NCP13992_技术文档

NCP13992

High Performance Current

Mode Resonant Controller

with Integrated High-

Voltage Drivers

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The NCP13992 is a high performance current mode controller for

half bridge resonant converters. This controller implements 600 V

gate drivers, simplifying layout and reducing external component

count. The built−in Brown−Out input function eases implementation

of the controller in all applications. In applications where a PFC front

stage is needed, the NCP13992 features a dedicated output to drive the

PFC controller. This feature together with quiet skip mode technique

further improves light load efficiency of the whole application. The

NCP13992 provides a suite of protection features allowing safe

operation in any application. This includes: overload protection,

over−current protection to prevent hard switching cycles, brown−out

detection, open optocoupler detection, automatic dead−time adjust,

over−voltage (OVP) and over−temperature (OTP) protections.

16

1

SOIC−16 NB

(LESS PINS 2 AND 13)

D SUFFIX

CASE 751DU

MARKING DIAGRAM

16

NCP13992xy

AWLYWWG

Features

• High−Frequency Operation from 20 kHz up to 750 kHz

• Current Mode Control Scheme

1

NCP13992 = Specific Device Code

• Automatic Dead−time with Maximum Dead−time Clamp

• Dedicated Startup Sequence for Fast Resonant Tank Stabilization

• Light Load Operation Mode for Improved Efficiency

• Quiet Skip Operation Mode for Minimize Transformer Acoustic Noise

• Latched or Auto−Recovery Overload Protection

• Latched or Auto−Recovery Output Short Circuit Protection

• Latched Input for Severe Fault Conditions, e.g. OVP or OTP

• Out of Resonance Switching Protection

x

y

A

WL

Y

= A

= Assembly Location

= Wafer Lot

= Year

= Work Week

= Pb−Free Package

WW

G

PIN CONNECTIONS

• Open Feedback Loop Protection

1

HV

16 VBOOT

15 HB

• Precise Brown−out Protection

• PFC Stage Operation Control According to Load Conditions

• Startup Current Source with Extremely Low Leakage Current

• Dynamic Self−Supply (DSS) Operation in Off−mode or Fault Modes

• Pin to Adjacent Pin / Open Pin Fail Safe

14

3

4

5

6

VBULK/PFCFB

SKIP

MUPPER

LLCFB

12 MLOWER

11

LLCCS

GND

10 VCC

PFCMODE

• These are Pb−Free Devices

OVP/OTP

FBFREEZE

7

8

Typical Applications

9

• Adapters and Offline Battery Chargers

• Flat Panel Display Power Converters

• Computing Power Supplies

(Top View)

ORDERING INFORMATION

See detailed ordering and shipping information on page 8 of

• Industrial and Medical Power Sources

this data sheet.

1

Publication Order Number:

January, 2018 − Rev. 0

NCP13992/D

NCP13992

Figure 1. Typical Application Example without PFC Stage − WLLC Design

Figure 2. Typical Application Example with PFC Stage

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2

NCP13992

PIN FUNCTION DESCRIPTION

Pin No.

Pin Name

Function

Pin Description

1

HV

High−voltage startup

current source input

Connects to rectified AC line or to bulk capacitor to perform functions of Start−

up Current Source and Dynamic Self−Supply

2

3

NC

Not connected

Increases the creepage distance

VBULK /

PFC FB

Bulk voltage monitoring input Receives divided bulk voltage to perform Brown−out protection.

4

5

SKIP

Skip threshold adjust

LLC feedback input

Sets the skip in threshold via a resistor connected to ground

LLC FB

Defines operating frequency based on given load conditions. Activates skip

mode operation under light load conditions.

6

LLC CS

LLC current sense input

Senses divided resonant capacitor voltage to perform on−time modulation, out

of resonant switching protection, over−current protection and secondary side

short circuit protection.

7

8

9

OTP / OVP

FB FREEZE

PFC MODE

Over−temperature and

over−voltage protection input

Implements over−temperature and over−voltage protection on single pin.

Minimum internal FB level

Adjusts minimum internal FB level that can be reached during light load oper-

ation.

PFC and external HV

switch control output

Provides supply voltage for PFC front stage controller and/or enables Vbulk

sensing network HV switch.

10

11

VCC

GND

Supplies the controller

Analog ground

The controller accepts up to 20 V on VCC pin

Common ground connection for adjust components, sensing networks and

DRV outputs.

12

13

14

15

16

MLOWER

NC

Low side driver output

Not connected

Drives the lower side MOSFET

Increases the creepage distance

Drives the higher side MOSFET

Connects to the half−bridge output.

The floating VCC supply for the upper stage

MUPPER

HB

High side driver output

Half−bridge connection

Bootstrap pin

VBOOT

Figure 3. Internal Circuit Architecture

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3

NCP13992

MAXIMUM RATINGS

Rating

Symbol

Value

−0.3 to 600

−0.3 to 5.5

Unit

V

HV Startup Current Source HV Pin Voltage (Pin 1)

VBULK/PFC FB Pin Voltage (Pin3)

SKIP Pin Voltage (Pin 4)

V

HV

BULK/PFC FB

V

SKIP

−0.3 to 5.5

V

LLC FB Pin Voltage (Pin 5)

V

−0.3 to 5.5

V

FB

CS

LLC CS Pin Voltage (Pin 6)

V

−5 to 5

V

PFC MODE Pin Output Voltage (Pin 9)

VCC Pin Voltage (Pin 10)

V

−0.3 to VCC+0.3

−0.3 to 20

V

PFC MODE

V

CC

DRV_MLOWER

Low Side Driver Output Voltage (Pin 12)

High Side Driver Output Voltage (Pin 14)

High Side Offset Voltage (Pin 15)

High Side Floating Supply Voltage (Pin 16)

High Side Floating Supply Voltage (Pin 15 and 16)

Allowable Output Slew Rate on HB Pin (Pin 15)

OVP/OTP Pin Voltage (Pin 7)

V

−0.3 to VCC + 0.3

V

– 0.3 to V

BOOT

+ 0.3

+0.3

V

DRV_MUPPER

HB

V

HB

V

−20 to V

Boot

V

Boot

V

BOOT

−0.3 to 620

−0.3 to 20.0

50

V

Boot–VHB

dV/dt

V/ns

V

max

V

−0.3 to 5.5

−50 to 150

−55 to 150

130

OVP/OTP

P ON/OFF

FB FREEZE Pin Voltage (Pin 8)

Junction Temperature

V

T

J

°C

°C/W

kV

Storage Temperature

T

STG

Thermal Resistance Junction−to−air

R

θ

JA

Human Body Model ESD Capability per JEDEC JESD22−A114F

(except HV Pin – Pin 1)

−

4.5

Machine Model ESD Capability per JEDEC JESD22−A115C

−

250

1

V

Charged−Device Model ESD Capability per JEDEC JESD22−C101E

kV

Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality

should not be assumed, damage may occur and reliability may be affected.

Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond

the Recommended Operating Ranges limits may affect device reliability.

1. This device contains latch−up protection and exceeds 100 mA per JEDEC Standard JESD78

ELECTRICAL CHARACTERISTICS

(For typical values Tj = 25°C, for min/max values Tj = −40°C to +125°C, Vcc = 12 V unless otherwise noted)

Symbol

Rating

Min

Typ

Max

Unit

HV STARTUP CURRENT SOURCE

V

Minimum voltage for current source operation

(V = V −0.5 V, I drops to 95%)

1

−

60

V

HV_MIN1

CC

CC_ON

START2

V

Minimum voltage for current source operation

(V = V −0.5 V, I drops to 5 mA)

HV_MIN2

CC

CC_ON

START2

I

Current flowing out of V pin (V = 0 V)

1, 10

1

0.2

6

0.5

9

0.8

13

10

mA

START1

CC

Current flowing out of V pin (V = V −0.5 V)

CC_ON

START2

CC

I

Off−state leakage current (V = 500 V, V = 15 V)

−

START_OFF

HV

CC

SUPPLY SECTION

V

Turn−on threshold level, V going up

10

15.3

9.0

15.8

9.5

16.3

10

V

CC_ON

CC

V

Minimum operating voltage after turn−on

CC_OFF

V

level at which the internal logic gets reset

10

5.8

6.6

7.2

V

CC_RESET

CC_INHIBIT

CC

V

level for I

to I

transition

10

0.40

500

0.80

780

1.25

950

V

START1

START2

I

Controller supply current in skip−mode, V = 15 V,

10, 11

mA

CC_SKIP−MODE

CC

OVP/OTP block debiased during skip mode

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4

NCP13992

ELECTRICAL CHARACTERISTICS

(For typical values Tj = 25°C, for min/max values Tj = −40°C to +125°C, Vcc = 12 V unless otherwise noted)

Symbol

Rating

Min

Typ

Max

Unit

SUPPLY SECTION

I

Controller supply current in latch−off mode,

10, 11

350

400

4.0

570

580

5.4

700

7.0

mA

CC_LATCH

V

CC

= V

− 0.2 V

CC_ON

I

Controller supply current in auto−recovery mode,

= V − 0.2 V

CC_AUTOREC

V

CC

CC_ON

I

Controller supply current in normal operation,

= 100 kHz, C = 1 nF, V = 15 V

mA

CC_OPERATION

f

sw

load

CC

BOOTSTRAP SECTION

V

Startup voltage on the floating section (Note 3)

Cutoff voltage on the floating section

16, 15

7.5

7.0

30

9.0

8.2

75

10.0

9.1

V

BOOT_ON

V

BOOT_OFF

I

Upper driver consumption, no DRV pulses

130

2.00

mA

BOOT1

Upper driver consumption, C

= 1 nF between Pins 13 &

1.30

1.65

BOOT2

load

15 f = 100 kHz, HB connected to GND

sw

HB DISCHARGER

I

HB sink current capability V = 30 V

15

7

1

−

9.6

4.1

−

12

8

mA

V

DISCHARGE1

DISCHARGE2

HB

HB sink current capability V = V

HB

HB_MIN

V

HB voltage @ I

changes from 2 to 0 mA

10

HB_MIN

DISCHARGE

DRIVER OUTPUTS

t

Output voltage rise−time @ C = 1 nF, 10−90% of output

signal

12, 14

20

5

45

30

80

50

ns

r

L

t

Output voltage fall−time @ C = 1 nF, 10−90% of output

f

L

signal

R

Source resistance

Sink resistance

12, 14

4

1

−

16

5

32

11

−

W

A

OH

R

OL

DRVSOURCE

I

Output high short circuit pulsed current

0.5

V

DRV

= 0 V, PW v 10 ms

I

Output high short circuit pulsed current

= VCC, PW v 10 ms

12, 14

−

1

−

5

A

DRVSINK

V

DRV

I

Leakage current on high voltage pins to GND

14, 15, 16

mA

HV_LEAK

DEAD−TIME GENERATION

t

Maximum Dead−time value if no dV/dt falling/rising edge is

received

12, 14

720

−

800

8

880

−

ns

−

DEAD_TIME_MAX

N

Number of DT_MAX events to enters IC into fault

12, 14, 16

DT_MAX

dV/dt DETECTOR

P

Positive slew rate on V

sensor triggered, VHB rising from 0 to 100 V linearly (Note 2)

pin above which is dV/dt_P

16

−

178

226

200

250

V/ms

dV/dt_th_1

BOOT

P

Positive slew rate on V pin above which is dV/dt_P

dV/dt_th_2

BOOT

sensor triggered, VHB rising from 100 to 200 V linearly

(Note 2)

P

Positive slew rate on V

sensor triggered, VHB rising from 200 to 400 V linearly

(Note 2)

pin above which is dV/dt_P

16

−

246

280

V/ms

dV/dt_th_3

BOOT

N

Negative slew rate on V

sensor triggered, VHB falling from 100 to 0 V linearly

pin above which is dV/dt_N

16

−

163

290

250

−

V/ms

dV/dt_th_1

dV/dt_th_2

dV/dt_th_3

BOOT

Negative slew rate on V pin above which is dV/dt_N

BOOT

sensor triggered, VHB falling from 200 to 100 V linearly

Negative slew rate on V pin above which is dV/dt_N

BOOT

sensor triggered, VHB falling from 400 to 200 V linearly

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5

NCP13992

ELECTRICAL CHARACTERISTICS

(For typical values Tj = 25°C, for min/max values Tj = −40°C to +125°C, Vcc = 12 V unless otherwise noted)

Symbol

Rating

Min

Typ

Max

Unit

PFC MODE OUTPUT AND P ON/OFF ADJUST

V

PFC MODE output voltage when application enters skip

mode (inject 1 mA into the PFC MODE output)

9

−

6.00

−

0.1

6.25

−

V

PFC_M_OFF

V

PFC MODE output voltage when V < V

P ON/OFF

5.75

PFC_M_BO

PFC_M_ON

PFC_M_LIM

FB

(sink 1 mA current from PFC MODE output)

V

PFC MODE output voltage when V > V

V

−

V

FB

P ON/OFF

CC

0.4

(sink 20 mA current from PFC MODE output)

I

PFC MODE output current limit (V

< 2 V)

0.7

1.2

1.85

mA

PFC MODE

OVP/OTP

V

OVP threshold voltage (V

OTP threshold voltage (V

going up)

7

2.35

0.76

90

2.50

0.80

95

2.65

0.84

100

V

OVP

OTP

OVP/OTP

going down)

OVP/OTP

I

OTP/OVP pin source current for external NTC – during

normal operation

mA

I

OTP/OVP pin source current for external NTC – during

startup

7

180

190

200

mA

OTP_BOOST

t

Internal filter for OVP comparator

Internal filter for OTP comparator

Blanking time for OTP input during startup

7

32

200

14

37

330

16

44

500

18

ms

V

OVP_FILTER

t

OTP_FILTER

t

BLANK_OTP

V

OVP/OTP pin clamping voltage @ I

= 0 mA

= 1 mA

1.0

1.8

1.2

2.4

1.4

3.0

CLAMP_OVP/OTP_1

CLAMP_OVP/OTP_2

OVP/OTP

V

START−UP SEQUENCE PARAMETERS

Initial Mlower DRV on−time duration

t

12

4.7

0.72

17

4.9

0.79

20

5.4

0.88

22

ms

ns

−

1st_MLOWER_TON

t

Initial Mupper DRV on−time duration

On−time period increment during soft−start

Soft−Start increment division ratio

14

1st_MUPPER_TON

t

12, 14

SS_INCREMENT

K

−

4

−

SS_INCREMENT

t

Time duration to restart IC if start−up phase is not finished

0.45

0.50

0.55

ms

WATCHDOG

FEEDBACK SECTION

R

Internal pull−up resistor on FB pin

5

15

18

25

kW

−

FB

K

V

FB

to internal current set point division ratio

1.92

4.60

4.4

2.00

4.95

4.6

2.08

5.30

4.8

V

Internal voltage reference on the FB pin

V

FB_REF

V

Internal clamp on FB input of On−time comparator referred

to external FB pin voltage

V

FB_CLAMP

V

Skip comparator hysteresis

5

148

0.468

0.595

0.95

174

0.508

0.635

1.05

222

0.548

0.675

1.15

mV

V

FB_SKIP_HYST

V

Feedback voltage thresholds to enter Light load mode

Feedback voltage thresholds to exit Light load mode

FB_LL_IN

V

5

V

FB_LL_OUT

1st_MLOWER_SKIP

st

t

On−time duration of 1 Mlower pulse when FB cross

5, 12

ms

V

+ V

threshold

FB_SKIP_IN

FB_SKIP_HYST

st

V

Internal FB level reduction during 1 Mupper pulse when

5, 6, 14

−

150

−

mV

1st_MUPPER_SKIP

FB cross V

+ V

threshold (Note 2)

FB_SKIP_IN

FB_SKIP_HYST

SKIP INPUT

I

Internal Skip pin current source

4

48

−

50

−

52

10

mA

SKIP

SKIP_LOAD_MAX

C

Maximum loading capacitance for skip pin voltage filtering

(Note 2)

nF

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6

NCP13992

ELECTRICAL CHARACTERISTICS

(For typical values Tj = 25°C, for min/max values Tj = −40°C to +125°C, Vcc = 12 V unless otherwise noted)

Symbol

Rating

Min

Typ

Max

Unit

QUIET−SKIP PARAMETERS

t

The portion of previous MU on−time that is place for last ML

pulse in pattern

12

−

50

5

−

%

LAST_ML_PATTERN

t

The portion of previous MU on−time that is place for last ML

pulse before the LL or skip mode is activated

12

LAST_ML_SKIP

t

Skip burst off−time duration that is needed to increase num-

ber of skipped valleys between following patterns

12, 14

−

ms

GEAR_UP

t

Skip burst on−time duration that is needed to decrease

number of skipped valleys between following patterns

−

15

5

−

GEAR_DOWN

t

Time duration to force valley count logic if valley is not de-

tected

4.5

5.5

VALLEY_WD

t

Quiet Timer duration

12, 14

−

5

2

−

ms

−

QS_timer

N

Number of patterns adjustment when bust period is shorter

than ¼ of QS_timer duration

QS_1/4

QS_2/4

QS_3/4

QS_4/4

QS_INF

Number of patterns adjustment when bust period is longer

than ¼ and shorter than 2/4 of QS_timer duration

12, 14

14

−

1

0

−

Number of patterns adjustment when bust period is longer

than 2/4 and shorter than 3/4 of QS_timer duration

Number of patterns adjustment when bust period is longer

than 3/4 and shorter than 4/4 of QS_timer duration

0

N

Number of patterns adjustment when bust period is longer

than QS_timer duration

−1

1

N

Initial number of patterns placed when LL or skip mode is

activated

PATTERN_INIT

N

Number of MU pulses during which FB_LL_IN cmp is

blanked once VFB > VFB_LL_OUT

60

LL_blank

FB FREEZE INPUT

I

FB Freeze pin current source

4

18

−

20

−

22

10

mA

FB_Freeze

FB_Freeze_LOAD_MAX

C

Maximum loading capacitance for FB Freeze pin voltage

filtering (Note 2)

nF

CURRENT SENSE INPUT SECTION

On−time comparator delay to Mupper driver turn off

t

5, 6

−

250

ns

pd_CS

V

FB

= 2.5 V, V goes up from –2.5 V to 2.5 V with rising

CS

edge of 100 ns

I

Current sense input leakage current for V

=

CS

3 V

6

−

1

mA

mV

ns

CS_LEAKAGE

V

Current sense input offset voltage

160

360

200

440

240

540

CS_OFFSET

t

Leading edge blanking time of the on−time comparator

output

5, 6, 14

LEB

LFFGAIN

Line Feed Forward current source transconductance

3, 6

−

0

−

mA/V

(V

> V )

BO

VBULK/PFC_FB

FAULTS AND AUTO−RECOVERY TIMER

t

Maximum on−time clamp

12, 14

7.3

−

7.7

1

8.4

−

ms

−

TON_MAX

TON_MAX_COUNTER

N

Number of TON_MAX events to confirm fault

FB fault timer duration

12,14

t

−

5

−

6

160

4.5

−

200

4.7

5

240

4.9

−

ms

V

FB_FAULT_TIMER

V

FB voltage when FB fault is detected

Number of CS_fault cmp. pulses to confirm CS fault

CS voltage when CS fault is detected (NCP13992xA)

FB_FAULT

CS_FAULT_COUNTER

N

−

V

2.5

2.7

2.9

V

CS_FAULT

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7

NCP13992

ELECTRICAL CHARACTERISTICS

(For typical values Tj = 25°C, for min/max values Tj = −40°C to +125°C, Vcc = 12 V unless otherwise noted)

Symbol

Rating

Min

Typ

Max

Unit

FAULTS AND AUTO−RECOVERY TIMER

t

Auto−recovery duration (common timer for all fault condition)

−

0.8

1

1.2

s

A−REC_TIMER

BROWN−OUT PROTECTION

V

Brown−out turn−off threshold

3

0.965

4.1

5

1.000

5.0

12

1.035

5.7

V

BO

I

Brown−out hysteresis current, V

< V

mA

mV

mA

ms

BO

VBULK/PFC_FB

BO

V

Brown−Out comparator hysteresis

Brown−Out input bias current

BO filter duration

25

BO_HYST

BO_BIAS

I

−

0.05

30

t

10

20

BO_FILTR

RAMP COMPENSATION

RC

Ramp compensation gain

−

58

−

82

108

−

mV/ms

ms

GAIN

RC_SHIFT

t

Ramp compensation time shift

0.4

TEMPERATURE SHUTDOWN PROTECTION

T

Temperature shutdown T going up

−

124

30

−

°C

TSD

TSD_HYST

J

T

Temperature shutdown hysteresis

Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product

performance may not be indicated by the Electrical Characteristics if operated under different conditions.

2. Guaranteed by design.

3. Minimal resistance connected in series with bootstrap diode is 3.3 W

IC OPTIONS

Cumulative

FB fault

source

OVP/OTP bias

during skip

FB fault timer/

counter

Option

FB fault

CS_FAULT

TON_MAX

OVP

OTP

NCP13992AA Auto−recovery

Timer

NO

Auto−recovery Auto−recovery Latch Auto−recovery

ON

Dedicated

Soft_start_-

seq

PFC_MODE

skip status

Option

Dead time

control

Ramp comp

status

Skip mode

Dead time fault BO status

Active OFF ON

NCP13992AA

ON

Quiet Skip

Auto−recovery

Without ramp

shift

ON

ORDERING INFORMATION

Device

†

Package Marking

Package

SOIC−16, Less Pin 2 and 13 (Pb−free)

Shipping

NCP13992AADR2G

NCP13992AA

2500 / Tape & Reel

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

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8

NCP13992

VCC Management with High−voltage Startup Current

Source

The NCP13992 controller features a HV startup current

source that allows fast startup time and extremely low

standby power consumption. Two startup current levels

over−temperature protection to prevent IC damage for any

failure mode that may occur in the application. The HV

startup current source is primarily enabled or disabled based

on V level. The startup HV current source can be also

CC

enabled by BO_OK rising edge, auto−recovery timer end

and TSD end event. The HV startup current source charges

the VCC capacitor before IC start−up.

(I

and I

) are provided by the system for safety in

start1

start2

case of short circuit between VCC and GND pins. In

addition, the HV startup current source features a dedicated

Figure 4. Internal Connection of the VCC Management Block

The NCP13992 controller disables the HV startup current

when the die temperature reaches 130°C. At this

temperature, I will be progressively to prevent the die

source once the VCC pin voltage level reaches V

CC_ON

start2

threshold – refer to Figure 4. The application then starts

operation and the auxiliary winding maintains the voltage

bias for the controller during normal and skip−mode

operating modes. The IC operates in so called Dynamic Self

Supply (DSS) mode when the bias from auxiliary winding

temperature from rising above 130°C.

Brown−out Protection − VBULK/PFC FB Input

Resonant tank of an LLC converter is always designed to

operate within a specific bulk voltage range. Operation

below minimum bulk voltage level would result in current

and temperature overstress of the converter power stage.

The NCP13992 controller features a VBULK/PFC FB input

in order to precisely adjust the bulk voltage turn−ON and

turn−OFF levels. This Brown−Out protection (BO) greatly

simplifies application level design.

is not sufficient to keep the V voltage above V

CC

CC_OFF

threshold (i.e. V voltage is cycling between V

and

CC

CC_ON

V

thresholds with no driver pulses on the output

CC_OFF

during positive V ramp). Please refer to Figure 23 through

CC

Figure 25 to find an illustration of the NCP13992 VCC

management system under all operating conditions/modes.

The HV startup current source features an independent

over–temperature protection system to limit I

current

start2

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9

NCP13992

Figure 5. Internal Connection of the Brown−out Protection Block

The internal circuitry shown in Figure 5 allows

V_{bulk_OFF}* V_BO

R_upper+ R_lower

@

(eq. 4)

monitoring the high−voltage input rail (V ).

A

bulk

V_BO

high−impedance resistive divider made of R

and R

upper

lower

Note that the VBULK/PFC FB pin is pulled down by an

internal switch when the controller is in startup phase − i.e.

when the V voltage ramps up from V < V

resistors brings a portion of the V

rail to the

bulk

VBULK/PFC FB pin. The Current sink (I ) is active below

BO

CC

CC_RESET

the bulk voltage turn−on level (V

). Therefore, the

bulk_ON

towards the V

level on the VCC pin. This feature

CC_ON

bulk voltage turn−on level is higher than defined by the

division ratio of the resistive divider. To the contrary, when

the internal BO_OK signal is high, i.e. the application is

assures that the VBULK/PFC FB pin voltage will not ramp

up before the IC operation starts. The I hysteresis current

sink is activated and BO discharge switch is disabled once

BO

running, the I sink is disabled. The bulk voltage turn−off

BO

the

V

CC

voltage crosses

V

CC_ON

threshold. The

threshold (V ) is then given by BO comparator

bulk_OFF

VBULK/PFC FB pin voltage then ramps up naturally

according to the BO divider information. The BO

comparator then authorizes or disables the LLC stage

reference voltage directly on the resistor divider. The

advantage of this solution is that the V threshold

bulk_OFF

precision is not affected by I

tolerance.

hysteresis current sink

BO

operation based on the actual V

level.

bulk

The low I hysteresis current of the NCP13992 brown

BO

The V

and V

levels can be calculated

bulk_ON

bulk_OFF

out protection system allows increasing the bulk voltage

divider resistance and thus reduces the application power

consumption during light load operation. On the other hand,

the high impedance divider can be noise sensitive due to

capacitive coupling to HV switching traces in the

using equations below:

The I is ON:

BO

(eq. 1)

V_BO) V_BOhyst

+

R_lower

R_lower) R_upper

R_lower@ R_upper

R_lower) R_upper

_@ǒ

Ǔ

V_{bulk_ON}

@

* I_BO

application. This is why a filter (t

) is added after the

BO_FILTR

BO comparator in order to increase the system noise

immunity. Despite the internal filtering, it is also

recommended to keep a good layout for BO divider resistors

and use a small external filtering capacitor on the

VBULK/PFC pin if precise BO detection wants to be

achieved.

The bulk voltage HV divider can be also used by a PFC

front stage controller as a feedback sensing network (refer

again to Figure 5). The shared bulk voltage resistor divider

between PFC and LLC stage offers a way how to further

reduce power losses during no−load operation. The

NCP13992 features a PFC MODE pin that disconnects bias

The I is OFF:

BO

R_lower

R_lower) R_upper

V_BO+ V_{bulk_OFF}

@

(eq. 2)

One can extract R

term from equation 2 and use it in

lower

equation 1 to get needed R

value:

upper

V_{bulk_ON}@V

^BO* V_BO* V_BOhyst

V_{bulk_OFF}

R_lower

+

(eq. 3)

V_BO

I_BO

@

ǒ

1 *

Ǔ

V_{bulk_OFF}

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10

NCP13992

of the PFC stage during light load or fault mode operation.

The controller is allowed to run when OVP/OTP input

voltage is within this working window. The controller stops

the operation, after filter time delay, when the OVP/OTP

input voltage is out of the no−fault window. The controller

then either latches−off or or starts an auto−recovery timer −

depending on the IC version − and triggered the protection

This technique further reduces the no−load power

consumption down again since the power losses of voltage

divider are not affected by the bulk voltage at all.

Please refer to Figure 23 through Figure 25 for an

illustration of NCP13992 Brown−out protection system in

all operating conditions/modes.

threshold (V

or V ).

OVP

OTP

The VBULK/PFC FB pin voltage is also used by Line

Feed Forward block (LFF). Please refer to ON−time

modulation and feedback loop block description for more

information about LFF function.

The internal current source I

implementation by using a single negative temperature

coefficient (NTC) thermistor. An active soft clamp

allows a simple OTP

OTP

composed from V

and R

components prevents the

clamp

OVP/OTP pin voltage from reaching the V

threshold

OVP

Over−voltage and Over−temperature Protection

when the pin is pulled up by the I

current. An external

OTP

The OVP/OTP pin is a dedicated input to allow for a

simple and cost effective implementation of two key

protection features that are needed in adapter applications:

over−voltage (OVP) and over−temperature (OTP)

protections. Both of these protections can be either latched

or auto−recovery– depending on the version of NCP13992.

The OVP/OTP pin has two voltage threshold levels of

pull*up current, higher than the pull*down capability of

the internal clamp (V

pull the OVP/OTP pin above V

), has to be applied to

threshold to activate the

CLAMP_OVP/OTP

OVP

OVP protection. The t

and t

filters

OVP_FILTER

OTP_FILTER

are implemented in the system to avoid any false triggering

of the protections due to application noise and/or poor

layout.

detection (V

and V ) that define a no−fault window.

OTP

OVP

Figure 6. Internal Connection of OVP/OTP Input

The OTP protection could be falsely triggered during

controller startup due to the external filtering capacitor

• V falls below V

threshold

CC

CC_OFF

• BO OK signal goes to low state (i.e. Brown−out

charging current. Thus the t

period has been

BLANK_OTP

condition occurs on the mains)

implemented in the system to overcome such behavior. The

OTP comparator output is ignored during t

• Fault signal is activated (Auto−recovery timer starts

counting or Latch fault is present)

BLANK_OTP

period. In order to speed up the charging of the external

filtering capacitor C connected to OVP/OTP pin,

• IC goes into the skip−mode operation (V

FB_SKIP_IN

OVP_OTP

threshold was reached)

the I

current has been doubled to I . The

OTP_BOOST

OTP

maximum value of filtering capacitor is 100 nF.

The OVP/OTP ON signal is set after the following events:

• the V voltage exceeds the V threshold during

IC option that keeps OVP/OTP block working during skip

mode is also available. The IC consumption is increased for

this version by OVP/OTP block bias.

CC

CC_ON

The latched OVP or OTP versions of NCP13992 enters

first start−up phase (after VCC pin voltage was below

threshold)

latched protection mode when V voltage cycles between

CC

V

CC_RESET

V

CC_ON

and V

thresholds and no pulses are provided

CC_OFF

• BO OK signal is received from BO block

by drivers. The controller VCC pin voltage has to be cycled

down below V threshold in order to restart

• Auto−recovery timer elapsed and a new restart occurs

CC_RESET

• IC returns to operation from skip−mode (V

+

operation. This would happen when the power supply is

unplugged from the mains.

FB_SKIP_IN

V

threshold was reached)

FB_SKIP_HYST

The I

current source is disabled when:

OTP

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11

NCP13992

st

PFC MODE Output

1 to control the external small signal HV MOSFET switch

that connects the bulk voltage divider to the VBULK/PFC

FB input

The NCP13992 has PFC MODE pin that can be used to

disable or enable PFC stage operation based on actual

application operating state – please refer to Figure 7. The

PFC MODE output pin can be used for two purposes:

nd

2

to control the PFC front stage controller operation via

PFC controller supply pin

Figure 7. Internal Connection of the PFC MODE Block

ON−time Modulation and Feedback Loop Block

There are two possible states of the PFC MODE output

that can be placed by the controller based on the application

operating conditions:

Frequency modulation of today’s commercially available

resonant mode controllers is based on the output voltage

regulator feedback only. The feedback voltage (or current)

of output regulator drives voltage (or current) controlled

oscillator (VCO or CCO) in the controller. This method

presents three main disadvantages:

a) The PFC MODE output pin is pulled−down by an internal

MOSFET switch before controller startup. This technique

ensures minimum VCC pin current consumption in order to

ramp V voltage in a short time from the HV startup

CC

st

nd

1

− The 2 order pole is present in small signal gain−phase

current source. This approach speeds up the startup and

restart time of an SMPS. The PFC MODE output pin is also

pulled−down in protection mode during which the HV

startup current source is operated in DSS mode. Application

power consumption is reduced in both above cases.

characteristics => the lower cross over frequency and worse

transient response is imposed by the system when voltage

mode control is used. There is no direct link to the actual

primary current – i.e. no line feed forward mechanism which

results in poor line transient response.

b) The pull−down switch is disabled and controller connects

VCC pin voltage to PFC MODE output with minimum

nd

2

– Precise VCO (or CCO) is needed to assure frequency

clamps

modulation with good reproducibility, f and f

dropout (V

).

min

max

PFC_M_ON

need to be adjusted for each design => need for an

adjustment pin(s).

The PFC MODE pin output current is limited when the

VCC to PFC MODE bypass switch is activated. The current

limitation avoids bypass switch damage during PFC VCC

decoupling capacitor charging process or short circuit. A

minimum value PFC VCC decoupling capacitance should

be used in order to speed up PFC stage startup after it is

enabled by the NCP13992 controller.

rd

3

– Dedicated overload protection system, requiring an

additional pin, is needed to assure application safety during

overload and/or secondary short circuit events.

The NCP13992 resolves all disadvantages mentioned

above by implementing a current mode control scheme that

ensures best transient response performance and provides

inherent cycle−by−cycle over−current protection feature in

the same time. The current mode control principle used in

this device can be seen in Figure 8.

Please refer to Figure 23 through Figure 25 for an

illustration of NCP13992 PFC operation control.

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12

NCP13992

Figure 8. Internal Connection of the NCP13992 Current Mode Control Scheme

The basic principle of current mode control scheme

detection – please refer to chapter dedicated to short circuit

implementation lies in the use of an ON−time comparator

that defines upper switch on−time by comparing voltage

ramp, derived from the current sense input voltage, to the

divided feedback pin voltage. The upper switch on−time is

then re−used for low side switch conduction period. The

switching frequency is thus defined by the actual primary

current and output load conditions. Digital processing with

10 ns minimum on−time resolution is implemented to

ensure high noise immunity. The ON−time comparator

protection.

The second input signal for the on−time comparator is

derived from the FB pin voltage. This internal FB pin signal

is also used for the following purposes: skip mode operation

detection, PFC MODE control and overload / open FB pin

fault detection. The detailed description of these functions

can be found in each dedicated chapters. The internal

pull−up resistor assures that the FB pin voltage increases

when the optocoupler LED becomes less biased – i.e. when

output load is increased. The higher FB pin voltage implies

a higher reference level for on−time comparator i.e. longer

Mupper switch on−time and thus also higher output power.

The FB pin features a precise voltage clamp which limits the

internal FB signal during overload and startup. The FB pin

signal passes through the FB processing block before it is

brought to the ON−time comparator input. The FB

output is blanked by the leading edge blanking (t

) after

LEB

the Mupper switch is turned−on. The ON−time comparator

LEB period helps to avoid false triggering of the on−time

modulation due to noise generated by the HB pin voltage

transition.

The voltage signal for current sense input is prepared

externally via natural primary current integration by the

resonant tank capacitor Cs. The resonant capacitor voltage

is divided down by capacitive divider (Ccs1, Ccs2, Rcs1,

Rcs2) before it is provided to the CS input. The capacitive

divider division ratio, which is fully externally adjustable,

defines the maximum primary current level that is reached

in case of maximum feedback voltage – i.e. the capacitive

divider division ration defines the maximum output power

of the converter for given bulk voltage. The CS is a bipolar

input pin which an input voltage swing is restricted to 5 V.

A fixed voltage offset is internally added to the CS pin signal

in order to assure enough voltage margin for operation the

feedback optocoupler − the FB optocoupler saturation

voltage is ~ 0.15 V (depending on type). However, the CS

pin useful signal for frequency modulation swings from 0 V,

so current mode regulation would not work under light load

conditions if no offset would be added to the CS pin before

it is stabilized to the level of the on−time comparator input.

The CS pin signal is also used for secondary side short circuit

processing block scales the FB signal down by a K ratio

FB

in order to limit the CS input dynamic voltage range. The

scaled FB signal is then further processed by subtraction of

a ramp compensation generator signal in order to ensure

stability of the current mode control scheme. The divided

internal FB signal is overridden by a Soft−start generator

output voltage during device starts−up.

The actual operating frequency of the converter is defined

based on the CS pin and FB pin input signals. The maximum

output power of the converter, under given input voltage, is

limited by maximum internal FB voltage clamp that is

reached when optocoupler provides no current. The

maximum output power limit is bulk voltage dependent due

to changing ratio between magnetizing and load primary

current components. Line Feed Forward (LFF) system is

implemented in the controller to compensate for maximum

output power clamp variation. The I

out from the Cs pin is BO/PFC FB pin voltage proportional

current that flows

LFF

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13

NCP13992

and creates voltage offset on the resistor connected to the Cs

only when BO pin voltage exceeds BO_OK threshold

voltage.

Please refer to Figure 9 and below description for better

understanding of the NCP13992 frequency modulation

system.

pin. The higher input voltage, the higher drop is created on

external resistor. The Mupper switch on−time is thus

reduced for given maximum internal FB voltage clamp

when input voltage increases. The I

current is provided

LFF

Figure 9. NCP13992 On−time Modulation Principle

Overload and Open FB Protections

The Mupper switch is activated by the controller after

dead−time (DT) period lapses in point A. The frequency

processing block increments the ON−time counter with

10 ns resolution until the internal CS signal crosses the

internal FB set point for the ON−time comparator in point B.

A DT period is then introduced by the controller to avoid any

shoot−through current through the power stage switches.

The DT period ends in point C and the controller activates

the Mlower switch. The ON−time processing block

decrements the ON_time counter down until it reaches zero.

The Mlower switch is then turned−OFF at point D and the

DT period is started. This approach results in perfect duty

cycle symmetry for Mlower and Mupper switches. The

Mupper switch on−time naturally increases and the

operating frequency drops when the FB pin voltage is

increased, i.e. when higher current is delivered by the

converter output – sequence E.

The resonant capacitor voltage and thus also CS pin

voltage can be out of balance in some cases – this is the case

during transition from full load to no−load operation when

skip mode is not used or adjusted correctly. The current

mode operation is not possible in such case because the

ON−time comparator output stays active for several

switching cycles. Thus a special logic has been implemented

in NCP13992 in order to repeat the last valid on−time until

the current mode operation recovers – i.e. until the CS pin

signal balance is restored by the system.

The overload protection and open FB pin detection are

implemented via FB pin voltage monitoring in this

controller. The FB fault comparator is triggered once the FB

pin voltage reaches its maximum level and the V

FB_FAULT

threshold is exceeded. The fault timer or counter (depending

on IC option) is then enabled – refer to Figure 10. The time

period to the FB fault event confirmation is defined by the

preselected t

parameter when the fault

FB_FAULT_TIMER

timer option is used. The FB fault counter, once selected as

a FB fault confirmation period source, defines the fault

confirmation period via Mupper DRV pulses counting. The

FB fault confirmation time is thus dependent on switching

frequency. The fault timer/counter is reset once the FB fault

condition diminishes. A digital noise filter has been added

after the FB fault comparator to overcome false triggering of

the FB fault timer/counter due to possible noise on the FB

input. The noise filter has a period of 2 ms for FB fault

timer/counter activation and 20 µs for reset/deactivation to

assure high noise immunity. A cumulative timer/counter IC

option is also available on request. The FB fault

timer/counter is not reset when the FB fault condition

diminishes in this case. The FB fault timer/counter is

disabled and memorizes the fault period information. The

cumulative FB fault timer/counter integrates all the FB fault

events over the IC operation time. The Fault timer/counter

can be reset via skip mode or VCC UVLO event.

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14

NCP13992

Figure 10. Internal FB Fault Management

The controller disables driver pulses and enters protection

primary current is naturally limited by the NCP13992

on−time modulation principle in this case. But the primary

current increases when the output terminals are shorted. The

NCP13992 controller will maintain zero voltage switching

operation in such case, however high currents will flow

through the power MOSFETS, transformer winding and

secondary side rectification. The NCP13992 implements a

dedicated secondary side short circuit protection system that

will shut down the controller much faster than the regular FB

fault event in order to limit the stress of the power stage

components. The CS pin signal is monitored by the

dedicated CS fault comparator − refer to Figure 8. The CS

fault counter is incremented each time the CS fault

comparator is triggered. The controller enters

auto−recovery or latched protection mode (depending on IC

option) in case the CS fault counter overflows refer to

Figure 11. The CS fault counter is then reset once the CS

fault comparator is inactive for at least 50 Mupper upcoming

pulses. This digital filtering improves CS fault protection

system noise immunity.

mode once the FB fault event is confirmed by the FB fault

timer or counter. Latched or auto−recovery operation is then

triggered – depends on selected IC option. The controller

adds an auto−recovery off−time period (t ) and

A−REC_TIMER

restarts the operation via soft start in case of auto−recovery

option. The application temperature runaway is thus

avoided in case of overload while the automatic restart is still

possible once the overload condition disappears. The IC

with latched FB fault option stays latched−off, supplied by

the HV startup current source working in DSS mode, until

the V

threshold is reached on the VCC pin – i.e.

CC_RESET

until user re−connects power supply mains.

Please refer to Figure 23 and Figure 24 for an illustration

of the NCP13992 FB fault detection block.

Secondary Short Circuit Detection

The protection system described previously, implemented

via FB pin voltage level detection, prevents continuous

overload operation and/or open FB pin conditions. The

Figure 11. NCP13992 CS Fault Principle

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15

NCP13992

Dedicated Startup Sequence and Soft−Start

Hard switching conditions can occur in a resonant SMPS

application when the resonant tank operation is started with

50% duty cycle symmetry – refer to Figure 12. This hard

switching appears because the resonant tank initial

conditions are not optimal for the clean startup.

Figure 12. Hard Switching Cycle Appears in the LLC Application

when Resonant Tank is Excited by 50% Duty Cycle during Startup

The initial resonant capacitor voltage level can differ

These facts show that a clean, hard switching free and

parasitic oscillation free, startup of an LLC converter is not

an easy task, and cannot be achieved by duty cycle

imbalance and/or simple resonant capacitor pre−charge to

Vbulk/2 level. These methods only work in specific startup

conditions.

This explains why the NCP13992 implements a

proprietary startup sequence − see Figure 13 and Figure 14.

The resonant capacitor is discharged down to 0 V before any

application restart − except when restarting from skip mode.

depending on how long delay was placed before application

operation restart. The resonant capacitor voltage is close to

zero level when application restarts after very long delay –

for example several seconds, when the resonant capacitor is

discharged by leakage to the power stage. However, the

resonant capacitor voltage value can be anywhere between

Vbulk and 0 V when the application restarts operation after

a short period of time – like during periodical SMPS

turn−on/off. Another factor that plays significant role during

resonant power supply startup is the actual load impedance

seen by the power stage during the first pulses of startup

sequence. This impedance is not only defined by resonant

tank components but also by the output loading conditions

and actual output voltage level. The load impedance of

resonant tank is low when the output is loaded and/or the

output voltage is low enough to made secondary rectifies

conducting during first switching cycles of startup phase.

The resonant frequency of the resonant tank is given by the

resonant capacitor capacitance and resonant inductance

−note that the magnetizing inductance does not participate

in resonance in this case. However, if the application

starts−up when the output capacitors is charged and there is

no load connected to the output, the secondary rectification

diodes is not conducting during each switching cycle of

startup sequence and thus the resonant frequency of resonant

tank is affected also by the magnetizing inductance. In this

case, the resonant frequency is much lower than in case of

startup into loaded/discharged output.

Figure 13. Initial Resonant Capacitor Discharge

before Dedicated Startup Sequence is Placed

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16

NCP13992

Figure 14. Dedicated Startup Sequence Detail

The resonant capacitor discharging process is simply

The startup period then depends on the previous condition.

Another blank Mlower switch period is placed by the

controller in case condition a) occurred. A normal Mlower

driver pulse, with DC of 50% to previous Mupper DRV

pulse, is placed in case condition b) is fulfilled.

implemented by activating an internal current limited switch

connected between the HB pin and IC ground – refer to

Figure 13. This technique assures that the resonant capacitor

energy is dissipated in the controller without ringing or

oscillations that could swing the resonant capacitor voltage

to a positive or negative level. The controller detects that the

discharge process is complete via HB pin voltage level

monitoring. The discharge switch is disabled once the HB

The dedicated startup sequence is placed after the

resonant capacitor is discharged (refer to Figure 13 and

Figure 14) in order to exclude any hard switching cycles

during the startup sequence. The first Mupper switch cycle

in startup phase is always non−ZVS cycle because there is

no energy in the resonant tank to prepare ZVS condition.

However, there is no energy in the resonant tank at this time,

there is also no possibility that the power stage MOSFET

body diodes conducts any current. Thus the hard

commutation of the body diode cannot occur in this case.

The IC will not start and provide regular driver output

pulses until it is placed into the target application, because

the startup sequence cannot be finished until HB pin signal

is detected by the system. The IC features a startup watchdog

pin voltage drops below the V

threshold.

HB_MIN

The dedicated startup sequence continues by activation of

the Mlower driver output for Tl1 period (refer to Figure 14).

This technique ensures that the bootstrap capacitor is fully

charged before the first high−side driver pulse is introduced

by the controller. The first Mupper switch on−time Tup1

period is fixed and depends on the application parameters.

This period can be adjusted internally – various IC options

are available. The Mupper switch is released after T

up1

period and it is not followed by the Mlower switch

activation. The controller waits for a new ZVS condition for

Mupper switch instead and measures actual resonant tank

conditions this way. The Mupper switch is then activated

again after the Mlower blank period is used for measurement

purposes. The second Mupper driver conduction period is

then dependent on the previously measured conditions:

1. The Mupper switch is activated for 3/2 of previous

Mupper conduction period in case the measured

timer (t ) which activates a dedicated startup

WATCHDOG

sequence periodically in case the IC is powered without

application (during bench testing) or in case the startup

sequence is not finished correctly. The IC will provide the

first Mlower and first Mupper DRV pulses with a

t

off−time in−between startup attempts.

WATCHDOG

Soft−start

The dedicated startup sequence is complete when

condition b) from previous chapter is fulfilled and the

controller continues operation with the soft−start sequence.

A fully digital non−linear soft−start sequence has been

implemented in NCP13992 using a soft−start counter and

D/A converter that are gradually incremented by the Mlower

driver pulses. A block diagram of the NCP13992 soft−start

system is shown in Figure 15.

time between previous Mupper turn−off event and

upper ZVS condition detection is twice higher than

the the previous Mupper pulse conduction period

2. The Mupper switch is activated for previous

Mupper conduction period in case the measured

time between previous Mupper turn−off event and

upper ZVS condition detection is twice lower than

the previous Mupper pulse conduction period

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17

NCP13992

Figure 15. Soft−start Block Internal Implementation

The soft−start block subsystems and operation are

4. The Maximum ON−time comparator compares the

described below:

actual ON−time counter value with the maximum on−time

value (t

) and activates the latch (or auto−recovery)

TON_MAX

1. The Soft−Start counter is a unidirectional counter that is

loaded with the last Mupper on−time value that is reached at

the dedicated startup sequence end (i.e. during condition b

occurrence explained in previous chapter). The on−time

period used in the initial period of the soft−start sequence is

affected by the first Mupper on−time period selection and

the dedicated startup sequence processing. The Soft−Start

counter counts up from this initial on time period to its

maximum value which corresponds to the IC maximum

on−time. The Soft−Start counter is incremented by the

protection mode once IC detect requested number of

TON_MAX events. The minimum operating frequency of

the controller is defined the same way. The Maximum

ON−time comparator reference is loaded by the Soft−Start

counter value on each switching cycle during soft−start. The

Maximum ON−time fault signal is ignored during

Soft−Start operation. The converter Mupper switch on−time

(and thus operating frequency) is thus defined by the

Soft−Start counter value indirectly – via Maximum

ON−time comparator. The Mupper switch on−time is

soft−start increment number (t

) during each

SS_INCREMENT

increased until the Soft−Start counter reaches t

TON_MAX

Mlower switch on−time period. The soft−start start

increment, selectable via IC option, thus affects the

soft−start time duration. The Mlower clock signal for the

Soft−Start counter can be divided down by the SS clock

period and Maximum on−time protection is activated, or

until ON−time comparator takes action and overrides the

Maximum ON−time comparator.

divider (K

) in case the soft−start period needs

5. The Soft−Start D/A converter generates a soft−start

voltage ramp for ON−time comparator input synchronously

with Soft−Start counter incrementing. The internal FB

signal for ON−time comparator input is artificially

pulled−down and then ramped−up gradually when soft−start

period is placed by the system – refer to Figure 16. The FB

loop is supposed to take over at certain point when

regulation loop is closed and output gets regulated so that

soft−start has no other effect on the on−time modulation.

The Soft−Start counter continues counting−up until it

reaches its maximum value which corresponds to the IC

maximum on−time value – i.e. the IC minimum operating

frequency. The Soft−Start period is terminated (i.e. counter

is loaded to its maximum) when the FB pin voltage drops

SS_INCREMENT

to be prolonged further – this can be also done via IC option

selection. The Soft−Start period is terminated (i.e. the

counter is loaded to its maximum) when the FB pin voltage

drops below V

level.

FB_SKIP_IN

2. The ON−time counter is a bidirectional counter that is

used as a main system counter for on−time modulation

during soft−start, normal operation or overload conditions.

The ON−time counter counts−up during Mupper switch

conduction period and then counts down to zero – defining

Mlower switch conduction period. This technique assures

perfect 50% duty cycle symmetry for both power switches

as afore mentioned. The ON−time counter count−up mode

can be switched to the count−down mode by either of two

st

below V

level. The D/A converter output evolve

FB_SKIP_IN

events: 1 when the ON−time counter value reaches the

nd

accordingly to the Soft−Start counter as it is loaded from its

output data bus.

maximum on−time value (t

Mupper on−time is terminated based on the current sense

input information.

) or 2 when the actual

TON_MAX

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18

NCP13992

Figure 16. Soft Start Behavior

The Controller Operation during Soft−start Sequence

Evolves as Follows:

and saturates at its maximum possible value which

corresponds to IC minimum operating frequency. The

maximum on−time fault detection system is enabled when

The Soft−Start counter is loaded by last Mupper on−time

value at the end of the dedicated startup sequence. The

ON−time counter is released and starts count−up from zero

until the value that is equal to the actual Soft−Start counter

state. The Mupper switch is active during the time when

ON−time counter counts−up. The Maximum ON−time

comparator then changes counting mode of the ON−time

comparator from count−up to count−down. A dead−time is

placed and the Mlower switch is activated till the ON−time

counter reaches zero value. The Soft−Start counter is

incremented by selected increment during corresponding

Mlower on−time period so that the following Mupper switch

on−time is prolonged automatically – the frequency thus

drops naturally. Because the operating frequency of the

controller drops and Mlower DRV signal is used as a clock

source for the Soft−start counter, the soft−start speed starts

to decrease on each (or on each N−th) Mlower driver pulse

Soft−Start counter value is equal to t

value.

TON_MAX

The previous on−time repetition feature, described above

in the ON−time modulation and feedback loop chapter, is

disabled in the beginning of soft start period. This is because

the ON−time comparator output stays high for several cycles

of soft start period – until the current mode regulation takes

over. The previous on−time repetition feature is enabled

once the current modulation starts to work fully, i.e. in the

time when the ON−time comparator output periodically

drops to low state within actual Mupper switch on−time

period. Typical startup waveform of the LLC application

driven by NCP13992 controller can be seen in Figure 17.

(where N is defined by K ) of switching cycle.

SS_INCREMENT

So we have non−linear soft−start that helps to speed up

output charging in the beginning of the soft−start operation

and reduces the output voltage slope when the output is close

to the regulation level. The output bus of the Soft−Start

counter addresses the D/A converter that defines the

ON−time comparator reference voltage. This reference

voltage thus also increases non−linearly from initial zero

level until the level at which the current mode regulation

starts to work. The on−time of the Mupper and Mlower

switch is then defined by the ON−time comparator action

instead of the Maximum ON−time comparator. The

soft−start then continues until the regulation loop is closed

and the on−time is fully controlled by the secondary

regulator. The Soft−Start counter then continues in counting

Figure 17. Application Startup with NCP13992 −

Primary Current − Green, V_out− Magenta

www.onsemi.com

19

NCP13992

Skip Mode Operation

preselected level. Zero voltage switching technique is still

present for the power switches to achieve high light load

efficiency. Quiet skip mode operation is initiated when load

drops further and FB voltage drops below another FB

threshold that is user adjustable on the skip pin. The

frequency of skip burst is regulated by internal digital

controller around preselected quiet skip frequency clamp in

order to reduce acoustic noise. The skip frequency then

drops to very low values during no−load conditions. Refer

to Figure 18, Figure 19 and Figure 20 for typical application

waveforms during light load and quiet skip mode operating

modes.

Then NCP13992 implements proprietary light load and

quiet skip mode operating techniques that improve light load

efficiency, reduce no−load power consumption and

significantly reduce acoustic noise. Controller uses 50%

duty cycle symmetry under full and medium load

conditions. Normal current mode frequency modulation

takes place during this operating mode – refer to on−time

processing section of this datasheet. The 50% duty cycle

symmetry operating mode is replaced by continues

operation with minimum switching patterns repeated after

controlled amount of off−time when load is decreased below

Figure 18. No−load Operation

Figure 19. Quiet Skip Mode Operation

Figure 20. Light−load Operation

The High Voltage Half−bridge Driver

resistor Rboot value is 3.3 W. Figure 21 shows the internal

The driver features a traditional bootstrap circuitry,

requiring an external high voltage diode with resistor in

series for the capacitor refueling path. Minimum series

architecture of the drivers section. The device incorporates

an upper UVLO circuitry that makes sure enough V is

GS

available for the upper side MOSFET.

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20

NCP13992

HV

Vboot

Cboot

Internal Mupper

Pulse

Trigger

Level

Shifter

S

Mupper

Q

R

HB

dV/dt_P signal

dV/dt_N signal

dV/dt

detector

UVLO

Rboot

HB

discharger

HB disch. activation

Dboot

V

CC

aux

V

CC

Fault

Mlower

GND

Internal Mlower

Delay

+

Figure 21. The NCP13992 Internal DRVs Structure

The internal dV/dt sensor, connected to the VBOOT pin,

detects the HB pin voltage transitions in order to setup the

optimum DT period – please refer to Dead−Time chapter.

The internal HV discharge switch is connected to the HB pin

and discharges resonant capacitor before application

startup. The current through the switch is regulated to

I

level until the V

threshold voltage is

DISCHARGE

HB_MIN

reached on the HB pin. The discharge system assures always

the same startup conditions for application – regardless of

previous operating state.

As stated in the maximum ratings section, the floating

portion can go up to 620 VDC on the BOOT pin. This

voltage range makes the IC perfectly suitable for offline

applications featuring a 400 V PFC front stage.

Automatic Dead−time Adjust

The dead−time period between the Mupper and Mlower

drivers is always needed in half bridge topologies to prevent

any cross conduction through the power stage MOSFETs

that would result in excessive current, high EMI noise

generation or total destruction of the application. Fixed

dead−time period is often used in the resonant converters

because this approach is simple to implement. However, this

method does not ensure optimum operating conditions in

resonant topologies because the magnetizing current is

changing with line and load conditions. The optimum

dead−time, under a given operating conditions, is equal to

the time that is needed for bridge voltage to transition

between upper and lower states and vice versa – refer to

Figure 22.

Figure 22. Optimum Dead−time Period Adjust

The MOSFET body diode conduction time is minimized

when optimum dead−time period is used which results in

maximum efficiency of a resonant converter power stage.

There are several methods to determine the optimum

dead−time period or to approximate it (for example using

auxiliary winding on main transformer or modulating

dead−time period with operating frequency of the

converter). These approaches however require a dedicated

pin for nominal dead−time adjust or auxiliary winding

www.onsemi.com

21

NCP13992

voltage sensing. The NCP13992 uses a dedicated method

2. The controller is latched−off in case the ZSV

condition is not detected within selected

that senses the VBOOT pin voltage internally and adjusts the

optimum dead−time period with respect to the actual

operating conditions of the converter. The high−voltage

dV/dt detector, connected to the VBOOT pin, delivers two

internal digital signals that are indicating Mupper to Mlower

and Mlower to Mupper transitions that occur on the HB and

VBOOT pins after the corresponding MOSFET switch is

turned−off. The controller enables the opposite MOSFET in

the power stage once the corresponding dV/dt sensor output

provides information about HB (or VBOOT) pin transition

ends.

t

period

DEAD_TIME_MAX

3. The controller stops operation and restarts

operation after auto−recovery period in case the

ZSV condition has not been detected within the

selected t

period

DEAD_TIME_MAX

A DT fault counter option is available. Selected number

(N ) or DT fault events have to occur in order to

DT_MAX

confirm DT fault in this case.

A fixed DT option is also available for this device. The

internal dV/dt sensor signal is not used for this device option

The ZVS transition on the bridge pin (HB) could take a

longer time or even does not finish in some cases – for

example with extremely low bulk voltage or when some

critical failure occurs. This situation should not occur

normally in correctly designed application because several

other protections would prevent such a situation. The

NCP13992 implements maximum DT period clamp that

and the t

period is used as a regular DT

DEAD_TIME_MAX

period instead. The DT fault detection is disabled in this

case.

Temperature Shutdown

The NCP13992 includes a temperature shutdown

protection. The typical TSD hysteresis is 30°C. When the

temperature rises above the upper threshold, the controller

stops switching instantaneously, and goes into the off−mode

limits driver’s off−time period to the t

DEAD_TIME_MAX

value. The corresponding MOSFET driver is forced to

turn−on by the internal logic regardless of missing dV/dt

sensor signal. This situation does not occur during normal

operation and will be considered a fault state by the device.

There are several possibilities on how the controller

continues operation after this event occurrence – depending

on the IC option:

with extremely low power consumption. The V supply is

CC

maintained (by operating the HV start−up in DSS mode) in

order to memorize the TSD event information. When the

temperature falls below the lower threshold, the full restart

(including soft−start) is initiated by the controller. The HV

startup current source features an independent

over−temperature protection which limits its output current

in case the DIE temperature exceeds TSD to avoid damage

to the HV startup silicon structure.

1. The opposite MOSFET switch is forced to turn−on

when t

period elapses and no

DEAD_TIME_MAX

fault is generated

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22

NCP13992

APPLICATION INFORMATION

Controller Operation Sequencing of NCP13992 LLC

Controller

The paragraphs below describe controller operation

sequencing under several typical cases as well as transitions

between them.

for the feedback block. The VCC management controls the

HV startup in DSS mode in order to keep enough VCC level

to hold the latch−up state memorized while the application

remains plugged−in to the mains.

The power supply is removed from the mains at point H

and the VCC voltage drops down below V

level

CC_RESET

1. Application start, Brown−out off and restart,

OVP/OTP latch and then restart – Figure 23

Application is connected to the mains at point A thus the

HV input of the controller becomes biased. The HV startup

thus the low voltage controller is released from latch. A new

application start occurs when the user plugs the application

the mains again.

current source starts charged VCC capacitor until V

CC

2. Application start, Brown−out off and restart, output

short fault with auto−recovery restart – Figure 24

Operating waveforms descriptions for this figure is

similar to one for Figure 23 from point A till point G – with

reaches V

threshold.

CC_ON

The VCC pin voltage reached V

threshold in point

CC_ON

B. The BO, FB, OVP/OTP and PFC MODE blocks are

enabled. The VBULK/PFC FB pin starts to receive divided

bulk voltage as the external HV switch is activated by PFC

one difference. The skip mode operation (FB

<

V

) blocks the IC startup after first V event

FB_SKIP_IN

CC_ON

MODE output. The V blank is activated during each

CC

instead of BO_fault.

V

CC_ON

event to ensure that the internal logic ignores all

The LLC converter operation is stopped in point G

because the controller detects an overload condition (short

circuit event in this case as the Vout drops abruptly). The

controller disables all blocks except for the FB block and the

fault logic. The HV startup DSS operation is initiated in

order to keep enough VCC level for all internal blocks that

need to be biased. Internal auto−recovery timer counts down

fault inputs until the internal blocks are fully biased and

stabilized after a V event. The IC DRVs were not

CC_ON

enabled after first V blank period in this case as the

CC

voltage on VBULK/PFC FB is below V level. The IC

BO

keeps all internal blocks biased and operates in the DSS

(Dynamic Self−Supply) mode as long as the fault conditions

is still present.

the recovery delay period t

.

A−REC_TIMER

The BO_OK condition is received (voltage on

The auto−recovery restart delay period lapses at point H.

The HV startup current source is activated to recharge VCC

capacitor before a new restart.

VBULK/PFC FB reach V

level) at point C. The IC

BO

activates the startup current source to refill VCC capacitor

in order to assure sufficient energy for a new startup. The

The V

threshold is reached in point I and all the

CC_ON

VCC capacitor voltage reaches V

level again and the

CC_ON

internal blocks are biased. The V blank and OVP/OTP

CC

VCC blank period is started. The DRVs are enabled and the

blank period are started at the same time. The LLC converter

operation is enabled, including a dedicated startup and

soft−start period. The output short circuit is removed in

between thus the Vout ramped−up and the FB loop took over

during the LLC converter soft−start period.

application is started after V blank period lapses because

CC

there is no faults condition at that time.

Line and also bulk voltage drops at point D so the BO_OK

signal become low (voltage on VBULK/PFC FB drops

below V level). The LLC DRVs are disabled as well as

BO

3. Startup, skip−mode operation, low line detection

and restart into skip−mode – Figure 25

The application is plugged into the mains at point A thus

the HV input of the controller becomes biased. The HV

startup current source starts charging the VCC capacitor

OVP/OTP block bias. The PFC MODE output stay high to

keep the bulk voltage divider connected, so the BO block

still monitors the bulk voltage. The controller activates the

HV startup current source into DSS mode to keep enough

VCC voltage for operation of all blocks that are active while

the IC is waiting for BO_OK condition.

until V reaches the V

threshold.

CC

CC_ON

The VCC pin voltage reaches the V

threshold at

CC_ON

The line voltage and thus also bulk voltage increase at

point E so the Brown−out block provide the BO_OK signal

point B. The BO, FB, OVP/OTP and PFC MODE blocks are

enabled. The VBULK/PFC FB pin begins to receive divided

bulk voltage as the external HV switch is activated by the

once the V level is reached. The startup current source is

BO

activated after BO_OK signal is received to charge the VCC

capacitor for a new restart.

PFC MODE output. The V

blank period is activated

CC

during each V

events. This blank ensures that the

CC_ON

The V

level is reached in point F. The OVP/OTP

CC_ON

internal logic ignores all fault inputs until the internal blocks

are fully biased and stabilized after V event. The IC

block is biased and the VCC blank period is started at the

same time. The controller restores operation via the regular

startup sequence and soft−start after VCC blank period

lapses since there is no fault condition detected.

The application then operates normally until the

OVP/OTP input is pulled−up at point G. The controller then

enters latch−off mode in which all blocks are disabled except

CC_ON

DRVs are not enabled even after V blank period ends

CC

because the OVP fault condition is present. The OVP fault

condition disappears after some time so the HV startup

current source is enabled to prepare enough V for a new

CC

startup attempt. The new V blank and OTP blank periods

CC

www.onsemi.com

23

NCP13992

are placed after the V

event is detected. The controller

V

level during skip mode. The device would enters

CC_ON

CC_OFF

authorizes DRVs at point C as there are no faults conditions

into off−mode.

present after the V blank period elapses. The load current

is reduced thus the FB loop reduces the primary controller

FB pin voltage.

The line voltage drops in point F, but the bulk voltage is

dropping slowly as there is nearly no consumption from the

bulk capacitor during skip mode – only some refilling bursts

are provided by the controller. The application thus

continues in skip mode operation for several skip burst

cycles.

CC

The load diminished further and the FB skip threshold is

reached in point D. The controller turns−off all the blocks

that are not essential for the controller operation during

skip−mode – i.e. all blocks except FB block and VCC

management. This technique is used to minimize the device

consumption when there are no driver pulses during

skip−mode operation. The output voltage then drops

naturally and the FB loop reflects this change into the

primary FB pin voltage that increases accordingly. The

auxiliary winding is refilling VCC capacitor during each

skip burst thus the controller is supplied from the application

during the skip mode operation.

The controller FB skip−out threshold is reached in point

E; the controller enables all blocks and LLC DRVs to refill

the output capacitor. The controller did not activate the HV

startup current source because there is enough voltage

present on the VCC pin during skip mode. The OTP blank

periods is activated at the beginning of the skip burst to mask

possible OTP faults.

The bulk voltage level less than V threshold is detected

BO

by the controller in point G during one of the skip burst

pulses. The controller thus disabled DRVs and enters DSS

mode of operation in which the OVP/OTP block is disabled

and the controller is waiting for BO_OK event. The PFC

MODE provides the V

voltage in this case to

PFC_M_ON

allow the PFC stage to refill bulk capacitors.

The line voltage is increased at point H thus the controller

receives the BO_OK signal. The BO_OK signal is received

during the period in which the HV startup current source is

active and refills the VCC capacitor.

This V

threshold is reached by the VCC pin at point

CC_ON

I. The V blank period and OVP/OTP blank period are

CC

started at the same time. The full startup sequence is enabled

at the end of the V blank period as no fault is detected. The

CC

application then enters skip mode again as the load current

is low.

Note: The VCC capacitor needs to be chosen with a value

high enough to ensure that V will not drop below the

CC

www.onsemi.com

24

NCP13992

Figure 23. Application Start, Brown−out Off and Restart, OVP/OTP Latch and then Restart

www.onsemi.com

25

NCP13992

Figure 24. Application Start, Brown−out Off and Restart, Output Short Fault with Auto−recovery Restart

www.onsemi.com

26

NCP13992

Figure 25. Startup, Skip−mode Operation, Low Line Detection and Restart into Skip

www.onsemi.com

27

NCP13992

PACKAGE DIMENSIONS

SOIC−16 NB MISSING PINS 2 AND 13

CASE 751DU

ISSUE O

NOTE 5

NOTES:

1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.

2. CONTROLLING DIMENSION: MILLIMETERS.

D

A

2X

16

9

3. DIMENSION b DOES NOT INCLUDE DAMBAR PROTRUSION.

ALLOWABLE PROTRUSION SHALL BE 0.10 mm IN EXCESS OF

MAXIMUM MATERIAL CONDITION.

4. DIMENSIONS D AND E DO NOT INCLUDE MOLD FLASH,

PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS

OR GATE BURRS SHALL NOT EXCEED 0.25 mm PER SIDE.

DIMENSIONS D AND E ARE DETERMINED AT DATUM F.

5. DIMENSIONS A AND B ARE TO BE DETERMINED AT DATUM F.

6. A1 IS DEFINED AS THE VERTICAL DISTANCE FROM THE SEATING

PLANE TO THE LOWEST POINT ON THE PACKAGE BODY.

0.10 C D

F

NOTE 4

E

E1

NOTE 6

A1

L

L2

1

8

0.20 C

SEATING

PLANE

C

MILLIMETERS

B

NOTE 5

14X b

DETAIL A

2X 4 TIPS

DIM MIN

MAX

1.75

0.25

0.49

0.25

10.00

M

0.25

C A-B D

A

A1

b

1.35

0.10

0.35

0.17

9.80

TOP VIEW

2X

c

0.10 C A-B

0.10 C

DETAIL A

D

E

6.00 BSC

0.10 C

E1

e

3.90 BSC

1.27 BSC

L

0.40

1.27

0.203 BSC

L2

e

END VIEW

A

SEATING

C

PLANE

SIDE VIEW

RECOMMENDED

SOLDERING FOOTPRINT

14X

1.52

16

1

9

7.00

8

14X

0.60

1.27

PITCH

DIMENSIONS: MILLIMETERS

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28


型号：	NCP13992
厂家：	ONSEMI
描述：	High Performance Current Mode Resonant Controller
文件：	总28页 (文件大小：474K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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