KA7541DTF [ROCHESTER]

0.3A FLUORESCENT LIGHT CONTROLLER, 56kHz SWITCHING FREQ-MAX, PDSO8, SOIC-8;


型号：	KA7541DTF
厂家：	Rochester Electronics
描述：	0.3A FLUORESCENT LIGHT CONTROLLER, 56kHz SWITCHING FREQ-MAX, PDSO8, SOIC-8 开关光电二极管
文件：	总17页 (文件大小：811K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

www.fairchildsemi.com

KA7541

Simple Ballast Controller

Features

Descriptions

• Internal soft start

• Flexible soft start frequency

• No lamp protection

• Trimmed 1.5% internal bandgap reference

• Under voltage lock out with 1.8V of hysteresis

• Totem pole output with high state clamp

• Low start up and operating current

The KA7541 provides simple and high performance

electronic ballast control functions. KA7541 is optimized for

electronic ballast requiring a minimum board area, reduced

component count and low power dissipation. Internal soft

start circuitry eliminates the need for an external soft start

PTC resistor. The initial soft start switching frequency and

soft start time can be adjusted depending on the types of

lamps. Protection circuitry has also been added to prevent

burning out of switches in no lamp condition. output gate

drive circuit clamps power MOSFET gate voltage

irrespective of supply voltage

8-DIP

8-SOP

Rev. 1.0.3

KA7541

Internal Block Diagram

UVLO

2V Ref

−

1.8V

Internal

bias

0.22µF

−

2.5µA

Vref

9.5V

UVLO

Ik = I / 6

Ict

OUT 1

Oscilator

180pF

S Q

Oscilator

F.D

8Ict

latch

30k

Ω

OUT 2

−

Current

mirror

3pF

22k

Ω

Frequency

divider

Vref

40k

Ω

= Ik

(Vref

−

V ) / Vref

Ldet

−

GND

= Vref / R

5pF

Shut down signal

Absolute Maximum Ratings

Parameter

Supply voltage

Symbol

Value

Unit

Peak drive output current

, I

±300

OH OL

Drive output clamping diodes

Iclamp

±10

V >V , or V <−0.3

Soft start, and no lamp detection input voltage

Operating temperature range

−0.3 to 6

-25 to 125

−65 to 150

0.8

Topr

Tstg

°C

Storage temperature range

8-DIP

8-SOP

8-DIP

8-SOP

Power dissipation

0.5

100

Thermal resistance (Junction-to-air)

θja

°C/W

165

Absolute Maximum Ratings (-25°C≤Ta≤125°C)

Parameter

Symbol

∆Vref(Typ)

∆fos(Typ)

Value

Unit

Temperature stability for reference voltage (Vref)

Temperature stability for operating frequency (fos)

kHz

KA7541

Pin Assignments

OUT1

OUT2

GND

Ldet

(Top View)

Pin Definitions

Pin Number

Pin Name

Pin Function Descrition

Soft start capacitor connection pin. The pin voltage determines the phase of soft

start, normal mode.

Timing capacitor connection pin. The timing capacitor is charged and discharged

to generate the sawtooth waveform that determines the oscillation frequency in

the internal oscillator block.

Soft start resistor connection pin. The soft start resistor value determines the initial

preheating switching frequency during soft start mode.

Input to the protection circuit. If the pin voltage is lower than 2V, the output of the

gate driver is inhibited.

Ldet

GND

The ground potential of all the pins.

The output of a high-current power driver capable of driving the gate of a power

MOSFET

OUT 2

The output of a high-current power driver capable of driving the gate of a power

MOSFET.

OUT 1

The logic and control power supply connection.

KA7541

Electrical Characteristics

Unless otherwise specified, for typical values Vcc=14V, Ta=25^oC, For Min/Max values Ta is the operating ambient

temperature range with -25^oC ≤ Ta ≤ 125^oC and 11V ≤ V

≤ 30V

Parameter

UNDER VOLTAGE LOCK OUT SECTION

Start threshold voltage

UVLO hysteresis

Symbol

Conditions

Min. Typ. Max. Unit

TH(st)

increasing

8.5

1.3

9.5

1.8

10.5

2.3

(st)

SUPPLY CURRENT SECTION

Start up supply current

Operating supply current

Dynamic operating supply current

REFERENCE SECTION

Reference voltage

<V (st)

0.15 0.25

CC TH

Output not switching

50kHz, CI=1nF

DCC

Iref=0mA, Vcc=14V

1.95

2.05

ref

Line regulation

∆V

14V≤V ≤25V

0.1

ref 1

ref 2

Temperature stability of Vref

OSCILLATOR SECTION

Operating frequency

-25≤Ta≤125°C, Vcc=14V

fos

=3V, C =470pF

2.4

2.9

3.4

KHz

µs

Operating dead time

tod

fss

tsd

=3V, Vcc=14V

Soft start frequency

=0V, C =470pF

KHz

µs

Soft start dead time

=0V, Vcc=14V

1.8

2.3

2.8

OUTPUT SECTION

Rising time ^(note1)

Falling time ^(note1)

CI=1nF, Vcc=12V

120

200

100

Maximum output voltage

Output voltage with UVLO activated

NO LAMP PROTECTION SECTION

No lamp detect voltage

=20V

omax(o)

=5V, I =100µA

omin(o)

Vnd

1.9

2.1

Note:

1. These parameters, although guaranteed, are not 100% tested in production.

KA7541

Start-up Circuit

Start up current is supplied to the IC through the start up resistor (Rst). In order to reduce the power dissipation in Rst, the Rst

is connected to the full wave rectified output voltage.

The following equation can be used to calculate the size of Rst

(Vin(ac_max) 2 – Vcc)²

Vin(ac) × 2 – Vth(st),max

------------------------------------------------------------------------

≤ 0.5W

P_RSt

--------------------------------------------------------------------------

Rst <

R_St

_St≥ 2 × (Vin(ac_max) 2 – Vcc)²

_St≥ 260K

Ist,max

260K ≤ R_St≤ 440K

85 × 2 – 10.5

= ------------------------------------- = 440kΩ

0.25 × 10^–3

The size of start up capacitor (Cst) is normally decided in terms of the start up time and operating current build up time with

auxiliary operating current source.

The turn off snubber capacitor (Cq2) and two diodes (D1, D2) constitute the auxiliary operating current source for the IC. The

charging current through the Cq2 flows into the IC and also charges the start-up capacitor. If the size of Cq2 is increased, the

voltage of the Cst is also increased.

Rectifier

Output

Cq2

Rst

To V

(Pin 8)

Cst

−

Figure 1. Start up circuit

Oscillator

The gate drive output frequency is as half as that of the triangular waveform in timing capacitor (Ct) at pin #2. In normal

operating mode, the timing capacitor charging current is 50µA. The discharging current is seven times of the charging current

(7× 50µA). The charging period of the timing capacitor is the on duty of the gate drive. The discharging period is the off duty

of the gate drive.

The rising slope and falling slope of the triangular waveform are as following.

Rising slope: dv / dt = i / C = 50µA / Ct

Falling slope: dv / dt = i / C = 7 × 50µA / Ct

For example, when the timing capacitor is 180pF,

∆Tch = 6.69µ

∆Tdis = 0.956µ

KA7541

Vct

2.86V

(Pin #2)

1.0V

14V

Voutput

(Pin #6, 7)

Charging

Period(∆Tch)

Discharging

Period(∆Tdis)

Figure 2. Oscillator sawtooth & Output gate drive waveform

As a result, the switching frequency is as following

Ts = 2 × (∆Tch + ∆Tdis) = 15.29µ

fsw = 1 / T = 65KHz

The explicit equation calculating the size of the timing capacitor for a certain switching frequency is written below.

11.76 × 10^–6

C_t= --------------------------------

f_sw

Soft Start

The switching frequency is linearly decreasing from the pre-heating frequency to the normal switching frequency.

In KA7541, the initial pre-heating frequency can be adjusted depending on the types of the lamps used. During the pre-heating

mode, a sixth of the soft start current (I ) which flows through the soft start resistor (R ) at pin #3 is added to the normal

timing capacitor charging current (50µA). The rising and falling slope of the triangular waveform are increased due to this

added current.

Soft start current (I ) = 2V / R

Rising slope: dv / dt = i / C = (50µA + I / 6) / Ct

Falling slope: dv / dt = i / C = 7 × (50µA + I / 6) / Ct

So, once the value of R and Ct are known, the pre-heating frequency can be calculated straightforward by using the

following equation.

50 × 10^–6+ -----------

0.33

fsw(pre) = ------------------------------------------

Ct × 4.25

The dead time ratio during pre-heating mode is maintained to be constant as well as in normal mode.

(on duty: dead time = 7:1 )

The voltage of the soft start capacitor (C ) determines the soft start time (tss). When VCC voltage exceeds the start-up voltage

(Vth(st)), the soft start capacitor start to be charged by the current source (313nA). The switching frequency decreases linearly

to fsw(nor) from fsw(pre) until the soft start capacitor voltage (V ) touches 2V. Therefore the soft start duration time (tss)

can be acquired by the following formula.

KA7541

Cs × V

tss = -----------------

0.2 × 10^–6× 2

313 × 10^–9

-----------------------------------

= 1.28s

For example, the soft start capacitor of 0.2µF makes the soft start time (tss) to be 1.28sec.

fsw, V

fsw (pre)

fsw (nor)

tss

Figure 3. Frequency & Soft start capacitor voltage variation during soft start

No Lamp Protection

When the voltage at pin #4 is lower than 2V, the gate drive output is off state, so the external power MOSFET stops switching.

In no lamp protection circuit the dc link voltage is divided by a couple of resistors including both lamp filaments, and The

divided voltage is applied to the pin #4 before the MOSFETs start switching.

R₄

---------------------------------------------------------------------

R₂+ R₃+ 2 × R_f

R₁+ ----------------------------------------- + R₄

V_R4= Vdd ×

15KΩ

--------------------------------------------------------------------------------------------

400 ×

330KΩ + 680KΩ

180KΩ + -------------------------------------------- + 15KΩ

R₃

--------------------

V₃= V₂×

200V

R₂+ R₃

When in normal mode the average voltage of the V3 is the half of the dc link voltage (Vdd). So, in order to make stable start

condition, the resistors are designed to make the voltage of V3 to be the half of the dc link voltage.

KA7541

DC Link Voltage (Vdd)

Rfilament

To pin #4

Figure 4. Lamp detection resistor network

KA7541

Application Circuit

<85 ~ 265V Input, 400V , 32W×2 Lamps Ballast>

Full-wave Rectified Output

PFC Output

NTC

C3 C4

FAN7527

TNR

AC INPUT

To PFC Output

R15

C15

C17

C18

C19

R14

C14

R10

C21

R11

C20

C16

R16

To full-wave

rectified voltage

R12

C10

KA7541

R17

R18

R13

C13

C11 C12

R19

KA7541

Component Listing

Part number

Value

2.7MΩ

Note

1/4W

Manufacturer

18kΩ

1/4W

R3, 12

R4, 13

R5, 10, 11

150kΩ

22kΩ

1/4W

47Ω

1/4W

3.3Ω

1/4W

0.2Ω

1.2MΩ

1/4W

103

Variable resistor

1/4W

R14

180kΩ

R15, 16

R17, 18

R19

330kΩ

1/4W

680kΩ

1/4W

15kΩ

1/4W

C1, 2

C3, 4

150nF, 275vac

2200pF, 3000V

0.22µF, 630V

47µF, 35V

0.33µF

Box-Cap

Y-Cap

Miller-Cap

Electrolytic

MLCC

C6, 10

1nF, 25V

47µF, 450V

0.22µF, 25V

180pF, 25V

0.1µF, 25V

1nF, 630V

4700pF, 1000V

6800pF, 630V

500V, 3.6A

1000V, 1A

75V, 150mA

600V, 1A

15V, 1W

Ceramic

Electrolytic

Ceramic

Miller-Cap

FQPF6N50

1N4007

UF4007

1N4148

1N4937

1N4744

Line Filter

EI3026

EI2820

EE1614

Fuse

C11, 21

C12

C13

C14

C15, 16

C17, 18, 19, 20

Q1, 2, 3

D1, 2, 3, 4

FairChild

D7, 8

ZD1

45mH

590µH (62T:5T)

3.1mH (120T)

1.2mH(30T:60T)

250V, 3A

470V

L3, 4

TNR

471

NTC

10Ω

10D09

KA7541

Mechanical Dimensions

Package

Dimensions in millimeters

8-SOP

0.1~0.25

MIN

0.004~0.001

1.55 ±0.20

0.061 ±0.008

6.00 ±0.30

0.236 ±0.012

1.80

0.071

MAX

3.95 ±0.20

0.156 ±0.008

5.72

0.225

0.50 ±0.20

0.020 ±0.008

KA7541

Mechanical Dimensions ^(Continued)

Package

Dimensions in millimeters

8-DIP

6.40 ±0.20

0.252 ±0.008

3.30 ±0.30

0.130 ±0.012

5.08

MAX

0.200

7.62

0.300

3.40 ±0.20

0.134 ±0.008

0.33

MIN

0.013

KA7541

Ordering Information

Product Number

KA7541

Package

Operating Temperature

8-DIP

-25°C ~ +125°C

KA7541D

8-SOP

KA7541

DISCLAIMER

FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY

PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY

LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER

DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.

LIFE SUPPORT POLICY

FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES

OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR

CORPORATION. As used herein:

1. Life support devices or systems are devices or systems

which, (a) are intended for surgical implant into the body,

or (b) support or sustain life, and (c) whose failure to

perform when properly used in accordance with

instructions for use provided in the labeling, can be

reasonably expected to result in a significant injury of the

user.

2. A critical component in any component of a life support

device or system whose failure to perform can be

reasonably expected to cause the failure of the life support

device or system, or to affect its safety or effectiveness.

www.fairchildsemi.com

9/27/01 0.0m 001

Stock#DSxxxxxxxx

2001 Fairchild Semiconductor Corporation

Product Folder - Fairchild P/N KA7541 - Electronic Ballast Controller

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KA7541DTF [ROCHESTER]

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