DI-42 [POWERINT]
Non-isolated Flyback (Buck/Boost) Converter; 非隔离型反激式（降压/升压）转换器
| 型号： | DI-42 |
| 厂家： | 
Power Integrations |
| 描述： | Non-isolated Flyback (Buck/Boost) Converter |
| 文件： | 总2页 (文件大小：44K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
Design Idea DI-42
TinySwitch® Non-isolated Flyback
(Buck/Boost) Converter
Topology
Buck/Boost
Device
Power Output
Input Voltage
Output Voltage
Application
Appliances
1.2 W
85-265 VAC
TNY254P
12 V
there is no analog control loop to compensate. The low
switching frequency under light and no-load conditions
provides very low power consumption under these
conditions – see Figures 2 and 3.
Design Highlights
• Lowest cost non-isolated flyback converter
• Inherently short circuit & thermal overload protected
• Excellent line and load regulation characteristics
• Operates at 85 ˚C, without forced cooling
• Meets EN61000-4-5 (2 kV line surge – simple
modification provides a 6 kV line surge withstand)
• Input AC line is fed directly to the output
• Available for prototyping in DAK-7
Providing power for driving TRIACs normally requires the
output of the supply to be referenced to the input line as
shown in Figure 1. Therefore, only half-wave rectification
is used and the switch must be in the return or neutral side of
the primary switching circuit. In these applications, EMI
filtering is normally done at the system level and is therefore
not shown here.
Circuit Features
The circuitry shown allows this converter to meet 2 kV surge
requirements according to IEC standards. To extend surge
withstand to 6 kV, an MOV must be added between the Line
input and the node where D3 connects to R2. Additionally,
D3 must be replaced with 100 Ω, 5 W surge-rated resistor
(See DAK-7 for details).
This non-isolated Flyback (Buck-Boost) converter has been
implemented using a TinySwitch TNY254P, which minimizes
cost, PCB space and design time.
The most typical application for the circuit of Figure 1 is
poweringaTRIAC driveandassociatedcircuitry,inaconsumer
or industrial appliance, having TRIAC controlled motors.
The high efficiency of this converter (see Figure 4) allows
thecircuittooperatetoveryhighambienttemperaturesofup
to85˚C,assometimesspecifiedinhouseholdappliancesand
industrial applications.
The combined voltage drops of Zener diode (VR1) and
optocouplerdiode(U2)settheoutputvoltage.Duetothe digital
nature of the TinySwitch output voltage regulation scheme, the
currenttransferratio(CTR)oftheoptocouplerisnotcriticaland
+12 VDC
+
D2
UF4005
C3
U2
220 uF
25 V
VR1
1N5342B
L
C1
6.8 uF
400 V
L1
1.5 mH
85 - 265
VAC
TinySwitch
R2
180 Ω, 3 W
Fusible
D3
1N4007
D1
1N4007
TNY254P
S
D
C2
0.1 uF
50 V
N
BP EN
U2
SFH615-2
PI-3280-090502
Figure 1. TinySwitch – TNY254P, 1.2 W, 12 V 100 mA.
.
DI-42
September 2002
www.powerint.com
DI-42
100
80
Key Design Points
• Use low cost optocoupler - CTR is unimportant for output
regulation.
• PCB traces that carry switching currents should be short
and wide to minimize EMI.
60
• Select input and output capacitors to meet ripple current
requirements.
• Diode D2 must be an ultra-fast type, with reverse recovery
time (trr) ≤ 50 ns.
40
20
• Minimum recommended output voltage in this topology is
5 V.
0
50
Lower voltages may cause continuous mode operation,
forcing high reverse recovery currents in D2 and therefore,
lowering efficiency.
100
150
200
250
300
Input Voltage (VAC)
Figure 3. No-load Power Consumption.
1.2
80
1
0.8
0.6
70
60
50
0.4
VIN = 115 VAC
VIN = 230 VAC
0.2
VIN = 115 VAC
VIN = 230 VAC
0
0
.200
Output Power (W)
Figure 2. Output Power vs. Input Power.
.400
.600
.800
40
0
20
40
Output Power (mA)
Figure 4. Efficiency vs. Output Current.
60
80
100 120
For the latest updates, visit our Web site: www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any
license under its patent rights or the rights of others. The products and applications illustrated herein may be covered by one or more U.S.
and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power
Integrations’ patents may be found at www.powerint.com.
The PI Logo, TOPSwitch, TinySwitch and EcoSmart are registered trademarks of Power Integrations, Inc.
PI Expert is a trademark of Power Integrations Inc. ©Copyright 2002, Power Integrations, Inc.
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