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DI-28 PDF预览

DI-28

更新时间: 2022-04-23 23:00:11
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帕沃英蒂格盛 - POWERINT /
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2页 49K
描述
3 W Charger: <30 mW No-load Consumption

DI-28 数据手册

 浏览型号DI-28的Datasheet PDF文件第2页 
®
Design Idea DI-28  
TinySwitch®-II 3 W Charger:  
<30 mW No-load Consumption  
Topology  
Flyback  
Device  
Power Output  
Input Voltage  
Output Voltage  
Application  
Charger  
3 W  
85-265 VAC  
TNY264P  
5 V, 600 mA  
the internal current source at no-load. Other load conditions  
are not important as the device will be powered from the  
DRAIN pin if bias is lost, allowing a simple flyback winding  
to be used. Figure 2 shows that the bias winding and choice  
of R2 should provide approximately 550 µA at no-load to  
minimize consumption.  
Design Highlights  
• Less than 30 mW no-load power consumption (for  
115/230 VAC input)  
• Meets CISPR-22 Class B without Y capacitor  
• Low cost, low component count solution  
The circuit meets CISPR-22 Class B conducted EMI limits  
without aYcapacitorandthereforehasverylowACleakage  
current. TinySwitch-II frequency jitter, use of the bias  
winding as a shield and capacitor C3 to soften leakage  
inductance spikes combine to provide the EMI performance.  
Operation  
The TinySwitch-II flyback converter in Figure 1 generates a  
constant voltage, constant current (CV/CC) 5 V,  
600 mA output. Typical applications include wall-mounted  
chargers for cell phones, PDAs and other battery powered  
portable equipment.  
Key Design Points  
The key performance characteristic of the circuit shown is the  
extremely low no-load consumption of <30 mW. A linear  
transformer charger of similar rating will typically consume  
1 W to 4 W at no-load. At $0.12/kWh, the TinySwitch-II can  
therefore reduce energy costs by $1 to $4 per year.  
• Design bias winding circuit to provide approximately  
550 µA at no-load. Figure 2 shows the details.  
• Minimizesecondarycircuitbiascurrents. Uselowcurrent  
feedback Zeners for best tolerance. The very low bias  
current in this design will provide approximately ±10%  
output voltage tolerance. A precision reference (e.g.  
TL431) can be used to reduce this if required.  
• Designtransformerwithlowreflectedvoltagetominimize  
clamp losses. A bigger device (TNY266) may help to  
further reduce VOR.  
• Wind transformer for lowest leakage inductance. Choose  
wire gauges to completely fill winding layers.  
• Winding transformer with tape between primary layers  
further reduces intra-winding capacitance and no-load  
consumption.  
The no-load performance is achieved by using a transformer  
biaswindingasalowvoltagesourceforTinySwitch-IIoperating  
current. Even without this winding, a TinySwitch-II circuit will  
consume <300 mW at no-load. However, by providing external  
bias, the internal high voltage current source, which normally  
powers the IC from the DRAIN pin, is disabled and a further  
reduction in consumption is therefore achieved.  
Thebiaswindingshouldprovideenoughcurrenttofullydisable  
D7 11DQ06  
1
8
+5 VDC  
L3  
C6  
L1  
1.0 mH  
8T  
24 AWG  
Ferrite  
Bead  
C3  
470 µF  
10 V  
2.2 nF  
R3  
1.5 kΩ  
VR1  
BZY97C200  
1 kV  
7
3
D6 1N4148  
D1  
D2  
105T  
33 AWG  
RF1  
8.2 Ω  
1.0 W  
1N4005 1N4005  
C7  
D5  
1N4937  
13T x2  
31 AWG  
4
R2  
5.1 kΩ  
C5  
100 µF  
2
47 µF  
Q1  
2N3906  
10 V  
16 V  
L
C2  
4.7 µF  
400 V  
C1  
4.7 µF  
400 V  
85 - 265  
VAC  
TinySwitch-II  
VR3  
BZX79B5V1  
U1  
R4  
820 Ω  
TNY264P  
N
D
S
EN  
BP  
U2  
D3  
1N4005  
D4  
1N4005  
L2  
Bead  
2.2 µH  
C4  
0.1 µF  
50 V  
R5  
2.7 Ω  
2 W  
U2  
PC817A  
RTN  
PI-3079-091402  
Figure 1. TinySwitch-II 3.0 W Cell Phone Charger.  
September 2002  
DI-28  
www.powerint.com  

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