Data Brief
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Rev 1
February 2006 1/5
5
STEVAL-ISA001V1
6W Dual O utput Supply using VIPer12A
Features
QSwitch mod e General Purpose Po wer Supply
QInput: 85 to 264 VAC @ 50/60 Hz
QOutp ut: 12V @ 0.5A
QOutp ut Power (peak) 6W
QBurst Mode Operation in Standby for Blue
Angel operation
QCurren t Mode Control
QSwitching Frequency 60 kHz
QOver 74% Efficiency
QAuxiliary Undervoltage Lockout with Hysteresis
QOutp ut Short Circuit Protection
QTherm al Shutdo wn Protection
QMeets EN55022 Class B EMI specification
Applications
This board is an off-line wide range dual output
general-purpose power supply capable of
delivering a total output power up to 6W. In low
load condition, it operates in the automatic burst
mode while in an overvoltage condition it will
operate in hiccup mode. Other output voltages
can easily be achieved by changing the
transformer and a few components on the board,
as shown in the application note. Transformers
are readily available for the following
configurations:
Q5V/12V
Q5V/15V
Q5V/24V
Blue angel
The reference board consumes less than 1W tot al
power consumption when working in the burst
mode during standby operation and therefore,
meets Blue Angel. Table 2 below outlines the tot al
power consumption measured on the reference
board at different line voltages with zero loads at
both the outputs. The output voltages remain
regulated when operating in burst mode condition.
STEVAL-ISA001V1
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General circuit description STEVAL-ISA001V1
2/5
1 General circuit description
The circuit operates from 85Vac to 264Vac input voltage with an output power peak of 6W
through two output voltages of 5Vdc and 12Vdc. It contains an input fuse (F2), EMI filtering (C1,
L1, and C2), and the secondary regulation is provided by U2 and U3, the optocoupler and
TL431 respectively. For output filtering, the components used are the output capacitors C8 and
C 10. These two output capacitors are sized according to the ripple current and ripple voltage
spe cifications. The two specifications det ermine the ES R and RMS current capabilities of th e
capacitors used . An additional LC (PI) filter is added to the 5Vdc output, C9-L2 configuration,
for further eff ective ripple and noise rejection. The AC input is rectified and filt ered by the bridge
BR1 and the bulk capacitor C1 to generate the high voltage DC bus applied to the primary
winding of the transformer , T1. The 5Vdc output is sensed with an optocoupler. It is possible to
modify the output volt ages by changing the transformer turns ratio and modifying the resistance
values of R7 a nd R8 in the feedback loop. R2 and C4 form the snubber circuit needed to
reduce the voltage ringing on the drain pin and the leakage spikes.
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STEVAL-ISA001V1 Bo a rd S che m ati c
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2 Board Schematic
Figure 1. Scheme
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Revision history STEVAL-ISA001V1
4/5
3 Revision history
Date Revision Changes
01-Feb-2006 1 Initial release.
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STEVAL-ISA001V1
5/5
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