AN1344 Datasheet, PDF (12/14 Pages) STMicroelectronics – The VIPer100A-E is designed to deliver

Transient response 50% step change
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Transient response 50% step change
AN1344
The output current is modulated from 3 A to 6 A, 50% duty cycle at a line input of 115 V_AC.
The result is 322 mV or 1.8% dynamic regulation with a settling time of 500 microseconds.
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Output ripple
The ripple was measured using an HP probe socket attached after the output connector.
This minimizes stray noise being picked up by the scope probe ground lead, which shows up
as high frequency noise.
The top trace shows the reduction in cost from eliminating L4 and C11. This gives a ripple,
at 6 A load, of 125 mV peak to peak. With the low pass filter the ripple is reduced to about
13 mV excluding voltage spikes.
9
EMI consideration
When dealing with EMI, it is always best to reduce noise at its source. Figure 11 shows FCC
class B plots comparing EMI at 6 amps load with snubber R3 and C4 in and out. The blue
trace, or lower trace, has the RC snubber across the diode. The EMI is reduced by 4 to 8 db.
Adding a 2W resistor and a capacitor here is much less expensive than adding across the
line capacitors and inductors in the EMI filter. This unit passed both EN55022 class B and
FCC class B.
10 Performance and cost consideration
This design has been optimized for performance. Cost can be reduced by substituting a 17V
zener for the TL431. The output regulation falls to the +/- 5% voltage set point, plus a
+0.084/°C temperature drift of the zener. The cost of the TL431 and 3 other passive
components can then be eliminated. If more output ripple voltage can be tolerated, than L4
and C11 can be eliminated.
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Conclusion
This design delivers over 100 W for both voltage ranges by utilizing the VIPer100A-E with a
voltage doubler in the front end. The power supply has excellent regulation, current limiting,
short circuit protection, meets both EN55022 and FCC class B and best of all is from
STMicroelectronics.