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AN1317 - APPLICATION NOTE

Figure 25: Non isolated inverter - Reduced output voltage.

6. CONCLUSION

It has been demonstrated that the simple topologies as the Buck or the inverter can be used directly on

off line applications to build efficient non isolated power supplies in the range of a few watts. A VIPer20

device can minimize the total number of components by offering the error amplifier, the PWM and the

Power MOSFET together inside a single piece of silicon.

A special care must be taken when designing the Buck topology, as it can provide serious output

overvoltages in case of low input voltage, and/or low output load. A simple zener diode on the output, or

a more efficient switching frequency shifter network can overcome this issue.

The benefits of such low power structures over more conventional 50 Hz transformers followed by

rectifiers, filters and serial regulators can be listed as follow:

• Wide range of input voltages with good output regulation

• Higher efficiency and lower standby consumption

• Lighter weight, with direct implementation on a standard PCB

AC IN

-xxV

GND OUT

AC IN

D1

1N4007

C3

10nF

D2

BYT01-400V

D3

BYT01-400V

C1

1uF

400V

13V

OSC

COMP

SOURCE

DRAIN

VDD

-

+

U1

VIPer20

C5

22uF

16V

L1

470uH

R3

3.9k

C2

10uF

16V

C4

100nF

R2

10k