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AN1317 - APPLICATION NOTE

5.2 Adjustable Output Voltage Structures

On the schematics of fig. 1 and 5, the output voltage is fixed and equal to the reference voltage of the

VIPer20, that is to say 13 V. When different voltages are needed, it is possible to modify these basic

structures to get other values.

Fig. 24 presents a +23V output non isolated Buck converter with a zener diode DZ2 in series with the

results, the output voltage will be regulated at +23 V.

The resistor R1, optionally added here on the line input, is an example of an inrush limiter and filter.

When lower output voltages are specified, an another configuration can be used, as shown on fig. 25. An

inductor with an intermediate tap is used in order to deliver a -5 V. This inductor can be of the same type

than an inexpensive drum vertically mounted on a PCB, except that three pins are provided instead of

two for a standard inductor.

Figure 24: Buck non isolated - Output voltage increased

13V

OSC

COMP

SOURCE

DRAIN

VDD

-

+

U1

VIPer20

R3

3.9k

C4

100nF

10k

R2

C3

10nF

D1

1N4007

C1

22uF

400V

L1

470uH

D3

BYT01-400V

C5

33uF

16V

D2

BYT01-400V

C2

10uF

16V

DZ1

BZX55CxxV

C6

2.2uF

35V

DZ2

BZX55C10V

AC IN

AC IN

+23V

GND OUT

100

R1