Open-loop failure protection

VIPER06

20/28

Doc ID 022794 Rev 1

15

Open-loop failure protection

If the power supply has been designed using flyback topology and the VIPER06 is supplied

by an auxiliary winding, as shown in Figure 27 and Figure 28 on page 21, the converter is

protected against feedback loop failure or accidental disconnections of the winding.

The following description is applicable for the schematics of Figure 27 and Figure 28 on

page 21, respectively the non-isolated flyback and the isolated flyback.

output through the secondary-to-auxiliary turns ratio.

given in Table 7 on page 8) and the clamp current injected on the VDD pin exceeds the latch

generated.

In order to distinguish an actual malfunction from a bad auxiliary winding design, both the

above conditions (drain current equal to the drain current limitation and current higher than

isolated flyback).

Figure 27.

FB pin connection for non-isolated flyback

V

COMPL

D

AUX

nR

FB

VDD

V

AUX

COMP

+

-

to PWM

R

L

E/A

R

H

R

R

AUX

C

VDD

V

OUT

V

REF_FB

from R

SENSE

BUS

+

-

PWM stop