Open loop failure protection

VIPER16

18/25

Doc ID 15232 Rev 5

15

Open loop failure protection

In case the power supply is built in fly-back topology and the VIPer16 is supplied by an

auxiliary winding, as shown in Figure 27 on page 18 and Figure 28 on page 19, 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 on page 18 and

Figure 28 on page 19, respectively the non-isolated fly-back and the isolated fly-back.

output through the secondary-to-auxiliary turns ratio.

reported on Table 8 on page 7) and the clamp current injected on 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

case of isolated fly-back).

Figure 27.

FB pin connection for non-isolated fly-back

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