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7/7

AN1686 APPLICATION NOTE

Figure 5. Circuit of figure 2 modified for autorecovery mode operation

In case of activation, the converter will be stopped and restarted after a delay set by the SS capacitor of the

L5991 (C6). If this delay is long enough, the Vcc capacitor (C2) may be discharged below the UVLO threshold

of the L5991, giving origin to even longer delays.

REFERENCES

[1] "45 W AC-DC Adapter with Standby Function" (AN1134)

[2] "L5991 Primary Controller with Standby" Datasheet

[3] "How to Handle Short Circuit Conditions with ST's Advanced PWM Controllers" (AN1215)

[4] "Minimize Power Losses of Lightly Loaded Flyback Converters with the L5991 PWM Controller" (AN1049)

4

VREF

D7

1N4148

7

ISEN

COMP

8

2

3

1

6

5

IC3A

LM393

IC3B

LM393

Q1

BC327

R23

10 k

Ω

R24

24 k

Ω

R25

4.3 k

Ω

R26

100 k

Ω

R27

2.2 k

Ω

C18

10 µF

ST-BY

Q2

BC337

D6

4V7

R28

3.3 k

Ω