L6668

18/23

Figure 43 shows a timing diagram where the PFC_STOP function operation is illustrated under different

operating conditions.

Figure 42. How the L6668 can switch off a PFC controller at light load

Figure 43. Operation of PFC_STOP function

Figure 44. Operation after DIS pin activation: timing diagram

L6668

PFC_STOP

14

16

Vcc

10 k

Ω

BC557

2.2 k

Ω

PFC

controller

Vcc

8.2 V

L6668

PFC_STOP

14

16

Vcc

10 k

Ω

BC557

2.2 k

Ω

PFC

controller

Vcc

8.2 V

Vcc

PFC_STOP

OUT

t

t

t

t

PFC

Gate

Drive

t

COMP

2.2V

2.7V

Start-up

Full-load

Light-load

Full-load

Vcc

OUT

Vin

t

t

t

t

2.2V

DIS

HV generator is turned on

Disable latch is reset here

HV generator is disabled here

Input source is removed here

Vcc

OUT

Vin

t

t

t

t

2.2V

DIS

HV generator is turned on

Disable latch is reset here

HV generator is disabled here

Input source is removed here