NCP1239
Standby Detection
Standby is not confirmed
Standby is confirmed,
Jittering 10ms*
Vpin6
(SS/timer)
4.3V
3.0V
1.8V
100ms*
delay
100ms*
PFC is down
PFC running
Bunches of pulses
Drv
FB
No delay
FB−stby−out (1.7*Vpin7)
FB−skip (Vpin7)
Fb is ok
Skip activity
Stby_detect latch is armed
Stby_detect latch is reset
Standby is entered
Standby is left
*This time is programmed by the Pin 6 capacitor. C
= 390 nF nearly sets the following intervals:
pin6
− Soft−Start Time (T ):7.5 ms
ss
jittering
− Jittering Period (T
): 10 ms
− Fault Detection Delay (T
): 100 ms
delay
More generally, the times approximately depend on C
as follows:
pin6
− T = 7.5 ms * C
/ 390 nF
ss
pin6
− T
− T
=10 ms * C
=100 ms * C
/ 390 nF
jittering
pin6
pin6
/ 390 nF
delay
Figure 34. Standby Detection
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