NCP1379 ON Semiconductor, NCP1379 Datasheet - Page 19

• Manufacturer Part Number: NCP1379
• Description: Quasi-Resonant Current-Mode Controller
• Manufacturer: ON Semiconductor

the signal on ZCD pin (pin 1). Indeed, a negative voltage
applied on this pin directly affects the internal voltage
reference setting the maximum peak current (Figure 35).
winding voltage becomes a negative voltage proportional to
needed to bypass R
The over power compensation is achieved by monitoring
When the power MOSFET is turned−on, the auxiliary
To ensure optimal zero−crossing detection, a diode is
opu
during the off−time.
Au x
Figure 34. Auto−Recovery Overload Protection Chronograms
Rz cd
Ropu
Ropl
Figure 35. Over Power Compensation Circuit
OVER POWER COMPENSATION
ZC D / O P P
1
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DRV
ESD
pr ot ect ion
Vth
CS
19
leakage blanking
the input voltage. As the auxiliary winding is already
connected to ZCD pin for the valley detection, by selecting
the right values for R
over power compensation.
on−time, we obtain the following relationship:
If we apply the resistor divider law on pin 1 during the
Tblank
V IL IMIT
+
−
OPP
opu
and R
IpFlag
Demag
opl
, we can easily perform
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