FA5331P Datasheet, PDF (7/13 Pages) Fuji Electric – Bipolar IC For Power Factor Correction

FA5331P(M)/FA5332P(M)
6. ON/OFF control input circuit
Figure 7 shows the ON/OFF control input circuit. If pin 12 is set
to the high level (enable), this IC outputs pulses from the OUT
pin. If pin 12 is set to the low level (disable), the internal bias
power (reference voltage) goes off and the IC current
consumption becomes about 1/10 that of its ON state. The
output level of pin 11 (CS for soft start) also goes low.
7. Output circuit
As Fig. 8 shows, pin 9 is configured as the high power terminal
(VC), independent of the IC power terminal (VCC). This pin
allows an independent drive resistance when the power
MOSFET is ON and OFF. If the drive resistances in the ON and
OFF states are Rg (on) and Rg (off), the following formulas can
be used to determine the total gate resistance
Rg:
Rg (on) = Rg1 + Rg2 ............................................. (9)
Rg (off) = Rg2 ..................................................... (10)
In the standby state, the output level of pin 8 is held low.
If the potential at the drain terminal of the power MOSFET
fluctuates, the gate-drain capacitance may drive the IC output
voltage at pin 8 to below 0. Once the voltage at pin 8 reaches
–0.6V, an unwanted current flows in the IC and a large abnormal
current flows in the output circuit when the output transistor is
turned on. To prevent this, connect a Schottky diode across the
gate and source of the power MOSFET.
ON/OFF
12
Vcc
10µA
1k
100k
Fig. 7 ON/OFF control input circuit
VCC
10
9
8
+
Rg1 _Cv
Pin7
Rg2
GND
7
Schottky
diode
Fig. 8 Output circuit
7