Panasonic Generation Plasma Display Television - Manual (Page 36)

PFC Circuit
Pin 16 of IC501 also goes low when pin 23 is “high”. When pin 16 goes “low”, the diode within the photo-coupler
IC401 emits light to turn on the photo-transistor.
Pin 4 of IC401 goes “low”. This “low” is applied to the gate of Q401 turning it on to apply 12V to pin 8 of PFC
circuit.
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