(L-L) Switching Regulator Unit; (A) Rectifying And Filtering Circuit; (B) Auxiliary Power Supply Circuit - NEC MultiSync 4FGe Service Manual

l-1. Switching regulator unit
(a) Rectifying and-filtering circuit
AC input is rectified by D601. Then, it is filtered by C601. The resulting DC voltage is supplied to the '
converter
circuit.

(b) Auxiliary power supply circuit

The auxiliary power supply circuit is needed to activate IC601. At the time when the power is turned on, the
charging current flows into the capacitors C603 via R601. Oscillation starts when the voltage of IC601
reaches 16V by this charging operation.
After the start of oscillation, the flyback voltage of the auxiliary winding for the switching transformer is
rectified and filtered by D608 and C603. The resulting DC voltage is supplied to IC601.
(Fig l-i -1) Rectifying and Filtering Circuit
C601
(Fig
l-1 -2) Auxiliary Power Supply Circuit
36
0
C
m
m
A
R601
D608