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4. Power Circuit for P.W.B.
● Fig. 4-1 shows the power circuit for P.W.B. and waveform at each point.
● In the power circuit for P.W.B., power supply for microcomputer, peripheral circuits, and system power
module driver circuit and, as well as DC 35V, are produced by switching power circuit.
● Switching power circuit performs voltage conversion effectively by switching transistor IC901 to convert
DC 330V voltage to high frequency of about 20kHz to 200kHz.
● Transistor IC901 operates as follows:
(1) Shifting from OFF to ON
● DC about 330V is applied from smoothing capacitors C010 Œ and C011 œ in the control power circuit.
With this power, current flows to pin of IC901 via R903 and R904 and IC901 starts to tum ON. Since
voltage in the direction of arrow generates at point at the same time, current passing through R910 and
D903 is positive-fed back to IC901.
4
C
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