Canon Canovision8 E50E Service Manual page 170

Chapter E Circuit Operation
*k 4. Overview :
i The AC power supplied from a commercial receptacie flows through the primary noise filter circuit and
fullwave-rectified and smoothened by D1, L2 and C7, then it becomes the DC power, Then it goes through
T1 and becomes pulse current by Q1 which is switched by PHM signal (130 kHz approx.) outputted from pin
2 of 1€51, By this pulse current, pulse voltage is generated at the secondary circuit. It is rectified
and smoothened by 02%, C21, C22, 121 etc., and outputted from the output terminal.
The state of secondary side is fed back to the primary side by PHC1.
PRIMARY SECONDARY SECONDARY
RECTIFIER RECTIFIER FILTER
CIRCUIT ma h o s CIRCUIT CIRCUIT
a, €1,62.L1 D1,C7,L2
Fig. 1
2. Switching Circuit
When the power is supplied, starting voltage is applied to pin 20 of IC51 via R1~4 (starting resis-
- tances). IC51 starts to operate and outputs PWM signal (130kHz approx.) from pin 2. By the PWM signal,
\ Qi is switched over to control pulse current which flows pins 1 and 2 of T1.
= PRIMARY SECONCARY
RECTIFIER RECTIFIER
CIRCUIT «= CIRCUIT
- eee whee EA. Fate ales ager - Fig. 2.