Sharp AL-1043, Руководство по обслуживанию

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AL-1551 ELECTRICAL SECTION 12-15
B. Circuit descriptions
(1) Main section
a. Noise filter circuit
The noise filter circuit of the DC power is composed of L and C as shown
in the figure below. It reduces normal mode noises and common mode
noises which come from and go to the AC line.
The normal mode noises are noises which are generated in the AC line
or the output line and are attenuated by C4B and C3. The common mode
noises are noise voltages generated between the AC line and GND, and
are attenuated by L1 and L2. The noise composition is bypassed to GND
through C4 and C5.
b. Rectifying/smoothing circuit
The AC voltage of 50(60)Hz is full-wave rectified by the rectifying diode
DB1 and smoothed by the smoothing capacitor C6.
TH1 is the power thermistor which limits a rush current flowing to C6.
c. Invertor circuit
The DC voltage from the rectifying/smoothing circuit is supplied to the
secondary side of transformer T1 by switching operation of FET Q1.
For switching, the RCC (Ringing Choke Convertor) system is employed.
FET Q1 is turned on by the starting resistors R20 and R1 to generate a
voltage between terminals 4 and 6 of transformer T1 and between
terminals 2 and 3 simultaneously. Then a voltage is applied to the gate of
FET Q1 to oscillate high frequency.
The actual line in the circuit diagram shows the current to turn ON FET
Q1, and the dotted line shows the current loop through which the energy
accumulated in the transformer is discharged when FET Q1 is turned
OFF.
Voltage across Q1 drain and source (VDS)
Q1 drain current (ID)
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