Sharp AR-5012 Service Manual page 83

The control circuit is subject to negative feedback from the secondary
side as shown in fig (4). A photo coupler (PC002) is employed to insu-
late between the primary side and the secondary side to feed back the
control signal to the primary side.
When the output voltage is increased by energy transmission from
T001, the voltage detected by R109 and R111 is compared with the
reference voltage of IC102. When it exceeds the reference voltage, the
current flowing through IC102 (that is, the photo diode current of
PC002) is increased and transmitted to the primary side. Then the
potential at the feedback pin (2 pin) of IC102 is decreased to control
Q001. Therefore, the change in the output voltage on the secondary
side is passed through IC102 and PC002 to control Q001, stabilizing
the output voltage.
(4) Overcurrent protection circuit (Primary side)
The inverter circuit of the primary side is connected with the current
detection resistor R102. When an overcurrent occurs in the secondary
side, the current flowing through the primary side inverter Q001 is
increased. The current is detected by R012, and passed through R013
to IC701 overcurrent restricting pin (3 pin) to turn OFF Q002, shutting
off all power. To resupply the power, turn off and on the power. Refer
to fig (4).
(5) Rectifying/smoothing circuit (+5V)
fig (6) Rectifying/smoothing circuit
The high frequency pulse generated by the inverter circuit is
decreased by the converter transformer, rectified by the high frequency
diode D103, and smoothed by C103 and C104.
fig (7) +5V rectifying/smoothing circuit voltage waveform
Voltage waveform
Voltage waveform
AR-5012 ELECTRICAL SECTION 13 - 13