Panasonic UF-585 Service Manual page 211

ETXDN200A4D (115V)
Input Circuit
AC line voltage travels to the rectifying circuit through the line filter. The line filter eliminates RFI noise which may otherwise pass
to the AC line from the power supply unit. It also protects the power supply unit from transient noise which may pass into the unit
from the AC line.
Rectifying Circuit
AC power is rectified by D101 and charges C105 to make high DC voltage, then supply power to converter circuit.
Kick-on voltage for control IC (IC101) is supplied AC power through R103 and R110.
Inrush current is limited by TH101.
Converter Circuit
A hybrid IC (IC101), in combination with transformer T1, form a switching power supply circuit using the RCC (Ringing Choke
Converter) system.
As soon as power is applied to the Power Supply Unit, AC line voltage is rectified by D101 and is smoothed by capacitor C105.
The protection circuit at the time of start-up is controlled by an IC (IC101) and resistors R103 and R110.
Ei
Q101
Main Switching Circuit
In the above circuit, when the main switching transistor, Q101, is turned On, input voltage, Ei, is supplied to the primary win ding of
transformer T101. However, no current will flow through diode D201 of the secondary side, due to reverse polarity of the
secondary winding causing no current flow within T1. But the transformer charges with energy. When Q101 is turned Off,
the supply voltage to the primary winding shuts off and the windings of T101 change polarity, allowing D201 to conduct, releasing
the energy accumulated in T101 to the circuit. When the energy is discharged through D201, Q101 turns on, once again
reversing the polarity on T101 windings, creating a self-oscillation circuit.
T101
P
S
B
Control Circuit
P --- Primary Winding
S --- Secondary Winding
B --- Control Winding
D203
Eo
+
System Description
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