Sony TRIMASTER EL BVM-E171 Service Manual page 95

Block diagram
VCC voltage
Q6110
Q6111
Primary switch
circuit
PFC power supply
Supplies to the
main power supply
As shown above, the VCC voltage supply switch circuit usually performs power-on operation when the SUB5V voltage
is output and supplies the VCC voltage to the PFC power and main power circuits.
PFC Power
The PFC power circuit boosts the PFC voltage to 395 V to meet the harmonic regulation.
PFC power output
PFC voltage
Power supply method
Current critical-type boost chopper power
Components
• PFC power IC (IC6300)
• PFC choke (L6301)
• Switching FET (Q6300)
• Rectifier diode (D6304)
• Smoothing capacitor (C6324: block chemicon)
Setting output voltages
PFC voltage: 395 V
Overvoltage protection
This circuit compares the voltage obtained by sensing the PFC voltage by dividing resistors with the reference voltage
generated by IC6103 and detects overvoltage state of the PFC voltage to shut down the POWER ON circuit and stop
the main power circuit (setting voltage: approx. 450 V).
Overcurrent protection
An overcurrent flowing in the switching FET is detected by the source current limiting resistors (R6314, R6315), and
is then input to the IS pin of the PFC power IC to stop switching operation. Inactivation of the PFC power circuit lowers
the PFC voltage. When the PFC voltage reaches 320 V, the main power circuit stops operating.
Description of circuit
The PFC power circuit employs a current critical-type boost chopper system.
When a VCC voltage is supplied from the SUB power circuit to the PFC power IC, the switching FET is turned on and
a current starts flowing through the primary winding of the PFC choke and the switching FET. This current increases
at a gradient of Vin (rms)/L (inductance value of L = L6301 primary winding: 240 μH). This current is converted to a
voltage by the source current detection resistors (R6314, R6315). When the voltage reaches the value set by the PFC
BVM-E171
Photo coupler
PH6103
Q6114
Secondary
SUB5V voltage
switch circuit
7-3