Toshiba 28YT56, Service Manual

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2.2.4 SMPS BLOCK
2.2.4.1 PRIMARY BLOCK
AC power applied via AC inlet, line filter components prevent chassis from incoming noise of AC line,
also prevents AC line against created noises by TV. Bridge rectifier and bulk capacitor converts AC
voltage to DC voltage. Applied DC voltage to primary winding is then swicthed via MOSFET by primary
controller in a controlled manner.
SMPS controller works on quasi-resonant PWM and gets first supply voltage from AC line (SMPS
Controller supply). Controller drives MOSFET according to feedback information supplied by
shunt regulator and opto-coupler, according to that information adjusts on-time of MOSFET for
required power. After the start-up in normal operation mode SMPS controller is supplied by SMT.
Primary block consist of following main parts,
AC Inlet (PL800),
Fuse (F800),
Varistor (R800 and R802),
Line Filter For EMC (C801,L800,C802),
SMPS Controller (IC804),
SMPS Controller supply for first Start-up and at Stand-by (D823, C800, D801, R801),
Bridge Rectifier (D800),
Rectifier For SMPS Controller(D802),
PFC Coil Socket (PL801),
PFC Coil Dumping Cap (C807),
Bulk Cap (C810),
Clamping Circuitry (R810, C814, C815, D816),
SMT (Switch Mode Transformer) (TR800),
SMT Driver MOSFET (Q802),
Current Sense Resistors (R814, 815,R816, R819),
Protection Components for MOSFET Failure (D805, D806, R813),