Samsung DVD-C700 Service Manual page 52

5-1-2 Circuit description (FLY-Back PWM (Plise Width Modulation) Control)
5-1-2 (a) AC Power Rectification/Smoothing Terminal
1) PD01,PD02,PD03,PD04 : Convert AC power to DC(Wave rectification)
2) PE3 : Smooth the voltage converted to DC(Refer to VIN of Fig. 5-7)
3) PC01, PC02, PC10, PC11, PC12, PC13, PL01, PL02, PL03 : Noise removal at power input/output
4) PVA1 : SMPS protection at power surge input (PVA1 pattern open is to remove noise)
5) PR10 : Rush current limit resistance at the moment of power cord insertion.
ΠRush current = (AC input voltage x 1.414 - Diode drop voltage) / Pattern resistance + PL02,01 resis-
´ Without PR10, the bridge diode might be damaged as the rush current increases.
5-1-2 (b) SNUBBER Circuit : PR15, PR16, PC04, PC05, PD11, PR17
Vswitch
dt
0
Toff
5-1-2 (c) PIC1 Vcc circuit
1) PR11, PR12, PR13, PR14 : PIC1 driving resistance (PIC1 works through driving resistance at power cord in)
2) PIC1 Vcc : PR18, PD12, PE6
ΠUse the output of transformer as Vcc, because the current starts to flow into transformer while PIC1 is active.
´ Rectify to PD12 and smooth to PE6.
ˇ Use the output of transformer as PIC1 Vcc : The loads are different before and after PIC1 driving.
(Vcc of PIC1 decreases below OFF voltage, using only the resistance due to load increase after PIC1 driving.)
Samsung Electronics
tance + PC10 resistance + PR10) (AC230V based : approx. 26A)
Inverted power
by leakage
inductance
Fig. 5-7
1) Prevent residual high voltage at the terminals of
switch during switch off/Suppress noise.
High inverted power occurs at switch (PIC1) off,
because of the 1st winding of transformer :
(V= LI xdi/dt. LI : Leakage Induction)
A very high residual voltage exists on both terminals
of PIC1 because dt is a very short.
2) SNUBBER circuit protects PIC1 from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to PD11 and PC04, and
discharges to PR15 and PR16).
t
3) PC05, PR17 : For noise removal
Circuit Descriptions
5-3