Samsung DVD-611, Service Manual

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Circuit Descriptions
Samsung Electronics 5-3
5-1-2 Circuit description (FLY-Back PWM (Plise Width Modulation) Control)
5-1-2 (a) AC Power Rectification/Smoothing Terminal
1) PDS01,PDS02,PDS03,PDS04 : Convert AC power to DC(Wave rectification)
2) PEF10 : Smooth the voltage converted to DC(Refer to VIN of Fig. 5-7)
3) PLF01, PLS01, PCF01, PCF02, PCD01, PCD03, PCS03 : 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 resi PLF01, PLS01
resi PCD01 resi PRF10) (AC230V based : approx. 26A)
´
Without PRF10, the bridge diode might be damaged as the rush current increases.
5-1-2 (b) SNUBBER Circuit : PRS11, PRS12, PRD12, PCD12, PDS11, PCF11
0
Vswitch
dt
Toff
t
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 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 PICF1 because dt is a very short.
2) SNUBBER circuit protects PICF1 from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to PDS11 and PCF11,
and discharges to PRS11 and PRS12).
3) PCD12, PRD12 : For noise removal
5-1-2 (c) PICF1 Vcc circuit
1) PCD11, PCF12, PCF13, PCF14 : PICF1 driving resistance
(PICF1 works through driving resistance at power cord in)
2) PICF1 Vcc : PDF13, PRF16, PEF12
ΠUse the output of transformer as Vcc, because the current starts to flow into transformer while
PICF1 is active.
´
Rectify to PDF13 and smooth to PEF12.
ˇ Use the output of transformer as PICF1 Vcc : The loads are different before and after PICF1 driving.
(Vcc of PICF1 decreases below OFF voltage, using only the resistance due to load increase after PICF1 driving.)