Samsung SV-DVD50 Service Manual page 105

(2) Circuit description (FLY-Back PWM (Pulse Width Modulation control)
(a) AC Power Rectification/Smoothing Terminal
1) D1SS01, D1SS02, D1SS03, D1SS04 : Convert AC power to DC(Wave rectification).
2) C1SS10 : Smooth the voltage converted to DC.
3) L1SS01, L1SS02, C1SS01, C1SD02 : Noise removal at power input/output.
4) R1SS01 : Rush current limit resistance at the moment of power cord insertion.
- Without R1SS01, the bridge diode might be damaged as the rush current increases.
(b) SNUBBER Circuit : R1SD11, R1SD13, C1SD12, C1SD16, D1SS11
Vswitch
dt
0
Toff
(c) IC1SS2 Vcc circuit
1) R1SR01, R1SR02, R1SR03 : IC1SS2 driving resistance
2) IC1SF01 Vcc : R1SS08, D1SF02, C1SF02
ΠUse the output of transformer as Vcc, because the current starts to flow into transformer while IC1SS2 is
active.
´ Rectify to D1SF02 and smooth to C1SF02.
ˇ Use the output of transformer as IC1SS2 Vcc : The loads are different before and after IC1SS2 driving.
(Vcc of IC1SS2 decreases below OFF voltage, using only the resistrance due to load increase after IC1SS2
driving.)
Inverted power
by leakage
inductance
Fig. 7-7
(IC1SS2 works through driving resistance at power cord in)
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 SCS11A because dt is a very short.
2) SNUBBER circuit protects SCS11A from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to D1SS11 and C1SD12
and discharges to R1SD11 and R1SD13).
t
3) C1SS16 : For noise removal
Circuit Operating Descriptions
7-3