Samsung DVD-R129, Service Manual, Page: 116 / 208

Circuit Operating Descriptions
13-2 Samsung Electronics
0
Vswitch
dt
Toff
t
Inverted power
by leakage
inductance
Fig. 13-2
(b) SNUBBER Circuit :
PSRZ1, PSRZ2, PSCX1, PSCZ2, PSDZ1
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=-L1 xdi/dt. L1 : Leakage Induction)
A very high residual voltage exist on both terminals
of PQIZ1 because dt is a very short.
2) SNUBBER circuit protects PQIZ1 from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to PSDZ1 and PSCX1
and discharges to PSRZ1, PSRZ2).
3) PSCZ2 : For noise removal
(c) PQIZ1 Vcc circuit
1) PQIZ1 Vcc : PVRL4, PVDL1, PVCL1
!
Use the output of transformer as Vcc,because the current starts to flow into transformer while PQIZ1 is
active
@
Rectify to PVDL1 and smooth to PVCL1.
#
Use the output of transformer as PQIZ1 Vcc : The loads are different before and after PQIZ1 driving.
(Vcc of PQIZ1 decreases below OFF voltage , using only the resistance dut to lode increase after PQIZ1
driving.)
(d) Feedback Control Circuit
ICE3B2065P
TRANS(PQTZ1) PPDF1
PPLF1
PFRF5
PFRF3
PFID1
PBIZ1
PFRF1
PFRF2
PFRF6
PFCF1
PFRF4
PPCF3 PPC1
5.8V
Fig. 13-3