Toshiba D-VR3SU, Service Manual

Page: 102 / 217

Circuit Operating Descriptions
7-2
0
Vswitch
dt
Toff
t
Inverted power
by leakage
inductance
Fig. 7-2
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 Q1S01 because dt is a very short.
2) SNUBBER circuit protects Q1S01 from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to D1S05 and C1S08
and discharges to R1S02, R1S03).
3) C1S38 : For noise removal
(c) IC1S01 Vcc circuit
1) R1S05, R1S07, R1S08 : IC1S01 driving resistance (IC1S011 works through driving resistance at power cord in)
2) IS1S01 Vcc : R1S06, D1S07, C1S09
! Use the output of transformer as Vcc,because the current starts to flow into transformer while IC1S01 is
active
@ Rectify to D1S07 and smooth to C1S09.
# Use the output of transformer as IC1S01 Vcc : The loads are different before and after IC1S01 driving.
(Vcc of IC1S01 decreases below OFF voltage , using only the resistance dut to lode increase after IC1S01
driving.)
(d) Feedback Control Circuit
3.3V
L1S30
D1S30
C1S30
C1S37
L1S31 D1S33 PT1SD1
C1S31
C1S38
R1S35
R1S36
C1S39
R1S33
R1S32
R1S31
IC1S03
IC1S02
IC1S01
Fig. 7-3