Toshiba D-VR3SU Service Manual page 102

Circuit Operating Descriptions
Vswitch
dt
0
(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
7-2
Inverted power
by leakage
inductance
Toff
Fig. 7-2
PT1SD1
IC1S01
IC1S02
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
t
and discharges to R1S02, R1S03).
3) C1S38 : For noise removal
D1S30
C1S30
D1S33
C1S31
R1S31
R1S32
R1S33
IC1S03
Fig. 7-3
3.3V
L1S30
C1S37
L1S31
C1S38
R1S35
C1S39
R1S36