Xerox WorkCentre Pro 412 Service Manual page 58

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Circuit Description
5-5-7-6. THV(THV(+)/THV(-) Output Unit)
Transfer(+) output unit is the transfer output control signal 'PWM-LOW ACTIVE'.
When THV-PWM LOW signal is received, Q203 turns on and the steady voltage will be accepted to the non-
inverting terminal of OP-AMP 324. As the voltage is higher than the inverting reference voltage of OP-AMP,
OP-AMP output turns high.
The 24V power adjusts the electric potential to ZD201 and ZD202, sends IB to TRANS auxiliary wire through
current-restricting resistance R215 via R212 and C204, and eventually Q204 will turn on. When the current is
accepted to Q402, Ic increases to the current proportional to time through the T201 primary coil, and when it
reaches the Hfe limit of Q204, it will not retain the "on" state, but will turn to "off". As Q402 turns 'off', TRANS
N1 will have counter-electromotive force, discharge energy to the secondary coil, sends current to the load
and outputs THV voltage through the high voltage output enable, which is comprised of Regulation– circuit.
The output voltage is determined by the DUTY width. Q203 switches with PWM DUTY cycle to fluctuate the
output by fluctuating the OP-AMP non-inverting end VREF electric potential, and the
maximum is output at 0% and the minimum, at 100%.Transfer(-) output unit is THV-EA 'L' enable.
When THV-EA is 'L', Q302 turns on and the VCE electric potential of Q302 will be formed and sends IB to
TRANS auxiliary wire through R311, C305 and VR302 via current-restricting resistance R314, and eventually
Q303 will turn on. When the current is accepted to Q303, Q303's Ic increases to the current proportional to
time through the T301 primary coil, and when it reaches the Hfe limit of Q303, it will not retain the "on" state,
but will turn to "off". As Q303 turns 'off', TRANS N1 will have counter-electromotive force, discharge energy to
the secondary coil, send current to load and output THV(-) voltage through the high voltage output enable,
which is comprised of Regulation circuit.
5V
18V
R201
10K
U2
U2
1
2
3
#7
TEV-PWM
R206
R205
100
1.8K
Q203
A708Y
R207
24VS
2K
+ C101
35V47
F
U
#17
5V
#19
5V
5
6
#5
TEV-EA
U2
7
7407
D-GND
8
#24
TEV-READ
5-32
D201
1N4148
R208
30K
R209
100KF
C201
C202
D202
R210
R211
103
121
1N4148
VR201
845KF
1MF
50K
D301
1N4148
24VS
C4
103
10
+
U1
R302
R303
9
R304
_
33K
100KF
389KF
KA324
C302
C303
D302
R305
102
103
1N4148
R301
10KF
470K
VR301
5K
C301
222
August 2001
24VS
5
+
7
R213
U1
2.2K
_
6
Q204
D526
11 KA324
C204
R212
C203
D203
ZD201
ZD202
R214
333Z
680K
472
1N4148
5.65V
705V
2.2K
18V
R312
R309
1W56
202K
Q301
A708Y
R307
R313
33K
1W56
18V
R310
Q303
2.2K
D526
Q302
A708Y
R308
33K
VR302
2K
R306
C305
R314
R311
26.1KF
333Z
1.7K
100KF
C304
500V103Z
T201
C206
C208
KAB-007
6KV470pF
6KV
1
7
C205
D204
D205
2KV68pF
6KV
6KV
6
5
C207
3KV470pF
2
R216
R218
SBR306
MGR1/2W100KF
4
R217
R215
SBR207
390
KAB-006
C307
D304
T301
3KW470pF
4KV
1
6
D303
C306
C308
4KV
2KV68pF
3KV470pF
5
7
2
4
WorkCentre Pro 412
Launch Issue
D206
D207
6KV
6KV
C209
6KV
R315
SBR306

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