Xerox WorkCentre M20 Service Manual page 174

Figure 5 Bias output unit block diagram
MHV (Electrification Output Enable)
Electrification Output Enable is the electrification output control signal 'PWM-LOW
ACTIVE'.When MHV-PWM LOW signal is received, Q401 turns on and the steady voltage will
be accepted to the non-inverting terminal of OP-AMP 324. As the voltage higher than the
inverting reference voltage of OP-AMP, which is set to R405 and R406, OP-AMP output turns
high. This output sends IB to the TRANS auxiliary wire through current-restricting resistance
Q402 via R408 and C403 and Q402 turns on. When the current is accepted to Q402, Ic
increases to the current proportional to time through the T401 primary coil, and when it
reaches the Hfe limit of Q402, 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 second-
ary unit, sends current to the load and outputs MHV voltage through the high voltage output
enable, which is comprised of Regulation circuit. Refer to Figure 6.
Figure 6 MHV signal
General Procedures and Information
GP 16
BIAS (Supply/Dev/Blade Output Unit)
BIAS (Electrification Output Enable) Electrification Output Enable is the electrification output
control signal 'PWM-LOW ACTIVE'.When BIAS-PWM LOW signal is received, Q501 turns on
and the steady voltage will be accepted to the non-inverting terminal of OP-AMP 324. As the
voltage higher than the inverting reference voltage of OP-AMP, which is set to R506 and R507,
OP-AMP output turns high. This output sends IB to the TRANS auxiliary wire through cur-
rent-restricting resistance Q502 via R509 and C504 and Q502 turns on. When the current is
accepted to Q502, Ic increases to the current proportional to time through the T201 primary
coil, and when it reaches the Hfe limit of Q502, it will not retain the "on" state, but will turn to
"off". As Q502 turns 'off', TRANS N1
energy to the secondary unit, sends current to the load and outputs DEV voltage through the
high voltage output enable, which is comprised of Regulation-circuit. Refer to Figure 7.
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 auxil-
iary wire through current-restricting resistance
Q204 will turn on. When the current is accepted to Q402, Ic increases to the current propor-
tional 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
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 Reg-
ulation– 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(-) out-
put unit is THV-EA 'L' enable.
March 2004
6-30
will have counter-electromotive force, discharge
Figure 7 Bias signal
R215 via R212 and C204, and eventually
Work Centre M20 Family
N1 will have