Charge Corona Circuit - Ricoh Robin Service Manual

24 June 1994

2.3 CHARGE CORONA CIRCUIT

CC Trig [ 24]
Grid Trig (PWM) [ 0→0/5]
GND [0]
Main Board (PCB 1)
The main board supplies +24 volts to the CC/Grid/Bias power pack at CN1-1
as the power supply source. After the Start key is pressed the CPU drops
CN1-3 from +24 volts to 0 volts. This energizes the charge corona circuit
within the CC/Grid/Bias power pack, which applies a high negative voltage of
approximately –7.0 K volts to the charge corona wires. The corona wires then
generate a negative corona charge.
The grid plate limits the charge voltage to ensure that the charge does not
fluctuate and that an even charge is applied to the drum surface.
The grid trigger pulse applied to CN1-5 is a pulse width modulated signal
(PWM signal). This signal is not only a trigger signal, it also changes the
voltage level of the grid. As the width of the pulse applied increases, the
voltage of the grid also increases.
CN1-1
CN119-7
VA [24]
CN119-6 CN1-2
VC [5]
CN1-3
CN119-5
CN119-3 CN1-5
CN119-1 CN1-7
t2
2-5
C
Power Pack -
CC/Grid/Bias
G
(P1)
B
PWM Duty cycle
t1
=t2/t1 x 100 (%)
DRUM CHARGE
Charge Corona
Grid
Development
Bias