Canon CLC1000 Service Manual page 126

3. Controlling the Grid Bias
Figure 3-523 shows the circuit that controls the grid bias, and the circuit has the following functions:
1. Controls the voltage.
2. Detects overcurrent.
The grid bias is controlled by the grid bias control signal (HVGR) as follows:
An output voltage suited to voltage of HVGR is generated by the transformer.
The changes in the grid bias generated to suit the grid bias
control signal (HVG) are as shown in Figure 3-522.
The output of the grid bias is monitored with reference to its voltage, and the data is fed back to the
current control circuit. The feedback signal is used to ensure a specific level of grid bias. If an overcurrent
is detected, because of leakage for example, the OC signal will turn on CM, thereby forcing off the pulse
output. When such occurs, the grid bias will remain off for 20 ms and then will return automatically.
A soecific voltaae is aoolied to the grid.
DC controller PCB
Voltage
d e t e c t i o n clrcult
Figure 3-523
CANON CLClOOO REV.1 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
12v
Figure 3-522
Potential
Environment sensor
Current Grid
control circuit
Grid
bias
sensor
3-99