Canon Vizcam 1000, Руководство по обслуживанию

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COPYRIGHT © 2001 CANON INC. CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3-99
3. OPERATION AND TIMING
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:
Input in the range of HVGR=0V to 12V
An output voltage suited to voltage of HVGR is generated by the transformer.
A specific voltage is applied to the grid.
The changes in the grid bias generated to suit
the grid bias control signal (HVG) are as shown in
Figure 3-522.
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 Q1, thereby forcing off the pulse output.
When such occurs, the grid bias will remain off for 20 ms and then will return automatically.
Figure 3-523
(Correction is executed each time the Start key is pressed based on
HVGR data from the enviroment sensor and the potential control.)
0V
11V
12V
-950V -200V
HVGR
Grid bias
HVT2-1
DC controller PCB
HVGR
24V
Grid bias
Grid
Q1
Pulse oscillator circuit
24V
Voltage
detection circuit
Overcurrent
detection circuit
Current
control circuit
Transformer
Potential sensor
Environment sensor
OC