High-Voltage Power Supply; Generation Of Primary Corona High Voltage; Generation Of Transfer Corona High Voltage - Canon LBP-CX Series Service Manual

B. High-Voltage Power Supply
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High-voltage power supply
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Figure 3-59 High-voltage control circuit
1. Outline
The high-voltage power supply· generates high
voltage for the primary corona, transfer corona, and
developing bias according to commands from micro-
computer IC208. The high-voltage power supply pre-
vents the circuit from being damaged by a short cir-
cuit in the high-voltage output, and stabilizes corona
discharge current in different environments.
2. Operation
Generation of primary corona high voltage
The high-voltage primary corona generator cir-
cuit transmits a pulse from the variable frequency
oscillator circuit to flyback transformer 1 via flyback
transformer driver 1, and generates primary corona
high voltage, which is then applied to tlie primary
corona. The high-voltage primary corona generator
circuit applies a feedback signal proportional to the
corona discharge current which flows in the primary
corona assembly to the frequency control circuit in
order to stabilize corona discharge current.
The frequency control circuit compares the
feedback signal with the reference voltage (which
equals the voltage of the feedback signal when
the correct corona discharge current flows in the
primary corona assembly). If there is a difference
in voltage, the frequency control circuit changes
the pulse frequency of the variable frequency oscil-
lator circuit to eliminate the difference.
The high-voltage primary corona generator
circuit contains a short-circuit protection circuit to
prevent the circuit from being damaged by a short
circuit in primary corona high-voltage output. When
detecting high-voltage short circuits the short-circuit
protection circuit switches off the power to flyback
transformer driver 1 using the power switch circuit.
Generation of transfer corona high voltage
The high-voltage transfer corona generator circuit
applies pulses from the variable frequency oscillator
circuit in the high-voltage primary corona generator
circuit to inverter transformer 3 via inverter trans-
former drive 2, and generates transfer corona high
voltage. The transfer corona high voltage is added to
the bias high voltage which is -generated by flyback
transformer 1, and lower than the starting voltage of
transfer corona discharge. The addition method
COPYRIGHT
©
BY CANDI INC. CANON LBP·CX SERIES REY.2 JULY 1985 PRINTED IN JAPAN (IMPRIME AU JAPONI
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