Panasonic KX-MB283BR Service Manual page 26

KX-MB283BR
6.5.2. SCANNER MOTOR DRIVE CIRCUIT
General
Scanner motor drive circuit is consist of motor current control circuit ,FB (Flat Bed) motor driver and ADF (Auto Document Feeder:
equipped model only) motor driver .
6.5.2.1. MOTOR CURRENT CONTROL CIRCUIT
1. Circuit explanation
According to the scan speed, each motor current is controlled for appropriate value.
When scan speed is low, motor current is reduced to prevent the vibration during motor rotation.
When scan speed is high, motor needs much driving force. so much current should be supplied.
For the control of motor current, Vref voltage of each motor driver is controlled.
When Vref voltage is high, motor current is increased, and the voltage is low, motor current is reduced.
In order to control Vref voltage, PWM pulse is supplied from IC300 pin D8 .
PWM pulse is inverted by Q521 and integrated by R533, R534, and C567, then convert to DC voltage.
This DC voltage is supplied to Vref pin of each motor driver through Q522.
When duty of PWM pulse is high, Vref voltage is decreased and when duty is low, Vref voltage is increased.
For FB motor, motor current is controlled approx. 0.1A-0.25A.
For ADF motor, motor current is controlled approx. 0.2A-0.35A (ADF epuipped model only).
2. Circuit diagram
3. Timing chart
Following timing charts are the example when PWM pulse duty are approx 9% and 45%.
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