Panasonic KX MC6020 - Color Laser - All-in-One Service Manual page 63

6.7.4. Optional Lower Input Tray Motor (OPF Motor) Drive Circuit
General
Optional Lower Input Tray (Option) motor drive circuit consists of motor current control circuit as well as Scanner motor.
6.7.4.1. Motor Current Control Circuit
1. Circuit explanation
According to the print speed, each motor current is controlled for appropriate value.
When print speed is low, motor current is decreased to prevent the vibration during motor rotation.
When print 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 drive is controlled.
When Vref voltage is high, motor current is increased, and the voltage is low, motor current is decreased.
In order to control of Vref voltage, PWM pulse is supplied from IC300 pin AN31.
PWM pulse is inverted by Q601 and integrated by R617, R618, and C601, then convert to DC voltage.
This DC voltage is supplied to Vref pin of each motor drive through Q603.
When duty of PWM pulse is high, Vref voltage is decreased and when duty is low, Vref voltage is increased.
When print speed is high (21ppm), this motor current is controlled approx. 0.50A.
When print speed is low (8ppm), this motor current is controlled approx. 0.40A.
2. Circuit diagram
63
KX-MC6020HX