Panasonic KX-MB1520FX7, Service Manual

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KX-MB1520FX7/KX-MB1520FX8/KX-MB1520FXW/KX-MB1530FX7/KX-MB1530FXW
6.7.2. FB (Flat bed) motor drive circuit (KX-MB1520)
1. General
FB motor drive circuit consists of "Motor driver", "Motor current control circuit" and "O.C.P(Over Current Protection) circuit"
FB motor feeds CIS unit in FB scan, FB copy, and FB FAX mode (KX-MB1520 ONLY).
A one step rotation of this motor feeds CIS unit 0.021mm.
2. Block Diagram of Scanner motor Drive circuit
6.7.2.1. Motor driver
Motor driver IC502 can drive motor up to 0.8A/phase and support up to W1-2 phase excitation.
When "Power save" signal (IC502_pin20) becomes "H", motor driver is activated.
Stepping pulses are output from IC300 pins A9, B9, C9, A10, B10, and C10.
Frequency and pattern of these pulses determine the motor rotation speed and excitation mode respectively.
Corresponding to these pulses, current are supplied from IC502_pin4, pin6, pin7 and pin9 to each motor coil.
6.7.2.2. Motor current control circuit
1. Function
According to the scan speed, motor current is controlled for appropriate value.
For example, when scan speed is low, motor has enough driving force.
So to prevent the vibration and noise during motor rotation, motor drive current should be reduced.
When scan speed is high, motor needs much driving force. so much current should be supplied.
In order to control the motor current, Vref voltage of IC502 is controlled.
When Vref voltage is high, motor current is increased, and the voltage is low, motor current is reduced.
2. Circuit Diagram
Please refer to the circuit diagram shown in the block diagram of FB (Flat bed) motor drive circuit (KX-MB1520) (P.38).
3. Circuit explanation
For the sake of Vref voltage control, PWM pulse is supplied from IC300_pinD8.
PWM pulse is integrated by R538, R539 and C509, then converted to DC voltage.
This DC voltage is supplied to Vref pin of IC502.
When duty of PWM pulse is high, Vref voltage is increased and when duty is low, Vref voltage is decreased.