Panasonic KX-MB1500UCW / KX-MB1520UCB Service Manual ▷ View online
37
KX-MB1500UCW/KX-MB1520UCB
2. Flat torque 1-2 phase excitation (Half speed)
(1) Timing chart
(1) Timing chart
(2) Wave form
38
KX-MB1500UCW/KX-MB1520UCB
6.7.2.
FB (Flat bed) motor drive circuit
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.
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 motors 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.
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.
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 (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 C764, 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.
PWM pulse is integrated by R538, R539 and C764, 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.
39
KX-MB1500UCW/KX-MB1520UCB
4. Timing chart of current control
Following timing charts are the example of Vref voltage corresponding to PWM pulse duty.
6.7.2.3.
O.C.P (Over Current Protection) circuit
1. Function
If motor driver can supply more than 15 watts, FB motors may become fire hazards.
To prevent the risk of fire, this circuit is provided.
To prevent the risk of fire, this circuit is provided.
2. Circuit Diagram
3. Circuit explanation
When the current supplied from 24V exceeds 0.44A, the voltage between two registers R575 and R578 becomes more than
0.6V (=0.44A*2.7ohm/2), consequently both Q515 and Q522 turn on.
If Q522 turns on, IC502_pin20 becomes "Low" level.
As a result IC502 is deactivated and motor currents are cut off.
So the current which IC502 can supply is limited to less than 0.44A and the wattage is also limited to less than 10.7W
(=0.44A*24V).
By limiting the wattage less than 15W, risk of fire hazard is eliminated.
0.6V (=0.44A*2.7ohm/2), consequently both Q515 and Q522 turn on.
If Q522 turns on, IC502_pin20 becomes "Low" level.
As a result IC502 is deactivated and motor currents are cut off.
So the current which IC502 can supply is limited to less than 0.44A and the wattage is also limited to less than 10.7W
(=0.44A*24V).
By limiting the wattage less than 15W, risk of fire hazard is eliminated.
40
KX-MB1500UCW/KX-MB1520UCB
6.8.
Timing chart and wave form of scanner motors
6.8.1.
Drive mode of FB motor
Correspondent table of operation
Click on the first or last page to see other KX-MB1500UCW / KX-MB1520UCB service manuals if exist.