Fan Motor Section - Panasonic KX-MB2061CXB Service Manual

KX-MB2061CXB/KX-MB2061CX2/KX-MB2062CXB

6.11. FAN Motor Section

6.11.1. General
This unit is equipped with two FAN motors to prevent the developing devices, Power Supply Unit (PSU) and other devices from
overheating during printing.
The FAN rotates at high speed (Approx. 3000rpm) while printing.
After printing is finished, FAN rotates at low speed (Approx.2200rpm) while predetermined period.
6.11.2. Circuit Diagram of FAN
Two FAN motors are controlled by following one circuit.
So the operation of two FAN motors (Full speed rotation/Half speed rotation/Stop) are controlled simultaneously.
6.11.3. Fan Control
For the control of FAN speed, comparator IC (IC504) is used.
This IC compares (+) side input level and (-) side input level.
If (+) side input level is bigger than (-) side input level, output of this IC is "OPEN".
If (+) side input level is less than (-) side input level, it outputs "L" level.
6.11.3.1. Half Speed Mode
In half speed mode, IC300_pinA11 outputs pulse (frequency is about 30KHz, duty is about 37.5%).
This pulse is integrated by R30 and C502 then Pin2_IC504 becomes approx. DC1.24V. Input level of IC504_pin2 is determined by
the voltage of between R507.
If voltage between R507 is less than 1.24V, output of pin1_IC504 becomes "H".
Then both Q512 and Q510 are turned on. So voltage between R504 (=the voltage of pin2_IC504) rises gradually.
When the voltage between R507 exceeds 1.24V, output of pin1_IC504 becomes "L".
Then both Q512 and Q510 are turned off. So voltage between R507 falls gradually.
By repeating these sequences, voltage between R507 is controlled approx. 1.24V.
On the other hand, if FAN voltage is represented Vo and voltage between R507 is represented VL, VL is determined as below for-
mula.
VL=Vo*R507/(R505+R507) → Vo=VL*(R505+R507)/R507
Since each value is as follows, Vo is determined approx. 9.7(V).
VL=1.24(V), R505=150(Kohm), R507=22(Kohm)
Vo=1.24*(150K+22K)/22K=9.7(V)
Therefore by reducing the voltage of FAN power supply, FAN rotates with half speed.
6.11.3.2. Full Speed Mode
In full speed mode, IC300_pinA11 outputs constant 3.3V.
When both Q512 and Q510 are turned on, Vo becomes 24V.
So the voltage between R507 is determined as follows
VL=Vo*R507/(R505+R507)=24*22K/(150K+22K)=3.07(V)
Since IC504_pinA3 is 3.3V and IC504_pinA2 is 3.07V, pin1_IC504 is always "H".
Consequently both Q512 and Q510 are always turned on, and then 24V is supplied to FAN motors.
Therefore FAN rotates with full speed.
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