Psu (Low Voltage Power Supply Board) Section - Panasonic KX MC6020 - Color Laser - All-in-One Service Manual

KX-MC6020HX

6.19. PSU (Low Voltage Power Supply Board) Section

The low voltage power supply board circuit generates +7V and +24Vdc.
It also supplies AC voltage to the halogen heat lamp in the fuser unit.
The low voltage power supply board uses the switching regulator method.
[Input Circuit]
The input current goes into the input rectifier circuit through the filter circuit.
The filter circuit decreases the noise voltage and the noise electric field strength.
[Rectifier Circuit]
The input circuit is rectified by D001 and charge C016 to make DC voltage.
Then it supplies power to the converter circuit.
[Kick-on Voltage Circuit]
Bias is applied to the Q001 gate via this circuit when the AC power is turned on and Q001 begins operating.
[Control Circuit and Error Detecting Circuit 1]
The control circuit detects the voltage that increased in an error detect circuit 1 and controls it to become the predetermined out-
put voltage.
This is shown as follows.
When the output voltage of the 7V circuit increases, the current of the photo coupler PC001 increases, the pulse width of the
output control IC becomes narrower and the ON period of Q001 becomes shorter.
[Over Current Limiter (O.C.L)]
The highest drain current of Q001 is limited by a limit current circuit. The 7V and 24V output is limited by this circuit.
[Over Voltage Circuit (O.V.L) and Error Detecting Circuit 2]
The control circuit detects the voltage that the 24V or 7V output increased in an error detect circuit 2 and controls it to becomes
0V.
Dummy load method (to quickly check the power supply output)
Refer to PSU (Low Voltage Power Supply Board) Section (P.296).
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