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This 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 current is rectified by D101,D102,D103 and D104 and charges C106 to make DC voltage. Then it supplies power to the
converter circuit.

[Kick-on voltage circuit] 
Bias is applied to the Q101 gate via this circuit when the AC power is turned on and Q101 begins operating.

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The following is an overview of how the power supply unit is controlled. 
The control method of this power supply unit is pulse width modulation.

When Q

1

 is ON, the energy is charged in the transfer primary coil according to E

1

. When Q

1

 is OFF, the energy is output from the

secondary transfer as follows.
    L 

→ D

1

 

→ Load → L

Then the power is supplied to the Load. When Q

1

 is ON, power is not output from the secondary side. The output voltage is fed

back in the control IC according to the error amp rectifier. Then depending on how T

ON

 is controlled, stabilization occurs. Also,

when the current load becomes too large, in order to decrease the voltage output, the increase in 

 is controlled and the output

voltage is stabilized.
Therefore, basically the timing: Ton/Toff of Q1 controls the output voltage.

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[Surge Absorber Circuit] 
This circuit is for absorbing surge voltage generated by the transformer.

[Control Circuit and Detecting Circuit] 
The control circuit amplifies the output with increased voltage detected in the error detecting circuit. Then it drives the main transis-
tor.
In this power supply, the duty ratio is defined by changing the ON period of the main transistor.
This is shown as follows.
When the output voltage of the 24V circuit increases, the current of the photo coupler PC101 increases, the pulse width of the out-
put control IC becomes narrower and the ON period of Q101 becomes shorter.

[Over Current Limiter (O.C.L)]
The highest drain current (Q101) is limited by a limiter circuit (IC101) of 24V. The 24V output is limited by this circuit.

[Over Voltage Circuit]
If the 24V output increases because the error detecting circuit or control circuit is broken, IC101 will recognize this signal and output
becomes 0V.

Refer to Power Supply Board Section(P.110).

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• The paper stacker may not be shown in all illustrations