Power Supply Board Section - Panasonic KX-MB2230JT Service Manual

6.19. Power Supply Board Section

The power supply board circuit generates 24Vdc and 12Vdc at normal mode.
It also supplies AC voltage to the halogen heat lamp in the fuser unit.
The power supply board uses the switching regulator method, and it has a power save function.
[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 D10 and charge C5 to make DC voltage.
Then it supplies power to the converter circuit.
[Kick-on Voltage Circuit]
Bias is applied to the Q1 gate via this circuit when the AC power is turned on and Q1 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 24V circuit or 12V circuit increases, the current of the photo coupler PC1 increases, the pulse
width of the output control IC becomes narrower and the ON period of Q1 becomes shorter.
[Power Saving Function]
Output voltage is changed by PWRDWN signal.
[Over Current Protection (O.C.P)]
The highest drain current of Q1 is limited by a over current circuit. The 24V or 12V output is limited by this circuit.
[Over Voltage Protection (O.V.P)/ Error Detecting Circuit 2]
If the 24V or 12V output increases because the error detecting circuit 1 or control circuit is broken, control circuit will recognize
this signal and output becomes 0V.
Dummy load method (to quickly check the power supply output).
Refer to Power Supply Board Section (P.95).
Condition PWRDWN
Normal Open
Power Save Low (0V)
KX-MB2230JT/ KX-MB2270JT/ KX-MB2515JT/ KX-MB2545JT/ KX-MB2575JT/ DP-MB310JT
24Vout 12Vout
24V 12V
12-20V 7V
95