External And Controls System; Power Supply; Protective Functions; Low-Voltage Power Supply Circuit - Canon LBP2900 series Service Manual

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2.6 EXTERNAL AND CONTROLS SYSTEM

2.6.1 Power Supply

2.6.1.1 Power Supply

2.6.1.1.1 Low-Voltage Power Supply Circuit

The low-voltage power supply circuit serves to convert the AC power from the power inlet into DC power for supply to various loads. The AC power is

supplied to the low-voltage power supply circuit on the power supply PCB when the power switch (SW101) is turned on. The AC power is then converted

by the printer unit into +24 V, which will then be converted into +5 V and +3.3 V in the engine controller.

The +24 V power is used to drive the main motor, scanner motor, and solenoids, while the +5 V power is used to drive the sensors and the ICs on the video

controller PCB.

The +24 V power turns to +24 V when it moves through the door switch (SW301) to reach the high-voltage power supply circuit. The +24 VU also serves

as the door open detection signal (DOSNS), enabling the CPU find out whether the door is open or not.

2.6.1.2 Protective Functions

2.6.1.2.1 Protective Mechanisms

The protective mechanisms include an overcurrent protective circuit that uses a fuse. If short circuit or the like occurs because of some fault and, as a result,

an overcurrent flows, the fuses will melt to cut off the power to the power supply circuit.

The power supply circuit is equipped with 2 fuses (Note; FU101, FU102); in the event an overcurrent flows into the AC line, either of these fuses will melt

to cut out the current. The power supply circuit also uses another fuse (FU501) to cut out the output voltage in response to an overcurrent in the DC line.

If the overcurrent protective circuit has gone on and DC voltage stops from the power supply circuit, turn off the power switch (SW101), correct the fault

in the load, replace the fuse, and turn the power switch back on.

The fuse FU102 is used only in the 110/127 V model.

Power switch

(SW101)

Inlet

(INL101)

Fuse

(FU101)

Fuse

(FU102)

110-127V only

Noise