Low-voltage power supply circuit Opening the feeder cover switch cuts power to the ADF scanning lamp, pickup motor, delivery motor, and the solenoids. The power supply unit generates dc power required in the scan engine based on the ac voltage supplied from the print engine power supply. The remote switch is employed as a power switch of the scan engine. Of the voltages supplied from the print engine dc controller to the power supply of the scan engine, 3.3 vdc are used as a remote signal. The signal is supplied to the power supply unit as the power remote signal (SPON) through the intermediate circuit.
When the signal is “H,” the low-voltage power supply circuit generates the ac power to the dc power. The power generated in the circuit is converted to +24 vdc, +15 vdc, +5 vdc, and +3.3 vdc required in the scan engine. The +24 vdc is supplied to the motors, solenoids, and scanning lamps; +15 vdc to the sensors, LEDs, and ICs in the SCB; and +3.3 vdc to the CPB. The +24 vdc is divided into the +24 vb and +24 va. The +24 va is constantly supplied from the low- voltage power supply circuit, and the +24 va stops power supply when the feeder cover switch (JMCSW) is turned off by opening the ADF feeder cover.
The +24 va is supplied to the scanning lamps, pickup motors, delivery motors, and solenoids. It also functions as the ADF FEEDER COVER OPEN DETECTION signal, and allows the CPU to detect an open cover. Figure 45. Low-voltage power supply circuit 78 Chapter 5 Theory of operation C8523-90921