[4] Circuit description of power supply PWB
1. Block diagram | F1 |
T1.25A/250V
AC IN
F2
T1.25A/250V
Noise
Filter
Circuit
Rectifying
Smoothing
Circuit
Switching
Circuit
(RCC system)
Regulater +5V Circuit
+24V F3
4A/72V
2-1. Noise filter circuit
The input noise filter section is composed of L and C, which reduces normal mode noise from the AC line and common mode noise to the AC line.
2-2. Rectifying/smoothing circuit
The AC input voltage is rectified by diode D1, 2, 3, 4 and smoothed by capacitor C5 to supply DC voltage to the switching circuit section.
Power thermistor TH1 suppresses inrush current at power
Photo Coupler
Fig. 7
The overcurrent protection is performed by bringing Q1 to OFF state through detection of voltage increase in the auxiliary winding of T1 by ZD2 and R9.
The overvoltage protection is performed by operating the overcurrent protection circuit through destruction of zener diode ZD4 and short- circuiting of load.
2-4. +5V circuit
Each DC voltage supplied by rectifying the output of transformer T1 with diode D8 is stabilized by
2-3. Switching circuit
This circuit employs the self excited ringing choke convertor (RCC) sys- tem. In this system, the DC voltage supplied from the rectifying/smooth- ing section is converted into high frequency pulses by ON/OFF repeti- tion of MOS FET Q1.
Energy is charged in the primary winding of T1 during ON period of Q1, and discharged to the secondary winding during OFF period.
The output voltage is controlled by adjusting ON period of Q1 which changes charge time of C9 through operation of
VTH output is supplied through the relay RY1. Relay RY1 is operated by
[5] Circuit description of CIS unit
1. CIS
Cis is an image sensor which puts the original paper in close contact with the
It is composed of sensor, rod lens, LED light source,
Due to the
2. Waveforms
The following clock is supplied from FC200 of the control board, and VO is output.
5ms
øT | Approx.5V |
| |
| 0V |
| 2∝s |
CISCLK |
|
VO | 2V(TYP) |
| (White original paper) |
Fig. 8
5 – 11
