Kyocera FS-920 - Power Source, Engine;High Voltage, and Main PWBs

2GL/2FV/2FW
2-3-1
2-3 Operati on of the PWBs
2-3-1 Power source PWB
Figure 2-3-1 Power source PWB block diagram
The power source PWB consists of the switching regulator section that is the main part, other zero cross signal detection
circuit and heater lamp control circuit. The switching regulator circuit consists of the noise filter circuit, rectification smooth-
ing circuit, switching control circuit, 5 V DC rectification/smoothing output circuit, 24 V DC rectification/smoothing output
circuit and overvoltage detection circuit, and this circuit converts the AC power input to the 5 V DC and 24 V DC power
source by the switching operation and outputs it to the engine/high voltage PWB. The zero cross signal detection circuit
detects the 0 V point (zero cross) of the AC wave form and outputs to the engine/high voltage circuit, and the engine/ high
voltage PWB outputs the heater lamp ON signal (HEATN) to the heater lamp control circuit based on the timing of zero
cross signal (ZCROSS) and controls the AC power loading to the heater lamp.
D10 to 13
D31 D32
C8
F1
F2
SW1
NTC1
Q1
T1
Switching
control
circuit
24 V DC
rectification/
smoothing
output circuit
TRA1
Heater
lamp
Thermal
cutout
Heater
lamp
control
circuit
Power source PWB
PC1
PC5
PC2
Noise
filter
circuit
(L1)
Rectification
smoothing circuit
24V1
5V
GND
GND
HEATN
24V2
Power
switch
AC
input
Exit sensor
ZCROSS
SLEEP
5 V DC
rectification/
smoothing
output circuit
EXITN
PC3
Pulse
Overvoltage
detection
circuit
(IC101)
PC4
Zero cross
signal
detection
circuit