Kyocera KM-2020

2C9
2-3-1
2-3-1 Power source PCB
Figure 2-3-1 Power source PCB block diagram
The power source PCB (PSPCB) is a switching regulator that converts an AC input to generate 24 V DC and 5 V DC. It
includes a rectifier circuit, a switching regulator circuit, a 24 V DC output circuit, a 5 V DC output circuit, overvoltage
detection circuit, zero-cross circuit and a fixing heater control circuit.
The rectifier circuit full-wave rectifies the AC input using the diode bridge D005. The smoothing capacitor (C008) smoothes
out the pulsed current from the diode bridge.
In the switching control circuit, PWM controller (IC001) turns the power MOSFET (Q006) on and off to switch the voltage
induced in the primary coil of the transformer (T001).
The 5 V DC output circuit rectifies and smoothes the voltage induced in the secondary coil of the transformer (T001) via
diodes (D206) and smoothing capacitors (C204), and the output is controlled by the overvoltage detection circuit (IC201).
For 5 V DC output, the PWM controller IC (IC001) of the switching control circuit changes the duty of the switching pulse
width of the power MOSFET (Q006) via a photo coupler (PC001) based on the output voltage status to adjust the 5 V DC
output.
The 24 V DC output circuit rectifies and smoothes the voltage induced in the secondary coil of the transformer (T001) via
diodes (D201) and smoothing capacitors (C102), and the output is controlled by the overvoltage detection circuit (IC201).
The zero-cross circuit detects zero-crossing of the AC input voltage with the AC detection circuit and outputs the zero-cross
signal (ZCROSS) from the zero-cross output circuit through the photo coupler (PC002).
The fixing heater control circuit is divided into the sub-heater output (SH. OUT) and the main heater output (MH. OUT).
When the control signals (S. HEATN and M. HEATN) input from the machine engine side show a low level, this circuit turns
on the sub-heater and the main heater respectively by turning on the photo triac couplers (PC004 and PC005) with a zero-
cross circuit to turn on the triacs (TR001 and TR002) in the fixing heater ON/OFF circuit.
The power-saving control circuit performs power-saving control by turning off the 24 V DC output in the 24 V DC output ON/
OFF switching circuit and controlling the switching control circuit and the AC detection circuit through the photo coupler
(PC003) to decrease the switching frequency, stop the starting circuit in the switching control circuit, and stop the AC
detection circuit when the sleep signal (SLEPN) input from the machine engine side is low.
In addition, 5 V DC three-terminal Reg is connected to the back of the 24 V DC output ON/OFF switching circuit to output +5
V1, and this output stops when the sleep signal (SLEPN) is low.
IL001
FG
DH1.LIVE
DH2.LIVE
DH1.OUT
DH2.OUT
SH.OUT
Ficing heater
ON/OFF circuit
MH.OUT
AC
INPUT
(TR001,TR002)
Fixing heater
control circuit
Zero-cross circuit
Rectifier circuit
Energy save control circuit
PC001
D101
D005
T001
L004L003F002
F001
F003
SW001
C102
F201
C008
C204
Q006
D206
PC002
PC004
PC005
PC003
AC
detection
circuit
Zero-cross
output circuit
ON/OFF
switch circuit
+24V
GND
GND
+5V
+5V1
ZCROSS
S.HEATN
M.HEATN
SLEPN
Switching
control circuit
(IC001)
Overvoltage
detection circuit
DC5V
output
circuit
DC5V
3 terminal
regulator
DC24V
output
circuit
(IC201)
(IC301)