Power Source Pcb - Kyocera KM-2530 Service Manual

2-3-1 Power source PCB

F1
AC input
F2
Fixing heater
control circuit
HEATER
TRA1
MAIN ON
HEATER
TRA2
SUB ON
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 and a fixing heater
control circuit.
The rectifier circuit full-wave rectifies the AC input using the diode bridge D3. The smoothing capacitor C5 smoothes out the
pulsed current from the diode bridge.
In the switching control circuit, PWM controller IC1 turns the power MOSFET Q1 on and off to switch the current induced in
the primary coil of the transformer T1.
The 24 V DC output circuit smoothes the current induced in the secondary coil of the transformer T1 via diodes D101 and
D102 and smoothing capacitors C101 and C102, and the output is controlled by the overvoltage detection circuit IC201 and
the power MOSFET Q201. For 24 V DC output, the PWM controller IC (IC1) of the switching control circuit changes the duty
of the switching pulse width of the power MOSFET Q1 via a photo coupler PC4 based on the output voltage status to adjust
the 24 V DC output.
The 5 V DC output circuit smoothes the current induced in the secondary coil of the transformer T1 via diodes D101 and
D102 and smoothing capacitors C101 and C102, and the output is controlled by the overvoltage detection circuit IC201 and
the power MOSFET Q201. For 5 V DC output, the PWM controller IC (IC1) of the switching control circuit changes the duty
of the switching pulse width of the power MOSFET Q1 via a photo coupler PC5 based on the output voltage status to adjust
the 5 V DC output.
The overvoltage detection circuit IC201 monitors the overvoltage status of 24 V DC and 5 V DC, and when it detects an
abnormal status, it gives immediately feedback to the PWM controller IC (IC1) via a photocoupler PC5 to stop control
operation and moves the power source to a standby condition.
The fixing heater control circuit sends a waveform of which zero-cross is detected to the main PCB (MPCB), which controls
the timing of HEATER REM 1 and 2 based on it to turn on the phototriacs PC1 and PC2. When the phototriacs PC1 and PC2
turn on, AC current flows through the triacs TRA1 and TRA2 to turn the fixing heaters M and S on.
Rectifier circuit
D3
+
C5
Zero-cross
circuit
PC3
Switching
control circuit
IC1
PC1
PC2
Figure 2-3-1 Power source PCB block diagram
Power source PCB
T1
D101
D102
+
C102
Q1
PC4
PC5
C101
+
24 V DC
output
circuit
5 V DC
+
output
C201
circuit
Overvoltage
detection circuit
IC201
2DF
24 V DC
GND
5 V DC
GND
ZERO CROSS
OUT
HEATER
REM1
HEATER
REM2
2-3-1