Mita PointSource Ai 3010, Руководство по обслуживанию

Страница: 82 / 478

2AR
2-3-2
The power source PCB (PSPCB) is a switching regulator which converts an AC input to
generate 24 V DC, 5 V DC, 3.3 V DC and 12 V DC. It consists of a noise filter circuit,
rectifier circuit, switching control circuit, 24 V DC output circuit, 5 V DC output circuit, 3.3
V DC output circuit, 12 V DC output circuit and fixing heater control circuit.
The noise filter circuit, which consists mainly of the line filters L1 and L2 and capacitors,
attenuates external noise, and prevents the switching noise generated on the power
source PCB from leaving the machine via the AC line.
The rectifier circuit full-wave rectifies the AC input which has passed through the noise
filter circuit using the diode bridge DB1. The smoothing capacitor C6 smoothes out the
pulsed voltage from the diode bridge.
The switching control circuit turns on/off the power MOSFET Q1 and Q2 via the PWM
controller IC1 to switch the current induced in the secondary coil of the transformer T1.
The 24 V DC output circuit smoothes out the voltage from the current induced in the
secondary coil of the transformer T1 via diode D30 and smoothing capacitors C30, C32,
C36, C40 and C48, and outputs a stable 24 V DC by the function of shunt regulator
IC30. The output status of the 24 V DC is fed back to the PWM controller IC1 in the
switching control circuit via the photo-coupler PC1. Based on the feedback, the PWM
controller IC1 changes the duty cycle of the pulse that turns power MOSFET Q1 and Q2
on/off in order to adjust the 24 V DC output.
The 5 V DC output circuit converts the 24 V DC from the 24 V DC output circuit to a
stable 5 V DC by means of the 4-pin regulator IC40.
The 3.3 V DC output circuit converts the 5 V DC from the 5 V DC output circuit to a
stable 3.3 V DC by means of the 4-pin regulator IC41.
The 12 V DC output circuit smoothes out the voltage from the current induced in the
secondary coil of the transformer T1 via diodes D50 and D51 and smoothing capacitor
C53, and generates a stable 12 V DC by the function of the 4-pin regulator IC51.
The fixing heater control circuit is controlled by the fixing heater M light signal H1 REM
from the engine PCB (EPCB). The phototriac PC20 turns on when this signal goes low.
When phototriac PC20 turns on, it will turn the triac TRC20 on (continuity present),
which then passes AC current. The fixing heater M (H1) then turns on. The sub fixing
heater control circuit is controlled by the fixing heater S light signal H2 REM. Its
components include phototriac PC21 and triac TRC21.