Xerox WorkCentre Pro 412 Service Manual page 109

Circuit Description
5-10-2 AC Input Stage (WorkCentre Pro 412 & FaxCentre F12)
AC input power path is consist of the fuse (F501) for AC current limit, the Varistor (TNR501) for by-passing
high voltage surge, the discharge resistor(R508), the AC impulse noise filtering circuit (C501, LF501,
C503), the common mode grounding circuit (C504, C505), the second noise filter (LF502), and the ther-
mistor (TH501).
When power is turned on, TH 501 limits inrush current by it's high resistance, and when it's temperature
rises, it's resistance reduces to approximately zero ohms.
5-10-3 AC Input Stage (WorkCentre M15/M15i)
AC Input power path is consist of the Fuse (F1) for AC current limit, the Varistor (TNR1) for by-passing
high Voltage Surge, the discharge resistor(R1), the AC Impalse Noise Filtering Circuit (C2, C4, LF1), the
Common Mode Grounding Circuit (C5, C6), the 2'nd noise filter (C7, LF2), and the thermistor (TH1).
Wher power is turned on, TH 1 limits Inlush-Current by it's high resistanle, and When it's temperature rise,
it's resistance become about Zero ohm.
5-10-4 SMC (Switched Mode Control) (WorkCentre Pro 412 & FaxCentre F12)
The AC input voltage is rectified and filtered by BD552 and C507 to create the DC high voltage applied to
the primary winding of T501. TR01 pin #1 is driven by the SMPS device U502. U502. auto-starts and
chops the DC voltage. The U502 is PWM SMPS IC and has internally a SMC (switched mode control) IC
and a MOSFET output stage. The SMC IC has a Auto-restart without a Power Supply for the IC and a
Thermal Shutdown function and so on. C509, R512, C510, D505 clamp leading-edge voltage spikes
caused by transformer leakage inductance.
The power secondary winding (pin # 11-12) is rectified and filtered by D507, C552, L551, and C554 to cre-
ate the 5V output voltage. The bias winding (pin # 4-5) is rectified and filtered by D506 and C511 to create
U502 bias voltage. The secondary output 5V is regulated through the path of the voltage divide by R553,
R556-U503 switching PC252-the bias voltage of U502-U503 PWM duty cycle-T501 secondary voltage.
C508 filters internal pin, determines the auto-restart frequency, and together with R506, compensates the
control loop. U552 of the secondary stage -12V is the Low Power-loss Regulator with built-in over-current
protection function.
5-10-5 SMC (Switched Mode Control) (WorkCentre M15/M15i)
The AC input voltage is rectified and filtered by BD1 and C10 to create the DC high voltage applied to the
primary winding of T1, Q5 pin #1 is driven by the SMPS device IC2, IC2. auto-starts and chops the DC
voltage. The U502 is PWM SMPS IC and has internally a SMC(switched mode control) IC and a MOSFET
output stage. The SMC IC has a Auto-restart without a Power Supply for the IC and a Thermal Shutdown
function and so on. R4, R5, C11, D1 clamp leading-edge voltage spikes caused by transformer leakage
inductance.
The power secondary winding(Pin #5~6)is rectified and filtered by D8, D9, L2, C33, C34 to create the 5V
output voltage. The bias winding(Pin #9~8)is rectified and filltered by D2 and C12 to create U502 bias volt-
age. The secondary output 5V is regulated through the path of the voltage divide by R34, R35.
WorkCentre Pro 412, FaxCentre F12 & 3/03 5-71
WorkCentre M15/M15i