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9. Technical Board Information
Description
PFC board is main for shaping the AC input line current waveform to correspond to that of the AC input line voltage, and boost input
rectified voltage to 380V DC for preregulator, it consist of EMI filter, rectifier, boost converter, dual driver, V DC monitor and PFC
controller.
Line voltage can directly input from 90V AC to 264V AC and boost to 380V DC for the output, there are differential choke L1, L3,
common choke FL2, and CX2, CX3 capacitors to form a EMI filter that can reduce noise and interference, then fed through retifier
CR1 to filter capacitor C810.
The PFC boost converter operated at average mode control and using new zero-current-zero-voltage switched (ZC-ZVS) active
snubber circuit that includes snubber inductor L802, clamp diode D802, clamp capacitor C803, C804, main switch Q801 and auxiliary
switch Q802. ZC-ZVS techniques can reduce the reverse-recovery-related losses of rectifier and also provides soft switching of main
switch (Q801) turns off with ZCS, whereas the auxiliary switch (Q802) turns on with ZVS, it is noticed that Q802 is turned on after
Q801 being turned on, and both of them are using IGBT. This application is shown to be significantly improved the conversion
efficiency especially at low line operation.
The output of the PFC controller IC321 is fed into dual driver IC322 and IC323, the same phase of output from IC322 and IC323
are together drive to main switch Q801. The signal after delayed is in series with IC322 and IC323 then fed to drive auxiliary switch
Q802. The power supply +15V for IC321 comes from standby and through regulator IC20.
IC321 provides all the function necessary for active power factor corrected preregulator, such as voltage error amplifier (pin 7 & 11),
multiplier (pins 5, 6, 7 & 8), current amplifier (pin 3, 4 & 5), oscillator (pin 12 & 14), power limit (pin 2) and OVP (pin 10, under 1.9V
DC is active), reference voltage (7.5V DC at pin 9) and pin 16 for the output.
When over current or short circuit occurs at 380V DC output, minus voltage drop accross R811 an R812 will be detected, and trigger
pin 2 of IC321 to stop PFC operation immediately. If over voltage happens at 380V DC output, voltage at pin 10 of IC321 will be
increase at the same time, IC327 is triggered, Q322 and Q357 turn on and operate as a SCR latched, so voltage at pin 10 of IC321
is clamped to ground to stop PFC operation.
IC325/326 act as protection to stop PFC operation while low line voltage is detected. It will force pin 10 below 1.9V DC voltage,
trigger IC321 to OVP and stop PFC operation immediately.
Pin assignment Connectors on Board
J2
J57
J61
J60
J59
J58
J55
J56
J2 (nc)
1 ++15V StdBy
2 GND P*
J59
1 380V
2 nc
3 GND P*
Image 9-3
Pin assignment connectors on board
48
J57 (nc)
J61
1 380V
1 380V
2 nc
2 nc
3 GND P*
3 GND P*
J58
J55
1 380V
1 380V
2 nc
2 nc
3 GND P*
3 GND P*
4 ++15V StdBy
J60
J5
1 380V
1/2 Mains (L)
2 nc
3 nc
3 GND P*
4/5 Mains (N)
J56 (nc)
J101
1 380V
1 Power Switch
2 nc
2 Power Switch
3 GND P*
* Primary ground
R5976766 RLM G5 22/04/2004
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