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4.3
Active PFC Stage
4.3.1
Boost chopper
The active PFC circuit is a simple boost chopper type. It can control to aim ideal input
current to follow the incoming main supply voltage waveform. A special module
"FPAB30BH60" has full-bridge rectifier, IGBT, gate driver and fast recovering diode. It is
used as core component of the PFC circuit. The input voltage range of the module is
90V~265VAC. The IGBT can tolerant with 600VAC-30A. For more information, please refer
to datasheet of "FPAB30BH60".
To make up a boost chopper circuit, the user is required to add an external choke through
existing connectors. The recommended specification of choke is 2~4 mH / 15A.
4.3.2
PFC feedback circuit
There are four feedback signals. These are required to implement digital PFC function.
They are:
Rectified input voltage
DC bus voltage
Rectified input current
Rectified input voltage zero-crossing event
The rectified input voltage comes from the voltage divider that consists of R12, R13 and R16.
The range of voltage is 0~4.0V when AC mains input range is from 90VAC to 265VAC.
There is RC filter, made of R14 and C7, between some resisters and ADC pin.
D3, diode, can limit to 5V as a maximum voltage .
As the rectified input voltage, the DC bus voltage comes from some resisters.
It consists of R2, R3 and R8. DC bus voltage passes through the filter that is made of R4
and C2.
D1, diode, can limit to 5V as a maximum voltage.
Rectified input current is measured using the shunt resistor R17 and the amplifier U4C unit.
The gain of amplifier is set at 5.
Rectified input voltage zero-crossing event is sensed using a voltage divider (R21, R22) and
an opt-coupler (U3).
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AN706-00042-1v0-E
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