Service manual

5.2 Operating Principle Of The Major Functional Block
5.2.1 AC/DC converter (PFC)
The purpose of AC/DC converter is to generate a stable bipolar DC BUS for inverter, another very
important task of AC/DC converter is to make the input current track input voltage waveform
therefore achieve a high input power factor close to 1, performing PFC (Power Factor Correction),
That is why we also call the AC/DC converter PFC converter.
Figure 5.2.1.1 showed the topology implement the PFC converter.
Figure 5.2.1.1 PFC converter
The PFC converter comprise several sub-circuit, the first one is the modified BOOST power
topology, the second one is the driving circuit, the third one is the PFC controller, which can
further divided into signal sensor, feedback circuit and the actuator.
When AC mains is in normal condition, after receive the turn on command, the global controller
turns on the AC relay and enables PFC converter work, the PFC controller outputs PWM (Pulse
Width Modulation) signal, the PWM signal will be isolated, amplified and use to drive switching
component, the IGBT. When The IGBT is turned on, the current flow through the PFC chock
increase, the chock is energized, when the IGBT is turned off, the chock de-energize and charge
the DC-BUS capacitor. By controlling the Duty Cycle of the PWM signal, the energy charging the
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