Many brands identify faults in the PFC (Power Factor Correction) circuit through error codes that indicate issues with the PFC circuit or the associated IGBT transistor.
Location and Operation of the PFC Circuit
Location of the PFC Circuit
The PFC circuit is located on the external electronic board, immediately after the diode bridge or rectifier.
Operation of the Circuit
The PFC circuit operates with a continuous voltage input that is higher than the board’s supply voltage. For instance, if the board is powered with 220 V AC, the PFC circuit receives approximately 300 V DC.
Essential Components of the PFC Circuit
Key Elements
The PFC circuit includes:
- An electronic controller that monitors the IGBT transistor
- A power inductor or reactor
- A fast diode
- A capacitor to stabilize the output voltage
IGBT Transistor Control
The controller activates the IGBT transistor through its gate pin. For example, if a 5 V signal is applied to the gate, the transistor activates, allowing communication between its other two pins and functioning as a switch.
Voltage Stabilization Process
Voltage Spikes Generation
When the inductor receives current and is then abruptly deactivated, a reactive voltage spike is generated. The controller activates the IGBT transistor to allow current flow through the inductor and then deactivates it after a few milliseconds, creating a voltage spike higher than the original.
Voltage Stabilization
These voltage spikes are stabilized by the capacitor, which provides a steady voltage. Additionally, a diode at the output prevents current from returning from the capacitor.
Diagnosis and Testing of the PFC Circuit
Input Voltage Measurement
To diagnose the PFC circuit, measure the input voltage after rectification using a multimeter set to DC and an appropriate range, such as 300 V for a 220 V AC supply.
Continuity Test of the Inductor
With the system disconnected, measure the electrical continuity of the inductor using the multimeter’s continuity function.
IGBT Pulse Verification
With the system powered on, check if the IGBT transistor is receiving pulses from the PFC circuit controller.
IGBT Transistor Testing
As a power component, the IGBT transistor can be damaged. To test it outside the board, locate its serial number, consult the datasheet to identify its pins, and follow the recommended testing procedure.
Diode Testing
To test a diode, measure the voltage drop when it is forward-biased. In this condition, the diode acts as a closed switch, allowing current flow.
