A single-phase active-clamped (AC) push-pull resonant power factor correction (PFC) converter is a type of power electronic circuit used to improve the power factor of an AC input while efficiently converting the input voltage to a regulated DC output voltage. This converter combines features of both active-clamp and resonant converter topologies to achieve these goals.
Here's how the operation of a single-phase active-clamped push-pull resonant PFC converter typically works:
Input AC Voltage:
The converter is connected to an AC input voltage source. This AC voltage is typically rectified and smoothed before being fed into the converter.
Input Filtering:
A filter is usually employed to smooth out the rectified AC voltage and reduce the high-frequency components. This helps in reducing harmonics and achieving better power factor correction.
Push-Pull Topology:
The core of the converter is the push-pull topology. This consists of two switches (usually MOSFETs) that are operated in a complementary manner. These switches alternate turning on and off to control the flow of current through the primary winding of a transformer.
Active Clamp:
An active clamp circuit is used to regulate the voltage spikes that occur when the switches turn off. This clamp circuit typically consists of a switch and a snubber capacitor. When the main switches turn off, the active clamp switch turns on, providing a low-impedance path for the energy stored in the leakage inductance of the transformer. This reduces the voltage stress on the main switches and improves their efficiency.
Resonant Operation:
The converter operates in a resonant mode, meaning that the switching of the main switches is synchronized with the resonant frequency of the circuit. This is typically achieved using a resonant tank circuit (consisting of a resonant capacitor and resonant inductor) connected to the primary side of the transformer. Resonant operation reduces switching losses and improves efficiency.
Phase-Shift Control:
Phase-shift control is often employed to regulate the output voltage. By adjusting the phase shift between the switching of the two main switches, the duty cycle and hence the output voltage can be controlled.
Power Factor Correction:
The resonant operation of the converter, combined with the control of the active clamp, results in reduced switching losses and improved power factor correction. The converter draws current from the AC source in a sinusoidal manner, which helps to align the current waveform with the voltage waveform and reduce distortion.
Output Rectification and Filtering:
The output of the transformer is rectified and filtered to obtain a stable DC voltage that can be used to power various loads.
The single-phase active-clamped push-pull resonant PFC converter offers advantages such as improved power factor correction, reduced switching losses, and efficient energy conversion. However, it also involves complex control and requires careful design to optimize its performance for a specific application.