A single-phase active-clamped (AC) push-pull boost power factor correction (PFC) converter is a type of power electronic circuit used to improve the power factor and efficiency of an AC-to-DC conversion process. It is commonly used in applications such as switch-mode power supplies (SMPS) for electronic devices.
Here's a description of how a single-phase active-clamped push-pull boost PFC converter operates:
Input Stage (AC Input):
The converter is connected to an AC input source, typically from the mains power supply. The AC voltage is rectified to DC using a diode bridge rectifier, resulting in a pulsating DC voltage. This pulsating DC voltage has a relatively low power factor and may contain harmonics, which can lead to inefficient power utilization and increased losses in the system.
Boost Stage (Push-Pull Converter):
The main objective of the PFC converter is to shape the input current waveform to closely follow the input voltage waveform, thus achieving a higher power factor. The boost stage consists of a push-pull converter topology, which is essentially a transformer-based circuit. It comprises two switches (typically MOSFETs) and a center-tapped transformer.
Switching Operation: The two switches are operated in a push-pull manner. When one switch is turned on, the other is turned off, and vice versa. This generates an alternating voltage across the primary winding of the transformer.
Transformer Action: The alternating voltage induces a voltage in the secondary winding of the transformer. This voltage is rectified and filtered to produce a high-voltage DC output.
Active Clamping: The "active-clamping" feature involves an additional switch and a capacitor in parallel with the primary winding of the transformer. This configuration allows for clamping the voltage across the primary winding to a safe level, preventing voltage spikes that could damage the switches and other components.
Control Strategy:
A control circuit is employed to regulate the operation of the switches in the boost stage. This control strategy aims to achieve a power factor close to unity by adjusting the duty cycle of the switches according to the instantaneous AC input voltage. A feedback loop monitors the input current and adjusts the switching frequency and duty cycle to maintain the desired power factor.
Output Stage:
The boosted and rectified DC voltage from the boost stage is then passed through a filter (typically an LC filter) to further smooth out the voltage waveform and reduce ripple. The filtered DC voltage is used to supply the load, which could be a DC bus for various applications.
In summary, a single-phase active-clamped push-pull boost PFC converter improves the power factor and efficiency of an AC-to-DC conversion process by shaping the input current waveform to closely follow the input voltage waveform. The active-clamping feature helps to control voltage spikes and protect the switches. The control strategy ensures that the converter operates with a high power factor, contributing to improved energy utilization and reduced harmonic distortion in the AC input current.