A Unity Power Factor Correction Preregulator With Fast Dynamic Response Based on a Low-Cost Microcontroller

Low cost passive Power Factor Correction (PFC) and Single-Stage PFC converters cannot draw a sinusoidal input current and are only suitable solutions to supply low power levels. PFC preregulators based on the use of a multiplier solve such drawbacks, but a second stage DC/DC converter is needed to obtain fast output voltage dynamics. The output voltage response of PFC preregulators can be improved by increasing the corner frequency of the output voltage feedback loop. The main drawback to obtaining a faster converter output response is the distortion of the input current. This paper describes a simple control strategy to obtain a sinusoidal input current. Based on the static analysis of output voltage ripple, a modified sinusoidal reference is created using a low cost microcontroller in order to obtain a input sinusoidal current. This reference replaces the traditional rectified sinusoidal input voltage reference in PFC preregulators with multiplier control. Using this circuitry, PFC preregulator topologies with galvanic isolation are suitable solutions to design a power supply with fast output voltage response (10 ms or 8.33 ms) and low line current distortion. Finally, theoretical and simulated results are validated using a 500 W prototype.

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