Single stage AC-DC power converter with flyback PFC and improved THD

摘要

A single-stage AC-DC power converter for powering a load at a substantially constant current, and related methods and systems. The AC-DC power converter includes a high power factor correction (PFC) circuit configured in a flyback topology and operating in transition mode. The flyback PFC circuit has a PFC controller and is configured to draw an input AC current from an AC power supply. The input AC current has a first total harmonic distortion (THD). The flyback PFC circuit outputs a DC current to the load. The PFC controller is configured to sense a rectified input voltage. By multiplying the rectified input voltage sensed by the PFC controller, the input AC current drawn by the flyback PFC circuit has a second, much improved THD, which is achievable without the need of an expensive PFC controller. The rectified input voltage sensed by the PFC controller is multiplied using a Zener diode ladder.

主权项

1. A single stage AC-DC power converter for powering a load, comprising:
a buck power factor correction (PFC) circuit having a PFC controller, the buck PFC circuit configured to: draw an alternating current (AC) input current having a first total harmonic distortion (THD), sense a rectified input voltage from a full-wave rectifier via the PFC controller, output a direct current (DC) voltage and a DC current and supply constant current to the load; and a passive voltage multiplier circuit disposed between the full-wave rectifier and a sensed voltage input pin of the PFC controller, and configured to multiply the rectified input voltage to be sensed by the PFC controller, thereby causing the input AC current drawn by the buck PFC circuit to have a second THD lower than the first THD.