Two-stage LED driver with buck PFC and improved THD

摘要

A two-stage light emitting diode (LED) driver for powering an LED load at a substantially constant current, and related methods and systems. The first or front end stage of the LED driver includes a buck topology power factor correction (PFC) circuit, the buck PFC circuit and a PFC controller. The second stage of the LED driver includes a conventional isolation and regulator circuit configured to receive the DC voltage and DC current output by the buck PFC and then to provide the substantially constant current to the LED load. By multiplying the rectified input voltage sensed by the PFC controller, the input AC current drawn by the buck PFC circuit has a much improved total harmonic distortion (THD), which is achievable without the need for using an expensive PFC controller. The rectified input voltage is multiplied using a Zener diode ladder.

主权项

1. A light emitting diode (LED) driver for powering an LED load at a substantially constant current, comprising:
a buck power factor correction (PFC) circuit, having a PFC controller, the buck PFC circuit configured to (i) draw an alternating current (AC) input current having a first total harmonic distortion (THD), (ii) sense a rectified input voltage from a full-wave rectifier at the PFC controller, and (iii) output a direct current (DC) voltage and a DC current; a passive voltage multiplier circuit (i) disposed between the full-wave rectifier and an input of the PFC controller, and (ii) configured to multiply the sensed rectified input voltage by a whole number greater than 1, the drawn AC current having a second THD different from the first THD; and a downstream isolation and regulator circuit configured to (i) receive the DC voltage and the DC current output by the buck PFC circuit, based on the drawn AC current, and (ii) selectively switch, by a switch thereof, the DC current between different values based on a status position of the switch, to provide the substantially constant current of a desired value to the LED load.