LED driver

摘要

An LED driver having an input to receive AC power from an AC power source, a semiconductor switch and an inductor controlled to produce a sinusoidal current drawn from the AC power source, and a large non-electrolytic (e.g. film) capacitor energy storage component. The semiconductor switch operates with a varying pulse-width-modulation frequency to regulate the voltage across the non-electrolytic capacitor energy storage component in such a way that a ripple current through the inductor is substantially smaller than a pulse-width-modulation cycle average current through the inductor. A DC-to-DC converter couples the energy from the non-electrolytic energy-storage capacitor to an LED string. A feedback loop allows the LED string to be regulated in either constant current mode or constant power mode and information for the feedback regulation is fed back across a high-voltage boundary using a low-cost signal transformer.

主权项

1. A light emitting diode (LED) driver comprising:
a first magnetic component configured to be coupled to an alternating current (AC) power source, wherein the first magnet component comprises an inductance; a first controllable semiconductor switch coupled to the inductance; a direct current (DC) bus coupled to the inductance and comprising a film capacitor; an LED load comprising a string of LEDs coupled to the DC bus; a non-regulated, isolated DC-to-DC converter that functions as a DC transformer and that is coupled to the DC bus and to the string of LEDs; and a first controller configured to control the first controllable semiconductor switch in such a way as to draw a sinusoidal current from the AC power source and such that the film capacitor absorbs pulsating power from the power source and provides DC power to the string of LEDs, wherein the film capacitor is sized such that a peak-to-peak AC ripple power in the LED load is greater than 20% of a steady-state power in the LED load, wherein a ratio of ripple voltage at a double AC-power-source frequency across the film capacitor to a DC voltage across the film capacitor is the same as a ratio of ripple voltage at a double AC-power-source frequency across the string of LEDs to a DC voltage across the string of LEDs.