Constant voltage dimmable LED driver
OwnerGang Gary Liuinventor
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Abstract
A constant voltage dimmable LED (Light Emitting Diode) driver is disclosed that is compatible with all types of dimmers, including conventional phase cut (TRIAC) dimmers, and behaves like a conventional constant voltage driver which can be connected to any size of LED load that has a matching voltage rating. The driver produces a continuous train of pulses for driving the LED load and obtains an averaged measure of the voltage at the AC input for controlling the duty cycle of the continuous train of pulses. Therefore, when the averaged measure of the voltage at the AC input is reduced by a dimmer, the duty cycle reduces, resulting in a dimmed LED. The driver can be created by adding a few components to a conventional wide input range AC-DC converter without or with very little modifications.
Claims16
A circuit for adapting an AC input to drive a load comprising:
- a) a measuring circuit for obtaining an averaged measure of the voltage at the AC input;
- b) a power converting module, comprising an AC-DC converter and a switch for turning on and off a current path between the AC-DC converter and the load, for converting the AC input into a continuous train of pulses for driving the load, with a duty cycle controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit, wherein the switch for turning on and off the current path between the AC-DC converter and the load is controlled by a pulse width modulator oscillating at a substantially fixed frequency above human's flickering perception threshold and having a pulse width controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.
A method for adapting an AC input to drive a load comprising:
- a) obtaining an averaged measure of the voltage at the AC input;
- b) using a power converting module comprising an AC-DC converter and a switch for turning on and off a current path between the AC-DC converter and the load to convert the AC input into a continuous train of pulses for driving the load, with a duty cycle controlled by the averaged measure of the voltage at the AC input, wherein the switch for turning on and off the current path between the AC-DC converter and the load is controlled by a pulse width modulator oscillating at a substantially fixed frequency above human's flickering perception threshold and having a pulse width controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.
Dependencies are inferred from the claim text.