Dimming control method and apparatus for LED light source

摘要

A light emitting diode (LED) light source, LED driver circuitry and methods for controlling the brightness of an LED light source are presented. In some embodiments, an LED driver control circuit receives a dimming command signal to dim the LED light source, modulates a continuous direct current (DC) level to dim the LED light source, and determines that a predetermined threshold level has been reached. At this time, the process includes initiating a fixed pulse width generator (PWG) control signal having a fixed duty cycle, automatically adjusting the LED current amplitude to its nominal current level, and decreasing the current amplitude while the fixed PWG control signal is active to achieve commanded lower dimming of the LED light source.

主权项

1. A light emitting diode (LED) light source apparatus, comprising:
at least one LED: and a driver control circuit for controlling the brightness of the at least one LED, wherein the driver control circuit comprises:
a power circuit operable to receive input power and to generate a direct current to power the at least one LED;at least one of a comparator or an amplifier having a current sense signal input and a dimmed current reference command signal input, wherein the at least one of a comparator or an amplifier generates a control signal output that controls the power circuit to dim the at least one LED by decreasing the amplitude of LED current when the control signal is above a predetermined threshold;a fixed pulse width generator (PWG) having an output connected to the power circuit, wherein the fixed PWG is configured to operate with a predetermined fixed duty cycle; anda comparator circuit having a predetermined threshold signal input and a dimming command signal input, wherein when the dimming command signal is above the predetermined threshold the comparator circuit disables the fixed PWG to dim the at least one LED, and wherein the comparator circuit enables the fixed PWG when the dimming command signal decreases below the predetermined threshold level resulting in the power converter circuit being controlled On-Off with the predetermined fixed duty cycle, and wherein the current amplitude level is automatically adjusted in response to the dimming command signal and the activation of the PWG in order to further dim the at least one LED.