Dimmer decoder with low duty cycle handling for use with LED drivers

摘要

A method includes receiving a sense signal having multiple pulses, where the sense signal is based on an output of a dimmer. The method also includes, for each of multiple sampling periods, (i) identifying a pulse duty cycle by sampling at least one pulse in the sense signal and calculating a duty cycle of the at least one pulse and (ii) generating an output value identifying a duty cycle for driving one or more LEDs. The output value is based on the pulse duty cycle. The method further includes generating a holding current for the dimmer (i) during the sampling of the at least one pulse in at least one of the sampling periods and (ii) when the pulse duty cycle is less than a specified threshold. The holding current can be applied continuously when the pulse duty cycle is less than the specified threshold (such as 15%).

主权项

1. A method adaptable for controlling illumination in an LED lighting system with multiple LEDs and a phase cut dimmer, comprising:
receiving a dimmer sense signal with a dimmer duty cycle based on a dimmer phase angle; generating an LED drive signal with an LED duty cycle for driving an LED current to the LEDs, the LED duty cycle based on the dimmer duty cycle; and generating a holding current for the dimmer when the dimmer duty cycle is less than a specified threshold, including:
generating a current sense signal corresponding to the LED current;generating a reference current corresponding to a minimum current through the dimmer; andgenerating the holding current based on a difference between the LED current and the reference current;such that a current through the dimmer corresponds to the reference current.