HYBRID DIMMING CONTROL TECHNIQUES FOR LED DRIVERS

摘要

Techniques are disclosed for dimming LED strings using frequency modulation (FM) dimming and burst control dimming. At high brightness levels, FM dimming may be used to decrease the current through LED strings by increasing the switching frequency of pulses within a pulse train of an AC current source. At low brightness levels, or after the switching frequency has been increased to the resonant frequency of the current source, burst control dimming may decrease the current through LED strings by decreasing the duty cycle of the pulse train of the current source. At high brightness levels, FM dimming and burst control dimming may be combined by decreasing the duty cycle of the pulse train at each of a number of increasing switching frequency values. FM dimming may also be combined with frequency hopping in order to increase the number of available frequency steps.

主权项

1. A lighting driver circuit, comprising:
an AC current source driven by a pulse train having a duty cycle, the current source configured to output a current to at least one LED assembly; and a controller operatively coupled to the current source and configured to, in response to a dimming signal, perform frequency modulation dimming at high brightness levels wherein frequency modulation dimming comprises changing the frequency of pulses within the pulse train, and perform burst control dimming at low brightness levels wherein burst control dimming comprises changing the duty cycle of the pulse train.