DIMMING REGULATOR INCLUDING PROGRAMMABLE HYSTERETIC DOWN-CONVERTER FOR INCREASING DIMMING RESOLUTION OF SOLID STATE LIGHTING LOADS

摘要

A system providing deep dimming of a solid state lighting (SSL) load includes a hysteretic down-converter, a shunt switch, a controller and a comparator. The down-converter controls average current value and amplitude of ripple of SSL current using amplitude modulation (AM) dimming control. The shunt switch controls magnitude of the SSL current using pulse width modulation (PWM) dimming control. The controller generates first and second PWM signals for controlling upper and lower current levels at which the down-converter operates based on the SSL current and voltage across the SSL load, and generates a third PWM signal for controlling the shunt switch based on a dimming level load set by a dimmer. The comparator circuit compares first and second analog signals corresponding to the first and second PWM signals with the SSL current, and drives the down-converter in response to the comparison. The SSL current is based on both the AM dimming control and the PWM dimming control.