Control ICs hasten dimming capacity for CFLs

Compact fluorescent lamps (CFL) are literally quite cool, but one of their drawbacks is that they are difficult to dim. The IRS2530D and IRS2538D 600V ballast-control ICs from International Rectifier plan to modify that by offering easy to design-in, effective dimming for CFL ballast circuits. Dimming level for the IRS2530D is reduced to 10 percent of full intensity.

The IRS2530D is an eight-pin device (DIP and small outline IC), footprint that fits standard CFL driver ICs, which provide dimming capability using a few external components, including a sense resistor that monitors lamp current. On a single pin, it incorporates the DC dim-input voltage reference and the AC lamp-current feedback voltages, and then applies control algorithms to manage the dimming function. Other features are programmable preheat time, run frequency, protection against failure to strike, open filament, brownout protection and crest factor overcurrent protection.

For new applications, which are not constrained by the pinout of existing 8-pin control ICs, the IRS2158D is a 16-pin device that gives added functions including programmable preheat frequency, half-bridge closed-loop ignition current regulation, and deadtime control, brownout protection, end-of-life comparator, and other operating parameter and protection attributes. It enables control of dimming below 10 percent level.

- Bill Schweber
Planet Analog