News and New Products

Green chips control white light

By Joshua Israelsohn -- EDN, 9/2/2004

Two new ICs from International Rectifier simplify lighting-control designs and increase lamp efficiency. The IR2520D forms the core of a robust, adaptive lighting ballast design for CFLs (compact fluorescent lamps). The chip reduces a ballast’s component count by 20%, increases its reliability over traditional electronic ballast designs, and compensates for lamp characteristics that vary due to temperature and aging (Picture).

The 2520 operates on rectified line voltage and provides gate drive for a 600V half-bridge, which powers the lamp through a simple resonant LC network. The ballast-control IC is self-starting and guards against open-filament and lamp-strike failures that can destroy components in traditional electronic-ballast designs. An on-chip crest-factor measurement circuit monitors the half-bridge output current using the low-side switch’s on-resistance as the sense resistor. Excessive current over a measurement interval causes the chip to lock out the gate-drive outputs until a user cycles the power to the chip.

IR’s adaptive ballast IC requires 20% fewer parts than conventional electronic CFL ballasts. The 2520 needs neither a transformer nor a PTC thermistor, resulting in a smaller ballast design that dissipates less heat than those based on many competing controllers. The 57-cent (100,000) IR2520D is available in DIP-8 and SO-8 packages.

For halogen lamps, International Rectifier’s IR2161 adapts to variations in operating frequency, supply voltage, and lamp conditions. It protects against overloads, short circuits, and excessive operating temperature and maintains compatibility with standard triac dimmers.

Like the 2520, the 2161 forms the center of a lamp-control circuit with 20% fewer external components than conventional designs. It trades the commonly used bipolar half-bridge output for a MOSFET pair and eliminates the need for matched output devices. Prices for the controller in DIP-8 or SO-8 packages start at 73 cents (100,000).

To jump-start your lighting-control design, International Rectifier also offers reference designs, demo boards, white papers, and design software, which runs on PC platforms. The program generates schematics, bills of material, and layouts for selected lamp types and input voltage ranges.

International Rectifier, www.irf.com.