EL SEGUNDO, CA. January 1999 - International Rectifier (IR^®), the power expert, now offers a new 600V Resonant Mode Controller IC, designated the IR2157, specially designed to act as the core for a high frequency electronic ballast. Incorporating a versatile variable frequency oscillator with 600V half-bridge gate drive functions, the new IC also offers advanced features such as precision 50 percent duty cycle, programmable soft start and comprehensive protection modes.

The benefits for using IR2157 in the electronic ballasts include:

LONGER LAMP LIFE -- The IR2157 IC includes a programmable frequency and timing sequence for pre-heat, ignition and running mode. Matching timing characteristics of the startup sequence with lamp operating requirements puts less stress on the filaments, assures reliable striking and prolongs lamp life.

IMPROVED RELIABILITY AND SAFETY -- This includes comprehensive protection modes against failure to strike, filament failures, low DC bus, thermal overload and below resonance operation. Full protection improves reliability and safety against conditions such as end of life overloading, which could cause catastrophic damages.

LOWER MAINTENANCE COSTS -- Besides the full protection features which lower the chance for destructive failures, the IC allows automatic restart for lamp exchange, thus lowering the service time and cost.

LOWER COMPONENT COUNT AND MANUFACTURING COST -- Integration of 600V gate drivers and the programmable controller in one IC means that only a handful of passive components and two output FETs are needed to complete the entire ballast circuit. Heating or current transformers are not required, and only a current sensing resistor is used as a protection sensor.

While specially designed for electronic ballasts, the new IR2157 ICs are also appropriate for applications wherever soft switching resonant loads are involved, such as low noise power supplies, universal input AC-adapters and chargers.

A Reference Design Kit (IRPLLNR2) on how to implement an electronic ballast for a T8 tube is available to demonstrate the ease of design, low component count and full protection modes offered.