Operating in offline power supplies, STMicroelectronics’ L6591 PWM controller demonstrates optimization for zero-voltage switching asymmetrical half-bridge converters. The device enables efficiencies of 85% min. at 500 kHz, implements pulse skipping under light-load and no-load conditions, and has a quiescent current of <3 mA. The controller includes a PFC interface, compliance for the International Energy Authority’s 1 W plan for standby power, pulse-by-pulse over-current protection for false tripping, overload protection with latched or auto restart behavior, and transformer-saturation detection. The SO16N-packaged device implements adaptive UVLO. Pricing starts at $1.50 in 2,500 quantities.