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STMicroelectronics introduce the L6591 PWM controller

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article image The L6591 PWM controller

The L6591 PWM controller, available from ST Microelectronics , is an integrated controller optimised for zero-voltage switching asymmetrical half-bridge converters, which enable lower-cost power supplies, delivering high efficiency from standby to full load, reducing heat and power loss.

For use in offline power supplies, the L6591 PWM controller implements the functional blocks required to control a soft-switching half-bridge converter. Zero-voltage switching eliminates turn-on switching losses, minimises EMI emissions and enables efficient operation at up to 500kHz. This allows small external filter components for compact overall dimensions. In addition, the L6591 PWM controller implements pulse skipping under light-load and no-load conditions and has a quiescent current lower than 3mA. These properties allow designers to meet the growing demands of customers to minimise power dissipation in standby modes and when fully operational. For power-factor-corrected systems, the L6591 PWM controller also provides a PFC interface, allowing the PFC pre-regulator to be turned off to maximise power savings under light-load and no-load conditions.

Using the L6591 PWM controller with the zero-voltage switching asymmetrical half-bridge topology, designers can ensure compliance with regulations such as the International Energy Authority’s 1Watt plan for standby power, the EU’s EuP Directive for energy-using products and the US Government’s Energy Star programme. Regulations such as EuP and Energy Star call for minimum operating efficiency of 85% in power supplies for equipment such as PCs, servers, consumer products and general-purpose AC- DC adapters and chargers.

In addition to its power-saving properties, the L6591 PWM controller also has an built-in protection, including pulse-by-pulse over-current protection to prevent false tripping, overload protection with latched or auto restart behaviour and transformer-saturation detection. Adaptive Under-Voltage Lock-Out (UVLO) is implemented to ensure reliable operation of systems optimised for minimum no-load power.

The L6591 PWM controller combines its high integration and power-saving features with high voltage-handling capability in a small-outline SO16N surface-mount package.

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