STMicroelectronics Introduces Integrated PWM Controller
October 2, 2008 // Published as a news service by IHS
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The L6591 pulse-width modulation (PWM) controller from STMicroelectronics (ST) is an integrated controller optimized for zero-voltage switching asymmetrical half-bridge converters.
According to ST, this enable smaller, lower-cost power supplies delivering high efficiency from standby to full load, thereby reducing heat and power loss.
For use in offline power supplies, the L6591 implements the functional blocks necessary to control a soft-switching half-bridge converter.
Zero-voltage switching eliminates turn-on switching losses, minimizes electromagnetic interference (EMI) emissions and also enables operation at up to 500 kHz.
In addition, the L6591 implements pulse skipping under light-load and no-load conditions and has a quiescent current lower than 3 mA.
Together, ST said, these properties allow designers to meet customer and end consumer demands to minimize power dissipation in standby modes as well as during full operation.
For power-factor-corrected systems, the L6591 also provides a power factor correction (PFC) interface, allowing the PFC preregulator to be turned off to maximize power savings under light- and no-load conditions.
Using the L6591 with the zero-voltage switching asymmetrical half-bridge topology, designers can ensure compliance with regulations such as the International Energy Authority's 1 Watt (W) plan for standby power, the European Union (EU) directive for energy-using products (EuP) and the U.S. government's Energy Star program.
Regulations such as EuP and Energy Star now call for minimum operating efficiency of 85% in power supplies for equipment such as PCs, servers, consumer products and general-purpose alternating current/direct current (AC/DC) adapters and chargers.
According to ST, existing proposals look to increase this target in the future, and the L6591 offers the headroom to meet these tighter requirements.
In addition to its power-saving properties, the L6591 also has built-in protection, including pulse-by-pulse overcurrent protection to prevent false tripping, overload protection with latched or auto restart behavior and transformer-saturation detection.
Adaptive undervoltage lockout (UVLO) is also implemented for systems optimized for minimum no-load power.
The L6591 offers voltage-handling capability of up to 700 volts (V), in a small-outline SO16N surface-mount package.
Source: STMicroelectronics (ST).