Power managers target low-output switchers

The STR-A61xx Series of power-management ICs are pulse ratio control topology devices designed for use in relatively low output power switch-mode power-supply designs.

The new STR-A61xx Series of power-management ICs from Allegro MicroSystems Europe are PRC (pulse ratio control) topology devices designed for use in relatively low output power switch-mode power-supply designs with output power up to 20W at universal input or 24W at 230V AC input.

The pulse ratio control operates with fixed off-time and variable on-time, and the devices incorporate an auto-standby function which reduces input power consumption to less than 50mW at 230V AC input using burst-mode operation stabilised by an auto-biasing function to avoid "hiccup" phenomena.

Current-mode feedback and leading-edge blanking stabilise the entire power-supply operation.

Internal protection includes overvoltage using bias-winding voltage sensing (with latch), overcurrent (pulse by pulse), overload (with auto restart), and thermal shutdown (with latch).

Each device incorporates a controller chip based on a proprietary high-voltage BCD process, and a power MOSFET which is available in voltage ratings from 500 to 800V, input voltages of 120V, 230V or universal, and power outputs from 12 to 24W.

The entire circuit is housed in a DIP-8 package using hybrid assembly technology.

An integrated startup circuit reduces the input power consumption and improves the system efficiency at light output loads.

The use of an avalanche-guaranteed MOSFET also improves system-level reliability and does not require voltage derating.

Applications include battery chargers for portable consumer electronics appliances, standby power supplies for PCs, TV and audio systems, and low-power supplies for inkjet printers, DVDs and other home appliances.

Sanken Electric semiconductor devices are available in Europe from Allegro MicroSystems Europe, a Sanken Electric subsidiary company, and via its network of distributors.

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