Allegro offers power-management ICs for low-power SMPS applications

Walton-on-Thames, UK — The STR-A61xx Series of power-management ICs from Allegro MicroSystems 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 20 W at universal input or 24 W at 230 V 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 50 mW at 230 VAC 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 800 V, input voltages of 120 V, 230 V or universal, and power outputs from 12 to 24 W. The entire circuit is housed in a DIP-8 package using hybrid assembly technology. An integrated start-up 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. Allegro MicroSystems Europe Ltd , Walton-on-Thames, UK.

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