Updated off-line switching converter tolerates poor AC supplies

Updated off-line switching converter tolerates poor AC supplies

New Products |
By Graham Prophet

The parts are typically used for auxiliary, always-on power supplies in a wide range of domestic appliance and industrial products. “We sell many millions of these,” says a company spokesman, “they are everywhere from powering the clock of a coffee-maker to providing power in industrial controls.”


The new generation, LinkSwitch-TN2 is an off-line switcher IC for non-isolated applications with up to 360 mA output current. It may be configured as a buck, buck-boost or a non-isolated flyback converter, delivers high accuracy, high efficiency and excellent no-load performance. The device incorporates new safety features including input over- and under-voltage protection and a rugged MOSFET with a 725V breakdown voltage, offering robust output short-circuit and over-temperature protection against line surges and swells. Applications include appliances, HVAC, industrial, home automation (IOT) and metering systems, particularly those destined for India and other geographies with challenging power grid stability.


LinkSwitch-TN2 ICs feature voltage regulation of better than ±3%. This high level of accuracy allows designers to eliminate post regulators, minimizing the BOM, increasing efficiency and reducing size. The new IC requires 20 additional components to complete a buck converter, and may be configured to use off-the-shelf inductors, further reducing cost and supply chain complexity.


Efficiency in low-power applications is above 80% in 12V, 120 mA (1.4W) buck designs, for example. LinkSwitch-TN2 designs typically provide excellent efficiency across the entire load range while consuming less than 30 mW no-load in a buck arrangement and less than 10 mW when configured as a non-isolated flyback. This, PI says, is a key tool for designers addressing Total Energy Consumption (TEC) regulations, which prescribe an energy budget limit over a range of operating modes. LinkSwitch-TN2 efficiency performance enables manufacturers to design power supplies to meet worldwide product energy-efficiency requirements from the U.S. DOE, European Commission ErP Ecodesign Directive, California Energy Commission, ENERGY STAR®, and others.


The ICs include a selectable cycle-by-cycle current limit which allows designers to choose low-cost inductors and capacitors saving cost and board space, or configure the circuit to output higher power using optimized external components. LinkSwitch-TN2 ICs come in three different packages: PDIP-8C, SO-8C, and SMD-8C. The latter package is, in effect, a DIP outline but with the pins spread “gull-wing” to give surface mounting with increased clearances and simple handling. Devices are priced at $0.60 (10,000)


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