International Business Machines Corporation

Diep N Ho

Randhir Singh Malik

William Hemena

Vijay V Oak

An AC adapter which reduces the amount of power drawn from an AC power source when a system is disconnected from the adapter, includes: a rectifier bridge for rectifying an AC voltage from an AC power supply; a conversion circuit coupled to the rectifier bridge for converting the rectified AC voltage to a DC voltage; and an opto-coupler coupled to the conversion circuit for monitoring an output connection of the circuit, wherein when a system is not coupled to the output connection, the opto-coupler substantially prevents the AC voltage from being drawn from the AC power supply. The adapter circuit uses an opto-coupler comprising a diode and a transistor to reduce the amount of current drawn from an AC power supply when a system is not connected to the AC adapter. In this manner, the AC adapter is prevented from becoming heated when no system is connected.

Circuit for AC adapter to reduce power drawn from an AC power source

The power supply in accordance with the present invention provides AC redundancy while also preventing voltages from multiple AC voltage sources from adding at a common node. The adding of voltages is avoided by ensuring that only one AC voltage source at a time is providing the voltage at the output. Even if the other AC voltage sources are connected afterwards, these later AC voltage source are prevented from providing power at the output. In addition, diodes prevent current from back flowing to the AC voltage sources which are not supplying power to the output. Because the power supply in accordance with the present invention neither uses redundant AC to DC power supplies from independent AC voltage sources, nor does it use a costly transfer switch, the power supply in accordance with the present invention is more cost effective than conventional redundant power supplies.

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Raleigh, NC, United States of America

Diep N Ho