Tandem Computers Incorporated

Cisco Technology, Inc.

Boschert, Inc.

Samson K Toy

Mark A Taylor

A safe external A/C adapter protecting the user against hazardous, high-voltage D/C output. High voltage is defined as any voltage in excess of 60V D/C. The adapter provides an internal remote ON/OFF circuit that automatically switches the D/C output OFF unless the output plug is seated within a mating socket disposed in an electronic device powered by the adapter. When the output plug is so seated, the hazardous voltage output is inaccessible to the user. In addition, a secondary shutdown circuit is provided that latches off the A/C input in the unlikely event that the remote ON/OFF circuit should fail. The secondary shutdown circuit is largely independent from the primary remote ON/OFF circuit, and can be implemented using control circuitry already present in the adapter. No special mechanical connectors are required. Also, because the D/C output is energized only upon insertion of the D/C output plug into the mating socket, and disabled when the output plug is removed, both the electronic device and the user are protected from electric arcing or sparking.

External A/C adapter protecting user against hazardous voltage

A supply voltage monitor for providing an indication of a supply voltage level considered safe for electronic circuit operation includes a supervisory or guard circuit that blocks the output of the monitor in favor of a secondary output for those periods of time when the monitor is considered to not be able of providing a valid reflection of supply voltage status.

Power on system

A regulator circuit supplies a regulated low, DC voltage that is derived from an unregulated voltage provided by a pair of redundant batteries. The regulator circuit comprises regulation control that responds to a feedback signal developed from monitoring the regulated voltage to maintain the regulated voltage at a desired level. Battery monitors supervise the voltage levels of the batteries used, and shut down the regulator when the battery voltages drop below a predetermined voltage level to preserve battery life.

Power regulation for redundant battery supplies

A high current, low voltage, regulated D.C. power supply incorporating a parallel pair of bridges connected across a D.C. supply and each having alternately switched opposite legs for producing across its output a relatively high frequency A.C. to a stepdown transformer. Each of the bridges is switched out of phase with the other to minimize output ripple in the combined D.C. produced from rectifiers at the secondary of the stepdown transformers. Regulation of the supply is provided by a current sensor at the secondary of each transformer which produces a signal that is compared with a signal representing D.C. output level to alter the duty cycle in the switching circuitry to the parallel bridges. The novel feature is that the regulation control circuits of two or more identical supplies may be coupled to produce master-slave power supply combinations capable of greatly increasing the output power capabilities.

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Sunnyvale, CA, United States of America

Samson K Toy