At&t Bell Laboratories

Bell Telephone Laboratories

Richard C Ray

Richard H Hock

Rudolph Scuderi

Hermann Fickenscher

A voltage controlled flyback converter used as a battery charging circuit avoids the power dissipation of the more conventional series-type regulator-type charging circuits but cannot be readily utilized because of the high gain in the feedback loop due to the battery voltage, which causes instabilities therein when it is operated in a continuous current mode. These instabilities are avoided in a flyback converter used for battery charging by using current control techniques to control current on the primary side of the converter during high-rate battery charging. During low-rate charging, normal voltage feedback from an output current sensing resistor is used as long as the converter operates in a discontinuous mode.

Buck-boost converter with dual-mode control for battery charging

A power failure detector for an off-line switcher provides an indication of power failure to a microprocessor load to permit an orderly shutdown without loss of data. The failure detector includes a voltage storage device shunting a secondary winding of a converter power transformer prior to the isolating diode. When its voltage drops below a preset threshold, the microprocessor load is notified that a shutdown action is to be taken.

Power failure alarm circuit permitting orderly shutdown of

An uninterruptible power supply utilizes a controlled ferroresonant regulator to derive a regulated DC voltage from a primary AC source. A reserve source of DC power is coupled to the output through a DC voltage regulator which is activated when the DC output voltage of the power supply drops below a predetermined threshold.

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Randolph Township, NJ, United States of America

Richard C Ray