At&t Bell Laboratories

Charles E Harm

Kenneth J Timm

George Knoedl, Jr

William A Nitz

A battery charger control includes a thermal sensor attached to the battery being charged. If the temperature readings indicate a thermal runaway condition the charging current output is adjusted in accord with the temperature reading by means of voltage injeciton into an output sense lead of the charging circuitry as a means of achieving a control that prevents thermal runaway of the battery while still permitting continuous charging of the battery.

Battery charger with thermal runaway protection

A method of and apparatus for monitoring the output signals of a power converter, having galvanic isolation between the input and output, observes the voltage and current on the primary side of the converter as reflected through a tertiary winding or influenced through the primary winding of the power transformer and applies error corrections thereto to replicate the output signal. These corrections are arrived at by compensating for operational differences between input and output circuitry and by emulating, on the primary side, the output side circuitry that causes the differences between the output signal and the reflected signal, and the conditions to which the output side circuitry is subjected. The resulting replicated signal is applied to feedback control circuitry, in lieu of the actual output signal, and used to regulate the output of the power converter.

Output voltage estimating circuit for a power converter having galvanic

Frequency variation in a resonant zero voltage switching (ZVS) power converter is combined with supplemental duty cycle modulation to obtain voltage regulation and to narrow the required frequency band needed for regulation of a given output load. These two regulation processes are applied simultaneously to the power switch control in order to accommodate a wider range of regulated load. Hence in the alternative, for a given load range a smaller frequency range is needed than would be the case if frequency variation alone is used. The regulation control circuit includes both a duty cycle modulator and a frequency modulator each being responsive to an error signal responsive to a differential between an output voltage of the converter and a reference voltage. Each individual modulator has its own transfer function; one transfer function being kHz/volt the other transfer function being % duty cycle/volt. The regulation control circuit output is a rectangular pulse type signal that contains both elements of frequency modulation and duty cycle modulation.

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Dallas City, TX, United States of America

Charles E Harm