Lucent Technologies Inc.

At+t Corp.

Paul John

Walter G Kutzavitch

A current limiting circuit for a power switching transistor, the current limiting circuit incorporating a DC modulator to control the conducting/non-conducting state of the switching transistor, with an input signal generated and supplied to the modulator (and thus controlling a modulator DC bias output signal and therefore the conducting/non-conducting state of the switching transistor) comprised of two components: a first component which controls the modulator state based upon limiting maximum transistor current when a DC supply voltage is at a nominal design value, and a second component which dynamically adjusts the value of the modulator input signal when values of the DC supply voltage are other than the nominal design value.

Control circuit arrangement for limiting output current in power

A power supply circuit drives a load with first and second power sources. The power supply circuit has a switching network comprising a first switch and an interlock switch. A first circuit section connects the first power source to the load only when both the first switch and the interlock switch are on, and a second circuit section connects the second power source to the load only when both the first switch and the interlock switch are on. The switching network provides isolation between the first and second circuit sections.

Switching network for circuit with multiple power sources

An improved pulse width modulation type switching power supply uses an opto-isolator as an output voltage error amplifier which feeds back an error signal to control pulse width modulation as well as to provide isolation between the primary and secondary voltages of the power supply.

Pulse width modulator for switching power supply

A high efficiency switching power transistor uses the energy in a snubber circuit to drive the gate driver and the pulse-width-modulator (PWM). The snubber consists of a resistor and a capacitor connected in series between the drain and source of a field-effect-transistor (FET). A steering diode is connected from the junction between the capacitor and the resistor to the power supply of the gate driver and PWM. This diode steers current from the snubber and makes it flow into the power supply thereby lowering the power requirements of the power supply. This energy would have been dissipated in the snubber as heat if it were not used this way. Efficiency of the switcher is increased both by lowering heat loss in the snubber and by using recovered snubber energy to lower the power requirements of the power supply of the gate driver and PWM.

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Hazlet, NJ, United States of America

Paul John