A power failure detection circuit (4) comprises an input port (5) for applying a voltage signal to be monitored; a voltage rate of change detecting circuit (6-15) connected to said input port (5) for deriving a signal representative of a rate of change of said voltage signal, and a first comparator (14-16) for comparing said representative signal to a predetermined limit and for outputting a first power failure signal if said representative signal exceeds a predetermined limit.

Power failure detection circuit

A CCFL power converter circuit is provided using a high-efficiency zero-voltage-switching technique that eliminates switching losses associated with the power MOSFETs. An optimal sweeping-frequency technique is used in the CCFL ignition by accounting for the parasitic capacitance in the resonant tank circuit. Additionally, the circuit is self-learning and is adapted to determine the optimum operating frequency for the circuit with a given load. An over-voltage protection circuit can also be provided to ensure that the circuit components are protected in the case of open-lamp condition.

High-efficiency adaptive DC/AC converter

A system for rapidly detecting power disturbances with ferroresonant transformers having a decay profile comprising the steps of rectifying a power signal; comparing the rectified signal against a reference signal; comparing the rectified signal against a dynamic reference signal; and generating a power-fail signal in response to either comparison falling below its respective reference.

Fast power-fail detector for power supplies with energy hysteresis

An H-bridge converter connected to a load includes a direct current power source, first and second pairs of switches alternately switched in order to connect the power source to the load, a plurality of snubber circuits correspondingly connected to the switches for protecting the switches from high currents and voltages, a sensing circuit connected between the first and second pairs of switches for sensing when each of the first and second pairs of switches are closed, and a snubber circuit counteracting circuit connected to a first snubber circuit of the first pair of switches, a second snubber circuit of the second pair of switches and to the sensing circuit for counteracting the flow of snubber currents in the sensing circuit from the first and second snubber circuits

Circuit for eliminating snubber current noise in the sense circuit of an H-bridge inverter

Presented is a current sensor and control device which when connected into a 120 Volt AC circuit senses that alternating current is present in the circuit and controls the application of such current in such manner that electric power cannot be drawn unless the sensor senses that a load is being imposed on the alternating current circuit.

Current sensor and control device

A fault detection system for use in power supply systems using ferro-resonant transformers is presented. Current sensing means are used to sense the current flowing in the ferro-resonant circuit associated with operation of the ferro-resonant transformer. A fault detection circuit, powered by its own power supply connected to the primary source of power, monitors the sensed current and signals any significant change therein. A fault condition in any of the secondary circuits of the transformer causes the ferro-resonant current to change, and upon sensing this change, the fault detection circuit disconnects the primary of the transformer from the source of power.

Arthur F. Witulski

Papers

Fault protection system for power supplies that use ferro-resonant transformers