Abstract: Apparatus and method are provided for fault detecting in an electrical system such as a redundant or fault-tolerant system. A current receiving device connected in shunt or in series in such a system draws electric current from the electrical system being monitored. During normal operation, while current is still flowing properly through the system being monitored, an appropriate indication such as a continued series of pulses is generated, which is interpreted as indicating proper operation. If that current flow is cut off, indicating a fault condition, then the apparatus and method provide an appropriate signal (such as cutoff of the series of pulses) to a communication system which provides an appropriate indication to an external location. The current receiving device can be a relaxation oscillator together with another device which can be a pulse generator, an L-C energy transfer arrangement, a bridge circuit including an inductor, a two-winding inductor or a capacitor.

Abstract: An anticipatory power failure detection apparatus and method, for use in connection with power supplies providing a regulated voltage signal to an electronic load such as a computer, employing circuitry for determining whether a control signal, within the regulated power supply circuit, is in a saturation state. Upon detecting a saturation state for the control signal, circuitry signals that an input power failure is occurring. The regulated power supply system can be a switching-type voltage regulation control system, wherein a pulse-width modulated switching system controls the periodic input of energy to an energy-storage network which generates the regulated voltage output signal. A derivative of the error signal is periodically sampled for determining whether it is in the saturation state. The regulated power supply control signal will be in the saturation state when the unregulated input voltage supply is insufficient to maintain the regulated voltage signal at the specified optimum operating point.

Abstract: An apparatus and method for detecting an AC power failure condition employs a fast attack, slow decay, energy storage circuit for tracking an AC input signal and for providing a slowly decaying output based upon a last received peak voltage input value. A current detection circuit monitors the current flow to the storage circuit from the AC mains and generates a current detection signal in response thereto. A power failure condition is declared when either the voltage across the energy storage circuit decays below a selected threshold value or current is not detected flowing to the energy storage circuit at a selected time. A particular current detection circuit employs a high permeability core which is saturated by a current in the sensed line having a current value below an expected peak current flowing to the energy storage circuit. An interrogation pulse periodically energizes an interrogation winding which, in the absence of current in the sensed line, induces a signal across an output winding.