Standby power supply line voltage fault detector
First Claim
1. In an A.C. power supply having input terminal means adapted for connection to A.C. power lines, output terminal means adapted for connection to an electrical load, a battery-operated inverter operable to supply power to said output terminal means, switching means operable between a first state for connectingly supplying power directly from said input terminal means to said output terminal means and to a second state breaking said connection and supplying electrical power from said inverter to said output terminal means, a power line voltage abnormality sensing circuit coupled to a chosen one of said terminal means for producing a normality-indicating signal condition responsively to a sensing of a terminal voltage condition across said chosen terminal means within at least one given amplitude limit and an abnormality-indicating signal condition responsively to a sensing of said terminal voltage condition outside of said limit, and control circuit means responsive to said abnormality sensing circuit signal conditions for actuating said switching means to one of said states responsively to receipt of said normality-indicating signal condition and to the other of said states responsively to receipt of said abnormality-indicating signal condition, the improvement comprising:
- waveform-producing circuit means associated with said abnormality sensing circuit and responsively coupled to said chosen terminal means for providing an output waveform of non-zero amplitude spanning the axis crossing regions of the terminal voltage waveform across said chosen terminal means and including means for causing said output waveform to respond to failure of said terminal voltage during any axis crossing thereof by an abrupt change in output waveform amplitude initiated synchronously with the occurrence of said failure, anddetector circuit means responsively coupled to said waveform-producing circuit means for providing said abnormality-indicating signal condition responsively to said abrupt change in output waveform amplitude beyond a given first threshold value.
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Accused Products
Abstract
A battery-operated standby power supply includes a circuit for the detection of failures in A.C. power line voltage provides immediate detection of power failure even if such failure occurs during the times of line voltage axis crossings. This is accomplished by providing and monitoring the amplitude of a synthesized waveform representing a full-wave rectified replica of the line voltage, combined with a 90° phase-shifted full-wave rectified replica of the line voltage waveform. The composite waveform has a peak-to-peak excursion of approximately 20% about a DC average without nulls. The phase-shifted waveform replicas are produced by a phase shift network configured to provide a strong differentiating function, thereby causing the phase-shifted replicas to reflect virtually instantaneously failure of the power line voltage, and in particular failure in the vicinity of an axis crossing, by an immediate change in amplitude. Transient overvoltages and undervoltages are similarly reflected. Suitable comparators are used to detect excursions beyond preset limits to produce a control signal which is used to actuate a battery-operated standby power supply from standby to power delivery mode.
33 Citations
22 Claims
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1. In an A.C. power supply having input terminal means adapted for connection to A.C. power lines, output terminal means adapted for connection to an electrical load, a battery-operated inverter operable to supply power to said output terminal means, switching means operable between a first state for connectingly supplying power directly from said input terminal means to said output terminal means and to a second state breaking said connection and supplying electrical power from said inverter to said output terminal means, a power line voltage abnormality sensing circuit coupled to a chosen one of said terminal means for producing a normality-indicating signal condition responsively to a sensing of a terminal voltage condition across said chosen terminal means within at least one given amplitude limit and an abnormality-indicating signal condition responsively to a sensing of said terminal voltage condition outside of said limit, and control circuit means responsive to said abnormality sensing circuit signal conditions for actuating said switching means to one of said states responsively to receipt of said normality-indicating signal condition and to the other of said states responsively to receipt of said abnormality-indicating signal condition, the improvement comprising:
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waveform-producing circuit means associated with said abnormality sensing circuit and responsively coupled to said chosen terminal means for providing an output waveform of non-zero amplitude spanning the axis crossing regions of the terminal voltage waveform across said chosen terminal means and including means for causing said output waveform to respond to failure of said terminal voltage during any axis crossing thereof by an abrupt change in output waveform amplitude initiated synchronously with the occurrence of said failure, and detector circuit means responsively coupled to said waveform-producing circuit means for providing said abnormality-indicating signal condition responsively to said abrupt change in output waveform amplitude beyond a given first threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification