Ground fault protection circuit
First Claim
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1. A circuit, comprising:
- an inverter circuit for providing an AC output signal to a load, the inverter circuit having first and second voltage rails;
a ground fault circuit having first and second input terminals and coupled to the first voltage rail of the inverter at said first input terminal and coupled to earth ground at said second input terminal, wherein the ground fault circuit detects a flow of current from the load to earth ground through a path external to the circuit, said ground fault circuit including a detection circuit for detecting the flow of current to earth ground and a detection control circuit for disabling the inverter to terminate the flow of current to the load, wherein said detection circuit is a resonance circuit configured such that the flow of current therethrough generates a local resonance having a resonant frequency at or near a frequency of operation of the inverter circuit.
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Abstract
A ground fault detection circuit is coupled to an AC circuit and to earth ground for detecting a flow of energy from the AC circuit to earth ground through a path external to the AC circuit. In one embodiment, the ground fault circuit includes a detection circuit coupled to a negative rail of an inverter, which forms part of the AC circuit, and a detection control circuit coupled to the inverter for disabling the AC circuit.
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Citations
12 Claims
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1. A circuit, comprising:
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an inverter circuit for providing an AC output signal to a load, the inverter circuit having first and second voltage rails;
a ground fault circuit having first and second input terminals and coupled to the first voltage rail of the inverter at said first input terminal and coupled to earth ground at said second input terminal, wherein the ground fault circuit detects a flow of current from the load to earth ground through a path external to the circuit, said ground fault circuit including a detection circuit for detecting the flow of current to earth ground and a detection control circuit for disabling the inverter to terminate the flow of current to the load, wherein said detection circuit is a resonance circuit configured such that the flow of current therethrough generates a local resonance having a resonant frequency at or near a frequency of operation of the inverter circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for providing ground fault protection for an inverter circuit driving a load, comprising:
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providing a ground fault circuit for detecting energy flow from an inverter circuit for energizing a load to earth ground generated by a flow of current from the inverter circuit to earth ground through a path external to the inverter circuit, configuring said ground fault circuit to include a detection circuit having circuit for generating a resonance frequency at or near the operation frequency of said inverter circuit to amplify said flow of current, and wherein said ground fault circuit further includes a control circuit for disabling said inverter when said energy flow exceeds a selected threshold. - View Dependent Claims (11)
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12. A method for providing ground fault protection to an inverter circuit energizing a load, comprising the steps of:
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detecting a common mode energy signal, generated due to a discontinuity in an AC signal path from said inverter circuit to ground, the step of detecting being performed by a ground fault circuit having a reasonable circuit for generating a local resonance frequency at or near the operation frequency of said inverter circuit; and
limiting a current to the load when said detected common mode energy signal exceeds a selected threshold.
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Specification