Neon power supply with improved ground fault protection circuit
First Claim
1. A ground fault protected power supply delivering high voltage electrical power to a gas discharge light and detecting ground fault current, comprising:
- a transformer core of magnetically permeable material,a primary winding having first and second primary terminals, said primary winding wound on said transformer core such that current flowing in said primary winding induces magnetic flux in said transformer core,an oscillator connected to said primary terminals to supply alternating current thereto to induce magnetic flux in said transformer core,a secondary winding having first and second secondary terminals, said secondary winding wound on said transformer core such that magnetic flux in said transformer core induces current in said secondary winding, said secondary terminals supplying electrical power to said gas discharge light,a clamp winding having first and second clamp winding terminals, said clamp winding being wound on said transformer core such that magnetic flux in said transformer core induces current in said clamp winding, said clamp winding being wound on said transformer core adjacent to said secondary winding such that said clamp winding is capacitively coupled to said secondary winding,current imbalance detection circuitry connected to said clamp winding terminals for detecting imbalance between current flowing into the first clamp winding terminal and current flowing out of the second clamp winding terminal, said current imbalance detection circuitry generating a ground fault electrical signal upon detection of a current imbalance between said first and second clamp winding terminals.
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Accused Products
Abstract
A power supply power supply circuit of the kind which includes a transformer having primary and secondary windings and an oscillator for driving the primary winding in a bi-directional fashion, suitable for driving gas discharge lighting such as neon signs, which prevents dangerous overvoltage output conditions and detects relatively low level ground fault currents. The transformer includes a clamp winding which is in proximity to and capacitively coupled to the secondary winding. The terminals of the clamp winding are connected to a current imbalance detection circuit for detecting imbalance between the current flowing into one clamp winding terminal and the current out of the other clamp winding terminal. In a ground fault condition, ground fault current flows in an unbalanced fashion into the clamp winding terminal(s), and through the capacitive coupling to the secondary winding. This ground fault current is detected by the current imbalance detection circuit, causing the current imbalance detection circuit to generate an electrical signal indicative of ground fault current, which shuts down the oscillator.
29 Citations
20 Claims
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1. A ground fault protected power supply delivering high voltage electrical power to a gas discharge light and detecting ground fault current, comprising:
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a transformer core of magnetically permeable material, a primary winding having first and second primary terminals, said primary winding wound on said transformer core such that current flowing in said primary winding induces magnetic flux in said transformer core, an oscillator connected to said primary terminals to supply alternating current thereto to induce magnetic flux in said transformer core, a secondary winding having first and second secondary terminals, said secondary winding wound on said transformer core such that magnetic flux in said transformer core induces current in said secondary winding, said secondary terminals supplying electrical power to said gas discharge light, a clamp winding having first and second clamp winding terminals, said clamp winding being wound on said transformer core such that magnetic flux in said transformer core induces current in said clamp winding, said clamp winding being wound on said transformer core adjacent to said secondary winding such that said clamp winding is capacitively coupled to said secondary winding, current imbalance detection circuitry connected to said clamp winding terminals for detecting imbalance between current flowing into the first clamp winding terminal and current flowing out of the second clamp winding terminal, said current imbalance detection circuitry generating a ground fault electrical signal upon detection of a current imbalance between said first and second clamp winding terminals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of delivering high voltage electrical power to a gas discharge light while detecting ground fault current, comprising:
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providing a transformer core of magnetically permeable material, winding a primary winding having first and second primary terminals, on said transformer core such that current flowing in said primary winding induces magnetic flux in said transformer core, supplying alternating current to said first and second primary terminals to induce magnetic flux in said transformer core, winding a secondary winding having first and second secondary terminals, on said transformer core such that magnetic flux in said transformer core induces current in said secondary winding, connecting said secondary terminals to said gas discharge light to supply electrical power thereto, winding a clamp winding having first and second clamp winding terminals, on said transformer core such that magnetic flux in said transformer core induces current in said clamp winding, said clamp winding being wound on said transformer core adjacent to said secondary winding such that said clamp winding is capacitively coupled to said secondary winding, detecting imbalance between current flowing into the first clamp winding terminal and current flowing out of the second clamp winding terminal, and identifying a ground fault upon detection of a current imbalance between said first and second clamp winding terminals. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification