Power supply protection circuit
First Claim
1. An apparatus for protecting electronic circuit elements from hazardous voltages produced by an energy source, comprising:
- a energy source for producing electrical energy having a predetermined energy level, said energy source having positive and negative terminals;
an electrical load being connected to the positive and negative terminals of said electrical energy source, said electrical load receiving electrical energy from said energy source;
a first Zener diode for receiving electrical energy from said electrical energy source and producing an overvoltage signal in response to receiving electrical energy greater than the breakdown voltage of the first Zener diode;
an NMOSFET for controllably regulating the electrical current flowing through said electrical load, said NMOSFET having a drain, gate, source and substrate, and being connected between the negative terminal of said energy source and said electrical load; and
control means for receiving the overvoltage signal and responsively limiting the NMOSFET gate-source voltage to increase the impedance of said NMOSFET to a predetermined impedance level, thereby limiting the current flowing through said electrical load to protect said electrical load from hazardous voltages, wherein said NMOSFET remains conducting to allow said electrical load to receive electrical energy from said energy source at substantially the breakdown voltage of said first Zener diode during a hazardous voltage condition.
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Abstract
In one aspect of the present invention, an apparatus for protecting electronic circuit elements from hazardous voltages is provided. The apparatus includes a source of electrical energy that produces electrical energy having a predetermined energy level. An electrical load is connected to the electrical energy source and responsively receives electrical energy. A signaling device receives electrical energy from the electrical energy source and produces an overvoltage signal in response to receiving electrical energy greater than the predetermined energy level. An NMOSFET is connected to the electrical load, and controllably regulates the electrical current flowing through the electrical load. A control device receives the overvoltage signal and responsively controls the operation of the NMOSFET.
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Citations
11 Claims
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1. An apparatus for protecting electronic circuit elements from hazardous voltages produced by an energy source, comprising:
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a energy source for producing electrical energy having a predetermined energy level, said energy source having positive and negative terminals; an electrical load being connected to the positive and negative terminals of said electrical energy source, said electrical load receiving electrical energy from said energy source; a first Zener diode for receiving electrical energy from said electrical energy source and producing an overvoltage signal in response to receiving electrical energy greater than the breakdown voltage of the first Zener diode; an NMOSFET for controllably regulating the electrical current flowing through said electrical load, said NMOSFET having a drain, gate, source and substrate, and being connected between the negative terminal of said energy source and said electrical load; and control means for receiving the overvoltage signal and responsively limiting the NMOSFET gate-source voltage to increase the impedance of said NMOSFET to a predetermined impedance level, thereby limiting the current flowing through said electrical load to protect said electrical load from hazardous voltages, wherein said NMOSFET remains conducting to allow said electrical load to receive electrical energy from said energy source at substantially the breakdown voltage of said first Zener diode during a hazardous voltage condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification