Input protection circuit
First Claim
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1. An inductively powered secondary circuit having protection circuitry comprising:
- a secondary coil for wirelessly receiving inductive power from an inductive power supply, wherein the inductively powered secondary circuit receives power wirelessly and is physically separable from the inductive power supply;
a secondary load in communication with said secondary coil;
a thermal cutoff electrically connected between said secondary coil and said secondary load, wherein in response to being heated to a threshold temperature, said thermal cutoff creates an open circuit in said protection circuit;
a voltage clamp electrically and thermally coupled to said thermal cutoff and electrically connected between said secondary coil and said secondary load, wherein said voltage clamp is adapted to clamp an input voltage to a desired level in response to an overvoltage condition and dissipate energy to said thermal cutoff in the form of heat; and
an electrical fuse electrically connected between said secondary coil and said thermal cutoff, wherein said electrical fuse disconnects said thermal cutoff, said voltage clamp, and said secondary load from said secondary coil in response to a large transient, and wherein said thermal cutoff is capable of creating an open circuit when there is insufficient power to activate said electrical fuse.
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Abstract
A voltage clamp protection circuit to protect against overvoltage conditions where there is insufficient current to blow a fuse. The voltage clamp protection circuit includes a voltage clamp and a thermal cutoff. The voltage clamp clamps any overvoltage to a clamping voltage. If an overvoltage condition persists for too long the voltage clamp dissipates a sufficient amount of heat to activate the thermal cutoff creating an open circuit that protects the rest of the circuit. The voltage clamp protection circuit may be used in combination with a variety of other protection circuits to provide increased protection.
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Citations
25 Claims
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1. An inductively powered secondary circuit having protection circuitry comprising:
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a secondary coil for wirelessly receiving inductive power from an inductive power supply, wherein the inductively powered secondary circuit receives power wirelessly and is physically separable from the inductive power supply; a secondary load in communication with said secondary coil; a thermal cutoff electrically connected between said secondary coil and said secondary load, wherein in response to being heated to a threshold temperature, said thermal cutoff creates an open circuit in said protection circuit; a voltage clamp electrically and thermally coupled to said thermal cutoff and electrically connected between said secondary coil and said secondary load, wherein said voltage clamp is adapted to clamp an input voltage to a desired level in response to an overvoltage condition and dissipate energy to said thermal cutoff in the form of heat; and an electrical fuse electrically connected between said secondary coil and said thermal cutoff, wherein said electrical fuse disconnects said thermal cutoff, said voltage clamp, and said secondary load from said secondary coil in response to a large transient, and wherein said thermal cutoff is capable of creating an open circuit when there is insufficient power to activate said electrical fuse. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An inductively powered secondary circuit for receiving power from a primary circuit, said secondary circuit comprising:
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a secondary coil for wirelessly receiving inductive power at an input voltage, wherein there is no physical connection between said secondary circuit and said primary circuit, wherein said inductively powered secondary circuit receives power wirelessly from the primary circuit and is physically separable from said primary circuit; a secondary load in electrical communication with said secondary coil; and a protection circuit electrically connected between said secondary coil and said secondary load, said protection circuit including; a thermal cutoff, wherein in response to being heated to a threshold temperature, said thermal cutoff electrically disconnects said secondary load from said secondary coil; a voltage clamp electrically and thermally coupled to said thermal cutoff, wherein said voltage clamp is adapted to clamp said input voltage to a desired level in response to an overvoltage condition and dissipate energy to said thermal cutoff in the form of heat; and an electrical fuse electrically connected between said secondary coil and said protection circuit, wherein said electrical fuse disconnects said protection circuit and said secondary load from said secondary coil in response to a large transient, and wherein said protection circuit is capable of creating an open circuit when there is insufficient power to activate said electrical fuse. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An inductively powered secondary circuit comprising:
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a secondary coil for wirelessly receiving inductive power from an inductive power supply, wherein said inductively powered secondary circuit receives power wirelessly from the inductive power supply and is physically separable from the inductive power supply; and a secondary load in electrical communication with said secondary coil; a microprocessor controlled field effect transistor connected between said secondary coil and said secondary load, wherein said field effect transistor disconnects said secondary load from said secondary coil in response to detection of a fault condition; and a voltage clamp protection circuit including; a thermal cutoff, wherein in response to being heated to a threshold temperature, said thermal cutoff electrically disconnects said secondary load from said secondary coil; and a voltage clamp electrically and thermally coupled to said thermal cutoff, wherein said voltage clamp is adapted to clamp said input voltage to a desired level in response to an overvoltage condition and dissipate energy to said thermal cutoff in the form of heat; and an electrical fuse electrically connected between said secondary coil and said voltage clamp protection circuit, wherein said electrical fuse disconnects said voltage clamp protection circuit, said microprocessor controlled field effect transistor, and said secondary load from said secondary coil in response to a large transient, and wherein said voltage clamp protection circuit is capable of creating an open circuit when there is insufficient power to activate said electrical fuse. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification