Input protection circuit

• US 8,259,428 B2
• Filed: 04/23/2009
• Issued: 09/04/2012
• Est. Priority Date: 04/25/2008
• Status: Active Grant

• Current Assignee: Philips IP Ventures B.V. (Koninklijke Philips N.V.)
• Original Assignee: Access Business Group International LLC (Alticor Incorporated)
• Inventors: Blaha, Mark A., Liff, Dale R., Zeik, Andrew C., Baarman, David W., Mollema, Scott A.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): BAUER, SCOTT ALLEN
• Application Number:
  US12/428,713
• Publication Number:
  US 20090268356A1
• Time in Patent Office: 1,230 Days
• Field of Search: 361/103, 320/108, 320/115, 320/107
• US Class Current: 361/103
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device

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.

Claims

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.

2. The protection circuit of claim 1 wherein, in response to said overvoltage condition persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature.

3. The protection circuit of claim 1 wherein, in response to said overvoltage condition persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature before said voltage clamp malfunction.

4. The protection circuit of claim 1 wherein said thermal cutoff is capable of creating an open circuit when there is insufficient power to activate an electrical fuse.

5. The protection circuit of claim 1 wherein said thermal cutoff and said voltage clamp are operational without input from a microcontroller.

6. The protection circuit of claim 1 wherein said thermal cutoff and said voltage clamp are operational without a power source.

7. The protection circuit of claim 1 wherein said at least two diodes are zener diodes, wherein at least one of said at least two diodes is electrically connected to oppose at least one other of said at least two diodes.

8. The protection circuit of claim 1 further comprising thermal adhesive, wherein said thermal adhesive assists in the transfer of heat from said voltage clamp to said thermal cutoff.

9. An inductively powered secondary circuit for receiving power from a primary circuit, said secondary circuit comprising:

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.

10. The inductively powered secondary circuit of claim 9 wherein, in response to said overvoltage condition persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature.

11. The inductively powered secondary circuit of claim 9 wherein, in response to said overvoltage condition persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature before said voltage clamp malfunctions.

12. The inductively powered secondary circuit of claim 9 wherein said thermal cutoff is capable of disconnecting said secondary load from said secondary coil when there is insufficient power to activate an electrical fuse.

13. The inductively powered secondary circuit of claim 9 wherein said thermal cutoff and said voltage clamp are operational without input from a microcontroller.

14. The inductively powered secondary circuit of claim 9 wherein said thermal cutoff and said voltage clamp are operational without a power source.

15. The inductively powered secondary circuit of claim 9 wherein said voltage clamp is a transient voltage suppressor, said transient voltage suppressor being a bidirectional transient voltage suppressor including at least two diodes in electrical communication, said at least two diodes are zener diodes, wherein at least one of said at least two diodes is electrically connected to oppose at least one other of said at least two diodes.

16. The inductively powered secondary circuit of claim 9 further comprising thermal adhesive, wherein said thermal adhesive assists in the transfer of heat from said voltage clamp to said thermal cutoff.

17. An inductively powered secondary circuit comprising:

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.

18. The inductively powered secondary circuit of claim 17 wherein, in response to said overvoltage consistent persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature.

19. The inductively powered secondary circuit of claim 17 wherein, in response to said overvoltage condition persisting, said voltage clamp dissipates a sufficient amount of heat to reach said threshold temperature before said voltage clamp malfunctions.

20. The inductively powered secondary circuit of claim 17 wherein said thermal cutoff is capable of disconnecting said secondary load from said secondary coil when there is insufficient power to activate an electrical fuse.

21. The inductively powered secondary circuit of claim 17 wherein said thermal cutoff and said voltage clamp are operational without input from a microcontroller.

22. The inductively powered secondary circuit of claim 17 wherein said thermal cutoff and said voltage clamp are operational without a power source.

23. The inductively powered secondary circuit of claim 17 wherein said voltage clamp is a transient voltage suppressor, said transient voltage suppressor being a bidirectional transient voltage suppressor including at least two diodes in electrical communication, said at least two diodes are zener diodes, wherein at least one of said at least two diodes is electrically connected to oppose at least one other of said at least two diodes.

24. The inductively powered secondary circuit of claim 17 further comprising thermal adhesive, wherein said thermal adhesive assists in the transfer of heat from said voltage clamp to said thermal cutoff.

25. The inductively powered secondary circuit of claim 17 including an electrical fuse electrically connected between said secondary coil and said secondary load, wherein said electrical fuse disconnects said secondary load from said secondary coil in response to a large transient.