Power stealing solid state switch

• US 6,288,458 B1
• Filed: 09/30/1999
• Issued: 09/11/2001
• Est. Priority Date: 09/30/1999
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Berndt, Dale F.
• Primary Examiner(s): Jackson, Stephen W.
• Assistant Examiner(s): POLK, SHARON A
• Application Number:
  US09/408,638
• Time in Patent Office: 712 Days
• Field of Search: 307/39, 307/130, 307/131, 307/126, 250/551, 219/492, 323/282, 323/322
• US Class Current: 307/130
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A mechanically actuated power stealing solid state low energy switch providing a drop-in replacement for low energy mechanical switches. The present switch eliminates disadvantages of the mechanical switches. Power stealing is done on a constant basis to eliminate spikes, which might interfere with digital logic. Stealing logic with no diode drops allows low power operation on single CMOS substrate and omni-directional hook-up of a power supply with the most negative voltage being directed to the substrate. Hysteresis for the solid state switch is provided to mimic mechanical switch operation but without chatter of the latter.

Claims

1. A solid state switch comprising:

a variable capacitor sensor;

a comparator, having hysteresis, coupled to said variable capacitor sensor;

a logic circuit in electrical communication with said comparator;

a power stealing circuit in electrical communication with said logic circuit; and

an output control circuit in electrical communication with said logic circuit and said power stealing circuit.

2. The switch of claim 1, further comprising:

a common terminal in electrical communication with said output control circuit;

a normally closed terminal in electrical communication with said output control circuit; and

a normally opened terminal in electrical communication with said output control circuit.

3. The switch of claim 2, further comprising:

a clamped voltage control circuit in electrical communication with said output control circuit;

a voltage logic buss in electrical communication with said variable capacitor sensor, said comparator, said logic circuit, said power stealing circuit and said output control circuit;

a charge pump in electrical communication with said clamped voltage control circuit and to said voltage logic buss; and

a voltage regulator in electrical communication with said voltage logic buss.

4. The switch of claim 3, wherein said power stealing circuit has less than two diode drops.

5. The switch of claim 3, wherein said charge pump operates on a very low voltage and outputs a much higher voltage sufficient to operate the solid state switch.

6. The switch of claim 5, wherein:

said power stealing circuit seeks out a most negative terminal among the common terminal, the normally closed terminal and the normally open terminal; and

said power stealing circuit seeks out a most positive terminal among the common terminal, the normally closed terminal and the normally open terminal.

7. The switch of claim 6, wherein the hysteresis of said comparator mimics a differential travel of a mechanical switch.

8. The switch of claim 7, wherein said logic circuit can determine whether the switch is to operate in a two- or three-terminal mode.

9. The switch of claim 8, wherein:

said logic circuit opens the switch in the two terminal mode if an amount of current flowing through the switch exceeds a predetermined maximum magnitude; and

said logic circuit limits the amount of current flowing through the switch in the three terminal mode to the predetermined maximum magnitude.

10. The switch of claim 8, wherein said power stealing circuit can function independent of voltage polarity in the two-terminal mode or the three-terminal mode.

11. The switch of claim 10, further comprising a mechanical plunger that can affect said variable capacitor sensor to actuate the switch.

12. The switch of claim 11, wherein said logic circuit provides the switch with break-before-make timing.

13. A solid state switch comprising:

an actuator;

a logic circuit coupled to said actuator;

a power stealing circuit coupled to said actuator and said logic circuit; and

a power output circuit in electrical communication with said logic circuit and said power stealing circuit; and

wherein;

said power output circuit is in electrical communication with at least two terminals; and

said power stealing circuit provides power to the switch from terminals of the switch.

14. The switch of claim 13, further comprising a charge pump for providing an appropriate voltage for the switch from a source of voltage of about 0.5 volt.

15. The switch of claim 14, wherein said actuator provides a mechanical-to-electrical actuation of the switch.

16. The switch of claim 15, wherein said switch is polarity independent.

17. The switch of claim 16, wherein said switch can operate in a two- or three-wire mode.

18. The switch of claim 17, wherein said logic circuit provides for break-before-make timing.

19. A solid state switch comprising:

actuator means for providing mechanical-to-electrical actuation, having electrical hysteresis;

logic means, coupled to said actuator means, for providing break before make timing of the switch;

output means, coupled to said logic means, for making and breaking contact;

terminal means, coupled to said output means, for coupling to an external circuit to be switched by said output means; and

stealing means, coupled to said logic means, output means and terminal means, for obtaining power from the external circuit via said terminal means.

20. The switch of claim 19, further comprising:

voltage buss means, coupled to said actuator means, said logic means, said output means, and said stealing means, for carrying power to said means;

pump means, coupled to said voltage buss means and said terminal means, for converting electrical power having a voltage insufficient for said voltage buss means to electrical power having a voltage sufficient for said voltage buss means;

regulating means, coupled to said voltage buss means and to said stealing means, for taking electrical power from said stealing means and converting it to electrical power having a regulated voltage for said voltage means; and

selection means, coupled to said voltage buss means, said pump means, and said regulating means, for selecting a source of power for said voltage buss means from said pump means or said regulating means.