Three wire air gap off power supply circuit for operating switch and regulating current when switch or load is open

• US 5,777,837 A
• Filed: 07/13/1995
• Issued: 07/07/1998
• Est. Priority Date: 02/02/1995
• Status: Expired due to Term

• Current Assignee: Hubbell, Inc.
• Original Assignee: Hubbell, Inc.
• Inventors: Batko, Thomas James, Eckel, David Philip
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US08/501,850
• Time in Patent Office: 1,090 Days
• Field of Search: 361/153, 361/160, 361/170, 307/126, 307/140, 307/116, 307/154, 307/157, 307/326, 307/327, 307/328, 307/125, 307/65, 315/91-93, 315/135, 315/136, 315/174, 315/175, 315/205, 315/207, 315/272, 315/273, 315/352, 315/353, 315/86, 323/245, 340/333
• US Class Current: 361/160
• CPC Class Codes: H01H 47/007 with galvanic isolation between controlling and controlled circuit, e.g. transformer relay
• CPC Class Codes: H05B 41/16 in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/13 by using passive infrared detectors
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A three wire power supply circuit is provided for selectively connecting and disconnecting a load from an alternating current power source having neutral, line and ground conductors. The load is connected to the neutral conductor. The power supply circuit is provided with a relay connected at one terminal to the load and at another terminal to the line conductor, a control circuit connected to the relay and operable to open and close the relay, a first rectifier circuit connected in parallel with the relay and operable to supply as much as full line power to the control circuit when the relay is open, and a second rectifier circuit connected at one terminal to the line conductor and connected at another terminal to the ground conductor. The second rectifier circuit is operable to supply power to the control circuit regardless of the position of the relay. An air gap switching mechanism is connected to the relay and the control circuit and operable to open the relay when the air gap switching mechanism is activated. The power supply circuit is operable to provide pulsed power versus steady state power to selected circuit components that require more power than that available via a regulated supply.

Claims

1. A power supply circuit for selectively connecting and disconnecting a load from an alternating current power source having neutral, line and ground conductors, said load being connected to said neutral conductor and to said power supply circuit via a load conductor, said power supply circuit comprising:

a relay connected at one terminal thereof to said load conductor and connected at another terminal thereof to said line conductor;

a control circuit connected to said relay and operable to open and close said relay;

a first rectifier circuit connected in parallel with said relay and operable to supply as much as full line power to said control circuit when said relay is open; and

a second rectifier circuit connected at one terminal thereof to said line conductor and connected at another terminal thereof to said ground conductor, said second rectifier circuit being operable to supply power to said control circuit.

2. A power supply circuit as claimed in claim 1, wherein said first rectifier circuit comprises a bridge rectifier and a capacitor connected in series with respect to each other and in parallel with respect to said relay, said bridge rectifier being connected to said line conductor at a first terminal, to said capacitor at a second terminal, and to said control circuit at third and fourth terminals thereof.

3. A power supply circuit as claimed in claim 1, wherein said second rectifier circuit comprises a bridge rectifier in series with at least one resistor.

4. A power supply circuit as claimed in claim 1, wherein said second rectifier circuit is configured to limit current from said line conductor to said ground conductor to a predetermined maximum current level.

5. A power supply circuit as claimed in claim 1, further comprising an air gap switch connected to said line conductor and operable to interrupt the current path from said power source to said load when open.

6. A power supply circuit as claimed in claim 1, wherein said control circuit comprises:

a resistor connected to said first rectifier circuit;

a capacitor connected to said resistor;

a switch connected in parallel with said resistor and having substantially less impedance when activated; and

a processor circuit to selectively activate said switch to shunt said resistor and charge said capacitor.

7. A power supply circuit as claimed in claim 6, wherein said processor circuit is programmable to activate said switch in accordance with at least one of a group of conditions consisting of a fixed duty cycle, a varying duty cycle, random intervals, and following operation of said relay.

8. A power supply circuit as claimed in claim 6, further comprising an indicator, said processor circuit being programmable to activate said switch in response to operation of said indicator.

9. A power supply circuit as claimed in claim 6, wherein said processor circuit is programmable to activate said switch to operate said relay.

10. A power supply circuit as claimed in claim 6, further comprising an air gap switch connected to at least one of said line conductor and said neutral conductor and operable to interrupt the current path from said power source to said load when open, said processor circuit being programmable to activate said switch to operate said air gap switch.

11. A power supply circuit as claimed in claim 1, wherein said control circuit comprises:

a resistor connected to said second rectifier circuit;

a capacitor connected to said resistor;

a switch connected in parallel with said resistor and having substantially less impedance when activated; and

a processor circuit to selectively activate said switch to shunt said resistor and to charge said capacitor.

12. A power supply circuit as claimed in claim 11, wherein said processor circuit is programmable to activate said switch in accordance with at least one of a group of conditions consisting of a fixed duty cycle, a varying duty cycle, random intervals, and following operation of said relay.

13. A power supply circuit as claimed in claim 11, further comprising an indicator, said processor circuit being programmable to activate said switch in response to operation of said indicator.

14. A power supply circuit as claimed in claim 11, wherein said processor circuit is programmable to activate said switch to operate said relay.

15. A power supply circuit as claimed in claim 11, further comprising an air gap switch connected to at least one of said line conductor and said neutral conductor and operable to interrupt the current path from said power source to said load when open, said processor circuit being programmable to activate said switch to operate said air gap switch.

16. A power supply circuit as claimed in claim 1, further comprising an air gap switch connected to said neutral conductor and operable to interrupt the current path from said power source to said load when open.

17. A power supply circuit as claimed in claim 1, further comprising a switch connected in series with said relay and said line conductor, and an air gap off detection circuit connected to said switch when said switch is open and to said control circuit, said air gap off detection circuit being operable to close said relay when said switch is open.

18. A power supply circuit as claimed in claim 17, wherein said switch comprises a first set of contacts connected in series with said relay, and a second set of contacts connected in series with said second rectifier circuit, said switch being operable to disconnect said power supply circuit from said power source when open, said air gap off detection circuit being operable to detect decreasing voltage and to open said relay in response thereto.

19. A power supply circuit as claimed in claim 17, further comprising a third rectifier connected between said switch and said load when said switch is open, said air gap off detection circuit being operable to detect increasing voltage and to open said relay in response thereto when said switch is open.

20. A power supply circuit as claimed in claim 1, further comprising a switch connected in series with said first rectifier circuit and in parallel with said relay, and an air gap off detection circuit connected to said switch when said switch is open and to said control circuit, said air gap off detection circuit being operable to open said relay when said switch is open.

21. A power supply circuit as claimed in claim 20, wherein said switch comprises a first set of contacts connected in series with said first rectifier circuit and in parallel with said relay, and a second set of contacts connected in series with said second rectifier circuit, said switch being operable to disconnect said power supply circuit from said power source when open, said air gap off detection circuit being operable to detect decreasing voltage and to open said relay in response thereto.

22. A power supply circuit as claimed in claim 20, further comprising a third rectifier connected between said switch and said load when said switch is open, said air gap off detection circuit being operable to detect increasing voltage when said switch is open and to open said relay in response thereto.

23. A power supply circuit as claimed in claim 1, further comprising a variable impedance circuit element connected in series with said second rectifier circuit and said ground conductor, said control circuit being operable to control the amount of impedance across said variable impedance circuit element.

24. A power supply circuit as claimed in claim 23, wherein said control circuit comprises at least one of a plurality of control elements comprising a processor circuit and a potentiometer.

25. A power supply circuit as claimed in claim 23, wherein said variable impedance circuit element is a thyristor and said control circuit comprises a processor circuit and a gate drive circuit, said gate drive circuit being connected in parallel with said thyristor and controllable by said processor circuit.

26. A power supply circuit as claimed in claim 23, further comprising a switch in series with said variable impedance circuit element, and a resistor connected in parallel with said switch and said variable impedance circuit element, said control circuit comprising a processor circuit which is operable to close said switch and increase and decrease the impedance of said variable impedance circuit element with respect to the impedance of said resistor.

27. A power supply circuit as claimed in claim 1, further comprising a variable impedance circuit element connected in series with said first rectifier circuit and said load, said control circuit being operable to control the amount of impedance across said variable impedance circuit element.

28. A power supply circuit as claimed in claim 27, wherein said control circuit comprises at least one of a plurality of control elements comprising a processor circuit and a potentiometer.

29. A power supply circuit as claimed in claim 27, wherein said variable impedance circuit element is a thyristor and said control circuit comprises a processor circuit and a gate drive circuit, said gate drive circuit being connected in parallel with said thyristor and controllable by said processor circuit.

30. A power supply circuit as claimed in claim 27, further comprising a switch in series with said variable impedance circuit element, and a resistor connected to said first rectifier circuit and providing a parallel path with respect to said switch and said variable impedance circuit element, said control circuit comprising a processor circuit which is operable to close said switch and increase and decrease the impedance of said variable impedance circuit element with respect to the impedance of said resistor.

31. A power supply circuit as claimed in claim 1, wherein said control circuit comprises a processor circuit and further comprising a switch connected to said processor, said processor being operable to detect when said switch is activated and to open said relay in response thereto.

32. A power supply circuit as claimed in claim 31, wherein said switch comprises one set of contacts connected to said processor circuit and another set of contacts connected in series with said first rectifier circuit, said processor being operable to detect a voltage drop across said first rectifier circuit when said switch is open.

33. A power supply circuit as claimed in claim 1, further comprising a resistor connected to said second rectifier circuit, a capacitor connected in series with said resistor, a transistor connected across said resistor, said control circuit being operable to gate said transistor to decrease the impedance across said resistor and charge said capacitor.

34. A power supply circuit as claimed in claim 1, wherein said control circuit comprises a processor circuit, and further comprising a capacitor and at least one switch connected to said processor circuit, said processor circuit being operable to control the flow of current to said capacitor via said first rectifier circuit and said at least one switch.

35. A power supply circuit as claimed in claim 1, further comprising a first ground circuit connected to at least one of said load and said first rectifier circuit and a second ground circuit connected to at least one of said ground conductor and said second rectifier circuit to provide first and second ground return paths, respectively.

36. A power supply circuit as claimed in claim 1, further comprising a voltage detection circuit connected to said first rectifier circuit, and an air gap switch connected to at least one of said line conductor and said load conductor, said voltage detection circuit being operable to detect a decrease in voltage when said relay is open and said load is open and to open said air gap switch to interrupt current flow to said load in response thereto.