Dimming control circuit

• US 5,323,088 A
• Filed: 05/11/1993
• Issued: 06/21/1994
• Est. Priority Date: 09/13/1991
• Status: Expired due to Term

• Current Assignee: Gregory Esakoff
• Original Assignee: Gregory Esakoff
• Inventors: Cunningham, David W.
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): Philogene, Haissa
• Application Number:
  US08/063,839
• Time in Patent Office: 406 Days
• Field of Search: 315/294, 315/195, 315/198, 315/205, 315/250, 315/252, 315/313, 315/314, 315/315, 315/312, 315/324, 315/295, 315/296, 315/297, 315/199, 315/291, 315/DIG. 4
• US Class Current: 315/195
• CPC Class Codes: H02M 5/257 using semiconductor devices only
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A dimming control circuit for a plurality of lighting fixtures includes a separate semiconductor power switch, e.g., a silicon-controlled rectifier or SCR, for providing controlled amounts of pulsed, unidirectional electrical current to each lighting fixture. In one embodiment, a pair of SCRs, arranged in parallel, opposed relationship, are controllably pulsed to produce an alternating sequence of positive and negative electrical current pulses, of independently-controlled duration, and oppositely-conducting diodes then connect these SCRs to two separate lighting fixture. One such lighting fixture thus receives the positive current pulses, and the other such lighting fixture thus receives the negative current pulses. In an alternative embodiment, each lighting fixture receives pulsed, unidirectional current directly from a separate, independently-controlled SCR.

Claims

1. A dimming control circuit for a plurality of lighting fixtures, comprising:

an ac power source for supplying ac electrical power in an alternating series of positive and negative half cycles;

a plurality of semiconductor power switches having a plurality of control electrodes, wherein the plurality of semiconductor power sources are connected between the ac power source and a plurality of lighting fixtures, and wherein the plurality of semiconductor power switches are arranged in one or more switch pairs, each switch pair providing electrical current for two associated lighting fixtures, and each switch pair including

first and second switchable semiconductor devices arranged in parallel, opposed relationship,

a first diode, connected between the first and second switchable semiconductor devices and a first of the two associated lighting fixtures and adapted to couple electrical current only in a positive direction through the first lighting fixture, and

a second diode, connected between the first and second switchable semiconductor devices and a second of the two associated lighting fixtures and adapted to couple electrical current only in a negative direction through the second lighting fixture;

phase control signal generator means for generating a plurality of independent control pulse signals for coupling to the control electrodes of the plurality of power switches, to condition each switch to couple a selected amount of electrical current in a single direction, positive or negative, through an associated lighting fixture, each lighting fixture receiving electrical current only via switch; and

a central housing for housing the first and second switchable semiconductor devices of each switch pair of the plurality of semiconductor power switches and for housing the phase control signal generator means;

wherein the plurality of lighting fixtures are located remote from the central housing; and

wherein the first and second diodes of each switch pair of the plurality of semiconductor power switchers are located remote from the central housing, at or near their associated first and second lighting fixtures.

2. A dimming control circuit as defined in claim 1, wherein said switchable semiconductor device is a silicon-controlled rectifier.

3. A dimming control circuit as defined in claim 1, and further including a circuit breaker and choke connected in series with the ac power source and the semiconductor switch means.

4. A dimming control circuit as defined in claim 1, wherein:

the ac electrical power supplied by the ac power source has a predetermined fundamental frequency; and

the plurality of independent control signals generated by the phase control signal generator means have a fundamental frequency the same as the predetermined fundamental frequency of the ac electrical power.

14. A dimming control circuit as defined in claim 1, wherein:

the first and second switchable semiconductor devices of each switch pair each include a control electrode;

the control electrodes of the first and second switchable semiconductor devices of each switch pair are electrically connected to each other; and

the phase control signal generator means generates first and second control pulse signals for the respective first and second switchable semiconductor devices of each switch pair and applies such first and second control pulse signals to the control electrodes of both the first and the second switchable semiconductor devices.

5. A dimming control circuit for lighting fixtures, comprising:

an ac power source for supplying ac electrical power in an alternating series of positive and negative half cycles;

a first switchable semiconductor device for conducting electrical current from the ac power source in a positive direction to a first lighting fixture, the first switchable semiconductor device having a control electrode;

a second switchable semiconductor device for conducting electrical current to the ac power source in a negative direction from a second lighting fixture, the second switchable semiconductor device having a control electrode;

wherein the first and second switchable semiconductor devices are connected in parallel, opposed relationship with each other;

a first diode connected between the first switchable semiconductor device and the first lighting fixture and adapted to conduct electrical current in a positive direction to the first lighting fixture;

a second diode connected between the second switchable semiconductor device and the second lighting fixture and adapted to conduct electrical current in a negative direction from the second lighting fixture; and

phase control signal generator means for generating independent first and second control signals for connection to the control electrodes of the first and second switchable semiconductor devices;

wherein the first control signal is selected to condition the first switchable semiconductor device to a conductive state and thereby to couple electrical current through the first lighting fixture, only during the positive half cycles of the ac electrical power, via the first switchable semiconductor device and the first diode;

and wherein the second control signal is selected to condition the second switchable semiconductor device to a conductive state, and thereby to couple such that electrical current through the second lighting fixture, only during the negative half cycles of the ac electrical power, via the second switchable semiconductor device and the second diode.

6. A dimming control circuit as defined in claim 5, wherein:

the dimming control circuit further includes a central housing for housing the first and second switchable semiconductor devices and for housing the phase control signal generator means;

the first and second lighting fixtures are located remote from the central housing; and

the first and second diodes are located remote from the central housing, at or near the respective first and second lighting fixtures.

7. A dimming control circuit as defined in claim 5, wherein the first and second switchable semiconductor devices are silicon-controlled rectifiers.

8. A dimming control circuit as defined in claim 5, and further including a choke and a circuit breaker connected in series with the ac power source and the semiconductor switch means.

9. A dimming control circuit as defined in claim 5, wherein:

the ac electrical power supplied by the ac power source has predetermined fundamental frequency; and

the plurality of independent control signals generated by the phase control signal generator means have a fundamental frequency the same as the predetermined fundamental frequency of the ac electrical power.

15. A dimming control circuit as defined in claim 5, wherein:

the control electrodes of the first and second switchable semiconductor devices are electrically connected to each other; and

the phase control signal generator means applies the first and second control signals to the control electrodes of both the first and the second switchable semiconductor devices.

10. A dimmable lighting system comprising:

an ac power source for supplying ac electrical power in an alternating series of positive and negative half cycles;

a first lighting fixture;

a second lighting fixture associated with the first lighting fixture;

a first switchable semiconductor device, connected between the ac power source and the first lighting fixture, for coupling electrical current only in a positive direction through the first lighting fixture, wherein the first switchable semiconductor device has a control electrode and is free of any parallel-connected switchable semiconductor device adapted to conduct current is negative direction, opposite the positive direction;

a second switchable semiconductor device, connected between the ac power source and the second lighting fixture, for coupling electrical current only in a negative direction through the second lighting fixture, wherein the second switchable semiconductor device has a control electrode and is free of any parallel-connected switchable semiconductor device adapted to conduct current in a positive direction, opposite the negative direction;

a housing for housing the first and second switchable semiconductor devices;

a single, multiple-conductor power line for coupling electrical current from the ac power source to the housing for the first and second switchable semiconductor devices; and

phase control signal generator means for generating a first control signal for coupling to the control electrode of the first switchable semiconductor device, to condition the first switchable semiconductor device to couple a selected amount of electrical current through the first lighting fixture, the first lighting fixture receiving electrical current only via the first switchable semiconductor device, the phase control signal generator means further generating a second control signal, independent of the first control signal, for coupling to the control electrode of the second switchable semiconductor device, to condition the second switchable semiconductor device to couple a selected amount of electrical current in a negative direction through the second lighting fixture, the second lighting fixture receives electrical current only via the second switchable semiconductor device.

11. A dimmable lighting system as defined in claim 10, wherein the first switchable semiconductor device is a silicon-controlled rectifier.

12. A dimmable lighting system as defined in claim 10, and further including a circuit breaker and choke connected in series with the ac power source and the first switchable semiconductor device.

13. A dimmable lighting system as defined in claim 10, wherein:

the ac electrical power supplied by the ac power source has a predetermined fundamental frequency; and

the plurality of independent control signals generated by the phase control signal generator means have a fundamental frequency the same as the predetermined fundamental frequency of the ac electrical power.

16. A dimmable lighting system as defined in claim 10 wherein:

the control electrodes of the first and second switchable semiconductor devices are electrically connected to each other without any intervening components; and

the phase control signal generator means applies the first and second control signals to the control electrodes of both the first and the second switchable semiconductor devices.

17. A dimming control circuit for a plurality of lighting fixtures, comprising:

switching circuit means connected to an ac power source for controllably providing on a power line current pulses of a first selected duration of the positive half cycles of the ac power source and for controllably providing on the same power line current pulses of a second selected duration, independent of the first selected duration, of the negative half cycles of the ac power source; and

first and second oppositely-poled diodes connected between the power line of the switching circuit means and the first and second lighting fixtures, respectively, such that the power supplied to the first and second lighting fixtures is independently controlled.

18. A dimming control circuit as defined in claim 17, wherein:

the switching circuit means includes first and second silicon-controlled rectifiers connected in parallel, opposed relationship; and

the switching circuit means includes a controller for generating independent first and second control pulse signals for application to the first and second silicon-controlled rectifiers.

19. A dimming control circuit as defined in claim 18, wherein:

the first and second silicon-controlled rectifiers each include a control electrode;

the control electrodes of the first and second silicon-controlled rectifiers are electrically connected to each other; and

the controller applies the first and second control pulse signals to the control electrodes of both the first and second silicon-controlled rectifiers.

20. A dimming control method for a plurality of lighting fixtures, comprising the steps of:

connecting a switching circuit to an ac power source for controllably providing on a power line current pulses of a first selected duration of the positive half cycles of the ac power source and for controllably providing on the same power line current pulses of a second selected duration, independent of the first selected duration, of the negative half cycles of the ac power source;

coupling the power line of the pulses of the positive and negative half cycles of the switching circuit to first and second, oppositely-poled diodes; and

connecting the first and second diodes to first and second lighting fixtures, respectively, such that the power supplied to the first and second lighting fixtures is independently controlled.

21. A dimming control method as defined in claim 20, wherein the step of connecting a switching circuit includes the steps of:

connecting first and second silicon-controlled rectifiers in parallel, opposed relationship and

providing first and second control pulse signal for independently switching the respective first and second silicon-controlled rectifiers on and off.

22. A dimming control method as defined in claim 21, wherein:

the step of connecting first and second silicon-controlled rectifiers in parallel, opposed relationship includes a step of electrically connecting together the control electrodes of such first and second silicon-controlled rectifiers; and

the step of providing first and second control pulse signals includes a step of applying the first and second control pulse signals to the control electrodes of both the first and the second silicon-controlled rectifiers.