Title: Dimming circuit with saturated semiconductor device

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Claims: The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; said source of electric power including an a-c source and a d-c converter connected to said a-c source; said oscillator circuit means and said transistor and lamp being driven from the d-c output of said d-c converter.

2. The energizing circuit of claim 1 which further includes a coupling transformer having first and second winding portions; said first and second winding portions being connected in closed series relation with one another and with said gas discharge lamp; said first winding portion being connected in a closed series relation with said source of electric power and said emitter and collector electrodes of said transistor and in parallel with the series connection of said second winding portion and said gas discharge lamp.

3. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; a coupling transformer having first and second winding portions; said first and second winding portions being connected in closed series relation with one another and with said gas discharge lamp; said first winding portion being connected in closed series relation with said source of electric power and said emitter and collector electrodes of said transistor and in parallel with the series connection of said second winding portion and said gas discharge lamp.

4. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; a dimming control circuit means for controlling the output light of said lamp; said dimming control means comprising control means connected to said oscillator circuit means for varying the magnitude of said pulse current, whereby the output light of said lamp varies directly with said pulse current magnitude into the base of said transistor even though said transistor is always in saturation.

5. The energizing circuit of claim 4 wherein said transistor is always driven to saturation by said pulse current in said base of said transistor at the least magnitude of said pulse current within the range of dimming adjustment.

6. The energizing circuit of claim 5 wherein said gas discharge lamp is a very high output fluorescent lamp.

7. The energizing circuit of claim 4 wherein said pulse current has a pulse repetition frequency of from about 10 kilohertz to about 100 kilohertz.

8. The energizing circuit of claim 4 which further includes a coupling transformer having first and second winding portions; said first and second winding portions being connected in closed series relation with one another and with said gas discharge lamp; said first winding portion being connected in a closed series relation with said source of electric power and said emitter and collector electrodes of said transistor and in parallel with the series connection of said second winding portion and said gas discharge lamp.

9. The energizing circuit of claim 4 which further includes servo amplifier means connected in series with said gas discharge lamp and monitoring the current flow through said lamp; said servo amplifier means including output control circuit means connected to oscillator circuit means for varying the magnitude of said output current pulse into the base of said transistor, whereby a given current flow will be maintained in said lamp.

10. The energizing circuit of claim 9 wherein said dimming control circuit means is connected to said servo amplifier means and varies the adjustment magnitude of said given current, thereby to affect control of the light output of said lamp.

11. The energizing circuit of claim 10 wherein said dimming control circuit means includes an oscillating circuit for varying the light output of said lamp at a given frequency.

12. The energizing circuit of claim 9 wherein said transistor is always driven to saturation by said pulse current in said base of said transistor at the least magnitude of said pulse current within the range of dimming adjustment.

13. The energizing circuit of claim 10 which further includes overvoltage protection circuit means for preventing excessive voltage across the emitter-collector electrodes of said transistor by adjusting said pulse current magnitude to reduce tube current in response to excessive voltage on said transistor.

14. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; a servo amplifier means connected in series with said gas discharge lamp and monitoring the current flow through said lamp; said servo amplifier means including output control circuit means connected to said oscillator circuit means for varying the magnitude of said output current pulse into the base of said transistor, whereby a given current flow will be maintained in said lamp.

15. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; a second gas discharge lamp connected in parallel with said lamp and current balancing transformer means for connecting one end of each of said lamps together; the other ends of said lamps being directly connected to one another; and tap means on said current balancing transformer to define an output terminal for said parallel-connected lamps.

16. The energizing circuit of claim 15 wherein said parallel-connected lamps are disposed physically parallel to one another and are closely spaced to one another; the parallel currents in each of said lamps flowing in opposite directions.

17. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; said pulse current having a length less than about 30 microseconds, whereby said gas discharge lamp, which would normally have a negative resistance characteristic, operates as though it has a less negative resistance characteristic.

18. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; and an inductive impedance connected in series with said gas discharge lamp.

19. The circuit of claim 18 which further includes coupling transformer means having a winding connected across said gas discharge lamp.

20. An energizing circuit for a gas discharging lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes a transistor having base, collector and emitter electrodes; said source of electric power, said emitter and collector electrodes of said transistor and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said transistor to inject said pulse current into said base of said transistor; said pulse current having a minimum magnitude sufficiently high to drive said transistor into saturation; and coupling transformer means having a winding connected across said gas discharge lamp.

21. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes an electronic switching means having control terminal means, power output terminal means and power input terminal means; said source of electric power, said power output and power input terminal means of said electronic switching means and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said electronic switching means to inject said pulse current into said control terminal means of said electronic switching means; said pulse current having a minimum magnitude sufficiently high to render said electronic switching means fully conductive; and over-voltage protection circuit means for preventing excessive voltage across said power input and power output terminal means of said electronic switching means by adjusting said pulse current magnitude to reduce tube current in response to excessive voltage across said power input and power output terminal means.

22. The energizing circuit of claim 21 wherein said overvoltage protection circuit means includes first transistor circuit means having input and output terminals; said output terminals of said first transistor circuit means connected to said control terminal means; and second transistor circuit means having input and output terminals; said input terminals of said second transistor circuit means connected to said power output and input terminals; said output terminals of said second transistor circuit means connected to said input terminals of said first transistor circuit means whereby, when the voltage across said power input and output terminals exceeds a given value, the output signal at said output terminals of said second transistor circuit means changes in a direction to change the output of said output terminals of said first transistor circuit means to reduce the drive of said control terminal means.

23. The energizing circuit of claim 22 which further includes a diode means and capacitor means connected in said input terminals of said second transistor circuit means.

24. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of electric power, oscillator circuit means for producing a pulse current at a relatively high frequency, and a pulse modulator circuit which includes an electronic switching means having control terminal means, power output terminal means and power input terminal means; said source of electric power, said power output and power input terminal means of said electronic switching means and said gas discharge lamp being connected in series; said oscillator circuit means being connected to said electronic switching means to inject said pulse current into said control terminal means of said electronic switching means; said pulse current having a minimum magnitude sufficiently high to render said electronic switching means fully conductive; a second gas discharge lamp connected in predetermined circuit relation with said lamp and being simultaneously energized therewith; and current balancing means connected to said gas discharge lamps to ensure a predetermined division of electrical power between said gas discharge lamps.

25. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of d-c power, a pulse modulator for producing a high frequency pulse current output from said source of d-c power, and a coupling transformer means for coupling said pulse current output from said pulse modulator into said gas discharge lamp; said pulse current output having a pulse length sufficiently short that said gas discharge lamp which would normally have a negative resistance characteristic operates with a resistance characteristic which is less negative than said negative resistance characteristic, and wherein said coupling transformer means includes first and second winding portions; said first and second winding portions being connected in closed series relation with one another and with said gas discharge lamp; said first winding portion being connected in a closed series relation with said source of d-c power and said pulse modulator and in parallel with the series connection of said second winding portion and said gas discharge lamp.

26. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of d-c power, a pulse modulator for producing a high frequency pulse current output from said source of d-c power, and a coupling transformer means for coupling said pulse current output from said pulse modulator into said gas discharge lamp; said pulse current output having a pulse length sufficiently short that said gas discharge lamp which would normally have a negative resistance characteristic operates with a resistance characteristic which is less negative than said negative resistance characteristic, and wherein a second gas discharge lamp is connected in parallel with said lamp and current balancing transformer means for connecting one end of each of said lamps together; the other ends of said lamps being directly connected to one another; and tap means on said balancing transformer to define an output terminal for said parallel-connected lamps.

27. The energizing circuit of claim 26 wherein said parallel-connected lamps are disposed physically parallel to one another and are closely spaced to one another; the parallel currents in each of said lamps flowing in opposite directions.

28. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of d-c power, a pulse modulator for producing a high frequency pulse current output from said source of d-c power, and a coupling transformer means for coupling said pulse current output from said pulse modulator into said gas discharge lamp; said pulse current output haaving a pulse length sufficiently short that said gas discharge lamp which would normally have a negative resistance characteristic operates with a resistance characteristic which is less negative than said negative resistance characteristic, and servo amplifier means connected in series with said gas discharge lamp and monitoring the current flow through said lamp; said servo amplifier means including output control circuit means connected to said pulse modulator to maintain the magnitude of said current pulse to said lamp at a given adjustable value.

29. The energizing circuit of claim 28 which further includes dimmer circuit means connected to said servo amplifier means for varying the adjustment value of said pulse current magnitude.

30. An energizing circuit for a gas discharge lamp; said energizing circuit including a source of d-c power, a pulse modulator for producing a high frequency pulse current output from said source of d-c power, and a coupling transformer means for coupling said pulse current output from said pulse modulator into said gas discharge lamp; said pulse current output having a pulse length sufficiently short that said gas discharge lamp which would normally have a negative resistance characteristic operates with a resistance characteristic which is less negative than said negative resistance characteristic; dimming circuit means connected to said pulse modulator for adjustably controlling the magnitude of said pulse current output to maintain a given adjustment value; said pulse modulator including a power transistor having emitter and collector electrodes connected in series with said lamp; and a pulse current source connected to the base of said transistor for driving said transistor into saturation at a repetition rate of from about 10 kilohertz to about 100 kilohertz and for said short pulse length; said dimming circuit means including means for varying the magnitude of the pulse current injected into said base; said transistor always being driven into saturation over substantially the full range of dimming of said lamp.

31. The energizing circuit of claim 30 wherein said pulse length is less than about 30 microseconds.

Other info:

Inventors: Gray, George (Lambertville, NJ, US)

Application Number: 391953
Filing Date: 1973-08-27
Publication_date: 1976-02-03
Assignee: Lutron Electronics Co., Inc. (Coopersburg, PA)
Primary Class(es): 315/210 315/224, 315/276, 315/DIG4
Other Classes:
US Patent Ref:

3611024	Oct, 1971	Nakatsu et al.	315/DIG.
3619716	Nov, 1971	Spira	315/DIG.
3681654	Aug, 1972	Quinn	315/DIG.

Other Refs:
Primary Examiner: Heyman, John S.
Assistant Examiner: Davis, B. P.
Attorney: Ostrolenk, Faber, Gerb & Soffen