Automatic light dimmer for gas discharge lamps

• US 6,329,767 B1
• Filed: 04/25/2000
• Issued: 12/11/2001
• Est. Priority Date: 12/17/1991
• Status: Expired due to Term

• Current Assignee: Taylor Dunham LLP (Taylor Dunham and Rodriguez LLP)
• Original Assignee: Richard L. Sievers
• Inventors: Sievers, Richard L.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US09/558,317
• Time in Patent Office: 595 Days
• Field of Search: 315/DIG.4, 315/205, 315/194, 315/276, 315/307, 315/158, 315/159, 315/360
• US Class Current: 315/307
• CPC Class Codes: H05B 41/2853 against abnormal power supply conditions
• CPC Class Codes: H05B 41/288 with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps H05B41/2806 takes precedence
• CPC Class Codes: H05B 41/38 Controlling the intensity of light
• CPC Class Codes: H05B 41/382 during the transitional start-up phase
• CPC Class Codes: H05B 41/386 for speeding-up the lighting-up
• CPC Class Codes: H05B 41/3922 and measurement of the incident light
• CPC Class Codes: H05B 41/3924 by phase control, e.g. using a triac H05B41/3922 takes precedence
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A power saving dimming apparatus for gas discharge lamps activates a system of gas discharge lamps through a phototransistor network sensitive to the infrared spectrum rather than the normal visible spectrum. The phototransistor network allows power to be supplied to the apparatus, resulting in the turning on of the lamps whenever daylight conditions exist which are insufficient to produce infrared light. When power is applied to the apparatus, either at initial turn on or after a momentary interruption, the apparatus applies full power to the primaries of the lamp ballasts for a preselected time period, thus ensuring all the lamps in the system light. After the preselected time period has passed, the apparatus automatically dims the lamps and maintains them in the dimmed state.

Claims

1. A power saving dimming apparatus for gas discharge lamps, comprising:

first means in response to a first set of control signals for applying an entire voltage waveform of an AC supply voltage to the ballasts of a plurality of said lamps upon the initial application or the momentary interruption of power to said dimming apparatus; and

second means for applying a minimum portion of each half-cycle of said AC supply voltage to said lamp ballasts, wherein said second means progressively reduces said AC supply voltage applied to said lamp ballasts from said entire voltage waveform to said minimum portion of each half-cycle in response to a second set of control signals.

2. The dimming apparatus according to claim 1 further comprising control means for generating said first and second set of control signals coupled to said first and second means.

3. The dimming apparatus according to claim 2 wherein said control means comprises a decade counter that sequentially generates a set of high output signals which serve as said first and second set of control signals.

4. The dimming apparatus according to claim 3 wherein said control means further comprises a timer for supplying a clock signal to said decade counter.

5. The dimming apparatus according to claim 1 wherein said second means progressively reduces said AC supply voltage from said entire voltage waveform to said minimum portion of each half-cycle in a step-wise reduction.

6. The dimming apparatus according to claim 1 wherein said second means progressively redudes said AC supply voltage from said entire voltage waveform to said minimum portion of each half-cycle in a continuous reduction.

7. The dimming apparatus according to claim 1 further comprising a phototransistor network for turning on said dimming apparatus in the absence of sufficient light and turning off said dimming apparatus in the presence of sufficient light.

8. The dimming apparatus according to claim 7 wherein said phototransistor network comprises a phototransistor which activates in the absence of infrared light and deactivates in the presence of infrared light.

9. The dimming apparatus according to claim 2 further comprising means for locking said control means with said first set of control signals actuated to continuously maintain said first means activated so that said entire voltage waveform of said AC supply voltage is applied to said lamps ballasts.

10. The dimming apparatus according to claim 2 further comprising power supply means for supplying power to said dimming apparatus.

11. The dimming apparatus according to claim 1, wherein said first means comprises an optically isolated triac driver coupled to a pair of SCRs connecting said lamp ballasts to said AC supply voltage, wherein said optically isolated triac driver actuates said SCRs in response to said first set of control signals to deliver said entire voltage waveform of said AC supply voltage to said lamp ballasts.

12. The dimming apparatus according to claim 11, wherein said second means, comprises:

a triac coupled to the gate of each of said SCRs;

a diac coupled to the gate of said triac; and

a timing capacitor coupled to said diac and said AC supply voltage through a resistor network, wherein said timing capacitor activates said diac when it charges to the breakover voltage of said diac, and further wherein sequential stages of said resistor network are coupled to said timing capacitor in response to said second set of control signals in order to step-wise increase the charging time of said timing capacitor.

13. The dimming apparatus according to claim 12, wherein said resistor network includes a potentiometer which permits manual adjustment of the charging time of said timing capacitor.

14. The dimming apparatus according to claim 11, wherein said second means, comprises:

a triac coupled to the gate of each of said SCRs;

a unijunction transistor coupled to the gate of said triac,

a first capacitor coupled to the emitter of said unijunction transistor and to the output of a bridge rectifier, wherein said first capacitor activates said unijunction transistor when it charges to the firing voltage of said unijunction transistor; and

a second capacitor coupled to said first capacitor, wherein said second capacitor discharges into said first capacitor in response to said second set of control signals in order to initially decrease the charging time of said first capacitor, and further wherein as said second capacitor discharges, the charging time of said first capacitor continuously increases to a maximum level.

15. The dimming apparatus according to claim 14, wherein said second means further comprises a potentiometer coupled to said first capacitor which permits the manual adjustment of the charging time of said first capacitor.

16. The dimming apparatus according to claim 1 wherein in response to the deactivation of said second set of control signals, said second means transfers control of the application of said AC supply voltage to said lamp ballasts to an auxiliary power reducing transformer to maintain a high power factor and reduced harmonics.