ELECTRONIC BALLASTS FOR LIGHTING SYSTEMS

• US 20080180037A1
• Filed: 08/29/2007
• Published: 07/31/2008
• Est. Priority Date: 07/02/2007
• Status: Active Grant

• Current Assignee: Empower Electronics, Inc.
• Original Assignee: Empower Electronics, Inc.
• Inventors: Srimuang, Paul
• Granted Patent: US 7,911,153 B2
• Time in Patent Office: Days
• US Class Current: 315/246
• CPC Class Codes: H05B 41/295 with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
• CPC Class Codes: Y10S 315/05 Starting and operating circuit for fluorescent lamp

Abstract

A microprocessor controlled electronic ballast for lighting equipment is described wherein light level control is performed by varying the power provided to the light. Lighting power is adjusted by driving the lamp through a resonant circuit with a variable frequency power signal. The programmable microprocessor controls overall operation including preheating, ignition, and shutdown.

Claims

1. A ballast comprising:

a lamp control subsystem disposed to provide a lamp control signal;

a lamp drive subsystem disposed to receive said lamp control signal and provide a lamp drive signal; and

an output network disposed to receive said lamp drive signal and provide a lamp drive output signal.

2. The ballast of claim 1 wherein said lamp control subsystem comprises:

a ballast control circuit for providing said lamp control signal;

a processor operatively coupled to said ballast control circuit; and

a memory, operatively coupled to said processor, said memory configured to store processor readable logical instructions wherein execution of the logical instructions by the processor results in the performing of at least the following operations;

controlling a predefined lamp ignition sequence;

determining whether a lamp operatively connected to said ballast has ignited; and

based on said determining controlling, in part, operation of said lamp.

3. The ballast of claim 2 wherein said execution of the logical instructions by the processor further results in the performing of the following operation:

based on said determining, turning off operation of said ballast.

4. The ballast of claim 1 wherein said lamp control subsystem comprises a phase control circuit disposed to maintain said lamp drive output signal at a user-selectable output power level.

5. The ballast of claim 4 wherein said phase control circuit is disposed to measure the phase between the voltage and current of said lamp drive output signal and adjust the frequency of said lamp drive output signal to maintain said user-selectable output power level;

wherein said user selectable output power level is related to said phase between said voltage and current.

6. The ballast of claim 4 wherein said user-selectable output power level is set by a lamp power level signal provided to said lamp control subsystem.

7. The ballast of claim 6 further comprising an isolation circuit disposed to receive a lamp power level input signal and provide said lamp power level signal, said isolation circuit disposed to electrically isolate said lamp power level signal and said lamp power level input.

8. The ballast of claim 7 wherein said isolation circuit comprises an opto-isolation circuit.

9. The ballast of claim 7 wherein said lamp power level input signal comprises a square wave signal with a variable duty cycle, said duty cycle proportional to a user desired lamp power level.

10. The ballast of claim 1 further comprising a power supply subsystem, said power supply subsystem disposed to supply power to said lamp control subsystem and said lamp drive subsystem.

11. The ballast of claim 10 wherein said power supply subsystem comprises a flyback power supply disposed to provide one or more low level voltages to said lamp control subsystem and said lamp drive subsystem.

12. The ballast of claim 1 further comprising:

a power supply circuit disposed to receive power from an external power source and provide one or more voltage regulated power sources to said lamp control subsystem and lamp drive subsystem; and

a power factor correction module disposed to provide a substantially constant input power factor to said external power source.

13. The ballast of claim 1 wherein said lamp drive subsystem comprises a pair of MOSFET transistors disposed to generate said lamp drive signal.

14. The ballast of claim 1 wherein said output network comprises a resonant tuned circuit.

15. The ballast of claim 14 wherein said resonant tuned circuit comprises an L-C circuit.

16. The ballast of claim 2 wherein said execution of the logical instructions by the processor further results in the performance of the following operation:

adjusting the frequency of an output signal provided by a voltage controlled oscillator within said lamp control subsystem to vary said lamp control signal so as to prevent premature lamp ignition at startup of a lamp operatively connected to said ballast.

17. The ballast of claim 2 wherein said execution of the logical instructions by the processor further results in the performance of the following operation:

determining whether a lamp connected to said ballast is in an active oscillating state; and

based on said determining, latching said ballast in an off state.

18. The electronic ballast of claim 2 wherein said circuit for providing said lamp control signal comprises a ballast control IC;

said ballast control IC operatively coupled to said processor.

19. The ballast of claim 18 further comprising a delay circuit operatively connected to said processor and said ballast control IC, said delay circuit configured to provide a gradual transition of the frequency of said lamp control signal after ignition of a lamp connected to said ballast.

20. The ballast of claim 18 wherein said execution of the logical instructions by the processor further results in the performance of the following operations:

determining, during a lamp ignition cycle, whether said ballast control IC is in an oscillating state; and

based on said determining, restarting said ballast control IC if said ballast control IC is not in an oscillating state.

21. The ballast of claim 20 wherein said operations of determining and restarting are repeated up to a predefined number of times.

22. A method of providing electrical power to a lamp comprising:

receiving an adjustable power level signal;

providing an AC lamp drive signal to a reactive output network;

measuring the phase difference between a voltage and current of said AC lamp drive signal at said reactive output network; and

adjusting a frequency of said AC lamp drive signal to maintain an adjustable phase difference between said voltage and current, said adjustable phase difference being based on said adjustable power level signal.

23. A method for starting a lamp using a ballast, comprising:

performing a predefined ignition cycle;

determining if said lamp has ignited;

performing, after a predefined time period said predefined ignition cycle if said lamp has not ignited; and

placing said ballast in a latched shutdown state if said lamp has not ignited.

24. The method of claim 23 further comprising repeating to the extent said lamp has not ignited, said predetermined ignition cycle up to a predetermined number of times.

25. A lighting system comprising:

a HID lamp; and

a ballast comprising;

a lamp control subsystem disposed to provide a lamp control signal;

a lamp drive subsystem disposed to receive said lamp control signal and provide a lamp drive signal; and

an output network disposed to receive said lamp drive signal and provide a lamp drive output signal.

26. The lighting system of claim 25 wherein said lamp control subsystem comprises:

a ballast control circuit for providing said lamp control signal;

a processor operatively coupled to said ballast control circuit; and

a memory, operatively coupled to said processor, said memory configured to store processor readable logical instructions wherein execution of the logical instructions by the processor results in the performing of at least the following operations;

controlling a predefined lamp ignition sequence;

determining whether a lamp operatively connected to said ballast has ignited; and

based on said determining controlling, in part, operation of said lamp.