Power supply system for multiple loads and driving system for multiple lamps

• US 6,420,839 B1
• Filed: 04/05/2001
• Issued: 07/16/2002
• Est. Priority Date: 01/19/2001
• Status: Active Grant

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Ambit Microsystems Corporation (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chou, Kun-Tsung, Chiang, Yi-Chao, Lin, Wei-Hong
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): VO, TUYET THI
• Application Number:
  US09/825,933
• Publication Number:
  US 20020097004A1
• Time in Patent Office: 467 Days
• Field of Search: 315/311, 315/310, 315/307, 315/291, 315/297, 315/224, 315/321
• US Class Current: 315/311
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations

Abstract

The present invention relates to a driving system for multiple lamps, which comprises a plurality of lamps including one master lamp and at least one slave lamp, an inverter circuit for converting DC power to AC power to be supplied to said plurality of lamps, and at least one current balancing circuit having an impedance device coupled to each of the slave lamp, so that the equivalent impedance varies with the current values of said master lamp and each of said slave lamps to thereby balance the currents in said master slave lamps.

Claims

1. A driving system for multiple lamps including a first lamp and a second lamp, comprising:

an inverter circuit for converting DC power to AC power to be supplied to said first and second lamps; and

a current balancing circuit for balancing the currents passing through said first and second lamps;

wherein said current balancing circuit comprising;

a first impedance device coupled to said first lamp;

a second impedance device coupled to said second lamp;

a first transistor with its collector and emitter respectively coupled to the two ends of said first impedance device and with its base coupled to said second impedance device; and

a third transistor with its collector and emitter respectively coupled to the two ends of said second impedance device and with its base coupled to said first impedance device.

19. The driving system for multiple lamps according to claim 1, wherein said inverter circuit includes a plurality of transformers.

2. A power supply system for driving multiple loads including a first load and a second load, comprising:

an inverter circuit for converting DC power to AC power to be supplied to said loads; and

a current balancing circuit, comprising;

a variable impedance circuit coupled to said second load;

a current sampling circuit for obtaining the current values through said first load and through said second load; and

a comparator circuit with its input terminals coupled to said current sampling circuit and its output terminal coupled to said variable impedance circuit for comparing the current values through said first load and through said second load and selectively outputting a control signal to vary the equivalent impedance of said variable impedance circuit to thereby balance the current values through said first load and through said second load.

3. A power supply system for multiple loads including a master load and a slave load, comprising:

a driving circuit for supplying power to said loads; and

a current balancing circuit for balancing the currents passing through said master load and said slave load;

wherein said current balancing circuit comprising;

a variable impedance circuit including an impedance device coupled to said slave load, a first transistor and a second transistor with their collectors and emitters respectively coupled to the two ends of said impedance device so that the equivalent impedance of said variable impedance circuit varies when either of said first and second transistors is driven;

current sampling circuit for obtaining the current values of said master load and said slave load; and

comparator circuit with its input coupled to said current sampling circuit and its output coupled to the bases of said first and said second transistors for comparing the currents passing through said master and slave loads and selectively outputting a control signal to drive said first and second transistors.

4. The power supply system for multiple loads according to claim 3, wherein said impedance device is a capacitor.

5. The power supply system for multiple loads according to claim 3, wherein said impedance device is a resistor.

6. The power supply system for multiple loads according to claim 3, wherein said impedance device is an inductor.

7. A driving system for multiple lamps including a first lamp and a second lamp, comprising:

an inverter circuit for converting DC power to AC power to be supplied to said first and second lamps; and

a current balancing circuit for balancing the currents passing through said first and second lamps;

wherein said current balancing circuit comprising;

a first impedance device coupled to said first lamp;

a second impedance device coupled to said second lamp;

a first transistor and a second transistor with their collectors and emitters respectively coupled to the two ends of said first impedance device and with their bases coupled to said second impedance device; and

a third transistor and a forth transistor with their collectors and emitters respectively coupled to the two ends of said second impedance device and with their bases coupled to said first impedance device.

8. The driving system for multiple lamps according to claim 7, wherein said impedance device is a capacitor.

9. The driving system for multiple lamps according to claim 7, wherein said impedance device is a resistor.

10. The driving system for multiple lamps according to claim 7, wherein said impedance device is an inductor.

11. The driving system for multiple lamps according to claim 7, wherein said first and third transistors are NPN transistors, and said second and forth transistors are PNP transistors.

12. The driving system for multiple lamps according to claim 7, further comprising a first pair of diodes for compensating the voltage between the bases and emitters of said first and second transistors and a second pair of diodes for compensating the voltage between the bases and emitters of said third and forth transistors.

13. The driving system for multiple lamps according to claim 7, wherein said inverter circuit includes a single transformer.

14. The driving system for multiple lamps according to claim 7, wherein said inverter circuit includes a plurality of transformers.

15. A driving system for multiple lamps including a master lamp and a slave lamp, comprising:

an inverter circuit for converting DC power to AC power to be supplied to said lamps; and

a current balancing circuit including a variable impedance circuit coupled to said slave lamp, and a circuit for sampling the current values through said master lamp and through said slave lamp and for accordingly outputting a control signal to vary the equivalent impedance of said variable impedance circuit to thereby balance the current in said master and slave lamps.

16. The driving system for multiple lamps according to claim 15, wherein said circuit for sampling the current values and for outputting the control signal comprises a sampling circuit for obtaining the positive current waveforms of said master and slave lamps and a comparator for comparing the positive current waveforms of the master and slave lamps.

17. The driving system for multiple lamps according to claim 15, wherein said circuit for sampling the current values and for outputting the control signal comprises a sampling circuit for obtaining the positive and negative current waveform of said master and slave lamps and two comparators respectively for comparing the positive current waveforms and the negative current waveforms of said master and slave lamps.

18. The driving system for multiple lamps according to claim 15, wherein said inverter circuit includes a single transformer.

20. The driving system for multiple lamps according to claim 15, wherein said variable impedance circuit comprises:

an impedance device connected in series with said slave lamp; and

a first transistor and a second transistor with their collectors and emitters respectively coupled to the two ends of said impedance device, so that the equivalent impedance of said variable impedance circuit varies when either of said first and second transistors is driven.

21. The driving system for multiple lamps according to claim 20, wherein said impedance device is a capacitor.

22. The driving system for multiple lamps according to claim 20, wherein said impedance device is a resistor.

23. The driving system for multiple lamps according to claim 20, wherein said impedance device is an inductor.

24. A driving system for multiple lamps including a master lamp and a slave lamp, comprising:

an inverter circuit for converting DC power to AC power to be supplied to said lamps; and

a current balancing circuit, comprising;

a variable impedance circuit coupled to said slave lamp;

a current sampling circuit for obtaining the current values through said master lamp and through said slave lamp; and

a comparator circuit with its input terminals coupled to said current sampling circuit and its output terminal coupled to said variable impedance circuit for comparing the current values through said master lamp and through said slave lamp and selectively outputting a [voltage] control signal to vary the equivalent impedance of said variable impedance circuit to thereby balance the current values through said master lamp and through said slave lamp.

25. The system according to claim 24, wherein said variable impedance circuit comprises:

a capacitor connected in series with said slave lamp; and

a transistor having a gate coupled to said output terminal of said comparator circuit, a collector and an emitter respectively coupled to the two ends of said capacitor, so that the equivalent impedance of said variable impedance circuit varies when said transistor is driven.

26. The system according to claim 24, wherein said variable impedance circuit comprises:

a resistor connected in series with said slave lamp; and

a transistor having a gate coupled to said output terminal of said comparator circuit, a collector and an emitter respectively coupled to the two ends of said resistor, so that the equivalent impedance of said variable impedance circuit varies when said transistor is driven.

27. The system according to claim 24, wherein said variable impedance circuit comprises:

an inductor connected in series with said slave lamp; and

a transistor having a gate coupled to said output terminal of said comparator circuit, a collector and an emitter respectively coupled to the two ends of said inductor, so that the equivalent impedance of said variable impedance circuit varies when said transistor is driven.

28. The system according to claim 24, wherein said variable impedance circuit comprises:

a capacitor connected in series with said slave lamp; and

a first transistor and a second transistor with their gates coupled to said output terminal of said comparator circuit, and with their collectors and emitters respectively coupled to the two ends of said capacitor, so that the equivalent impedance of said variable impedance circuit varies when either of said transistors is driven.

29. The system according to claim 24, wherein said variable impedance circuit comprises:

a resistor connected in series with said slave lamp; and

a first transistor and a second transistor with their gates coupled to said output terminal of said comparator circuit, and with their collectors and emitters respectively coupled to the two ends of said resistor, so that the equivalent impedance of said variable impedance circuit varies when either of said transistors is driven.

30. The system according to claim 24, wherein said variable impedance circuit comprises:

an inductor connected in series with said slave lamp; and

a first transistor and a second transistor with their gates coupled to said output terminal of said comparator circuit, and with their collectors and emitters respectively coupled to the two ends of said inductor, so that the equivalent impedance of said variable impedance circuit varies when either of said transistors is driven.

31. The system according to claim 24, wherein said current sampling circuit is used for obtaining the positive current waveforms of said master and slave lamps;

and said comparator circuit includes one comparator for comparing the positive current waveforms of the master and slave lamps.

32. The system according to claim 24, wherein said current sampling circuit is used for obtaining the positive and negative current waveform of said master and slave lamps;

and said comparator circuit includes two comparators respectively for comparing the positive current waveforms and the negative current waveforms of said master and slave lamps.