Lamp electronic ballast with a piezoelectric cooling fan

• US 6,353,295 B1
• Filed: 01/20/1999
• Issued: 03/05/2002
• Est. Priority Date: 01/20/1999
• Status: Expired due to Fees

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Inventors: Mehrotra, Vivek, Bruning, Gert W., Sabate, Juan, Sridhar, Shri, Roozen, Nicolaas Bernardus
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): TRAN, THUY V
• Application Number:
  US09/233,844
• Time in Patent Office: 1,140 Days
• Field of Search: 315/248, 315/246, 315/247, 315/200.R, 315/276, 315/291, 315/307, 315/55, 310/311, 310/314, 310/316.01, 310/319, 310/324, 310/348, 323/355, 323/358, 323/908, 363/52, 363/55, 363/125, 363/141, 363/123
• US Class Current: 315/248
• CPC Class Codes: H01L 23/467 by flowing gases, e.g. air H01L23/473 takes precedence
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05B 41/02 Details
• 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
• CPC Class Codes: H05B 41/36 Controlling

Abstract

A lamp electronic ballast with a piezoelectric cooling fan. Use of ballast-driven lamps is limited in some lighting applications by thermal considerations. For example, the problem of heat removal from compact fluorescent lamps with integrated ballasts has limited their use. Similarly, the use of ballast-driven fluorescent lighting in high hat and other closed luminaire applications has been limited by thermal considerations. Thermal management of ballasts for such thermally sensitive applications is provided by a piezoelectric fan integrated with the ballast. The power to drive the fan may be obtained from the same AC line input that supplies the ballast, or from an AC ripple voltage present at the output of a rectifier in the ballast, or from the output of the ballast to the lamp, or from any suitable circuit location in the ballast. The fan maybe a membrane-type spot-cooler comprising a thin membrane carried by a frame mounted adjacent a hot spot. The membrane has one or more holes in it and is vibrated about a central plane by suitably spaced piezoelectric elements attached to the membrane.

Claims

1. The combination of a lamp electronic ballast and a piezoelectric fan positioned to remove heat from the ballast, the ballast comprising a rectifier adapted to receive AC power and produce DC power with an AC ripple voltage, and an inverter coupled to the rectifier and to an output of the ballast which is adapted to be coupled to a lamp, the piezoelectric fan being coupled to be driven by power from said AC ripple voltage present at the rectifier and having a mechanical resonance related to the frequency of the AC ripple voltage.

2. The combination as claimed in claim 1 wherein the ballast comprises a power factor correction circuit coupled between the rectifier and the inverter.

3. The combination as claimed in claim 1 comprising a conversion circuit for the piezoelectric fan coupled to receive the AC ripple voltage and provide power suitable for driving the piezoelectric fan.

4. The combination as claimed in claim 1 wherein the piezoelectric fan comprises a membrane having one or more apertures therein, and one or more piezoelectric elements fixed so as to vibrate the membrane about a central plane in response to the power coupled from the ballast effective to move air through the one or more apertures.

5. The combination as claimed in claim 4 wherein the piezoelectric fan comprises four piezoelectric elements fixed to and spaced 90E apart about the periphery of the membrane, the membrane having a central aperture, and wherein a frame is mounted adjacent the area to be cooled and the membrane and one end of the piezoelectric elements are fixed to the frame.

6. The combination as claimed in claim 5 wherein the membrane is made of a polyamide material and the piezoelectric elements are bimorphous ceramic elements.

7. The combination as claimed in claim 4 wherein the membrane has a hole therethrough of non-uniform cross section configured to improve air movement therethrough in at least one direction.

8. The combination as claimed in claim 7 where the hole of non-uniform cross section decreases in cross-sectional area in a direction in which improved air movement is desired.

9. The combination as claimed in claim 4 wherein the mechanical resonance of the piezoelectric fan is the combined mechanical resonance of the membrane and the acoustic Helmholtz resonance of an acoustical cavity below the membrane.

10. The combination of a lamp electronic ballast and a piezoelectric fan positioned to remove heat from the ballast, the ballast providing AC power at an output thereof which is adapted to be coupled to a lamp and comprising an inverter coupled to receive DC power and to provide the AC power at an output thereof, the piezoelectric fan being coupled to the output of the inverter and having a mechanical resonance related to the frequency of the AC power.

11. The combination as claimed in claim 10 comprising an AC to DC converter coupled to receive AC power and provide the DC power to the inverter.

12. The combination as claimed in claim 11 wherein the ballast output is coupled to the output of the inverter.

13. The combination as claimed in claim 12 wherein the ballast comprises a power factor correction circuit coupled between the AC to DC converter and the inverter.

14. The combination as claimed in claim 12 wherein the ballast comprises a DC to DC converter coupled between the AC to DC converter and the inverter.

15. The combination as claimed in claim 10 comprising a conversion circuit for the piezoelectric fan coupled to receive the AC power at the output of the inverter and provide power suitable for driving the piezoelectric fan.

16. The combination as claimed in claim 10 wherein the piezoelectric fan comprises a membrane having one or more apertures therein, and one or more piezoelectric elements fixed so as to vibrate the membrane about a central plane in response to the power coupled from the ballast effective to move air through the one or more apertures.

17. The combination as claimed in claim 16 wherein the piezoelectric fan comprises four piezoelectric elements fixed to and spaced 90 E apart about the periphery of the membrane, the membrane having a central aperture, and wherein a frame is mounted adjacent the area to be cooled and the membrane and one end of the piezoelectric elements are fixed to the frame.

18. The combination as claimed in claim 17 wherein the membrane is made of a polyamide material and the piezoelectric elements are bimorphous ceramic elements.

19. The combination as claimed in claim 16 wherein the mechanical resonance of the piezoelectric fan is the combined mechanical resonance of the membrane and the acoustic Helmholtz resonance of an acoustical cavity below the membrane.

20. A miniature piezoelectric fan comprising a membrane having one or more apertures therein, and one or more piezoelectric elements fixed so as to vibrate the membrane about a central plane in response to an electrical signal coupled to the piezoelectric elements effective to move air through the one or more apertures.

21. The piezoelectric fan as claimed in claim 20 comprising four piezoelectric elements fixed to and spaced 90 E apart about the periphery of the membrane, the membrane having a central aperture, and wherein a frame is mounted adjacent the area to be cooled and the membrane and one end of the piezoelectric elements are fixed to the frame.

22. The piezoelectric fan as claimed in claim 21 wherein the membrane is made of a polyamide material and the piezoelectric elements are bimorphous ceramic elements.

23. The piezoelectric fan as claimed in claim 22 wherein the membrane has a hole therethrough of non-uniform cross section configured to improve air movement therethrough in at least one direction.

24. The piezoelectric fan as claimed in claim 23 where the hole of non-uniform cross section decreases in cross-sectional area in a direction in which improved air movement is desired.

25. The piezoelectric fan as claimed in claim 20 wherein the membrane has a mechanical resonance, and the piezoelectric fan can be driven by an electrical signal having a frequency related to the mechanical resonance of the membrane.

26. The piezoelectric fan as claimed in claim 20 wherein the membrane has a mechanical resonance, and the piezoelectric fan can be driven by an electrical signal having a frequency related to the combined mechanical resonance of the membrane and the acoustic Helmholtz resonance of an acoustical cavity below the membrane.

27. The combination of a lamp electronic ballast and a piezoelectric fan positioned to remove heat from the ballast,

the ballast having an input for receiving electric power, and first means for producing power within the ballast for a ballast use other than cooling, said power within the ballast including a component at a frequency higher than the received electric power,

said first means including second means for providing, from said power within the ballast including said component, electrical power at an output thereof which is adapted to be coupled to a lamp,

the piezoelectric fan being electrically coupled to the ballast and for driving by power coupled from said component at a frequency higher than the received electric power.

28. The combination as claimed in claim 27 wherein said second means comprises an inverter which provides a high frequency AC voltage, said high frequency AC voltage being said component, the fan having a mechanical resonance related to said high frequency and being coupled to the ballast to be driven by the high frequency AC voltage provided by the inverter.

29. The combination as claimed in claim 28 wherein said second means provides the high frequency AC voltage at said output.

30. The combination as claimed in claim 28, further comprising a conversion circuit for the piezoelectric fan coupled to receive the AC voltage from the inverter and provide power suitable for driving the piezoelectric fan.

31. The combination as claimed in claim 27 wherein:

the received electric power is an AC voltage at a first frequency,

said first means for producing power comprises a rectifier circuit converting said AC voltage at a first frequency to a DC voltage having an AC ripple voltage, the AC ripple voltage including said component at a frequency higher than the received electric power,

said second means receives said DC voltage for providing the output, and

the fan is coupled to be driven by said component of the AC ripple voltage and has a mechanical resonance related to the frequency of said component.

32. The combination as claimed in claim 31, further comprising a conversion circuit for the piezoelectric fan coupled to receive said component of the AC ripple voltage and provide power suitable for driving the piezoelectric fan.