Distributed parallel semiconductor device spaced for improved thermal distribution and having reduced power dissipation

• US 6,310,439 B1
• Filed: 03/15/1999
• Issued: 10/30/2001
• Est. Priority Date: 03/15/1999
• Status: Expired due to Term

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Weightman, Russell, Spira, Joel, Billington, Scott A., Jacoby, Elliot G. Jr.
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): VO, TUYET THI
• Application Number:
  US09/268,209
• Time in Patent Office: 960 Days
• Field of Search: 315/112-119, 315/209.SC, 361/748, 361/57, 257/706, 257/712
• US Class Current: 315/112
• 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 39/00 Circuit arrangements or apparatus for operating incandescent light sources structurally associated with the incandescent lamps H01K1/62
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: H05K 7/209 Heat transfer by conduction from internal heat source to heat radiating structure H05K7/20909 takes precedence

Abstract

A single triac on a heat sink is replaced by a plurality of lower rated current, parallel connected triacs for carrying the same total current as the single triac. The plural devices are spaced apart as far as possible, within the confines of an insulation back cover, to reduce the thermal gradient across the heat sink and to reduce the input thermal power to the heat sink. Thermally conductive compressive sheets thermally couple the flat heat sink to a face plate on the side of the heat sink opposite to the side receiving the triacs.

Claims

1. A reduced temperature electric power control structure comprising a heat sink having a device mounting surface and at least two parallel connected semiconductor switching devices mounted on said device mounting surface of said heat sink and thermally coupled thereto and which are spaced apart by a distance which substantially thermally couples said at least two semiconductor switching devices carrying instantaneous currents of substantially equal magnitude as a function of time;

said at least two semiconductor switching devices producing less power dissipation than a like single semiconductor device which carries the same total current as is carried by said at least two semiconductor devices.

2. The structure of claim 1 wherein said at least two semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and further comprising a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

3. The structure of claim 1 wherein said semiconductor switching devices are selected from the group consisting of triacs, thyristors, IGBTs, diodes and SCRs.

4. The structure of claim 1 wherein each of said at least two semiconductor devices have a power dissipation determined by the average current conducted by each device multiplied by its forward turn on voltage drop plus the on resistance of each times the square of the RMS current through each device.

5. The structure of claim 4 wherein said at least two semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and further comprising a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

6. The structure of claim 4 wherein said heat sink is a thin copper plate which has a thickness and thermal conductivity to ensure the equal heating of each of said semiconductor devices and the equal division of current between all of said semiconductor devices.

7. The structure of claim 6 wherein said heat sink has a substantially constant thickness.

8. The structure of claim 7 wherein said at least two semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and further comprising a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

9. The structure of claim 7 which further includes a back cover which encloses said semiconductor devices and said control circuit;

said back cover having a maximum temperature rise less than about 65°

C. at maximum current through said semiconductor devices when said power control circuit is connected to and controlling a 2000 watt load.

10. The structure of claim 6 wherein said semiconductor devices are each rated to carry at least 25 amperes and replace a single device which is rated to carry at least 40 amperes.

11. The structure of claim 10 wherein said heat sink has a substantially constant thickness.

12. The structure of claim 6 which further includes a back cover which encloses said semiconductor devices and said control circuit;

said back cover having a maximum temperature rise less than about 65°

C. at maximum current through said semiconductor devices when said power control circuit is connected to and controlling a 2000 watt load.

13. The structure of claim 12 which comprises 4 semiconductor devices located on the corners of a rectangle surrounding a central area of said copper plate.

14. The structure of claim 13 wherein said 4 semiconductor devices are each rated to carry at least 16 amperes and replace a single device which is rated to carry at least 40 amperes.

15. The structure of claim 4 wherein said heat sink is a flat rectangular thin copper plate, and said semiconductor devices are spaced symmetrically around a central area of said plate.

16. The structure of claim 15 which comprises 4 semiconductor devices located on the corners of a rectangle surrounding a central area of said copper plate.

17. The structure of claim 16 wherein said 4 semiconductor devices are each rated to carry at least 16 amperes and replace a single device which is rated to carry at least 40 amperes.

18. The structure of claim 17 wherein each of said 4 devices is a triac.

19. The structure of claim 17 wherein each of said 4 devices are triacs.

20. A wall mounted control structure for control of a lighting load;

said wall mounted control structure comprising a thin rectangular conductive plate which acts as a thermal heat sink and at least two semiconductor switching devices each having respective first and second power electrodes and being supported on and thermally connected to a first surface of said conductive plate and said semiconductor devices being in thermal communication with each other;

first and second externally accessible power conductors connected to said first and second power electrodes of said semiconductor switching devices, whereby said at least two devices are connected in parallel;

a back cover of insulation material attached to said conductive plate and enclosing said at least two semiconductor switching devices;

said first and second externally accessible power conductors extending through said back cover for external connection to a source of power and to said lighting load;

an insulation plate connected to a second surface of said conductive plate which is opposite to said first surface;

a manually operable operating means for varying the conduction of said semiconductor devices;

said at least first and second semiconductor devices being spaced apart by a distance sufficient to more uniformly distribute the heat produced by said devices over a major portion of the area of said conductive plate than if a single semiconductor device were used.

21. The structure of claim 20 wherein said at least two semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and further comprising a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

22. The structure of claim 20 wherein said semiconductor switching devices are selected from the group consisting of triacs, thyristors, IGBTs, SCRs and diodes.

23. The structure of claim 20 wherein said thin rectangular conductive plate is a thin copper plate which has a thickness and thermal conductivity to ensure the equal heating of each of said semiconductor devices and the equal division of current between all of said semiconductor devices.

24. The structure of claim 20 wherein said back cover has a maximum temperature rise of 65°

C. when said power control circuit is connected to and controls a 2000 watt load.

25. The structure of claim 20 wherein said at least two semiconductor switching devices produce less power dissipation than a single semiconductor device which carries the same total current as is carried by said at least two semiconductor devices, and wherein each of said at least two semiconductor devices have a power dissipation determined by the average current conducted by each device multiplied by its forward turn on voltage drop plus the on resistance of each times the square of the RMS current through each device.

26. The structure of claim 25 wherein said at least two semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

27. The structure of claim 25 wherein said back cover has a maximum temperature rise of 65°

C. when said power control circuit is connected to and controls a 2000 watt load.

28. The structure of claim 25 wherein said thin rectangular conductive plate is a thin copper plate, and said semiconductor devices are spaced generally symmetrically around a central area of said plate.

29. The structure of claim 28 which comprises 4 semiconductor devices located on the corners of a rectangle generally surrounding the central area of said copper plate.

30. A process for reducing the temperature rise of the insulated back cover of a dimmer device comprising;

(a) mounting a plurality of parallel connected semiconductor devices which control a load current to a 2000 Watt lighting load on a thin metallic plate so that the devices carry substantially equal instantaneous current as a function of time and (b) spacing said devices from one another over the surface of said plate by a distance which substantially thermally couples said plurality of parallel connected devices whereby the insulated back cover enclosing the semiconductor devices is heated to a temperature rise less than about 65°

C.

31. A process for selecting a current rating for each of a plurality n of parallel connected semiconductor devices and physically arranging the location of each of said devices on the surface of a common heat sink, which is partially covered by a back cover to reduce maximum temperature comprising;

a) selecting a current rating which is at least 1/n of the total parallel current through said n parallel connected semiconductor devices while reducing the total power dissipation of said devices as compared to the power dissipation of a single device which has a current rating equal to that of the n devices in parallel, and

b) mounting said selected devices on said surface of said heat sink within the confines of said back cover, such that the selected devices are in thermal communication with each other.

32. An electric power control device comprising a plurality of semiconductor switching devices thermally connected to a common heat sink, wherein a thermal gradient surrounds each semiconductor switching device when the semiconductor switching device is operating, each thermal gradient overlapping at least one other thermal gradient to balance the current carried by each semiconductor switching device.

33. A wall mounted control structure for control of a lighting load;

said wall mounted structure comprising a rectangular conductive plate of uniform thickness having first and second opposite surfaces and at least one controllably conductive semiconductor switching device mechanically connected to said plate at its said first surface and in thermal communication therewith;

an insulation back cover fixed to said conductive plate and enclosing said at least one controllably conductive switching device;

an insulation plate having a first and second surface, the first surface positioned adjacent said second surface of said conductive plate a control circuit for controlling the conduction of said at least one controllably conductive switching device mounted within said back cover;

a control device coupled to said control circuit for controlling the operation of said at least one controllably conductive semiconductor switching device; and

a thermally conductive layer of material coupled to said insulation plate at said first surface which is in communication with said second surface of said conductive plate;

whereby heat from said conductive plate which is produced by said at least one controllably conductive switching device can be conducted to said second surface of said insulation plate.

34. The structure of claim 33 wherein said thermally conductive layer is a thin, flat, compressible fabric.

35. The structure of claim 33 wherein said at least one controllably conductive semiconductor switching device comprises at least two parallel connected semiconductor switching devices mounted on the same surface of said conductive plate and are thermally coupled thereto and which are spaced apart by a distance which substantially thermally couples said devices and reduces the thermal gradient across said plate;

said at least two semiconductor switching devices producing less power dissipation than a single semiconductor device which carries the same total current as is carried by said at least two semiconductor devices.

36. The device of claim 35 wherein each of said at least two parallel connected semiconductor switching devices have a power dissipation determined by the average current conducted by each device multiplied by its forward turn on voltage drop plus the on resistance of each times the square of the RMS current through each device.

37. The structure of claim 36 wherein said at least two parallel connected semiconductor switching devices are controllably conductive devices having respective input control electrodes;

and further comprising a common control circuit connected to each of said input control electrodes and operable to simultaneously and substantially identically control the current through each of said semiconductor switching devices.

38. The structure of claim 37 wherein said conductive plate is a thin copper plate which has a thickness and thermal conductivity to ensure the equal heating of each of said semiconductor devices and the equal division of current between all of said semiconductor devices.