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Researchers Submit Patent Application, "Thermal Control Circuit for an Active Cooling Module for a Light-Emitting Diode Fixture", for Approval

August 6, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Kornitz, Alexander (Coquitlam, CA); Pospisil, Mirek (West Vancouver, CA), filed on January 14, 2013, was made available online on July 24, 2014.

No assignee for this patent application has been made.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to an active cooling module and, in particular, to a thermal control circuit for an active cooling module for a light-emitting diode fixture.

"Light-emitting diodes, like any semiconductor, emit heat during their operation. This is because not all of the electrical energy provided to a light-emitting diode is converted to luminous energy. A significant portion of the electrical energy is converted to thermal energy which results in an increase in the temperature of the light-emitting diode. In resistor driven circuits, as the temperature of the light-emitting diode increases, the forward voltage drops and the current passing through the PN junction of the light-emitting diode increases. The increased current causes additional heating of the PN junction and may thermally stress the light-emitting diode.

"Thermally stressed light-emitting diodes lose efficiency and their output is diminished. In certain situations, optical wavelengths may even shift causing white light to appear with a blue tinge. Thermally stressed light-emitting diodes may also impose an increased load on related driver components causing their temperature to increase as well. This may result in broken wire bonds, delaminating, internal solder joint detachment, damage to die-bond epoxy, and lens yellowing. If nothing is done to control the increasing temperature of the light emitting diode, the PN junction may fail, possibly resulting in thermal runaway and catastrophic failure.

"Thermal control of light-emitting diodes involves the transfer of thermal energy from the light-emitting diode. Accordingly, one aspect of light-emitting diode fixture design involves efficiently transferring as much thermal energy as possible away from the PN junction of the light-emitting diode. This can generally be accomplished, at least in part, through the use of a heat sink However, for more powerful light-emitting diode fixtures in the 20 to 60 watt range or in applications where numerous light-emitting diodes are disposed within a confined space, an additional cooling means may be required to maintain performance. This is because the thermal energy generated by the light-emitting diodes may at times exceed the thermal energy absorbed and dissipated by the heat sink In these situations a cooling fan is typically used in combination with the heat sink

"In a conventional thermal control system for light-emitting diode fixtures, a heat sink and a cooling fan are thermally coupled to a light source comprised of a plurality of light-emitting diodes. A thermal sensor senses the temperature of the light source and signals a controller to operate a variable speed cooling fan, based on the temperature of the light source, to maintain the fixture within a desired temperature range. However, the need for a controller, typically in the form of a microprocessor, increases the number of components in the thermal control system and thereby increases manufacturing costs."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "There is accordingly provided a thermal control circuit comprising a positive temperature coefficient thermistor array, a negative temperature coefficient thermistor array, and a resistor array. The positive temperature coefficient thermistor array and resistor array are electrically connected in parallel to a first terminal of the thermal control circuit. The negative temperature coefficient thermistor array is electrically connected to a second terminal of the thermal control circuit. The positive temperature coefficient thermistor array, the negative temperature coefficient thermistor array, and the resistor array are all connected by a negative bus to a third terminal of the thermal control circuit. The thermal control circuit may be a package.

"There is also provided an active cooling module for a light-emitting diode. The active cooling module comprises a cooling device electrically connected to a power supply. A thermal control circuit is electrically connected to the power supply. The thermal control circuit comprises a positive temperature coefficient thermistor array, a negative temperature coefficient thermistor array, and a resistor array. The positive temperature coefficient thermistor array and resistor array are electrically connected in parallel to a first terminal of the thermal control circuit. The negative temperature coefficient thermistor array is electrically connected to a second terminal of the thermal control circuit. The positive temperature coefficient thermistor array, the negative temperature coefficient thermistor array, and the resistor array are all connected by a negative bus to a third terminal of the thermal control circuit. A negative terminal of the light-emitting diode is electrically connected the first terminal of the thermal control circuit. A negative terminal of the cooling device is electrically connected to the second terminal of the thermal control circuit and a negative terminal of the power supply is electrically connected to the third terminal of the thermal control circuit. The active cooling module may further include a heat sink and the light-emitting diode may be thermally coupled to the heat sink. The thermal control circuit may be mounted on the heat sink The thermal control circuit may be a package. The cooling device may be a fan. The light-emitting diode may be part of an LED array.

"There is further provided an electrical device provided with an active cooling module. The electrical device comprises a power supply. A light-emitting diode electrically connected to the power supply. A cooling device and thermal control circuit are also electrically connected to the power supply. The thermal control circuit comprises a positive temperature coefficient thermistor array, a negative temperature coefficient thermistor array, and a resistor array. The positive temperature coefficient thermistor array and resistor array are electrically connected in parallel to a first terminal of the thermal control circuit. The negative temperature coefficient thermistor array is electrically connected to a second terminal of the thermal control circuit. The positive temperature coefficient thermistor array, the negative temperature coefficient thermistor array, and the resistor array are all connected by a negative bus to a third terminal of the thermal control circuit. A negative terminal of the light-emitting diode is electrically connected the first terminal of the thermal control circuit. A negative terminal of the cooling device is electrically connected to the second terminal of the thermal control circuit and a negative terminal of the power supply is electrically connected to the third terminal of the thermal control circuit. The electronic device may further include a printed circuit board and the thermal control circuit may mounted on the printed circuit board. The active cooling module may further include a heat sink and the light-emitting diode may be thermally coupled to the heat sink The thermal control circuit may be mounted on the heat sink. The thermal control circuit may be a package. The cooling device may be a fan. The light-emitting diode may be part of an LED array. The electronic device may be an light-emitting diode of array.

BRIEF DESCRIPTIONS OF DRAWINGS

"The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which:

"FIG. 1 is a circuit diagram of a light-emitting diode fixture provided with an improved active cooling module having an improved thermal control circuit;

"FIG. 2 is a schematic diagram of the thermal control circuit coupled to a heat sink;

"FIG. 3 shows a schematic diagram of the thermal control circuit coupled to a printed circuit board upon which an LED array is mounted;

"FIG. 4 shows a schematic diagram of a thermal control circuit as an electrical package; and

"FIG. 5 is a simplified circuit diagram of the active cooling module."

For additional information on this patent application, see: Kornitz, Alexander; Pospisil, Mirek. Thermal Control Circuit for an Active Cooling Module for a Light-Emitting Diode Fixture. Filed January 14, 2013 and posted July 24, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4143&p=83&f=G&l=50&d=PG01&S1=20140717.PD.&OS=PD/20140717&RS=PD/20140717

Keywords for this news article include: Patents, Electronics, Circuit Board, Light-emitting Diode.

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Source: Electronics Newsweekly


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