# US 9,435,524 B2 · Liquid cooled LED systems

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- Number: US 9,435,524 B2
- Document ID: US9435524B2
- Status: Granted
- Kind: B2
- Application number: 13/453,577
- Filed: 2012-04-23
- Published: 2013-07-04
- Granted: 2016-09-06
- Earliest claimed: 2011-12-30
- Assignees: Cree, Inc.
- Applicants: Praneet Athalye
- Inventors: Praneet Athalye
- Web page: https://patentgrep.com/patent/US9435524B2

## CPC

- F21K 9/64: using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
- F21K 9/232: specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
- F21K 9/233: specially adapted for generating a spot light distribution, e.g. for substitution of reflector lamps
- F21K 9/90: Methods of manufacture
- F21V 3/00: Globes; Bowls; Cover glasses (with refracting properties F21V5/00; with reflecting properties F21V7/00; characterised by cooling arrangements F21V29/506)
- F21V 3/12: the coatings comprising photoluminescent substances
- F21V 29/56: using liquid coolants (F21V29/51 takes precedence)
- F21V 29/58: characterised by the coolants
- F21V 29/59: {with forced flow of the coolant}
- F21V 21/30: Pivoted housings or frames
- F21V 29/506: of globes, bowls or cover glasses
- F21Y 2101/00: Point-like light sources
- F21Y 2107/00: Light sources with three-dimensionally disposed light-generating elements
- F21Y 2113/13: comprising an assembly of point-like light sources
- F21Y 2115/10: Light-emitting diodes [LED]
- F21K: NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED

## Abstract

Liquid cooled LED systems are disclosed. Embodiments of the invention provide an LED lighting system in which the LED devices are cooled by circulating liquid or fluid. In example embodiments, a flow return member provides a way for a fluid medium to enter and exit an envelope containing the LED devices. An additional cooling mechanism, such as a radiator or thermoelectric cooler can be provided. The optically transmissive fluid medium can be, for example, oil or a fluorinated or halogenated liquid or gel, and can optionally provide index matching. The fluid medium can optionally include a phase change material in order to enhance cooling. In some embodiments, a pump is used to circulate the fluid medium. However, the optical envelope and/or the flow return member could also be oriented so that the fluid medium circulates by gravity and/or temperature difference.

## Claims

### Claim 1

A lighting system comprising:
a tubular optical envelope;
an array of LED devices without a submount or other carrier within the optically transmissive envelope to be operable to substantially emit omnidirectional light when energized;
an optically transmissive fluid medium in thermal communication with the array of LED devices; and
a flow return member in fluid communication with the tubular optical envelope so that the optically transmissive fluid medium can circulate through the optically transmissive envelope, the flow return member further comprising a plurality of metal coils through which the optically transmissive fluid passes, the plurality of metal coils being external to the tubular optical envelope.

### Claim 2 (depends on 1)

The lighting system of claim 1 further comprising a thermoelectric cooler in thermal communication with the optically transmissive fluid medium.

### Claim 3 (depends on 1)

The lighting system of claim 1 further comprising a pump in fluid communication with at least one of the tubular optical envelope and the flow return member.

### Claim 4 (depends on 1)

The lighting system of claim 1 wherein at least one of the optically transmissive envelope and the flow return member is oriented so that the fluid medium circulates by at least one of gravity and temperature difference.

### Claim 5 (depends on 1)

The lighting system of claim 1 wherein the optically transmissive fluid medium comprises at least one of oil and a fluorinated or halogenated liquid or gel.

### Claim 6 (depends on 5)

The lighting system of claim 5 wherein the optically transmissive fluid medium is an index matching medium.

### Claim 7 (depends on 5)

The lighting system of claim 5 further comprising phosphor disposed within or on the tubular optical envelope.

### Claim 8 (depends on 7)

The lighting system of claim 7 wherein the tubular optical envelope further comprises neodymium oxide so that the envelope filters light to exhibit a spectral notch between 520 nm and 605 nm.

### Claim 9 (depends on 5)

The lighting system of claim 5 wherein the array of LED devices further comprises a plurality of LED devices connected in series.

### Claim 10 (depends on 9)

The lighting system of claim 9 wherein the electrical connection is configured to supply the array of LED devices with alternating current.

### Claim 11 (depends on 9)

The lighting system of claim 9 wherein the electrical connection is configured to supply the array of LED devices with direct current.

### Claim 12 (depends on 1)

The lighting system of claim 1 wherein the optically transmissive fluid medium comprises a phase change material.

### Claim 13 (depends on 1)

The lighting system of claim 1 wherein the array of LED devices further comprises a plurality of LED devices connected in parallel.

### Claim 14 (depends on 13)

The lighting system of claim 13 wherein the flow return member and optically transmissive envelope are configured so that the optically transmissive fluid medium circulates in a direction that opposes a voltage drop through the plurality of LED devices.

### Claim 15 (depends on 1)

The lighting system of claim 1 further comprising:
an internal envelope between the tubular optical envelope and the array of LED devices; and
an internal coolant disposed in the internal envelope.

### Claim 16 (depends on 15)

The lighting system of claim 15 wherein the internal coolant comprises at least one of oil and a fluorinated or halogenated liquid or gel.

### Claim 17 (depends on 16)

The lighting system of claim 16 wherein the optically transmissive fluid medium comprises water.

### Claim 18

A light fixture comprising:
an optically transmissive tubular envelope;
a linear array of LED devices without a submount or other carrier disposed in the tubular envelope to be operable to substantially emit omnidirectional light when energized;
a reflector configured to reflect the omnidirectional light from the linear array of LED;
an optically transmissive fluid medium in thermal communication with the linear array of LED devices;
a flow return member in fluid communication with the tubular envelope so that the optically transmissive fluid medium can circulate through the tubular envelope, the flow return member further comprising a plurality of metal coils through which the optically transmissive fluid passes, the plurality of metal coils being external to the tubular envelope; and
a power supply connected to the linear array of LED devices.

### Claim 19 (depends on 18)

The light fixture of claim 18 further comprising a thermoelectric cooler in thermal communication with the optically transmissive fluid medium.

### Claim 20 (depends on 18)

The light fixture of claim 18 wherein the optically transmissive fluid medium comprises at least one of oil and a fluorinated or halogenated liquid or gel.

### Claim 21 (depends on 20)

The light fixture of claim 20 wherein the optically transmissive fluid medium is an index matching medium.

### Claim 22 (depends on 18)

The light fixture of claim 18 wherein the linear array of LED devices further comprises a plurality of LED devices connected in series.

### Claim 23 (depends on 18)

The light fixture of claim 18 wherein the linear array of LED devices further comprises a plurality of LED devices connected in parallel.

### Claim 24 (depends on 23)

The light fixture of claim 23 wherein the flow return member and optically transmissive tubular envelope are configured so that the optically transmissive fluid medium circulates in a direction that opposes a direction of voltage drop through the plurality of LED devices.

### Claim 25

A method of operating an LED lighting system, the method comprising:
energizing a linear LED array comprising a plurality of LEDs without a submount or other carrier so that the plurality of LEDs substantially emit omnidirectional light;
circulating an optically transmissive fluid through a tubular optical envelope surrounding the linear LED array so that the LED array substantially emits the omnidirectional light through the optically transmissive fluid medium and the tubular optical envelope; and
dissipating heat from the optically transmissive fluid by circulating the optically transmissive fluid medium through a flow return member comprising a plurality of metal coils through which the optically transmissive fluid passes, the plurality of metal coils being external to the tubular optical envelop.

### Claim 26 (depends on 25)

The method of claim 25 further comprising energizing a phosphor.

### Claim 27 (depends on 26)

The method of claim 26 further comprising filtering a visible light intensity using neodymium oxide so that the intensity is comparatively reduced within a predetermined part of a spectrum of visible light.

### Claim 28 (depends on 25)

The method of claim 25 wherein at least one of the circulating of the optically transmissive fluid through the tubular optical envelope and the circulating of the optically transmissive fluid through the flow return member further comprises pumping the optically transmissive fluid.

### Claim 29 (depends on 25)

The method of claim 25 wherein the circulating of the optically transmissive fluid through the optical envelope further comprises circulating the optically transmissive fluid in a direction that opposes a voltage drop in the linear LED array.