COMPUTER LED BAR AND THERMAL ARCHITECTURE FEATURES

• US 20140085564A1
• Filed: 09/26/2012
• Published: 03/27/2014
• Est. Priority Date: 09/26/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hendren, Keith J., Mathew, Dinesh C., Rundle, Nicholas Alan, Degner, Brett W.
• Granted Patent: US 9,207,484 B2
• Time in Patent Office: Days
• US Class Current: 349/58
• CPC Class Codes: G02F 1/133308 Support structures for LCD panels, e.g. frames or bezels
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell
• CPC Class Codes: G02F 1/133385 with cooling means, e.g. fans
• CPC Class Codes: G02F 1/133628 with cooling means

Abstract

The described embodiments relate generally to liquid crystal displays (LCDs) and more particularly to thermal management of heat produced by an illumination source in an LCD module. High temperatures generated by the illumination source can cause color shifts in the LCD due to changes in any included LEDs and liquid crystals. One solution is to house the LCD module in a metal chassis and thermally couple the LED light bar to the metal chassis. Furthermore, the LCD module can be kept at a uniform temperature by transferring heat from a region near the LED light bar to a relatively cooler region of the LCD module. These approaches can minimize any alterations or shifts in color resulting from heat from the LED light bar.

Claims

1. A computing device, comprising:

a chassis, the chassis formed of a thermally conductive material and configured to enclose and support a plurality of operating components;

a liquid crystal display (LCD) module, comprising;

an illumination source configured to provide an amount of light and a corresponding amount of waste heat, the amount of waste heat being commensurate with the amount of light provided,

a light guide configured to receive and internally disperse at least some of the light provided by the illumination source, and

an LCD cell configured to receive at least some of the internally dispersed light, wherein the LCD cell further comprises a plurality of liquid crystals and a color filter, wherein the liquid crystals respond to a control signal by passing a pre-determined amount of the light received from the light guide to the color filter;

a cover glass layer disposed in front of and in contact with the LCD cell;

a mounting frame for attaching the cover glass layer to the chassis, wherein the mounting frame and the cover glass layer are configured to inhibit a flow of heat between the chassis and the LCD display module; and

a waste heat transport system thermally coupling the LCD module and the chassis, wherein the waste heat transport system transports an amount of the waste heat generated by the LCD module to the chassis sufficient to maintain the LCD module within a pre-selected operating temperature range.

2. The computing device as recited in claim 1, wherein the illumination source further comprises:

a thermally conductive substrate;

a plurality of LED lights thermally coupled to one surface of the thermally conductive substrate; and

electrical traces overlaid on the thermally conductive substrate and configured to deliver power to the LED lights.

3. The computing device as recited in claim 1, the waste heat transport system comprising a graphite layer disposed along a surface of the chassis and thermally coupled to the illumination source, wherein the graphite layer is configured to anisotropically conduct waste heat away from the illumination source by preferentially conducting the waste heat along a length of graphite layer while reducing heat conduction in a direction towards the LCD cell.

4. The computing device as recited in claim 1, wherein the waste heat transport system comprises a plurality of cooling fins configured to increase convection of waste heat away from the illumination source.

5. The computing device as recited in claim 4, wherein the plurality of cooling fins is attached to a heat sink coupled to one or more LED lights.

6. The computing device as recited in claim 1, the waste heat transport system comprising at least one heat pipe thermally coupled to the illumination source and configured to transfer waste heat from the illumination source to a relatively cool region of the LCD module.

7. The computing device as recited in claim 1, the waste heat transport system comprising at least one electrical component thermally coupled to the LCD module and disposed along an edge of the LCD assembly opposite the LED light bar, wherein the electrical component is configured to emit heat such that an approximately uniform temperature is maintained across the LCD cell.

8. The computing device as recited in claim 7, wherein the at least one electrical component comprises at least one driver circuit configured to send signals to the LCD cell.

9. The computing device as recited in claim 1, the waste heat transport system comprising chassis regions of varying thickness configured to conduct heat away from the illumination source and towards a side of the LCD module opposite the illumination source, wherein heat conduction is in proportion to chassis thickness and heat is directed to relatively cooler regions by arranging relatively thicker chassis regions to define a heat path.

10. The computing device as recited in claim 1, further comprising:

an exterior housing configured to enclose the chassis and LCD module;

an inlet disposed in a surface of the exterior housing;

an outlet disposed in a surface of the exterior housing, wherein the inlet and outlet are configured such that an airflow moving from the inlet to the outlet removes waste heat from the illumination source and redistributes the waste heat along a region of the LCD module opposite the illumination source; and

a cooling fan configured to move air through the exterior housing from the inlet to the outlet.

11. The computing device as recited in claim 10, further comprising:

at least one temperature sensor configured to detect a temperature of the illumination source; and

a controller, the controller configured to receive data from the at least one temperature sensor and control the rotation speed of the fan, wherein the controller adjusts the rotation speed of the fan to keep the illumination source within a pre-defined temperature range.

12. A non-transient computer readable medium for storing computer code executable by a processor in a computing device for operating a waste heat transport system configured for maintaining a temperature of a display assembly housed within the computing device within an acceptable operating range, comprising:

computer code for obtaining temperature data from at least one temperature sensor located near the display assembly by the processor;

computer code for using the temperature data from the sensor to generate a control signal;

computer code for passing the control signal from the processor to the waste heat transport system; and

computer code for operating the waste heat transport system to remove an amount of waste heat generated by the display assembly sufficient to maintain an operating temperature of the display assembly within the acceptable operating range.

13. The non-transient computer readable medium as recited in claim 12, wherein the waste heat transport system comprises a fan assembly and wherein the computer readable medium further comprises computer code for controlling the speed of a fan included within the fan assembly, wherein the fan speed is selected to keep the temperature of the illumination source within the range of acceptable temperatures.

14. The non-transient computer readable medium as recited in claim 13, further comprising:

computer code for obtaining temperature data from at least one temperature sensor located near an LCD module included in the computing device; and

computer code for controlling the speed of the fan to maintain an approximately uniform temperature across the LCD module.

15. A method for removing waste heat from an illumination source in a computing device including an LCD module, comprising:

receiving the LCD module, wherein the LCD module includes an LCD cell, a light guide, and the illumination source configured to provide an amount of light and a corresponding amount of waste heat;

enclosing the LCD module in a chassis formed of a thermally conductive material and configured to enclose and support a plurality of operating components; and

thermally coupling the illumination source and the chassis using a waste heat transport system; and

using the waste heat transport system to remove a sufficient amount of waste heat generated by the illumination source in order to maintain the LCD module within a pre-selected operating temperature range.

16. The method as recited in claim 15, wherein the illumination source comprises:

a thermally conductive substrate;

a plurality of LED lights thermally coupled to one surface of the thermally conductive substrate; and

electrical traces overlaid on the thermally conductive substrate and configured to deliver power to the LED lights.

17. The method as recited in claim 15, further comprising providing a graphite layer disposed along a surface of the chassis and thermally coupled to the illumination source, wherein the graphite layer is configured to conduct waste heat away from the illumination source by preferentially conducting the waste heat along a length of the graphite layer while reducing heat conduction in a direction towards the LCD module

18. The method as recited in claim 15, further comprising:

thermally coupling at least one heat pipe containing a liquid kept at a relatively low pressure to the illumination source; and

configuring the liquid and pressure within the heat pipe to transfer waste heat from the illumination source to a relatively cool region of the LCD module.

19. The method as recited in claim 15, further comprising thermally coupling at least one electrical component to the LCD module along an edge of the LCD module opposite the LED light bar, wherein the at least one electrical component is configured to emit heat such that an approximately uniform temperature is maintained across the LCD module.

20. The method as recited in claim 15, further comprising creating regions of varying thickness in the chassis that are configured to draw heat away from the illumination source and towards a side of the LCD module opposite the illumination source, wherein heat conduction is in proportion to chassis thickness and heat is directed to relatively cooler regions by arranging relatively thicker chassis regions to define a heat path.

21. The method as recited in claim 15, further comprising:

housing the LCD module and chassis within an exterior housing;

creating an inlet disposed in a surface of the exterior housing;

creating an outlet disposed in a surface of the exterior housing, wherein the inlet and outlet are configured such that an airflow moving from the inlet to the outlet removes waste heat from the illumination source and redistributes the waste heat along a region of the LCD module opposite the illumination source; and

installing a cooling fan within the exterior housing, wherein the cooling fan is configured to move air through the exterior housing from the inlet to the outlet.