Patent Application
20090137290
This disclosure generally relates to wireless telephones, and more particularly, to a wireless telephone housing that provides enhanced heat dissipation.
Wireless telephones, also referred to as mobile telephones or cellular telephones, have enabled portable communication of individuals with one another. Technological advances have enabled the creation of wireless telephones that are relatively small in size compared to earlier wireless telephone designs. Other technological advances that have been implemented on wireless telephones include various communication services, such as text messaging, e-mail, Internet access, and multi-media services. Use of these communication services in conjunction with the relatively portable nature of known wireless telephone designs have provided enhanced connectivity for individuals.
According to one embodiment of the disclosure, a wireless telephone generally includes a housing and a heat spreading member. The housing encases a plurality of electrical components of the wireless telephone. The heat spreading member is in thermal communication with at least two distally located portions of the housing for reducing a thermal gradient over the surface of the housing.
Some embodiments of the invention provide numerous technical advantages. Some embodiments may benefit from some, none, or all of these advantages. For example, according to one embodiment, heat dissipation may be provided over a relatively larger portion of the wireless telephone housing that may in turn, reduce the effective thermal resistance of the wireless telephone housing. For wireless telephone housings that are typically made of plastic, this distributed heat dissipation may alleviate the formation of hot spots on specific regions of the wireless phone housing during operation of the wireless telephone.
Other technical advantages may be readily ascertained by one of ordinary skill in the art.
A more complete understanding of embodiments of the disclosure will be apparent from the detailed description taken in conjunction with the accompanying drawings in which:
As described previously, a number of communication services have been implemented for use on wireless telephones. One particular communication service that has been implemented on wireless telephones is a multi-media communication service that may include streaming of images to and from the wireless telephone. Viewing of these images has been provided by a liquid crystal display (LCD) screen configured on the housing of the wireless telephone. The liquid crystal display screen, however, may have a relatively limited view area due in large part, to the relatively small physical size of the wireless telephone. Spatial light modulators, such as digital micro-mirror devices, scanning mirrors, liquid crystal on silicon (LCOS) devices, and transmissive liquid crystal displays have been developed that may provide a larger viewing area by enabling projection onto a two-dimensional surface external to the wireless telephone; however, light generating devices used to illuminate these spatial light modulators may generate an undue amount of heat during operation and may therefore, hinder or preclude implementation of these spatial light modulators in the relatively small wireless telephone.
The wireless telephone housing 14 may be configured to dissipate heat generated by any electrical component 12 of the wireless telephone 10. In one embodiment, a particular electrical component 12 of the wireless telephone 10 may be a light generating device 12b that is configured to generate light used by a spatial light modulator 12a to produce the two-dimensional image 22. In another embodiment, spatial light modulator 12a is a digital micro-mirror device (DMD) in which light from light generating device 12b is reflected in order to form the two-dimensional image 22. In one embodiment, the light generating device 12b may be thermally coupled to the housing 14 by being in contact with a portion of the heat pipe 18.
Light generating device 12b may be any device suitable for generating radiant energy in the visual light spectrum. In one embodiment, light generating device 12b may be one or more light emitting diodes. In another embodiment, light generating device 12b may be one or more laser devices. Due to a limited efficiency of operation, these light generating devices 12b may produce heat during operation. For example, a particular laser light source providing sufficient luminous intensity for use with a spatial light modulator 12a may produce approximately 1.0 watt of heat during operation. To dissipate this amount of heat, the light generating device 12b may be thermally coupled to the wireless telephone housing 14. Typical materials from which known wireless telephone housings are made, however, may have relatively poor thermal conductivity and thus cause “hot spots” proximate the portion of the wireless telephone housing 14 that is thermally coupled to the light generating device 12b. Certain embodiments incorporating a heat spreading member, such as heat pipe 18, may provide an advantage in that heat generated by various electrical components 12, such as light generating devices 12b, may be spread over multiple portions of the housing 14 for enhanced dissipation of heat.
In one embodiment, wireless telephone housing 14 may be formed of a generally thermally conductive material, such as magnesium or graphite composition having relatively good thermally conducting properties. In another embodiment, heat pipe 18 may be included to spread heat over various distally separate portions of the housing 14. Heat pipe 18 may be thermally coupled to different portions of the housing 14 using any suitable thermal coupling approach, such as thermally conductive epoxy or thermal grease. In another embodiment, heat pipe 18 may be integrally formed with the wireless telephone housing 14. A heat pipe generally refers to a type of elongated device that may include a liquid/vapor material disposed in an inner cavity for movement of heat using the material's latent heat of vaporization. The heat pipe 18 shown has a generally round cross-sectional shape; however, the heat pipe 18 may have any cross-sectional shape that allows heat to be conveyed along its elongated extent. In one embodiment, the display 20 may be free of contact with the heat pipe 18. That is, the heat pipe 18 may be disposed away from the display 20 of the wireless telephone 10 such that heat transferal from electrical components 12, such as light generating device 12b, to display 20 may be reduced.
In another embodiment, inner lining 36 may be a layer of thermally conductive material that has been cured from a liquid form. Thermally conductive materials of this type may be applied by spraying or brushing the thermally conductive material onto the inner surface of the housing 32. After an elapsed period of time, the thermally conductive material may cure into a solid form and adhere to the housing 32.
In one embodiment, coupling of the housing 32 to the electrical component 12 may be provided by a thermo-electric cooler 40. The thermo-electric cooler 40 is a particular type of electrical device having two ends 42a and 42b that are configured to transfer heat between one another using the Peltier effect. In one embodiment, one end 42b of the thermo-electric cooler 40 is thermally coupled to light generating device 12b and the other end 40a is coupled to the heat spreading member, which in this particular embodiment, is the inner lining 36. When an appropriate electrical power source is applied, the thermo-electric cooler 40 may actively move heat from the light generating device 12b to the housing 32. The thermo-electric cooler 40 is generally referred to as an active thermal device in that heating or cooling of either of its ends 42 may be accomplished by application of an external power source, such as electrical power derived from a battery (not specifically shown) disposed in the wireless telephone housing 32. In one embodiment, the polarity of the thermo-electric cooler 40 may be reversed such that heat may be transferred from the wireless telephone housing 32 to the light generating device 12b. In this manner, the light generating device 12b may be operated in ambient temperatures well below its specified operating range. In some embodiments in which only active heating of light generating device 12b is desired, the active thermal device may be a resistor that is configured to provide heat to the light generating device 12b in order to raise its operating temperature.
Certain embodiments incorporating a thermo-electric cooler 40 for active cooling of electrical components 12, such as light generating devices 12b may provide an advantage in that the operating temperature may be controlled over a wider range than may be provided by passive cooling. For example, a wireless telephone 10 or 30 having a wireless telephone housing 14 or 32 with a thermal resistance of 20 degrees Celsius/Watt (° C./W) and an electrical component 12 that generates 1.0 Watt of heat will operate at 20 degrees Celsius above the ambient environment. If the maximum specified operating temperature of the electrical component 12 is 60 degrees Celsius, then operation of the wireless telephone in ambient environments above 40 degrees Celsius will cause the electrical component 12 to operate beyond its maximum specified operating temperature. However, use of the thermo-electric cooler 40 may allow use in ambient environments above 40 degrees Celsius by actively transferring heat to the housing 14 or 32.
In one embodiment, a controller circuit 34 may be used in conjunction with an active thermal device, such as thermo-electric cooler 40 or a resistor, to regulate the operating temperature of the light generating device 12b. The controller circuit 34 may include a thermal sensor 38 for thermally sensing the temperature of the light generating device 12b. In the event that the operating temperature exceeds an upper threshold temperature, the controller circuit 34 may adjust power to the active thermal device such that the operating temperature of the light generating device 12b is reduced. The controller circuit 34 may also be operable to adjust power to the active thermal device such that the operating temperature is increased if the operating temperature of the light generating device 12b exceeds a lower threshold temperature.
Certain embodiments incorporating an active thermal device, such as a thermo-electric cooler 40 or a resistor may provide an advantage in that the light generating device 12b may be rapidly brought to a desired operating temperature, for example, upon startup. Electrical components 12, such as light generating device 12b used with spatial light modulator 12a on wireless telephone 30 may experience relatively sporadic usage. These devices, however, may require a period of time to warm up to their desired operating temperature when turning from an “off” to an “on” state. Thus, it may be beneficial to actively heat the light generating device 12b to a desired operating temperature such that the latent warm up time of the light generating device 12b may be reduced. Thus, active thermal devices, such as thermo-electric coolers 40 or resistors may be used to reduce the latent warm time of the light generating device 12b in some embodiments.
A wireless phone housing 14 or 32 for a wireless phone 10 or 30 has been described that may enable or enhance use of various electrical components 12 that generate heat during operation. Heat spreading members, such as heat pipes 18 or inner linings 36 provide dissipation of heat generated by the electrical component 12 in such a manner to reduce hot spots that may be harmful or annoying to users of the wireless telephone 10 or 30. Wireless phone housings 14 or 32 configured with active thermal devices may also be controlled by a controller circuit 34 to actively control the operating temperature of various electrical components 12, such as light generating devices 12b. For these light generating devices 12b, the operating temperature may be controlled such that light may be emitted at a relative maximum intensity. Certain embodiments in which the operating temperature of light generating devices 12b are controlled to emit light at a relative maximum intensity may provide an advantage in that a greater amount of light may provide for a corresponding greater image area and/or brightness of the image.
Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the following claims.
