Patent Application
20070024214
High efficiency illumination sources, such as those used in projector systems, industrial lighting fixtures, stadium lighting, and so forth, may make use of a metal halide vapor that is electrically excited in order to produce light. To activate the illumination source, a ballast or other device is used to deliver a controlled current and voltage waveform to the illumination source. The waveforms typically begin with an initial high-voltage segment that activates the illumination source while the source is preferably in a “cold” state. Subsequently, the voltage delivered to the illumination source is reduced as the illumination source assumes steady-state operation.
When the input power to a high efficiency metal vapor illumination source is removed, sufficient time should be allowed before restarting the illumination source so that the metal halide vapor can be allowed to condense. If the illumination source is not allowed to sufficiently cool before being reactivated, the presence of a large voltage at the input to the source can cause a large current to flow through the metal halide vapor. These high-current and high-voltage events can damage the electrodes within the illumination source, thus causing the lamp to fail or to significantly reduce the operating life of the illumination source.
Embodiments of the invention can prevent damage to the illumination source caused by the user attempting to “hot start” a high efficiency metal halide vapor illumination source. This can be especially useful in low cost digital projector systems in which a premium is placed on maximizing the operating life of the illumination source. In these systems, the premature replacement of damaged or inoperative illumination sources can substantially increase the cost of ownership of the projector system.
In projector system 100, illumination source 150 represents a high efficiency illumination source which may use mercury vapor or any other type of metal halide. However, it is contemplated that regardless of the precise nature of illumination source 150, the illumination source operates at an elevated temperature, thereby requiring (or at least benefiting from) reversible fan 170 directing an air current across at least a portion of illumination source 150. It is further contemplated that regardless of the precise nature of illumination source 150, the operating life of the source is degraded when the user attempts to activate the source prior to allowing sufficient time for the source to cool down from an elevated temperature resulting from previous use. This can occur when a user inadvertently depresses on/off switch 110, thereby removing power from illumination source 150, and then attempts to immediately reactivate the illumination source.
In the embodiment of
In the event that the temperature of the air current is greater than a predetermined value, indicating that activating illumination source 150 may cause damage to the illumination source, logic module 120 delays the operation of ballast 140 to allow sufficient time for the illumination source to cool below a predetermined temperature. When logic module 120 determines that illumination source 150 can be safely activated, either by measuring real-time outputs of temperature 130, or by simply allowing reversible fan 170 to operate for a given length of time as determined by timer 220, logic module 120 causes ballast 140 to begin conveying the appropriate voltage and current waveform to activate illumination source 150. For most home entertainment and enterprise usage environments, is contemplated that the activation of illumination source 150 be delayed only by 10 to 15 seconds to allow the source to achieve a suitably low temperature.
After sensing the temperature of illumination source 150, reversible fan 170 directs air in an opposite direction in a manner that allows an air current to flow across at least a portion of ballast 140 and over illumination source 150. The air current is then directed outside of the enclosure of projector system 100 by way of vent 190. By way of this reversal in the direction of the air current, the operating temperature of ballast 140 can be sensed using temperature sensor 130. It is contemplated that by way of sensing the temperature of ballast 140, logic module 120 can assess the general condition of ballast 140. Thus, in the event that illumination source 150 is drawing excessive current, indicating the irregular or unusual operation of illumination source 150, this condition can be detected by way of sensing the temperature of ballast 140. Logic module 120 may then determine that ballast 140 should be switched off so as to prevent damage to the ballast or to limit damage to the illumination source.
The embodiment of
In the event that the temperature of the air current is below a predetermined value, step 290 is performed in which the direction of the airflow is reversed. The reversal in the direction of the airflow of step 290 represents the steady-state operating condition in which air is directed to remove heat from locations inside the projector or display system to a location external to the enclosure. In step 300, the illumination source is activated, perhaps by applying a high voltage signal to the illumination source. At step 310, the temperature of the air flowing across the ballast is sensed. As mentioned in reference to
In the event that the outcome of step 280 indicates that the temperature of the illumination source is greater than a predetermined value, step 330 is performed in which the direction of the airflow is reversed. As mentioned in reference to step 290, the reversal in the direction of the airflow represents the steady-state operating condition in which air is directed in manner that removes heat from locations inside the projector or display system to a location external to the enclosure. Step 340 is then performed in which, perhaps as a function of the measured temperature of the air flow from the illumination source, an illumination source cooling algorithm is performed. In some embodiments of the invention, the algorithm may be as simple as delaying step 300, in which the illumination source is activated, for 10 or 15 seconds to allow the illumination source to cool. Other embodiments of the invention may include delaying performing step 300 for a variable period of time as a function of the temperature sensed at step 270. After the illumination source is activated in step 300, step 310 is performed in which the temperature of the air flowing across the ballast is measured.
In some embodiments of the invention, not all of the steps of
In response to receiving the signal of step 350, step 360 is performed in which the logic module initiates operation of a device that directs air in a first direction, such as reversible fan 170 of
In the event that the decision of step 375 indicates that the illumination source is above a predetermined temperature, step 400 is performed, which includes directing the air current in the opposite direction so as to direct air from inside the enclosure housing the illumination source to a location outside of the enclosure. It is contemplated that in at least some embodiments of the invention, step 410 includes a fixed delay of 10 or more seconds before activating the illumination source. After the 10 or more seconds (or other fixed time period) has elapsed, the illumination source is activated.
In some embodiments of the invention, not all of the steps of
In conclusion, while the present invention has been particularly shown and described with reference to various embodiments, those skilled in the art will understand that many variations may be made therein without departing from the spirit and scope of the invention as defined in the following claims. This description of the invention should be understood to include the novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later patent application to any novel and non-obvious combination of these elements. The foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later patent application. Where the claims recite “a” or “a first” element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.
