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Patent Issued for Discharge Lamp System, Method and Apparatus of Controlling the Transition Time of Discharge Lamp Current Change

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Zhang, Qi (Shanghai, CN); Zhang, Wei-Qiang (Shanghai, CN); Ying, Jian-Ping (Shanghai, CN), filed on September 30, 2011, was published online on July 8, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8773039 is assigned to Delta Electronics (Shanghai) Co., Ltd. (Shanghai, CN).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present disclosure relates to a control mechanism of a discharge lamp, and more particularly, a method, a device and a system of controlling the discharge lamp for projection.

"Present projection device products are full of diversities, a digital light processing (DLP) projection device, a liquid crystal projection device (LCD) and a reflective single-crystal silicon (LCOS) projection device are provided to different groups of consumers respectively. The digital light processing (DLP) projection device preferably uses discharge lamps generating light for projection, and more particularly, uses high-intensity discharge lamps (HID). In the digital light processing projection device, a color filter constructed by a color wheel with three primary colors of R, B, G (R for Red, B for Blue, G for green) rotates to pass light from light sources to sequentially generate beams of three primary colors and control spatial modulating elements simultaneously, thereby images are sequentially generated according to each of the three primary colors by time division, and color images are displayed. For a color filter of 3 colors, due to essential differences of various color lights and different requirements for brightness of various color lights, for example, if one of 3 colors appears again with different brightness comparing to other colors or if brightness in a specific image area is different from brightness in other image areas, then the requirement for the light intensity of the discharge lamp is different so that the required current of the discharge lamp is different. As shown in FIG. 1, FIG. 1 is a diagram of a discharge lamp current corresponding to each color of a color filter of 3 colors. As shown in FIG. 1, there are a difference .DELTA.I between a discharge lamp current corresponding to B color and a discharge lamp current corresponding to R color and a difference .DELTA.I' between a discharge lamp current corresponding to B color and a discharge lamp current corresponding to G color. On the other hand, in FIG. 1, the operation that the discharge lamp current corresponding to R color changes to the discharge lamp current corresponding to B color and the operation that the discharge lamp current corresponding to B color changes to the discharge lamp current corresponding to G color both require for a certain time period, i.e., transition time periods tr, tf, in which a previous light color changes to a latter light color during the transition time period, i.e., the intensity of light emitted by the discharge lamp would change during the transition time. Since the intensity of light emitted by the discharge lamp would change during the transition time, the light emitted by the discharge lamp during the transition time is not used for projection in order to reduce influence on quality of image, and this will result in waste of energy. Therefore, the transition time is better to be shorter to enhance the efficiency of light emitted by the discharge lamp and to save energy as well.

"Therefore, how to invent a method and a device for controlling a discharge lamp and to shorten a transition time during which a discharge lamp changes from one color to another color are problems that need to solve."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "One aspect of the present disclosure is to control a discharge lamp for shortening the transition time and decreasing the oscillation when the lamp current changes.

"The present disclosure provides a method for controlling a discharge lamp that includes a) receiving a synchronous signal; b) determining whether a lamp current of the discharge lamp changes or not according to the synchronous signal; c) when the lamp current changes, determining a is percentage of change of the lamp current according to the synchronous signal and obtaining a second lamp current after the discharge lamp current changes according to the percentage of change of the lamp current and a first lamp current before the discharge lamp current changes; d) calculating a current difference between the second lamp current and the first lamp current; e) obtaining a modulating signal according to the current difference; and f) generating a pulse voltage signal is and outputting a switch control signal according to a lamp current detecting signal, an average lamp current signal and the modulating signal so as to control the lamp current of the discharge lamp. The pulse voltage signal comprises at least a first voltage, a second voltage and a time period. The pulse voltage signal transits from the first voltage to the second voltage during the time period when the lamp current is transited from the first lamp current to the second lamp current during a transition time, and the transition time and/or current difference between the second lamp current and the first lamp current is controlled by regulating a value of the second voltage and the time period.

"According to one embodiment, the second voltage is larger than the first voltage when change of the lamp current is positive going, and the second voltage is smaller than the first voltage when change of the lamp current is negative going.

"According to one embodiment, the time period of the pulse voltage signal is divided into a first sub time period and a second sub time period, the pulse voltage signal comprises at least a third voltage, the pulse voltage signal changes from the first voltage to the third voltage during the first sub time period, and the pulse voltage signal changes from the third voltage to the second voltage during the second sub time period.

"According to one embodiment, the third voltage is larger than the second voltage.

"According to one embodiment, the third voltage is smaller than the second voltage.

"According to one embodiment, the range of the time period is between about 1 microsecond (us) to 3 times the maximum of the transition time.

"According to one embodiment, the first sub time period and/or the second sub time period are/is larger or equal to zero.

"According to one embodiment, the transition time and/or the second lamp current is controlled by modulating the second voltage value and/or the third voltage value and/or the first sub time period and/or the second sub time period.

"One aspect of the present disclosure is to provide a controlling device for controlling a discharge lamp. The controlling device comprises a microprocessor and a control circuit. The microprocessor is used to receive a synchronous signal and a lamp state detecting signal and generate an average lamp current signal and generate a modulating signal according to a difference between a second lamp current and a first lamp current. The control circuit is electrically connected to the microprocessor and used to receive a lamp current detecting signal, the average lamp current signal and the modulating signal, and generate a pulse voltage signal so as to output a switch control signal to control a discharge lamp current. The pulse voltage signal comprises at least a first voltage, a second voltage and a time period, the pulse voltage signal transits from the first voltage to the second voltage during the time period when the lamp current needs to transit from the first lamp current to the second lamp current during a transition time, and the transition time and/or current difference between the second lamp current and the first lamp current is controlled by modulating a second voltage value and the time period.

"According to one embodiment, the second voltage is larger than the first voltage when change of the lamp current is positive going, and the second voltage is smaller than the first voltage when change of the lamp current is negative going.

"According to one embodiment, the time period of the pulse voltage signal is divided into a first sub time period and a second sub time period, the pulse voltage signal comprises at least a third voltage, the pulse voltage signal changes from the first voltage to the third voltage during the first sub time period, and the pulse voltage signal changes from the third voltage to the second voltage during the second sub time period.

"According to one embodiment, the first sub time period and/or the second sub time period are/is larger or equal to zero.

"According to one embodiment, the third voltage is larger than the second voltage.

"According to one embodiment, the third voltage is smaller than the second voltage.

"According to one embodiment, the transition time and/or the second lamp current is controlled by modulating the second voltage value and/or the third voltage value and/or the first sub time period and/or the second sub time period.

"According to one embodiment, the range of the time period is between about 1 microsecond (us) to 3 times more than maximum of the transition time.

"According to one embodiment, the microprocessor includes a microprocessing unit, a first digital to analog converter, and a second digital to analog converter. The microprocessing unit includes a determining unit for determining whether a lamp current of the discharge lamp changes or not according to the synchronous signal and obtaining a percentage of change of the lamp current of the discharge lamp when the lamp current changes and a calculating unit for calculating a second lamp current of the discharge lamp and a current difference between the second lamp current and the first lamp current according to the percentage of change of the lamp current of the discharge lamp and the first lamp current of the discharge lamp, and for responsively generating a first digital signal and a second digital signal. The first digital to analog converter is used to convert the first digital signal to the average lamp current signal. The second digital to analog converter is used to convert the second digital signal to the modulating signal.

"According to one embodiment, the control circuit further includes a superposition circuit for superpoing the average lamp current signal on the modulating signal so as to output the pulse voltage signal, a secondoperational amplifier having a non-inverting input, an inverting input and an output, for receiving the pulse voltage signal and the lamp current detecting signal so as to generate an error signal, and a pulse width modulation signal generator connected to the output of the first operational amplifier, for generating a switch control signal.

"According to one embodiment, the control circuit further includes a lamp current processing circuit for receiving the lamp current detecting signal and the modulating signal so as to generate a pulse voltage signal, a third operational amplifier electrically connected to the lamp current processing circuit and the microprocessor to receive the pulse voltage signal and the average lamp current signal so as to generate an error signal, and the pulse modulation signal generator connected to the output of the third operational amplifier, for generating the switch control signal.

"According to one embodiment, the modulating signal is obtained such that the pulse voltage signal is obtained according to a difference between the second lamp current and the first lamp current and the lamp state detecting signal, the lamp state detecting signal is a signal responsive to a lamp voltage state including lamp voltage and a duty ratio of the switch control signal.

"Yet another aspect of the present disclosure is to provide a discharge lamp system. The discharge lamp system comprising a discharge lamp, a power supply device used to provide a DC power, a converter including at least a switch, electrically connected to the power supply device and the discharge lamp and used to convert the DC power to the discharge lamp current, a lamp state signal detecting circuit used to detect a lamp state of the discharge lamp to generate a lamp state detecting signal, and a controlling device which is the controlling device in another embodiment of the present invention.

"According to one embodiment, the converter is a DC-DC converter.

"According to one embodiment, the converter further includes a DC-AC inverter.

"According to one embodiment, the lamp state detecting signal is a lamp voltage signal, a lamp current signal, a lamp power signal, the transistor duty ratio signal, an input voltage signal, an input current signal or an input power signal.

"By applying the method, the device and the discharge lamp system, the pulse voltage signal required for controlling the discharge lamp to change from having a first lamp current to having a second lamp current is obtained by the lamp current and the transition time before and after the lamp current changes. When the lamp current of the discharge lamp changes from the first lamp current to the second lamp current, the pulse voltage signal for controlling the change of the lamp current transits from a first voltage to a second voltage during a time period. The transition time of change of the lamp current is significantly decreased so that unnecessary light emitted by the discharge lamp during the transition time is decreased and thus the power is saved. Furthermore, the time period that the pulse voltage signal changes is added so that the change of lamp current of the discharge lamp can become more stable."

URL and more information on this patent, see: Zhang, Qi; Zhang, Wei-Qiang; Ying, Jian-Ping. Discharge Lamp System, Method and Apparatus of Controlling the Transition Time of Discharge Lamp Current Change. U.S. Patent Number 8773039, filed September 30, 2011, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8773039.PN.&OS=PN/8773039RS=PN/8773039

Keywords for this news article include: Microprocessors, Delta Electronics, Digital To Analog.

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Source: Electronics Newsweekly


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