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  Voltage conversion device having non-linear gain and changeable gain polarityUSPTO Application #: 20080100376Title: Voltage conversion device having non-linear gain and changeable gain polarity Abstract: A voltage conversion device having non-linear gain and changeable gain polarity includes a switch module, a gain decision module, a first voltage selection module, a second voltage selection module, a first switch unit, a second switch unit and a voltage output module. The switch module is used for outputting analog voltage provided by the analog voltage source or voltage corresponding to the system ground end. The gain decision module is used for determining a gain. The first voltage selection module is used for outputting a first DC voltage. The second voltage selection module is used for outputting a second DC voltage. The first switch unit is used for outputting the first DC voltage. The second switch unit is used for outputting the second DC voltage. The voltage output module is used for outputting an amplified result of a DC voltage according to the gain. (end of abstract) Agent: North America Intellectual Property Corporation - Merrifield, VA, US Inventor: Chih-Jen Yen USPTO Applicaton #: 20080100376 - Class: 327561 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080100376. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to a voltage conversion device, and more particularly, to a voltage conversion device having non-linear gain and changeable gain polarity. [0003]2. Description of the Prior Art [0004]A liquid crystal display (LCD) monitor has characteristics of light shape, low power consumption, zero radiation, etc. and has been widely used in many information technology (IT) products, such as computer systems, mobile phones, and personal digital assistants (PDAs). The operating principle of the LCD is based on a property that liquid crystals in different twist status can exert different polarization and refraction effects on light. Thus, the liquid crystals arranged in different twist status control penetration amount of light so that various intensity of output light and red, green and blue lights in diverse gray levels can be produced. [0005]Please refer to FIG. 1. FIG. 1 is a schematic diagram of a thin-film-transistor (TFT) LCD monitor 10 according to the prior art. The LCD monitor 10 includes an LCD panel 100, a control circuit 102, a data-line-signal output circuit 104, a scan-line-signal output circuit 106, and a voltage generator 108. The LCD panel 100 is formed with two substrates, and there are LCD layers stuffed between the substrates. One substrate includes a plurality of data lines 110, a plurality of scan lines (or gate lines) 112 vertical to the data lines 110, and a plurality of TFTs 114. The other substrate includes a common electrode for providing a common voltage Vcom generated by the voltage generator 108. For the sake of brevity, FIG. 1 only reveals four TFTs 114, but in a real case, each of TFTs 114 is set at an intersection of a data line 110 and a scan line 112 on the LCD panel 100. In other words, the plurality of TFTs 114, each corresponding to a pixel, form a matrix on the LCD panel 100, and thereby the data lines 110 and the scan lines 112 are corresponding to columns and rows of the matrix. In addition, a circuit effect resulted from the two substrates of the LCD panel 100 can be regarded as equivalent capacitors 116. [0006]A driving process of the prior art TFT LCD monitor 10 is described in detail as follows. When the control circuit 102 receives a horizontal synchronization signal 118 and a vertical synchronization signal 120, the control circuit 102 generates corresponding control signals for the data-line-signal output circuit 104 and the scan-line-signal output circuit 106. The data-line-signal output circuit 104 and the scan-line-signal output circuit 106 generate input signals for the data lines 110 and the scan lines 112 according to the control signals, in order to control the TFTs 114 and voltage differences of the equivalent capacitors 116. The voltage differences change twist of liquid crystals and corresponding penetration amount of light, so as to display the display data 122 on a panel. For example, the scan-line-signal output circuit 106 outputs a pulse wave for turning on a TFT 114, and signals of a corresponding data line 110 outputted from the data-line-signal output circuit 104 can pass through the TFT 114 to a corresponding equivalent capacitor 116, so as to control a gray level of corresponding pixel. Besides, controlling signal levels of the signals on the data line 110 outputted from the data-line-signal output circuit 104 can drive gray levels of corresponding pixels. [0007]In the prior art, in order to reduce EMI and save power under high-frequency operations, voltage swing outputted from the display data 122 is expected to be small, i.e., 0.1V.about.1V. Therefore, signals inputted to the data-line-signal output circuit 104 need to pass through a voltage conversion circuit, which adjusts the voltage swing of the inputted signals to a predetermined range, so as to control chrominance and luminance of corresponding pixels. For example, please refer to FIG. 2, which is a schematic diagram of a voltage conversion circuit 20 according to the prior art. The voltage conversion circuit 20 includes an operational amplifier 200 and resistors 202, 204. The operational amplifier 200 has an input end 206 coupled to an output end of the display data 122, and an output end 208 coupled to an input end of the data-line-signal output circuit 104. As those skilled in the art recognized, if the operational amplifier 200 is an ideal operational amplifier, which has an infinite gain, and resistance of the resistors 202, 204 are R1 and R2, the gain of the voltage conversion circuit 20 can be derived as a value, (1+R2/R1). In other words, the relation between the input and output voltages of the voltage conversion circuit 20 is corresponding to a linear function. [0008]Therefore, data signals outputted from the display data 122 are amplified via the voltage conversion circuit 20 and then are outputted to the data-line-signal output circuit 104. Under this circumstance, via the voltage conversion circuit 20 of the prior art, data-line signals outputted from the data-line-signal output circuit 104 are linearly amplified to an operating range of the TFTs 114, so that the relation between the gray level and brightness displayed on the TFT LCD monitor 10 is approximate to a linear line, which effects color gradient of images and results in unnatural display images. [0009]Besides, regarding LCD monitors, an event related to necessity of inverting polarity of output voltage also has to be taken into consideration. For an LCD monitor, continuously using a positive or negative polarity voltage to drive liquid crystals will decrease ability of the liquid crystals to polarize or reflect light, which makes image quality worse. Thus, in order to prevent the liquid crystals from breakage resulted from the driving voltage, using the positive and negative polarity voltages to alternately drive the liquid crystals is required. Furthermore, in addition to the equivalent capacitors, the circuit itself produces parasitic capacitors. When an image is displayed on the LCD panel for a long time, the parasitic capacitors may result in a residual image effect due to storage charge and further affect the follow-up image displaying. Therefore, the positive and negative polarity voltages must drive the liquid crystals in an alternate manner, such as methods of line inversion, dot inversion, and etc., so as to improve the effect mentioned above. That is to say, polarity of the data-line signals outputted from the data-line-signal output circuit can be inverted timely to prevent from the residual image effect or breakage of the liquid crystals. [0010]Therefore, the voltage conversion circuit 20 of the prior art linearly amplifies the signals outputted by the display data 122, so that the relation between the gray levels and brightness displayed by the TFT LCD monitor 10 is approximate to a linear function, resulting in bad color gradient and unnatural images. Besides, the voltage conversion circuit 20 cannot provide a driving operation of alternating the positive and negative polarity voltages for inverting the data-line signals outputted from the data-line-signal output circuit 104. Therefore, problems of the residual image effect and breakage of the liquid crystals may easily occur in the TFT LCD monitor 10. SUMMARY OF THE INVENTION [0011]It is therefore a primary object of the present invention to provide a voltage conversion device having non-linear gain and changeable gain polarity. [0012]The present invention discloses a voltage conversion device having non-linear gain and changeable gain polarity, for converting analog voltage provided by an analog voltage source. The voltage conversion device includes a switch module, a gain decision module, a first voltage selection module, a second voltage selection module, and a voltage output module. The switch module is coupled to the analog voltage source and a system ground end and is used for outputting analog voltage provided by the analog voltage source or voltage corresponding to the system ground end according to a polarity selection signal. The gain decision module includes an analog-to-digital (A/D) converter and a gain selector. The A/D converter is coupled to the analog voltage source and is used for converting analog voltage provided by the analog voltage source into digital signals. The gain selector is coupled to the A/D converter and the switch module and is used for determining a gain according to the digital signals outputted from the A/D converter. The first voltage selection module is coupled to the A/D converter and is used for outputting a first direct-current (DC) voltage selected from a plurality of DC voltages according to the digital signals outputted from the A/D converter. The second voltage selection module is coupled to the analog voltage source and the A/D converter and is used for outputting a second DC voltage selected according to analog voltage provided by the analog voltage source, a plurality of DC voltages and the digital signals outputted from the A/D converter. The first switch unit is coupled to the first voltage selection module and is used for outputting the first DC voltage according to the polarity selection signal. The second switch unit is coupled to the second voltage selection module and is used for outputting the second DC voltage according to the polarity selection signal. The voltage output module has a first input end, an output end coupled to the gain selector, and a second input end coupled to the first switch unit and the second switch unit. The voltage output module is used for outputting an amplified result of the DC voltage received by the second input end according to the gain determined by the gain selector. [0013]The present invention further discloses a voltage conversion device having non-linear gain and changeable gain polarity, for converting analog voltage provided by an analog voltage source. The voltage conversion device includes a switch module, a gain decision, and a voltage output module. The switch module is coupled to the analog voltage source and a plurality of direct-current (DC) voltage sources. Besides, the switch module has a first output end and a second output end and is used for determining to output analog voltage provided by the analog voltage source from the first output end and one of the DC voltage sources from the second output end, or to output one of the DC voltage sources from the first output end and analog voltage provided by the analog voltage source from the second output end according to a polarity selection signal. The gain decision module includes an analog-to-digital (A/D) converter and a gain selector. The A/D converter is coupled to the analog voltage source and is used for converting analog voltage provided by the analog voltage source into digital signals. The gain selector is coupled to the A/D converter and the first output end of the switch module and is used for determining a gain according to the digital signals outputted from the A/D converter and voltage outputted from the first output end of the switch module. The voltage output module includes a first input end, an output end coupled to the gain selector, and a second input end coupled to the second output end of the switch module. In addition, the voltage output module is used for outputting an amplified result of the DC voltage received by the second input end according to the gain determined by the gain selector. [0014]These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0015]FIG. 1 is a schematic diagram of a thin-film-transistor (TFT) LCD according to the prior art. [0016]FIG. 2 is a schematic diagram of a voltage conversion circuit according to the prior art. [0017]FIG. 3 is a schematic diagram of a voltage conversion device according to an embodiment of the present invention. [0018]FIG. 4 is a schematic diagram of an A/D converter. [0019]FIG. 5 is a schematic diagram of a gain selector. [0020]FIG. 6 is a schematic diagram of a gain selector. [0021]FIG. 7 is a schematic diagram of a first voltage selection module. Continue reading... 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