Digital liquid crystal display driving circuit

Abstract

A digital liquid crystal display (LCD) driving circuit is provided for driving an LCD to display video images. The LCD driving circuit comprises a digital gamma-correction and inversion circuit for performing a digital gamma-correction process on the digitized video signal and then performing a polarity inversion process on selected lines of the video signal. The digital gamma-correction and inversion circuit is coupled directly to a display memory unit so as to fetch the digitized video signal directly from the display memory unit. A digital-to-analog conversion means is coupled to the digital gamma-correction and inversion circuit for converting the digital output of the digital gamma-correction and inversion circuit into analog form. Further, the LCD driving circuit comprises an LCD timing control circuit, which is coupled to receive a plurality of video control signals associated with the digitized video signal, for converting the video control signals into a LCD timing control signal to control the LCD to display the video signal. Still further, the LCD driving circuit comprises a PWM and shutdown circuit for supplying power to the LCD and shutting down the LCD when the LCD has been idle for a preset period. Most of the constituent circuit components of the LCD driving circuit can be implemented in a single LSI integrated circuit. The LCD driving circuit is therefore compact in size, low in manufacturing cost, and low in power consumption.

1. An LCD driving circuit for driving an LCD to display a video image, comprising:
 a digital gamma-correction and inversion circuit, coupled to directly receive a digitized video signal from a display memory, for performing a digital gamma-correction process on the digitized video signal and then performing a polarity inversion process on selected lines of the gamma corrected video signal;  
 a digital-to-analog conversion means, coupled to said digital gamma-correction and inversion circuit, for converting the digital output of said digital gamma-correction and inversion circuit into analog form; and  
 an LCD timing control circuit, coupled to an external time control circuit, said digital gamma-correction and inversion circuit, and said digital conversion means, to directly receive a plurality of video control signals associated with the digitized video signal, for converting the video control signals into an LCD timing control signal to control the display of the digitized video signal on the LCD; and  
 a PWM and shutdown circuit for supplying power to the LCD and shutting down the LCD when the LCD has been idle for a preset period.  
 
     
     
       2. The LCD driving circuit of  claim 1 , wherein said digital gamma-correction and inversion circuit is coupled to a display memory unit in which the data of the digitized video signal are stored, so as to fetch the digitized video signal directly from said display memory unit. 
     
     
       3. The LCD driving circuit of  claim 1 , wherein said plurality of video control signals received by said LCD timing control circuit include a horizontal synchronizing signal, a vertical synchronizing signal and a pixel clock signal. 
     
     
       4. The LCD driving circuit of  claim 1 , wherein said LCD timing control circuit comprises a means for setting a user-desired resolution for the LCD to display the video image based on a logic signal representative of the user-set resolution. 
     
     
       5. The LCD driving circuit of  claim 1 , wherein said PWM and shutdown circuit is used in conjunction with a filtering circuit to convert an input DC voltage to the power required to drive the LCD and said PWM and shutdown circuit shuts down the LCD in response to a shutdown trigger signal. 
     
     
       6. The LCD driving circuit of  claim 1 , wherein said digital gamma-correction and inversion circuit performs the polarity inversion process in such a manner that odd-numbered lines are positively polarized while even-numbered lines are negatively polarized. 
     
     
       7. An LCD driving circuit for driving an LCD to display a video image, comprising:
 a digital gamma-correction and inversion circuit, coupled to directly receive a digitized video signal from a display memory, for performing a digital gamma-correction process on the digitized video signal and then performing a polarity inversion process on selected lines of the gamma corrected video signal;  
 a digital-to-analog conversion means, coupled to said digital gamma-correction and inversion circuit, for converting the digital output of said digital gamma-correction and inversion circuit into analog form; and  
 an LCD timing control circuit, coupled to an external time control circuit, said digital gamma-correction and inversion circuit, and said digital conversion means, to directly receive a plurality of video control signals associated with the digitized video signal, for converting the video control signals into an LCD timing control signal to control the display of the digitized video signal on the LCD.  
 
     
     
       8. The LCD driving circuit of  claim 7 , further comprising a PWM and shutdown circuit, wherein said PWM and shutdown circuit is used in conjunction with a filtering circuit to convert an input DC voltage to the power required to drive the LCD and said PWM and shutdown circuit shuts down the LCD in response to a shutdown trigger signal. 
     
     
       9. The LCD driving circuit of  claim 7 , wherein said digital gamma-correction and inversion circuit is coupled to a display memory unit in which the data of the digitized video signal are stored, so as to fetch the digitized video signal directly from said display memory unit. 
     
     
       10. The LCD driving circuit of  claim 7 , wherein said plurality of video control signals received by said LCD timing control circuit include a horizontal synchronizing signal, a vertical synchronizing signal and a pixel clock signal. 
     
     
       11. The LCD driving circuit of  claim 7 , wherein said LCD timing control circuit comprises:
 means for setting a user-desired resolution for the LCD to display the video image based on a logic signal representative of the user-set resolution.  
 
     
     
       12. A method for driving an LCD to display a video signal, comprising the steps of:
   directly receiving a digital video signal from a display memory; converting a gamma corrected and signal inverted version of the directly received digital video signal to a video signal in analog form for display by an LCD; directly receiving video control signals that control the directly received digital video signal; driving the LCD with the video control signals; supplying power to an LCD that displays the video signal in analog form; and shutting down the LCD when the LCD has been idle for a preset period.     
     
     
       13. A method for driving an LCD to display a video image, comprising the steps of:
   receiving a digitized video signal and a plurality of video control signals, respectively, in an LCD driving circuit to drive the LCD to display the video image; performing gamma - correction and polarity inversion in the LCD driving circuit on the digitized video signal to generate a digital output to achieve gamma - correction for the video image to be displayed on the LCD, and to make neighboring lines of the LCD opposite in polarity; and processing the video control signals in an LCD timing control circuit of the LCD driving circuit to generate video control signals for driving the LCD; wherein the LCD driving circuit further comprises a PWM and shutdown circuit, and wherein the method further comprises; receiving an external voltage in the PWM and shutdown circuit; and converting the external voltage in the PWM and shutdown circuit to a DC voltage to power the LCD.     
     
     
       14. The method of  claim 13 , wherein the PWM and shutdown circuit receives a shut down trigger signal input to generate a signal to shut down the LCD. 
     
     
       15. An LCD driving circuit to drive an LCD to display a video image, comprising:
   a gamma - correction and inversion circuit for receiving a digitized video signal and performing gamma - correction and polarity inversion of the digitized video signal to generate a digital output, to achieve gamma - correction for the video image to be displayed on the LCD, and to make neighboring lines of the LCD opposite in polarity; an LCD timing control circuit for receiving and processing video control signals to generate a video timing signal to drive the LCD; and a PWM and shutdown circuit for receiving and converting an external voltage to a DC voltage to power the LCD.     
     
     
       16. An LCD driving circuit to drive an LCD to display a video image, comprising:
   a gamma - correction and inversion circuit for receiving a digitized video signal and performing gamma - correction and polarity inversion of the digitized video signal to generate a digital output, to achieve gamma - correction for the video image to be displayed on the LCD, and to make neighboring lines of the LCD opposite in polarity; an LCD timing control circuit for receiving and processing video control signals to generate a video timing signal to drive the LCD; and a PWM and shut down circuit for receiving and converting an external voltage into an LCD timing and control signal to control the display of the video image on the LCD.     
     
     
       17. An LSI circuit for driving an LCD to display a video image, comprising:
   a digital gamma - correction and inversion circuit receiving a digitized video signal, and performing digital gamma - correction and polarity inversion of the digitized video signal to provide a digital output;        a digital - to - analog conversion circuit converting the digital output of said gamma - correction and inversion circuit into analog form corresponding to a video image to be displayed;        an LCD timing control circuit receiving a plurality of timing control signals and providing timing control to said digital gamma - correction and inversion circuit, said digital - to - analog conversion circuit and the LCD; and        a PWM and shutdown circuit supplying power to the LCD and shutting down the LCD when the LCD has been idle for a preset period.     
     
     
       18. A method of driving an LCD to display a video image, comprising:
   providing in an LSI circuit with a digital gamma - correction and inversion circuit, a digital - to - analog conversion circuit coupled to said digital gamma - correction and inversion circuit, an LCD timing control circuit, and a PWM and shutdown circuit;        receiving a digitized video signal by the digital gamma - correction and inversion circuit, and performing digital gamma - correction and polarity inversion of the digitized video signal to provide a digital output;        converting the digital output of said digital gamma - correction and inversion circuit into analog form by the digital - to - analog conversion circuit wherein the analog form corresponds to a video image to be displayed; and        receiving a plurality of timing control signals by the LCD timing control circuit, and providing timing control by the LCD timing control circuit of said digital gamma - correction and inversion circuit, said digital conversion circuit and the LCD; and        supplying power to the LCD the PWM and shutdown circuit, and shutting down the LCD by the PWM and shutdown circuit when the LCD has been idle for a preset period.