Common voltage generation circuit, power supply circuit, display driver, and common voltage generation method

Abstract

A common voltage generation circuit includes a first operational amplifier which outputs an amplitude voltage of a common voltage based on a first power supply voltage, a second operational amplifier which outputs a high-potential-side voltage of the common voltage based on the first power supply voltage, and a low-potential-side voltage generation circuit which generates a low-potential-side voltage of the common voltage which is lower in potential than the high-potential-side voltage for the amplitude voltage by a charge-pump operation. The common voltage generation circuit supplies the high-potential-side voltage or the low-potential-side voltage to a common electrode which faces a pixel electrode specified by a scan line and a data line of an electro-optical device through an electro-optical substance.

1 . A common voltage generation circuit for generating a common voltage applied to a common electrode which faces a pixel electrode specified by a scan line and a data line of an electro-optical device through an electro-optical substance, the common voltage generation circuit comprising: 
 a first operational amplifier which outputs an amplitude voltage of the common voltage based on a first power supply voltage;    a second operational amplifier which outputs a high-potential-side voltage of the common voltage based on the first power supply voltage; and    a low-potential-side voltage generation circuit which generates a low-potential-side voltage of the common voltage by a charge-pump operation and supplies the low-potential-side voltage to a backup capacitor, to which a first voltage is supplied at one end, at the other end, the low-potential-side voltage being lower in potential than the high-potential-side voltage for the amplitude voltage,    wherein the common voltage generation circuit supplies the high-potential-side voltage or the low-potential-side voltage to the common electrode.    
   
   
       2 . A common voltage generation circuit for generating a common voltage applied to a common electrode which faces a pixel electrode specified by a scan line and a data line of an electro-optical device through an electro-optical substance, the common voltage generation circuit comprising: 
 a first operational amplifier which outputs an amplitude voltage of the common voltage based on a first power supply voltage;    a second operational amplifier which outputs a high-potential-side voltage of the common voltage based on the first power supply voltage; and    a low-potential-side voltage generation circuit which generates a low-potential-side voltage of the common voltage by a charge-pump operation which causes the high-potential-side voltage to be supplied to one end of a flying capacitor which stores an electric charge corresponding to a voltage difference between the first power supply voltage and the amplitude voltage, the low-potential-side voltage being lower in potential than the high-potential-side voltage for the amplitude voltage,    wherein the common voltage generation circuit supplies the high-potential-side voltage or the low-potential-side voltage to the common electrode.    
   
   
       3 . The common voltage generation circuit as defined in  claim 1 , 
 wherein the low-potential-side voltage generation circuit includes:    first and second switch elements connected in series; and    third and fourth switch elements connected in series,    wherein the amplitude voltage is supplied to one end of the first switch element,    wherein the high-potential-side voltage is supplied to one end of the second switch element,    wherein the first power supply voltage is supplied to one end of the third switch element,    wherein the first power supply voltage is supplied to one end of the backup capacitor,    wherein, in a first period, the first switch element is turned on and the second switch element is turned off to supply the amplitude voltage to one end of a flying capacitor, and the third switch element is turned on and the fourth switch element is turned off, and    wherein, in a second period subsequent to the first period, the first switch element is turned off and the second switch element is turned on to supply the high-potential-side voltage to one end of the flying capacitor, and the third switch element is turned off and the fourth switch element is turned on to supply a voltage of the other end of the flying capacitor to the other end of the backup capacitor.    
   
   
       4 . The common voltage generation circuit as defined in  claim 2 , 
 wherein the low-potential-side voltage generation circuit includes:    first and second switch elements connected in series; and    third and fourth switch elements connected in series,    wherein the amplitude voltage is supplied to one end of the first switch element,    wherein the high-potential-side voltage is supplied to one end of the second switch element,    wherein the first power supply voltage is supplied to one end of the third switch element,    wherein the first power supply voltage is supplied to one end of the backup capacitor,    wherein, in a first period, the first switch element is turned on and the second switch element is turned off to supply the amplitude voltage to one end of a flying capacitor, and the third switch element is turned on and the fourth switch element is turned off, and    wherein, in a second period subsequent to the first period, the first switch element is turned off and the second switch element is turned on to supply the high-potential-side voltage to one end of the flying capacitor, and the third switch element is turned off and the fourth switch element is turned on to supply a voltage of the other end of the flying capacitor to the other end of the backup capacitor.    
   
   
       5 . The common voltage generation circuit as defined in  claim 3 , 
 wherein the first and second switch elements are MOS transistors, amplitude of gate voltages of the MOS transistors which form the first and second switch elements being greater than a voltage difference between the amplitude voltage and the high-potential-side voltage, and    wherein the third and fourth switch elements are MOS transistors, amplitude of gate voltages of the MOS transistors which form the third and fourth switch elements being greater than a voltage difference between the first power supply voltage and the low-potential-side voltage.    
   
   
       6 . The common voltage generation circuit as defined in  claim 4 , 
 wherein the first and second switch elements are MOS transistors, amplitude of gate voltages of the MOS transistors which form the first and second switch elements being greater than a voltage difference between the amplitude voltage and the high-potential-side voltage, and    wherein the third and fourth switch elements are MOS transistors, amplitude of gate voltages of the MOS transistors which form the third and fourth switch elements being greater than a voltage difference between the first power supply voltage and the low-potential-side voltage.    
   
   
       7 . The common voltage generation circuit as defined in  claim 5 , 
 wherein the amplitude of the gate voltages of the MOS transistors which form the first to fourth switch elements is the same as amplitude of a scan voltage applied to the scan line.    
   
   
       8 . The common voltage generation circuit as defined in  claim 6 , 
 wherein the amplitude of the gate voltages of the MOS transistors which form the first to fourth switch elements is the same as amplitude of a scan voltage applied to the scan line.    
   
   
       9 . The common voltage generation circuit as defined in  claim 1 , 
 wherein the second operational amplifier is a voltage-follower-connected operational amplifier, output of the second operational amplifier being driven by an n-channel driver transistor, and    wherein the amplitude voltage is a potential higher than the high-potential-side voltage.    
   
   
       10 . The common voltage generation circuit as defined in  claim 2 , 
 wherein the second operational amplifier is a voltage-follower-connected operational amplifier, output of the second operational amplifier being driven by an n-channel driver transistor, and    wherein the amplitude voltage is a potential higher than the high-potential-side voltage.    
   
   
       11 . The common voltage generation circuit as defined in  claim 9 , 
 wherein the second operational amplifier includes a second differential section and a second driver section which are voltage-follower-connected, and    wherein the second driver section includes:    a current source which is connected with a second power supply voltage at one end and is connected with the output of the second operational amplifier at the other end; and    an n-channel driver transistor which is connected with the first power supply voltage at one end and is connected with the output of the second operational amplifier at the other end.    
   
   
       12 . The common voltage generation circuit as defined in  claim 10 , 
 wherein the second operational amplifier includes a second differential section and a second driver section which are voltage-follower-connected, and    wherein the second driver section includes:    a current source which is connected with a second power supply voltage at one end and is connected with the output of the second operational amplifier at the other end; and    an n-channel driver transistor which is connected with the first power supply voltage at one end and is connected with the output of the second operational amplifier at the other end.    
   
   
       13 . The common voltage generation circuit as defined in  claim 1 , 
 wherein the first operational amplifier is a voltage-follower-connected operational amplifier, output of the first operational amplifier being driven by a p-channel driver transistor.    
   
   
       14 . The common voltage generation circuit as defined in  claim 2 , 
 wherein the first operational amplifier is a voltage-follower-connected operational amplifier, output of the first operational amplifier being driven by a p-channel driver transistor.    
   
   
       15 . The common voltage generation circuit as defined in  claim 13 , 
 wherein the first operational amplifier includes a first differential section and a first driver section which are voltage-follower-connected, and    wherein the first driver section includes:    a p-channel driver transistor which is connected with a second power supply voltage at one end and is connected with the output of the first operational amplifier at the other end; and    a current source which is connected with the first power supply voltage at one end and is connected with the output of the first operational amplifier at the other end.    
   
   
       16 . The common voltage generation circuit as defined in  claim 14 , 
 wherein the first operational amplifier includes a first differential section and a first driver section which are voltage-follower-connected, and    wherein the first driver section includes:    a p-channel driver transistor which is connected with a second power supply voltage at one end and is connected with the output of the first operational amplifier at the other end; and    a current source which is connected with the first power supply voltage at one end and is connected with the output of the first operational amplifier at the other end.    
   
   
       17 . The common voltage generation circuit as defined in  claim 11 , 
 wherein the first operational amplifier is a voltage-follower-connected operational amplifier, output of the first operational amplifier being driven by a p-channel driver transistor.    
   
   
       18 . The common voltage generation circuit as defined in  claim 12 , 
 wherein the first operational amplifier is a voltage-follower-connected operational amplifier, output of the first operational amplifier being driven by a p-channel driver transistor.    
   
   
       19 . The common voltage generation circuit as defined in  claim 17 , 
 wherein the first operational amplifier includes a first differential section and a first driver section which are voltage-follower-connected, and    wherein the first driver section includes:    a p-channel driver transistor which is connected with the second power supply voltage at one end and is connected with the output of the first operational amplifier at the other end; and    a current source which is connected with the first power supply voltage at one end and is connected with the output of the first operational amplifier at the other end.    
   
   
       20 . The common voltage generation circuit as defined in  claim 18 , 
 wherein the first operational amplifier includes a first differential section and a first driver section which are voltage-follower-connected, and    wherein the first driver section includes:    a p-channel driver transistor which is connected with the second power supply voltage at one end and is connected with the output of the first operational amplifier at the other end; and    a current source which is connected with the first power supply voltage at one end and is connected with the output of the first operational amplifier at the other end.    
   
   
       21 . The common voltage generation circuit as defined in  claim 1 , comprising: 
 a first output transistor to which the high-potential-side voltage is supplied at one end; and    a second output transistor to which the low-potential-side voltage is supplied at one end,    wherein the other end of the first output transistor is connected with the other end of the second output transistor, and    wherein amplitude of gate voltages of the first and second output transistors is greater than a voltage difference between the high-potential-side voltage and the low-potential-side voltage.    
   
   
       22 . The common voltage generation circuit as defined in  claim 2 , comprising: 
 a first output transistor to which the high-potential-side voltage is supplied at one end; and    a second output transistor to which the low-potential-side voltage is supplied at one end,    wherein the other end of the first output transistor is connected with the other end of the second output transistor, and    wherein amplitude of gate voltages of the first and second output transistors is greater than a voltage difference between the high-potential-side voltage and the low-potential-side voltage.    
   
   
       23 . The common voltage generation circuit as defined in  claim 21 , 
 wherein the amplitude of the gate voltages of the first and second output transistors is the same as amplitude of a scan voltage applied to the scan line.    
   
   
       24 . The common voltage generation circuit as defined in  claim 22 , 
 wherein the amplitude of the gate voltages of the first and second output transistors is the same as amplitude of a scan voltage applied to the scan line.    
   
   
       25 . A power supply circuit which includes the common voltage generation circuit defined in  claim 1 .  
   
   
       26 . A power supply circuit which includes the common voltage generation circuit defined in  claim 2 .  
   
   
       27 . A power supply circuit for providing a power supply to an electro-optical device including a plurality of scan lines and a plurality of data lines, the power supply circuit comprising: 
 the common voltage generation circuit as defined in  claim 1;  and    a scan voltage generation circuit which generates a scan voltage of the scan line and supplies a high-potential-side voltage and a low-potential-side voltage of the scan voltage to the common voltage generation circuit.    
   
   
       28 . A power supply circuit for providing a power supply to an electro-optical device including a plurality of scan lines and a plurality of data lines, the power supply circuit comprising: 
 the common voltage generation circuit as defined in  claim 2;  and    a scan voltage generation circuit which generates a scan voltage of the scan line and supplies a high-potential-side voltage and a low-potential-side voltage of the scan voltage to the common voltage generation circuit.    
   
   
       29 . A display driver for driving an electro-optical device including a plurality of scan lines and a plurality of data lines, the display driver comprising: 
 the power supply circuit as defined in  claim 27;  and    a scan line driver circuit which drives the scan line by using the scan voltage.    
   
   
       30 . A display driver for driving an electro-optical device including a plurality of scan lines and a plurality of data lines, the display driver comprising: 
 the power supply circuit as defined in  claim 28;  and    a scan line driver circuit which drives the scan line by using the scan voltage.    
   
   
       31 . The display driver as defined in  claim 29 , comprising: a data line driver circuit which drives the data line based on display data.  
   
   
       32 . The display driver as defined in  claim 30 , comprising: a data line driver circuit which drives the data line based on display data.  
   
   
       33 . A display driver for driving an electro-optical device including a plurality of scan lines and a plurality of data lines, the display driver comprising: 
 the power supply circuit as defined in  claim 25;  and    a data line driver circuit which drives the data line based on display data.    
   
   
       34 . A display driver for driving an electro-optical device including a plurality of scan lines and a plurality of data lines, the display driver comprising: 
 the power supply circuit as defined in  claim 26;  and    a data line driver circuit which drives the data line based on display data.    
   
   
       35 . A display device, comprising the common voltage generation circuit as defined in  claim 1 , and performing a liquid crystal display by using the common voltage generated by the common voltage generation circuit.  
   
   
       36 . A display device, comprising the common voltage generation circuit as defined in  claim 2 , and performing a liquid crystal display by using the common voltage generated by the common voltage generation circuit.  
   
   
       37 . A common voltage generation method for generating a common voltage applied to a common electrode which faces a pixel electrode specified by a scan line and a data line of an electro-optical device through an electro-optical substance, the common voltage generation method comprising: 
 outputting an amplitude voltage of the common voltage based on a first power supply voltage by using a p-channel driver transistor of a voltage-follower-connected first operational amplifier, and generating a high-potential-side voltage of the common voltage based on the first power supply voltage by using an n-channel driver transistor of a voltage-follower-connected second operational amplifier;    generating a low-potential-side voltage of the common voltage by a charge-pump operation by using a flying capacitor connected between output of the first operational amplifier and the first power supply voltage, the low-potential-side voltage being lower in potential than the high-potential-side voltage for the amplitude voltage; and    supplying the high-potential-side voltage or the low-potential-side voltage to the common electrode.