JP2007212714A - Display panel built in with power source circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the performance of a built-in power source circuit while suppressing an increase in external terminals. <P>SOLUTION: The power source circuit 11 built in a liquid crystal panel 10 includes a first switch 12 for changing over the continuity between a voltage input point and a node P and a second switch 13 for changing over the continuity between a voltage output point and the node P. Control signals RCK1, RCK2 for controlling these switches are supplied separately through the external terminals. The transition from the state in which one of the two switches is conducting to the state in which the other is conducting by way of the state in which both are non-conducting is caused and a voltage changeover signal X is changed while the two switches are non-conducting. The two control signals RCK1, RCK2 and the voltage changeover signal X may be generated in a control signal generation circuit built into the liquid crystal panel and an external condenser may be built into the power source circuit of the liquid crystal panel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display panel such as a liquid crystal panel, and more particularly to a display panel incorporating a power supply circuit.

  When driving a display panel such as a liquid crystal panel, a power supply circuit is used to generate a voltage necessary for driving a pixel. For example, a charge pump type power supply circuit shown in FIG. 14 is used for the power supply circuit of the display panel. In order to increase or decrease the input voltage Vi by using this power supply circuit to obtain the output voltage Vo, the switch control circuit 90 is used to control the conduction state of the first and second switches 91 and 92, and the voltage It is necessary to control the voltage of one electrode of the capacitor 93 using the switching signal X.

  For example, in the initial state, it is assumed that the first and second switches 91 and 92 are in an off state, the voltage level of the voltage switching signal X is V1, and no charge is accumulated in the capacitor 93. In this initial state, first, the first switch 91 is controlled to be on for a predetermined time, and then the voltage level of the voltage switching signal X is changed from V1 to V2. Next, the second switch 92 is controlled to be in an on state for a predetermined time, and then the voltage level of the voltage switching signal X is changed from V2 to V1. Thereafter, this control is repeated.

  While the first switch 91 is in the ON state, a charge flows from the voltage input point via the first switch 91, and this charge is accumulated in the capacitor 93. On the other hand, while the second switch 92 is in the ON state, the electric charge accumulated in the capacitor 93 flows out from the voltage output point via the second switch 92.

  When a sufficient amount of electric charge is accumulated in the capacitor 93, the voltage between the electrodes of the capacitor 93 is (Vi−V1). Further, since the voltage between the electrodes of the capacitor 93 does not change even if the voltage level of the voltage switching signal X changes, the voltage at the node P after the voltage level of the voltage switching signal X changes to V2 is (Vi−V1 + V2). Become. Therefore, the output voltage Vo is (Vi−V1 + V2). In this manner, by charging the capacitor 93 and changing the voltage of one electrode of the capacitor 93 from V1 to V2, the input voltage Vi can be boosted or lowered to obtain the output voltage Vo.

As for charge pump type power supply circuits, conventionally, a technique in which a switch is configured by a MOS transistor is known (for example, Patent Documents 1 and 2).
JP-A-5-62477 JP 11-299227 A

  In many conventional display devices, the power supply circuit is built in a control IC provided outside the display panel. However, in recent display devices (particularly, recent liquid crystal display devices), the number of cases in which a power supply circuit is built in a display panel is increasing in order to reduce power consumption. When the power supply circuit is built in the display panel, it is necessary to supply the control signal of the power supply circuit from the outside of the display panel, and the power supply circuit built in the display panel also requires high boosting capability or step-down capability. Is done.

  However, a conventional display panel with a built-in power supply circuit cannot supply a suitable control signal to the power supply circuit, so that there is a problem that the boosting capability (or step-down capability) of the power supply circuit is reduced. In addition, it is necessary to provide an external terminal for inputting a control signal of the power supply circuit in the display panel incorporating the power supply circuit. However, if the external terminal is provided, there is a problem that the risk of electrostatic breakdown increases.

  Therefore, an object of the present invention is to improve the performance of a power supply circuit built in a display panel, and in particular, to improve the performance of a power supply circuit built in a display panel while suppressing an increase in external terminals. .

A first invention is a display panel incorporating a power supply circuit,
A plurality of pixels;
A drive circuit for driving the pixels;
A power supply circuit that generates a voltage necessary for driving the pixel and supplies the voltage to the drive circuit;
The power supply circuit is
A first switch for switching a conduction state between a voltage input point and an intermediate node configured to be able to control a voltage from outside the panel, based on a first switch control signal;
A second switch for switching a conduction state between a voltage output point and the intermediate node based on a second switch control signal;
The first and second switch control signals are separately supplied via different external terminals.

According to a second invention, in the first invention,
The power supply circuit further includes a level shift circuit that converts a voltage level of the first and second switch control signals supplied via an external terminal into an input voltage level or an output voltage level.

According to a third invention, in the first invention,
At least one of the first and second switch control signals is a control signal for the drive circuit.

According to a fourth invention, in the first invention,
The intermediate node is connected to an external terminal.

According to a fifth invention, in the first invention,
The power supply circuit further includes a capacitor having one electrode connected to an external terminal, and the intermediate node is connected to the other electrode of the capacitor.

A sixth invention is a display device,
A display panel of the first invention;
A display control circuit for outputting the first and second switch control signals and a voltage switching signal for controlling the voltage of the intermediate node;
The first and second switch control signals cause the first and second switches to transition from a state where one is conductive to a state where both are non-conductive and the other is conductive. The voltage switching signal changes while both the first and second switches are non-conductive.

A seventh invention is a display panel incorporating a power supply circuit,
A plurality of pixels;
A drive circuit for driving the pixels;
A power supply circuit that generates a voltage necessary for driving the pixel and supplies the voltage to the drive circuit;
The power supply circuit is
A control signal generation circuit for generating first and second switch control signals and a voltage switching signal based on a clock signal supplied via an external terminal;
A first switch that switches a conduction state between a voltage input point and an intermediate node configured to be able to control a voltage based on the voltage switching signal based on the first switch control signal;
And a second switch for switching a conduction state between the voltage output point and the intermediate node based on the second switch control signal.

In an eighth aspect based on the seventh aspect,
The first and second switch control signals cause the first and second switches to transition from a state where one is conductive to a state where both are non-conductive and the other is conductive. The voltage switching signal changes while both the first and second switches are non-conductive.

In a ninth aspect based on the eighth aspect,
The control signal generation circuit includes a delay circuit that delays the clock signal, and based on the clock signal and an output signal of the delay circuit, the first and second switch control signals, and the voltage switching signal. It is characterized by generating.

In a tenth aspect based on the eighth aspect,
The control signal generation circuit includes a frequency dividing circuit that divides the clock signal, and based on the clock signal and the output signal of the frequency dividing circuit, the first and second switch control signals, and the voltage A switching signal is generated.

In an eleventh aspect based on the seventh aspect,
The power supply circuit further includes a level shift circuit that converts a voltage level of the first and second switch control signals generated by the control signal generation circuit into an input voltage level or an output voltage level.

In a twelfth aspect based on the seventh aspect,
The clock signal is a control signal for the driving circuit.

In a thirteenth aspect based on the seventh aspect,
At least one of the first and second switch control signals is used as a control signal for the drive circuit.

In a seventeenth aspect based on the seventh aspect,
The voltage switching signal is output to the outside of the panel via an external terminal, and the intermediate node is connected to another external terminal.

In a fifteenth aspect based on the seventh aspect,
The power supply circuit further includes a capacitor to which the voltage switching signal is supplied to one electrode, and the intermediate node is connected to the other electrode of the capacitor.

  According to the first invention, when the two switches are controlled using the two switch control signals and the voltage at the intermediate node is controlled from the outside of the panel using the voltage switching signal, The voltage switching signal can be changed at any timing. Therefore, a switch control signal that causes two switches to transition from a state in which one switch is conductive to a state in which both switches are nonconductive and the other switch is in a conductive state, and the two switches are both nonconductive. By supplying a voltage switching signal that changes while the external capacitor or the built-in capacitor is charged and discharged, the capability of the power supply circuit built in the display panel can be improved.

  According to the second aspect, by suppressing the voltage amplitude of the switch control signal, the withstand voltage requirement of the control IC for the display panel can be lowered.

  According to the third aspect, by using the control signal for the drive circuit as the switch control signal, the number of external terminals for inputting the switch control signal can be reduced.

  According to the fourth aspect of the present invention, one electrode of the external capacitor is connected to the external terminal connected to the intermediate node, and a voltage switching signal is supplied to the other electrode of the external capacitor. The voltage can be controlled from outside the panel.

  According to the fifth aspect, the voltage at the intermediate node can be controlled from outside the panel by supplying the voltage switching signal to the external terminal connected to the capacitor. In addition, by incorporating a capacitor, external parts of the display panel can be reduced and external terminals can be reduced.

  According to the sixth aspect of the invention, the switch control causes the display control circuit to transition the two switches from a state in which one of the two switches is conductive to a state in which the other is conductive through a state in which both are non-conductive. A signal and a voltage switching signal that changes while both switches are non-conductive are generated. By supplying these signals to the display panel, the external capacitor or the built-in capacitor can be reliably charged and discharged, and the capability of the power supply circuit built in the display panel can be improved.

  According to the seventh aspect, the control signal generation circuit can generate signals suitable for controlling the power supply circuit as the first and second switch control signals and the voltage switching signal. Therefore, by using these signals, the external capacitor or the built-in capacitor can be reliably charged and discharged, and the capability of the power supply circuit built in the display panel can be improved. In addition, by generating the switch control signal within the panel, the timing at which the switch control signal changes can be controlled with high accuracy.

  According to the eighth aspect of the invention, the control signal generating circuit causes the two switches to transition from a state where one is conductive to a state where both are non-conductive and the other is conductive. A control signal and a voltage switching signal that changes while both switches are non-conductive are generated. By using these signals, the external capacitor or the built-in capacitor can be reliably charged and discharged, and the capability of the power supply circuit built in the display panel can be improved.

  According to the ninth aspect, the timing at which the first and second switch control signals change and the timing at which the voltage switching signal change can be made different based on the delay time in the delay circuit.

  According to the tenth aspect, the timing at which the first and second switch control signals change and the timing at which the voltage switching signal change can be made different by an integral multiple of a half period of the clock signal.

  According to the eleventh aspect of the invention, the voltage amplitude requirement of the control IC for the display panel can be reduced by suppressing the voltage amplitude of the switch control signal and the voltage amplitude of the clock signal supplied to the display panel.

  According to the twelfth aspect, by using the control signal for the drive circuit as the clock signal, the external terminals for inputting the clock signal can be reduced.

  According to the thirteenth aspect, by using the switch control signal generated in the panel as a control signal for the drive circuit, external terminals for inputting the control signal for the drive circuit can be reduced.

  According to the fourteenth aspect, one electrode of the external capacitor is connected to the external terminal connected to the intermediate node, and the voltage switching signal generated by the control signal generation circuit is supplied to the other electrode of the external capacitor. Thus, the voltage at the intermediate node can be controlled based on the voltage switching signal.

  According to the fifteenth aspect, the voltage at the intermediate node can be controlled based on the voltage switching signal. In addition, by incorporating a capacitor, external parts of the display panel can be reduced and external terminals can be reduced.

  Hereinafter, liquid crystal panels according to first to seventh embodiments of the present invention will be described with reference to the drawings. Each of the liquid crystal panels according to each embodiment has a built-in power supply circuit and is characterized by the configuration of the power supply circuit. Therefore, in the following, the power supply circuit of the liquid crystal panel according to each embodiment will be mainly described. In addition, about the component demonstrated in previous embodiment among the components of each embodiment, the same referential mark is attached | subjected and description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a liquid crystal panel according to the first embodiment of the present invention. A liquid crystal panel 10 shown in FIG. 1 includes a pixel array 1, a drive circuit 2, and a power supply circuit 11. A capacitor 18 and a display control circuit 19 are provided outside the liquid crystal panel 10. The display control circuit 19 outputs first and second switch control signals RCK1 and RCK2 and a voltage switching signal X in order to control the power supply circuit 11 built in the liquid crystal panel 10. These three control signals are separately supplied to the liquid crystal panel 10 via different external terminals.

  The pixel array 1 includes a plurality of pixels (not shown) arranged two-dimensionally. The drive circuit 2 drives the pixels included in the pixel array 1 based on the display control signal CNTL output from the display control circuit 19. A voltage necessary for driving the pixel is supplied from the power supply circuit 11. The power supply circuit 11 boosts or steps down the input voltage Vi and supplies the obtained output voltage Vo to the drive circuit 2.

  The power supply circuit 11 includes a first switch 12 and a second switch 13. The first and second switches 12 and 13 are composed of MOS transistors. In the example shown in FIG. 1, the first switch 12 is composed of an N channel MOS transistor, and the second switch 13 is composed of a P channel MOS transistor. The first switch 12 may be a P-channel MOS transistor and the second switch 13 may be an N-channel MOS transistor, or the first and second switches 12 and 13 may be the same conduction type MOS transistor. It may be configured.

  Each of the first and second switches 12 and 13 has two conduction terminals and one control terminal. The first and second switches 12 and 13 are connected in series. More specifically, one conduction terminal of the first switch 12 and one conduction terminal of the second switch 13 are connected to the node P. An input voltage Vi supplied from the outside of the liquid crystal panel 10 is applied to the other conduction terminal of the first switch 12. An output voltage Vo supplied to the drive circuit 2 is output from the other conduction terminal of the second switch 13.

  The first switch control signal RCK1 is supplied to the control terminal of the first switch 12 via an external terminal. The first switch 12 controls the conduction state between the voltage input point to which the input voltage Vi is applied and the node P based on the first switch control signal RCK1. The first switch 12 is in an on state when the first switch control signal RCK1 is at a high level, and is in an off state when it is at a low level.

  The control terminal of the second switch 13 is supplied with the second switch control signal RCK2 supplied via the external terminal. The second switch 13 controls the conduction state between the voltage output point where the output voltage Vo is output and the node P based on the second switch control signal RCK2. The second switch 13 is turned off when the second switch control signal RCK2 is at a high level, and turned on when it is at a low level.

  The node P is connected to an external terminal of the liquid crystal panel 10. One electrode of the capacitor 18 is connected to the external terminal, and the voltage switching signal X output from the display control circuit 19 is supplied to the other electrode of the capacitor 18.

  FIG. 2 is a signal waveform diagram of the control signal of the power supply circuit 11. Hereinafter, a signal change from time t1 to time t2 will be described. At time t1, the first switch control signal RCK1 is at a low level, the second switch control signal RCK2 is at a high level, and the voltage level of the voltage switching signal X is V1. Therefore, at time t1, the first and second switches 12 and 13 are turned off.

  After time t1, first switch control signal RCK1 changes to high level. As a result, the first switch 12 is turned on, and electric charge flows from the voltage input point via the first switch 12, and this electric charge is accumulated in the capacitor 18 externally attached to the liquid crystal panel 10. After a predetermined time has elapsed, the first switch control signal RCK1 changes to a low level, and accordingly, the first switch 12 is turned off. When a sufficient amount of charge is accumulated in the capacitor 18, the voltage between the electrodes of the capacitor 18 is (Vi-V1), and the voltage at the node P is Vi.

  Next, the voltage level of the voltage switching signal X changes from V1 to V2. As a result, the voltage at the node P changes from Vi to (Vi−V1 + V2).

  Next, the second switch control signal RCK2 changes to a low level. As a result, the second switch 13 is turned on, and the charge accumulated in the capacitor 18 flows out from the voltage output point via the second switch 13. The output voltage Vo at this time is the voltage at the node P, that is, (Vi−V1 + V2). After a predetermined time has elapsed, the second switch control signal RCK2 changes to a low level, and accordingly, the second switch 13 is turned off. When all the charges accumulated in the capacitor 18 are released, the voltage between the electrodes of the capacitor 18 becomes 0 and the voltage at the node P becomes V2.

  Next, the voltage level of the voltage switching signal X changes from V2 to V1. Accordingly, the voltage at the node P changes from V2 to V1.

  Thus, by supplying three control signals that change at the timing shown in FIG. 2 to the power supply circuit 11, the input voltage Vi can be boosted or stepped down to obtain the output voltage Vo. In addition, the first and second switch control signals RCK1 and RCK2 shown in FIG. 2 pass from a state where one of the first and second switches 12 and 13 is conductive to a state where both are non-conductive, The voltage switching signal X shown in FIG. 2 is changed while both the first and second switches 12 and 13 are non-conductive. Thus, before and after the voltage switching signal X changes (only time T in FIG. 2), the charging and discharging of the capacitor 18 is performed by providing a state in which both the first and second switches 12 and 13 are non-conductive. Thus, the step-up capability or step-down capability of the power supply circuit 11 can be improved.

  As described above, according to the liquid crystal panel according to the present embodiment, one electrode of the external capacitor is connected to the external terminal connected to the intermediate node, and a voltage switching signal is supplied to the other electrode of the external capacitor. By doing so, the voltage of the intermediate node can be controlled from outside the panel. Moreover, when controlling two switches using two switch control signals and controlling the voltage of the node P from the outside of the panel using the voltage switching signal, the switch control signal and the voltage switching signal can be freely set. It can be changed at the timing. Therefore, a switch control signal that causes two switches to transition from a state in which one switch is conductive to a state in which both switches are nonconductive and the other switch is in a conductive state, and the two switches are both nonconductive. By supplying a voltage switching signal that changes while the external capacitor is being charged, it is possible to reliably charge and discharge the external capacitor and improve the capability of the power supply circuit built in the display panel.

(Second Embodiment)
FIG. 3 is a diagram showing a configuration of a liquid crystal panel according to the second embodiment of the present invention. A liquid crystal panel 20 shown in FIG. 3 is obtained by replacing the power supply circuit 11 with a power supply circuit 21 in the liquid crystal panel 10 according to the first embodiment. The power supply circuit 21 is obtained by adding level shifters 22 and 23 to the power supply circuit 11. As in the first embodiment, a capacitor 18 and a display control circuit 19 are provided outside the liquid crystal panel 20.

  The level shifter 22 is provided between the external terminal and the control terminal of the first switch 12, and the voltage level of the first switch control signal RCK1 supplied via the external terminal is set to the level of the input voltage Vi or the output voltage Vo. Convert to The level shifter 23 is provided between the external terminal and the control terminal of the second switch 13, and changes the voltage level of the second switch control signal RCK2 supplied via the external terminal to the level of the input voltage Vi or the output voltage Vo. Convert to

  More specifically, when the power supply circuit 11 performs boosting (that is, when Vi <Vo), the voltage level of the output signal of the level shifter 22 is Vi, when the first switch control signal RCK1 is at low level, When it is high level, it becomes Vo. Conversely, when the power supply circuit 11 performs step-down (that is, when Vi> Vo), the voltage level of the output signal of the level shifter 22 is Vo, when the first switch control signal RCK1 is at low level. When it is high level, it becomes Vi. The voltage level of the output signal of the level shifter 23 is the same as this.

  Therefore, according to the liquid crystal panel according to the present embodiment, in addition to the effect of the liquid crystal panel according to the first embodiment, the voltage amplitude of the switch control signal output from the display control circuit is suppressed, and the display panel control IC withstand voltage requirements can be lowered.

(Third embodiment)
FIG. 4 is a diagram showing a configuration of a liquid crystal panel according to the third embodiment of the present invention. A liquid crystal panel 30 shown in FIG. 4 is obtained by replacing the power supply circuit 21 with a power supply circuit 31 in the liquid crystal panel 20 according to the second embodiment. The power supply circuit 31 is obtained by adding a control signal generation circuit 32 to the power supply circuit 21. A capacitor 18 and a display control circuit 39 are provided outside the liquid crystal panel 30. The display control circuit 39 outputs a clock signal CK in order to control the power supply circuit 31 built in the liquid crystal panel 30. The clock signal CK is supplied to the liquid crystal panel 30 via an external terminal.

  The control signal generation circuit 32 generates the first and second switch control signals RCK1 and RCK2 and the voltage switching signal X based on the clock signal CK supplied via the external terminal. More specifically, the control signal generation circuit 32 includes delay circuits 33 and 34, a NOR gate 35, and a NAND gate 36. The delay circuit 33 delays the clock signal CK supplied via the external terminal by a predetermined time T. The delay circuit 34 further delays the output signal of the delay circuit 33 by a predetermined time T. The NOR gate 35 outputs the negation of the logical sum of the clock signal CK and the output signal of the delay circuit 34. The NAND gate 36 outputs the negation of the logical product of the clock signal CK and the output signal of the delay circuit 34. The control signal generation circuit 32 outputs the output signals of the delay circuit 33, the NOR gate 35, and the NAND gate 36 as the voltage switching signal X, the first switch control signal RCK1, and the second switch control signal RCK2, respectively.

  The voltage switching signal X is output to the outside of the liquid crystal panel 30 via an external terminal, and this external terminal is connected to one electrode of the capacitor 18. The node P to which the first and second switches 12 and 13 are connected is connected to another external terminal of the liquid crystal panel 30. The other electrode of the capacitor 18 is connected to this external terminal. As a result, the voltage at the node P is controlled based on the voltage switching signal X generated by the control signal generation circuit 32.

  FIG. 5 is a signal waveform diagram of the control signal of the power supply circuit 31. As shown in FIG. 5, the voltage switching signal X changes with a time T behind the clock signal CK, and the output signal of the delay circuit 34 changes with a time 2T behind the clock signal CK. The first switch control signal RCK1 is at a high level during the period from when the output signal of the delay circuit 34 falls to when the clock signal CK rises, and at a low level otherwise. The second switch control signal RCK2 is at a low level from when the output signal of the delay circuit 34 rises to when the clock signal CK falls, and at other times it is at a high level. As a result, both the first and second switches 12 and 13 are turned off for a time T before and after the voltage switching signal X changes.

  As described above, the first and second switch control signals RCK1 and RCK2 are turned on from the state where one of the first and second switches 12 and 13 is turned on to the state where both are turned off. The voltage switching signal X changes while both the first and second switches 12 and 13 are non-conductive.

  As described above, according to the liquid crystal panel according to the present embodiment, one electrode of the external capacitor is connected to the external terminal connected to the intermediate node, and the control signal generation circuit is connected to the other electrode of the external capacitor. By supplying the generated voltage switching signal, the voltage of the intermediate node can be controlled based on the voltage switching signal. In addition, the control signal generation circuit makes a transition from a state in which one of the two switches is turned on to a state in which both are turned off and the other is turned on. A voltage switching signal is generated that changes while both switches are non-conductive. By using these signals, the external capacitor can be reliably charged and discharged, and the capability of the power supply circuit built in the display panel can be improved. In addition, by generating the switch control signal within the panel, the timing at which the switch control signal changes can be controlled with high accuracy.

  The control signal generation circuit includes a delay circuit that delays the clock signal, and generates the first and second switch control signals and the voltage switching signal based on the clock signal and the output signal of the delay circuit. Therefore, the timing at which the first and second switch control signals change can be made different from the timing at which the voltage switching signal changes based on the delay time in the delay circuit.

(Fourth embodiment)
FIG. 6 is a diagram showing a configuration of a liquid crystal panel according to the fourth embodiment of the present invention. A liquid crystal panel 40 shown in FIG. 6 is obtained by replacing the power supply circuit 31 with a power supply circuit 41 in the liquid crystal panel 30 according to the third embodiment. The power supply circuit 41 is obtained by replacing the control signal generation circuit 32 with a control signal generation circuit 42 in the power supply circuit 31. Similar to the third embodiment, the capacitor 18 and the display control circuit 39 are provided outside the liquid crystal panel 40.

  Similar to the control signal generation circuit 32, the control signal generation circuit 42 generates the first and second switch control signals RCK1, RCK2 and the voltage switching signal X based on the clock signal CK supplied via the external terminal. To do. More specifically, the control signal generation circuit 42 includes D flip-flops 43 and 44 and a plurality of logic gates (such as a NOR gate 45 and a NAND gate 46). A clock signal CK supplied via an external terminal is supplied to the clock input of the D flip-flop 43, and an output signal of the D flip-flop 43 is supplied to the clock input of the D flip-flop 44. Accordingly, the D flip-flops 43 and 44 function as a frequency dividing circuit that divides the clock signal CK. The logic gates included in the control signal generation circuit 42 are connected as shown in FIG. The control signal generation circuit 42 outputs the output signals of the D flip-flop 44, the NOR gate 45, and the NAND gate 46 as the voltage switching signal X, the first switch control signal RCK1, and the second switch control signal RCK2, respectively.

  FIG. 7 is a signal waveform diagram of the control signal of the power supply circuit 41. FIG. 7 also shows signal waveforms at points Q1 to Q3 shown in FIG. As shown in FIG. 7, the output signal of the D flip-flop 43 is a signal obtained by dividing the clock signal CK by 2, and the voltage switching signal X is a signal obtained by dividing the clock signal CK by 4. When the half cycle of the clock signal CK is T, the signal at the point Q3 changes earlier by the time T than the output signal of the D flip-flop 43. The first switch control signal RCK1 is at a high level from time T after the fall of the voltage switching signal X until time T before the rise of the voltage switching signal X, and is at low level otherwise. . The second switch control signal RCK2 is at a low level from time T after the rise of the voltage switching signal X until time T before the fall of the voltage switching signal X, and is at high level otherwise. .

  Thus, as in the third embodiment, the first and second switch control signals RCK1, RCK2 are both non-conductive from the state where one of the first and second switches 12, 13 is conductive. After the state is switched to the state where the other is conductive, the voltage switching signal X changes while both the first and second switches 12 and 13 are non-conductive.

  As described above, according to the liquid crystal panel according to the present embodiment, similarly to the liquid crystal panel according to the third embodiment, the external capacitor is reliably charged and discharged, and the power supply circuit built in the liquid crystal panel is In addition to improving the capability, the timing at which the switch control signal changes can be controlled with high accuracy.

  The control signal generation circuit includes a frequency dividing circuit that divides the clock signal, and generates the first and second switch control signals and the voltage switching signal based on the clock signal and the output signal of the frequency dividing circuit. To do. Therefore, the timing at which the first and second switch control signals change and the timing at which the voltage switching signal changes by an integral multiple of the half cycle of the clock signal (in the example shown in FIG. 6, only by the half cycle of the clock signal). Can be different.

  In the example shown in FIG. 6, the frequency division number of the clock signal CK is 2 and 4. However, the frequency division number of the clock signal CK may be a value other than this. The frequency division number of the clock signal CK is determined based on the cycle of the clock signal CK and the cycles of the first and second switch control signals RCK1 and RCK2, and in accordance with this, the detailed configuration of the control signal generation circuit is also provided. It is determined.

(Fifth embodiment)
FIG. 8 is a diagram showing a configuration of a liquid crystal panel according to the fifth embodiment of the present invention. A liquid crystal panel 50 shown in FIG. 8A includes a pixel array 1, a scanning signal line driving circuit 3, a data signal line driving circuit (not shown), and a power supply circuit 51. A capacitor 18 and a display control circuit 58 are provided outside the liquid crystal panel 50. The liquid crystal panel 52 shown in FIG. 8B includes a pixel array 1, a scanning signal line drive circuit (not shown), a data signal line drive circuit 4, and a power supply circuit 53. A capacitor 18 and a display control circuit 59 are provided outside the liquid crystal panel 52.

  Generally, the display control circuit outputs a drive control signal that periodically changes in order to control drive circuits (scanning signal line drive circuit and data signal line drive circuit) built in the liquid crystal panel. The drive control signal includes, for example, first and second gate clock signals GCK1 and GCK2, a source clock signal SCK, a gate output enable signal GOE, and the like. These drive control signals are separately supplied to the liquid crystal panel via external terminals. The liquid crystal panel according to the present embodiment uses the drive control signal as a switch control signal or a clock signal.

  In FIG. 8A, a power supply circuit 51 is the power supply circuit 11 according to the first embodiment, the power supply circuit 21 according to the second embodiment, or the like. The first gate clock signal GCK1 supplied to the liquid crystal panel 50 via the external terminal is supplied to the scanning signal line drive circuit 3 and is also supplied to the power supply circuit 51 as the first switch control signal RCK1. Similarly, the second gate clock signal GCK2 supplied to the liquid crystal panel 50 via the external terminal is supplied to the scanning signal line driving circuit 3 and also supplied to the power supply circuit 51 as the second switch control signal RCK2. . The node P in the power supply circuit 51 (the node to which the first and second switches 12 and 13 are connected) is connected to the external terminal of the liquid crystal panel 50. One electrode of the capacitor 18 is connected to the external terminal, and the voltage switching signal X output from the display control circuit 19 is supplied to the other electrode of the capacitor 18.

  In FIG. 8B, the power supply circuit 53 is the power supply circuit 31 according to the third embodiment, the power supply circuit 41 according to the fourth embodiment, or the like. The source clock signal SCK supplied to the liquid crystal panel 52 via an external terminal is supplied to the data signal line driving circuit 4 and also supplied to the power supply circuit 53 as the clock signal CK. The voltage switching signal X is output to the outside of the liquid crystal panel 52 via an external terminal, and this external terminal is connected to one electrode of the capacitor 18. The node P (the node P to which the first and second switches 12 and 13 are connected) is connected to another external terminal of the liquid crystal panel 52. The other electrode of the capacitor 18 is connected to this external terminal.

  As long as the power supply circuit correctly performs step-up or step-down, any of the drive control signals output from the display control circuits 58 and 59 for any of the power supply circuits 11, 21, 31, and 41 is used as a switch control signal or a clock. It may be supplied as a signal. For example, two drive control signals may be supplied to the power supply circuit 51 as two switch control signals (see FIG. 8A), or to control the drive control signal and the power supply circuit. May be supplied one by one.

  As described above, according to the liquid crystal panel according to the present embodiment, in addition to the effects of the liquid crystal panel according to each embodiment, the control signal for the drive circuit is used as the switch control signal or the clock signal, thereby enabling the switch control. External terminals for inputting a signal or a clock signal can be reduced.

(Sixth embodiment)
FIG. 9 is a diagram showing a configuration of a liquid crystal panel according to the sixth embodiment of the present invention. The liquid crystal panel 54 shown in FIG. 9A includes a pixel array 1, a scanning signal line driving circuit 3, a data signal line driving circuit (not shown), and a power supply circuit 55. The liquid crystal panel 56 shown in FIG. 9B includes a pixel array 1, a scanning signal line drive circuit (not shown), a data signal line drive circuit 4, and a power supply circuit 55. A capacitor 18 and a display control circuit 39 are provided outside the liquid crystal panels 54 and 56. The liquid crystal panel according to the present embodiment uses a clock control signal generated in the panel as a drive control signal.

  9A and 9B, the power supply circuit 55 is the power supply circuit 31 according to the third embodiment, the power supply circuit 41 according to the fourth embodiment, or the like. The power supply circuit 55 includes a control signal generation circuit 57 that generates first and second switch control signals RCK1 and RCK2 and a voltage switching signal X based on a clock signal CK supplied via an external terminal. The first and second switch control signals RCK1 and RCK2 are used to control the first and second switches included in the power supply circuit 55.

  The first and second switch control signals RCK1 and RCK2 are supplied to drive circuits (scanning signal line drive circuit and data signal line drive circuit) built in the liquid crystal panels 54 and 56, and are also used as drive control signals. Is done. In the liquid crystal panel 54 shown in FIG. 9A, the first and second switch control signals RCK1 and RCK2 are supplied to the scanning signal line drive circuit 3 and used as the first and second gate clock signals GCK1 and GCK2. Is done. In the liquid crystal panel 56 shown in FIG. 9B, only the second switch control signal RCK2 is supplied to the data signal line driving circuit 4 and used as the source clock signal SCK.

  As long as the drive circuit performs driving correctly, any of the first and second switch control signals RCK1 and RCK2 generated by the control signal generation circuit 57 may be used as any drive control signal. For example, both the first and second switch control signals RCK1 and RCK2 may be used as drive control signals (FIG. 9A), or only one of them may be used as a drive control signal (FIG. 9). 9 (b)).

  As described above, according to the liquid crystal panel according to the present embodiment, in addition to the effects of the liquid crystal panel according to each embodiment, the switch control signal generated in the panel is used as a control signal for the drive circuit. The number of external terminals for inputting a control signal to the drive circuit can be reduced.

(Seventh embodiment)
10 to 13 are diagrams showing the configuration of the liquid crystal panel according to the seventh embodiment of the present invention. As described above, the liquid crystal panels according to the first to sixth embodiments are used with the capacitor 18 externally attached. The liquid crystal panel according to the present embodiment is obtained by modifying the liquid crystal panel according to the first to sixth embodiments so that the power supply circuit includes a capacitor.

  A liquid crystal panel 60 shown in FIG. 10A is a modification of the liquid crystal panel 10 according to the first embodiment. A power supply circuit 61 included in the liquid crystal panel 60 is obtained by adding a capacitor 14 to the power supply circuit 11 according to the first embodiment. One electrode of the capacitor 14 is connected to the external terminal of the liquid crystal panel 60, and the other electrode is connected to the node P. The voltage switching signal X output from the display control circuit 19 is supplied to the external terminal to which the capacitor 14 is connected.

  A liquid crystal panel 62 shown in FIG. 10B is a modification of the liquid crystal panel 20 according to the second embodiment. The power supply circuit 63 included in the liquid crystal panel 62 is obtained by adding a capacitor 14 to the power supply circuit 21 according to the second embodiment. One electrode of the capacitor 14 is connected to the external terminal of the liquid crystal panel 62, and the other electrode is connected to the node P. The voltage switching signal X output from the display control circuit 19 is supplied to the external terminal to which the capacitor 14 is connected.

  A liquid crystal panel 64 shown in FIG. 11 is a modification of the liquid crystal panel 30 according to the third embodiment. A power circuit 65 included in the liquid crystal panel 64 is obtained by adding a capacitor 14 to the power circuit 31 according to the third embodiment. The voltage switching signal X generated by the control signal generation circuit 32 is supplied to one electrode of the capacitor 14, and the other electrode is connected to the node P. If the control signal generation circuit 32 is replaced with the control signal generation circuit 42 (FIG. 6) in the liquid crystal panel 64, a liquid crystal panel obtained by modifying the liquid crystal panel 40 according to the fourth embodiment is obtained.

  A liquid crystal panel 70 shown in FIG. 12A is a modification of the liquid crystal panel 50 (FIG. 8A) according to the fifth embodiment. The built-in capacitor type power supply circuit 71 included in the liquid crystal panel 70 is, for example, the power supply circuit 61 shown in FIG. 10A and the power supply circuit 63 shown in FIG. A liquid crystal panel 72 shown in FIG. 12B is a modification of the liquid crystal panel 52 (FIG. 8B) according to the fifth embodiment. The capacitor built-in power circuit 73 included in the liquid crystal panel 72 is the power circuit 65 shown in FIG.

  A liquid crystal panel 74 shown in FIG. 13A is a modification of the liquid crystal panel 54 (FIG. 9A) according to the sixth embodiment. A liquid crystal panel 76 shown in FIG. 13B is a modification of the liquid crystal panel 56 (FIG. 9B) according to the sixth embodiment. The capacitor built-in power circuit 75 included in the liquid crystal panels 74 and 76 is obtained by adding a capacitor to the power circuit 31 shown in FIG. 4 or the power circuit 41 shown in FIG.

  As described above, according to the liquid crystal panel according to the present embodiment, in addition to the effects of the liquid crystal panel according to each embodiment, by incorporating a capacitor in the power supply circuit, the external parts of the display panel are reduced, and the external Terminals can be reduced.

  Up to this point, a liquid crystal panel with a built-in power supply circuit has been described as an example of a display panel with a built-in power supply circuit. However, a display panel other than the liquid crystal panel (for example, an organic electroluminescence panel) is configured based on the same principle. You can also.

It is a figure which shows the structure of the liquid crystal panel which concerns on the 1st Embodiment of this invention. FIG. 2 is a signal waveform diagram of a control signal of a power supply circuit of the liquid crystal panel shown in FIG. 1. It is a figure which shows the structure of the liquid crystal panel which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the liquid crystal panel which concerns on the 3rd Embodiment of this invention. FIG. 6 is a signal waveform diagram of a control signal of a power supply circuit of the liquid crystal panel shown in FIG. 5. It is a figure which shows the structure of the liquid crystal panel which concerns on the 4th Embodiment of this invention. FIG. 8 is a signal waveform diagram of a control signal of a power supply circuit of the liquid crystal panel shown in FIG. 7. It is a figure which shows the structure of the liquid crystal panel which concerns on the 5th Embodiment of this invention. It is a figure which shows the structure of the liquid crystal panel which concerns on the 6th Embodiment of this invention. It is a figure which shows the structure of the liquid crystal panel which concerns on the 7th Embodiment of this invention. It is a figure which shows the other structure of the liquid crystal panel which concerns on the 7th Embodiment of this invention. It is a figure which shows the other structure of the liquid crystal panel which concerns on the 7th Embodiment of this invention. It is a figure which shows the other structure of the liquid crystal panel which concerns on the 7th Embodiment of this invention. It is a figure which shows the structure of a charge pump type power supply circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pixel array 2 ... Drive circuit 3 ... Scanning signal line drive circuit 4 ... Data signal line drive circuit 10, 20, 30, 40, 50, 52, 54, 56, 60, 62, 64, 70, 72, 74, 76 ... Liquid crystal panel 11, 21, 31, 41, 51, 53, 55, 61, 63, 65 ... Power supply circuit 12 ... First switch 13 ... Second switch 14, 18 ... Capacitor 19, 39, 58, 59 ... Display control circuit 22, 23 ... Level shifter 32, 42, 57 ... Control signal generation circuit 71, 73, 75 ... Built-in capacitor type power supply circuit

Claims (15)

A display panel with a built-in power circuit,
A plurality of pixels;
A drive circuit for driving the pixels;
A power supply circuit that generates a voltage necessary for driving the pixel and supplies the voltage to the drive circuit;
The power supply circuit is
A first switch for switching a conduction state between a voltage input point and an intermediate node configured to be able to control a voltage from outside the panel, based on a first switch control signal;
A second switch for switching a conduction state between a voltage output point and the intermediate node based on a second switch control signal;
The display panel according to claim 1, wherein the first and second switch control signals are separately supplied via different external terminals.   2. The power supply circuit according to claim 1, further comprising a level shift circuit that converts voltage levels of the first and second switch control signals supplied via an external terminal into an input voltage level or an output voltage level. Display panel.   The display panel according to claim 1, wherein at least one of the first and second switch control signals is a control signal for the drive circuit.   The display panel according to claim 1, wherein the intermediate node is connected to an external terminal.   The display panel according to claim 1, wherein the power circuit further includes a capacitor having one electrode connected to an external terminal, and the intermediate node is connected to the other electrode of the capacitor. . A display panel according to claim 1;
A display control circuit for outputting the first and second switch control signals and a voltage switching signal for controlling the voltage of the intermediate node;
The first and second switch control signals cause the first and second switches to transition from a state where one is conductive to a state where both are non-conductive and the other is conductive. The voltage switching signal changes while both the first and second switches are non-conductive. A display panel with a built-in power circuit,
A plurality of pixels;
A drive circuit for driving the pixels;
A power supply circuit that generates a voltage necessary for driving the pixel and supplies the voltage to the drive circuit;
The power supply circuit is
A control signal generation circuit for generating first and second switch control signals and a voltage switching signal based on a clock signal supplied via an external terminal;
A first switch that switches a conduction state between a voltage input point and an intermediate node configured to be able to control a voltage based on the voltage switching signal based on the first switch control signal;
A display panel comprising: a second switch that switches a conduction state between a voltage output point and the intermediate node based on the second switch control signal.   The first and second switch control signals cause the first and second switches to transition from a state where one is conductive to a state where both are non-conductive and the other is conductive. 8. The display panel according to claim 7, wherein the voltage switching signal changes while both the first and second switches are non-conductive.   The control signal generation circuit includes a delay circuit that delays the clock signal, and based on the clock signal and an output signal of the delay circuit, the first and second switch control signals, and the voltage switching signal. The display panel according to claim 8, wherein the display panel is generated.   The control signal generation circuit includes a frequency dividing circuit that divides the clock signal, and based on the clock signal and the output signal of the frequency dividing circuit, the first and second switch control signals, and the voltage The display panel according to claim 8, wherein the display panel generates a switching signal.   The power supply circuit further includes a level shift circuit that converts a voltage level of the first and second switch control signals generated by the control signal generation circuit into a level of an input voltage or an output voltage. Display panel as described.   The display panel according to claim 7, wherein the clock signal is a control signal for the driving circuit.   8. The display panel according to claim 7, wherein at least one of the first and second switch control signals is used as a control signal for the drive circuit.   The display panel according to claim 7, wherein the voltage switching signal is output to the outside of the panel via an external terminal, and the intermediate node is connected to another external terminal.   The said power supply circuit further includes the capacitor | condenser by which the said voltage switching signal is supplied to one electrode, The said intermediate node is connected to the other electrode of the said capacitor | condenser, Display panel.

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