JP2004229027A - Comparator, power supply circuit, integrated circuit, and flat display unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption as compared with prior art. <P>SOLUTION: A comparator has a switch circuit for interrupting the supply of a power supply VDD to a comparator body 47 by switching an operation according to a control signal by applying to the comparator. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a comparison circuit, a power supply circuit, an integrated circuit, and a flat display device, and can be applied to, for example, a flat display device in which a display unit and a drive circuit are integrally formed on an insulating substrate. According to the present invention, power is supplied only at the time of comparison, thereby reducing power consumption as compared with the related art.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a liquid crystal display device which is a flat display device applied to a portable terminal device such as a PDA and a mobile phone, a driving circuit of the liquid crystal display panel is integrated on a glass substrate which is an insulating substrate constituting the liquid crystal display panel. Are provided.
[0003]
In such a liquid crystal display device, a power supply circuit is formed using a charge-pump type DC-DC converter as disclosed in, for example, JP-A-2002-191168. To generate the necessary power.
[0004]
In this power supply circuit, a predetermined reference voltage is compared with the output voltage of the DC-DC converter by a comparison circuit, and the operation of the DC-DC converter is controlled based on the comparison result, so that the output voltage of the DC-DC converter is controlled to a predetermined value. It is designed to hold the voltage.
[0005]
[Patent Document 1]
JP 2002-191168 A
[Problems to be solved by the invention]
By the way, power consumption of a transistor formed on a glass substrate of this type tends to be higher than that of a transistor formed on a normal silicon substrate or the like. As a result, in the control of the DC-DC converter using such a comparison circuit, if the comparison result is obtained intermittently instead of the configuration that always obtains the comparison result, the power consumption can be reduced accordingly. It is considered possible. By the way, in this type of power supply circuit, even if the comparison result is obtained intermittently as described above, if the time interval related to the intermittent comparison result is set appropriately, the voltage fluctuation can be reduced to a practically sufficient range. Can be suppressed.
[0007]
That is, as shown in FIG. 8, switch circuits 4 to 6 are provided on the input line and the output line of the comparison circuit main body 3 constituting the comparison circuit 1, and the switch circuits 4 to 6 are turned on and off by the control signal SCC. A comparison circuit compares a potential VA of a power supply output from, for example, a DC-DC converter and a potential VB, which is a control target of the potential VA, only during a period in which the switch circuits 4 to 6 are held in an ON state. 1 and the result of the comparison can be latched and held by the subsequent latch 2. Thus, it is considered that the DC-DC converter can be controlled by the latch result of the latch 2 and the comparison circuit 1 can be operated intermittently to control the power supply voltage.
[0008]
However, when the comparison circuit 1 is intermittently operated in this way, even when the comparison circuit 1 is not comparing the potentials VA and VB, a small amount of current always flows from the node side by the power supply VDD to the node side by the power supply VSS. However, there is a problem that power is wasted unnecessarily.
[0009]
The present invention has been made in view of the above points, and it is an object of the present invention to propose a comparison circuit capable of reducing power consumption as compared with the related art, a power supply circuit using the comparison circuit, an integrated circuit, and a flat display device. Is what you do.
[0010]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 is provided with a switch circuit which is applied to a comparison circuit and switches the operation by a control signal to stop supplying power to the comparison circuit body.
[0011]
Further, in the invention of claim 2, applied to a power supply circuit, a DC-DC converter main body for generating a predetermined operation power supply from an input power supply, and a predetermined time interval between the operation power supply and a predetermined reference voltage. A control circuit for outputting a comparison result and controlling the DC-DC converter main body to stop or operate for a time interval based on the comparison result of the comparison circuit, thereby maintaining the operation power supply at a voltage determined by the reference voltage. A comparison circuit for outputting a comparison result between the operation power supply and the reference voltage, and a comparison circuit for outputting a comparison result between the operation power supply and the predetermined reference voltage at a predetermined time interval. And a switch circuit for supplying power to the comparison circuit body.
[0012]
Further, in the invention according to claim 3, the present invention is applied to an integrated circuit that switches the operation of each section based on the comparison result by the comparison circuit, and the comparison circuit compares the comparison result between the comparison target and the reference voltage at a fixed time interval. During the output period, a switch circuit for supplying power to the comparison circuit body is provided.
[0013]
Further, in the invention according to claim 4, applied to a flat display device, a power supply circuit operates by a predetermined drive pulse to generate an operation power supply from an input power supply, and a fixed time interval. A comparison circuit that outputs a comparison result between the operating power supply and a predetermined reference voltage, and stopping supply of a drive pulse to the DC-DC converter body for a time interval based on the comparison result of the comparison circuit. And a control circuit for holding the operating power supply at a voltage determined by the reference voltage.
[0014]
According to the configuration of the first aspect, a switch circuit that switches the operation by a control signal and stops the supply of power to the comparison circuit body is applied to the comparison circuit, so that the switch is switched only when the comparison result is required. Power can be supplied through a circuit to reduce power consumption.
[0015]
Thus, according to the configuration of claim 2, power consumption in the power supply circuit can be reduced as compared with the related art.
[0016]
Further, according to the configuration of the third aspect, the power consumption of the integrated circuit can be reduced as compared with the related art.
[0017]
Further, according to the configuration of the fourth aspect, the voltage of the operating power supply is monitored at regular time intervals and the operation of the DC-DC converter is stopped and controlled, so that the voltage of the operating power supply is constantly monitored. Thus, power consumption can be reduced.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
[0019]
(1) Configuration of Embodiment FIG. 2 is a block diagram showing an image display unit according to a mobile terminal device according to an embodiment of the present invention. The mobile terminal device is, for example, a mobile phone, a PDA, or the like, and displays a desired image on the image display unit 11. Therefore, in the image display unit 11, the image data D1 is stored in an image memory built in the image processing circuit 12, and the image data D1 is sequentially output to the liquid crystal display device 13. Further, in synchronization with the output of the image data D1, a master clock MCK, a vertical synchronization signal VSYNC, and a horizontal synchronization signal HSYNC are output.
[0020]
The portable terminal device inputs the image data D1, the master clock MCK, the vertical synchronization signal VSYNC, and the horizontal synchronization signal HSYNC to a built-in liquid crystal display device 13, and displays an image on the liquid crystal display device 13. Here, the liquid crystal display device 13 is a flat display device in which a display unit 14 having pixels arranged in a matrix and a drive circuit 15 for driving the pixels of the display unit 14 are integrally formed on a glass substrate. It is. In this embodiment, the pixels of the display section 14 are composed of a liquid crystal cell, a polysilicon TFT for switching the liquid crystal cell, and an auxiliary capacitor.
[0021]
On the other hand, the drive circuit 15 inputs the master clock MCK, the vertical synchronizing signal VSYNC, and the horizontal synchronizing signal HSYNC to the timing generator (TG) 17 via the interface (IF) 16, and outputs timing signals of various operation references here. Generate. The DC-DC converter (DDC) 21 operates according to a predetermined timing signal generated by the timing generator 17, and converts the power supply VDD supplied to the liquid crystal display device 13 to the power supplies VDD2, VVSS2, HVSS2 or the like is generated.
[0022]
Similarly, the vertical drive circuit 18 is operated by a predetermined timing signal generated by the timing generator 17, and outputs a selection signal for selecting a line of the display unit 14. The reference voltage generation circuit 19 generates a reference voltage necessary for the processing of the horizontal drive circuit 20, and the horizontal drive circuit 20 sets the gradation of the corresponding pixel of the display unit 14 by the gradation data based on the image data D1.
[0023]
FIG. 3 shows a configuration related to one power supply VDD2 of the DC-DC converter 21. FIG. Here, the converter unit 31 is a charge pump type DC-DC converter, which operates based on the pumping pulse PP and outputs a predetermined power supply VDD2. The comparison circuit 32 outputs a comparison result between the potential VA of the power supply VDD2 output from the converter unit 31 and a predetermined reference potential VB to the latch 33, and the latch 33 latches the comparison result and sends it to the AND circuit 34. Output. The AND circuit 34 turns on and off the operation of the converter 31 by gating the pumping pulse PP based on the latch result of the latch 33. Thus, the DC-DC converter 21 is configured to hold the output voltage VDD2 at a predetermined voltage by feedback control based on the comparison result of the comparison circuit 32.
[0024]
Here, as shown in FIG. 1, the comparison circuit 32 is configured so that input lines and output lines can be cut off by switch circuits 41, 42, and 43 that are operated by a control signal SCC, and is operated by a power supply control signal SC. The supply of the power supplies VDD and VSS to the comparison circuit main body 47 is stopped by the switch circuits 44 and 45.
[0025]
The comparison circuit 32 is set such that the signal levels of the power supply control signal SC and the control signal SCC are switched in conjunction with each other, whereby the switch circuits 41 to 43 are switched off to compare the potentials VA and VB. During the non-period, the switch circuits 44 and 45 are switched off so that no power is supplied, thereby further reducing power consumption.
[0026]
FIG. 4 is a time chart showing the power supply control signal SC and the control signal SCC. In this embodiment, the switch circuits 44 and 45 are turned on before the switch circuits 41 to 43 are turned on, and the switch circuits 44 and 45 are turned off after the switch circuits 41 to 43 are turned off. Is switched to the OFF state, whereby the potentials VA and VB can be reliably compared and the comparison result can be output.
[0027]
That is, when the power supply control signal SC rises at time t1, in the comparison circuit 32, the switch circuits 44 and 45 are turned on, and the supply of power to the comparison circuit main body 47 is started. Thereafter, when the comparison circuit main body 47 is enabled to operate stably, the control signal SCC rises at time t2, and the switch circuits 41 to 43 are turned on, and the comparison target body VA and the reference potential VB are input to the comparison circuit main body 47. As a result, a comparison result between the potentials VA and VB is obtained and latched by the latch 33. When the comparison result is latched by the latch 33, the control signal SCC falls at time t3, and the switch circuits 41 to 43 are turned off to supply the comparison object potential VA and the reference potential VB to the comparison circuit main body 47. Is stopped. Subsequently, at time t4, the power supply control signal SC falls, the switch circuits 44 and 45 are switched off, and the supply of power to the comparison circuit main body 47 is stopped.
[0028]
In the DC-DC converter 21 (FIG. 3), the comparison result by the comparison circuit 32 is latched by the latch 33 and input to the AND circuit 34. The AND circuit 34 gates the pumping pulse PP, and outputs the output of the converter unit 31. The voltage is maintained at a predetermined voltage.
[0029]
That is, as shown in FIG. 5, in the DC-DC converter 21, the converter section 31 operates by the pumping pulse PP to gradually increase the output voltage VDD2 (FIGS. 5A and 5B). In the DC-DC converter 21, the power supply control signal SC and the control signal SCC rise at regular time intervals, and a comparison result is obtained by the comparison circuit 32 (FIGS. 5C and 5D). The control signal SD of the converter unit 31 which is latched by the latch 33 and gates the AND circuit 34 rises (FIG. 5E). As a result, the operation of the DC-DC converter 21 is stopped, and the output voltage VDD2 gradually decreases. In addition, the control signal SD falls due to the rise of the power supply control signal SC and the control signal SCC after a certain time interval, whereby the converter section 31 starts operating and the output voltage VDD2 is prevented from lowering. As a result, in this embodiment, the power consumption can be reduced as compared with the case where the voltage of the operating power supply is monitored by always operating the comparison circuit.
[0030]
As shown in FIGS. 6 and 7, in the power supply control signal SC and the control signal SCC, a predetermined reference signal S1 is delayed by a delay circuit (D) 51 in a timing generator 17 to generate a delay reference signal S2. The OR circuit 52 and the AND circuit 53 process the reference signal S1 and the delay reference signal S2 to generate the signal.
[0031]
(2) Operation of the Embodiment In the configuration described above, in this portable terminal device (FIG. 2), image data D1 relating to an image acquired by accessing a homepage, and image data D1 acquired through an imaging unit are processed by image processing. The image data D1 held in an image memory built in the circuit 12 is input to the liquid crystal display device 13 together with a synchronization signal and the like. Further, the image data D1 is converted into a drive signal corresponding to the gradation of each pixel by the horizontal drive circuit 20 and output to the display unit 14, and by the selection of the line by the vertical drive circuit 18, the drive signal The image data D1 is supplied to the pixels, whereby an image based on the image data D1 is displayed on the display unit 14.
[0032]
In displaying an image based on the image data D1 in this manner, an operation power supply VDD2 and the like necessary for the operation of the drive circuit are generated from the input power supply VDD by the DC-DC converter 21 which is a power supply circuit. That is, in the DC-DC converter 21 (FIG. 3), the converter section 31 operates by the pumping pulse PP to generate the operation power supply VDD2 from the input power supply VDD, and at regular time intervals, the voltage VA of the operation power supply VDD2. And a predetermined reference voltage VB are compared by the comparison circuit 32 and held in the latch 33. In the DC-DC converter 21, when the voltage of the operating power supply VDD <b> 2 is high based on the comparison result, the pumping pulse PP is gated based on the latch result to stop the supply of the pumping pulse PP to the converter unit 31. As a result, an increase in the voltage of the operation power supply VDD2 is prevented. On the contrary, when the voltage of the operation power supply VDD2 is low, the pumping pulse PP is supplied to the converter unit 31 by the gate of the pumping pulse PP based on the latch result, and the converter unit 31 operates. Voltage drop of the power supply VDD2 is prevented.
[0033]
Thus, in this embodiment, the power consumption can be reduced as compared with the case where the voltage of the operating power supply is constantly monitored by the comparison circuit.
[0034]
Further, in the comparison circuit 32 that intermittently outputs the comparison result in this way (FIG. 4), the time is set so that the comparison result can be obtained sufficiently stably and reliably only when the comparison result is obtained and output. Power is supplied to the comparison circuit main body 47 by the switch circuits 44 and 45 with sufficient margin. As a result, in the comparison circuit 32, power consumption can be reduced as compared with the related art.
[0035]
(3) Effects of the Embodiment According to the above configuration, power is supplied only at the time of comparison, so that power consumption can be reduced as compared with the related art.
[0036]
Further, in a configuration using such a comparison circuit, by obtaining a comparison result at a fixed time interval and controlling the power supply, power consumption can be reduced as compared with the related art.
[0037]
(4) Other Embodiments In the above-described embodiment, the case where the present invention is applied to a power supply circuit using a charge pump type DC-DC converter has been described. However, the present invention is not limited to this. It can be widely applied to a power supply circuit and the like using a DC-DC converter of a system.
[0038]
Further, in the above-described embodiment, the case where the present invention is applied to the control of the power supply circuit has been described. Can be applied.
[0039]
Further, in the above-described embodiment, a case where a pixel is driven by a liquid crystal cell has been described. However, the present invention is not limited to this, and can be widely applied to a flat display device including a pixel with various display means.
[0040]
【The invention's effect】
As described above, according to the present invention, power is supplied to the entire comparison circuit only at the time of comparison, so that power consumption can be reduced as compared with the related art.
[Brief description of the drawings]
FIG. 1 is a connection diagram showing a comparison circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a portable terminal device using the comparison circuit of FIG. 1;
3 is a connection diagram showing a DC-DC converter in the portable terminal device of FIG.
FIG. 4 is a time chart for explaining the operation of the comparison circuit of FIG. 1;
FIG. 5 is a time chart for explaining the operation of the DC-DC converter of FIG. 3;
FIG. 6 is a block diagram illustrating a configuration of a timing generator for generating a control signal for controlling the operation of the comparison circuit of FIG. 1;
FIG. 7 is a time chart for explaining the operation of the timing generator of FIG. 6;
FIG. 8 is a connection diagram illustrating a comparison circuit in which a switch circuit is provided on an input / output line.
[Explanation of symbols]
1, 32 comparison circuit, 2, 33 latch, 3, 47 comparison circuit body, 4-6, 41-45 switch circuit, 21 DC-DC converter, 31 converter unit, 34, 53 ... AND circuit

Claims (5)

A comparison circuit that outputs a comparison result of the input signal;
A switch circuit for switching operation by a control signal and stopping supply of power to the comparison circuit main body. A DC-DC converter body for generating a predetermined operation power supply from an input power supply,
At a constant time interval, a comparison circuit that outputs a comparison result between the operation power supply and a predetermined reference voltage,
A control circuit that stops or operates the DC-DC converter body during the time interval based on a comparison result of the comparison circuit, thereby holding the operation power supply at a voltage determined by the reference voltage. ,
The comparison circuit includes:
A comparison circuit main body that outputs a comparison result between the operation power supply and the reference voltage,
A power supply circuit, comprising: a switch circuit for supplying power to the comparison circuit main body during a predetermined period of outputting a comparison result between the operation power supply and a predetermined reference voltage at the predetermined time interval. In an integrated circuit that switches the operation of each unit based on the comparison result by the comparison circuit,
The comparison circuit includes:
A comparison circuit main body that outputs a comparison result between the comparison target and the reference voltage,
An integrated circuit, comprising: a switch circuit that supplies power to the comparison circuit main body during a predetermined period during which a comparison result between the comparison target and a reference voltage is output. In a flat display device in which a display portion in which pixels are arranged in a matrix and a driving circuit for driving the pixels in the display portion are formed integrally on a substrate,
A predetermined power supply circuit generates an operation power supply required for operation of the drive circuit from an input power supply,
The power supply circuit,
A DC-DC converter main body that operates by a predetermined drive pulse and generates the operation power supply from the input power supply;
At a constant time interval, a comparison circuit that outputs a comparison result between the operation power supply and a predetermined reference voltage,
Control for maintaining the operating power supply at a voltage determined by the reference voltage by stopping supply of the drive pulse to the DC-DC converter body during the time interval based on a comparison result of the comparison circuit. A flat display device comprising a circuit. The comparison circuit includes:
A comparison circuit main body that outputs a comparison result between the operation power supply and the reference voltage,
A switch circuit that supplies power for operation to the main body of the comparison circuit during a predetermined time interval for outputting a result of comparison between the power supply for operation and a predetermined reference voltage at the constant time interval. The flat display device according to claim 4.

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