JP2001215931A - Temperature compensating circuit for liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature compensating circuit for liquid crystal display elements capable of generating an optimum driving voltage supplied to the liquid crystal display elements in accordance with a temperature change and capable of being incorporated in an integrated circuit. SOLUTION: This temperature compensating circuit is provided with a power source circuit for temperature detection 10 consisting of analog switches 7 to be operated based on the control of an up-down counter 8 and a resistance dividing circuit for voltage adjustment 6 for adjusting an output voltage based on inputs from the switches 7 and, moreover, the circuit is provided with a temperature detecting circuit 5 consiting of a diode 2 and a resistance dividing circuit 3. Furthermore, the circuit is provided with a liquid crystal characteristic correcting circuit 11 for converting the temperature change into a count number by the up-down counter 8 which is operated by being linked with a temperature detection output from the circuit 5 and for generating an optimum driving voltage to the liquid crystal display elements by inputting the converted value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating circuit for a liquid crystal display device, and more particularly, to generating an optimum driving voltage for a liquid crystal display device such as a car navigation system used in an environment where temperature changes rapidly. And a temperature compensation circuit for a liquid crystal display element.

[0002]

2. Description of the Related Art A temperature compensating circuit for a liquid crystal display device which obtains a required contrast with respect to a temperature change in the liquid crystal display device has been disclosed in Japanese Patent Application Laid-Open No. 61-141493. This temperature compensation circuit 5 for a liquid crystal display element
0, as shown in FIG. 7, a resistance dividing circuit 51 for generating a driving voltage of the liquid crystal display element, a temperature compensating circuit 54 including a posistor 52 and a temperature correcting resistor 53, and a plurality of operational amplifiers 55 including a voltage follower circuit. And an impedance conversion circuit 56.

In this temperature compensation circuit for a liquid crystal display element, a temperature change is replaced by a resistance value change by a posistor, so that a voltage dividing ratio of a resistance in a resistance dividing circuit changes.
The drive voltage of the liquid crystal display element is optimized by changing the bias ratio of the liquid crystal display element.

[0004]

As described above, in the conventional temperature compensation circuit for a liquid crystal display element, the drive voltage of the liquid crystal display element is adjusted by adjusting the bias ratio using a posistor and a correction resistor. can do. However, in the conventional temperature compensation circuit for a liquid crystal display element, the temperature characteristic cannot be specified because there is a variation in the temperature characteristic in the posistor and a variation in the temperature characteristic due to the material or quality in the liquid crystal display element. Therefore, there is a problem that it is difficult to optimize the display quality of the liquid crystal display device. In addition, since a posistor cannot be built in the integrated circuit, there is a problem that the posistor must be externally provided.

The present invention has been proposed in view of the above circumstances, and can generate an optimum drive voltage to be supplied to a liquid crystal display element in response to a change in temperature, and can be incorporated in an integrated circuit. It is an object of the present invention to provide a possible temperature compensation circuit for a liquid crystal display element.

[0006]

A temperature compensation circuit for a liquid crystal display device according to the present invention has the following features in order to achieve the above object.

That is, a temperature compensation circuit for a liquid crystal display element according to the present invention is a temperature compensation circuit for a liquid crystal display element for generating an optimum drive voltage to be supplied to the liquid crystal display element in response to a temperature change. A temperature detection power supply circuit including a switch that operates based on the control of the above, and a voltage adjustment resistance division circuit for adjusting an output voltage based on an input from the switch; a diode; a resistance division circuit; A temperature detection circuit comprising: a temperature change circuit configured to convert a temperature change into a count number by the counter operating in cooperation with a temperature detection output from the temperature detection circuit; and inputting the converted value to drive the liquid crystal display element optimally. A liquid crystal characteristic correction circuit for generating a voltage.

It is preferable that an interface circuit for extracting an output from the counter to the outside is provided.

It is preferable that a signal line of the interface circuit is also used as a control signal line of a liquid crystal display element driver.

[0010] The counter constituting the power supply circuit for temperature detection may be constituted by an up counter.

A voltage output from the temperature detecting power supply circuit is supplied to the comparator as a driving voltage;
The voltage obtained by the resistance division and the forward voltage of the diode, which changes based on temperature, are compared by the comparator, and the output of the comparator can be input to the counter.

Further, it is possible to select a resistance of the resistance dividing circuit based on an output from the counter and generate an optimum driving voltage for the liquid crystal display element based on a voltage obtained from the selected resistance. It is.

Since the temperature compensation circuit for a liquid crystal display element according to the present invention has the above-mentioned features, the driving of the comparator for comparing the voltage generated by the resistance dividing circuit with the forward voltage of the diode which changes with temperature is performed. By changing the voltage, the temperature can be detected. Then, based on the detected temperature and the temperature characteristics of the liquid crystal display element, an optimum driving voltage is supplied to the liquid crystal display element by the liquid crystal characteristic correction circuit, and the display quality of the liquid crystal display element can be optimized. .

Further, by forming a temperature detecting circuit with a semiconductor element, the temperature detecting circuit can be built in the integrated circuit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a temperature compensation circuit for a liquid crystal display device according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of a temperature compensation circuit for a liquid crystal display element according to an embodiment of the present invention, FIG. 2 is a graph showing characteristics of a temperature detection circuit, and FIG. FIG. 4 is a graph showing characteristics of a liquid crystal display element, FIG. 5 is a block diagram showing a circuit configuration of an up counter circuit, and a timing chart showing operation timing. FIG. 6 is a circuit of a liquid crystal characteristics correction circuit. FIG. 3 is a block diagram illustrating a configuration.

As shown in FIG. 1, a temperature compensating circuit 1 for a liquid crystal display element according to the present invention comprises a temperature detecting circuit 5 comprising a diode 2, a resistance dividing circuit 3 and a comparator 4, and a voltage adjusting resistance dividing circuit 6. A temperature detection power supply circuit 10 including an analog switch 7, an up counter 8, and a comparator 9, a liquid crystal characteristic correction circuit 11, a liquid crystal display element drive voltage generation circuit 12, and an interface circuit (I / F circuit) 13. Have.

The temperature detecting power supply circuit 10 is a circuit for changing the driving voltage of the temperature detecting circuit 5, and the liquid crystal characteristic correcting circuit 11 supplies the liquid crystal display element to the liquid crystal display element based on the output value from the up counter 8. The liquid crystal display element drive voltage generation circuit 12 is a circuit for determining a drive voltage, is a circuit for generating a drive voltage to be supplied to the liquid crystal display element, and the interface circuit 13 is a circuit for an external controller. This is a circuit for transmitting and receiving data also as a liquid crystal display element control signal.

As shown in FIG. 5, the up counter 8
It has four T-type flip-flops 14, and receives a clock and a control signal, and also receives a predetermined reset signal. When clocks are sequentially input to the up counter 8, the count value increases by "1". When the count value of the up counter 8 increases by “1”, the temperature detection drive voltage sequentially decreases according to the count value, as shown in FIG. Then, for example, when the count value becomes “1”, the ambient temperature (T1) is detected by the temperature detection circuit 5, and the output of the comparator 4 changes from the low level to the high level as shown in FIG. .

That is, as shown in FIG. 1, the up counter 8 outputs Q1, Q2, Q3, and Q4 in order from the bottom, and the analog switch 7 is turned off corresponding to each of the outputs Q1 to Q4 to detect the temperature. The voltage Vta corresponding to the count value is output from the comparator 9 configuring the power supply circuit 10 for use. At this time, the forward voltage of the diode 2 changes in accordance with the ambient temperature, and when the voltage Vta corresponding to the ambient temperature is input, the inputs node1 and node2 of the comparator 4 forming the temperature detecting circuit 5 are input.
Are equal. Therefore, the comparator 4 outputs a High level as a control signal of the up counter 8.

Then, when the control signal of the up counter 8 output from the temperature detecting circuit 5 becomes High level,
The counting operation of the up counter 8 stops. Therefore, the up counter 8 holds and outputs a count value (corresponding to the ambient temperature) corresponding to the voltage Vta output from the temperature detection power supply circuit 10.

As shown in FIG. 6, the liquid crystal characteristic correction circuit 11 has a resistance which satisfies the relationship between the ambient temperatures TL, T1,..., TH and the optimum voltages VM0,. That is, resistors R, R0, R1,..., R15 satisfying the output characteristics of the liquid crystal display element shown in FIG.
And a comparator 15.

The liquid crystal characteristic correction circuit 11 receives a count value during a period when the control signal for the up counter 8 is at a high level. For example, since the count value output from the up counter 8 when the ambient temperature is T1 is “1”, the optimum voltage VM1 of the liquid crystal display element is output based on the resistance ratio between the resistors R1 and R.

In this manner, the drive voltage corresponding to the temperature characteristics of the liquid crystal display element is determined, and the liquid crystal display element drive voltage generation circuit 12 generates the optimum drive voltage.

The liquid crystal characteristic correction circuit 11 includes a RAM.
It is preferable that a memory such as the above is built-in so that data of an optimum voltage corresponding to the output characteristics of the liquid crystal display element can be stored in the memory. With such a configuration, the data stored in the memory can be changed to accommodate a plurality of liquid crystal display elements having different output characteristics.

In the temperature compensation circuit 1 for a liquid crystal display element according to the present embodiment, the signal line of the interface circuit 13 is also used as a control signal line of a liquid crystal display element driver (not shown). Therefore, the temperature data can be transmitted to an external controller (such as a liquid crystal display element controller or a microcomputer) via the interface circuit 13, and external control can be performed.

The temperature compensating circuit 1 for a liquid crystal display element according to the above-described embodiment has a configuration capable of detecting the temperature in 16 steps. The temperature can be detected with high accuracy. In the temperature compensation circuit 1 for a liquid crystal display element according to the present invention, a down counter circuit can be used instead of the up counter 8 described above.

[0028]

As described above, the temperature compensation circuit for a liquid crystal display device according to the present invention includes a temperature detection circuit and a liquid crystal characteristic correction circuit. Therefore, an optimal drive voltage to be supplied to the liquid crystal display element can be generated by the temperature detection circuit and the liquid crystal characteristic correction circuit in accordance with the temperature change. For this reason, high-quality display can always be performed even with a liquid crystal display element such as a car navigation system used in an environment where the temperature changes rapidly.

Further, by forming the temperature detecting circuit by the semiconductor element, the temperature detecting circuit can be built in the integrated circuit. In addition, an interface circuit for extracting an output from the counter to the outside is provided, and a signal line of the interface circuit is also used as a control signal line of the liquid crystal display element driver. Therefore, by transmitting the temperature data to the external controller via the interface circuit, the liquid crystal display element can be controlled from the outside.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a temperature compensation circuit for a liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a graph showing characteristics of a temperature detection circuit.

FIG. 3 is a graph showing output characteristics of a comparator.

FIG. 4 is a graph showing characteristics of a liquid crystal display element.

5A is a block diagram showing a circuit configuration of an up counter, and FIG. 5B is a timing chart showing operation timing.

FIG. 6 is a block diagram illustrating a circuit configuration of a liquid crystal characteristic correction circuit.

FIG. 7 is a block diagram showing a circuit configuration of a conventional temperature compensation circuit for a liquid crystal display element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature compensation circuit for liquid crystal display elements 2 Diode 3 Resistance division circuit 4 Comparator 5 Temperature detection circuit 6 Resistance division circuit for voltage adjustment 7 Analog switch 8 Up counter 9 Comparator 10 Temperature detection power supply circuit 11 Liquid crystal characteristic correction circuit 12 Liquid crystal display element Drive voltage generation circuit 13 Interface circuit 14 T-type flip-flop 15 Comparator 50 Conventional temperature compensation circuit for liquid crystal display element 51 Resistance divider circuit 52 Posistor 53 Temperature compensation resistor 54 Temperature compensation circuit 55 Operational amplifier 56 Impedance conversion circuit

Claims (6)

[Claims] 1. A temperature compensating circuit for a liquid crystal display element for generating an optimum drive voltage to be supplied to a liquid crystal display element in response to a temperature change, comprising: a switch that operates based on control of a counter; A temperature detection power supply circuit including a voltage adjustment resistance division circuit for adjusting an output voltage based on the input of the temperature detection circuit, a diode, a resistance division circuit, and a comparator; and a temperature detection circuit. Convert the temperature change into a count number by the counter operating in cooperation with the temperature detection output of,
A liquid crystal display element temperature compensation circuit, comprising: a liquid crystal characteristic correction circuit for generating an optimum drive voltage for the liquid crystal display element by inputting the conversion value. 2. The temperature compensation circuit for a liquid crystal display device according to claim 1, further comprising an interface circuit for extracting an output from said counter to the outside. 3. The temperature compensation circuit for a liquid crystal display device according to claim 2, wherein a signal line of the interface circuit is also used as a control signal line of a liquid crystal display device driver. 4. The temperature compensating circuit for a liquid crystal display device according to claim 1, wherein said counter constituting said temperature detecting power supply circuit is an up counter. 5. A voltage output from the temperature detection power supply circuit is supplied to the comparator as a drive voltage, and a voltage obtained by the resistance division and a forward voltage of the diode that changes based on temperature are calculated. 5. The temperature compensation circuit for a liquid crystal display element according to claim 1, wherein the temperature is compared by the comparator, and an output of the comparator is input to the counter. 6. 6. The method according to claim 1, wherein a resistance of the resistance dividing circuit is selected based on an output from the counter, and an optimum driving voltage is generated for the liquid crystal display element based on a voltage obtained from the selected resistance. The temperature compensation circuit for a liquid crystal display element according to any one of claims 1 to 5, wherein