Temperature compensation type display and contrast control circuit thereof

Abstract

The invention discloses a temperature compensation type display and a contrast control circuit thereof, and relates to the technical field of displayers, when the environment temperature rises, the positive conduction resistance of a first Schottky diode and a second Schottky diode is correspondingly increased, the detection efficiency is reduced, and therefore the standard negative voltage output by detection is reduced; on the contrary, when the environment temperature is reduced, the positive conduction resistance is reduced, the detection efficiency is improved, the standard negative voltage output by detection is correspondingly increased, temperature compensation of the standard negative voltage is achieved, and the negative voltage after temperature compensation outputs driving voltage to a duty ratio control voltage generator and contrast control voltage to a liquid crystal sheet through a negative voltage output driver. The driving voltage outputs duty ratio control voltages of different gears through the duty ratio control voltage generator, and the contrast control voltage and the duty ratio control voltages of different gears are used for jointly controlling the liquid crystal sheet, so that the contrast in subjective evaluation of human vision in a full-temperature working range is kept constant.

Description

Technical Field

[0001] The present invention relates to the technical field of displays, and in particular to a temperature compensation type display and a contrast control circuit thereof. Background Art

[0002] The display is a key component for human-computer interaction in automation equipment. It controls the contrast of the display through software and hardware to clearly display complex graphical interfaces and text information, thereby enriching the user's visual experience. Figure 1 As shown, Figure 1 This is a schematic diagram of the principle of a liquid crystal display, which consists of a liquid crystal panel, a liquid crystal dot matrix row and column scanning drive system, a liquid crystal graphic display control system, and a control circuit for controlling the contrast of a temperature-compensated display. In order to ensure that the contrast of the display in the subjective evaluation of human vision remains constant within the full temperature operating range, it is necessary to perform temperature compensation on the control voltage input to the liquid crystal panel to control the contrast, wherein the control voltage includes a contrast control voltage and a duty cycle control voltage. If the control voltage is fixed without temperature compensation adjustment measures, the contrast of the display becomes higher at high temperatures, and the display appears "white", and the contrast of the display becomes lower at low temperatures, and the display appears "black". Therefore, if the contrast of the liquid crystal display is too high or too low in high or low temperature environments, the user will not be able to recognize the display information of the liquid crystal display.

[0003] At present, a thermistor is usually set in the negative voltage output driver to perform temperature compensation on the control voltage. However, since the resistance value of the thermistor is nonlinearly related to temperature, this limits the temperature compensation range of the thermistor when performing temperature compensation on the control voltage. At the same time, this temperature compensation method has the risk of over-compensation of the control voltage as the temperature increases. If the thermistor fails, the display may also face the dangerous situation of display failure. In addition, the thermistor will also consume the output power of the negative voltage output driver and increase the power consumption of the display. Summary of the invention

[0004] The purpose of the present invention is to provide a temperature compensated display and a contrast control circuit thereof, which utilizes a contrast control voltage and a duty cycle control voltage of different gears to jointly control a liquid crystal panel, thereby achieving a constant contrast in subjective visual evaluation of the human eye within the full temperature working range, thereby ensuring the uniformity and stability of the display effect of the display.

[0005] In order to solve the above technical problems, the present invention provides a control circuit for the contrast of a temperature-compensated display, comprising:

[0006] A capacitor, wherein the first end of the capacitor is connected to direct current, and the second end is respectively connected to the positive electrode of the first Schottky diode and the negative electrode of the second Schottky diode; the first Schottky diode, wherein the negative electrode of the first Schottky diode is grounded; the second Schottky diode, wherein the positive electrode of the second Schottky diode is connected to the input end of a negative voltage output driver, and is used to cooperate with the capacitor and the first Schottky diode to convert the direct current into a standard negative voltage; the negative voltage output driver, wherein the first output end of the negative voltage output driver is connected to the first input end of a duty cycle control voltage generator, and the second output end is connected to a liquid crystal panel, and is used to output a driving voltage and a contrast control voltage based on the standard negative voltage; the duty cycle control voltage generator, wherein the output end is connected to the liquid crystal panel, and is used to output duty cycle control voltages of different gears based on the driving voltage.

[0007] Optionally, it further includes: a first filtering module, wherein a first end of the first filtering module is connected to the anode of the second Schottky diode, and a second end is grounded.

[0008] Optionally, the first filtering module includes at least two filtering capacitors, and the capacitance values ​​of at least two of the filtering capacitors are different.

[0009] Optionally, it further includes: a DC / DC converter, wherein the input end of the DC / DC converter is connected to the direct current, and the output end is connected to the first end of the capacitor, and is used to convert the direct current into a square wave signal.

[0010] Optionally, the duty cycle control voltage generator includes: N voltage-dividing resistors, the N voltage-dividing resistors are connected in series in sequence, and one end of the series connection is connected to the first output end of the negative voltage output driver, and the other end is connected to a power supply; N-1 emitter followers, the input ends of the N-1 emitter followers are respectively connected one-to-one with the common ends of each adjacent two of the N voltage-dividing resistors, and the output ends are connected to the liquid crystal panel for outputting duty cycle control voltages of different gears, and N is an integer not less than 2.

[0011] Optionally, the duty cycle control voltage generator also includes: N current limiting resistors, the first ends of N-1 of the current limiting resistors are respectively connected to the output ends of N-1 emitter followers, the first end of the remaining 1 current limiting resistor is connected to the first output end of the negative voltage output driver, and the second ends of all the current limiting resistors are connected to the liquid crystal panel.

[0012] Optionally, the duty cycle control voltage generator also includes: N second filter modules, the first ends of N-1 second filter modules are respectively connected to the output ends of N-1 emitter followers, the first end of the remaining 1 second filter module is connected to the first output end of the negative voltage output driver, and the second ends of all the second filter modules are grounded.

[0013] Optionally, the duty cycle control voltage generator also includes: N third filter modules, the first ends of N-1 of the third filter modules are respectively connected to the common ends of each adjacent two of the N voltage-divider resistors, the first end of the remaining 1 third filter module is connected to the first output end of the negative voltage output driver, and the second ends of all the third filter modules are grounded.

[0014] Optionally, the negative voltage output driver includes: a first fixed resistor, a first end of the first fixed resistor is connected to the anode of the second Schottky diode, and a second end is connected to the base of the transistor; the transistor, the collector of the transistor is connected to the first input terminal of the duty cycle control voltage generator, and the emitter is connected to the first fixed contact of the potentiometer, for outputting a driving voltage from the collector and a contrast control voltage from the base when the anode of the second Schottky diode outputs a standard negative voltage; the potentiometer, the second fixed contact of the potentiometer is grounded, and the sliding contact is connected to the first end of the second fixed resistor; the second fixed resistor, the second end of the second fixed resistor is grounded.

[0015] The present invention also provides a temperature compensation display, including a liquid crystal panel and a contrast control circuit of the temperature compensation display as described above, wherein the liquid crystal panel is connected to the contrast control circuit of the temperature compensation display.

[0016] The invention provides a temperature compensation type display and a contrast control circuit thereof. The contrast control circuit of the temperature compensation type display comprises a negative voltage output driver, a duty cycle control voltage generator and a voltage doubling full-wave rectifier circuit composed of a capacitor, a first Schottky diode and a second Schottky diode. When the ambient temperature rises, the forward conduction resistance of the first Schottky diode and the second Schottky diode increases accordingly, resulting in a decrease in detection efficiency, thereby reducing the standard negative voltage output by the detection. On the contrary, when the ambient temperature decreases, the forward conduction resistance decreases, the detection efficiency increases, and the standard negative voltage output by the detection increases accordingly, thereby achieving temperature compensation for the standard negative voltage. The negative voltage after temperature compensation outputs a driving voltage to a duty cycle control voltage generator and a contrast control voltage to a liquid crystal chip through a negative voltage output driver. The driving voltage outputs duty cycle control voltages of different gears through the duty cycle control voltage generator. The contrast control voltage and the duty cycle control voltages of different gears are used to jointly control the liquid crystal chip, thereby achieving a constant contrast in subjective visual evaluation of human eyes within the full temperature working range, thereby ensuring the uniformity and stability of the display effect of the display. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of the principle of a liquid crystal display;

[0019] Figure 2 A schematic diagram of the principle of a contrast control circuit for a temperature compensation display provided by the present invention;

[0020] Figure 3 A schematic diagram of temperature characteristics of contrast ratio of a multi-level grayscale liquid crystal display provided by the present invention;

[0021] Figure 4 The present invention provides a schematic diagram of the principle of a contrast control circuit for a specific temperature compensation display. DETAILED DESCRIPTION

[0022] The core of the present invention is to provide a temperature-compensated display and a contrast control circuit thereof, which utilizes a contrast control voltage and a duty cycle control voltage of different gears to jointly control a liquid crystal panel, thereby achieving a constant contrast in the subjective evaluation of human vision within the full temperature working range, thereby ensuring the uniformity and stability of the display effect of the display.

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] At present, thermistors are usually set in negative voltage output drivers to perform temperature compensation on the control voltage. However, since the resistance of the thermistor is nonlinear with temperature, this limits the temperature compensation range of the thermistor when performing temperature compensation on the control voltage. For example, if a negative temperature coefficient thermistor is used to perform temperature compensation on the control voltage, the resistance of the negative temperature coefficient thermistor will decrease with increasing temperature and will be nonlinear. Therefore, it will only have a compensation effect in high temperature areas. At the same time, there is a risk of over-compensation of the contrast as the temperature increases. And if the thermistor fails, there may be a dangerous situation of display failure. In addition, the thermistor will consume the output power of the negative voltage output driver and increase the power consumption of the display.

[0025] In order to solve the above technical problem, the present invention provides a control circuit for the contrast of a temperature compensation display.

[0026] Specifically, see Figure 2 As shown, Figure 2 The present invention provides a schematic diagram of the principle of a contrast control circuit for a temperature compensation display, wherein the liquid crystal cell of the present invention may be a multi-level grayscale liquid crystal cell.

[0027] The contrast control circuit of the temperature compensation display comprises: a capacitor C, a first end of the capacitor C is connected to direct current, and a second end is respectively connected to the positive electrode of a first Schottky diode D1 and the negative electrode of a second Schottky diode D2; a first Schottky diode D1, a negative electrode of the first Schottky diode D1 is grounded; a second Schottky diode D2, a positive electrode of the second Schottky diode D2 is connected to the input end of a negative voltage output driver 1, and is used to cooperate with the capacitor C and the first Schottky diode D1 to convert direct current into a standard negative voltage; a negative voltage output driver 1, a first output end of the negative voltage output driver 1 is connected to the first input end of a duty cycle control voltage generator 2, and a second output end is connected to a liquid crystal panel 3, and is used to output a driving voltage and a contrast control voltage based on the standard negative voltage; a duty cycle control voltage generator 2, an output end of which is connected to the liquid crystal panel 3, and is used to output duty cycle control voltages of different gears based on the driving voltage.

[0028] The contrast control circuit of the temperature compensation display includes a negative voltage output driver 1, a duty cycle control voltage generator 2, and a voltage doubling full-wave rectifier circuit composed of a capacitor C, a first Schottky diode D1, and a second Schottky diode D2. In normal operation, that is, when the ambient temperature is a normal temperature of 23°C, the first Schottky diode D1 and the second Schottky diode D2 mainly realize their detection and rectification functions through the Schottky barrier formed by the contact between the metal and the semiconductor. When the first Schottky diode D1 and the second Schottky diode D2 are in a forward biased state, that is, a forward voltage is applied, and electrons flow from the N-type semiconductor to the metal side. Since the potential energy of electrons in the metal is low, these electrons can overcome the barrier and enter the metal side, thereby forming a current. In this case, the first Schottky diode D1 and the second Schottky diode D2 exhibit a low forward voltage drop, usually between 0.2V and 0.4V, which is much lower than the 0.6V to 0.7V of the traditional PN junction diode. When the first Schottky diode D1 and the second Schottky diode D2 are in a reverse bias state, that is, a reverse voltage is applied, the barrier height increases, preventing the current from flowing. At this time, only a small amount of leakage current exists because there is not enough energy for electrons to return from the metal side to the semiconductor side.

[0029] In addition, the liquid crystal cell 3 in this embodiment can be a multi-level grayscale liquid crystal cell, which has a special temperature characteristic. When the ambient temperature decreases, the contrast of the multi-level grayscale liquid crystal cell decreases, and the display is "black". At this time, the contrast control voltage must be increased to compensate for the decrease in the contrast of the multi-level grayscale liquid crystal cell; on the contrary, when the ambient temperature increases, the contrast of the multi-level grayscale liquid crystal cell increases, and the display is "white". At this time, the contrast control voltage must be reduced to suppress the increase in the contrast of the multi-level grayscale liquid crystal cell. The detection efficiency of the Schottky diode has a temperature characteristic: when the ambient temperature increases, the forward conduction resistance of the Schottky diode increases accordingly, resulting in a decrease in the detection efficiency, thereby reducing the standard negative voltage of the detection output; on the contrary, when the ambient temperature decreases, the forward conduction resistance decreases, the detection efficiency increases, and the standard negative voltage of the detection output increases accordingly. Therefore, this embodiment adopts the first Schottky diode D1 and the second Schottky diode D2, and the temperature characteristics of the detection efficiency of the two are opposite to the temperature characteristics of the contrast of the multi-level grayscale liquid crystal panel. When the ambient temperature changes, the standard negative voltage is temperature compensated, thereby achieving the suppression of the change of the contrast of the multi-level grayscale liquid crystal panel by controlling the contrast control voltage.

[0030] It should be noted that the Schottky detector diode has the advantages of low on-state voltage, small on-state resistance, large detection current, high reverse withstand voltage, good safety, and high detection efficiency, and is the first choice for voltage doubler full-wave rectifier circuits. Moreover, a notable feature of the Schottky diode is its fast switching speed and extremely short reverse recovery time (nanosecond level), which makes it very effective in high-frequency applications. In addition, due to its simple structure and the absence of a depletion layer, there is no charge storage problem, so it can switch from the on state to the off state faster.

[0031] Furthermore, the negative voltage after temperature compensation outputs a driving voltage to the duty cycle control voltage generator 2 and a contrast control voltage to the liquid crystal panel 3 through the negative voltage output driver 1. The driving voltage outputs a duty cycle control voltage of different gears through the duty cycle control voltage generator 2. The contrast control voltage and the duty cycle control voltage of different gears are used to jointly control the liquid crystal panel 3, so that the contrast of the subjective visual evaluation of the human eye remains constant within the full temperature working range, ensuring the uniformity and stability of the display effect of the display. For details, please refer to Figure 3 As shown, Figure 3 The present invention provides a schematic diagram of the temperature characteristic of the contrast ratio of a multi-level grayscale liquid crystal display, wherein the full temperature range of the multi-level grayscale liquid crystal display can be -20°C to +70°C.

[0032] Among them, capacitor C can be used to filter out high-frequency ripple and convert DC power into a relatively smooth DC voltage. It can also be used to store energy. In the voltage-doubling full-wave rectifier circuit, capacitor C is used to store charge and is charged alternately in each AC cycle, so that the output voltage is higher than the input voltage, helping to achieve voltage doubling.

[0033] It can be seen that this embodiment realizes the output voltage drive of the voltage-doubling full-wave rectifier circuit through the capacitor C, the first Schottky diode D1 and the second Schottky diode D2, on the one hand, and also realizes the automatic temperature compensation of the contrast in the subjective evaluation of human vision within the full temperature working range, and avoids the defects of using conventional negative temperature coefficient thermistors to realize the automatic temperature compensation of the contrast. The circuit has higher reliability and simple debugging. The effect of the automatic temperature compensation of the contrast in the subjective evaluation of human vision within the full temperature working range is more obvious, thereby improving the use efficiency of the display.

[0034] Based on the above embodiments:

[0035] See also Figure 4 As shown, Figure 4 The present invention provides a schematic diagram of the principle of a contrast control circuit for a specific temperature compensation display. The present invention takes two filter capacitors and five voltage divider resistors 6 as examples, and accordingly, there are five emitter followers 7, current limiting resistors 8 and second filter modules 9, and five third filter modules 10.

[0036] As an optional embodiment, it further includes: a first filtering module 4, a first end of the first filtering module 4 is connected to the anode of the second Schottky diode D2, and a second end is grounded.

[0037] Specifically, in order to make the standard negative voltage output by the voltage-doubling full-wave rectifier circuit smoother and reduce pulsation, thereby providing a more stable standard negative voltage, the present invention provides a first filtering module 4 for filtering out clutter and outputting a smoother standard negative voltage.

[0038] It can be seen that the first filtering module 4 can effectively filter out noise and interference components in the standard negative voltage, smooth the standard negative voltage, remove high-frequency noise, make the standard negative voltage more stable, and thus improve the quality of the standard negative voltage.

[0039] As an optional embodiment, the first filtering module 4 includes at least two filtering capacitors, and the capacitance values ​​of the at least two filtering capacitors are different.

[0040] Specifically, filter capacitors are often used in power supply voltage stabilization circuits, and their main function is to reduce the ripple amplitude at the power supply output end, thereby ensuring the normal operation of the circuit. The first filter module 4 includes at least two filter capacitors, and the capacitance values ​​of at least two filter capacitors are different, so as to achieve more precise frequency adjustment and optimization according to specific needs. In this embodiment, two filter capacitors are taken as an example, and the capacitance values ​​of the two filter capacitors are different. The two filter capacitors jointly filter out clutter in different frequency bands, which can more effectively reduce the AC component of the output standard negative voltage and make the DC output smoother.

[0041] It can be seen that by using multiple capacitors with different capacitance values, a wider filtering frequency range can be achieved, thereby improving the filtering effect and enhancing the anti-interference ability of the circuit.

[0042] As an optional embodiment, it further includes: a DC / DC converter 5, wherein the input end of the DC / DC converter 5 is connected to direct current, and the output end is connected to the first end of the capacitor C, for converting direct current into a square wave signal.

[0043] Specifically, the DC / DC converter 5 uses PWM (Pulse width modulation) technology to chop the DC power into a square wave (pulse wave), and changes the output voltage by adjusting the duty cycle of the square wave. This square wave signal is the key to achieving voltage gain in the voltage doubler full-wave rectifier circuit, because the voltage doubler full-wave rectifier circuit can use two half waves in each AC cycle to charge the capacitor C1, thereby increasing the output voltage. Among them, this square wave signal is the control signal of the internal switch of the DC / DC chip U1, which is used to drive the external inductor L and the Schottky diode to achieve voltage conversion.

[0044] The DC / DC converter 5 includes an inductor L, a DC / DC chip U1, a third fixed resistor R3, a fourth fixed resistor R4, a fifth fixed resistor R5, a first capacitor C1 and a second capacitor C2. The first end of the first capacitor C1 is connected to direct current, and the second end is grounded; the first end of the fourth fixed resistor R4 is connected to the positive electrode of the second Schottky diode D2, and the second end is connected to the first end of the fifth fixed resistor R5, and the second end of the fifth fixed resistor R5 is grounded; the second capacitor C2 is connected in parallel with the fourth fixed resistor R4; the first input end of the DC / DC chip U1 is connected to direct current, the second input end is connected to direct current through the third fixed resistor R3, the first output end is connected to the first end of the capacitor C, the second output end is grounded, and the third output end is connected to the common end of the fourth fixed resistor R4 and the fifth fixed resistor R5.

[0045] It should be noted that the DC / DC chip U1 contains a switch, usually a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), which is periodically turned on and off at high frequencies (usually tens of kilohertz to several megahertz). The on and off of the switch generates a high-frequency square wave signal, which is used to drive a filter network composed of an inductor and a capacitor. Most DC / DC chips U1 contain a feedback loop for monitoring the output standard negative voltage and adjusting the duty cycle of the switch to keep the output standard negative voltage stable. Through feedback control, the DC / DC chip U1 can dynamically adjust the behavior of the switch to ensure that the output standard negative voltage remains stable when the load changes or the input voltage fluctuates.

[0046] Among them, when the NMOS switch inside the DC / DC chip U1 is turned on, the inductor L starts to charge; when the NMOS switch is turned off, the inductor L releases energy and provides current to the subsequent circuit through the Schottky diode. If the feedback voltage fed back from the third output terminal of the DC / DC chip U1 is lower than the preset feedback voltage threshold, the circuit inside the DC / DC chip U1 will be closed, and the capacitor C will provide energy for the Schottky diode; when the feedback voltage fed back from the third output terminal of the DC / DC chip U1 is not lower than the preset feedback voltage threshold, the internal circuit is re-enabled, the NMOS switch is turned on, and the current of the inductor L begins to rise; when the current of the inductor L reaches 100mA, the comparator inside the DC / DC chip U1 is triggered, and the NMOS switch is turned off for 400ns. During this period, the inductor L continues to provide current to the Schottky diode. This process is repeated until the output standard negative voltage is stable.

[0047] For example, if the DC / DC chip U1 is AIC1653 model, when the input DC power is +5V, the NMOS switch inside the DC / DC chip U1 controls the first output terminal, and the first output terminal of the DC / DC chip U1 will output a stable periodic square wave signal of +4.93V. The square wave signal is driven by a voltage-doubling full-wave rectifier circuit to generate a standard negative voltage with a voltage value of -21.70V.

[0048] It can be seen that the DC / DC chip U1 controls the on and off of the switch inside the DC / DC chip U1 through the input DC power and feedback voltage, and generates a square wave signal through PWM technology. Under PWM technology, the switching frequency remains constant and the switching frequency does not change. This constant frequency helps to reduce noise and improve the efficiency of the power supply, and enhances the reliability and adaptability of the circuit.

[0049] As an optional embodiment, the duty cycle control voltage generator 2 includes: N voltage dividing resistors 6, the N voltage dividing resistors 6 are connected in series in sequence, and one end of the series connection is connected to the first output end of the negative voltage output driver 1, and the other end is connected to the power supply ( Figure 4 VDD in the middle); N-1 emitter followers 7, the input ends of the N-1 emitter followers 7 are connected to the common ends of every two adjacent voltage-dividing resistors 6 in the N voltage-dividing resistors 6 in a one-to-one correspondence, and the output ends are connected to the liquid crystal panel 3 for outputting duty cycle control voltages of different gears, and N is an integer not less than 2.

[0050] Specifically, in order to make the input driving voltage generate control voltages of different gears according to a certain ratio, so as to realize accurate distribution and adjustment of the input driving voltage and obtain the required voltage value, a voltage dividing network can be constructed by using N voltage dividing resistors 6, and the input ends of N-1 emitter followers 7 are respectively connected to the common ends of each adjacent two voltage dividing resistors 6 in the N voltage dividing resistors 6 in a one-to-one correspondence to output duty cycle control voltages of different gears; wherein N is an integer not less than 2.

[0051] In practical applications, the emitter follower 7 can improve the input impedance of the circuit, reduce the impact on the previous stage circuit, and provide a stable output impedance to drive the subsequent circuit or load.

[0052] It should be noted that the emitter follower 7, also known as a common collector amplifier or a voltage follower, is a common amplifier circuit, which is characterized by high input impedance, low output impedance, and the input signal and the output signal are in phase. The voltage gain of the emitter follower 7 is close to 1, which means that it will not significantly amplify or reduce the voltage amplitude of the signal, but can provide current amplification, so it has a certain power amplification effect.

[0053] It can be seen that the duty cycle control voltage generator 2 outputs N duty cycle control voltages with N voltage-dividing resistors 6 and N-1 emitter followers 7, which together with the contrast control voltage output by the negative voltage output driver 1 control the contrast change of the liquid crystal panel 3, so that the contrast of the display remains constant in the subjective visual evaluation of the human eye within the full temperature working range.

[0054] As an optional embodiment, the duty cycle control voltage generator 2 also includes: N current limiting resistors 8, the first ends of N-1 current limiting resistors 8 are respectively connected to the output end of the emitter follower 7, the first end of the remaining 1 current limiting resistor 8 is connected to the first output end of the negative voltage output driver 1, and the second ends of all current limiting resistors 8 are connected to the liquid crystal panel 3.

[0055] Specifically, when the current in the circuit exceeds the rated withstand current of the device, it may cause mechanical damage to the device, and if the circuit is short-circuited, the huge current generated instantly will cause the electrical circuit to heat up rapidly, and even cause a fire. In order to avoid these hazards, this embodiment sets N current-limiting resistors 8 in the duty cycle control voltage generator 2 to limit the flow of current to protect other components in the circuit from damage caused by excessive current. In addition, the N current-limiting resistors 8 can also play a role in voltage division in circuit design, helping to stabilize the voltage in the circuit.

[0056] It can be seen that in this embodiment, the flow of current is reduced by using N current-limiting resistors 8, thereby preventing other components in the circuit from being burned or damaged due to excessive current, which can not only protect other components in the circuit but also improve the reliability of the circuit.

[0057] As an optional embodiment, the duty cycle control voltage generator 2 also includes: N second filter modules 9, the first ends of N-1 second filter modules 9 are respectively connected to the output end of the emitter follower 7, the first end of the remaining 1 second filter module 9 is connected to the first output end of the negative voltage output driver 1, and the second ends of all second filter modules 9 are grounded.

[0058] Specifically, in order to make the duty cycle control voltage output by the duty cycle control voltage generator 2 smoother and reduce pulsation, the present invention provides N second filtering modules 9 for filtering out clutter.

[0059] It can be seen that the N second filter modules 9 can effectively filter out the noise and interference components of the voltage output from the output end of the emitter follower 7, smooth the voltage output from the output end of the emitter follower 7, make the output duty cycle control voltage more stable, thereby improving the quality of the duty cycle control voltage.

[0060] As an optional embodiment, the duty cycle control voltage generator 2 also includes: N third filter modules 10, the first ends of N-1 third filter modules 10 are respectively connected to the common ends of each adjacent two voltage-dividing resistors 6 among the N voltage-dividing resistors 6, the first end of the remaining 1 third filter module 10 is connected to the first output end of the negative voltage output driver 1, and the second ends of all the third filter modules 10 are grounded.

[0061] Specifically, the main features of the emitter follower 7 are high input impedance, low output impedance and voltage gain close to 1, so it is often used for voltage buffering and isolation. However, the frequency characteristics of the emitter follower 7 may be affected by the base series resistance and input capacitance, forming a low-pass filter effect, resulting in a decrease in high-frequency gain. In order to improve the frequency response and ensure the transmission quality of the signal in the high-frequency range, this implementation adds N third filtering modules 10, which can help filter out noise and interference, thereby improving signal quality.

[0062] It can be seen that the third filtering module 10 can effectively filter out the noise and interference components of the voltage input from the output end of the emitter follower 7, smooth the voltage input from the input end of the emitter follower 7, and reduce the influence of noise on the frequency characteristics of the emitter follower 7, thereby improving the quality of the duty cycle control voltage.

[0063] As an optional embodiment, the negative voltage output driver 1 includes: a first fixed resistor R1, the first end of the first fixed resistor R1 is connected to the positive electrode of the second Schottky diode D2, and the second end is connected to the base b of the transistor Q; the transistor Q, the collector c of the transistor Q is connected to the first input end of the duty cycle control voltage generator 2, and the emitter e is connected to the first fixed contact of the potentiometer RP, which is used to output the driving voltage from the collector c and the contrast control voltage from the base b when the positive electrode of the second Schottky diode D2 outputs a standard negative voltage; the potentiometer RP, the second fixed contact of the potentiometer RP is grounded, and the sliding contact is connected to the first end of the second fixed resistor R2; the second fixed resistor R2, the second end of the second fixed resistor R2 is grounded.

[0064] Specifically, the fixed resistor can limit the current in the circuit by its fixed resistance value. This embodiment adopts the first fixed resistor R1. When the load impedance of the negative voltage output driver 1 changes or other factors cause the current to be too large, the first fixed resistor R1 can protect the circuit and prevent it from being overloaded and damaged. At the same time, the first fixed resistor R1 can play a voltage dividing role, help balance the voltage distribution, and prevent a single electrical component from being subjected to excessive voltage. The transistor Q can be used as a switch of the negative voltage output driver 1, and the flow of current is adjusted by controlling its on and off states. The positive electrode of the second Schottky diode D2 outputs a standard negative voltage, which is divided by the first fixed resistor R1 and then outputs a driving voltage from the collector c, and outputs a contrast control voltage from the base b. The duty cycle control voltage output by the duty cycle control voltage generator 2 controls the contrast of the liquid crystal panel 3 to remain constant in the subjective evaluation of human vision within the full temperature working range, ensuring the uniformity and stability of the display effect of the display. Here, the second fixed resistor R2 is used to replace the thermistor, so the position of the sliding contact of the potentiometer RP can also be changed to adjust the driving voltage output from the collector c, thereby controlling the output of the duty cycle control voltage.

[0065] In addition, when the transistor Q outputs the contrast control voltage from the base b, it is connected to the liquid crystal panel 3 through a 0 ohm resistor. The 0 ohm resistor is only provided on the PCB (Printed Circuit Board) for the convenience of debugging or compatible design.

[0066] It can be seen that the negative voltage output driver 1 of this embodiment is composed of a first fixed resistor R1, a transistor Q, a potentiometer RP and a second fixed resistor R2. This design eliminates the traditional method of using a negative temperature coefficient thermistor for automatic contrast temperature control, thereby effectively avoiding the defect of uneven contrast automatic control and ensuring the uniformity and stability of the display effect.

[0067] The present invention also provides a temperature-compensated display, including a liquid crystal panel, and also including a contrast control circuit of the temperature-compensated display as described above, wherein the liquid crystal panel is connected to the contrast control circuit of the temperature-compensated display. The liquid crystal panel of the present invention adopts a multi-level grayscale liquid crystal panel, and the multi-level grayscale liquid crystal display is a key component for realizing human-computer interaction in automation equipment. It controls the contrast of the multi-level grayscale liquid crystal display through software and hardware, so as to clearly display complex graphical interfaces and text information, thereby enriching the user's visual experience. This display maintains the characteristics of low energy consumption and is particularly suitable for battery-powered equipment. It can work stably within a wide temperature range, showing strong environmental adaptability, while having high reliability and durability, and reducing the possibility of failure. In addition, the multi-level grayscale liquid crystal display achieves effective cost control while ensuring performance. These characteristics make it an ideal choice for industrial and special equipment that requires portable operation, battery power supply, and operation in harsh environments.

[0068] In addition, the multi-level grayscale liquid crystal display also includes a liquid crystal dot matrix row and column scanning drive system and a liquid crystal graphic display control system. The liquid crystal graphic display control system receives display commands and display information from the main control system through the display control interface of the main control system, and then the liquid crystal dot matrix row and column scanning drive system converts them into row and column dot matrix display drive data parameters required for liquid crystal display according to the timing control rules, controls the multi-level grayscale liquid crystal chip to realize graphic display, and the capacitor C, the first Schottky diode and the second Schottky diode used to control the contrast cooperate to generate a standard negative voltage, and the standard negative voltage is used to control the contrast of the multi-level grayscale liquid crystal chip.

[0069] It can be seen that, in the display provided by the present invention, when the ambient temperature rises, the forward conduction resistance of the first Schottky diode and the second Schottky diode increases accordingly, resulting in a decrease in the detection efficiency, thereby reducing the standard negative voltage of the detection output; on the contrary, when the ambient temperature decreases, the forward conduction resistance decreases, the detection efficiency increases, and the standard negative voltage of the detection output increases accordingly. This realizes temperature compensation of the control voltage, and achieves a constant contrast ratio in the subjective evaluation of human vision within the full temperature working range, ensuring the uniformity and stability of the display effect of the display.

[0070] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should also be noted that in this specification, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0071] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A contrast control circuit for a temperature-compensated display, characterized in that: include: A capacitor, wherein a first end of the capacitor is connected to direct current, and a second end of the capacitor is connected to the positive electrode of the first Schottky diode and the negative electrode of the second Schottky diode respectively; The first Schottky diode, wherein the cathode of the first Schottky diode is grounded; The second Schottky diode, the anode of which is connected to the input terminal of the negative voltage output driver, is used to cooperate with the capacitor and the first Schottky diode to convert the direct current into a standard negative voltage; The negative voltage output driver, wherein the first output terminal of the negative voltage output driver is connected to the first input terminal of the duty cycle control voltage generator, and the second output terminal is connected to the liquid crystal panel, and is used to output a driving voltage and a contrast control voltage based on the standard negative voltage; The duty cycle control voltage generator has an output end connected to the liquid crystal panel and is used to output duty cycle control voltages of different gears based on the driving voltage.

2. The contrast control circuit of a temperature compensation display according to claim 1, characterized in that: Also includes: A first filtering module, wherein a first end of the first filtering module is connected to the anode of the second Schottky diode, and a second end of the first filtering module is grounded.

3. The contrast control circuit of the temperature compensation type display according to claim 2, characterized in that: The first filtering module includes at least two filtering capacitors, and the capacitance values ​​of at least two of the filtering capacitors are different.

4. The contrast control circuit of the temperature compensation type display according to claim 1, characterized in that: Also includes: A DC / DC converter, wherein an input end of the DC / DC converter is connected to the direct current, and an output end of the DC / DC converter is connected to the first end of the capacitor, and is used for converting the direct current into a square wave signal.

5. The contrast control circuit of a temperature compensation display according to claim 1, characterized in that: The duty cycle control voltage generator comprises: N voltage-dividing resistors, the N voltage-dividing resistors are sequentially connected in series, and one end of the series connection is connected to the first output end of the negative voltage output driver, and the other end is connected to a power supply; N-1 emitter followers, the input ends of the N-1 emitter followers are connected one-to-one with the common ends of every two adjacent voltage-dividing resistors among the N voltage-dividing resistors, and the output ends are connected to the liquid crystal panel for outputting duty cycle control voltages of different gears, and N is an integer not less than 2.

6. The contrast control circuit of the temperature compensation type display according to claim 5, characterized in that: The duty cycle control voltage generator also includes: There are N current limiting resistors, the first ends of N-1 of the current limiting resistors are connected to the output ends of N-1 emitter followers respectively, the first end of the remaining 1 current limiting resistor is connected to the first output end of the negative voltage output driver, and the second ends of all the current limiting resistors are connected to the liquid crystal panel.

7. The contrast control circuit of a temperature compensation display according to claim 5, characterized in that: The duty cycle control voltage generator also includes: N second filter modules, the first ends of N-1 second filter modules are connected to the output ends of N-1 emitter followers respectively, the first end of the remaining 1 second filter module is connected to the first output end of the negative voltage output driver, and the second ends of all the second filter modules are grounded.

8. The contrast control circuit of a temperature compensation display according to claim 5, characterized in that: The duty cycle control voltage generator also includes: N third filter modules, the first ends of N-1 third filter modules are respectively connected to the common ends of each adjacent two voltage-dividing resistors among the N voltage-dividing resistors, the first end of the remaining 1 third filter module is connected to the first output end of the negative voltage output driver, and the second ends of all third filter modules are grounded.

9. The contrast control circuit of a temperature compensation display according to any one of claims 1 to 8, characterized in that: The negative pressure output driver comprises: A first fixed value resistor, wherein a first end of the first fixed value resistor is connected to the anode of the second Schottky diode, and a second end of the first fixed value resistor is connected to the base of the transistor; The triode, the collector of the triode is connected to the first input terminal of the duty cycle control voltage generator, the emitter is connected to the first fixed contact of the potentiometer, and is used to output a driving voltage from the collector and a contrast control voltage from the base when the anode of the second Schottky diode outputs a standard negative voltage; The potentiometer, wherein the second fixed contact of the potentiometer is grounded, and the sliding contact is connected to the first end of the second fixed value resistor; The second fixed value resistor, a second end of the second fixed value resistor is grounded.

10. A temperature compensation display, characterized in that: The device comprises a liquid crystal panel and a contrast control circuit of a temperature-compensated display as claimed in any one of claims 1 to 9, wherein the liquid crystal panel is connected to the contrast control circuit of the temperature-compensated display.

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