A temperature compensation display and its contrast control circuit

Abstract

The invention discloses a temperature-compensated display and a contrast control circuit thereof, relating to the technical field of displays. When the ambient temperature rises, the forward conduction resistance of a first Schottky diode and a second Schottky diode increases accordingly, resulting in a decrease in detection efficiency, thereby reducing the standard negative voltage output by the detection. Conversely, when the ambient temperature drops, 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 temperature-compensated negative voltage outputs a driving voltage to a duty cycle control voltage generator and a contrast control voltage to a liquid crystal panel 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 panel, thereby achieving a constant contrast in subjective visual evaluation by the human eye within the full temperature operating range.

Description

Technical Field

[0001] The present invention relates to the technical field of displays, and in particular to a temperature compensation 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 working principle of a liquid crystal display (LCD). The display consists of a liquid crystal panel, a liquid crystal dot matrix row and column scanning drive system, a liquid crystal graphics display control system, and a control circuit for controlling the contrast of a temperature-compensated display. To ensure that the display's contrast remains constant across the entire operating temperature range, as measured by subjective human visual evaluation, the contrast control voltage input to the LCD panel must be temperature compensated. This control voltage includes a contrast control voltage and a duty cycle control voltage. If the control voltage is fixed without temperature compensation, the display's contrast will increase at high temperatures, resulting in a "whitish" display; at low temperatures, the display's contrast will decrease, resulting in a "black" display. Therefore, if the contrast of an LCD display is too high or too low in either high or low temperature environment, the user will be unable to recognize the displayed information.

[0003] Currently, a thermistor is typically installed in a negative voltage output driver to perform temperature compensation on the control voltage. However, the nonlinear relationship between the resistance of the thermistor and temperature limits the temperature compensation range of the thermistor when performing temperature compensation on the control voltage. Furthermore, this temperature compensation method carries the risk of overcompensation of the control voltage as the temperature increases. Furthermore, if the thermistor fails, the display may experience a dangerous display failure. Furthermore, the thermistor consumes the output power of the negative voltage output driver, increasing 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 by the human eye within the full temperature operating range, thereby ensuring the uniformity and stability of the display effect of the display.

[0005] 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 the 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 the duty cycle control voltage generator, and the second output end 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, 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 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 the power supply; N-1 emitter followers, the input ends of the N-1 emitter followers are respectively connected one-to-one to 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 filtering modules, the first ends of N-1 second filtering modules are respectively connected to the output ends of N-1 emitter followers, the first end of the remaining 1 second filtering module is connected to the first output end of the negative voltage output driver, and the second ends of all second filtering modules are grounded.

[0013] Optionally, the duty cycle control voltage generator also includes: N third filtering modules, the first ends of N-1 of the third filtering modules are respectively connected to the common ends of each adjacent two voltage-dividing resistors in the N voltage-dividing resistors, the first end of the remaining 1 third filtering module is connected to the first output end of the negative voltage output driver, and the second ends of all third filtering 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 positive electrode 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 end 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 positive electrode 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-compensated display, comprising a liquid crystal panel and 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.

[0016] The present invention provides a temperature-compensated display and a contrast control circuit thereof. The contrast control circuit of the temperature-compensated 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 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. Conversely, when the ambient temperature drops, the forward 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 temperature-compensated negative voltage outputs a driving voltage to a duty cycle control voltage generator and a contrast control voltage to a liquid crystal panel through the 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 panel, thereby achieving a constant contrast in subjective visual evaluation by the human eye within the full temperature operating 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 following briefly introduces the prior art and the drawings required for use in the embodiments. 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 paying any 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-compensated display provided by the present invention;

[0020] Figure 3 A schematic diagram of the temperature characteristic of the 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-compensated display. DETAILED DESCRIPTION

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

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative efforts shall fall within the scope of protection of the present invention.

[0024] Currently, negative voltage output drivers typically incorporate thermistors for temperature compensation of the control voltage. However, the nonlinear relationship between thermistor resistance and temperature limits the temperature compensation range. For example, if a negative temperature coefficient (NTC) thermistor is used for temperature compensation, its resistance decreases with increasing temperature, exhibiting a nonlinear relationship. Therefore, it only provides compensation in high-temperature ranges, and there is a risk of overcompensation of contrast as temperature increases. Furthermore, if the thermistor fails, the display may fail. Furthermore, the thermistor consumes the output power of the negative voltage output driver, increasing the display's power consumption.

[0025] In order to solve the above technical problem, the present invention provides a contrast control circuit for a temperature-compensated 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-compensated display, wherein the liquid crystal panel of the present invention may be a multi-level grayscale liquid crystal panel.

[0027] The contrast control circuit of the temperature-compensated display includes: a capacitor C, a first end of the capacitor C being connected to direct current, and a second end being connected to the anode of a first Schottky diode D1 and the cathode of a second Schottky diode D2, respectively; a first Schottky diode D1, the cathode of which is grounded; a second Schottky diode D2, the anode of which is connected to the input end of a negative voltage output driver 1, and configured 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, the first output end of which is connected to the first input end of a duty cycle control voltage generator 2, and the second output end of which is connected to a liquid crystal panel 3, and configured to output a driving voltage and a contrast control voltage based on the standard negative voltage; and a duty cycle control voltage generator 2, the output end of which is connected to the liquid crystal panel 3, and configured to output duty cycle control voltages of different gears based on the driving voltage.

[0028] The contrast control circuit for this temperature-compensated display includes a negative voltage output driver 1, a duty cycle control voltage generator 2, and a voltage-doubling full-wave rectifier circuit consisting of a capacitor C, a first Schottky diode D1, and a second Schottky diode D2. During normal operation (i.e., at a normal ambient temperature of 23°C), the first and second Schottky diodes D1 and D2 primarily perform their detection and rectification functions through the Schottky barrier formed by the metal-semiconductor contact. When the first and second Schottky diodes D1 and D2 are forward-biased (i.e., when a forward voltage is applied), electrons flow from the N-type semiconductor to the metal. Due to the lower potential energy of electrons in the metal, these electrons are able to overcome the barrier and enter the metal, thus forming a current. In this state, the first and second Schottky diodes D1 and D2 exhibit a low forward voltage drop, typically between 0.2V and 0.4V, significantly lower than the 0.6V to 0.7V of traditional PN junction diodes. When the first and second Schottky diodes D1 and D2 are reverse biased, that is, when a reverse voltage is applied, the barrier height increases, preventing 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 panel 3 in this embodiment can be a multi-level grayscale liquid crystal panel. Multi-level grayscale liquid crystal panels have unique temperature characteristics. When the ambient temperature decreases, the contrast of the multi-level grayscale liquid crystal panel decreases, and the display appears "black". In this case, the contrast control voltage must be increased to compensate for the decrease in contrast of the multi-level grayscale liquid crystal panel. Conversely, when the ambient temperature increases, the contrast of the multi-level grayscale liquid crystal panel increases, and the display appears "white". In this case, the contrast control voltage must be reduced to suppress the increase in contrast of the multi-level grayscale liquid crystal panel. The detection efficiency of the Schottky diode has a temperature characteristic: when the ambient temperature increases, the forward resistance of the Schottky diode increases accordingly, resulting in a decrease in detection efficiency, thereby reducing the standard negative voltage of the detection output. Conversely, when the ambient temperature decreases, the forward resistance decreases, the detection efficiency increases, and the standard negative voltage of the detection output increases accordingly. Therefore, this embodiment uses a first Schottky diode D1 and a 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 goal of suppressing the change in the contrast of the multi-level grayscale liquid crystal panel by controlling the contrast control voltage.

[0030] It should be noted that Schottky detector diodes offer the advantages of low on-state voltage, low on-resistance, high detection current, high reverse voltage withstand, excellent safety, and high detection efficiency, making them the preferred choice for voltage-doubling full-wave rectifier circuits. Furthermore, a notable feature of Schottky diodes is their fast switching speed and extremely short reverse recovery time (nanoseconds), making them very effective in high-frequency applications. Furthermore, due to their simple structure and lack of a depletion layer, they eliminate charge storage issues, enabling faster switching from the on-state to the off-state.

[0031] Furthermore, the temperature-compensated negative voltage outputs a driving voltage to the duty cycle control voltage generator 2 and a contrast control voltage to the liquid crystal panel 3 via the negative voltage output driver 1. The driving voltage then outputs duty cycle control voltages of different gears via the duty cycle control voltage generator 2. The contrast control voltage and the duty cycle control voltages of different gears are used to jointly control the liquid crystal panel 3, thereby achieving a constant contrast ratio in the subjective evaluation of human vision within the full temperature operating range, thereby ensuring the uniformity and stability of the display effect. For details, please refer to Figure 3 As shown, Figure 3 This is a schematic diagram of the temperature characteristic of the contrast ratio of a multi-level grayscale liquid crystal display provided by the present invention, 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 alternately charged 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, through the capacitor C, the first Schottky diode D1 and the second Schottky diode D2, not only realizes the output voltage drive of the voltage-doubling full-wave rectifier circuit, but also realizes the automatic temperature compensation of the contrast ratio in the subjective evaluation of human vision within the full temperature operating range. This avoids the defects of using conventional negative temperature coefficient thermistors to realize the automatic temperature compensation of the contrast ratio. The circuit has higher reliability and is simple to debug. The effect of the automatic temperature compensation of the contrast ratio in the subjective evaluation of human vision within the full temperature operating range is more obvious, thereby improving the performance of the display.

[0034] Based on the above embodiment:

[0035] See Figure 4 As shown, Figure 4 This is a schematic diagram of a specific temperature-compensated display contrast control circuit provided by the present invention. The present invention uses two filter capacitors and five voltage-divider resistors 6 as examples. 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, the system further includes: a first filtering module 4 , wherein a first end of the first filtering module 4 is connected to the anode of the second Schottky diode D2 , and a second end thereof 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 commonly used in power supply voltage stabilization circuits. Their primary function is to reduce the ripple amplitude at the power supply output, thereby ensuring the normal operation of the circuit. The first filter module 4 includes at least two filter capacitors, and at least two filter capacitors have different capacitance values ​​to achieve more precise frequency adjustment and optimization based on specific needs. In this embodiment, two filter capacitors are used as an example, and the two filter capacitors have different capacitance values. 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 the direct current into a square wave signal.

[0043] Specifically, DC / DC converter 5 uses PWM (Pulse Width Modulation) technology to chop DC power into a square wave (pulse wave) and varies the output voltage by adjusting the square wave's duty cycle. This square wave signal is key to achieving voltage gain in the voltage-doubling full-wave rectifier circuit, as it uses two half-waves within each AC cycle to charge capacitor C1, thereby increasing the output voltage. This square wave signal serves as the control signal for the internal switches of DC / DC chip U1, driving external inductor L and Schottky diodes to achieve voltage conversion.

[0044] The DC / DC converter 5 includes an inductor L, a DC / DC chip U1, a third fixed-value resistor R3, a fourth fixed-value resistor R4, a fifth fixed-value resistor R5, a first capacitor C1, and a second capacitor C2. The first end of the first capacitor C1 is connected to a DC source, and the second end is grounded. The first end of the fourth fixed-value resistor R4 is connected to the anode of the second Schottky diode D2, and the second end is connected to the first end of the fifth fixed-value resistor R5, and the second end of the fifth fixed-value resistor R5 is grounded. The second capacitor C2 is connected in parallel with the fourth fixed-value resistor R4. The DC / DC chip U1 has a first input end connected to a DC source, a second input end connected to a DC source via the third fixed-value resistor R3, a first output end connected to the first end of the capacitor C, a second output end grounded, and a third output end connected to the common end of the fourth fixed-value resistor R4 and the fifth fixed-value 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). The switch is periodically turned on and off at a high frequency (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 the filter network composed of inductors and capacitors. 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 maintain the stability of the output standard negative voltage. 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] When the NMOS switch inside DC / DC chip U1 turns on, inductor L begins charging. When the NMOS switch turns off, inductor L releases energy, supplying current to the subsequent circuitry through the Schottky diode. If the feedback voltage from the third output terminal of DC / DC chip U1 falls below the preset feedback voltage threshold, the internal circuitry of DC / DC chip U1 shuts down, and capacitor C supplies energy to the Schottky diode. When the feedback voltage from the third output terminal of DC / DC chip U1 does not fall below the preset feedback voltage threshold, the internal circuitry reactivates, the NMOS switch turns on, and the current in inductor L begins to increase. When the current in inductor L reaches 100mA, the comparator inside DC / DC chip U1 triggers, turning the NMOS switch off for 400ns. During this time, inductor L continues to supply current to the Schottky diode. This process repeats until the output standard negative voltage stabilizes.

[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] As can be seen, DC / DC chip U1 uses the input DC power and feedback voltage to control the on and off of the switch inside DC / DC chip U1, generating a square wave signal through PWM technology. Under PWM technology, the switching frequency remains constant and does not change. This constant frequency helps reduce noise and improve power supply efficiency, enhancing 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, which 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 1, and the other end is connected to the power supply ( Figure 4 wherein VDD is N-1 emitter followers 7, wherein the input terminals of the N-1 emitter followers 7 are connected one-to-one to the common terminals of every two adjacent voltage-dividing resistors 6 in the N voltage-dividing resistors 6, and the output terminals of the emitter followers 7 are connected to the liquid crystal panel 3 for outputting duty cycle control voltages of different gears, where N is an integer not less than 2.

[0050] Specifically, in order to generate control voltages of different gears according to a certain ratio based on the input drive voltage, thereby achieving precise distribution and regulation of the input drive voltage and obtaining the desired voltage value, a voltage divider network can be constructed using N voltage divider resistors 6, with the input terminals of N-1 emitter followers 7 connected one-to-one to the common terminals of every two adjacent voltage divider resistors 6 in the N voltage divider resistors 6 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 emitter follower 7, also known as a common-collector amplifier or voltage follower, is a common amplifier circuit characterized by high input impedance, low output impedance, and the input and output signals being in phase. The voltage gain of emitter follower 7 is close to 1, meaning it does not significantly amplify or reduce the voltage amplitude of the signal, but it can provide current amplification, thus having a certain power amplification effect.

[0053] It can be seen that the duty cycle control voltage generator 2 outputs N levels of duty cycle control voltage using 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 operating 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. Furthermore, if the circuit shorts, the instantaneous huge current generated can cause the electrical circuit to rapidly heat up, or even cause a fire. To prevent these hazards, this embodiment provides N current-limiting resistors 8 in the duty cycle control voltage generator 2 to limit the flow of current and protect other components in the circuit from damage caused by excessive current. Furthermore, the N current-limiting resistors 8 can also act as voltage dividers in the circuit design, helping to stabilize the voltage in the circuit.

[0056] It can be seen that this embodiment reduces the flow of current by using N current-limiting resistors 8, thereby preventing other components in the circuit from being burned or damaged due to excessive current. This not only protects other components in the circuit, but also improves 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, and 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 filtering 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, and thus improve 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 divider resistors 6 in the N voltage divider 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 third filter modules 10 are grounded.

[0061] Specifically, the main features of the emitter follower 7 are high input impedance, low output impedance, and a 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 embodiment 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 the 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, and the second end of the second fixed resistor R2 is grounded.

[0064] Specifically, a fixed resistor can limit the current in the circuit through its fixed resistance value. This embodiment uses a first fixed resistor R1. When the load impedance of the negative voltage output driver 1 changes or other factors cause excessive current, the first fixed resistor R1 can protect the circuit from overload and damage. Furthermore, the first fixed resistor R1 can act as a voltage divider, helping to 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 for the negative voltage output driver 1, regulating the flow of current by controlling its on and off states. A standard negative voltage is output at the positive electrode of the second Schottky diode D2, which is divided by the first fixed resistor R1 and then output as a driving voltage from the collector c. A contrast control voltage is output from the base b, which, together with 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 across the entire temperature operating range, as determined by the subjective visual evaluation of the human eye, thereby ensuring the uniformity and stability of the display effect. Here, the second fixed resistor R2 is used instead of 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 transistor Q outputs a contrast control voltage from 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 debugging convenience or design compatibility.

[0066] It can be seen that the negative voltage output driver 1 of this embodiment is composed of a first fixed-value resistor R1, a transistor Q, a potentiometer RP, and a second fixed-value 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 comprising a liquid crystal panel and a contrast control circuit for the temperature-compensated display, as described above. The liquid crystal panel is connected to the contrast control circuit for the temperature-compensated display. The liquid crystal panel of the present invention utilizes a multi-grayscale liquid crystal panel. Multi-grayscale liquid crystal displays are key components for human-computer interaction in automated equipment. They utilize software and hardware to coordinate and control the contrast of the multi-grayscale liquid crystal display, thereby clearly displaying complex graphical interfaces and text information, thereby enriching the user's visual experience. This display maintains low energy consumption and is particularly suitable for battery-powered devices. It operates stably over a wide temperature range, demonstrating strong environmental adaptability, high reliability and durability, and reducing the likelihood of failure. Furthermore, the multi-grayscale liquid crystal display achieves effective cost control while ensuring performance. These characteristics make it an ideal choice for industrial and specialty equipment that requires portable operation, battery power, 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 main control system display control interface. The liquid crystal dot matrix row and column scanning drive system then converts these into the row and column dot matrix display drive data parameters required for the liquid crystal display according to timing control rules. This controls the multi-level grayscale liquid crystal panel to achieve graphic display. The capacitor C, the first Schottky diode, and the second Schottky diode used to control contrast cooperate to generate a standard negative voltage, which is used to control the contrast of the multi-level grayscale liquid crystal panel.

[0069] As can be seen, in the display provided by the present invention, when the ambient temperature rises, the forward resistance of the first and second Schottky diodes increases accordingly, resulting in a decrease in detection efficiency and, consequently, a decrease in the standard negative voltage output by the detection. Conversely, when the ambient temperature drops, the forward resistance decreases, the detection efficiency increases, and the standard negative voltage output by the detection increases accordingly. This achieves temperature compensation for the control voltage, ensuring that the contrast ratio, as measured by subjective human visual evaluation, remains constant across the full operating temperature range, ensuring uniformity and stability of the display's display quality.

[0070] In this specification, the various embodiments are described in a progressive manner, with each embodiment focusing on the differences from the other embodiments. Similar or identical parts between the various embodiments may be referred to in conjunction with each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and for relevant parts, reference may be made to the method description. It should also be noted that, in this specification, relational terms such as first and second, etc., are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

[0071] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily 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 is not limited to the embodiments shown herein but is intended to conform 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 a direct current, and a second end of the capacitor is connected to the anode of the first Schottky diode and the cathode of the second Schottky diode respectively; The first Schottky diode, wherein the cathode of the first Schottky diode is grounded; The second Schottky diode, wherein the anode of the second Schottky diode 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 has a first output terminal connected to the first input terminal of the duty cycle control voltage generator, and a second output terminal 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-compensated display according to claim 1, wherein: 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 a temperature-compensated display according to claim 2, wherein: The first filtering module includes at least two filtering capacitors, and the capacitance values ​​of the at least two filtering capacitors are different.

4. The contrast control circuit of a temperature-compensated display according to claim 1, wherein: Also includes: A DC / DC converter, wherein an input end of the DC / DC converter is connected to the DC power, and an output end is connected to the first end of the capacitor, and is used to convert the DC power into a square wave signal.

5. The contrast control circuit of a temperature-compensated display according to claim 1, wherein: The duty cycle control voltage generator includes: N voltage-dividing resistors, wherein 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 respectively connected to 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, where N is an integer not less than 2.

6. The contrast control circuit of a temperature-compensated display according to claim 5, wherein: The duty cycle control voltage generator further includes: N current-limiting resistors, the first ends of N-1 of the current-limiting resistors are connected one-to-one with 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.

7. The contrast control circuit of a temperature-compensated display according to claim 5, wherein: The duty cycle control voltage generator further 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 second filter modules are grounded.

8. The contrast control circuit of a temperature-compensated display according to claim 5, wherein: The duty cycle control voltage generator further 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 voltage-dividing resistors in 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-compensated display according to any one of claims 1 to 8, wherein: 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 has a collector connected to the first input terminal of the duty cycle control voltage generator, an emitter connected to the first fixed contact of the potentiometer, and is configured 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-compensated display, characterized in that: The device comprises a liquid crystal panel and a contrast control circuit for a temperature-compensated display according to any one of claims 1 to 9, wherein the liquid crystal panel is connected to the contrast control circuit for the temperature-compensated display.

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