An operational amplifier positive and negative pressure expansion circuit

Abstract

The utility model discloses a kind of positive and negative pressure expansion circuit of operational amplifier, comprising: operational amplifier U1, operational amplifier U1 including same phase input end, inverting input end and first output end.Signal input circuit, signal input circuit is connected with same phase input end, for generating target voltage signal Vdac.Push-pull output circuit, push-pull output circuit includes input end, second output end and third output end, input end is connected with first output end, second output end and third output end are connected output end VOUT, for outputing symmetrical positive voltage or negative voltage.Feedback circuit, feedback circuit is connected with inverting input end and output end VOUT respectively, for the voltage signal of output end VOUT is fed back to inverting input end, forms closed loop gain stabilization system.The scheme is through the combination of precision operational amplifier closed loop control and push-pull power expansion, while maintaining the high-precision characteristics of operational amplifier, break through its output current limit, material cost is reduced compared with single large current operational amplifier.

Description

Technical Field

[0001] This utility model relates to the field of liquid crystal display driving technology, specifically to an operational amplifier positive and negative voltage current amplification circuit. Background Technology

[0002] VCOM voltage is the reference voltage for the deflection of liquid crystal molecules. The voltage difference between VCOM and Gamma voltage determines the deflection angle of the liquid crystal molecules, thus affecting grayscale and color performance. Positive and negative voltage current outputs ensure consistent positive and negative period voltage differences, avoiding image jitter or grayscale shift problems caused by voltage fluctuations. The VCOM voltage needs to be dynamically adjusted for different brightness levels, temperatures, or signal frequencies.

[0003] In existing technologies, VCOM driver circuits rely on high-precision, high-current operational amplifiers for direct output. However, this approach has the following drawbacks: High cost: The unit price of a high-current op-amp exceeds 50 yuan, and additional heat dissipation design is required. Low efficiency: The op-amp has high static power consumption (>80mW) and significant temperature rise (ΔT≥40℃) in linear operating mode. Limited driving capability: The output current of a single op-amp is typically ≤0.5A, making it difficult to adapt to the requirements of high-resolution screens. Utility Model Content

[0004] To overcome the above-mentioned shortcomings, the purpose of this utility model is to provide an operational amplifier positive and negative voltage current amplification circuit to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is an operational amplifier positive and negative voltage current amplification circuit, comprising: Operational amplifier U1, wherein operational amplifier U1 includes a non-inverting input terminal, an inverting input terminal, and a first output terminal; A signal input circuit, connected to the non-inverting input terminal, is used to generate a target voltage signal Vdac; A push-pull output circuit includes an input terminal, a second output terminal, and a third output terminal. The input terminal is connected to the first output terminal, and the second and third output terminals are connected to a common output terminal VOUT, which is used to output a symmetrical positive or negative voltage. A feedback circuit is connected to both the inverting input terminal and the output terminal VOUT, and is used to feed back the voltage signal of the output terminal VOUT to the inverting input terminal to form a closed-loop gain stabilization system.

[0006] This invention provides an operational amplifier (op-amp) positive and negative voltage amplification circuit. Through a push-pull output circuit design, it can output symmetrical positive or negative voltages, meeting the needs of various applications requiring positive and negative voltage outputs. The feedback circuit design allows the voltage signal at the output terminal VOUT to be fed back to the inverting input terminal, forming a closed-loop gain stabilization system. This solution, through an innovative combination of precision op-amp closed-loop control and push-pull power expansion, overcomes the output current limitation while maintaining the high precision characteristics of the op-amp. It also features high linearity, high efficiency, wide bandwidth, and strong robustness, while reducing material costs compared to a single high-current op-amp, providing a cost-effective solution for LCD display drivers.

[0007] In some embodiments, the push-pull output circuit includes a first transistor Q1 and a second transistor Q2. The base of the first transistor Q1 is connected to the first output terminal, the collector is connected to the positive power supply Vdd, and the emitter is the second output terminal, which is connected to the output terminal VOUT. The base of the second transistor Q2 is connected to the first output terminal, the collector is connected to the negative power supply Vss, and the emitter is the third output terminal, which is connected to the output terminal VOUT.

[0008] Using the above technical solution, the two transistors in the push-pull output circuit can work alternately. The first transistor Q1 is turned on only when a positive voltage is needed, and the second transistor Q2 is turned on when a negative voltage is needed. Compared with a single transistor or a single-ended output circuit, the push-pull output circuit can provide a larger output current and drive a larger current load by having the two transistors work alternately.

[0009] In some embodiments, the feedback circuit includes a first resistor R1, a second resistor R2, and a third resistor R3. One end of the third resistor R3 is connected to the inverting input terminal, and the other end is grounded. One end of the first resistor R1 and one end of the second resistor R2 are both connected to the node between the third resistor R3 and the operational amplifier U1. The other end of the second resistor R2 is connected to the output terminal VOUT.

[0010] Using the above technical solution, the feedback circuit feeds back the voltage signal at the output terminal VOUT to the inverting input terminal of the operational amplifier through the voltage division effect of the first resistor R1, the second resistor R2, and the third resistor R3. By selecting appropriate resistor values, the closed-loop gain can be precisely set, ensuring that the ratio between the output voltage and the input signal meets the design requirements. Closed-loop negative feedback can automatically correct output voltage deviations caused by power supply voltage fluctuations or load changes, improving output voltage stability and enhancing the dynamic performance of the circuit.

[0011] In some embodiments, the signal input circuit includes an MCU processor, a DAC chip, and a fourth resistor R4. The DAC chip is connected in series with the fourth resistor R4 and connected to the non-inverting input terminal of the operational amplifier U1. The MCU processor is signal-connected to the DAC chip.

[0012] Using the above technical solution, the MCU can dynamically adjust the output of the DAC chip based on real-time data or user input, realizing real-time control of the operational amplifier input signal and generating complex signal waveforms (such as sine waves, square waves, triangle waves, etc.) to meet various complex application requirements. The combination of the DAC chip and resistor R4 can effectively filter out high-frequency noise, reduce the impact of noise on the signal, and improve the purity of the signal.

[0013] In some embodiments, the operational amplifier positive and negative voltage amplification circuit further includes a reference voltage source connected to the other end of the first resistor R1, for providing a reference voltage Vref to the operational amplifier.

[0014] By employing the above technical solution, the reference voltage source can provide a high-precision reference voltage, thereby ensuring a more accurate output voltage for the operational amplifier and reducing output deviations caused by power supply fluctuations or temperature changes. Furthermore, the fast response characteristics of the reference voltage source enable the feedback circuit to more quickly correct the output voltage, reducing output voltage overshoot and oscillation, and improving the dynamic performance of the circuit.

[0015] In some embodiments, the operational amplifier positive and negative voltage amplification circuit further includes a discharge circuit, which includes a fifth resistor RL, one end of which is connected to the output terminal VOUT, and the other end is grounded.

[0016] Using the above technical solution, the discharge circuit provides a discharge path for the output terminal VOUT through the fifth resistor RL, so that the charge at the output terminal can be released quickly, which is used to provide a discharge path for the liquid crystal layer when the liquid crystal display is turned off.

[0017] In some implementations, the first transistor Q1 is an NPN transistor, and the second transistor Q2 is a PNP transistor.

[0018] Using the above technical solution, only the NPN transistor is turned on when the output voltage is positive; when the output voltage is negative, only the PNP transistor is turned on. That is, the NPN transistor (Q1) is used for positive voltage output, and the PNP transistor (Q2) is used for negative voltage output. The two transistors are turned on and off respectively to provide symmetrical positive and negative voltage output. The symmetrical output capability can reduce the power loss caused by voltage asymmetry and improve the overall efficiency of the circuit.

[0019] In some implementations, the DAC chip is designated DAC80508 and communicates with the MCU via an SPI interface.

[0020] Using the above technical solution, the DAC80508 supports high-resolution digital input and can generate extremely accurate analog signals. At the same time, the chip typically has low noise and high linearity characteristics, which can reduce signal distortion and improve signal quality. Its SPI interface supports high-speed data transmission, which can quickly send digital signals to the DAC chip and reduce signal delay.

[0021] In some embodiments, the operational amplifier is designated as OPA2197.

[0022] By adopting the above technical solution, the OPA2197 has extremely low voltage noise, current noise, and high-precision gain and linearity, which can significantly reduce noise components in the signal, improve signal purity, and ensure the accuracy and consistency of the output signal, while reducing signal distortion caused by operational amplifier characteristics.

[0023] In some embodiments, the reference voltage source is model TPR6040F40-S3TR-S, and its reference voltage is 4.096V.

[0024] Using the above technical solution, the TPR6040F40-S3TR-S can provide a precise 4.096V reference voltage and has low noise characteristics, which can reduce noise in the feedback circuit, thereby reducing the noise component in the output voltage and improving the purity of the output signal. Attached Figure Description

[0025] Figure 1 This is a circuit diagram of an embodiment of an operational amplifier positive and negative voltage current amplification circuit according to the present invention. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the scope of protection of the present invention.

[0027] refer to Figure 1 , Figure 1 The diagram shows a circuit diagram of an operational amplifier positive and negative voltage current amplification circuit provided in an embodiment of the present invention.

[0028] like Figure 1 As shown, the technical solution provided in this application is an operational amplifier positive and negative voltage current amplification circuit, including: Operational amplifier U1 includes a non-inverting input terminal, an inverting input terminal, and a first output terminal.

[0029] The signal input circuit is connected to the non-inverting input terminal and is used to generate the target voltage signal Vdac.

[0030] The push-pull output circuit includes an input terminal, a second output terminal, and a third output terminal. The input terminal is connected to the first output terminal, and the second and third output terminals are connected to the common output terminal VOUT, which is used to output symmetrical positive or negative voltages.

[0031] The feedback circuit is connected to both the inverting input and the output VOUT, and is used to feed back the voltage signal of the output VOUT to the inverting input to form a closed-loop gain-stabilized system.

[0032] This invention provides an operational amplifier (op-amp) positive and negative voltage amplification circuit. Through a push-pull output circuit design, it can output symmetrical positive or negative voltages, meeting the needs of various applications requiring positive and negative voltage outputs. The feedback circuit design allows the voltage signal at the output terminal VOUT to be fed back to the inverting input terminal, forming a closed-loop gain stabilization system. This solution, through a combination of precision op-amp closed-loop control and push-pull power expansion, overcomes the output current limitation while maintaining the high precision characteristics of the op-amp. It also features high linearity, high efficiency, wide bandwidth, and strong robustness, while reducing material costs compared to a single high-current op-amp, providing a cost-effective solution for LCD display drivers.

[0033] In some embodiments, reference Figure 1 The push-pull output circuit includes a first transistor Q1 and a second transistor Q2. The base of the first transistor Q1 is connected to the first output terminal, the collector is connected to the positive power supply Vdd, and the emitter is the second output terminal, which is connected to the output terminal VOUT. The base of the second transistor Q2 is connected to the first output terminal, the collector is connected to the negative power supply Vss, and the emitter is the third output terminal, which is connected to the output terminal VOUT.

[0034] For example, in a push-pull output circuit, the two transistors can operate alternately. The first transistor Q1 conducts only when a positive output voltage is needed, and the second transistor Q2 conducts only when a negative output voltage is needed. Compared to a single transistor or a single-ended output circuit, the push-pull output circuit can provide a larger output current and drive a larger current load by having two transistors operate alternately. The push-pull structure only conducts a single transistor during half a signal cycle, improving both output capability and current amplification capability. Static power consumption is reduced to 10-20mA, and system efficiency reaches 85%-89%, which is superior to traditional single-ended circuits.

[0035] In some embodiments, reference Figure 1The feedback circuit includes a first resistor R1, a second resistor R2, and a third resistor R3. One end of the third resistor R3 is connected to the inverting input terminal, and the other end is grounded. One end of the first resistor R1 and one end of the second resistor R2 are both connected to the node between the third resistor R3 and the operational amplifier U1. The other end of the second resistor R2 is connected to the output terminal VOUT.

[0036] For example, the feedback circuit uses the voltage divider effect of the first resistor R1, the second resistor R2, and the third resistor R3 to feed back the voltage signal at the output terminal VOUT to the inverting input terminal of the operational amplifier. By selecting appropriate resistor values, the closed-loop gain can be precisely set to ensure that the ratio between the output voltage and the input signal meets the design requirements. Closed-loop negative feedback can automatically correct output voltage deviations caused by power supply voltage fluctuations or load changes, suppress input noise and interference signals, improve the signal-to-noise ratio, reduce output power supply ripple, improve output voltage stability, and enhance the dynamic performance of the circuit.

[0037] In some embodiments, reference Figure 1 The signal input circuit includes an MCU processor, a DAC chip, and a fourth resistor R4. The DAC chip is connected in series with the fourth resistor R4 and connected to the non-inverting input terminal of the operational amplifier U1. The MCU processor is connected to the DAC chip for signal connection.

[0038] For example, the MCU can dynamically adjust the output of the DAC chip based on real-time data or user input, thereby achieving real-time control of the operational amplifier input signal and generating complex signal waveforms (such as sine waves, square waves, triangle waves, etc.) to meet various complex application requirements. The combination of the DAC chip and resistor R4 can effectively filter out high-frequency noise, reduce the impact of noise on the signal, and improve the purity of the signal.

[0039] In some embodiments, reference Figure 1 The operational amplifier positive and negative voltage amplification circuit also includes a reference voltage source, which is connected to the other end of the first resistor R1 to provide a reference voltage Vref for the operational amplifier.

[0040] For example, a reference voltage source can provide a high-precision reference voltage, thereby ensuring a more accurate output voltage for the operational amplifier, reducing output deviations caused by power supply fluctuations or temperature changes, and improving noise immunity and accuracy. Furthermore, the fast response characteristics of the reference voltage source allow the feedback circuit to correct the output voltage more quickly, reducing output voltage overshoot and oscillation, and improving the circuit's dynamic performance.

[0041] In some embodiments, reference Figure 1 The operational amplifier positive and negative voltage amplification circuit also includes a discharge circuit, which includes a fifth resistor RL. One end of the fifth resistor RL is connected to the output terminal VOUT, and the other end is grounded.

[0042] For example, the discharge circuit provides a discharge path for the output terminal VOUT through the fifth resistor RL, so that the charge at the output terminal can be released quickly, which is used to provide a discharge path for the liquid crystal layer when the liquid crystal display is turned off.

[0043] In some embodiments, reference Figure 1 The first transistor Q1 is an NPN transistor, and the second transistor Q2 is a PNP transistor.

[0044] For example, when outputting a positive voltage, only the NPN transistor is turned on. When outputting a negative voltage, only the PNP transistor is turned on. That is, the NPN transistor (Q1) is used for positive voltage output, and the PNP transistor (Q2) is used for negative voltage output. One is turned on and the other is turned off to provide symmetrical positive and negative voltage output. The symmetrical output capability can reduce power loss caused by voltage asymmetry and improve the overall efficiency of the circuit.

[0045] In some embodiments, reference Figure 1 The DAC chip is model DAC80508, which communicates with the MCU via the SPI interface.

[0046] For example, the DAC80508 supports high-resolution digital input and can generate extremely accurate analog signals. At the same time, the chip typically has low noise and high linearity characteristics, which can reduce signal distortion and improve signal quality. Its SPI interface supports high-speed data transmission, which can quickly send digital signals to the DAC chip and reduce signal delay.

[0047] In some embodiments, reference Figure 1 The operational amplifier model is OPA2197.

[0048] For example, the OPA2197 features extremely low voltage noise, current noise, and high-precision gain and linearity, which can significantly reduce noise components in the signal, improve signal purity, and ensure the accuracy and consistency of the output signal, while reducing signal distortion caused by the characteristics of the op-amp.

[0049] In some embodiments, reference Figure 1 The reference voltage source is model TPR6040F40-S3TR-S, and its reference voltage is 4.096V.

[0050] For example, the TPR6040F40-S3TR-S can provide an accurate 4.096V reference voltage and has low noise characteristics, which can reduce noise in the feedback circuit, thereby reducing the noise component in the output voltage and improving the purity of the output signal.

[0051] The following is a specific embodiment of an operational amplifier positive and negative voltage current amplification circuit provided in this application: 1. Design a VCOM output circuit controlled by an MCU, outputting -12V to 12V and driving a load RL. The output current capability should be ≥1A and the linearity error <1%.

[0052] 2. Circuit design and selection: DAC chip: DAC80508 (16-bit, SPI, 0~2.5V); Operational amplifier: OPA2197 (dual precision op-amp, low noise, 10MHz bandwidth); The first resistor R1 = 20K, the second resistor R2 = 59K, the third resistor R3 = 10K, and the fourth resistor R4 = 2K. Reference voltage source chip: TPR6040F40-S3TR-S (reference voltage is 4.096V) NPN transistor: TIP35C; PNP transistor: TIP36C; Substitute into the formula: Conclusion: The working principle of the operational amplifier positive and negative voltage current amplification circuit provided in this application is as follows: When the operational amplifier is in normal working condition, the analog signal Vin, which is lower than the operational amplifier supply voltage, is input to the non-inverting input of operational amplifier U1. The output terminals of the operational amplifier are respectively connected to the base of the first transistor Q1 and the base of the second transistor Q2. The collector of the first transistor Q1 is connected to the positive power supply Vdd, and the collector of the second transistor Q2 is connected to the negative power supply Vss. The emitters of the first transistor Q1 and the second transistor Q2 are connected in parallel to the fifth resistor RL. The first resistor R1, the second resistor R2 and the third resistor R3 form a closed-loop feedback for the operational amplifier current amplification. When the input signal Vin is positive, a closed-loop feedback loop for current amplification of the op-amp is formed: the op-amp outputs a positive signal, and the base of the NPN transistor Q1 receives a positive bias current and turns on. Its equivalent on-resistance is controlled by the magnitude of Vin, while transistor Q2 turns off because its base receives a forward current. Similarly, when Vin is negative, the op-amp outputs a negative signal, and the base of the second transistor Q2 receives a reverse current and turns on, while the first transistor Q1 turns off. Since the negative feedback point of the op-amp is the emitter of the first transistor Q1 and the second transistor Q2, the output voltage of the transistors is always proportional to Vin, and the output current is greatly increased through the current amplification of the transistors, thus achieving the purpose of amplifying the op-amp output.

[0053] The above embodiments are only for illustrating the technical concept and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it. They cannot be used to limit the protection scope of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the protection scope of this utility model.

Claims

1. An operational amplifier positive and negative voltage current amplification circuit, characterized in that, include: Operational amplifier U1, wherein operational amplifier U1 includes a non-inverting input terminal, an inverting input terminal, and a first output terminal; A signal input circuit, connected to the non-inverting input terminal, is used to generate a target voltage signal Vdac; A push-pull output circuit includes an input terminal, a second output terminal, and a third output terminal. The input terminal is connected to the first output terminal, and the second and third output terminals are connected to a common output terminal VOUT, which is used to output a symmetrical positive or negative voltage. A feedback circuit is connected to the inverting input terminal and the output terminal VOUT respectively, and is used to feed back the voltage signal of the output terminal VOUT to the inverting input terminal to form a closed-loop gain stabilization system. The push-pull output circuit includes a first transistor Q1 and a second transistor Q2. The base of the first transistor Q1 is connected to the first output terminal, the collector is connected to the positive power supply Vdd, and the emitter is the second output terminal, which is connected to the output terminal VOUT. The base of the second transistor Q2 is connected to the first output terminal, the collector is connected to the negative power supply Vss, and the emitter is the third output terminal, which is connected to the output terminal VOUT. The feedback circuit includes a first resistor R1, a second resistor R2, and a third resistor R3. One end of the third resistor R3 is connected to the inverting input terminal, and the other end is grounded. One end of the first resistor R1 and one end of the second resistor R2 are both connected to the node between the third resistor R3 and the operational amplifier U1. The other end of the second resistor R2 is connected to the output terminal VOUT. The signal input circuit includes an MCU processor, a DAC chip, and a fourth resistor R4. The DAC chip is connected in series with the fourth resistor R4 and connected to the non-inverting input terminal of the operational amplifier U1. The MCU processor is signal-connected to the DAC chip.

2. The operational amplifier positive and negative voltage current amplification circuit according to claim 1, characterized in that, It also includes a reference voltage source, which is connected to the other end of the first resistor R1 to provide a reference voltage Vref for the operational amplifier.

3. The operational amplifier positive and negative voltage current amplification circuit according to claim 1, characterized in that, It also includes a discharge circuit, which includes a fifth resistor RL, one end of which is connected to the output terminal VOUT, and the other end is grounded.

4. The operational amplifier positive and negative voltage current amplification circuit according to claim 1, characterized in that, The first transistor Q1 is an NPN transistor, and the second transistor Q2 is a PNP transistor.

5. The operational amplifier positive and negative voltage current amplification circuit according to claim 1, characterized in that, The DAC chip is model DAC80508, and it communicates with the MCU via an SPI interface.

6. The operational amplifier positive and negative voltage current amplification circuit according to claim 1, characterized in that, The operational amplifier is model OPA2197.

7. The operational amplifier positive and negative voltage current amplification circuit according to claim 2, characterized in that, The reference voltage source is model TPR6040F40-S3TR-S, and its reference voltage is 4.096V.

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