Device for providing stable power supply for analog circuit of weighing system

Abstract

The invention relates to the technical field of weighing devices, in particular to a device for providing a stable power supply for a weighing system analog circuit, which comprises a reference power supply input end, an operational amplifier control unit and a power supply output end. The reference power supply input end is connected with an existing high-precision reference power supply in the system, the operational amplifier control unit and the low-temperature drift resistor form a feedback network through the operational amplifier, the reference power supply is converted into a stable output power supply, and finally the power supply output end supplies power to the analog circuit. And target voltages such as + / -2.5 V and the like can be accurately output by adjusting the resistance ratio of the feedback potential-divider network. The high gain characteristic of the operational amplifier is utilized, so that the output voltage stably depends on the reference power supply and the low-temperature drift resistance ratio, and the ultrahigh stability of the same level as the reference is realized.

Description

Technical Field

[0001] This invention belongs to the field of weighing device technology, specifically relating to a device that provides a stable power supply for the analog circuit of a weighing system. Background Technology

[0002] In high-precision weighing systems, the power supply stability of the analog circuit plays a crucial role in measurement accuracy. Traditional designs typically use linear power supply chips for analog circuit power, but these chips have significant temperature drift, resulting in low power supply stability. Continuous power supply voltage fluctuations directly affect the accuracy of high-precision weighing, making it difficult to meet the demands of high-precision measurement.

[0003] Existing patent 1 (publication number: CN110514314B) discloses a low-power, high-precision temperature sensor using CMOS technology. In this design, the independently configured LDO chip has no electrical connection with the system's high-precision reference power supply, and their voltage changes may exhibit asynchronous characteristics. Chips generally have large temperature drift, resulting in low power supply stability. Continuous power supply voltage fluctuations, and this reverse change, can cause the sensor signal to accumulate proportional errors during sampling and quantization. The core flaw of this existing technology lies in its failure to utilize the existing high-precision reference resources in the system, instead relying on a separate power supply chip. This not only increases hardware costs and circuit complexity but also amplifies errors due to the uncoordinated changes in the power supply and reference.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems in the prior art, the present invention provides a device for providing a stable power supply for the analog circuit of a weighing system, which solves the problem that the large temperature drift of the chip causes the low stability of the power supply and the continuous power supply voltage fluctuations affect the accuracy of high-precision weighing.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A device for providing a stable power supply to an analog circuit of a weighing system, comprising: The reference power input terminal is used to connect to the reference power supply in the weighing system to obtain the reference power supply; The operational amplifier control unit is used to obtain a stable output power from the reference power obtained at the reference power input terminal through operational amplifier control. The power output terminal is used to output the output power obtained by the operational amplifier control unit to the analog circuit in the weighing system, so as to provide power to the analog circuit.

[0007] Furthermore, the operational amplifier control unit includes: a control circuit for obtaining a positive power supply and a control circuit for obtaining a negative power supply.

[0008] Furthermore, the control circuit for obtaining a positive power supply includes: a first reference power supply, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a first operational amplifier, a first transistor, a first positive voltage power supply, and a first negative voltage power supply; The first reference power supply is connected to the non-inverting input of the first operational amplifier through a first resistor. The first positive voltage power supply is connected to the positive power supply pin of the first operational amplifier and the collector of the first transistor, respectively. The first negative voltage power supply is connected to the negative power supply pin of the first operational amplifier. The non-inverting input of the first operational amplifier is connected to the first reference power supply through the first resistor, and is also grounded through the series branch of the third and fourth resistors; the inverting input of the first operational amplifier is connected to the output through a feedback network composed of the second resistor, the first capacitor, and the second capacitor, forming negative feedback; the output of the first operational amplifier is connected to the base of the first transistor through the fifth resistor. The base of the first transistor is connected to the output of the first operational amplifier via the fifth resistor, the collector is connected to the first positive voltage power supply, and the emitter is grounded through the third resistor, which also serves as the output node.

[0009] Furthermore, in the negative feedback: the fourth resistor and the second capacitor are connected in series and in parallel with the first capacitor.

[0010] Furthermore, the first reference power supply is the setpoint for closed-loop control, and the output voltage of the control circuit is the controlled variable. The relationship between the output voltage and the setpoint is as follows:

[0011] in, Where A is the output voltage, F is the forward gain, and A is the feedback gain. It serves as the primary reference power source.

[0012] Furthermore, the forward gain A is greater than 10,000 and the feedback gain F is in the range of 0.1 to 1, making AF >> 1.

[0013] Furthermore, the first transistor is an NPN transistor.

[0014] Furthermore, the control circuit for obtaining the negative power supply includes: a second reference power supply, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a fourth capacitor, a fifth capacitor, and a sixth capacitor, a second operational amplifier, a second transistor, a second positive voltage power supply, and a second negative voltage power supply; The second reference power supply is connected to the inverting input of the second operational amplifier through the sixth resistor, the second positive voltage power supply is connected to the positive power supply pin of the second operational amplifier, the second negative voltage power supply is connected to the negative power supply pin of the second operational amplifier, and is also connected to the collector of the second transistor. The non-inverting input of the second operational amplifier is connected to the reference power supply through the sixth resistor, and is also grounded through the series branch of the ninth and seventh resistors. The inverting input of the second operational amplifier is connected to the output through a feedback network consisting of the eighth resistor, the fourth capacitor, and the fifth capacitor, forming negative feedback; the output of the second operational amplifier is connected to the base of the second transistor through the tenth resistor, and the emitter of the second transistor is grounded through the sixth capacitor, which also serves as the output node.

[0015] Furthermore, the second transistor is a PNP type transistor.

[0016] Furthermore, the control circuit for obtaining positive power supply works in conjunction with the control circuit for obtaining negative power supply to provide stable positive and negative power supplies to the operational amplifier circuit, respectively.

[0017] Compared with existing technologies, the device for providing a stable power supply for the analog circuit of a weighing system provided by this invention solves the weighing accuracy error problem caused by the large temperature drift and asynchronous changes of the traditional linear power supply and the low temperature drift resistor by reusing the existing reference power supply in the high-precision weighing system and combining it with a closed-loop control circuit composed of an operational amplifier and a low temperature drift resistor. By utilizing the high gain characteristics of the operational amplifier, the output voltage stability depends on the ratio of the reference power supply and the low temperature drift resistor, achieving ultra-high stability at the same level as the reference, eliminating the "scissors difference" error of independent power supplies, and eliminating the need for additional high-precision reference chips. It provides a flexible, adjustable, low-ripple, and highly anti-interference stable positive and negative power supply for the analog circuit at low cost, ensuring the signal conditioning and sampling accuracy of the high-precision weighing system. Attached Figure Description

[0018] Figure 1 A circuit diagram of a control circuit for obtaining a positive power supply provided in an embodiment of the present invention; Figure 2 The circuit diagram shows the control circuit for obtaining a negative power supply provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] It should be noted that, unless otherwise specifically stated, the relative arrangement and numerical expressions of the components and steps described in these embodiments should not be construed as limiting the scope of the invention.

[0021] The following description of exemplary embodiments is merely illustrative and is not intended to limit the invention or its application or use in any way. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail herein, but where applicable, such techniques, methods, and apparatus should be considered part of this specification.

[0022] The present invention proposes a device for providing a stable power supply for a weighing system analog circuit, which may specifically include: The reference power input terminal is used to connect to the reference power supply in the weighing system to obtain the reference power supply; An operational amplifier control unit is used to obtain a stable output power supply from the reference power supply obtained at the reference power supply input terminal through operational amplifier control; wherein, the unit includes: a control circuit for obtaining a positive power supply and a control circuit for obtaining a negative power supply.

[0023] The power output terminal is used to output the stable output power obtained by the operational amplifier control unit to the analog circuit in the weighing system, so as to provide power to the analog circuit.

[0024] See Figure 1 , Figure 1 The diagram shows the structure of the control circuit for obtaining a positive power supply. V21 is the reference power supply, and VOUT is the output of the power supply constructed using the reference, used for powering the positive terminal of the operational amplifier circuit, etc. This power supply can achieve a stability similar to the reference, powering the analog circuit of the weighing system. Specifically, it includes: First reference power supply V21, first resistor R30, second resistor R33, third resistor R32, fourth resistor R34, fifth resistor R29, first capacitor C16, second capacitor C18, third capacitor C17, first operational amplifier X8, first transistor Q5, first positive voltage power supply P5V, first negative voltage power supply N5V; Power supply connection: The first reference power supply V21 is connected to the non-inverting input of the first operational amplifier X8 through the first resistor R30; the first positive voltage power supply P5V is connected to the positive power supply pin of the first operational amplifier X8 and the collector of the first transistor Q5 respectively; and the first negative voltage power supply N5V is connected to the negative power supply pin of the first operational amplifier X8. Operational amplifier connections: The non-inverting input of the first operational amplifier X8 is connected to the first reference power supply V23 through the first resistor R30, and is also grounded through the series branch of the third resistor R32 and the fourth resistor R34; the inverting input of the first operational amplifier X8 is connected to the output through a feedback network composed of the second resistor R33, the first capacitor C16, and the second capacitor C18, forming negative feedback; the output of the first operational amplifier X8 is connected to the base of the first transistor Q5 through the fifth resistor R29. Transistor connections: The base of the first transistor Q5 is connected to the output of the first operational amplifier X8 via the fifth resistor R29, the collector is connected to the first positive voltage power supply, and the emitter is grounded via the third resistor R32, which also serves as the output node. The first transistor Q5 is an NPN type transistor.

[0025] exist Figure 1 In the circuit, the first reference power supply V21 serves as the setpoint for closed-loop control, and the output voltage VOUT serves as the controlled variable. The two establish a control relationship through a closed-loop feedback system composed of the first operational amplifier X8. According to closed-loop control theory, the output and the setpoint satisfy the following relationship:

[0026] in, For output voltage, It is forward gain. It is feedback gain. V21 is the first reference power supply.

[0027] Since A is very large, typical op-amps can reach 1 million, and some even exceed 10 million. F is the feedback network gain, which is typically above 0.01. The application of this invention is in the range of 0.1 to 1. Because AF is much greater than 1, the formula can be simplified to: making the VOUT expression... = Since V21 is very stable, as long as the resistor F is low temperature drift, the stability of VOUT will be very high.

[0028] The stability of the output voltage VOUT is directly determined by the high-precision reference power supply V21 and the feedback gain F. The temperature drift of the high-precision reference power supply V21 is 2-5 ppm, and F is determined by the resistance ratio of the feedback voltage divider network composed of low-temperature drift resistors, such as R32 and R34. By selecting metal film resistors or foil resistors with a temperature drift coefficient of less than or equal to 5 ppm / ℃, the stability of F can be ensured to match that of the reference power supply, thereby achieving the same level of stability for VOUT as V21.

[0029] To further optimize the temperature drift suppression characteristics, the resistance value of R30 in the feedback network is designed to be equal to the parallel value of R32 and R34. Through the symmetrical design of the resistor network, the common-mode suppression capability of the circuit against temperature changes is improved, and the feedback coefficient drift caused by the inconsistency of resistor temperature drift is avoided.

[0030] Since VOUT and V21 are positively correlated, meaning VOUT changes proportionally with V21, and V21 serves as the reference voltage for the power supply chip while VOUT provides power to the analog circuit, their proportional changes in the same direction can cancel out errors in the signal sampling stage. When temperature or power fluctuations cause V21 and VOUT to change synchronously, the voltage ratio sampled by the power supply chip—such as the ratio of the sensor signal voltage to VOUT, and the ratio to the reference voltage, i.e., the ratio of VOUT to V21—forms error compensation. This avoids the accumulation of sampling and quantization errors caused by the asynchronous changes in the reference power supply of traditional independent LDO power supplies. Traditional independent LDO power supplies may experience a situation where VOUT increases while V21 decreases, leading to error accumulation. This circuit design improves the measurement accuracy of the weighing system from both the power supply and signal ends.

[0031] Additionally, see Figure 2 This invention also provides a structural diagram of a control circuit for obtaining a negative power supply, a circuit for outputting a negative voltage. Compared with a positive voltage output, the difference lies in that the NPN transistor is replaced with a PNP transistor, and the reference is changed from a positive input pin to a negative input pin. Specifically, it includes: The components are: second reference power supply V24, sixth resistor R36, seventh resistor R38, eighth resistor R37, ninth resistor R35, tenth resistor R31, fourth capacitor C21, fifth capacitor C19, and sixth capacitor C20; second operational amplifier X9; second transistor Q7; second positive voltage power supply P5V; and second negative voltage power supply N5V. The specific structures of these components are as follows: Power supply connections: The second reference power supply V24 is connected to the inverting input of the second operational amplifier X9 through the sixth resistor R36; the second positive voltage power supply P5V is connected to the positive power supply pin of the second operational amplifier X9; and the second negative voltage power supply N5V is connected to the negative power supply pin of the second operational amplifier X9, and is also connected to the collector of the second transistor Q7. Operational amplifier input circuit: The non-inverting input terminal of the second operational amplifier X9 is connected to the reference power supply through the sixth resistor R36, and is also grounded through the series branch of the ninth resistor R35 and the seventh resistor R38.

[0032] Operational amplifier feedback loop: The inverting input of the second operational amplifier X9 is connected to the output through a feedback network consisting of the eighth resistor R37, the fourth capacitor C21, and the fifth capacitor C19, forming negative feedback. The output of the second operational amplifier X9 is connected to the base of the second transistor Q7 through the tenth resistor R31. The emitter of the second transistor Q7 is grounded through the sixth capacitor C20, which also serves as the output node. The second transistor Q7 is a PNP transistor, the fourth capacitor C21 has a capacitance of 100pF, and the fifth capacitor C19 has a capacitance of 4.7nF.

[0033] Regarding circuit parameter configuration, the required output voltage can be flexibly constructed by adjusting the resistance ratio of R32 and R34 in the feedback voltage divider network. Taking a high-precision ADC chip as an example, in addition to the reference power supply, it usually requires a stable ±2.5V power supply for analog circuit operation. Through the above-mentioned resistor ratio adjustment mechanism, the target voltage such as +2.5V can be accurately output to meet the high-precision power supply requirements.

[0034] Referring to Table 1, the minimum fluctuation of the LDO is 952 in the last three digits, and the maximum fluctuation is 972 in the last three digits, with a fluctuation of 20uV; the minimum power supply of the present invention is 246, the maximum is 256, and the fluctuation is 10uV, which significantly reduces voltage fluctuation.

[0035] Table 1

[0036] In summary, based on the collaborative design of the positive and negative power supply control circuits, this invention provides symmetrical and stable positive and negative power supplies for high-precision operational amplifier circuits, effectively improving the stability of the operational amplifier output signal. Directly addressing the power supply requirements of analog circuits in high-precision weighing systems, it reduces interference factors such as temperature drift and voltage fluctuations at the power supply end, demonstrating significant practical value in improving the overall measurement accuracy of the weighing system. Simultaneously, it constructs a high-quality power output scheme that differs from traditional reference voltages by utilizing a high-precision reference and operational amplifier units. In high-precision measurement scenarios, the high-precision reference is already an inherent configuration of the system as part of power supply chips and other devices. This invention does not require additional hardware costs; it only expands the functionality of the existing high-precision reference through circuit design, fully leveraging its performance advantages. The market price of high-precision references ranges from tens to thousands of yuan; this invention maximizes the potential of these high-value devices through a reuse strategy.

[0037] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for providing a stable power supply to a weighing system analog circuit, characterized in that, include: The reference power input terminal is used to connect to the reference power supply in the weighing system to obtain the reference power supply; The operational amplifier control unit is used to obtain a stable output power from the reference power obtained at the reference power input terminal through operational amplifier control. The power output terminal is used to output the output power obtained by the operational amplifier control unit to the analog circuit in the weighing system, so as to provide power to the analog circuit.

2. The device for providing a stable power supply to the analog circuit of a weighing system according to claim 1, characterized in that, The operational amplifier control unit includes: a control circuit for obtaining a positive power supply and a control circuit for obtaining a negative power supply.

3. The device for providing a stable power supply to the analog circuit of a weighing system according to claim 2, characterized in that, The control circuit for obtaining a positive power supply includes: a first reference power supply, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a first operational amplifier, a first transistor, a first positive voltage power supply, and a first negative voltage power supply; The first reference power supply is connected to the non-inverting input of the first operational amplifier through a first resistor. The first positive voltage power supply is connected to the positive power supply pin of the first operational amplifier and the collector of the first transistor, respectively. The first negative voltage power supply is connected to the negative power supply pin of the first operational amplifier. The non-inverting input of the first operational amplifier is connected to the first reference power supply through the first resistor, and is also grounded through the series branch of the third and fourth resistors; the inverting input of the first operational amplifier is connected to the output through a feedback network composed of the second resistor, the first capacitor, and the second capacitor, forming negative feedback; the output of the first operational amplifier is connected to the base of the first transistor through the fifth resistor. The base of the first transistor is connected to the output of the first operational amplifier via the fifth resistor, the collector is connected to the first positive voltage power supply, and the emitter is grounded through the third resistor, which also serves as the output node.

4. The device for providing a stable power supply to the analog circuit of a weighing system according to claim 3, characterized in that, In the negative feedback: the fourth resistor and the second capacitor are connected in series and in parallel with the first capacitor.

5. The device for providing a stable power supply to the analog circuit of a weighing system according to claim 3, characterized in that, The first reference power supply is the setpoint for closed-loop control, and the output voltage of the control circuit is the controlled variable. The relationship between the output voltage and the setpoint is as follows: in, Where A is the output voltage, F is the forward gain, and A is the feedback gain. It serves as the primary reference power source.

6. The apparatus for providing a stable power supply to the analog circuit of a weighing system according to claim 5, characterized in that, The forward gain A is greater than 10,000, and the feedback gain F is in the range of 0.1 to 1, which makes AF >> 1.

7. The device for providing a stable power supply to the analog circuit of a weighing system according to claim 3, characterized in that, The first transistor is an NPN transistor.

8. The apparatus for providing a stable power supply to the analog circuit of a weighing system according to claim 2, characterized in that, The control circuit for obtaining the negative power supply includes: a second reference power supply, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a fourth capacitor, a fifth capacitor, and a sixth capacitor, a second operational amplifier, a second transistor, a second positive voltage power supply, and a second negative voltage power supply; The second reference power supply is connected to the inverting input of the second operational amplifier through the sixth resistor, the second positive voltage power supply is connected to the positive power supply pin of the second operational amplifier, the second negative voltage power supply is connected to the negative power supply pin of the second operational amplifier, and is also connected to the collector of the second transistor. The non-inverting input of the second operational amplifier is connected to the reference power supply through the sixth resistor, and is also grounded through the series branch of the ninth and seventh resistors. The inverting input of the second operational amplifier is connected to the output through a feedback network consisting of the eighth resistor, the fourth capacitor, and the fifth capacitor, forming negative feedback; the output of the second operational amplifier is connected to the base of the second transistor through the tenth resistor, and the emitter of the second transistor is grounded through the sixth capacitor, which also serves as the output node.

9. The apparatus for providing a stable power supply to the analog circuit of a weighing system according to claim 8, characterized in that, The second transistor is a PNP type transistor.

10. The apparatus for providing a stable power supply to the analog circuit of a weighing system according to claim 2, characterized in that, The control circuit for obtaining positive power and the control circuit for obtaining negative power work together to provide stable positive and negative power supplies to the operational amplifier circuit, respectively.

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