Dual-reference synthesized voltage generation circuit

Abstract

This invention relates to a dual-reference synthesized voltage generation circuit, comprising: a first reference source circuit and a second reference source circuit; a PWM circuit, including an analog switch and an isolation chip, wherein the analog switch is connected to the output terminal of the second reference source circuit and the isolation chip respectively; a digital control circuit, connected to the isolation chip via the digital control chip; a filter circuit, connected to the analog switch; an integral feedback circuit, connected to the filter module; a buffer amplifier circuit, connected to the output terminals of the second reference source circuit and the integral feedback circuit; and a protection circuit, with its input terminal connected to the first reference source circuit and the buffer amplifier circuit, and its output terminal connected to the integral feedback circuit. This invention employs a dual-reference voltage synthesis approach, reducing dependence on precision resistors and temperature, minimizing changes in the reference chip output caused by temperature variations, and simultaneously reducing high-frequency noise introduced by PWM modulation.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic metrology technology, specifically to a dual-reference synthesized voltage generation circuit. Background Technology

[0002] DC voltage standards are the most important basic parameters in electromagnetic metrology, directly affecting AC voltage, DC current, and AC current. To ensure the accuracy and stability of equipment, highly stable voltage standards are required for calibration and value transfer. Currently, China mainly uses foreign-developed solid-state voltage references as the main standard for DC voltage measurement, which suffers from problems such as technological monopoly and high prices, while mature domestic products are not yet available.

[0003] Figure 1 This is a typical schematic diagram of a solid-state voltage reference. The scheme can be divided into a standard voltage generation circuit, a buck circuit, and a power supply circuit. The power supply circuit powers the entire device and can be powered by 220V or a battery. The standard voltage generation circuit includes a reference source circuit and a boost circuit, mainly used to generate a stable standard 10V voltage; its quality directly affects the output voltage quality. The buck circuit reduces the output standard 10V voltage and compares it with the reference voltage generated by the reference source circuit, achieving closed-loop control to obtain a stable standard 10V voltage.

[0004] However, existing solutions are quite sensitive to temperature. Temperature affects the stability of the reference chip output and the resistance value of the precision resistors used in the boost circuit, thus affecting the stability of the final output. For example, Wang Gang, Lan Jiang et al.'s "A Highly Stable Continuously Adjustable DC Voltage Source with Pulse Width Modulation" (Journal of Metrology, 2014, VOL35, No2, P169-P172) mentions that "the key component of the DC constant voltage reference circuit is the voltage reference chip... In order to minimize the impact of contact thermoelectric potential on the output, proper heat preservation is necessary," but does not mention specific treatment methods; Liu Xin, Han Bing et al.'s "A Temperature Control Circuit for Improving the Stability of DC Voltage Sources" (Metrology Technology, 2016, No2, P6-P9) uses... The design of a temperature control circuit ensures the temperature stability of the reference chip's operating environment, but this increases the overall size and power consumption of the device. Zhao Haiying et al.'s "DC Solid-State Voltage Standard Device" (CN20151018992.7) only improved the device's appearance without modifying the circuitry. Cai Ying et al.'s "Development of a New Solid-State Voltage Standard" (Aerospace Measurement Technology 2000, VOL20, No.3, P58-P62) also uses a constant-temperature bath design. These solutions all rely heavily on high-stability resistors. Furthermore, similar foreign products also depend on constant-temperature systems to ensure stable performance, resulting in large size, high power consumption, bulkiness, and difficulties in transportation.

[0005] In solid-state voltage references, the standard voltage generation circuit is the most critical part, and the stability of its output directly affects the stability of the system output. Therefore, it is urgent to improve the standard voltage generation circuit to reduce its dependence on precision resistors and temperature. Summary of the Invention

[0006] This invention primarily improves the standard voltage generation circuit by reducing its dependence on precision resistors and temperature, thereby lowering the high-frequency noise of the output and enhancing the output stability and environmental adaptability of the solid-state voltage reference.

[0007] To achieve the above-mentioned objectives of this invention, an embodiment of this invention provides a dual-reference synthesized voltage generation circuit, comprising: a first reference source circuit and a second reference source circuit; a PWM circuit, including an analog switch and an isolation chip, wherein the analog switch is connected to the output terminal of the second reference source circuit and the isolation chip respectively; a digital control circuit, connected to the isolation chip via the digital control chip; a filter circuit, connected to the analog switch; an integral feedback circuit, connected to the filter module; a buffer amplifier circuit, connected to the output terminal of the second reference source circuit and also connected to the integral feedback circuit; and a protection circuit, whose input terminal is connected to the first reference source circuit and the buffer amplifier circuit, and whose output terminal is connected to the integral feedback circuit.

[0008] In a preferred embodiment of the present invention, the first reference source circuit outputs a negative reference voltage, the second reference source circuit outputs a positive reference voltage, and the two voltages are finally combined to form the output voltage of the dual reference combined voltage generating circuit.

[0009] In a preferred embodiment of the present invention, the output positive voltage signal is used as a feedback signal, and closed-loop control is performed with the integral feedback circuit to condition the positive voltage signal in the buffer amplifier circuit to achieve a high-stability output of the positive voltage signal.

[0010] In a preferred embodiment of the present invention, the output terminal of the second reference voltage is also connected to the non-inverting and inverting terminals of the buffer amplifier circuit through a voltage divider resistor.

[0011] In a preferred embodiment of the present invention, the first reference source circuit outputs a -7.2V reference voltage, which is regulated by the operational amplifier of the protection circuit to a -7.2V reference voltage. The second reference source circuit outputs a 7.2V reference voltage, which is converted to a 2.8V voltage by the PWM circuit. The voltage values ​​input to the non-inverting and inverting inputs of the integral feedback circuit are then compared to form a closed loop. When the voltage value input to the inverting input of the integral feedback circuit changes and deviates from the balance, the change in the output of the integral feedback circuit is fed into the non-inverting input of the buffer amplifier circuit through the voltage divider resistor. This change is then added or subtracted from the 7.2V reference voltage output by the second reference source circuit, which is fed into the buffer amplifier circuit through the voltage divider resistor, according to the predetermined weight of the voltage divider resistor. The output value is adjusted until the target voltage value of 2.8V is output, thus completing the closed-loop control. The two voltages are combined into a 10V reference voltage output after the protection circuit.

[0012] In a preferred embodiment of the present invention, the PWM circuit is treated with equipotential shielding.

[0013] In a preferred embodiment of the present invention, the filtering circuit employs a drift-free, all-pole active filter.

[0014] This invention proposes a dual-reference chip synthesis technology by improving the standard voltage generation circuit, and develops a voltage reference device based on this, thereby reducing its dependence on precision resistors and temperature, reducing the large high-frequency noise generated by PWM modulation, and thus improving the output stability and environmental adaptability of the solid-state voltage reference. The main advantages are as follows: (1) The boost circuit designed with precision resistors is eliminated, reducing the dependence on precision resistors and reducing the output changes caused by precision resistor drift; (2) Through positive and negative reference compensation, the temperature coefficient can be reduced to within 0.05PPM / ℃, which is beneficial to production and greatly reduces the difficulty of adjusting the temperature coefficient of the solid-state voltage reference; (3) It is easy to control the noise of the solid-state voltage reference. The final output of this scheme is a -7.2V output directly from the reference chip and a 2.8V synthesized by the PWM DAC. The -7.2V is the noise of the Zener diode itself, which is low. After being synthesized with the 2.8V modulated by the PWM DAC, it can effectively suppress the noise brought by the PWM DAC. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram illustrating the development principle of a solid-state voltage reference;

[0017] Figure 2 This is a schematic diagram of the dual-reference synthesized voltage generation circuit according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures:

[0019] First reference source circuit 1, second reference source circuit 2, PWM circuit 3, analog switch 4, isolation chip 5, digital control circuit 6, filter circuit 7, integral feedback circuit 8, buffer amplifier circuit 9, protection circuit 10, voltage divider resistor 11. Detailed Implementation

[0020] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0021] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0022] like Figure 2The diagram shows a dual-reference synthesized voltage generation circuit according to an embodiment of the present invention, comprising: a first reference source circuit 1, a second reference source circuit 2, a PWM circuit 3, a digital control circuit 6, a filter circuit 7, an integral feedback circuit 8, a buffer amplifier circuit 9, and a protection circuit 10. The PWM circuit 3 includes an analog switch 4 and an isolation chip 5. The first reference source circuit 1 outputs a reference voltage of -7.2V, which, after being regulated by an operational amplifier (not shown in the diagram, but located in the protection circuit 10), outputs a reference voltage of -7.2V. The second reference source circuit 2 outputs a 7.2V reference voltage, which is then output as 2.8V through the PWM circuit 3. This 2V is then compared with the voltage values ​​input to the non-inverting and inverting inputs of the integral feedback circuit 8, forming a closed-loop circuit. When the voltage value input to the inverting input of the integral feedback circuit 8 changes and deviates from balance, the change in the output of the integral feedback circuit 8 is fed into the non-inverting input of the buffer amplifier circuit 9 through the voltage divider resistor 11. This change is then added to or subtracted from the 7.2V reference voltage output from the second reference source circuit 2, which is fed into the buffer amplifier circuit 9 through the voltage divider resistor 11, according to the predetermined weight of the voltage divider resistor 11. The output value is adjusted until the target voltage value of 2.8V is output, completing the closed-loop control. The two voltages are then combined into a 10V reference voltage output after the protection circuit 10.

[0023] like Figure 2 As shown, in this embodiment, the voltage divider resistor 11 includes a first voltage divider resistor R1, a second voltage divider resistor R2, a third voltage divider resistor R3, a fourth voltage divider resistor R4, and a fifth voltage divider resistor R5. The non-inverting input of the buffer amplifier circuit 9 is connected to the output of the second reference source circuit 2 through the second voltage divider resistor R2 and the third voltage divider resistor R3. The inverting input of the buffer amplifier circuit 9 is connected to the output of the second reference source circuit 2 through the first voltage divider resistor R1 and the fifth voltage divider resistor R5. The non-inverting input of the buffer amplifier circuit 9 is connected to the output of the integral feedback circuit 8 through the fourth voltage divider resistor R4. The voltage divider resistors 11 have different resistance values ​​and different voltage division ratios. For example, R1=4.99kΩ, R2=4.99kΩ, R3=4.99kΩ, R4=49.9kΩ, and R5=1.07kΩ. When the positive voltage output changes, after closed-loop control by the integrating operational amplifier, the integrating feedback circuit 8 will output a related change to the non-inverting input of the buffer amplifier circuit 9. The influence weight is (R2 / / R3) / (R4+R2 / / R3), which is used for adjustment until the target output value is reached.

[0024] The second reference source circuit 2 outputs a reference voltage of 7.2V, which is then converted to a 2.8V voltage using a pulse-wide module (PWM) for high-precision conversion. This 2.8V voltage is used to synthesize the two references. To ensure the stability of the PWM-modulated 2.8V voltage, equipotential shielding is employed. The basic principle of PWM is to control the amplitude of the output DC voltage by adjusting the ratio of the high-level duration to the total cycle length (i.e., the duty cycle). Frequency provides much better voltage stability and is almost unaffected by external environmental factors. This method of indirectly obtaining voltage through frequency control is far superior to the existing technology that uses only voltage divider resistors for stabilization.

[0025] Furthermore, in this embodiment, the addition of PWM introduces high-frequency quantities into the circuit, which need to be filtered out using a low-pass filter. Introducing a low-pass filter into the DC channel is an effective means of suppressing noise. Passive filters can only achieve poles on the negative real axis, which cannot meet diverse engineering requirements; therefore, active filters are considered. When introducing an active filter, it is necessary to consider preventing its active components from introducing new additional drift into the channel. Therefore, filter circuit 7 can adopt a drift-free, all-pole active filter, which has good low drift and low component sensitivity characteristics, and is beneficial for achieving a highly stable 10V voltage output.

[0026] The reference voltage generation circuit of this invention improves the standard voltage generation circuit and proposes a dual-reference chip synthesis technology. Based on this, a corresponding voltage reference circuit is proposed, thereby reducing its dependence on precision resistors and temperature, reducing the large high-frequency noise generated by PWM modulation, and thus improving the output stability and environmental adaptability of the solid-state voltage reference. The main advantages are as follows: (1) The boost circuit designed with precision resistors is eliminated, reducing the dependence on precision resistors and reducing the output changes caused by precision resistor drift; (2) Through positive and negative reference compensation, the temperature coefficient can be reduced to within 0.05PPM / ℃, which is beneficial to production and greatly reduces the difficulty of adjusting the temperature coefficient of the solid-state voltage reference; (3) It is easy to control the noise of the solid-state voltage reference. The final output of this scheme is a -7.2V output directly from the reference chip and a 2.8V synthesized by the PWM DAC. The -7.2V is the noise of the Zener diode itself, which is low. After being synthesized with the 2.8V modulated by the PWM DAC, the noise brought by the PWM DAC can be effectively suppressed.

[0027] The dual-reference synthesized voltage generation circuit of this invention has been put into practical engineering applications and has proven to solve the problems of high dependence on precision boost resistors, significant influence from ambient temperature, and high output noise in current reference chips. It improves the output stability of the reference voltage and lays the foundation for the localization of voltage references. DC voltage standards are the most important basic parameters in electromagnetic metrology. This invention can be used in applications requiring high-precision voltage, such as value transfer and high-precision voltage output. With changes in the international situation, this invention will gradually be applied to more metrological units, possessing significant market potential.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-reference synthesized voltage generation circuit, characterized in that, include: First reference source circuit (1) and second reference source circuit (2); The PWM circuit (3) includes an analog switch (4) and an isolation chip (5), wherein the analog switch (4) is connected to the output terminal of the second reference source circuit (2) and the isolation chip (5) respectively; The digital control circuit (6) is connected to the isolation chip (5) through the digital control chip; The filter circuit (7) is connected to the analog switch (4); An integral feedback circuit (8) is connected to the filter circuit (7); The buffer amplifier circuit (9) is connected to the output terminal of the second reference source circuit (2) and the integral feedback circuit (8); The protection circuit (10) has its input terminal connected to the first reference source circuit (1) and the buffer amplifier circuit (9), and its output terminal connected to the integral feedback circuit (8). The output of the second reference source circuit (2) is also connected to the non-inverting and inverting terminals of the buffer amplifier circuit (9) through a voltage divider resistor (11); The voltage divider resistor (11) includes a second voltage divider resistor (R2) and a third voltage divider resistor (R3). The non-inverting terminal of the buffer amplifier circuit (9) is connected to the output terminal of the second reference source circuit (2) through the second voltage divider resistor (R2) and the third voltage divider resistor (R3). The voltage divider resistor (11) includes a first voltage divider resistor (R1) and a fifth voltage divider resistor (R5). The inverting terminal of the buffer amplifier circuit (9) is connected to the output terminal of the second reference source circuit (2) through the first voltage divider resistor (R1) and the fifth voltage divider resistor (R5). The voltage divider resistor (11) includes a fourth voltage divider resistor (R4), and the non-inverting terminal of the buffer amplifier circuit (9) is connected to the output of the integral feedback circuit (8) through the fourth voltage divider resistor (R4).

2. The dual-reference synthesized voltage generation circuit according to claim 1, characterized in that, The first reference source circuit (1) outputs a negative reference voltage, and the second reference source circuit (2) outputs a positive reference voltage. The two voltages are finally combined to form the output voltage of the dual reference combined voltage generating circuit.

3. The dual-reference synthesized voltage generation circuit according to claim 2, characterized in that, The output positive voltage signal is used as a feedback signal and is controlled in a closed loop with the integral feedback circuit (8). The positive voltage signal is conditioned in the buffer amplifier circuit (9) to achieve a high-stability output of the positive voltage signal.

4. The dual-reference synthesized voltage generation circuit according to claim 1, characterized in that, The first reference source circuit (1) outputs a reference voltage of -7.2V. After being regulated by the operational amplifier of the protection circuit (10), the output reference voltage is -7.2V. The second reference source circuit (2) outputs a 7.2V reference voltage, which is converted to a 2.8V voltage by the PWM circuit (3). The voltage values ​​input to the non-inverting and inverting terminals of the integral feedback circuit (8) are then compared to form a closed loop. When the voltage value input to the inverting terminal of the integral feedback circuit (8) changes and deviates from the balance, the change output by the integral feedback circuit (8) enters the non-inverting terminal of the buffer amplifier circuit (9) through the voltage divider resistor (11). It is then added or subtracted according to the predetermined weight of the voltage divider resistor (11) to adjust the output value until the target voltage value of 2.8V is output, thus completing the closed loop control. The two voltages are combined into a 10V reference voltage output after the protection circuit (10).

5. The dual-reference synthesized voltage generation circuit according to claim 1, characterized in that, The PWM circuit (3) is treated with equipotential shielding.

6. The dual-reference synthesized voltage generation circuit according to claim 1, characterized in that, The filter circuit (7) uses a drift-free, all-pole active filter.

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