阅读说明：本技术 一种隔离式高精度宽范围电压测量系统及测量方法 (Isolated high-precision wide-range voltage measurement system and measurement method ) 是由 边杰 梁景岩 查艺闻 蒋伟 王千龙 施媛媛 王昊 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种隔离式高精度宽范围电压测量系统,包括主电路单元和控制电路单元,主电路单元包括电阻切换电路、数据隔离采样电路以及模数转换电路,电阻切换电路用以通过分压方式进行待测电压的测量,数据隔离采样电路用以实现主电路单元与控制电路单元实现电气隔离,电阻切换电路的输出端数据隔离采样电路的输入端,数据隔离采样电路的输出端接模数转换电路的输入端,控制电路单元包括连接在数字信号处理器上的隔离控制电路,本发明通过实时改变采样电路的电压变比,来获得更高的测量精度。(The invention discloses an isolated high-precision wide-range voltage measuring system, which comprises a main circuit unit and a control circuit unit, wherein the main circuit unit comprises a resistance switching circuit, a data isolation sampling circuit and an analog-to-digital conversion circuit, the resistance switching circuit is used for measuring voltage to be measured in a voltage division mode, the data isolation sampling circuit is used for realizing electrical isolation between the main circuit unit and the control circuit unit, the output end of the resistance switching circuit is connected with the input end of the data isolation sampling circuit, the output end of the data isolation sampling circuit is connected with the input end of the analog-to-digital conversion circuit, and the control circuit unit comprises an isolation control circuit connected to a digital signal processor.)

1. An isolated high-precision wide-range voltage measurement system is characterized by comprising a main circuit unit and a control circuit unit, wherein the main circuit unit comprises a resistance switching circuit, a data isolation sampling circuit and an analog-to-digital conversion circuit, the resistance switching circuit is used for measuring voltage to be measured in a voltage division mode, the data isolation sampling circuit is used for realizing electrical isolation between the main circuit unit and the control circuit unit and inhibiting high-frequency interference and noise signals of a main circuit, the output end of the resistance switching circuit is connected with the input end of the data isolation sampling circuit, and the output end of the data isolation sampling circuit is connected with the input end of the analog-to-digital conversion circuit;

the resistance switching circuit comprises preset voltage division resistors Ra and Rb, voltage division transformation ratio adjusting resistors R1-Rn and MOSFET adjusting switches Q1-Qn which are connected in series, the voltage division transformation ratio adjusting resistors R1-Rn and the MOSFET adjusting switches Q1-Qn are correspondingly connected in series and then connected in parallel at two ends of the preset voltage division resistor Rb, two ends of the preset voltage division resistors Ra and Rb are used as voltage sampling ends after being connected in series, and two ends of the resistor Rb are used as sampling voltage output ends; the data isolation sampling circuit comprises a linear optical coupler and an operational amplifier, wherein the linear optical coupler consists of a light emitting diode D1 and two photodiodes D2 and D3, and can form a negative feedback circuit by matching with the operational amplifier;

the control circuit unit comprises an isolation control circuit connected to the digital signal processor, the isolation control circuit is used for controlling the work of the MOSFET regulating switch and comprises n groups of MOSFET isolation driving circuits connected to the output end of the digital signal processor; the isolation driving circuit comprises a photoelectric coupler and a transistor amplifying circuit.

2. The isolated high-precision wide-range voltage measuring system of claim 1, wherein the data isolation sampling circuit comprises an amplifier A1, an amplifier A2, an amplifier A3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a light emitting diode D1, a photodiode D2, and a photodiode D3, wherein an input anode of the amplifier A1 is connected with the resistor R5 and then used as an input anode of the data isolation sampling circuit, an input cathode of the amplifier A1 is connected with an output end thereof through the resistor R6, an output end of the amplifier A1 is connected with a cathode of the photodiode D2 through the resistor R7 and an input cathode of the amplifier A2, an anode of the photodiode is connected with ground and used as an input cathode of the data isolation sampling circuit, an input anode of the amplifier A2 is connected with a cathode of the amplifier A2 through the capacitor C1, the output end of the amplifier A2 is connected with the cathode of the light-emitting diode D1 through the resistor R8, and the anode of the light-emitting diode D1 is grounded; the anode of the photodiode D3 is grounded and used as the output cathode of the data isolation sampling circuit, the cathode of the photodiode D3 is connected with the resistor R9 and then used as the output anode of the data isolation sampling circuit, the input cathode of the amplifier A3 is connected with the cathode of the photodiode D3, the input anode of the amplifier A3 is grounded, the input cathode of the amplifier A3 is connected with the output end of the amplifier through the capacitor C2, and the output end of the amplifier A3 is connected with the output anode of the data isolation sampling circuit.

3. An isolated high-precision wide-range voltage measuring system as claimed in claim 1 or 2, wherein n sets of said isolation control circuits are identical in structure and include a transistor T1, a transistor T2, a light emitting diode D4, a photodiode D5, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a transistor T1 having a terminal connected to the digital signal processor via a resistor R10, a transistor T1 having an emitter connected to ground, a transistor T1 having a collector connected to a cathode of the light emitting diode D4, a transistor D4 having an anode connected to a power supply via a resistor R11, a transistor T2 having a base connected to a cathode of the photodiode D5, a transistor D5 having an anode connected to a power supply, a transistor T2 having an anode connected to a collector of the transistor T2 via a resistor R12, a transistor T2 having a collector connected to a MOSFET regulation switch via a resistor R13, and a transistor T2 having an emitter connected to ground.

4. An isolated high-precision wide-range voltage measurement method, which adopts the voltage measurement circuit as claimed in any one of claims 1-3, and is characterized by comprising the following three stages:

step a) range identification stage: when the voltage measuring circuit starts to work, the MOSFET is controlled to adjust the switching states of the switches Q1-Qn, so that the current voltage division coefficient is the largest, the acceptable input voltage is the largest, and then the digital signal processor samples the output voltage of the voltage measuring circuit to obtain a range identification digital quantity;

step b) range switching stage: when the voltage measuring circuit is designed, the resistance values of the resistors are set according to the sampled transformation ratio range, then a mapping table is compiled, the input range corresponding to each partial voltage transformation ratio and the MOSFET regulating switch signal matrix under the corresponding transformation ratio are specifically listed in the mapping table, the proper partial voltage transformation ratio is determined according to the identification digital quantity obtained in the first stage, and the MOSFET regulating switch is operated to complete transformation ratio switching;

step c) precise measurement stage: and after the range is switched, ADC sampling is carried out again through the digital controller to obtain a measured accurate sampling value, and then the accurate sampling value is reduced to a real value through the selected voltage division transformation ratio to finish accurate sampling and control of the signal.

5. An isolated high precision wide range as in claim 4The voltage measurement method is characterized in that the selection of the current segment in the step b) and the first ADC trial sampling (the transformation ratio is K)₁) Satisfies the following relationship:

where m is the number of bits of the controller ADC, K_iFor the transformation ratio of each segment, p is the number of segmented sampling segments.

Technical Field

The present invention relates to voltage measurement systems, and particularly to a voltage measurement system and a voltage measurement method.

Background

The voltage sampling circuit is crucial in the control of the switching power supply. In both constant voltage and constant current and constant power control, electrical quantity needs to be collected. Generally, the measured voltage is converted into a voltage signal within a certain range for transmission and measurement. In a three-phase switching power supply, the bus voltage is usually above 500V, and the AD conversion unit of the digital controller can only bear the DC voltage of 0-3.3V. Therefore, in order to achieve a given control target, a voltage dividing circuit with a large transformation ratio needs to be constructed, but the control precision is reduced, and the control effect is not ideal.

At present, the method for solving the problem of large-range accurate sampling measurement mainly uses an ADC conversion module with higher precision. For example, with an ADC sampling module with 10-bit precision, the precision can reach 0.0032V (3.2mV) when the input voltage is limited to 3.3V, and if the corresponding measured signal is 537V at the maximum, the minimum resolvable voltage is 0.5V. This is of course based on an analysis of the ideal case, in practice our measurement circuit will add margins such as scaling up. Meanwhile, the voltage ripple caused by the switch can further enlarge the margin of the measuring circuit. At this time, in order to ensure that the control effect is not changed, an AD conversion module with higher precision is selected.

Disclosure of Invention

The invention aims to provide an isolated high-precision wide-range voltage measuring system and a measuring method, so that on the premise of not improving the AD conversion precision, the voltage transformation ratio of a sampling circuit is changed in real time to obtain higher measuring precision.

The purpose of the invention is realized as follows: an isolated high-precision wide-range voltage measuring system comprises a main circuit unit and a control circuit unit, wherein the main circuit unit comprises a resistance switching circuit, a data isolation sampling circuit and an analog-to-digital conversion circuit, the resistance switching circuit is used for measuring voltage to be measured in a voltage division mode, the data isolation sampling circuit is used for realizing electrical isolation between the main circuit unit and the control circuit unit and inhibiting high-frequency interference and noise signals of a main circuit, the output end of the resistance switching circuit is connected with the input end of the data isolation sampling circuit, and the output end of the data isolation sampling circuit is connected with the input end of the analog-to-digital conversion circuit;

the resistance switching circuit comprises preset voltage division resistors Ra and Rb, voltage division transformation ratio adjusting resistors R1-Rn and MOSFET adjusting switches Q1-Qn which are connected in series, the voltage division transformation ratio adjusting resistors R1-Rn and the MOSFET adjusting switches Q1-Qn are correspondingly connected in series and then connected in parallel at two ends of the preset voltage division resistor Rb, two ends of the preset voltage division resistors Ra and Rb are used as voltage sampling ends after being connected in series, and two ends of the resistor Rb are used as sampling voltage output ends; the data isolation sampling circuit comprises a linear optical coupler and an operational amplifier, wherein the linear optical coupler consists of a light emitting diode D1 and two photodiodes D2 and D3, and can form a negative feedback circuit by matching with the operational amplifier;

the control circuit unit comprises an isolation control circuit connected to the digital signal processor, the isolation control circuit is used for controlling the work of the MOSFET regulating switch and comprises n groups of MOSFET isolation driving circuits connected to the output end of the digital signal processor; the isolation driving circuit comprises a photoelectric coupler and a transistor amplifying circuit.

As a further limitation of the present invention, the data isolation sampling circuit specifically includes an amplifier a1, an amplifier a2, an amplifier A3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a light emitting diode D1, a photodiode D2, and a photodiode D3, wherein an input anode of the amplifier a1 is connected to the resistor R5 to serve as an input anode of the data isolation sampling circuit, an input cathode of the amplifier a1 is connected to an output end thereof through a resistor R6, an output end of the amplifier a1 is connected to a cathode of the photodiode D7 and an input cathode of the amplifier a 7 through a resistor R7, the anode of the photodiode is grounded and serves as an input cathode of the data isolation sampling circuit, the input anode of the amplifier a 7 is grounded, the input anode of the amplifier a 7 is connected to an output end of the amplifier a 7 through a resistor R7, the anode of the light-emitting diode D1 is grounded; the anode of the photodiode D3 is grounded and used as the output cathode of the data isolation sampling circuit, the cathode of the photodiode D3 is connected with the resistor R9 and then used as the output anode of the data isolation sampling circuit, the input cathode of the amplifier A3 is connected with the cathode of the photodiode D3, the input anode of the amplifier A3 is grounded, the input cathode of the amplifier A3 is connected with the output end of the amplifier through the capacitor C2, and the output end of the amplifier A3 is connected with the output anode of the data isolation sampling circuit.

As a further limitation of the present invention, the n groups of isolation control circuits have the same structure, and include a transistor T1, a transistor T2, a light emitting diode D4, a photodiode D5, a resistor R10, a resistor R11, a resistor R12, and a resistor R13, wherein a pole of the transistor T1 is connected to the digital signal processor through a resistor R10, an emitter of the transistor T1 is grounded, a collector of the transistor T1 is connected to a cathode of the light emitting diode D4, an anode of the light emitting diode D4 is connected to a power supply through a resistor R11, a base of the transistor T2 is connected to a cathode of the photodiode D5, an anode of the photodiode D5 is connected to the power supply, an anode of the transistor T2 is connected to a collector of the transistor T2 through a resistor R12, a collector of the transistor T2 is further connected to a MOSFET adjusting switch through a resistor R13, and an emitter of the.

An isolated high-precision wide-range voltage measurement method adopts the voltage measurement circuit and comprises the following three stages:

step a) range identification stage: when the voltage measuring circuit starts to work, the MOSFET is controlled to adjust the switching states of the switches Q1-Qn, so that the current voltage division coefficient is the largest, the acceptable input voltage is the largest, and then the digital signal processor samples the output voltage of the voltage measuring circuit to obtain a range identification digital quantity;

step b) range switching stage: when the voltage measuring circuit is designed, the resistance values of the resistors are set according to the sampled transformation ratio range, then a mapping table is compiled, the input range corresponding to each partial voltage transformation ratio and the MOSFET regulating switch signal matrix under the corresponding transformation ratio are specifically listed in the mapping table, the proper partial voltage transformation ratio is determined according to the identification digital quantity obtained in the first stage, and the MOSFET regulating switch is operated to complete transformation ratio switching;

step c) precise measurement stage: and after the range is switched, ADC sampling is carried out again through the digital controller to obtain a measured accurate sampling value, and then the accurate sampling value is reduced to a real value through the selected voltage division transformation ratio to finish accurate sampling and control of the signal.

As a further limitation of the invention, the selection of the current segment in step b) is compared to the first ADC trial sampling (transformation ratio K)₁) Satisfies the following relationship:

where m is the number of bits of the controller ADC, K_iFor the transformation ratio of each segment, p is the number of segmented sampling segments.

Compared with the prior art, the invention has the beneficial effects that:

the device has the advantages that the device is economical, an ultra-high-precision AD sampling module is not required to be selected, and a sampling module with lower precision is matched with the variable voltage division ratio sampling conditioning circuit to obtain higher control precision;

the accuracy is high, the measured voltage in different ranges is uniformly distributed in the acceptable range of the AD sampling module through the transformation ratio adjustment, the sampling range of the AD module is fully utilized, and the measurement accuracy is improved;

the reliability is at the end, the circuit topology is still based on the traditional voltage division circuit, and the circuit topology has extremely high reliability after the resistance and the power of the resistor are carefully selected.

Drawings

FIG. 1 is a schematic diagram of a resistance switching circuit according to the present invention.

Fig. 2 is a schematic diagram of a data isolation sampling circuit according to the present invention.

FIG. 3 is a schematic diagram of an isolation control circuit according to the present invention.

FIG. 4 is a schematic view of the present invention in use.

FIG. 5 is a flow chart of the measurement process of the present invention.

Detailed Description

The present invention will be further described with reference to specific examples, which take four sets of voltage dividing units as an example.

An isolated high-precision wide-range voltage measurement system as shown in fig. 1-4 comprises a main circuit unit and a control circuit unit, wherein the main circuit unit comprises a resistance switching circuit, a data isolation sampling circuit and an analog-to-digital conversion circuit, the resistance switching circuit is used for measuring a voltage to be measured in a voltage division mode, the data isolation sampling circuit is used for realizing the electrical isolation of the main circuit unit and the control circuit unit and inhibiting high-frequency interference and noise signals of the main circuit, the output end of the resistance switching circuit is connected with the input end of the data isolation sampling circuit, and the output end of the data isolation sampling circuit is connected with the input end of the analog-to-digital conversion circuit;

the resistance switching circuit comprises preset voltage division resistors Ra and Rb, voltage division transformation ratio adjusting resistors R1-Rn and MOSFET adjusting switches Q1-Qn which are connected in series, the voltage division transformation ratio adjusting resistors R1-Rn and the MOSFET adjusting switches Q1-Qn are correspondingly connected in series and then connected in parallel at two ends of the preset voltage division resistor Rb, two ends of the preset voltage division resistors Ra and Rb are used as voltage sampling ends after being connected in series, and two ends of the resistor Rb are used as sampling voltage output ends; the data isolation sampling circuit comprises a linear optical coupler and an operational amplifier, wherein the linear optical coupler consists of a light emitting diode D1 and two photodiodes D2 and D3, and can form a negative feedback circuit by matching with the operational amplifier;

the data isolation sampling circuit specifically comprises an amplifier A1, an amplifier A2, an amplifier A3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a light emitting diode D1, a photodiode D2 and a photodiode D3, the input anode of the amplifier A1 is connected with a resistor R5 and then used as the input anode of the data isolation sampling circuit, the input cathode of the amplifier A1 is connected with the output end of the amplifier A through a resistor R6, the output end of the amplifier A1 is connected with the cathode of the photodiode D2 and the input cathode of the amplifier A2 through a resistor R7, the anode of the photodiode is grounded and used as the input cathode of the data isolation sampling circuit, the input anode of the amplifier A2 is grounded, the input cathode of the amplifier A2 is connected with the output end of the amplifier A through a capacitor C1, the output end of the amplifier A2 is connected with the cathode of the photodiode D1 through a resistor R8, and the anode of the light emitting diode D1 is grounded; the anode of the photodiode D3 is grounded and used as the output cathode of the data isolation sampling circuit, the cathode of the photodiode D3 is connected with the resistor R9 and then used as the output anode of the data isolation sampling circuit, the input cathode of the amplifier A3 is connected with the cathode of the photodiode D3, the input anode of the amplifier A3 is grounded, the input cathode of the amplifier A3 is connected with the output end of the amplifier through the capacitor C2, and the output end of the amplifier A3 is connected with the output anode of the data isolation sampling circuit;

the control circuit unit comprises an isolation control circuit connected to the digital signal processor, the isolation control circuit is used for controlling the work of the MOSFET regulating switch and comprises 4 groups of MOSFET isolation driving circuits connected to the output end of the digital signal processor; the isolation driving circuit comprises a photoelectric coupler and a transistor amplifying circuit, 4 groups of isolation control circuits have the same structure and comprise a triode T1, a triode T2, a light emitting diode D4, a photodiode D5, a resistor R10, a resistor R11, a resistor R12 and a resistor R13, the pole of the triode T1 is connected with a digital signal processor through a resistor R10, the emitter of the triode T1 is grounded, the collector of the triode T1 is connected with the cathode of the light emitting diode D4, the anode of the light emitting diode D4 is connected with a power supply through a resistor R11, the base of the triode T2 is connected with the cathode of the photodiode D5, the anode of the photodiode D5 is connected with the power supply, the anode of the triode T2 is connected with the collector of the triode T2 through a resistor R12, the collector of the triode T2 is also connected with a MOSFET adjusting switch through a resistor R13, and the emitter of the triode T.

An isolated high-precision wide-range voltage measurement method as shown in fig. 5, which adopts the voltage measurement circuit as claimed in any one of claims 1-3, and comprises the following three stages:

step a) range identification stage: when the voltage measuring circuit starts to work, the MOSFET is controlled to adjust the switching states of the switches Q1-Qn, so that the current voltage division coefficient is the largest, the acceptable input voltage is the largest, and then the digital signal processor samples the output voltage of the voltage measuring circuit to obtain a range identification digital quantity;

step b) range switching stage: when designing the present voltage measuring circuitSetting the resistance values of the resistors according to the sampled transformation ratio range, then compiling a mapping table, specifically listing the input range corresponding to each partial voltage transformation ratio and the MOSFET regulating switch signal matrix under the corresponding transformation ratio in the mapping table, determining the proper partial voltage transformation ratio according to the identification digital quantity obtained in the first stage, operating the MOSFET regulating switch to complete transformation ratio switching, and selecting the current section and carrying out the first ADC trial sampling (the transformation ratio is K)₁) Satisfies the following relationship:

where m is the number of bits of the controller ADC, K_iP is the number of the segmented sampling segments for the transformation ratio of each segment;

step c) precise measurement stage: and after the range is switched, ADC sampling is carried out again through the digital controller to obtain a measured accurate sampling value, and then the accurate sampling value is reduced to a real value through the selected voltage division transformation ratio to finish accurate sampling and control of the signal.

The present invention will be further described with reference to the following principles.

The invention adopts a design idea of a resistance switching circuit, and assumes that the highest voltage to be measured by the system is U_mIf the margin is Δ V, the input U is sampled_imax＝U_m+ Δ V. Assuming that P segments are divided together for segmented sampling, the upper voltage limit of each segment isThe sampling value range corresponding to each group is U_senserThen the ratio of each segment can be expressed asIt can be seen that the transformation ratio K of the first stage₁Maximum, last step transformation ratio K_pAnd minimum. Accordingly, R can be designed_aAnd R_bThe value of (A) should be guaranteed during designMeanwhile, specific values are calculated according to the power consumption condition. When designing other transformation ratios, the multi-resistance parallel structure can be used for configuration by comprehensive consideration. The calculation formula of the resistance voltage division transformation ratio can be knownIn conjunction with this circuit topology, R can be known_{On the upper part}＝R_a；Therefore, the temperature of the molten metal is controlled,in general, the configuration is performed using j ═ 1 first, since K is passed_preHas completed R_aAnd R_bIs taken as the value of (1), and R is designed again₁(broadly, 1 st resistance) can be matched. Subsequently, if a multi-resistance combination configuration transformation ratio is needed, m can be configured to be any value of 2-4.

Meanwhile, the invention also discloses a control method of the novel resistance switching network. In this scheme, the resistance switching network has four resistors. By reasonable configuration of the resistance value, switching between 16 transformation ratios at most can be realized. The usage matrix can be expressed as:wherein Q is a MOSFET drive signal; s is a1 x 16 column vector, for a total of 16: s₁＝[1 0 0 … 0]^T；S₂＝[0 1 0 … 0]^T…S₁₆＝[0 0 0 … 1]^T。S₁～S₁₆The selection of (2) is related to the resistance value distribution selected by each transformation ratio, and the selection is carried out by integrating the real-time transformation ratio requirement and the resistance network configuration. Assuming that the number of bits of the controller ADC is n and the number of the sampling sections of the segments is P, the selection of the current segment and the first sampling of the ADC (the transformation ratio is K)₁) Satisfies the following relationship:

so far, the resistance switching network will work smoothly. However, there is room for improvement in measuring large voltage dc signals with small ripple: the transformation ratio can be determined when the reference value is changed, and only an upper limit and no lower limit are set for the voltage range of each segment. Therefore, frequent switching is not needed during each measurement, and the stability is improved. In the mode, the switching times can be reduced, and the stability of the sampling circuit is improved. At this time, the transformation ratio switching satisfies the following relationship:

therefore, the real value can be calculated from the accurate sampling value and the corresponding correction transformation ratio, and the restoration of the sampling value is completed. Also in operation, if the ratio is determined at the setting, the digital quantity of the accurate sampling can be used entirely in the control, and the conversion is performed only when the output is required.

Finally, the invention is further illustrated by experimental data. When the bus voltage of 400V is measured, a 10-bit ADC is used for sampling, the maximum input voltage of the ADC is 3.3V, and the measurement is carried out in ten sections.

During specific operation, the transformation ratio is adjusted to maximize the measurement range, namely the measurement range is 0-400V, and a converted digital quantity can be obtained. By comparison with the data in the following table:

a second stage of span switching can then be performed to change the ratio of the resistive switching network to a value at the corresponding span. When the transformation ratio is switched in place, accurate measurement can be carried out.

Of course, if the measured data set point is determined during operation and the measured data remains relatively stable (fluctuating only over a small range) during system operation, then we can determine the transformation ratio directly based on the set point, and there is no need to perform a trial sampling at each measurement. Meanwhile, in order to simplify the control logic, each sampling range is provided with only an upper limit and no lower limit (or the lower limits are all 0). Based on the above example, the ratio selection table in this case can be given as follows:

therefore, accurate sampling of the voltage signal on 0-400V is achieved.

The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.