Special small signal output and automatic calibration system and method for power secondary equipment

Abstract

The invention discloses a small signal output and automatic calibration system and method special for power secondary equipment. The system comprises a voltage acquisition loop, a current acquisition loop, an analog switch switching loop, an ADC sampling loop, an acquisition channel calibration module and a calibration parameter calculation module. According to the invention, the internal resistor of the DAC is combined with the operational amplifier to acquire the output current of the current acquisition loop, so that the use of external elements is avoided; meanwhile, voltage and current signals are combined and sent to the ADC sampling loop through the analog switch switching loop, calibration parameters are automatically calculated in combination with a calibration algorithm, the output precision is ensured, the influence of switch network on-resistance errors and external element drift is eliminated, and synchronous monitoring and automatic calibration are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a small signal output and automatic calibration system and method, in particular to a small signal output and automatic calibration system and method special for power secondary equipment. BACKGROUND

[0002] At present, the small signal output precision of power secondary equipment is crucial to system performance. The existing technology usually converts the DAC output current into a voltage signal through an external sampling resistor and an operational amplifier circuit, and monitors it through an ADC. However, this method relies on external components, not only increasing the cost and complexity, but also reducing the reliability and accuracy of monitoring, and even may cause system output control logic error due to the parameter drift or failure of external components. Especially in long time running, the temperature drift and long-term stability problems of external components will further increase the measurement error.

[0003] To solve these problems, the existing technology uses a multiplexer to switch the outputs of multiple DACs to a common ADC for sampling and monitoring in turn. Although this method can improve the flexibility of the system to some extent, the on-resistance introduced by the analog switch switching method will introduce additional measurement error, affecting the monitoring precision. In addition, the time-sharing multiplexing mechanism cannot realize the synchronous real-time monitoring of multiple DAC outputs, limiting the real-time performance and accuracy of the system.

[0004] Another method is to use two pieces of DAC for output splicing and time-interleaved ADC technology to improve the measurement resolution and sampling rate, and realize accurate measurement of the output signal. Although this method enhances the measurement accuracy, it still relies on external reference sources and sampling resistors, and the temperature drift and long-term stability of these external components will cause additional measurement error, increasing the complexity and cost of the system. SUMMARY

[0005] The purpose of the present application is to provide a small signal output and automatic calibration system special for power secondary equipment to realize the calibration of small signal output, ensure the output precision and system reliability, and on the other hand, provide a small signal output and automatic calibration method special for power secondary equipment.

[0006] Technical solution: The small signal output and automatic calibration system of the present application comprises: A voltage acquisition circuit for acquiring the output voltage of the DAC through a voltage follower composed of an operational amplifier, and inputting the voltage sampling signal to an analog switch; A current acquisition circuit for calculating the output current of the DAC by using the internal resistance of the DAC, combining a voltage follower composed of an operational amplifier and a subtractor circuit, and outputting through the subtractor; an analog switch switching loop, configured to select a signal of the voltage acquisition loop or the current acquisition loop based on a DAC output mode switching signal, and output the signal after signal combination; an ADC sampling loop, configured to sample the signal output by the analog switch switching loop and upload a sampling value; an acquisition channel calibration module, configured to input a specified voltage and current signal through an external calibration device, compare an ADC measurement value with an external input value, and calculate an acquisition channel calibration coefficient; a calibration parameter calculation module, configured to calculate a calibration parameter through a linear formula based on an ADC sampling value and a DAC setting value, and store the calibration parameter.

[0007] Preferably, the voltage follower in the voltage acquisition loop adopts an input rail-to-rail operational amplifier, ensuring high-impedance input and low-impedance output.

[0008] Preferably, the subtractor circuit in the current acquisition loop is built by an operational amplifier, and an amplification multiple is determined by a first resistor, a second resistor, a third resistor and a fourth resistor.

[0009] Preferably, the acquisition channel calibration module comprises a calibration process: inputting an external signal, calculating a calibration coefficient, verifying that a sampling accuracy is less than 0.01%, and recalibrating if the verification fails.

[0010] Preferably, the DAC calibration parameter calculation module comprises a calibration process: issuing two different voltage or current values to the DAC, reading a corresponding ADC sampling value, calculating a calibration parameter, verifying that a sampling accuracy is less than a preset error threshold, and recalibrating if the verification fails.

[0011] Preferably, the system further comprises a calibration failure processing mechanism: when calibration fails, a default calibration coefficient is restored and recalculated.

[0012] The small-signal output and automatic calibration method provided by the application comprises the following steps: The voltage acquisition loop acquires a DAC output voltage through a voltage follower built by an operational amplifier, and generates a voltage sampling signal; The current acquisition loop acquires a DAC current output value through a voltage follower and a subtractor circuit built by an operational amplifier, and outputs the value through the subtractor; The analog switch switching loop selects a voltage sampling signal of the voltage acquisition loop and a current sampling signal of the current acquisition loop based on a DAC output mode switching signal, and outputs the signals after signal combination; The ADC sampling loop samples the signal output by the analog switch switching loop, and obtains a sampling value; The acquisition channel calibration module inputs specified voltage signals and current signals through an external calibration device, reads ADC sampling values, and calculates acquisition channel calibration coefficients; Two different setting values are issued to the DAC, two corresponding ADC sampling values are read, calibration parameters are calculated through a linear equation, and parameter validity and sampling precision are verified.

[0013] Preferably, the DAC current output value is calculated by the following formula: I out = (AVDD-V i ) / R. Where I out represents the current output value of the DAC, AVDD is the positive terminal of the DAC power supply, one end of the internal resistance of the DAC is connected to AVDD, and the voltage value at the other end is V i , and R represents the internal resistance value of the DAC.

[0014] Advantages: Compared with the prior art, the present application has the following significant advantages: 1. The current acquisition circuit does not need to use an independent power supply by using an input rail-to-rail operational amplifier, thereby reducing cost; 2. The current is sampled by the internal resistance of the DAC, the circuit is simple to implement, and the influencing factors of the DAC output precision are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of the system framework of the present application; Figure 2 is a schematic diagram of the small signal output and automatic calibration system circuit of the present application; Figure 3 is a schematic diagram of the current acquisition circuit of the present application. DETAILED DESCRIPTION

[0016] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

[0017] As shown in the accompanying Figures 1-2 , the present embodiment provides a small signal output and automatic calibration system special for power secondary equipment, which comprises a voltage acquisition circuit, a current acquisition circuit, an analog switch switching circuit, an ADC sampling circuit, an acquisition channel calibration module, and a calibration parameter calculation module.

[0018] The voltage acquisition circuit is used to acquire the output voltage V out of the DAC through a voltage follower composed of an operational amplifier, and input the voltage sampling signal to the analog switch; the voltage follower uses an input rail-to-rail operational amplifier to ensure high-impedance input and low-impedance output.

[0019] Current acquisition circuit, for calculating the output current of the DAC by using the internal resistance of the DAC, combining a voltage follower composed of an operational amplifier and a subtractor circuit, and outputting through the subtractor; specifically, as shown in the accompanying Figure 3 , the current acquisition circuit calculates the output current I out of the DAC by acquiring the voltage across the internal resistance R of the DAC, one end of the resistance R being the analog positive power supply AVDD and the other end being at a voltage V i , the output current value I out of the DAC being (ADVV-V i ) / R; V i First, the voltage follower composed of the operational amplifier (the same as the voltage acquisition circuit) ensures high input impedance, thereby preventing leakage current from affecting the output current accuracy of the DAC, and then the subtractor circuit built by the operational amplifier subtracts V i from AVDD and amplifies the difference, and outputs to the analog switch.

[0020] The amplification factor is determined by the four high-precision resistors R1, R2, R3 and R4, and when R1 / R 2= R3 / R4, the amplification factor of the subtractor is R2 / R1, and the final output value V iout =R2 / R1* (ADVV-V i ).

[0021] Analog switch switching circuit, for selecting the signals of the voltage acquisition circuit and the current acquisition circuit based on the DAC output mode switching signal, and merging and outputting the signals; specifically, the analog switch switching circuit uses the voltage / current switching signal DA-SEL (controlled by the CPU and not changed after calibration) shared with the DAC output, and gates the voltage sampling signal of the voltage acquisition circuit and the current sampling signal of the current acquisition circuit, merges them into one signal and sends it to the ADC sampling circuit for sampling.

[0022] ADC sampling circuit, for sampling the signal output by the analog switch switching circuit and uploading the sampling value; during calibration, first calibrate the sampling channel, disconnect the DAC output and input a specified size of voltage / current analog quantity from an external calibration device to simulate the voltage and current small signal, then compare the measurement value of the ADC with the external input value, calculate the calibration coefficient of the acquisition channel and store it locally. Then input different voltage and current values from the outside again, calculate the sampling accuracy, if less than two thousandths, it is considered to be calibrated successfully, otherwise, the calibration fails.

[0023] Acquisition channel calibration module, for inputting a specified voltage and current small signal from an external calibration device, comparing the ADC measurement value with the external input value, and calculating the acquisition channel calibration coefficient.

[0024] Wherein, the current small signal generally refers to ±10V or 4-20mA.

[0025] The calibration parameter calculation module is configured to calculate the calibration parameters based on the ADC sampling value and the DAC setting value through a linear formula and store the calibration parameters.

[0026] In the calibration process, the system issues two different voltage / current values Y1 and Y2 to the DAC, and reads the ADC sampling values X1 and X2, and brings the two sets of data into the formula Y=K*X+B to calculate the calibration parameters K and B. It is judged whether the obtained K value and B value are within the error range, if not, it is determined that the calibration fails, otherwise it is stored in the local. Then five different voltages / currents will be issued to the DAC and the sampling accuracy will be calculated, if the sampling accuracy is less than 0.02%, the default calibration coefficient will be restored and the calibration coefficient calculation will be performed again, if the sampling accuracy does not meet the requirement for three times in a row, it is determined that the calibration fails, otherwise the calibration is successful.

[0027] The embodiment also provides a small signal output and automatic calibration method special for power secondary equipment, comprising the following steps: The voltage acquisition circuit acquires the DAC output voltage V out by the voltage follower composed of the operational amplifier; The current acquisition circuit acquires the DAC current output value by the voltage follower and the subtracter circuit composed of the internal resistance R of the DAC and the operational amplifier, and outputs the value through the subtracter; wherein, the current value is calculated based on the formula I out =(ADVV-V i ) / R, and V iout =R2 / R1*(ADVV-V i )。

[0028] The analog switch switching circuit selects the voltage sampling signal of the voltage acquisition circuit and the current sampling signal of the current acquisition circuit based on the DAC output mode switching signal DA-SEL, and outputs the combined signal; The ADC sampling circuit samples the signal output by the analog switch switching circuit to obtain the sampling value X.

[0029] The acquisition channel calibration module inputs the specified voltage signal and current signal through the external calibration device, reads the ADC sampling value, calculates the acquisition channel calibration coefficient, and verifies whether the sampling accuracy is less than 0.02%.

[0030] Two different voltage / current values Y1 and Y2 are issued to the DAC, and the sampling values X1 and X2 of the ADC are read, the calibration parameters K and B are calculated through the linear equation Y=K*X+B, it is judged whether the obtained K value and B value are within the error range, if not, it is determined that the calibration fails, otherwise it is stored in the local. Then five different voltage / current values will be issued to the DAC, and the sampling accuracy is calculated, if the sampling accuracy is less than 0.01%, the default calibration coefficient is restored and the calibration coefficient calculation is performed again, if the sampling accuracy does not meet the requirement for three times in a row, it is determined that the calibration fails, otherwise the calibration is successful.

Claims

1. A small signal output and automatic calibration system for power secondary equipment, characterized in that, The system comprises: a voltage acquisition circuit for acquiring the output voltage of the DAC through a voltage follower composed of an operational amplifier, and inputting a voltage sampling signal to an analog switch; a current acquisition circuit for calculating the output current of the DAC by using the internal resistance of the DAC, combining a voltage follower composed of an operational amplifier and a subtractor circuit, and outputting through the subtractor; an analog switch switching circuit for selecting the signal of the voltage acquisition circuit or the current acquisition circuit based on a DAC output mode switching signal, and outputting the combined signal; an ADC sampling circuit for sampling the signal output by the analog switch switching circuit and uploading the sampling value; an acquisition channel calibration module for inputting a specified voltage and current signal through an external calibration device, comparing the ADC measurement value with the external input value, and calculating the acquisition channel calibration coefficient; a calibration parameter calculation module for calculating the calibration parameter through a linear formula based on the ADC sampling value and the DAC setting value, and storing the calibration parameter.

2. The small signal output and automatic calibration system of claim 1, wherein, The voltage follower in the voltage acquisition circuit adopts an input rail-to-rail operational amplifier, ensuring high-impedance input and low-impedance output.

3. The small signal output and automatic calibration system of claim 1, wherein, The subtractor circuit in the current acquisition circuit is built by an operational amplifier, and the amplification multiple is determined by a first resistor, a second resistor, a third resistor and a fourth resistor.

4. The small signal output and automatic calibration system of claim 1, wherein, The acquisition channel calibration module comprises a calibration process: inputting an external signal, calculating a calibration coefficient, verifying that the sampling accuracy is less than a preset error threshold, and recalibrating if the verification fails.

5. The small signal output and automatic calibration system of claim 1, wherein, The DAC calibration parameter calculation module comprises a calibration process: issuing two different voltage or current values to the DAC, reading the corresponding ADC sampling value, calculating the calibration parameter, verifying that the parameter is within the error range, and verifying the sampling accuracy based on the test value, and determining that the calibration fails if it fails for three times in a row.

6. The small signal output and automatic calibration system of claim 1, wherein, The system further comprises a calibration failure processing mechanism: when the calibration fails, the default calibration coefficient is restored and recalculated.

7. A small signal output and automatic calibration method for power secondary equipment, characterized in that, The system comprises the following steps: a voltage acquisition circuit acquires the output voltage of the DAC through a voltage follower composed of an operational amplifier, and generates a voltage sampling signal; a current acquisition circuit acquires the current output value of the DAC by using the internal resistance of the DAC, combining a voltage follower composed of an operational amplifier and a subtractor circuit, and outputting through the subtractor; an analog switch switching circuit selects the voltage sampling signal of the voltage acquisition circuit and the current sampling signal of the current acquisition circuit based on a DAC output mode switching signal, and outputs the combined signal; an ADC sampling circuit samples the signal output by the analog switch switching circuit to obtain a sampling value; an acquisition channel calibration module inputs a specified voltage signal and a current signal through an external calibration device, reads the ADC sampling value, and calculates the acquisition channel calibration coefficient; two different setting values are issued to the DAC, two corresponding ADC sampling values are read, a calibration parameter is calculated through a linear equation, and the parameter validity and sampling accuracy are verified.

8. The small signal output and automatic calibration method of claim 7, wherein, The DAC current output value is calculated by the following formula: I out = (ADVV-V i ) / R; Wherein, I out represents the current output value of the DAC, AVDD is the positive terminal of the power supply of the DAC, one end of the internal resistance of the DAC is connected to AVDD, and the voltage value at the other end is V i , and R represents the internal resistance value of the DAC.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions, and the computer instructions are used to make the computer execute the method in any one of claims 7 to 8.

10. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor implements the method of any one of claims 7 to 8 when executing the program.

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