CN109444792B - Circuit for reducing sampling error of current sensor - Google Patents

Abstract

The invention provides a circuit for reducing sampling error of a current sensor, which eliminates the error caused by VCC (voltage to current) through a current sensor signal conditioning circuit with a reference power supply. The reference power supply comprises a reference power supply generating circuit and a current sensor signal conditioning circuit, wherein the current sensor signal conditioning circuit comprises a current sensor, the current sensor inputs VCC and GND and outputs V₂Output V₂Is connected with a resistor R₃Bias voltage V_offsetConnecting resistor R₅Then forming a second line, and connecting the first line and the second line in parallel to an operational amplifier U₂The voltage V generated by the output end of the reference power generation circuit₁The output line of the reference power generating circuit is connected with the resistor R₄Rear-access operational amplifier U₂Negative input terminal of (1), operational amplifier U₂Is connected with a resistor R between the output end and the negative input end₆The operational amplifier U₂The output end of the voltage-stabilizing circuit obtains V through the subtraction amplifying circuit₂And V₁Difference value V of₃Wherein R is₃Is equal to R₄Resistance value of R₅Is equal to R₆The voltage V generated at the output terminal of the reference power generation circuit₁The value of (d) is 0.5 VCC.

Description

Circuit for reducing sampling error of current sensor

Technical Field

The invention relates to the technical field of current sensor sampling, in particular to a circuit for reducing sampling errors of a current sensor.

Background

The low-error current sampling circuit is the basis of motor control, the static difference or fluctuation of the power supply voltage of the current sensor is one of the reasons for generating sampling errors, and the static difference of the power supply voltage causes the zero drift of the measured current; the supply voltage fluctuation causes the sampling burr to be larger.

The general output calculation formula of the current sensor is as follows:

wherein V_outOutputting a voltage value for the sensor; v_oeVCC is the supply voltage of the current sensor; k is a radical of₁Is the inherent gain of the current sensor; i is_pIs the actual measured current; i is_pnIs the effective range of the sensor. As can be seen from formula (1), if I_pInvariably, the static difference or fluctuation of VCC will also result in V_outChange fromResulting in current sampling errors.

In order to reduce the output error of the current signal conditioning circuit, the error caused by VCC static difference or fluctuation should be reduced or eliminated completely when the hardware circuit is designed.

Disclosure of Invention

In view of the above problems, the present invention provides a circuit for reducing sampling error of a current sensor, which eliminates the error caused by VCC through a current sensor signal conditioning circuit with a reference power supply.

A circuit for reducing sampling error of a current sensor, comprising: the current sensor signal conditioning circuit comprises a reference power supply generating circuit and a current sensor signal conditioning circuit, wherein the current sensor signal conditioning circuit comprises a current sensor, the current sensor inputs VCC and GND and outputs V₂Said output V₂Is connected with a resistor R₃Bias voltage V_offsetConnecting resistor R₅Then forming a second line, wherein the first line and the second line are connected in parallel to an operational amplifier U₂The voltage V generated by the output terminal of the reference power generation circuit₁The output line of the reference power generation circuit is connected with a resistor R₄Rear-access operational amplifier U₂The negative input of the operational amplifier U₂Is connected with a resistor R between the output end and the negative input end₆The operational amplifier U₂The output end of the voltage-stabilizing circuit obtains V through the subtraction amplifying circuit₂And V₁Difference value V of₃Wherein R is₃Is equal to R₄Resistance value of R₅Is equal to R₆The voltage V generated at the output terminal of the reference power generation circuit₁The value of (d) is 0.5 VCC.

It is further characterized in that: the bias voltage V_offsetGenerated by a high-precision power reference chip and having a value of V_offset＝0.5V_{adc_ref}，V_{adc_ref}Is the inherent reference voltage inside the ADC sampling chip;

by modifying R₃、R₄、R₅、R₆The gain of the amplifying circuit can be adjusted by subtractionLarge circuit can obtain V₂And V₁Difference value V of₃，

k₁Is the inherent gain of the current sensor, I_pIs the actual measured current, I_pnIs the effective range of the current sensor;

the reference power generation circuit comprises a resistor R₁、R₂Operational amplifier U₁Operational amplifier U₁The positive input end of the transformer is connected with two lines in parallel, wherein one line is connected with a resistor R₁The power supply voltage VCC of the rear connection current sensor, and the resistance R of the other circuit₂Back ground, said operational amplifier U₁Is connected to the negative input terminal, the operational amplifier U₁The output end of the reference power supply generating circuit is the voltage V generated by the output end of the reference power supply generating circuit₁。

After the invention is adopted, the voltage V generated at the output end of the reference power supply generation circuit₁Has a value of 0.5VCC, V₂The size is shown as formula (1); r₃～R₆，U₂Form a subtraction amplifying circuit, R₃And R₄Designed to be equal in resistance, R₅And R₆Designed to have equal resistance, modify R₃、R₄、R₅、R₆The gain of the amplifying circuit can be adjusted, and V can be obtained by the subtraction amplifying circuit₂And V₁A difference of (i.e. V)₃The formula is as follows:

considering equation (1) and equation (2), one can obtain

Wherein V_offsetIs a bias voltage due to I_pNegative values exist, requiring the introduction of a bias voltage V in the circuit_offset。V_offsetGenerated by a high-precision power reference chip and having a value of V_offset＝0.5V_{adc_ref}，V_{adc_ref}The inherent reference voltage inside the ADC sampling chip is shown in formula (4), and the absence of the power supply voltage VCC in the calculation formula means that the circuit can completely eliminate the influence of VCC, a reference voltage which changes along with VCC is generated by the reference power generation circuit, and the difference between the output signal of the current sensor and the reference voltage is obtained by the subtraction circuit, so that the influence of VCC change in the output signal of the current sensor is eliminated.

Drawings

FIG. 1 is a schematic diagram of a reference power generating circuit according to the present invention;

FIG. 2 is a schematic diagram of a current sensor signal conditioning circuit according to the present invention.

Detailed Description

A circuit for reducing sampling error of a current sensor is disclosed in figures 1 and 2: the reference power supply comprises a reference power supply generating circuit and a current sensor signal conditioning circuit, wherein the current sensor signal conditioning circuit comprises a current sensor, the current sensor inputs VCC and GND and outputs V₂Output V₂Is connected with a resistor R₃Bias voltage V_offsetConnecting resistor R₅Then forming a second line, and connecting the first line and the second line in parallel to an operational amplifier U₂The voltage V generated by the output end of the reference power generation circuit₁The output line of the reference power generating circuit is connected with the resistor R₄Rear-access operational amplifier U₂Negative input terminal of (1), operational amplifier U₂Is connected with a resistor R between the output end and the negative input end₆Operational amplifier U₂The output end of the voltage-stabilizing circuit obtains V through the subtraction amplifying circuit₂And V₁Difference value V of₃Wherein R is₃Is equal to R₄Resistance value of R₅Is equal to R₆The voltage V generated at the output terminal of the reference power supply generation circuit₁The value of (d) is 0.5 VCC.

Bias voltage V_offsetGenerated by a high-precision power reference chip, the value of whichIs a V_offset＝0.5V_{adc_ref}，V_{adc_ref}Is the inherent reference voltage inside the ADC sampling chip;

by modifying R₃、R₄、R₅、R₆The gain of the amplifying circuit can be adjusted, and V can be obtained by the subtraction amplifying circuit₂And V₁Difference value V of₃，

k₁Is the inherent gain of the current sensor, I_pIs the actual measured current, I_pnIs the effective range of the current sensor;

the reference power generating circuit includes a resistor R₁、R₂Operational amplifier U₁Operational amplifier U₁The positive input end of the transformer is connected with two lines in parallel, wherein one line is connected with a resistor R₁The power supply voltage VCC of the rear connection current sensor, and the resistance R of the other circuit₂Rear grounded operational amplifier U₁Is connected to the negative input terminal, an operational amplifier U₁The output end of the reference power supply generating circuit is the voltage V generated by the output end of the reference power supply generating circuit₁。

After the invention is adopted, the voltage V generated at the output end of the reference power supply generation circuit₁Has a value of 0.5VCC, V₂The size is shown as formula (1); r₃～R₆，U₂Form a subtraction amplifying circuit, R₃And R₄Designed to be equal in resistance, R₅And R₆Designed to have equal resistance, modify R₃、R₄、R₅、R₆The gain of the amplifying circuit can be adjusted, and V can be obtained by the subtraction amplifying circuit₂And V₁A difference of (i.e. V)₃The formula is as follows:

considering equation (1) and equation (2), one can obtain

Wherein V_offsetIs a bias voltage due to I_pNegative values exist, requiring the introduction of a bias voltage V in the circuit_offset。V_offsetGenerated by a high-precision power reference chip and having a value of V_offset＝0.5V_{adc_ref}，V_{adc_ref}The inherent reference voltage inside the ADC sampling chip is shown in formula (4), and the absence of the power supply voltage VCC in the calculation formula means that the circuit can completely eliminate the influence of VCC, a reference voltage which changes along with VCC is generated by the reference power generation circuit, and the difference between the output signal of the current sensor and the reference voltage is obtained by the subtraction circuit, so that the influence of VCC change in the output signal of the current sensor is eliminated.

The detailed description of the embodiments of the present invention is provided above, but the present invention is only the preferred embodiments of the present invention, and should not be considered as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the invention as claimed should be covered by this patent.

Claims (1)

1. A circuit for reducing sampling error of a current sensor, comprising: the current sensor signal conditioning circuit comprises a reference power supply generating circuit and a current sensor signal conditioning circuit, wherein the current sensor signal conditioning circuit comprises a current sensor, the current sensor inputs VCC and GND and outputs V₂Said output V₂Is connected with a resistor R₃Bias voltage V_offsetConnecting resistor R₅Then forming a second line, wherein the first line and the second line are connected in parallel to an operational amplifier U₂The voltage V generated by the output terminal of the reference power generation circuit₁The output line of the reference power generation circuit is connected with a resistor R₄Rear-access operational amplifier U₂The negative input of the operational amplifier U₂Is connected with a resistor R between the output end and the negative input end₆The operational amplifier U₂Is transported byV is obtained at the output end through a subtraction amplifying circuit₂And V₁Difference value V of₃Wherein R is₃Is equal to R₄Resistance value of R₅Is equal to R₆The voltage V generated at the output terminal of the reference power generation circuit₁The value of (a) is 0.5 VCC; the bias voltage V_offsetGenerated by a high-precision power reference chip and having a value of V_offset＝0.5V_{adc_ref}，V_{adc_ref}Is the inherent reference voltage inside the ADC sampling chip; by modifying R₃、R₄、R₅、R₆The gain of the amplifying circuit can be adjusted, and V can be obtained by the subtraction amplifying circuit₂And V₁Difference value V of₃，

k₁Is the inherent gain of the current sensor, I_pIs the actual measured current, I_pnIs the effective range of the current sensor;

the reference power generation circuit comprises a resistor R₁、R₂Operational amplifier U₁Operational amplifier U₁The positive input end of the transformer is connected with two lines in parallel, wherein one line is connected with a resistor R₁The power supply voltage VCC of the rear connection current sensor, and the resistance R of the other circuit₂Back ground, said operational amplifier U₁Is connected to the negative input terminal, the operational amplifier U₁The output end of the reference power supply generating circuit is the voltage V generated by the output end of the reference power supply generating circuit₁。

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