High-precision voltage detection device

Abstract

A high-precision voltage detection device comprises a differential voltage detection circuit, and the input end of the differential voltage detection circuit is connected with the positive electrode and the negative electrode of direct-current voltage of an electric vehicle battery. The output end of the differential voltage detection circuit is connected with the voltage detection calibration circuit and the voltage detection reverse connection circuit, and the output end of the voltage detection calibration circuit is connected with the single-chip microcomputer through the voltage detection isolation circuit. The output end of the voltage detection reverse connection circuit is connected with the single-chip microcomputer. The utility model has the advantages that the voltage detection precision is improved, and the detection mode can also be used for improving the accuracy of insulation monitoring and improving the operation stability of the whole charging process.

Description

TECHNICAL FIELD

[0001] The utility model belongs to new energy charging pile technical field, mainly relates to electric automobile charging technology. BACKGROUND

[0002] With the steady advance of the national new energy electric vehicle strategy, new energy vehicles show explosive growth, new energy vehicles have a large proportion of pure electric vehicles, and the current mainstream charging method is mainly wired charging, and voltage detection is a key step in the charging process.

[0003] Most of the industry is mainly direct detection, without calibration detection function, or using communication ammeter detection value for calculation. INVENTION CONTENTS

[0004] The technical problem to be solved by the utility model is: how to calibrate and detect the charging voltage of the electric vehicle, and therefore a high-precision voltage detection device is provided.

[0005] The technical scheme of the utility model is specifically:

[0006] A high-precision voltage detection device, comprising a differential voltage detection circuit, the input end of the differential voltage detection circuit is connected to the positive and negative poles of the direct current voltage of the electric vehicle battery; the output end of the differential voltage detection circuit is connected to a voltage detection calibration circuit and a voltage detection reverse connection circuit respectively, wherein the output end of the voltage detection calibration circuit is connected to a single-chip microcomputer through a voltage detection isolation circuit; the output end of the voltage detection reverse connection circuit is connected to the single-chip microcomputer.

[0007] The differential voltage detection circuit comprises a first operational amplifier circuit, the positive input end of the first operational amplifier circuit is connected to the positive pole DC+ of the direct current voltage, the negative input end of the first operational amplifier circuit is connected to the negative pole DC- of the direct current voltage, the first operational amplifier circuit outputs a signal DC_IN and enters the analog switch of the voltage detection calibration circuit.

[0008] The voltage detection isolation circuit comprises a follower circuit composed of a second operational amplifier circuit and a third operational amplifier circuit, the output end of the follower circuit enters a first optocoupler circuit, the output end of the first optocoupler circuit is connected to a fourth operational amplifier circuit, and the output signal of the fourth operational amplifier circuit is VOUTB.

[0009] The voltage reverse detection circuit comprises a fifth operational amplifier circuit, the positive input end of the fifth operational amplifier circuit is connected to the output signal DC_IN of the differential voltage detection circuit, the negative input end of the fifth operational amplifier circuit is connected to a resistance dividing circuit; the output end of the fifth operational amplifier circuit is connected to a second optocoupler circuit, and the output signal DC_FB of the second optocoupler circuit enters the single-chip microcomputer.

[0010] The utility model discloses a beneficial effect is: the utility model provides a voltage detection mode with calibration adds the isolation, and the advantage is to improve the detection voltage precision, and this detection mode can also be used to improve the accuracy of insulation monitoring, improves the whole charging process operation stability. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is differential voltage detection circuit;

[0012] Figure 2 It is voltage detection calibration circuit;

[0013] Figure 3 It is voltage detection isolation circuit;

[0014] Figure 4 It is voltage detection reverse connection circuit. DETAILED DESCRIPTION

[0015] The technical scheme in the utility model embodiment will be clearly and completely described below with the drawings in the utility model embodiment, and apparently, the described embodiment is only a part of the embodiment of the utility model, not all the embodiment.Based on the embodiment in the utility model, all other embodiments obtained by the ordinary skill in the art without making the creative labor belong to the range of the utility model protection.

[0016] A high-precision voltage detection device, comprising a differential voltage detection circuit, the input end of the differential voltage detection circuit is connected to the positive and negative poles of the direct current voltage of the electric vehicle battery;The output end of the differential voltage detection circuit is connected to the voltage detection calibration circuit and the voltage detection reverse connection circuit respectively, wherein the output end of the voltage detection calibration circuit is connected to the single-chip microcomputer through the voltage detection isolation circuit;The output end of the voltage detection reverse connection circuit is connected to the single-chip microcomputer.

[0017] As Figure 1 The differential voltage detection circuit comprises a first operational amplifier circuit U1A, the positive input end of the first operational amplifier circuit U1A is connected to the positive pole DC+ of the direct current voltage through resistors R1-R6, the negative input end of the first operational amplifier circuit U1A is connected to the negative pole DC- of the direct current voltage through resistors R8-R13, wherein the positive input end of the first operational amplifier circuit U1A is also connected with an RC circuit, the RC circuit comprises a first capacitor C1 and a seventh resistor R7 arranged in parallel, a fourteenth resistor R14 is arranged between the negative input end and the output end of the first operational amplifier circuit U1A, wherein R1-R6 and R8-R13 are equal, R7 and R14 are equal, Uin is the difference between the positive pole DC+ and the negative pole DC- of the direct current voltage, then the voltage UDC_IN of the output signal DC_IN of the differential voltage detection circuit is Uin*R7 / (6R1+R7).

[0018] The output signal DC_IN of the differential voltage detection circuit enters the analog switch U4, which is connected with the voltage detection calibration circuit as shown in the table 1. Figure 2 The input and output truth table of the analog switch U4 is shown in the table 1, in which 2.5VREF is the reference value, and the output value DC_OUT of the voltage detection calibration circuit can be controlled by the values of A and B controlled by the single-chip microcomputer. When A=0 and B=1 or A=1 and B=0, 2.5VREF is outputted, and UDC_OUT=U2.5VREF. When A=1 and B=1, the output value is UDC_OUT=UDC_IN.

[0019]

[0020] Table 1.

[0021] The output DC_OUT of the voltage detection calibration circuit enters the voltage detection isolation circuit, and the output signal VOUTB of the voltage detection isolation circuit enters the single-chip microcomputer. The voltage detection isolation circuit is shown in the table 2. Figure 3 The voltage detection isolation circuit includes a following circuit composed of the second operational amplifier circuit U2A and the third operational amplifier circuit U2B, and the output end of the following circuit enters the first optocoupler circuit U3. The output end of the first optocoupler circuit U3 is connected with the fourth operational amplifier circuit U5B, and the output signal of the fourth operational amplifier circuit U5B is VOUTB.

[0022] In the voltage detection isolation circuit, the circuit transmission ratio K=R18 / R15. If R15=R18, the transmission ratio K=1. UDC_OUT is transmitted to the output VOUTB through voltage following and optocoupler isolation. The theoretical calculation value VOUTB=K*UDC_OUT.

[0023] The overall circuit operation process is shown in the table 3.

[0024] 1. The single-chip microcomputer outputs A=0 and B=1 (high and low level control), UDC_OUT is outputted as the reference voltage 2.5VREF through the analog switch U4, and then is outputted as VOUTB=K*U2.5VREF through the voltage detection isolation circuit. Figure 4 VOUTB is directly connected to the detection port of the single-chip microcomputer, and the detection value UO is read out. Then the system transmission ratio K1=UO / (K*UR2.5VREF) can be obtained.

[0025] 2. The single-chip microcomputer outputs A=1 and B=1 (high and low level control), UDC_OUT is outputted as the detection voltage value UDC_IN through the analog switch U4, and the single-chip microcomputer detection value U1 is obtained through the isolation circuit. Then UDC_IN=U1 / K1 can be obtained, and UDC_IN=U1*K*UR2.5VREF / UO can be obtained. In order to facilitate calculation, the circuit generally sets R18=R15, and K=1. Then UDC_IN=U1*UR2.5VREF / UO can be obtained.Figure 1 The operation UDC_IN=Uin*R7 / (6R1+R7) is shown, Uin=UDC_IN* (6R1+R7) / R7 can be obtained, and Uin=U1* UR2.5VREF* (6R1+R7) / (R7*U0) is obtained, and finally the input voltage value, that is, the charger output voltage, is calculated.

[0026] Figure 4 As shown, the voltage connection reverse detection circuit includes a fifth operational amplifier circuit U5A, the non-inverting input end of the fifth operational amplifier circuit U5A is connected with the output signal DC_IN of the differential voltage detection circuit, and the inverting input end of the fifth operational amplifier circuit U5A is connected with a resistance voltage dividing circuit; the output end of the fifth operational amplifier circuit U5A is connected with a second optocoupler circuit U6, and the output signal DC_FB of the second optocoupler circuit U6 enters a single-chip microcomputer. In the circuit, R24 is greater than or equal to 100R28, the normal UDC_IN should be greater than the resistance voltage dividing value U3 of R24 and R28, and a high level is output, after passing through the second optocoupler circuit U6, UDC_FB is low, and is fed back to the single-chip microcomputer; if UDC_IN is negative, because R24 is greater than or equal to 100R28 in the circuit, the resistance voltage dividing value U3 of R24 and R28 is close to 0V, the resistance voltage dividing value U3 is greater than UDC_IN, and after being transmitted through the second optocoupler circuit U6, UDC_FB is high, and the single-chip microcomputer reports a connection reverse fault.

[0027] The utility model discloses a high-precision detection scheme based on the existing voltage detection mode, can solve the conversion from high voltage to low voltage, and the isolation mode needs to be added in the conversion process, and there will be corresponding attenuation and the like in the transmission process, therefore, the reference voltage needs to be added for calibration, the value of the detected voltage can be more accurately reflected, corresponding deviation caused by the isolation and the device deviation problem is avoided, and the calculation is more accurate. The utility model also compares the ammeter detection condition, and the phase difference value cannot be greater than 5V, and the ammeter detection value and the voltage detection value are greater than 5V, and corresponding faults can be reported. Meanwhile, the voltage detection value is also used for connection reverse detection in combination with the charging pile characteristics.

[0028] The above-mentioned is only the preferred embodiment of the utility model, and it should be pointed out that for the person skilled in the art, without departing from the overall concept of the utility model, a number of changes and improvements can be made, and these should also be regarded as the protection range of the utility model.

Claims

1. A high-precision voltage detection device, characterized by: The differential voltage detection circuit comprises a first operational amplifier circuit, a positive input end of the first operational amplifier circuit is connected to a DC positive pole DC+, an inverting input end of the first operational amplifier circuit is connected to a DC negative pole DC-, and the first operational amplifier circuit outputs a signal DC_IN and enters an analog switch of a voltage detection calibration circuit.

2. The high-precision voltage detection device according to claim 1, characterized in that: The differential voltage detection circuit comprises a first operational amplifier circuit, a positive input end of the first operational amplifier circuit is connected to a DC positive pole DC+, an inverting input end of the first operational amplifier circuit is connected to a DC negative pole DC-, and the first operational amplifier circuit outputs a signal DC_IN and enters an analog switch of a voltage detection calibration circuit.

3. The high-precision voltage detection device according to claim 2, characterized in that: The voltage detection isolation circuit comprises a follower circuit composed of a second operational amplifier circuit and a third operational amplifier circuit, an output end of the follower circuit enters a first optocoupler circuit, an output end of the first optocoupler circuit is connected to a fourth operational amplifier circuit, and an output signal of the fourth operational amplifier circuit is VOUTB.

4. The high-precision voltage detection device of claim 1, wherein: The voltage detection isolation circuit comprises a follower circuit composed of a second operational amplifier circuit and a third operational amplifier circuit, an output end of the follower circuit enters a first optocoupler circuit, an output end of the first optocoupler circuit is connected to a fourth operational amplifier circuit, and an output signal of the fourth operational amplifier circuit is VOUTB. The voltage detection isolation circuit comprises a follower circuit composed of a second operational amplifier circuit and a third operational amplifier circuit, an output end of the follower circuit enters a first optocoupler circuit, an output end of the first optocoupler circuit is connected to a fourth operational amplifier circuit, and an output signal of the fourth operational amplifier circuit is VOUTB.

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