A current detection circuit

Abstract

The present invention belongs to the technical field of energy storage systems, and specifically relates to a current detection circuit. The detection circuit includes a controller, N signal amplification circuits, a selection switch module, and an analog-to-digital converter; the input end of each signal amplification circuit is used to connect the input voltage; the output end of each signal amplification circuit is connected to the first N ends of the selection switch module in a one-to-one correspondence, and the output end of each signal amplification circuit is also connected to each analog input end of the controller in a one-to-one correspondence; the N+1th end of the selection switch module is connected to the digital input end of the controller through an analog-to-digital converter; the controller controls the connection of the selection switch module to achieve connection between any of the first N ends of the selection switch module and the N+1th end. Whether it is detecting a small current or a large current, the accuracy of the current detection is guaranteed, so that the current can be guaranteed to have the same accuracy within the full range of detection, and several levels of measurement can be selected according to actual needs, providing a reliable basis for the SOC estimation of the energy storage system.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage systems, and in particular relates to a current detection circuit. Background Art

[0002] With the large-scale access of new energy, the vigorous development of microgrids and smart grids, energy storage systems are becoming an increasingly important and indispensable component of modern power systems. Energy storage systems are generally large in scale, and are mainly charged and discharged in prefabricated cabin energy storage systems. A prefabricated cabin energy storage system consists of hundreds or thousands of battery cells connected in series and parallel. In order to ensure the safe operation of the energy storage system, its battery state of charge (SOC) needs to be accurately estimated. At present, SOC estimation is mainly based on current, so circuit detection accuracy is crucial to SOC estimation.

[0003] At present, current detection mainly adopts one-way current detection. However, due to the influence of the use range and performance of various components, it often leads to inaccurate detection when the current is too small or too large. It is difficult to achieve the same measurement accuracy within the full range, and the current detection range is limited. Summary of the invention

[0004] The invention provides a current detection circuit for solving the problem of inaccurate detection caused by only one current detection circuit.

[0005] In order to solve the above technical problems, the technical solution of the present invention includes:

[0006] The present invention provides a current detection circuit, comprising a controller, N signal amplifying circuits, a selection switch module and an analog-to-digital converter, N≥2; the amplification factors of the signal amplifying circuits are different;

[0007] The controller includes a digital input terminal and N analog input terminals;

[0008] The selection switch module includes an N+1 terminal, and the selection switch module can realize connection between any terminal among the first N terminals and the N+1 terminal;

[0009] The input end of each signal amplifying circuit is used to connect the input voltage, and the input voltage is the current signal of the energy storage module converted into a voltage signal; the output end of each signal amplifying circuit is connected to the first N ends of the selection switch module in a one-to-one correspondence, and the output end of each signal amplifying circuit is also connected to each analog input end of the controller in a one-to-one correspondence; the N+1th end of the selection switch module is connected to the digital input end of the controller through an analog-to-digital converter;

[0010] The controller controls the connection of the selection switch module, and performs preliminary preprocessing and judgment on the amplified analog signal to determine the amplification degree, so as to achieve the connection between one of the first N terminals of the selection switch module and the N+1th terminal.

[0011] The beneficial effects of the above technical solution are as follows: the current detection circuit of the present invention, after the input voltage is amplified by each signal amplification circuit, the amplified analog signal is first directly transmitted to the controller for preliminary preprocessing and judgment by the controller to determine the most appropriate degree of amplification, so as to control the connection between one of the N terminals in front of the selection switch module and the N+1 terminal, so that the amplified signal of the corresponding path is converted into a stable signal after analog-to-digital conversion and then input into the controller to obtain the signal with the best accuracy. Whether it is detecting a small current or a large current, the accuracy of current detection is guaranteed, and the current can be guaranteed to have the same accuracy within the full range of detection. Moreover, several levels of measurement can be selected according to actual needs, which is more flexible to use, providing a reliable basis for SOC estimation of the energy storage system and providing a certain guarantee for the safe operation of the energy storage system.

[0012] Furthermore, in order to achieve voltage following, the detection circuit further includes N voltage following circuits, and each voltage following circuit is arranged one by one between the output end of each signal amplifying circuit and the first N ends of the selection switch module.

[0013] Furthermore, the detection circuit also includes N voltage-dropping resistors, and each voltage-dropping resistor is connected in series between the output end of each signal amplifying circuit and the input end of each voltage follower circuit in a one-to-one correspondence.

[0014] Furthermore, the selection switch module includes N control switches, and the detection circuit also includes a decoder; one end of each control switch is connected to form the N+1th end, and the other end of each control switch is the first N ends respectively; the decoder includes an input end and N output ends, the input end of the decoder is connected to the output end of the controller, and the output ends of the decoder are connected to each control switch one by one to control the control switch to be closed.

[0015] Furthermore, in order to put the controller in an inoperative state to save power when there is no input voltage, the controller also includes a power enable terminal, and the detection circuit also includes N anti-reverse diodes, each anti-reverse diode is connected in series between the output terminal of each signal amplification circuit and the power enable terminal of the controller, and the cathode of each anti-reverse diode is connected to the power enable terminal of the controller.

[0016] Furthermore, the signal amplification circuit includes an op amp; the non-inverting input terminal of the op amp is grounded through a first resistor and is also connected to a reference voltage through a second resistor; the inverting input terminal of the op amp is used to connect the input voltage through a third resistor and is also connected to the output terminal of the op amp through a fourth resistor.

[0017] Furthermore, the voltage follower circuit includes a follower, a non-inverting input terminal of the follower is connected to an output terminal of a corresponding signal amplifying circuit, and an inverting input terminal of the follower is connected to an output terminal of the follower. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a circuit diagram of a current detection circuit of the present invention;

[0019] Figure 2 is a schematic diagram of a selector switch used in the selection switch module of the present invention;

[0020] Figure 3 It is a schematic diagram of the voltage amplification curves of the four amplification circuits of the present invention. DETAILED DESCRIPTION

[0021] A current detection circuit of the present invention, such as Figure 1 As shown, including MCU, decoder U k1 , analog-to-digital converter U k2 , N control switches (S1, S2, ..., S N ), N signal amplification circuits, N voltage follower circuits, N anti-reverse diodes (D1, D2, ..., D N ) and N voltage-dropping resistors (R 01 , R 02 ,……,R 0N ).

[0022] Input voltage V i It is the current signal of the energy storage module converted into a voltage signal.

[0023] The MCU includes a digital input terminal (b1), N analog input terminals (a1, a2, ..., aN), a power supply enable terminal (VCC) and an analog output terminal (b4).

[0024] Each signal amplification circuit includes an operational amplifier, which is an operational amplifier U 11 、Operation amplifier U 12 ,……, operational amplifier U 1N The inverting input of each op amp is connected through the corresponding third resistor (R 31 , R 32 ,……,R 3N )Connect input voltage U iThe output of each op amp is connected to a corresponding voltage drop resistor (R 01 , R 02 ,……,R 0N ) one end. 11 The non-inverting input terminal is connected to the corresponding first resistor R 11 The non-inverting input terminal is also connected to the ground through the corresponding second resistor R 21 Connect the reference voltage V ref The inverting input terminal also passes through the corresponding fourth resistor R 41 Connecting op amp U 11 The output of the op amp U 1N The non-inverting input terminal is connected to the corresponding first resistor R 1N The non-inverting input terminal is also connected to the ground through the corresponding second resistor R 2N Connect the reference voltage V ref The inverting input terminal also passes through the corresponding fourth resistor R 4N Connecting op amp U 1N The resistance values ​​of the resistors included in each signal amplifying circuit may be different, so that the amplification factor of the signal amplifying circuit is different.

[0025] Each voltage follower circuit includes a follower, which is respectively a follower U 21 , Follower U 22 , ..., follower U 2N The non-inverting input terminal of each follower is connected to each drop resistor (R 01 , R 02 ,……,R 0N ) are connected one by one, the inverting input end of each follower is connected to the output end of each follower, and the output end of each follower is also connected to each control switch (respectively S1, S2, ..., S N ) are connected one by one, and the other end of each control switch is connected through an analog-to-digital converter U k2 Connected to the digital input terminal of the MCU. The output terminal of each follower is also directly connected to each analog input terminal of the MCU one by one.

[0026] Each drop resistor (R 01 , R 02 ,……,R 0N ) are also connected to the other end through a corresponding anti-reverse diode (respectively D1, D2, ..., D N ) are connected to the power supply enable terminal of the MCU. The anti-reverse diode mainly plays the role of backflow prevention and clamping.

[0027] Decoder U k1It includes an input terminal and N output terminals. The input terminal of the decoder is connected to the analog output terminal of the MCU, and each output terminal of the decoder is connected to each control switch (S1, S2, ..., S N ) are connected one by one to control the control switches to close one of them.

[0028] Among them, adjusting the resistance value of each resistor in the signal amplification circuit can change the amplification factor of the signal amplification circuit. The voltage signal U obtained by the signal amplification circuit j (j=1, 2, ... N) can be expressed as:

[0029]

[0030] For the jth amplifier, R 1j , R 2j , R 3j , R 4j And the reference voltage V ref is a fixed value, so:

[0031] V j =C 0j -C 1j *V i

[0032] in, is a constant; is a constant.

[0033] Therefore, by adjusting R 1j , R 2j , R 3j , R 4j The voltage signal after amplification of different times can be obtained. In actual application, the number of N and R can be selected according to the application conditions. 1j , R 2j , R 3j , R 4j size.

[0034] The working principle of the current detection circuit is described below.

[0035] Use a shunt or Hall sensor to convert the collected current signal of the energy storage module into a voltage signal, that is, the input voltage U i , then input voltage U i It will pass through each signal amplification circuit, each voltage drop resistor and each anti-reverse diode to generate a voltage signal. When there is a signal at the power supply enable end of the MCU, the MCU starts working and then inputs the voltage U iThe signals will be amplified, stepped down and followed by the signal amplifier circuits, step-down resistors and voltage follower circuits respectively, so that the final voltage signal is directly transmitted to the MCU through the analog input port of the MCU. The MCU first pre-processes these voltage signals to determine which of these voltage signals is within the set voltage range. According to the voltage range of the voltage signal, the MCU outputs the signal to the decoder U k1 , decoder U k1 The control switch corresponding to the interval range is controlled to close, so that the amplification loop where the control switch is located is turned on, and the voltage signal finally obtained by the loop is converted through the analog-to-digital converter U k2 After obtaining a more stable signal, it is transmitted to the digital input terminal of the MCU and converted into a corresponding current by the MCU.

[0036] It should be noted that there are N voltage intervals here. When judging which voltage interval the final voltage signal is within, there must be only one final voltage signal within a certain voltage interval, and there will not be a situation where multiple final voltage signals are within multiple voltage intervals. For example, when N=4, after passing through the signal amplification circuit, the voltage signals obtained are V1, V2, V3, and V4, and V1>V2>V3>V4. The corresponding voltages received by the MCU are V'1, V'2, V'3, and V'4 (because V1, V2, V3, and V4 will be slightly attenuated after passing through the voltage drop resistor). The MCU judges which of V'1, V'2, V'3, and V'4 is within V k1 ~V k2 、V k2 ~V k3 、V k3 ~V k4 , or V k4 ~V k5 If V'1 is within the range of V k1 ~V k2 If the voltage is within the range of 100V, the MCU controls the switch S1 through the decoder to close, and the voltage signal finally obtained is converted to the analog-to-digital converter U k2 The voltage signal is transmitted to the MCU, and the MCU converts the voltage signal into a current signal for output.

[0037] Combine the following Figure 3 , briefly explain the above-mentioned scopes and the basis for division. Figure 3 As shown in the figure, when N=4, the intersection of the output voltage curves in different amplifier circuits is the division point of the range, V k1 ~V k2 、V k2 ~V k3 、V k3 ~V k4 、Vk4 ~V k5 The range of the 4 output voltage curves is V k1 ~V k2 , the range of the amplified voltage curve 2 is V k2 ~V k3 , the range of the amplified voltage curve 3 is V k3 ~V k4 , the range of the amplified voltage curve 4 is V k4 ~V k5 When the input voltage is U i When the voltage curves of different amplifier circuits intersect with each other, they are a, b, c, and d. Since only the intersection a is on the V curve of curve 1, k1 ~V k2 range, b is not within the V of curve 2 k2 ~V k3 range, c is not within the V range of curve 3 k3 ~V k4 range, d is not within the V of curve 4 k4 ~V k5 range, so only one voltage range is valid.

[0038] This detection circuit, whether detecting small current or large current, passes through different circuits, which ensures the accuracy of current detection and can ensure the same accuracy of current within the full detection range. Moreover, several levels of measurement can be selected according to actual needs, which is more flexible to use, providing a reliable basis for SOC estimation of energy storage system and providing a certain guarantee for the safe operation of energy storage system.

[0039] In this embodiment, the selection switch module is implemented by using N control switches, one end of each control switch ( Figure 1 The right end of each control switch in the selection switch module is connected to form the N+1th end of the selection switch module, and the other end of each control switch ( Figure 1 The left end of each control switch in the selection switch module is respectively the first N ends of the selection switch module, thereby achieving the connection between any end of the first N ends of the selection switch module and the N+1th end. As another embodiment, the selection switch module can also use a selector switch, such as Figure 2 As shown, the N+1th terminal on the left is connected to the analog-to-digital converter, and the 1st to Nth terminals on the right are respectively connected to the output terminals of each follower one by one, and the functions required to be implemented by the selection switch module can also be realized.

Claims

1. A current detection circuit, It is characterized in that It includes a controller, N signal amplifying circuits, a selection switch module and an analog-to-digital converter, where N is greater than or equal to 2; the amplification factors of each signal amplifying circuit are different; The controller includes a digital input terminal and N analog input terminals; The selection switch module includes an N+1 terminal, and the selection switch module can realize connection between any terminal among the first N terminals and the N+1 terminal; The input end of each signal amplifying circuit is used to connect the input voltage, and the input voltage is the current signal of the energy storage module converted into a voltage signal; the output end of each signal amplifying circuit is connected to the first N ends of the selection switch module in a one-to-one correspondence, and the output end of each signal amplifying circuit is also connected to each analog input end of the controller in a one-to-one correspondence; the N+1th end of the selection switch module is connected to the digital input end of the controller through an analog-to-digital converter; The controller controls the connection of the selection switch module, and performs preliminary preprocessing and judgment on the amplified analog signal to determine the amplification degree, so as to achieve the connection between one of the first N terminals of the selection switch module and the N+1th terminal.

2. The current detection circuit according to claim 1, It is characterized in that The detection circuit further includes N voltage follower circuits, each of which is arranged one by one between the output end of each signal amplifying circuit and the first N ends of the selection switch module.

3. The current detection circuit according to claim 2, It is characterized in that The detection circuit further includes N voltage-dropping resistors, each of which is connected in series between the output end of each signal amplifying circuit and the input end of each voltage follower circuit in a one-to-one correspondence.

4. The current detection circuit according to claim 1, It is characterized in that The selection switch module includes N control switches, and the detection circuit also includes a decoder; one end of each control switch is connected to form the N+1th end, and the other end of each control switch is the first N ends respectively; the decoder includes an input end and N output ends, the input end of the decoder is connected to the output end of the controller, and the output ends of the decoder are connected to each control switch one by one to control the control switch to be closed.

5. The current detection circuit according to claim 1, It is characterized in that The controller also includes a power supply enable terminal, and the detection circuit also includes N anti-reverse diodes, each anti-reverse diode is connected in series between the output terminal of each signal amplification circuit and the power supply enable terminal of the controller, and the cathode of each anti-reverse diode is connected to the power supply enable terminal of the controller.

6. The current detection circuit according to claim 1, It is characterized in that The signal amplification circuit includes an operational amplifier; the in-phase input terminal of the operational amplifier is grounded through a first resistor and is also connected to a reference voltage through a second resistor; the inverting input terminal of the operational amplifier is used to connect the input voltage through a third resistor and is also connected to the output terminal of the operational amplifier through a fourth resistor.

7. The current detection circuit according to claim 2, It is characterized in that The voltage follower circuit comprises a follower, wherein the in-phase input terminal of the follower is connected to the output terminal of the corresponding signal amplifying circuit, and the inverting input terminal of the follower is connected to the output terminal of the follower.

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