Shunt type signal current sensor

Abstract

The utility model discloses a shunt type signal current sensor, which relates to the technical field of large current detection and comprises a power supply, a power supply isolator, a CAN (controller area network) signal isolator, a CAN transceiver, a single chip microcomputer, an ADC (analog-to-digital converter), a thermistor and a shunt, the shunt is connected with the ADC, the thermistor and the ADC are respectively connected with the single chip microcomputer, the single chip microcomputer is connected with the CAN transceiver through the CAN signal isolator, and the CAN transceiver is connected with the single chip microcomputer through the ADC. And the CAN transceiver outputs the data through the terminal. The diverter is of a red copper-manganin-red copper structure, and sampling points are located on the PCBA and are symmetrically arranged relative to the center of the joint of the red copper and the manganin of the diverter. The current sensor can carry out bidirectional measurement, high-voltage and low-voltage isolation of a power supply and a signal is completely realized, and the current sensor is suitable for a total positive end or a total negative end of a battery system. The current sensor performs temperature compensation on acquired data through NTC temperature measurement, and has the advantages of high precision, strong applicability and the like compared with the prior art.

Description

TECHNICAL FIELD

[0001] The utility model relates to current sensor technical field, concretely relates to a shunt type signal current sensor. BACKGROUND

[0002] Under the background that global environmental protection and sustainable development are paid more and more attention, new energy electric cars have received extensive attention and development. In the performance test of new energy electric cars, the high reliability of current detection technology is particularly important. The current detection technologies used in the market at present include shunt current sensors, Hall current sensors and fluxgate current sensors, and the shunt current sensor is widely used due to its high range and fast response speed.

[0003] The shunt current detection method is to connect a shunt in series on the copper bar output of a battery pack. When current flows through the shunt, a voltage difference is generated across the shunt. The resistance value of the shunt is known, and the current can be calculated by Ohm's law. However, since large current can cause the shunt to heat up, the heat further affects the resistance value change, and the real-time current cannot be accurately measured by the table lookup method.

[0004] In addition, due to the problem of electric car burning, people pay more and more attention to the high-voltage safety problem in the use process. In the process of long-time overcharging or over-discharging of the battery pack, if unpredictable failure occurs in the current sensor, the BMS cannot accurately identify the current, and cannot perform closed-loop control, which may cause the whole vehicle to burn in serious cases. INVENTION CONTENTS

[0005] The utility model aims at providing a shunt type signal current sensor, which solves the technical problems of high-voltage safety and large measurement deviation caused by thermoelectric effect.

[0006] The purpose of the utility model can be achieved by the following technical solutions:

[0007] A shunt type signal current sensor comprises a power supply, a power supply isolation, a CAN signal isolation, a CAN transceiver, a single-chip microcomputer, an ADC, a thermistor and a shunt. The shunt is connected to the ADC, the thermistor and the ADC are respectively connected to the single-chip microcomputer, the single-chip microcomputer is connected to the CAN transceiver through the CAN signal isolation, and the CAN transceiver outputs data through a terminal.

[0008] As a further scheme of the utility model, the shunt structure is red copper-manganese copper-red copper, the sampling point is located on the PCBA, and the position is symmetrically placed relative to the red copper and manganese copper connection of the shunt.

[0009] As a further scheme of the utility model, the two ends of the shunt are connected to the current circuit to be collected through a copper bar, and the voltage signal collected by the sampling point is transmitted to the ADC through a filtering circuit.

[0010] As a further scheme of the utility model: the voltage signal collected is transmitted to the single-chip microcomputer processing after being converted by the operational amplifier and 16-bit ADC, and the single-chip microcomputer is output to the CAN bus through the CAN transceiver.

[0011] As a further scheme of the utility model: the current sensor power voltage is 5.5V-18V, is reduced to 5V through the voltage reduction module, and then 5V is output through the transformer, and 3.3V is output through the LDO after the isolated 5V; the single-chip microcomputer is powered by the isolated 3.3V, the CAN isolation chip is powered by the isolated 3.3V and 5V, and the CAN chip is powered by 5V. The main and secondary circuits are isolated through the transformer, and the isolated voltage is 3KV.

[0012] As a further scheme of the utility model: the single-chip microcomputer and the CAN transceiver are connected through the isolation chip, and the isolated voltage is 5KV.

[0013] As a further scheme of the utility model: the CAN isolation chip is NSI8222W1-Q1SWVR chip.

[0014] As a further scheme of the utility model: the CAN chip is TJA1042T / 3 / 1J chip.

[0015] The utility model has the advantages of:

[0016] The current sensor has the functions of high-precision current detection, signal amplification, temperature measurement and calibration. The PGA operational amplifier is used in the current sensor, the analog signal is amplified by the amplifier and converted by 16-bit ADC, 32-bit single-chip microcomputer temperature compensation and calibration correction, and then digital signals are output through the CAN chip bus interface, so that users can directly read the final result, reduce the workload of BMS and improve the use efficiency.

[0017] In the utility model, there is thermal resistance between the NTC and the shunt sampling point, the temperature is collected by the NTC, the shunt is compensated in real time, the accurate resistance value under the temperature is obtained, and then the accurate current is obtained.

[0018] In the utility model, electrical isolation technology is used, high and low voltage electricity is isolated through the transformer and the isolated CAN transceiver, and the isolated voltage is 3KV.

[0019] In the utility model, the EMC specification of the vehicle is met, and the current detection is suitable for high-end or low-end and various harsh environments. BRIEF DESCRIPTION OF DRAWINGS

[0020] The utility model will be further described in combination with the drawings.

[0021] Figure 1 It is the hardware circuit block diagram of the utility model.

[0022] Figure 2 It is the temperature compensation schematic diagram of the utility model shunt. Specific embodiments

[0023] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0024] Please refer to Figure 1 The utility model discloses a shunt type signal current sensor, including power, power isolation, CAN signal isolation, CAN transceiver, singlechip, ADC, thermistor, shunt, the shunt is connected with ADC, the thermistor is connected with singlechip respectively, singlechip is connected with CAN transceiver through CAN signal isolation, and CAN transceiver exports data through terminal.

[0025] The shunt structure is red copper-manganese copper-red copper, and the sampling point is located on the PCBA and is symmetrically arranged at the middle of the connection between the red copper and the manganese copper of the shunt.

[0026] The shunt is connected with the current circuit to be collected through copper bars, and the voltage signal collected by the sampling point is transmitted to the ADC through a filtering circuit.

[0027] The ADC is internally integrated with a PGA operational amplifier, the collected voltage signal is transmitted to the singlechip for processing after being converted by the operational amplifier and a 16-bit ADC, and the singlechip is output to the CAN bus through the CAN transceiver.

[0028] The current sensor power voltage is 5.5V-18V, is reduced to 5V through a voltage reduction module, is output isolated 5V through a transformer, and isolated 5V is output isolated 3.3V through an LDO; the singlechip is powered by isolated 3.3V, the CAN isolation chip is powered by two ways of isolated 3.3V and 5V, and the CAN chip is powered by 5V. The main and secondary circuits are isolated through a transformer, and the isolated voltage is 3KV.

[0029] The singlechip and the CAN transceiver are connected through an isolation chip, and the isolated voltage is 5KV.

[0030] The CAN isolation chip is an NSI8222W1-Q1SWVR chip.

[0031] The CAN chip is a TJA1042T / 3 / 1J chip.

[0032] Referring to Figures 1-2 The specific process is shown as follows:

[0033] Step one: temperature collection

[0034] Two NTCs (thermistors) on the module are connected in series with a 10K resistor, one end of which is connected to 3.3V and the other end is connected to ground; the single-chip microcomputer collects the voltage across the thermistor to obtain the voltage across the 10K resistor, and obtains the current value of the path according to Ohm's law I=U / R, and the voltage / current of the thermistor can obtain the resistance value of the thermistor, and the real-time temperature can be obtained by bringing the resistance value of the thermistor into the fitting curve of the thermistor RT (NTC1 is normal, only the temperature of NTC1 is calculated, when NTC1 is abnormal, the temperature of NTC2 is calculated, and when NTC1 and NTC2 are both abnormal, an NTC abnormality flag is set);

[0035] Step two: shunt resistance calculation

[0036] A large current can cause the shunt to heat up, thereby affecting the resistance value of the shunt, and the temperature of the shunt is compensated by the NTC to obtain the accurate resistance value at a certain temperature. There is a thermal resistance between the NTC sampling point and the shunt, and the relationship between the temperature difference and the thermal resistance is:△T=P x Rth, wherein△T is the temperature difference, P is the power, and Rth is the thermal resistance. The temperature difference△T between the NTC and the shunt is calculated by measuring the thermal resistance and the power of the shunt;

[0037] The temperature T measured by the NTC is the real temperature Tshunt of the shunt, and the real temperature Tshunt of the shunt is brought into the strain effect formula of the shunt to calculate the shunt resistance compensation ratio Rcomp, and finally the real resistance value Rshunt of the shunt can be calculated through the initial resistance value Ri*(1+Rcomp) of the shunt.

[0038] Step three: current collection process

[0039] The ADC internally integrates a PGA, amplifies the collected voltage value across the shunt by 25 times, and then converts the digital signal into a digital signal and transmits it to the single-chip microcomputer (the sampling frequency is 4KHz), the single-chip microcomputer calculates the voltage / resistance Rshunt to obtain the current, and outputs it to the CAN bus through the CAN chip, and the user directly reads the final result.

[0040] The above describes one embodiment of the utility model in detail, but the content described is only a preferred embodiment of the utility model, and cannot be considered as limiting the scope of the utility model. Any equivalent changes and improvements within the scope of the utility model application shall still belong to the patent coverage of the utility model.

Claims

1. A shunt type signal current sensor characterized by, The current sensor comprises a power supply, power supply isolation, CAN signal isolation, a CAN transceiver, a single-chip microcomputer, an ADC, a thermistor, and a shunt.

2. The current sensor according to claim 1, wherein The shunt structure is red copper-manganese copper-red copper, and the sampling point is symmetrically arranged on the PCBA relative to the connection position of the red copper and the manganese copper.

3. A current sensor according to claim 2, wherein the current sensor is a shunt type current sensor. The shunt is connected with the current circuit to be collected through copper bars, and the voltage signal collected by the sampling point is transmitted to the ADC through a filtering circuit.

4. A current sensor according to claim 3, wherein the current sensor is a shunt type current sensor. The ADC is internally integrated with a PGA operational amplifier, the collected voltage signal is transmitted to the single-chip microcomputer for processing after being converted by the operational amplifier and the 16-bit ADC, and the single-chip microcomputer is output to the CAN bus through the CAN transceiver.

5. The current sensor according to claim 1, wherein Two thermistors for collecting temperature are arranged on the current sensor and are respectively connected in series with 10K resistors, one end of each of the thermistors is connected to 3.3V, and the other end is grounded.

6. The current sensor according to claim 1, wherein The power supply voltage of the current sensor is 5.5V-18V, is reduced to 5V through a voltage reduction module, is output as an isolated 5V through a transformer, and is output as an isolated 3.3V through an LDO; the single-chip microcomputer is powered by the isolated 3.3V, the CAN isolation chip is powered by the isolated 3.3V and the isolated 5V, and the CAN chip is powered by the 5V.

7. The current sensor according to claim 1, wherein The primary and secondary circuits are isolated through a transformer, and the isolated voltage is 3KV.

8. A current sensor according to claim 7, wherein the current sensor is a shunt type current sensor. The single-chip microcomputer and the CAN transceiver are connected through an isolation chip, and the isolated voltage is 5KV.

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