Domestic automotive-grade high-current Hall current sensor application case sharing

The domestic automotive-grade Hall current sensor CH704 is an isolated integrated current sensor chip developed for large current detection applications above 50A. It has the advantages of high precision, enhanced insulation withstand voltage, high reliability and low power consumption.

The chip integrates a precision programmable linear Hall chip, a small magnetic ring and a copper bus with an on-resistance of 0.1mΩ, which can achieve current detection of +/-50A, +/-100A, +/-150A, +/-200A, and can measure a maximum surge current of 400A through factory pre-programming. The internal low-offset, chopper-stabilized linear Hall chip combined with a unique temperature compensation circuit design achieves good temperature consistency within the full temperature range of CH704 (-40℃ to 150℃). The chip has been calibrated for sensitivity and static (zero current) output voltage before leaving the factory, providing a typical high accuracy of ±1% over the full temperature range.

Its main applications include:

• Automotive electronics: automotive OBC, DC-DC, EPS motor, etc.

• Industrial control: uninterruptible power supply (UPS), welding machine/mobile communication equipment, etc.

• High-power motors: balance car/unicycle controller, heat pump/ice maker, etc.

• Energy: process control, battery testing, energy measurement, etc.

Measuring current above 50A: Yirui isolated integrated current sensor CH704 The article has introduced some related applications. Let's learn how to use the CH704 chip from some other specific applications (click on the blue link for specific applications):

1. Introduction to a heat pump device protection circuit with automatic switching overcurrent protection module (ACS758/CH704 application case)

The following is a brief description of the drawings required for describing the embodiments.

In this example, the current-voltage conversion unit includes a linear current sensor chip U1 of model CH704, the input terminal (IP+, IP-) of the linear current sensor chip is connected to the mains input terminal, the comparison unit includes a first resistor R1, a second resistor R2 and an op amp A1, the first resistor and the second resistor are connected in series between the power supply terminal and the ground, one input terminal of the op amp is connected to the output terminal (VOUT) of the linear current sensor chip, the other input terminal of the op amp is connected between the first resistor and the second resistor, and the output terminal of the op amp is connected to the analog switch control terminal. The linear current sensor chip CH704 is equipped with a Hall sensor, which converts the magnetic field signal generated by the current into a voltage signal output, and compares it with the potential between the first resistor and the second resistor. The comparison result is output through the op amp, thereby realizing the detection and judgment of the input current of the mains input terminal.

2. Introduction to the protection board circuit of high-power lithium battery pack BMS (battery management system) (ACS758/CH704 application case)

Traditional BMS boards are usually designed with discrete components such as operational amplifiers and MOS tubes, which have disadvantages such as complex principles, high costs, difficulty in debugging, and high failure rates.

The CH704 chip is used to measure the output current in isolation. The CH704 chip converts the current signal into a voltage signal and inputs it into the A/D pin of the nrF51822 chip. The 4 and 5 pins of the CH704 are connected in series to the output of the battery, with the 4 pin connected to + and the 5 pin connected to -.

Discharging over-limited cells is the core action of the entire BMS board. When the battery is almost fully charged, there are many cells that need to be discharged. If the discharge operation is continued, the LTC6803 and related circuits will be hot. In order to reduce the temperature, I adopted a time-sharing balancing algorithm, which takes advantage of the fact that the cell voltage cannot change suddenly. That is, the balancing circuit starts working in a certain period of time and shuts down in another period of time. In this way, the cell voltage is balanced and the temperature rise of the balancing circuit is very small.

3. Hall current sensor ACS758/ACS770/CH704 is used in the current detection device of three-phase four-bridge inverter

Two current detection pins of the Hall current sensor are connected in series to the three-phase output circuit of the three-phase four-bridge-arm inverter, and the signal output pin of the Hall current sensor is connected to the sampling current processing circuit.

The Hall current sensor can use Allegro's ACS758 or ACS770 chips, or the ***CH704 from Iris Semiconductor.

Figure 1 Schematic diagram of the device.

Figure 2 Schematic diagram of the installation position of the Hall current sensor.

Three Hall current sensors CS(A), CS(B), CS(C), three sampling current processing circuits D and a digital signal processor DSP. The three Hall current sensors are respectively connected in series to the three-phase output lines of the three-phase four-bridge arm inverter to detect the three-phase output current. Each Hall current sensor is respectively connected to the corresponding sampling current processing circuit, and then connected to the digital signal processor to convert the collected current analog signal into a current digital signal and then transmit it to the digital signal processor.

Figure 3 Schematic diagram of the sampling current processing circuit.

4. Analysis of key components of GM's "Buick Blue" intelligent electric drive system - application of Hall current sensor ACS758 (CH704) in it

Figure 4 Back of the driver board

Power Board

1. FS50R07W1E3_B11A (650V, 50A), Infineon;

2. ACS758LCB-050B (Currently, Allegro products are in serious shortage, and domestic alternative products CH704 can be used)

3. R75 MKP (0.33uF, 250V), Arcotronics;

4. SUYIN needle holder;

5. The surface of the ceramic aluminum substrate integrated inside the IGBT.

5. Circuit for monitoring the working status of switching power supply (application case of Hall current sensor ACS758/CH704)

The circuit includes a switching power supply output current detection module 1, a switching power supply output voltage detection module 2, a temperature detection module 3 for detecting ambient temperature, a PWM wave pulse width detection module 4 for detecting the pulse width of a PWM wave for controlling the on and off of a switch tube in the switching power supply, a switch tube current detection module 5 for detecting the magnitude of a current flowing through the switch tube in the switching power supply, and a processor 6 for processing detection data. The detection signal output end of the switching power supply output current detection module 1, the detection signal output end of the switching power supply output voltage detection module 2, the detection signal output end of the temperature detection module 3, the detection signal output end of the PWM wave pulse width detection module 4, and the detection signal output end of the switch tube current detection module 5 are respectively connected to the processor 6.

The switching power supply output current detection module 1 adopts a current sensor U1 with a chip model of ACS758 (or ***CH704), the 4th pin of the current sensor U1 is used as the detection current input terminal, the 5th pin is used as the detection current output terminal, and the 3rd pin is used as the detection signal output terminal of the switching power supply output current detection module 1 and is connected to the processor 6.

6. Current detection method in energy storage bidirectional converter (PCS) equipment

The system has 1 input on the battery (Bat) side, and the output is a three-phase three-wire output. The main power principle block diagram is shown in the figure:

The energy storage inverter supports both grid-connected and off-grid operation modes.

In grid-connected operation, the AC side of the energy storage converter is connected to the grid, and the DC side is connected to the battery. Cooperating with the grid dispatching system, it participates in the grid voltage and frequency regulation to achieve peak load reduction and valley filling of the grid load. Depending on the selected operation mode, the battery can be charged and discharged at constant voltage, constant current and constant power.

During off-grid operation, the DC side of the energy storage inverter is connected to the battery, and the system can output a three-phase AC voltage with a fixed frequency and effective value to achieve continuous power supply to the AC side load.

7. Research on a new hardware circuit solution for commercial air conditioner inverter

Since the high temperature and corrosive environment inside the air-conditioning compressor cannot install a position sensor, the compressor inverter needs to adopt a position sensorless control method. In the sensorless control method, effective detection of the motor phase current is an important part of improving control performance. There are three common sampling methods, as shown in Figure 2.

8. The core of the automotive air conditioning system - air conditioning controller and its key components

The air conditioning controller is connected to multiple sensors in the car, and can accurately obtain the in-car environment through these sensors. At the same time, the controller communicates with the air conditioning control panel through CAN, and can obtain the driver's requirements for the environment in real time. Using internal algorithms, the air conditioning compressor and air conditioning PTC, blower, and actuators such as damper motors and valves are controlled through CAN to achieve precise control of the in-car environment.