Current sampling circuit

Abstract

This disclosure relates to a current sampling circuit, comprising: a switching module, a sampling module, a first resistor RH, and a second resistor RL, wherein the resistance value of the first resistor RH is greater than that of the second resistor RL; a first terminal of the switching module is used to connect to a voltage source, and the switching module is used to selectively connect either the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load; the sampling module is used to collect the current flowing through the first resistor RH or the current flowing through the second resistor RL. This disclosure improves the sampling accuracy of current sampling by switching resistors of different resistance values ​​connected to the power supply circuit, using a high-resistance resistor at low current to improve sampling accuracy, and using a low-resistance resistor at high current to reduce heat generation.

Description

Technical Field

[0001] This disclosure relates to the field of circuit control technology, and more specifically, to a current sampling circuit. Background Technology

[0002] The principle of a current sampling circuit is based on Ohm's law. A sampling resistor is inserted in the current path, and the current value is deduced by measuring the voltage signal. However, a resistor with a fixed resistance value cannot meet the performance requirements of both high-current and low-current operating conditions. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this disclosure provides a current sampling circuit.

[0004] To achieve the above objectives, this disclosure provides a current sampling circuit, comprising: The circuit includes a switching module, a sampling module, a first resistor RH, and a second resistor RL, wherein the resistance of the first resistor RH is greater than that of the second resistor RL. The first terminal of the switching module is used to connect to a voltage source, and the switching module is used to selectively connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load. The sampling module is used to collect the current flowing through the first resistor RH or the current flowing through the second resistor RL.

[0005] Optionally, the second terminal of the switch module is connected to the first resistor RH, the third terminal of the switch module is connected to the second resistor RL, and the sampling module further includes a controller, the first output terminal of the controller being connected to the control terminal of the switch module; The controller is used to control the switching module to connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load.

[0006] Optionally, the current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal, and the controller is used to: Based on at least one of the current magnitude already acquired by the sampling module, the sampling accuracy requirement, the temperature of the first resistor RH, and the temperature of the second resistor RL, the switching module is controlled to connect either the first resistor RH or the second resistor RL into the power supply circuit from the voltage source to the load.

[0007] Optionally, the current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal, and the controller is used to: When the current collected by the sampling module is less than or equal to a preset threshold, the switching module is controlled to connect the first resistor RH to the power supply circuit from the voltage source to the load. When the current collected by the sampling module is greater than the preset threshold, the switching module is controlled to connect the second resistor RL into the power supply circuit from the voltage source to the load.

[0008] Optionally, the current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal, and the controller is used to: When the current collected by the sampling module in multiple consecutive sampling cycles is less than or equal to a preset threshold, the switching module is controlled to connect the first resistor RH to the power supply circuit from the voltage source to the load. When the current collected by the sampling module in multiple consecutive sampling cycles is greater than the preset threshold, the switching module is controlled to connect the second resistor RL to the power supply circuit from the voltage source to the load.

[0009] Optionally, the sampling module further includes an operational amplifier connected in parallel with any of the first resistor RH and the second resistor RL.

[0010] Optionally, the sampling module further includes a pre-driver chip connected in parallel with any of the first resistor RH and the second resistor RL, wherein the pre-driver chip integrates an operational amplifier.

[0011] Optionally, the load is a motor in the vehicle steering system.

[0012] Optionally, the connection points of the first resistor RH and the second resistor RL in the power supply circuit are both located on the bus.

[0013] Optionally, the motor is a multiphase motor, and the first resistor RH and the second resistor RL are connected in the power supply circuit on the same phase line of the multiphase motor.

[0014] The above technical solution improves the sampling accuracy of current sampling by switching resistors with different resistance values ​​connected to the power supply circuit. High resistance resistors are used to improve sampling accuracy when the current is low, while low resistance resistors are used to reduce heat generation when the current is high.

[0015] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 A circuit diagram for single-resistor sampling is shown.

[0017] Figure 2 A circuit diagram for dual-resistor sampling is shown.

[0018] Figure 3 A circuit diagram of three-resistor sampling is shown.

[0019] Figure 4 One of the circuit diagrams of the current sampling circuit provided in the embodiment is shown.

[0020] Figure 5 A second circuit diagram of the current sampling circuit provided in the embodiment is shown. Detailed Implementation

[0021] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0022] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0023] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0024] It should be understood that the steps described in the method embodiments of this disclosure may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of this disclosure is not limited in this respect.

[0025] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0026] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0027] In related technologies, resistance sampling mainly includes: single-resistor sampling, dual-resistor sampling, and triple-resistor sampling.

[0028] Please see Figure 1 , Figure 1 A circuit diagram for single-resistor sampling is shown. A sampling resistor is connected in series at the power bus grounding terminal or the lower arm of any arm of a three-phase bridge circuit, and the current value is calculated by measuring the voltage drop. This scheme is inexpensive, uses only a single resistor, and carries the risk of single-point failure. Furthermore, it requires complex algorithms to reconstruct the three-phase current. For example, single-resistor sampling in FOC control requires two samplings and relies on sector judgment.

[0029] Please see Figure 2 , Figure 2 A circuit diagram for dual-resistor sampling is shown. Two independent sampling resistors are set in the lower arms of two different arms of the three-phase bridge circuit.

[0030] Please see Figure 3 , Figure 3 A circuit diagram for three-resistor sampling is shown. Each arm of the three-phase bridge circuit is equipped with an independent sampling resistor to directly measure the current in each phase.

[0031] Current sampling is used in low-voltage EPS systems, whether it's single-resistor sampling, dual-resistor sampling, or triple-resistor sampling. However, when applied to high-voltage (800V) systems, the following drawbacks exist: (1) When the current level is mA under low current conditions, it is greatly affected by noise interference, which seriously affects the sampling accuracy.

[0032] (2) Due to the influence of the operating current and the upper limit of the voltage in the circuit components, it is difficult to select a suitable resistance value. When the resistance is large, the heat generation is serious under high current conditions; when the resistance is small, the sampling accuracy is low.

[0033] To address the technical problems mentioned in the background art and related technologies, this disclosure provides a circuit diagram of a current sampling circuit, as shown below. Figure 4 As shown. The current sampling circuit includes: a switching module U1, a sampling module, a first resistor RH, and a second resistor RL. The switching module U1 is an electronic device used to switch different resistors connected to the power supply circuit. Specifically, it can be implemented using a relay or a semiconductor switching device. Its control terminal receives signals to switch the circuit path.

[0034] A sampling module is used to acquire the actual current or voltage value flowing through the circuit. The sampling module may include an operational amplifier, an inductor, a power meter, or a pre-driver chip with an integrated operational amplifier. When the sampling module is an operational amplifier, it can be connected in parallel with any resistor among the first resistor RH and the second resistor RL to achieve current sampling in the circuit. The sampling module also includes a pre-driver chip connected in parallel with any resistor among the first resistor RH and the second resistor RL, thereby achieving current sampling in the circuit. The sampling module may also include both an operational amplifier and a pre-driver chip. The operational amplifier can be connected in parallel with either the first resistor RH or the second resistor RL, and another resistor can be connected in parallel with the pre-driver chip, achieving current sampling in the circuit using different resistors.

[0035] For example, please continue to see Figure 4 The first resistor RH is connected in parallel with the operational amplifier, and the second resistor RL is connected in parallel with the pre-driver chip.

[0036] Furthermore, the resistance of the first resistor RH is greater than that of the second resistor RL. For example, the resistance of the first resistor RH can be tens of times greater than that of the second resistor RL. For instance, the resistance of the first resistor RH can be 1000Ω, and the resistance of the second resistor RL can be 2Ω, to ensure that the resistance of the first resistor RH is greater than that of the second resistor RL. The resistance values ​​of the first resistor RH and the second resistor RL can also be selected according to actual needs.

[0037] The first terminal of the switching module U1 is used to connect to a voltage source. The switching module U1 is used to selectively connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load. The load can be a motor, a coil, or a device or equipment that converts electrical energy into kinetic energy, light energy, or other forms of energy, such as an incandescent lamp. The sampling module is used to collect the current flowing through the first resistor RH or the current flowing through the second resistor RL. By physically isolating two independent paths, the cross-influence of the two resistors in the circuit is completely eliminated, enabling higher precision current sampling in different ranges.

[0038] In one embodiment, the sampling module further includes a controller, which is a processing unit for logic judgment and signal output. Specifically, it can be implemented using a microcontroller (MCU) or a digital signal processor (DSP). The controller determines the current state and outputs a control signal through a preset algorithm. The first output terminal of the controller is connected to the control terminal of the switching module U1. The second terminal of the switching module U1 is connected to the first resistor RH, and the third terminal of the switching module U1 is connected to the second resistor RL. The controller is used to control the switching module U1 to connect either the first resistor RH or the second resistor RL into the power supply circuit from the voltage source to the load.

[0039] Specifically, the controller sends a switching command to the switching module U1 through its first output terminal, selecting either the first resistor RH or the second resistor RL to be connected to the power supply circuit based on the real-time current status. For example, when a low-current condition is detected in the circuit, the controller instructs the switching module U1 to connect the first resistor RH to the circuit, utilizing its high resistance to amplify the sampling signal. When a high-current condition is detected in the circuit, the controller switches to the second resistor RL to reduce heat generation. By dynamically switching resistors of different resistance values, the performance contradiction of a single resistor over a wide current range is resolved. By switching to a resistor with a larger resistance value, the sampling signal accuracy under low-current conditions can be effectively improved.

[0040] In one embodiment, the current at the connection point of the first resistor and the current at the connection point of the second resistor in the power supply circuit are equal. That is, the connection points of both the first and second resistors in the power supply circuit are located on the busbar. In other words, the connection points of both the first and second resistors are located on the positive terminal busbar, or they can both be located on the negative terminal busbar, or one resistor can be located on the positive terminal busbar and the other on the negative terminal busbar, as shown below. Figure 4 As shown. The first resistor RH and the second resistor RL are connected at the positive terminal bus and the negative terminal bus, respectively.

[0041] The controller is used to control the switching module U1 to connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load, based on at least one of the current magnitude collected by the sampling module, the sampling accuracy requirement, the temperature of the first resistor, and the temperature of the second resistor.

[0042] The sampling accuracy requirement refers to the system's demand for accurate current measurement results, which can be achieved by presetting an error range or dynamically adjusting the operational amplifier's gain parameters. For example, when the system requires higher resolution, the controller can prioritize selecting a resistor with a larger resistance value to enhance signal strength. The temperatures of the first and second resistors refer to the temperature changes caused by the heat generated during current flow, which can be monitored in real time using temperature sensors or thermistors. For example, if the temperature of one resistor exceeds a safety threshold, the controller can switch to another resistor to avoid overheating risks.

[0043] Specifically, the controller makes dynamic decisions based on a comprehensive consideration of current magnitude, accuracy requirements, and temperature conditions. For example, when a small current value is detected and high-precision sampling is required, the controller selects a first resistor RH with a larger resistance value to connect to the circuit. The higher resistance amplifies the voltage signal of the small current, thereby reducing the impact of noise interference on the sampling results. If the system is operating under high current conditions and the first resistor RH will experience temperature increases due to the high current, the controller can switch to a second resistor RL with a smaller resistance value to reduce heat generation and maintain system stability. Furthermore, when sampling accuracy requirements change, such as switching from conventional monitoring to high-resolution mode, the controller can adjust the resistor selection strategy based on a preset threshold or a real-time calculated error range. By introducing a dual-resistor structure and a dynamic switching mechanism, the controller can adaptively select the optimal sampling path based on real-time operating parameters, thereby ensuring accuracy while avoiding device damage.

[0044] In one embodiment, the current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor in the power supply circuit are equal. The controller is configured to: control the switching module U1 to connect the first resistor RH to the power supply circuit from the voltage source to the load when the current collected by the sampling module is less than or equal to a preset threshold; and control the switching module U1 to connect the second resistor RL to the power supply circuit from the voltage source to the load when the current collected by the sampling module is greater than the preset threshold.

[0045] The preset threshold refers to a critical current value set according to the system's operating current range and accuracy requirements. It can be implemented using a fixed value or a dynamic adjustment strategy, and is used to distinguish between low-current and high-current operating conditions. The difference in resistance values ​​between the first resistor RH and the second resistor RL makes RH suitable for low-current, high-precision sampling, while RL is suitable for high-current, low-heat-generating scenarios.

[0046] Specifically, when the load current is in the low range, the controller compares the sampled current with a preset threshold to determine whether to trigger a switching action. If the current remains below or equal to the threshold, the switching module U1 connects the high-resistance first resistor RH to the circuit. At this time, the sampling module calculates the current value through the voltage across RH. Because RH has a large resistance, the voltage signal corresponding to a small current is more easily detected and amplified, thereby improving the measurement accuracy under low current conditions. When the load current exceeds the threshold, the controller switches to the low-resistance second resistor RL. At this time, the voltage drop generated by the current flowing through RL is small, but the low resistance of RL can reduce power loss and temperature rise when a large current passes through, avoiding performance degradation or damage caused by resistor overheating.

[0047] This solves the problems of severe interference in current sampling under low current conditions and excessive resistance heating under high current conditions in high-voltage systems, while improving sampling accuracy and system reliability across different current ranges. By setting a reasonable preset threshold, erroneous switching caused by instantaneous current fluctuations can be avoided, ensuring stable circuit operation.

[0048] In one embodiment, the current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal. The controller is configured to: control the switching module U1 to connect the first resistor RH to the power supply circuit from the voltage source to the load when the current collected by the sampling module in multiple consecutive sampling cycles is less than or equal to a preset threshold; and control the switching module U1 to connect the second resistor RL to the power supply circuit from the voltage source to the load when the current collected by the sampling module in multiple consecutive sampling cycles is greater than the preset threshold.

[0049] In this context, "multiple consecutive sampling periods" refers to the system acquiring data over multiple independent time intervals when determining the current state. This can be achieved using a fixed-time detection window, such as setting three consecutive 10-millisecond detection periods. By using data acquired through multiple consecutive sampling periods to determine the current, the influence of transient interference on the judgment result can be eliminated, ensuring the stability of the current state.

[0050] Specifically, taking a preset threshold of 500mA as an example, when the controller detects that the current in the power supply circuit does not exceed 500mA in multiple consecutive sampling cycles, it determines it as a low-current condition and controls the switching module U1 to connect to the first resistor RH. At this time, the high-resistance resistor amplifies the small current signal, improving sampling accuracy. Conversely, if the current remains above 500mA for three consecutive cycles, it switches to the second resistor RL, utilizing its low resistance to reduce power loss. This multi-cycle verification mechanism effectively filters abnormal data caused by PWM noise or instantaneous load changes, improving the accuracy of current state identification. Simultaneously, the multi-cycle detection mechanism reduces the frequency of operation of the switching module U1, extending the lifespan of switching devices such as relays.

[0051] Please refer to the following for details on the specific implementation process. Figure 4 In this circuit, U1 is a switching module. Pins 1 and 2 are normally open, forming a low-current sampling circuit; pins 2 and 3 are normally closed, forming a high-current sampling circuit. Q1, Q2, Q3, Q4, Q5, and Q6 are power N-type MOSFETs in a three-phase bridge. U, V, and W represent the three phases of the motor. The first resistor RH and the second resistor RL are sampling resistors. The first resistor RH is used for low-current operation, and the second resistor RL is used for high-current operation. The first resistor RH and the second resistor RL are filtered through differential signal traces and then input to the operational amplifier and the operational amplifier integrated inside the pre-driver chip. The operational amplifier amplifies the acquired voltage signal by a pre-set factor and outputs it as an analog current signal, which is then sent to the controller MCU. Switching module U1 is a single-pole double-throw relay, controlled by the controller MCU.

[0052] In one implementation, please refer to Figure 5 The load is a motor in the vehicle steering system, and the motor is a multi-phase motor. The first resistor RH and the second resistor RL are connected in the power supply circuit on the same phase line of the multi-phase motor.

[0053] In this context, the motor in the vehicle steering system refers to the electric motor used to drive the vehicle steering mechanism. Specifically, it can be a permanent magnet synchronous motor or an induction motor, and its operating voltage range can cover high-voltage systems, such as 800V. In the current sampling circuit, this motor is connected as a load to a power supply circuit consisting of a voltage source, a switching module U1, a sampling module, and resistors of different resistance values. By switching the resistors with different resistance values, sampling of the load under different current conditions is achieved.

[0054] Furthermore, the connection points of the first resistor RH and the second resistor RL can be set on the phase line connected to the load, or the connection point of the first resistor RH can be set on the phase line connected to the load, and the connection point of the second resistor RL can be set on the lower bridge arm in the three-phase bridge circuit, so as to achieve sampling and improve security through mutual verification.

[0055] Specifically, in a vehicle steering system, the motor's operating current dynamically changes with steering demand, exhibiting alternating periods of low and high current. When the motor is operating at low current, the switching module U1 connects the first resistor RH to the power supply circuit. At this time, the sampling module collects the current signal flowing through this resistor, and the amplified voltage signal is transmitted to the controller for processing. When the motor is operating at high current, the switching module U1 switches to the second resistor RL to prevent overheating due to excessive current. For example, when the steering assist demand is low, the motor operating current may be below 500mA, in which case a high-resistance resistor is activated to improve sampling accuracy. However, under emergency steering or high load conditions, the current may reach 8A, in which case a low-resistance resistor is switched to reduce the risk of overheating. This circuit ensures stable acquisition of motor operating status data across different current ranges by dynamically adjusting the sampling resistor.

[0056] In the specific implementation process, please continue to refer to Figure 5 When the system powers on, the entire system initializes and performs a self-test. The pre-driver chip turns off the MOSFET switch, at which point the switching module U1 is normally open, and pins 1 and 2 are conducting. Since the MOSFET switch is off, no current flows through the first resistor RH and the second resistor RL. The operational amplifier acquires the voltage signal across the first resistor RH via differential signal acquisition, filters it, and outputs it to the controller MCU after a pre-set amplification factor. The pre-driver chip acquires the voltage signal across the second resistor RL via differential signal acquisition, filters it, and outputs it to the controller MCU after a pre-set amplification factor. The controller MCU records the initial deviation voltage of the two channels and performs zero-point calibration.

[0057] Next, when the controller MCU issues a torque demand, the system starts working. At this time, the current sampling loop is the default loop (small current sampling loop). The bus current flows through the relay, through the first resistor RH, and is output to the inverter upper bridge. After passing through the control algorithm, it flows through the motor phase limit back to the inverter lower bridge, and then through the second resistor RL back to GND. At this time, the system reads the voltage V_RH across the first resistor RH of the small current sampling channel and calculates the actual current value according to the following formula: (1) Then, using formula (1), the operational amplifier amplifies the actual current value by the set amplification factor. The voltage signal is converted into a voltage signal and output to the controller MCU. The controller MCU uses the acquired voltage signal to perform FOC control.

[0058] Then, the sampling loop switches from low current to high current. When the system performs FOC control, the controller MCU detects the system current value. The current is greater than the preset boundary current for n consecutive periods. After setting, the sampling loop is switched, i.e. When, where t is the system current value Greater than the boundary current The duration of set. The controller MCU outputs a signal to control the switch module U1. During the next cycle when the upper MOSFET is turned off, Pin1 and Pin2 are disconnected, and Pin2 is connected to Pin3. The bus current is directly input to the upper bridge of the inverter by the relay. After the control algorithm, it flows through the motor phase limit and back to the lower bridge of the inverter, and flows through the second resistor RL back to GND. At this time, the system reads the voltage V_RL across the sampling resistor RL of the high current channel and calculates the actual current value according to the following formula (2): (2) The actual current value is then amplified by the operational amplifier inside the pre-driver chip by a set factor. The voltage signal is converted into a voltage signal and output to the controller MCU. The controller MCU uses the acquired voltage signal to perform FOC control of the motor.

[0059] Finally, similar to the sampling loop switching from low current to high current operation, after the system performs FOC control, when the controller MCU detects the system current value... The current is less than or equal to the preset boundary current for a set of n consecutive periods. After small, the sampling loop is switched, that is: The controller MCU outputs a signal to control relay U1, which disconnects Pin2 and Pin3 during the next MOS transistor turn-off cycle, and connects Pin2 to Pin1 to continue small current detection.

[0060] Through the above steps, the system is divided into high-current and low-current operating conditions at the hardware level. By adding relays, the system can switch sampling circuits according to the operating conditions, selecting different sampling circuits for different current levels. This solves the problems of severe interference and low sampling accuracy under low-current conditions, and severe overheating under high-current conditions.

[0061] Through the above technical solution, this application solves the problem of reduced sampling accuracy and reduced device reliability caused by the large current dynamic range in high-pressure steering systems. By optimizing the resistor selection strategy by matching the motor load characteristics, more accurate current feedback is achieved in steering assist control, thereby improving the control stability and safety of the steering system.

[0062] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0063] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0064] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A current sampling circuit, characterized in that, include: The circuit includes a switching module, a sampling module, a first resistor RH, and a second resistor RL, wherein the resistance of the first resistor RH is greater than that of the second resistor RL. The first terminal of the switching module is used to connect to a voltage source, and the switching module is used to selectively connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load. The sampling module is used to collect the current flowing through the first resistor RH or the current flowing through the second resistor RL.

2. The circuit according to claim 1, characterized in that, The second terminal of the switching module is connected to the first resistor RH, the third terminal of the switching module is connected to the second resistor RL, and the sampling module further includes a controller, the first output terminal of the controller is connected to the control terminal of the switching module; The controller is used to control the switching module to connect the first resistor RH or the second resistor RL to the power supply circuit from the voltage source to the load.

3. The circuit according to claim 2, characterized in that, The current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal. The controller is used to: Based on at least one of the current magnitude already acquired by the sampling module, the sampling accuracy requirement, the temperature of the first resistor RH, and the temperature of the second resistor RL, the switching module is controlled to connect either the first resistor RH or the second resistor RL into the power supply circuit from the voltage source to the load.

4. The circuit according to claim 2, characterized in that, The current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal. The controller is used to: When the current collected by the sampling module is less than or equal to a preset threshold, the switching module is controlled to connect the first resistor RH to the power supply circuit from the voltage source to the load. When the current collected by the sampling module is greater than the preset threshold, the switching module is controlled to connect the second resistor RL into the power supply circuit from the voltage source to the load.

5. The circuit according to claim 2, characterized in that, The current at the connection point of the first resistor RH in the power supply circuit and the current at the connection point of the second resistor RL in the power supply circuit are equal. The controller is used to: When the current collected by the sampling module in multiple consecutive sampling cycles is less than or equal to a preset threshold, the switching module is controlled to connect the first resistor RH to the power supply circuit from the voltage source to the load. When the current collected by the sampling module in multiple consecutive sampling cycles is greater than the preset threshold, the switching module is controlled to connect the second resistor RL to the power supply circuit from the voltage source to the load.

6. The circuit according to claim 1, characterized in that, The sampling module also includes an operational amplifier connected in parallel with any of the first resistor RH and the second resistor RL.

7. The circuit according to claim 1, characterized in that, The sampling module also includes a pre-driver chip connected in parallel with any of the first resistor RH and the second resistor RL, and the pre-driver chip integrates an operational amplifier.

8. The circuit according to claim 1, characterized in that, The load is the motor in the vehicle steering system.

9. The circuit according to claim 8, characterized in that, The first resistor RH and the second resistor RL are both connected to the bus in the power supply circuit.

10. The circuit according to claim 8, characterized in that, The motor is a multiphase motor, and the first resistor RH and the second resistor RL are connected in the power supply circuit on the same phase line of the multiphase motor.

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