Current sensors play a vital role in charging piles (especially DC fast charging piles), and their performance significantly affects the thermal efficiency and overall energy efficiency of the charging pile. Although the heat generated by the sensor itself is usually small, its measurement accuracy and reliability will indirectly but profoundly affect the thermal efficiency of the system through the following ways:

 

 

 

1.Measurement accuracy directly affects power control accuracy:

 

Core function: Current sensor (usually combined with voltage measurement) is the key to accurately measure input/output power. The power conversion module of the charging pile (such as AC/DC rectifier, DC/DC converter) requires accurate current feedback for closed-loop control (such as PWM control).

 

 

 

Consequences of insufficient precision:

 

Overmodulation/undermodulation: If the current measurement value is too low, the control system will mistakenly think that the output power is insufficient, thereby increasing the on-time or duty cycle of the switch tube (overmodulation), causing the actual current and loss of the power device (IGBT/MOSFET) to exceed the design value and increase the heat generation.

 

 

 

Efficiency point deviation: The power conversion topology of modern charging piles (such as LLC resonant converter) usually has the highest efficiency at a specific load point. Inaccurate current measurement may cause the system to operate at a non-optimal efficiency point, increasing conversion losses.

 

 

 

Unnecessary derating: Measurement errors can also cause the control system to misjudge overcurrent and derate prematurely, protecting the device but reducing available power and potential efficiency (if there is no actual overcurrent).

 

 

 

2.The power consumption of the current sensor itself:

 

Heat generation: The current sensor consumes a certain amount of power when working, and this power will eventually be converted into heat.

 

 

 

How Impact?

 

 

Shunt : Shunt-based sensors have relatively high power consumption (`P_loss = I² * R_shunt`). In high current applications (e.g. 250A, 500A), even if the resistance is very small (e.g. 100µΩ), the power consumption (e.g. `250² * 0.0001 = 6.25W`, `500² * 0.0001 = 25W`) is considerable, becoming a heat source inside the system, increasing the heat dissipation burden.

 

Magnetic sensor: The power consumption of magnetic sensors such as Hall effect sensors, current transformers, and Rogowski coils is usually much lower than that of shunts (generally in the milliwatt to several watt range), and their direct impact on the overall thermal efficiency of the system is relatively small. However, closed-loop Hall sensors need to power the compensation coil, and their power consumption will be slightly higher than that of open-loop Hall sensors.

 

3.Impact on the accuracy of thermal management:

Thermal control is current dependent: The speed control of the charging station’s thermal system (e.g., fan, liquid cooling pump) is usually tied to the measured output current (representing the load and heat generation).

 

 

 

Consequences of insufficient precision:

Insufficient heat dissipation: If the current measurement is low, the cooling system may not be able to provide sufficient air volume or flow, causing the temperature of core heat-generating components such as power devices and magnetic components to rise beyond the design range. High temperature will significantly increase the conductor resistance (copper loss) and the iron loss of magnetic components, further reducing efficiency (forming a vicious cycle) and threatening the life of the device.

 

 

 

Excessive cooling: If the current measurement is high, the cooling system may be overworking (full fan speed). Although the temperature is guaranteed to be safe, it consumes unnecessary auxiliary power and reduces the overall energy efficiency of the system (the portion of the total system input power used for cooling increases).

 

 

 

4.Temperature drift of current sensor:

Accuracy changes with temperature: The accuracy of all current sensors is affected by the operating temperature (temperature drift). For example, the resistance of a shunt resistor will change with increasing temperature, and the sensitivity and zero point of a Hall sensor may also drift.

Error amplification at high temperatures: In the high temperature environment inside the charging pile, if the temperature coefficient of the sensor is large, its measurement error will increase significantly. This increased measurement error at high temperatures will further aggravate the problems mentioned in points 1 and 3 above (reduced control accuracy and mismatched heat dissipation), forming a positive feedback loop that seriously damages thermal efficiency and reliability.

 

 

 

5.Bandwidth and dynamic response:

Capturing rapid changes: Switching power supplies operate at frequencies of tens of kHz or even higher. Current sensors require sufficient bandwidth to accurately and in real time capture rapid changes in current (such as current waveforms at the moment of switching).

 

 

 

Consequences of insufficient response: If the sensor bandwidth is insufficient or the response speed is slow, the current information fed back to the control loop will be delayed or distorted. This may cause the control loop to be unstable (oscillation) or fail to achieve optimal soft switching conditions (such as ZVS/ZCS). Switching losses (especially the turn-on/off losses of switching devices) are one of the main sources of loss in charging piles. Poor control will significantly increase switching losses, reduce efficiency, and generate more heat.

 

 

 

Summary of impact:

 

Indirect but critical: The heat consumption of the current sensor itself (especially Shunt) is one of the system heat sources, but usually not the largest. Its most core impact lies in the accuracy of the current information it provides to the control system as an “eye”.

Precision is the core: High-precision, low-temperature drift current sensors are the key to ensuring:

1.The power conversion module operates at the optimal efficiency point (reducing conversion losses).

 

2.Power devices operate in a safe and efficient range (avoiding excessive losses).

 

3.The cooling system works precisely as required (not over-consuming auxiliary energy while fully ensuring heat dissipation).

 

 

 

Reliability foundation: Accurate current measurement is also the basis for functions such as overcurrent protection and short-circuit protection to prevent thermal runaway caused by catastrophic failures.

 

 

 

Suggestions for charging pile designers:

 

 

1.Accuracy and temperature drift priority: Select high-precision, low-temperature drift current sensors (such as closed-loop Hall sensors, high-precision low-resistance Shunt + precision op amps) at key power measurement points (such as module input/output, battery-side output).

 

2.Weigh power consumption: In high current paths, give priority to low-power magnetic sensors (such as Hall and Rogowski coils) to minimize self-heating. If a Shunt must be used, be sure to select a product with extremely low resistance and sufficient power margin, and optimize its heat dissipation design.

 

3.Focus on bandwidth: Ensure that the sensor’s bandwidth and response time meet the requirements of the power switching frequency and control loop.

 

4.Temperature compensation: For applications with extremely high accuracy requirements, consider using sensors with temperature compensation functions or implementing software temperature compensation in the control algorithm.

 

5.Calibration and maintenance: During production and post-maintenance, necessary calibration is performed to ensure long-term accuracy.

 

 

 

In summary, although the heat generated by the current sensor itself may not be the largest heat source in the system, its measurement accuracy and stability are the key prerequisites for ensuring the efficient operation of the charging pile power conversion module and the precise operation of the thermal management system. Improper selection or insufficient performance of the current sensor will significantly increase system losses, reduce overall thermal efficiency, and may cause reliability issues.

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