The current sensor itself is not the main noise source of the charging pile (such as the cooling fan or magnetic component howling), but it is crucial to achieve efficient and smooth power conversion control, and an excellent control strategy is precisely one of the key means to suppress noise (especially the howling of magnetic components). Therefore, the current sensor indirectly but effectively suppresses noise by enabling advanced control algorithms.

 

 

Here are some specific ways that current sensors can help suppress noise by improving control performance:

 

 

1.Achieve precise soft switching technology:

Problem: Hard switching (such as traditional PWM) will generate very high dv/dt and di/dt at the switching moment, resulting in strong electromagnetic interference and device stress, and aggravating the vibration and howling of magnetic components.

 

Solution: Soft switching topologies such as LLC resonance and phase-shifted full-bridge need to turn on or off the switch tube at a precise moment (such as current zero crossing or voltage valley) to achieve zero voltage switching or zero current switching, significantly reducing switching stress and noise.

 

The role of the current sensor: Accurate, fast and real-time detection of the resonant current or the primary/secondary current of the transformer is the basis for achieving this precise timing control. Without accurate current information, the controller cannot determine the best switching time, and the soft switching effect will be greatly reduced or even fail, resulting in increased switching noise, which may in turn excite stronger vibration and howling of the magnetic components.

 

 

 

2.Support variable frequency/jitter frequency control:

Problem: When the switching frequency or its harmonics fall into the audio range (typically a few hundred Hz to a few kHz), magnetic components (especially inductors) will produce a noticeable and annoying single-frequency whine due to the magnetostrictive effect.

 

Solution: Frequency conversion control or frequency jittering technology actively and regularly fine-tunes the switching frequency, dispersing the switching energy originally concentrated at a single frequency point to a wider frequency band. This makes the energy at any single frequency point lower than the hearing threshold of the human ear or difficult to cause strong resonance of the component.

 

The role of current sensors: Variable frequency/jittering control usually requires stable current closed-loop control as support to ensure the stability and dynamic response of the output current/voltage when the frequency changes. The current sensor provides a critical closed-loop feedback signal, enabling the controller to accurately adjust the duty cycle or other parameters while the frequency changes to maintain stable system operation. Stable control is the prerequisite for effective frequency jittering.

 

 

 

3.Optimize current waveform and reduce harmonics and oscillations:

Problem: Current waveform distortion (such as overshoot, oscillation, distortion) will contain abundant high-frequency harmonic components. These high-frequency energies can easily excite the oscillation of parasitic parameters in the circuit (such as PCB trace inductance, device parasitic capacitance), and may couple to magnetic components, exacerbating their vibration noise.

 

Solution: High-performance current closed-loop control (such as peak current mode and average current mode control) can accurately track the current command and produce a smoother and less distorted current waveform.

 

The role of the current sensor: It is the core feedback element for realizing current closed-loop control. The high-precision, low-latency, and wide-bandwidth current sensor enables the controller to quickly detect small deviations in the current and correct them in time, thereby obtaining a cleaner and more sinusoidal current waveform, reducing high-frequency oscillations and harmonics, and indirectly reducing the noise caused by them.

 

 

 

4.Improve overall system efficiency and thermal management, indirectly reducing fan noise:

Problem: Imprecise control (such as large switching losses, increased conduction losses, and harmonic losses) will lead to reduced system efficiency, generate more heat, and force the cooling fan to run at a higher speed, causing greater wind noise.

 

Solution: Accurate current control is the core of efficient power conversion. Soft switching technology can significantly reduce switching losses. Optimized current waveform can also reduce conduction losses and harmonic losses.

 

The role of current sensors: By supporting soft switching, optimizing waveforms, and achieving precise power management and protection, current sensors help the system operate at a higher efficiency. Improved efficiency means less heat generation, and the cooling fan can meet the cooling requirements at a lower speed, thereby significantly reducing fan noise.

 

 

 

 

Key requirements for current sensors (to achieve noise reduction related control):

 

High precision: ensure the accuracy of control.

 

Low noise/low ripple: The output noise of the sensor itself should be small to avoid introducing false signals that interfere with control.

 

Wide bandwidth: Able to respond quickly to current changes (especially for high-frequency switching and resonant current detection) to meet the needs of soft switching and high-speed closed-loop control. Insufficient bandwidth will cause detection delays, affecting control effect and stability.

 

Low latency/fast response time: The time from when the current changes to when it is reflected in the sensor output signal must be extremely short, which is critical for high-frequency switching control.

 

Good Linearity and Temperature Stability: Maintains measurement accuracy over the entire operating current range and temperature range.

 

High common-mode rejection ratio: For sensors that detect floating potential current (such as using isolated sensors to detect switch tube current), it is necessary to effectively suppress common-mode voltage interference.

 

Commonly used current sensor types and their applicability:

 

 

1.Shunt:

For example, our FL series

Advantages: low cost, high accuracy, extremely high bandwidth, fast response.

 

Disadvantages: Conduction losses (especially at high currents), requires isolation, susceptible to parasitic inductance (may cause voltage spikes and measurement errors).

 

Noise reduction correlation: Ideal for applications requiring extremely high bandwidth and speed, such as high-frequency switch current sensing (for soft switching control, peak current control).

 

 

 

2.Current transformer:

For example, our split core current transformer KCT series

Advantages: natural isolation, no conduction loss, can measure large current, moderate cost.

 

Disadvantages: Only suitable for AC or pulse current (cannot measure DC component), there are saturation problems, bandwidth is limited by the core material (may be insufficient at high frequencies), relatively large size.

 

Noise reduction correlation: Commonly used to detect high-frequency AC components of AC side current, resonant current, or primary/secondary side of transformer. Bandwidth is a key consideration for high-frequency control.

 

 

 

 

3.Fluxgate Current Sensor:

For example, our HYCA series

Advantages: ultra-high precision, extremely low temperature drift, low noise, high linearity, measurable AC and DC, isolation.

 

Disadvantages: Highest cost, relatively low bandwidth (usually lower than Hall), more complex circuit.

 

Noise reduction correlation: It is suitable for occasions with extremely high requirements for accuracy and stability (such as precision measurement and metering). In general noise reduction control, it may have excessive performance and uneconomical cost.

 

 

 

 

4.Rogowski coil:

For example, our FRC series

Advantages: No magnetic saturation problem, extremely high bandwidth (up to MHz level), can measure extremely large di/dt current, non-contact (but usually needs to be put on the conductor).

 

Disadvantages: only measures AC components, output is a differential signal that needs to be integrated, sensitive to environmental magnetic fields, poor low-frequency accuracy, and may be large in size.

 

Noise reduction correlation: Mainly used for pulse current measurement or fault diagnosis with extremely high frequency and extremely large di/dt, and is rarely used in conventional charging pile power control.

 

 

 

 

Summarize:

The current sensor itself does not directly “suppress” noise, but it is the indispensable “eyes” and “ears” for achieving **advanced, precise, and efficient power conversion control**. By providing **high-precision, high-bandwidth, low-latency** current feedback information to the controller, the current sensor enables:

 

 

1.Accurate soft switching control becomes possible, significantly reducing switching noise and stress.

 

2.Effective frequency conversion/frequency jittering control is implemented to disperse the switching energy and eliminate single frequency howling.

 

3.Optimized current waveform control is achieved, reducing harmonics and oscillations.

 

4.The overall system efficiency is improved, heat generation is reduced, and the fan can run at a lower speed.

 

 

Therefore, selecting a current sensor with matching performance (especially accuracy, bandwidth, and response speed) and cooperating with an optimized control algorithm is a crucial part of a comprehensive charging pile noise suppression solution, especially in solving the howling of magnetic components and improving efficiency to reduce fan noise.

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