What are the specific requirements for the performance of SQ type flat wire common mode filters?
Publish Time: 2024-08-21
The performance requirements of SQ type flat wire common mode filters usually include the following aspects:
Electrical performance:
High impedance: It should present high impedance in the common mode frequency range to effectively suppress common mode noise signals. For example, for common electromagnetic interference frequencies, such as 50Hz - 1GHz, it can maintain a high impedance value, thereby limiting the common mode interference current to a low level.
Low differential mode loss: The loss of differential mode signals should be as low as possible to ensure normal signal transmission quality. The attenuation of differential mode signals should be controlled within a very small range. For example, at a specific frequency, the differential mode attenuation does not exceed 0.5dB.
Good frequency characteristics: Within the operating frequency range, the performance is stable, including parameters such as impedance and attenuation should not fluctuate violently with frequency changes. For example, in the frequency range of 100kHz - 500MHz, the changes in various performance indicators should be within an acceptable range to meet the processing requirements of different frequency signals in different application scenarios.
Filtering effect:
High common mode rejection ratio (CMRR): can significantly reduce the amplitude of common mode interference signals. Usually, the CMRR value is required to reach a high level, such as above 60dB, or even higher, so as to suppress common mode noise to an extremely low level and ensure the normal operation of equipment or systems.
Targeted suppression of specific frequency noise: For example, it has good suppression ability for 50Hz power frequency interference and its harmonics on the power line, or high-frequency noise in high-speed digital signals, so that the noise components of these specific frequencies in the signal after the filter are greatly reduced.
Inductance characteristics:
Suitable inductance: According to the specific application requirements and circuit design, it has a matching inductance. The size of the inductance will directly affect the filter's suppression effect on common mode signals and the degree of influence on differential mode signals, generally between a few microhenries and tens of millihenries.
Low leakage inductance: The leakage inductance should be as small as possible to avoid adverse effects on circuit performance, such as signal distortion, additional electromagnetic interference, etc. The leakage inductance value is usually required to be controlled within a certain proportion of the main inductance, such as less than 5%.
Current carrying capacity: It can withstand the expected working current in the circuit, and will not overheat or burn when a large current passes through. For example, for some common-mode filters in high-power devices or systems, it may be necessary to be able to carry 10A or even higher current.
Temperature stability: Under different operating temperature environments (such as -40℃ to +85℃), the performance remains stable, including the changes in parameters such as inductance, impedance, and filtering effect within the allowable range to ensure reliable operation under various environmental conditions, and the filter performance will not fail or deteriorate due to temperature changes.
Mechanical structure and size:
Compact size: To meet the space restrictions of the device or system, especially in some miniaturized and integrated electronic devices, the SQ type flat wire common mode filter needs to have a smaller volume, such as using flat wire winding and other technologies to reduce the size.
Solid structure: It has sufficient mechanical strength and stability to withstand external forces such as vibration and impact during installation and use without deformation or damage, ensuring long-term reliable operation.
Reliability and durability: It has a long service life. After long-term use, the performance can still meet the requirements. For example, within the prescribed service life, the attenuation of various performance indicators does not exceed a certain proportion. At the same time, it must have good anti-aging and anti-corrosion properties to adapt to different working environments.
