As a key electronic component, the power filter plays a vital role in the power system. It reduces noise interference on the power line through impedance matching to ensure the purity and stability of the power signal. Power filters are not only widely used in household electricity and small industrial equipment, but also play an important role in high-power power supply occasions, such as inverters, UPS, etc., as well as complex commercial power occasions. This article will explore in depth the targeting of power filters to different types of power interference, including its adaptability to linear regulated power supplies and switching regulated power supplies, as well as the filtering effect on common mode noise and differential mode noise.

Basic principles and classification of power filters

The power filter is essentially an impedance adaptation network that filters out interference signals on the power line through components such as inductors and capacitors. Depending on whether an external power supply is required, power filters can be divided into two categories: passive filters and active filters. Passive filters mainly rely on components such as inductors and capacitors to filter out interference. They have the advantages of simple structure, low cost, and easy maintenance, but the filtering effect is relatively limited. In addition to components such as inductors and capacitors, active filters also require external power supply, which can generate corresponding reverse harmonic currents according to the harmonic frequency of the power grid to offset the harmonic components, thereby achieving a more efficient filtering effect.

Adaptability of power supply filters to linear regulated power supplies

Linear regulated power supplies have been widely used in small electronic devices and precision instruments due to their minimal peripheral components, minimal output noise, and minimal static current. However, in practical applications, linear regulated power supplies may still be interfered by common-mode and differential-mode noise from the power grid. The power supply filter effectively suppresses these noises through its internal capacitors and inductors.

▶ Suppression of common-mode and differential-mode noise: Common-mode noise refers to noise with the same direction and similar amplitude that appears on two or more lines of the power line (such as the live wire and the neutral wire), while differential-mode noise mainly appears between different lines of the power line, manifested as noise with opposite directions and unequal amplitudes. The power supply filter can effectively suppress these two types of noise through its unique structure and design, ensuring the purity and stability of the power supply signal.

▶ Improve power quality: By connecting a power filter, the harmonic distortion and electromagnetic interference of the linear regulated power supply can be further reduced, thereby improving the overall quality of the power supply. This is especially important for precision instruments and equipment that require high-precision power supply.

▶ Protect load equipment: When voltage fluctuations or transient interference occur in the power grid, the filter can quickly respond and absorb these interference signals to avoid damage to the load equipment.

Adaptability of power filter to switching regulated power supply

Switching regulated power supply has been widely used in large industrial equipment and household appliances due to its high efficiency, low power consumption, and adjustable output voltage. Active filters have significant advantages in this regard and can effectively filter out high-frequency harmonic currents.

▶ Efficiently filter out high-frequency harmonics: The output voltage and current of the switching regulated power supply will fluctuate with the change of load, generating high-frequency harmonic currents. Active filters can accurately filter out these high-frequency harmonics to ensure the stability of the power supply signal.

▶ Dynamic response: Since the output voltage and current of the switching power supply fluctuate with the load, the power filter needs to have a fast dynamic response speed to quickly adapt to the load changes and maintain the stability of the power signal.

▶ Electromagnetic compatibility: The switching power supply may generate electromagnetic interference during operation, affecting the normal operation of other equipment. The power filter improves the electromagnetic compatibility of the equipment by filtering out the interference signal on the power line and ensures the stable operation of the system.

The targeting of the power filter to common-mode noise and differential-mode noise

The interference current on the power line is divided into common-mode interference current and differential-mode interference current according to its flow path. The power filter performs well in suppressing these two types of interference.

▶ Common-mode noise suppression: Common-mode noise is often generated by the internal circuit of the device and propagates to the external environment through the power line. The power filter effectively suppresses common-mode noise through its internal capacitor elements. These capacitor elements can absorb and filter out common-mode noise on the power line to protect the equipment from harm.

▶ Differential-mode noise suppression: Differential-mode noise is usually caused by interference signals at the input end of the power supply, such as harmonics and high-frequency noise in the power grid. The power filter can effectively filter out the differential mode noise on the power line through the internal differential mode filter circuit, and improve the purity and stability of the power signal.

Configuration strategy of power filter in multi-power system

In a multi-power system, it is crucial to configure the power filter to avoid mutual interference. Here are some effective configuration strategies:

▶ Avoid electromagnetic coupling: The input and output lines of the power filter should be kept at a certain distance and avoid parallel arrangement to reduce electromagnetic coupling.

▶Independent wiring: Try to configure an independent power filter for each power device, and ensure that its input and output lines are separated from the lines of other devices.

▶Common mode and differential mode filtering: Select filters that can suppress common mode and differential mode interference at the same time to effectively reduce interference between different power devices.

▶Active filter: For high power or multi-power systems, active filters can be considered, which can more effectively suppress harmonics and electromagnetic interference.

▶Grounding measures: Ensure that the grounding terminal of the power filter is well connected to the grounding system of the equipment to provide an effective interference discharge path.

▶Short ground wire: Try to use shorter ground wires to reduce ground inductance and resistance, thereby improving the common-mode suppression capability of the filter.

▶Shielded cable: Use shielded cables to connect power supply equipment and filters to reduce electromagnetic radiation and interference.

▶Isolation transformer: When necessary, an isolation transformer can be used to isolate different power supply systems to prevent electrical interference.

▶Check the filter status: Regularly check the hardware status of the power filter to ensure its normal operation. Replace loss parts in time to maintain the performance of the filter.

▶System test: Regularly perform electromagnetic compatibility tests to evaluate the performance of the filter and the overall interference of the system.

Through the above strategies, the power filter can be effectively configured to reduce mutual interference in the multi-power system and ensure the stable operation of the system.

Conclusion

As an indispensable component in the power system, the power filter is significantly targeted at different types of power interference. Whether it is a linear regulated power supply or a switching regulated power supply, the power filter can improve the power quality and protect the load equipment by suppressing common-mode and differential-mode noise. In a multi-power system, the reasonable configuration of the power filter is the key to ensure the stable operation of the system. By continuously optimizing the design and configuration strategies of filters, we can better cope with various interferences in the power system and provide strong guarantees for the normal operation of equipment.