In electronic devices, the stability of the power supply is crucial, and the ripple and noise in the power supply will affect the performance of the device. Choosing a suitable power filter is the key to reducing ripple and noise. The following are the key points to consider when choosing:

Understand the type of power supply noise

Power supply noise is mainly divided into common mode noise and differential mode noise. Common mode noise is the noise between the power line and the ground, and differential mode noise is the noise between the power lines. Different filters have different suppression capabilities for these two types of noise, and they need to be selected according to the actual application.

Noise frequency range: Determine the noise frequency that needs to be filtered out. Power supply noise is usually divided into low frequency (50/60 Hz and its harmonics) and high frequency (high frequency noise generated by switching power supplies).

Noise type: Distinguish between common mode noise (existing between all wires and ground) and differential mode noise (existing between wires).

Choose a suitable filter circuit

Power supply filters are usually composed of inductors and capacitors. Their goal is to suppress high-frequency noise through low-pass filtering characteristics. For low-impedance noise sources, the filter should use a high-impedance series inductor; for high-impedance noise sources, a low-impedance parallel capacitor should be used.

Low-pass filter: suitable for filtering high-frequency noise and retaining low-frequency signals.

Common-mode filter: specifically suppresses common-mode noise.

Differential-mode filter: specifically suppresses differential-mode noise.

Pay attention to insertion loss and key parameters

Insertion loss measures the filter's ability to attenuate noise of a specific frequency. When selecting, a filter with high insertion loss should be selected based on the noise frequency range of the power supply.

Cut-off frequency: select a cut-off frequency lower than the noise frequency.

Insertion loss: The greater the insertion loss, the better the filtering effect.

Rated current and voltage: ensure that the filter can withstand the maximum current and voltage of the circuit.

Impedance matching: The filter should match the power supply and load impedance to achieve the best effect.

Consider rated current and ambient temperature

The rated current of the filter usually refers to the maximum operating current at room temperature. In practical applications, it is necessary to select a suitable filter based on the maximum operating current and ambient temperature of the power supply to avoid performance degradation due to excessive current or high temperature.

Temperature range: Ensure that the filter can operate normally within the operating temperature range.

EMC standard: Select a filter that meets the relevant electromagnetic compatibility standards.

Optimize filter installation

The filter should be installed on the rack or housing of the equipment to ensure that the grounding wire is short to reduce the impact of high-frequency attenuation. The input end is connected to the power supply and the output end is connected to the equipment to ensure the filtering effect.

Close to the noise source: The filter should be installed as close to the noise source as possible.

Short connection line: Reduce the length of the connection line to avoid introducing additional noise.

Good grounding: Ensure that the filter is well grounded, especially the common mode filter.

Actual test: After installation, test the filtering effect through an oscilloscope or spectrum analyzer to ensure that it meets the requirements.

Regular maintenance and inspection

Clean the filter regularly to avoid dust accumulation, check the hardware status, and replace damaged parts in time to ensure continuous and effective operation.

Through the above points, the stability and reliability of the power supply can be effectively improved, providing protection for the normal operation of electronic equipment. The selection of a suitable power filter requires comprehensive consideration of noise type, frequency range, filter parameters, installation method and environmental factors, and the effect should be verified through actual testing.