The power line filter is a common electronic component, and its main role is to filter and denoise the regulated power supply or AC signal from the power supply. Its structure is composed of an inductor and a capacitor in parallel, through which the power supply noise and interference can be well eliminated, and the stability and reliability of the circuit can be improved.
First, the principle of power filter.
The operation of the power line filter is based on a low-pass filter circuit composed of inductance and capacitance in parallel, which can effectively filter high-frequency noise. At the input end, when the ripple voltage of the power supply passes through the inductance of the saturated core core, it will form an output current in the opposite phase to the input, which will have a canceling effect, thereby reducing the effect of power clutter propagating into the subsequent circuit.
Second, the main function of the power filter.
The main functions of the power filter, in summary, can also be summarized as follows:
1. Solve the problem of high-frequency harmonic interference, including the harmonic in the power supply and the series of harmonic interference caused by the high-frequency harmonic generated by the harmonic source such as the inverter and servo during operation.
2. Improve the anti-interference ability of the system using power filters. The power filter has a bidirectional filtering ability, which can effectively improve the anti-interference ability of the system using the power filter.
3. Reduce THD content. Power filters have a certain harmonic rejection capability that can significantly reduce the THD value of the system (of course, it is not possible to achieve a THD of 5% or 10% for the system).
4. Pass EMC testing. Many standards or certifications have EMC testing items, and power filters are an important tool that can help the system successfully pass EMC testing.
3. Classification of power filters.
1. According to the signal processed:
There are two types of filters: analog filters and digital filters.
2. According to the frequency band of the signal passed:
Low-pass filter: It allows the passage of low-frequency or DC components in the signal, suppressing high-frequency components or interference and noise;
High-pass filter: It allows the passage of high-frequency components in the signal, suppressing low-frequency or DC components;
Bandpass filter: It allows signals in a certain frequency band to pass through, suppressing signals, interference, and noise below or above that frequency band;
Band Stop Filter: It suppresses signals within a certain frequency band, allowing signals outside of that band to pass through.
Fourth, the characteristics of the power filter.
The main characteristics of power filters can be summarized into the following four aspects:
1. Suppress high-frequency harmonics.
2. Suppress conducted harmonics and radiated harmonics.
3. Suppress differential mode harmonics and common mode harmonics.
4. Improve the safety, stability and reliability of the system using power filters.