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What are the filter considerations?
Sep 03, 2017



What are the filter considerations?


The filter is divided into analog filter and digital filter according to the processed signal. It is divided into low-pass, high-pass, band-pass and band-stop filters according to the frequency band of the signal to be passed. There are two kinds of passive and active filters, so there are many kinds of filters. Here, we will introduce them to you. The power filters and signal filters are commonly used in equipment. The choice of filter needs to consider the following four points:

1, current

The current specification is critical, which determines the wire diameter of the winding copper and lead wires of the inductor inside the filter. If the selection is fine, running a large current on the thin wire, such as a small horse-drawn cart, will cause severe heat and even burn. This current is also a range, the steady state current + the maximum value of the fluctuating current.

2, voltage

This voltage value requirement is a range and is a combination of steady-state voltage ± ripple voltage.

3. Electromagnetic compatibility standard requirements

Since it is a filter, it is to filter out some undesired frequency bands, and the filtering effect is generally determined by the visual results of EMC test standards and field applications. In particular, the power filter, it is best to determine which standard is required to pass the product of this filter, according to the different requirements of the standard, there are also specific test frequency requirements when selecting. The main targets of the power filter are conducted emission CE and conducted interference suppression CS. The signal filter mainly depends on the requirements of the undesired input frequency band and the undesired output frequency band in the EMC standard. For example, the rectifier for the electrodeless lamp itself is a switch working state, there will be external emission, and the EMC test will focus on checking the switching frequency and the conduction interference of its higher harmonic components. The filter needs to be specific to these specific frequency bands or frequencies. The dots have sufficient filtering effect.

4. Safety standards requirements

You may find it strange to choose a filter and say that the safety standards are dry? This is because the filter is generally used at the input of the power supply and the interface of the board. These parts are the hardest hit areas of safety problems. It is equal to the filter that bears multiple requirements. The safety related to the filter is focused on three indicators: insulation withstand voltage, leakage current, residual voltage residual energy.


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