How to select the right EMI filter for the power supply of an HMI (Human Machine Delivery System)?

The selection of an HMI power supply EMI filter needs to be determined comprehensively based on the system power supply specifications, the interference frequency bands to be suppressed, and the installation space. First, clarify the power supply type, such as single-phase AC 220V, DC 24V, or wide-voltage DC input. For AC input, a complete filter including safety-certified X capacitors, Y capacitors, and a common-mode inductor should be selected. Its rated current should be greater than 1.5 times the system's maximum operating current. For example, the CMZ7060A series filter can be selected, as its high common-mode impedance effectively suppresses low-frequency conducted emissions. For DC input, differential-mode noise is the primary consideration. A π-type or T-type filter circuit can be selected, consisting of a power inductor and capacitor.

The inductor value is calculated based on the switching power supply frequency and the frequency points to be attenuated. The capacitor's withstand voltage and ripple current must be considered. The resonant frequency of the filter components should avoid the system's operating frequency and switching frequency to prevent resonant amplification of noise. During installation, the filter should be placed as close as possible to the power input, input and output cables should be routed separately, and the filter's metal casing should be connected to the chassis with low impedance. Yinte Electronics offers CMZ series AC filters and PBZ series power beads. Based on the specific test spectrum exceeding the standard point, the model with the best attenuation characteristics in the corresponding frequency band can be selected to achieve precise filtering.