The Problem :

Switched-mode power supplies (SMPS) are incredibly efficient but often introduce high-frequency noise on the input side. This noise can interfere with nearby sensors, microcontrollers, or wireless modules, leading to unstable performance in your projects.

The Solution :

To fix this, add input filtering components such as ferrite beads, X/Y capacitors, and common-mode chokes. These components help block or absorb the high-frequency noise, ensuring your SMPS runs cleanly and quietly.

Practical Example :

Say you’re powering a Wi-Fi-enabled IoT device using a 12V SMPS. Without input filtering, the power supply’s switching noise can interfere with your Wi-Fi module’s signal strength or ADC readings. Adding a ferrite bead (100Ω@100MHz) and 0.1µF ceramic capacitor across input lines significantly reduces the noise.

Sample Calculation :

A pi-filter can be designed using:

• C1 = 0.1µF (ceramic)

• L = 100µH inductor

• C2 = 100µF (electrolytic)

• This suppresses frequencies above a few hundred kHz, cleaning up your input line.

Product Suggestion :

Look for ferrite beads or ceramic capacitors made in India:

Ferrite Bead

Ceramic Capacitor

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