Switch Mode Power Supplies (SMPS) are compact and efficient—but they’re also notorious for generating input noise. For electronics hobbyists and engineers in India, ignoring this noise can lead to malfunctioning sensors, display glitches, or even EMI compliance issues. Luckily, you can fix it with a simple input noise filter.

🔧 The Problem: Noisy Power Lines

SMPS circuits switch rapidly, creating high-frequency noise that travels back into the power line. This can interfere with nearby sensitive circuits or cause erratic behavior in microcontroller-based designs.

✅ The Solution: Add an Input Filter

The most common fix is to add a π (pi) filter at the input, using inductors and capacitors. This helps suppress high-frequency noise and smooth out the input voltage.

🔍 Practical Example: Powering a Microcontroller

Say you’re using an SMPS to power a development board with sensors. The sensors behave unpredictably. By adding a 100µH inductor and two 100nF ceramic capacitors (one before and one after), you stabilize the input and eliminate the noise.

🧮 Sample Calculation: Filter Cutoff Frequency

Using:
L = 100µH
C = 100nF

fc = 1 / (2π√LC) = ~50kHz
This means noise above 50kHz gets filtered out—perfect for typical SMPS ripple.

🛒 Product Suggestion: Made in India Components

• 🔌 [Shop ceramic capacitors]

• ⚙️ [Shop power inductors]

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