Switch Mode Power Supplies (SMPS) are popular in electronics for their efficiency—but they often suffer from unstable output if not designed carefully. Let’s walk through the common issue and how to fix it with an easy-to-follow example, calculation, and some Made in India component suggestions.

🛠️ The Problem: Unstable SMPS Output

Unstable output voltage in an SMPS can lead to flickering LEDs, resetting microcontrollers, or erratic motor performance. This typically happens due to poor feedback loop design or insufficient filtering at the output. Hobbyists often overlook these during prototyping, leading to frustrating results.

✅ The Solution: Proper Feedback and Decoupling

To fix instability, ensure a well-designed feedback resistor divider and add decoupling capacitors (typically 100µF electrolytic + 0.1µF ceramic) at the output. Also, place small ceramic capacitors close to your ICs to suppress high-frequency noise.

🔍 Practical Example: Servo Motor Glitch Fix

A hobbyist in Pune noticed random twitching in a servo motor driven by a 5V SMPS. After adding a 6.8kΩ resistor in the feedback loop and a 100µF capacitor at the output, the servo ran smoothly—no flicker, no noise. Simple tweaks, big results!

📐 Sample Calculation: Setting 5V Output

For an SMPS controller with a 1.25V reference:

Let R1 = 2.2kΩ

Vout = 1.25V × (1 + R2/R1)

5V = 1.25 × (1 + R2/2200)

Solving: R2 ≈ 6.6kΩ → use standard 6.8kΩ

This sets the SMPS to output a stable 5V.

🧰 Product Suggestion: Use Quality Made in India Components

Choose reliable MOSFET drivers or flux for clean solder joints and proper switching performance. Using Made in India components ensures compatibility and supports local innovation.

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