The Problem :

Power supplies are at the heart of any electronic project, but they often come with their own set of challenges—especially when working with Switched-Mode Power Supplies (SMPS). As hobbyists and engineers, troubleshooting an SMPS can be daunting, but understanding the basic issues and how to fix them will make a huge difference.

The Solution :

One of the most common problems with SMPS is failure to output stable voltage. This often happens because of faulty capacitors, incorrect resistor sizing, or overheating components. To troubleshoot, start by checking the input and output voltages with a multimeter. If there is no output, the issue could be a damaged MOSFET or capacitor. Replace these components carefully, ensuring they are correctly rated.

Example :

Let’s say you’re powering an LED circuit from an SMPS, but the LED keeps blinking instead of staying lit. This could be due to improper voltage regulation. Use a multimeter to check if the output is consistent with the voltage required for your LED. If it’s fluctuating, a faulty feedback loop or capacitor might be the culprit. Replace any suspect components and retest.

Sample Calculation : 

Let’s calculate the current-limiting resistor needed for a 5V SMPS powering a 20mA LED.

Using Ohm’s law (V = IR), we find:

R = V/I = (5V – 2V) / 0.02A = 150 ohms

So, a 150-ohm resistor will ensure your LED receives the proper current.

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