Switch-Mode Power Supply (SMPS) designs are essential in modern electronics, but improper PCB layout can lead to inefficiency, heat buildup, or noise issues. A key challenge many engineers face when working with SMPS is the placement of components on the PCB. Improper routing can cause voltage drops, reduce efficiency, or even damage sensitive parts. Fortunately, with a few guidelines, these issues can be easily fixed!

The Problem :

In an SMPS circuit, high-current paths must be kept short and thick to minimize losses. A common mistake is routing high-current traces near sensitive control signals, leading to electromagnetic interference (EMI). To fix this, keep the power and signal traces separate and use ground planes to reduce noise.

Practical Example:

Imagine you’re designing a PCB for a power supply that will be used in a home appliance. If you route the high-current traces near the microcontroller or sensor, EMI can corrupt their signals, making the appliance malfunction. By ensuring these traces are separated and creating a dedicated ground plane, you can significantly reduce noise, making the device more stable.

Sample Calculation:

Let’s calculate the required resistor value to limit current in an LED circuit powered by an SMPS. For a 12V SMPS and a 20mA LED:

  * Voltage across the resistor = 12V – 2V (LED forward voltage) = 10V.

    R=IV​=0.02A10V​=500Ω

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