The Problem: Understanding MOSFET Switching Losses

While MOSFETs are popular for their high efficiency, switching losses can significantly heat up your circuit, especially in high-frequency applications like buck converters or motor drivers. Ignoring these losses can lead to overheating, reduced efficiency, or circuit failure.

The Solution: Minimize Switching Time & Gate Drive Impedance

Switching loss mainly occurs during transitions when both voltage and current briefly overlap. To reduce it:

• Use a MOSFET with low gate charge (Qg)

• Drive it fast using a suitable gate resistor (too large = slow, too small = noisy)

• Consider MOSFET driver ICs for high-speed applications

Practical Example: DC Motor PWM Control

Say you’re switching a 12V DC motor at 20kHz. A slow gate drive results in long transition times (~200ns), causing heat. Using a fast gate driver and tuning the gate resistor helps reduce transition to ~50ns, cutting losses by up to 75%.

Sample Calculation: Switching Loss Estimate

Switching Loss (Psw) = 0.5 × V × I × (ton + toff) × f

If V = 12V, I = 2A, ton+toff = 100ns, f = 20kHz

Psw = 0.5 × 12 × 2 × 100e-9 × 20e3 = 24mW

It adds up in continuous use!

Product Suggestions: Made in India Components

• MOSFET Low Rds(on)

• Gate Driver IC

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