What are typical SMPS advantages, disadvantages, and failure modes?

Typical SMPS advantages, disadvantages, and failure modes

Advantages

• High Efficiency: They waste very little power, making them ideal for energy-conscious applications like computers, servers, and battery chargers.
• Compact & Lightweight: Their small size makes them perfect for modern electronics where space is limited, such as laptops, smartphones, and flat-screen TVs.
• Wide Input Voltage Range: Most SMPS units can automatically adapt to different mains voltages around the world.

Disadvantages

• Electrical Noise: The internal switching generates high-frequency noise (Electromagnetic Interference - EMI) that can interfere with sensitive radio or audio equipment if not properly filtered.
• Complexity: The design is more complex than a linear supply, which can sometimes make troubleshooting and repair more difficult.
• Output Ripple: The output voltage has a small, high-frequency ripple, which may be unsuitable for extremely sensitive analog or scientific instruments without additional filtering.

Common Failure Modes

• Capacitor Failure: This is the most common cause of SMPS failure. Electrolytic capacitors, especially those on the input and output stages, degrade over time, particularly when exposed to heat. They can dry out, bulge, or leak, leading to unstable output or complete failure.
• Switching Transistor (MOSFET) Failure: The main switching component handles high voltage and current and can fail due to overheating or voltage spikes. This failure is usually catastrophic and often takes other components with it.
• Inrush Current Limiter Failure: When first turned on, an SMPS draws a large initial surge of current. A component (often a thermistor) is used to limit this surge. If this component fails, the supply may trip a circuit breaker or blow a fuse upon startup.