SMPS Efficiency Guide
An SMPS efficiency check compares useful output power with power taken from the source. The result shows how much energy becomes regulated output. It also shows how much energy becomes heat inside switches, diodes, magnetic parts, and control circuits.
Why Efficiency Matters
A high efficiency converter wastes less energy. It runs cooler. It can use smaller heatsinks. It also improves battery life and lowers running cost. Low efficiency may point to poor layout, overloaded parts, bad switching frequency, or weak rectification. The best value depends on topology, input range, output current, and safety margin.
Measured Method
The most direct method uses real bench data. Measure input voltage, input current, and power factor when the source is AC. You may also enter measured input power from a wattmeter. Then measure each output rail under the same load condition. The calculator multiplies voltage by current for every output. It adds the rails and divides total output power by input power.
Loss Model Method
A loss model is useful during design. Add switching loss, conduction loss, magnetic loss, rectifier loss, driver loss, controller loss, and other losses. The calculator adds these losses to output power. It then estimates input power and model efficiency. This helps compare MOSFETs, diodes, inductors, transformers, and thermal choices before hardware is ready.
Thermal View
Efficiency is closely linked to temperature. Every wasted watt becomes heat. This tool converts measured loss into BTU per hour. It can also apply a simple temperature derating above 25 °C. The correction is not a replacement for testing. It only gives a quick view of hot operating conditions.
Good Testing Practice
Use calibrated meters when possible. Keep the same load during all readings. Let the supply warm up before recording final values. Test at light load, half load, full load, low input, nominal input, and high input. Record ripple and temperature separately. Do not judge a converter from one operating point only. A complete table gives a clearer design decision.
Design Notes
Small changes can matter. Better copper width reduces conduction loss. Faster switches can lower overlap loss. They may increase ringing. Synchronous rectification helps low voltage rails. Good magnetics reduce core heating. Always balance efficiency with cost, size, noise, reliability, and goals.