How do you calculate the efficiency of a switching converter?

2 Losses and components

The efficiency of a switching converter is not static and can be affected by several factors, such as the switching frequency, the load current, the temperature, and the quality of the components. Conduction losses are caused by the resistance of wires, switches, and inductors, and increase with the load current and temperature. Switching losses are triggered by the transitions between on and off states of the switches, while leakage losses are caused by parasitic capacitance and inductance of components. Quiescent losses arise from power consumption of the control circuit and feedback network. To enhance efficiency, you can select low-resistance switches, low-loss inductors, high-frequency capacitors, and optimized control and feedback circuits.

3 Measurement and simulation

To calculate the efficiency of a switching converter, you can either measure it or simulate it. Measuring the efficiency requires a power source, a load, a multimeter, and an oscilloscope. You need to measure the input and output voltages and currents at different load conditions and calculate the efficiency using the formula. You also need to measure the switching waveforms and check for any anomalies or noise.

Simulating the efficiency requires a circuit design software, such as LTspice, PSpice, or Simulink. You need to create a schematic of the switching converter, including the components values and models, and run a simulation with different input and output parameters. You can then plot the efficiency curve and analyze the losses and waveforms.

4 Efficiency standards and regulations

The efficiency of a switching converter is not only important for performance and reliability, but also for compliance with standards and regulations. Depending on the application and the market, there may be different requirements for the minimum efficiency, the power factor, the harmonic distortion, and the standby power. For example, the Energy Star program sets standards for the efficiency of various electronic products, such as computers, monitors, printers, and televisions. The IEC 61000-3-2 standard sets limits for the harmonic current emissions of electronic equipment. The European Union's Ecodesign Directive sets requirements for the energy efficiency and environmental impact of electronic products.

To meet the standards and regulations, you may need to design your switching converter with additional features, such as power factor correction, active or passive filtering, or standby power reduction.

5 Tips and tricks

To increase the efficiency of your switching converter, consider employing synchronous rectification instead of diode rectification, as this will reduce conduction and reverse recovery losses. Additionally, you can apply soft switching techniques, such as zero-voltage or zero-current switching, to reduce the overlap between voltage and current during transitions. Furthermore, you can adjust the switching frequency or duty cycle according to the load current, which will reduce both switching and quiescent losses at light loads. Finally, a multi-stage or multi-output switching converter can reduce the input voltage or output voltage difference, resulting in lower conduction and switching losses.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?