How can you design a flyback converter for a power supply?

1 Choose the topology

The first step is to choose the appropriate topology for your flyback converter, depending on your input and output specifications, such as voltage, current, power, isolation, and regulation. There are two main types of flyback converters: single-ended and double-ended. A single-ended flyback converter uses one switch and one diode, while a double-ended flyback converter uses two switches and two diodes. The single-ended topology is simpler, cheaper, and more efficient, but it has higher peak currents and voltage stresses. The double-ended topology has lower peak currents and voltage stresses, but it is more complex, expensive, and less efficient.

2 Design the transformer

The second step is to design the transformer, which is the key component of the flyback converter. The transformer transfers energy between the primary and secondary windings through a magnetic core, and provides isolation and voltage transformation. To design the transformer, you need to determine the following parameters: the turns ratio, the core size and material, the air gap, the winding wire gauge and layout, and the leakage inductance. The turns ratio depends on the input and output voltages and the duty cycle of the switch. The core size and material depend on the power rating, the operating frequency, and the core losses. The air gap affects the magnetizing inductance, which determines the peak current and the energy storage. The winding wire gauge and layout affect the winding resistance, which determines the conduction losses and the efficiency. The leakage inductance affects the voltage spikes and the snubber circuit.

3 Select the components

The third step is to select the components that make up the rest of the flyback converter circuit, such as the switch, the diode, the capacitor, the resistor, and the feedback network. The switch controls the energy transfer between the primary and secondary windings, and it should have a low on-resistance and a high breakdown voltage. The diode rectifies the output voltage and should have a low forward voltage drop and a fast recovery time. The capacitor filters the output voltage and should have a low equivalent series resistance (ESR) and a high ripple current rating. The resistor sets the output voltage by forming a voltage divider with the feedback network. The feedback network regulates the output voltage by adjusting the duty cycle of the switch through an optocoupler or a transformer.

4 Simulate and test

The fourth step is to simulate and test your flyback converter design, using software tools or hardware prototypes. Simulation can help you verify your design parameters, optimize your performance, and identify potential issues, such as instability, overshoot, undershoot, ringing, noise, and thermal stress. Testing can help you validate your simulation results, measure your actual performance, and troubleshoot any problems, such as poor regulation, low efficiency, high ripple, or component failure. You should use proper equipment and procedures, such as oscilloscopes, multimeters, load banks, and safety precautions, to conduct your simulation and testing.

5 Evaluate and improve

The fifth step is to evaluate and improve your flyback converter design, based on your simulation and testing results and your design objectives. You should compare your output voltage, current, power, efficiency, ripple, and transient response with your specifications, and check if they meet your requirements and expectations. You should also analyze your component stresses, losses, and temperatures, and check if they are within your limits and tolerances. If you find any discrepancies or issues, you should modify your design parameters, components, or circuit, and repeat the previous steps until you achieve your desired performance and reliability.

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?