Flywheel diodes are usually used with energy storage elements to prevent sudden changes in voltage and current and provide a path. Inductor can provide continuous current to the load through it, avoid sudden change of load current and smooth the current! In the switching power supply, you can see a free-wheeling circuit consisting of a diode and a resistor in series. The circuit is connected in parallel with the primary side of the transformer. When the switch tube is turned off, the freewheeling circuit can release the energy stored in the transformer coil to prevent the switch tube from being damaged due to excessive induced voltage. Generally, a fast recovery diode or Schottky diode can be used to convert the reverse potential generated by the coil. It can be seen that "free-wheeling diode" is not a substantial component, but its function in the circuit is called "free-wheeling".