A flyback converter uses a magnetic component to temporarily store energy from the input side before it is transferred to the output. This transfer of energy from the input occurs when the switch is closed and current is built up in the primary winding of the gapped transformer. During this time the output diode blocks any current flow in the secondary winding. The energy is stored in the magnetic field of the transformer. In this applet as the magnetic stored energy builds up the colour of the transformer core changes. With a gap in the transformer core it can be seen that most of the energy is stored in the air-gap. 

When the switch is opened the voltage on the secondary winding reverses and current is now conducted through the diode to the output. Therefore the stored energy is transferred to the output side.

• Change the length of the air gap to see the influence on the current waveforms and the amount of stored magnetic energy.
• Change the number of turns on the primary (switch) winding. A smaller number of turns results a lower inductance and the current can increase more quickly in the winding for a given input voltage.
• Change the number of turns on the secondary winding.
• Use the red time line to see how the current in the circuit changes during the operation of the flyback converter.
• By adjusting the number of turns on both sides of the transformer and the gap, it is possible to get the flyback to move from discontinuous current operation to continuous current operation. Discontinuous current operation is when all of the energy is removed from the transformer core before the switch is turned on again. This can be observed when the secondary current reaches zero and the output diode turns off.