This applet examines the operation of the flyback converter, and in particular the influence of the input voltage, switching frequency, duty cycle, and load resistance on the discontinuous current operation of the converter. Discontinuous current mode (DCM) operation occurs when all of the energy is removed from the transformer core before the switch is turned on again. This can be observed in the waveforms when the secondary current reaches zero and the output diode turns off. Continuous current mode operation (CCM) is when energy still remains in the transformer core when the switch is turned on again.

• Change the input voltage level. A higher voltage allows the primary transformer current to build up to a higher value before the switch is opened. This allows more energy to be stored in the transformer.
• Increase and decrease the load resistance. By increasing the load resistance the flyback converter goes from discontinuous to continuous current mode operation. This is because the load is not extracting all of the stored energy from the transformer.
• Change the duty cycle and/or the switching frequency of the converter and examine the impact on the operation of the converter.
• Move the red time line to see how the current flows in the flyback converter during different operating times.