SHAKE TO START!
The yellow waveform is the triggering pulses,
Green waveform is the load current and blue is the SCR current.
A Morgan Chopper is a DC-DC converter that uses an SCR as a switch. The SCR is triggered using a relaxation oscillator and a pulsing transformer. The SCR is commutated (turned off) using Class B commutation http://everycircuit.com/circuit/5601123789176832 .
Since the on time is a constant, the power delivered to the load is controlled by varying the off time. This method is called Pulse Frequency Modulation.
