I'm having a problem with the attached Royer circuit, 125VDC input, unregulated 24VAC output.
The output then goes to a rectifier and 15V regulator. Normal current draw is 0.06A from 125VDC input.
[ Specified attachment is not available ]
It seems that when powered up from a slow ramping source there is no problem (e.g. powering up a 125VDC power supply from the mains), but when using a fast ramping source this circuit ocasionally blows the 0.5A fuse (e.g. switching 125VDC to the input).
I had a hunch that the oscillator wasn't starting up properly, so I've tested this circuit thousands of times and only once managed to capture this:
pink trace shows 125V input,
blue trace is the current input,
Yellow and green are Q1, Q2 collector voltages.
![Royer oscillator not starting up? 1505680-1](https://www.eevblog.com/forum/index.php?action=dlattach;topic=328174.0;attach=1505683;image)
It looks like there is a delay in the oscillation starting, resulting in a current spike, then the oscillation starts but by that time the fuse is on its way out and the fuse blows after 37ms.
Would you agree that it looks like the oscillator is not starting immediately and that is causing the higher input current?
Has anyone seen this type of problem with Royer oscillators before and how would you suggest I fix the issue?
For reference, this is what normally happens, the oscillations start immediately and the input current drops quickly to the 60mA level:
![Royer oscillator not starting up? 1505698-2](https://www.eevblog.com/forum/index.php?action=dlattach;topic=328174.0;attach=1505701;image)