Royer efficiency tuning

[Akwasi]

I'm using a Royer converter to charge a capacitor (47nF) to 1kV, it is supposed to run only to from time to time when the charge on the capacitor drops below a threshold,
I used the application note AN118 from Linear Tech as a starting point, to switch the converter on and off I'm using a microcontroller instead of the LT control circuit,

without load the circuit consumes 120mA at 5V supply, I wonder whether this is a normal result, or if I did some mistake,
I'm using the components as in the App-Note, only the transformer is a slightly different type from Coiltronics, it's the 2.5W CTX210659 version instead of the 6W CTX210609,
apart from the power rating and the ESR the transforms are similar,
and the 220nF of the oscillator is a standard foil capacitor instead of the recommended Wima MKP type

could it happen that the transformer goes into saturation and cause additional supply current ?

https://obrazki.elektroda.pl/4420943600_1398703895.png

Thanks for any ideas
Andreas

 

[Orson Cart]

There will be some losses in the Tx and the power transistors, 0.12 x 5 = 0.6watt in total, this sounds reasonable, for lower losses you will need a custom designed transformer that runs at lower flux and to ensure the transistors are mostly soft switched (which they are not quite in this circuit - there will always be some turn off loss in BJT's compared to fets in the same application).
Regards, Orson.

Note also that a 10 Meg load on 1kV is 0.1 watt...

 

[Akwasi]

Thanks, that makes now more sense to me