questions about royer oscillator

[lokeycmos]

so i built the attached circuit and i have a couple questions about it.

1. what determines the oscilating frequency? is it the capacitor or is it based off the feedback winding?

2. not all flybacks are the same. if i were to calcualte the resonant capacitor based off the oscilating frequency and the inductance of the 7+7 turns, would i measure inductance from all 14 turns or just 7 turns?

3.im a little bit confused, if the frequency changes with capacitance, then the only constant i have is the inductance of the primary.

4. what would the optimum frequency be then? then i can calculate the proper capacitor

 

[Bob Scott]

This schematic looks almost identical to the power supply in a '70s era CD electronic ignition or electronic flash for photography.

Determination of the oscillating frequency is not easily calculable. The frequency of operation is dependent on the saturation of the magnetic core. One transistor turns on. Its base gets positive feedback from the second winding, shown drawn on the primary side. Current rises with time until it becomes so great that the core saturates, this second winding loses voltage, the transistor turns off, and inductive flyback turns on the other transistor. Repeat ad infinitum.

Determination of the operating frequency is best done by experimentation..... unless someone else has a better idea?

 

[dr pepper]

The resonant frequency will be adjustable a little with the capacitor, you wouldnt want to mess with the turns as that affects the output voltage as well.
The circuit also works partially as a blocking oscillator so the lopty has a large effect.
80khz has worked for a similar circuit I've built, but it does depend on the lopty.
The circuit might work without the capacitor, some fglyback drivers dont use one, current draw will increase however.