Here's Dave Lawton's WFC circuit, with some improvements.
I segregated the power supply to the WFC circuit and the 555 timer circuit, so a voltage drawdown or spike in the WFC part of the circuitry won't affect the 555 timer part of the circuit as much.
The inductor/diode pair allows a 'soft-start' voltage climb (it takes about 7.5 ms to get to operating voltage), then when voltage reaches its operating range, the diode kicks in to keep the inductor 'spinning' without spiking downstream voltage. Because the inductor is always 'spinning' (ie: the downstream circuit is drawing current), a short-term voltage drawdown upstream won't affect voltage supply to the downstream 555 timer circuitry as much, either. The 100 uF capacitor downstream of the inductor/diode pair further acts to smooth voltage fluctuations.
The back-spikes when the MOSFET opens are redirected back to upstream of the bifilar (modeled as a transformer with the WFC connected serially across the primary and secondary). You'll notice that as WFC voltage builds up, the current flow through the large capacitor is more than the total circuit consumes. Once voltage gets high enough, this part no longer contributes to WFC voltage build-up, but it helps to build that WFC voltage more quickly.
I also replaced the resistor on the second 555 timer's output terminal with a diode... you don't want the MOSFET to go into linear mode, you want it to alternate between 'saturation' and 'off'. This gives the biggest voltage spikes. The diode also protects the 555 timer's output terminal from any voltage backspikes should that MOSFET short the drain to the gate.
As for the bifilar itself, I'm experimenting... I've currently got a 1:5 primary:secondary winding ratio, which allows for very high voltage spikes when the MOSFET opens, after WFC voltage has built up sufficiently. This also helps to keep that diode redirecting back-spikes working longer to build WFC voltage, thereby reducing total circuit current draw.
The WFC is modeled as a large capacitor with a spark gap across it, as that's the closest I can come to how an actual WFC would work.
The code:
Code: [Select]
I segregated the power supply to the WFC circuit and the 555 timer circuit, so a voltage drawdown or spike in the WFC part of the circuitry won't affect the 555 timer part of the circuit as much.
The inductor/diode pair allows a 'soft-start' voltage climb (it takes about 7.5 ms to get to operating voltage), then when voltage reaches its operating range, the diode kicks in to keep the inductor 'spinning' without spiking downstream voltage. Because the inductor is always 'spinning' (ie: the downstream circuit is drawing current), a short-term voltage drawdown upstream won't affect voltage supply to the downstream 555 timer circuitry as much, either. The 100 uF capacitor downstream of the inductor/diode pair further acts to smooth voltage fluctuations.
The back-spikes when the MOSFET opens are redirected back to upstream of the bifilar (modeled as a transformer with the WFC connected serially across the primary and secondary). You'll notice that as WFC voltage builds up, the current flow through the large capacitor is more than the total circuit consumes. Once voltage gets high enough, this part no longer contributes to WFC voltage build-up, but it helps to build that WFC voltage more quickly.
I also replaced the resistor on the second 555 timer's output terminal with a diode... you don't want the MOSFET to go into linear mode, you want it to alternate between 'saturation' and 'off'. This gives the biggest voltage spikes. The diode also protects the 555 timer's output terminal from any voltage backspikes should that MOSFET short the drain to the gate.
As for the bifilar itself, I'm experimenting... I've currently got a 1:5 primary:secondary winding ratio, which allows for very high voltage spikes when the MOSFET opens, after WFC voltage has built up sufficiently. This also helps to keep that diode redirecting back-spikes working longer to build WFC voltage, thereby reducing total circuit current draw.
The WFC is modeled as a large capacitor with a spark gap across it, as that's the closest I can come to how an actual WFC would work.
The code:
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