I had tried previously using an Ixys driver, but I I think I may have blown it. It is hard to tell. I ended up pulling it out along with the IRF510 and putting a new IRF510 in with a bjt push-pull driving it, and a 2n7000 in front of that.
After wiring this up, I started with a lower Vcc and immediately got an output of about a watt. Encouraged, I started slowing upping the voltage. But at some point it stopped working - the power supply over current safety was tripping, and I wasn't getting an output, same as before. But this time I went though and wiggled all the components and did continuity tests and tried again. Then it started working again. So maybe this is what was happening before - some stray whisker or something. In any case, I upped the voltage up to 15v and got out about 4 watts. I didn't want to go higher than that because I don't know the voltage ratings on the capacitors I used (the shunt cap should end up with about 3x Vcc if I remember correctly).
So, a bit of a success. However, LTSpice thinks I should be getting out 14 watts at that voltage. Also, the supply says I am drawing 694mA, which would be 10.4W, so not sure where that other 6.4W is going. Nothing was getting that hot (I didn't even have a heat sink on the IRF510). I probably need to go look at the waveforms at all the different points, but don't have time to do that right now.
Nice work Ben. I will look at that discrete bjt totem pole also as that may help my PA to work. Charlie ZL2CTM
ReplyDeleteThose values look about right. 680p D-S and 1n5 on the O/P. I just use a 100n coupling cap and 7T on T94-2 as BPF.
ReplyDeleteDriver wise using the NCP81074A keeps things things simple and SQUARE!
Thanks! I'll take a look at that. MOSFET drivers are an area that I don't know much about.
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