Hi,
My MPPT converter is also based on the TL494 mentioned before. Principle of the switcher is about the same as you're working with.. A buck converter with a high side FET switch, and freewheeling diodes on the lower side. I'm driving the FET's with a full-bridge driver built from TC4420 and TC4429 (complementary gate drive IC's), and level shifting for the high side fet is done with a small toroidial transformer. Your schematic is missing the level shifting for the FET, I assume you're also going to be forced to use a transformer with it as well.. High & low side gate drivers like IR2110 need also a low side switch to work. I'm attaching a pdf version of the schmatic, it may be helpful if you decide to go with the TL494 route.
It's by no means perfect, but it's been serving me well for over a year now. I've since made some modifications, at least I remember changing the RC feedback dampener of the TL494 to something like 100ohm / 1µF. It could still use some more dampening(on current measurement mayby), or someone with more experience on control loops, to identify the causes of the instability. As it happens, the pulse width output of the TL494 wants to modulate some (+/- ~5%)at a frequency of about 2kHz.
On my diary is more of the practical problems about making it work;
http://board.fieldlines.com/index.php/topic,130334.0.htmlIf I would start from null again, I would do quite a few things differently now..
1; I'd forget about 100kHz, and go with something like 20-30kHz.. Just buy some bigger capacitors and inductor cores, and have easier life making it work reliable.
2; Use synchronous buck topology. It would be more efficient (diodes dissipate quite a lot of heat at big currents..), and it would allow me to ditch the problematic gate drive transformer and just use a floated capacitor driver like IR2110.
3; Forget about the analog control. There's a micro controller in it anyway, so it would be wise to use a right tool for the job, in other words a part with high enought clock speed to be able to generate the PWM waveform on it's own. Much easier to build any interlocks into it that way too.
4; Use something else than a low side shunt current measuring, It's just a pain.. High side shunt monitors, or ready-made hall effect current sensors are not too expensive.
note to moderators; on my diary some of the images are missing, could you investigate? I think they were uploaded to the FL server, what has happened to them??