| Electronics > Projects, Designs, and Technical Stuff |
| Terrible Idea Boost Converter To Be Tested On Gocart |
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| james_s:
--- Quote from: amyk on January 02, 2020, 09:38:08 pm ---For a relatively cheap and quick solution I would suggest getting an inverter (one with 120VAC output will be ~170VDC) and either putting a rectifier on the output or tapping into its internal HVDC bus. --- End quote --- You can buy just the 12V->170VDC part from China, at least I've seen them available in the past. Personally I'd be looking at an array of RC LiPo packs to get >100V or a surplus EV battery module. Salvaged Tesla batteries are surprisingly affordable for what you get. |
| T3sl4co1l:
Consider what happens if there is a small say 1% duty mismatch between channels driven at the same PWM; consider further if they have negligible resistance (in the inductor, switch and diode) (which they do); and consider if there's say a 10% error in inductance. What does this do to current flow in the different channels? How can you predict this effect? How can you prevent transistors from exploding? Well, you can't, which is why we put current sensors on them to be sure. ;D Tim |
| pepelevamp:
get one of those spinning wheels that one motor turns while a second one gets spun & generates a voltage. why bother with fast switching mosfets and silicon when you can add an extra wheel to your go-kart and use cogs to convert your power. :box: :) ;D :D |
| i_am_fubar:
Hmmmm, good point. There is definitely a risk here. I would argue that I can prevent the transistors from exploding. But it would be at a significant performance limit. Assuming that all inductors are actually at their -20% limit, I can configure my maximum on time to ensure their current can't rise above a safe value (say 50A). Yes, this means that if the inductor is actually at +20% tolerance, then I'm running nowhere near peak power throughput for the power components, but at the same time, it does mean nothing will go bang (in normal operation). The mismatch is a bigger worry and I may end up with 1 of the 4 phases doing 50% of the conversion, but again, providing my timing is such that I'm not exceeding SOA for each device, I don't see it as a magic smoke risk. Of cause, this is all my opinion as an engineer very new to high power, high speed switching.... So, please keep punching holes :) Plus, if I up my input voltage to 24v at half the current, then the performance degradation of playing it safe should be offset. Way to do efficient, low cost, design :) (sarcasm) On the bright side, I think I finally grasped the physics of gate ringing last night and how the parasitics come in to play, why snubbers work, and why slowing the gate reduces the effect. So, as a learning exercise, this is working :) |
| i_am_fubar:
Also, I have a bus bar design that I'm going to use for feeding the battery supply into each channel. I could integrate a current sensor into each branch of that to get independent monitoring. Onward an upward, more bits coming in today. |
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