Steve Ward's DRSSTC-1 W/OCD First Light Testing
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- Опубліковано 14 жов 2024
- www.stevehv.4h...
The SMD UD board is expensive to build and while much smaller making something like this is way cheaper and can drive 'moderate' power into some coils. I really like the OCD feature though it may not have been wise to use a cheap pot like I did as opposed to a multi-turn trimmer. Very small precise increments can make a big difference in setting it with a cheap pot.
This circuit lacks an important phase lead tuning ability but it should be easy to add with a tunable inductor or maybe fixed inductor with tunable impedance, something I'll probably add before doing real tuning on a coil for this. It seems to handle ~400khz fine so I might get a huge topload and play around with a tappable pancake.
The gate drive is not looking too pretty during this testing so I won't try it from full mains until working that out. Given how the field from this coil does things to far away electronics I've never had a coil do before (like cut on a flashlight with an electronic switch) it's amazing interference wasn't more of an issue during testing.
This test ran with a half bridge of FGA60n65SMD's,15v gate drive w/ 33nf tank cap and 12uF decoupling on 2x 250v 1000uF doubler caps. 2nF in place of C14 for approx running frequency. 20ohm burden resistor on OCD CT using 1:1000 transformers for both OCD and feedback CT's. 18v zeners and 400v TVS diodes.
Nice man ! this video was a big help to me , the details were good. Keep the good work
wow, the pcbs are so clean ;) Nice Mate, love it! keep going!
Thanks bro this one is going to be my mission for a while
Hi ! I am building the same model and I have a question regarding the OCD. When you rotate the variable resistor of the OCD, what exactly happens ? I mean, does it serve to turn the OCD on and off or to regulate how much I want it to protect the circuit? I suppose that when you rotate the variable resistor you regulate the level of protection of the coil, since the load resistance is selected according to the maximum current supported by the IGBTs; hence the relationship of the CTs in cascade and other calculations... I don't know if I have explained myself correctly. Thank you very much!
Yea you're basically setting a voltage set point relative to the burden resistors on the CT via the comparator. In the schematic I believe he has 5 ohms burden resistor. So based upon the amount of voltage this reaches given a CT winding ratio, a particular peak amperage can be determined. So the higher or lower you set this point the more or less peak amperage can flow through the primary before the OCD starts limiting the on time of the driver. The comparator output controls a 555 timer that switches the interrupter signal low through a mosfet whenever this set point (pk current) is reached.
Typically the reason for this is because people are trying to push their setups to a point where they may be close to the limits of what their components can handle, so while they want to get close to a maximum from them they are calculating a pk amperage that is just going to be too much for the circuit. As unpredictable as these can be it's good to be able to set a pk amperage it cannot exceed to protect the mosfets/IGBT's. With mine I'm pushing fairly low power and assuming my tuning/coupling is close enough to not allow excessive primary currents. AKA the primary current is able to transfer to secondary arcs fast enough. So basically I just set mine to trip from ground strikes at the highest input I want to run them after feeling out the tuning. If I ever wanted to push what I thought was close to maximum capability from a driver/switches then I'd probably want to start calculating what these pk amps are going to be and how to set that limit.
It's not something I've quite felt out entirely yet and so far have not really needed the OCD it seems, but it's a tricky thing sometimes to where it has to be shielded properly etc because it can sometimes trigger falsely.
@@Magneticitist Thank you very much for your quick response. Thanks to your explanation I have a better understanding of the OCD concept. I have built Steve's version of the DRSSTC .5 and in that case I didn't need the OCD because I was using a small size coil.
Now, I have built a larger size coil and in this case I do want to protect my IGBTs. Thank you very much for all your work, you are helping a lot of people who want to build their own DRSSTC
@@alexcaleal9025 No problem at all. I've been slacking on building more recently but I should be getting my free time worked out a little better before long. I plan on building a high power one eventually but I've sort of been trying to pilfer what I can from work to save money.
That Drsstc .5 was a great circuit too IMO. I actually had some interesting results with the secondary feedback but my circuit was dying from ground strikes which is why I moved to the one with OCD.
what type of IGBT u use in this setup?
Halfbridge?
Pretty sure these are FGA60N65SMD's but yea this one is a half bridge.
Cool! Have you tried the UD2.7c? It's from Steve Ward too
Never tried to build it due to how much it would seem to cost but if I could get my hands on a preassembled board for cheap enough I'd probably try it just to be able to reliably drive bigger bridges one day.
I've tried to source components to build a version of the driver that is far from 2.7 but has at least a more powerful gate drive and maybe things like UVLO and phase adjust but I'm not sure how I'd do pulse skipping and stuff like that.
@@Magneticitist Im quite new to this, but I've already ordered the PCB and the components to build it. But yeah, it costs around 60$ to 70$
@@natgazer That's really not too expensive in reality but I've gotten used to about $10 or so in cost for the older boards I've been making. For me the real need would come in if I wanted to drive bricks I think. I'm considering that in the future but as of now I honestly haven't even played enough with my 247 package bridges.
@@Magneticitist hmm, ok I see. Good luck