| Electronics > Beginners |
| Bypassing Loads Under Constant Current Efficiently |
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| TheDood:
--- Quote from: T3sl4co1l on December 08, 2019, 10:04:10 am ---Well, the most important part is, the sources are alternately pulling above and below what you've declared as GND. The AC lines are only alternately connected to ground via the diode bridge. Half the time they're high up, supplying whatever Vout is, give or take. If you're supplying a 30V load, goodbye Vgs(max). Or say a line transient comes along, or someone just turns it on during a line peak. Tim --- End quote --- Man I'm sorry, I'm not trying to be dumb here, but Im still missing it. Is the simulation wrong? I just added more diodes to create a load Vf of ~62V. I still only get 7.8V max delta between NMOSsg (though a bit more -V at source pin, maybe -4.4V max)? I'm not comprehending how the load V will effect Vgs? I'm designing around single phase AC. As far as the surge from a mains spike, can't I use a TVS? And I figured the load cap would help during a turn on while mains was at peak V. But maybe Ill have to devise a way to create a small delay between mains input and load energizing, like a resistive short but only for a second till X1 cap is impeding like intended? Also, I was going to implement a type of GFCI or a re-setable trip to mitigate the need for a replaceble fuse. EDIT: If I put the coil before the load, would that help current surges more than if placed after the load? |
| T3sl4co1l:
Oh right, body diode holds source down, and the series diode disconnects the high side. Nevermind! You still have a number of fundamental problems, with the C dropper, and dimming, which are why this method isn't used for more than a very small amount of power (a few watts?). Tim |
| TheDood:
You guys have been very helpful in my comprehension thus far, thanks. Feel free to point out any issues with capacitive droppers that I might not know about. I've seen lots of negative comments about them, how they are unsafe, inefficient ect, but it seems to me you can add safety regardless the type of power supply, and I'm missing where they're inefficient. The biggest thing I'm guessing is the PF, but residents in the states dont pay for PF. Even still, I'll probably look into what it will take to correct it because it will probably gnaw at me after awhile lol |
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