Timeline for Can Class D output capacitors be placed towards both rails?
Current License: CC BY-SA 4.0
10 events
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| Jan 19, 2023 at 10:37 | comment | added | Rohat Kılıç | @tobalt partially. Have a look at this. | |
| Jan 19, 2023 at 8:52 | comment | added | tobalt | Rohat, I am asking (after 2 days) because I cannot reproduce this excess current in my sim (nor hypothetically in my mind), so obviously I have accidently done something wrong (such as failed to include some crucial parasitic effect). I guess what you may mean: When the transistors switch and demand current from the power rail, it usually comes from the input cap. With the split cap arrangement, it will also take some of it from the output caps (but accordingly less from the input cap). Is that what you mean ? | |
| Jan 19, 2023 at 8:35 | comment | added | Rohat Kılıç | @tobalt you have a simulation tool. Simulate it and see it yourself. | |
| Jan 19, 2023 at 8:09 | comment | added | tobalt | Ok, so assume we have a pi filter after the Vpow source. Then through which components will there be a current spike when the half-bridge switches, and how will this current spike be higher/different compared to the situation where C2 is missing? | |
| Jan 19, 2023 at 7:42 | comment | added | Rohat Kılıç | @tobalt I wrote "For the supply you'll probably have a PI filter..." I meant supply filtering, I didn't say anything output filtering. | |
| Jan 19, 2023 at 7:38 | comment | added | tobalt | Sorry for asking again. The load is indeed Vpow-referenced. Why would anyone ever use a pi-filter as output filter after a half-bridge ?? That first C in the pi filter (which I assume, you mean would be on the left side of L1) is just tremendous useless burden on the switching transistors. So no, I don't have a pi-filter, just the L right from the switch node output into the output caps. (Of course there might be very small snubbing components near the switch node itself). So I am still not really sure which current spikes you are talking about.. through which components ? | |
| Jan 17, 2023 at 8:06 | history | edited | Rohat Kılıç | CC BY-SA 4.0 |
added 78 characters in body
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| Jan 17, 2023 at 8:04 | comment | added | Rohat Kılıç | @tobalt For the supply you'll probably have a PI filter in which the L has a non-zero DC resistance (I should've added this detail into my answer, sorry. Now I'm adding it.). Make an LTspice simulation and you'll see. If you won't have any filter then just ignore this. | |
| Jan 16, 2023 at 15:44 | comment | added | tobalt | It is for 48V nominal Vpow, so I'll have to check some of those C(VDC) curves carefully. Could you please explain why there would be switching related peak currents (more than in a only-C1 scenario) ? | |
| Jan 16, 2023 at 15:40 | history | answered | Rohat Kılıç | CC BY-SA 4.0 |