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How possible to do a SMPS amp with 1000mhz (1ghz)?

okok

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technically it's doable, just out of my long curiosity, after all these years, the highest switching FR from smps amp is 1mhz, come on, we can push a bit farther
 

dfuller

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Other than logic gates, there's basically no reason to operate transistors that fast. Most SMPS designs switch well below 1MHz.
 

amirm

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Work has been done on much faster switching frequencies. Best example is a spin off from MIT, Finsix. I use their replacement switching power supply for my HP laptops. They are a quarter of the size of normal switching supplies. The research was around 30 to 300 Mhz switching frequency. Can't find the exact specs for Finsix but I think it runs at 100 MHz. The faster switching rate allows the reservoir electrolytic caps to become much smaller (to the point of being able to do away with them). The trick was maintaining efficiency with the MIT research solves with a two stage regulation.

You can read more about it online: https://www.powerelectronictips.com/high-switching-frequencies-come-to-laptop-chargers/

Here is a picture of the Finsix supplies:



dims
 

egellings

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At such high frequencies, MMLC (monocaps) would likely do. No 'lytics needed.
 

Panelhead

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The highest I have seen for sale is around 700 kHz. Some of the esoteric new (big bucks) power amplifiers may be higher.
But time will show if higher switching speeds yield better products.
 

Blumlein 88

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Last edited:

egellings

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At that frequency, 2 short pieces of wire or PCB runs in close proximity would constitute your transformer!
 

earworm

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Possibly an incredibly dumb question on these finsix dart chargers; but it did inspire me to register as I've been lurking and considering a class D amp purchase for my office to plug in some old speakers. But of course got hung up on whether I had a compatible power supply on hand instead of which amp to buy :) I have a couple of these dart chargers but no longer use them with laptops as my devices have gone USB-C but finsix went out of business before being able to ship enough USB-C cables (and of course the one I have is busted). Could I use these as power supplies for one of these sub-$100 class d amps if a tip fits? I think it can produce up to 20V at 3.25a. I'd be doing nearfield, quiet listening on small bookshelf speakers so don't need a ton of power.
 

Synergy4

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At only 50MHz clock jitter can cause loss of resolution on a sample data system. Clock phase noise is one of the major limitations for 16bit 1GHz ADCs.

Running very high switching frequencies for a Class D amplifier requires more power in the logic & switching, especially if one one wants high resolution. In CMOS logic, the 1/f noise noise of the MOSFET logic gate contributes to clock jitter. Getting lower 1/f noise in the logic MOSFET requires larger gate area & more current at high speeds.

https://e2e.ti.com/blogs_/b/analogwire/archive/2015/12/11/rf-sampling-clocking-is-the-key-every-time

Jitter.JPG


This 2MHz switching frequency GaN Class D amplifier project used air core output inductors: "GaN Transistor Based Digital Class-D. Amplifier with Global Feedback" by Denis Hafizovic & Magnus Karlsson (2020) CHALMERS UNIVERSITY OF TECHNOLOGY, Gothenburg, Sweden 2020

"The output filter was a second-order low pass LC-filter with a cutoff-frequency of 400 kHz, as a result of a trade-off between aliasing distortion and loop filter gain. Air core inductors were used in the output filter, which resulted in lower resistive losses in the core and well as in the copper windings."

"The proposed system has a THD of as low as 0.005% and a THD+N of 0.02%. Clock jitter in the design is believed to limit the noise performance of the system, which could be significantly improved with a redesign of the clock network. "
 

earworm

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Thanks for the detailed reply. So I’ve read that a few times now, mind boggled and I think the answer is No. If I’ve gotten the answer wrong please chime in :)
 

egellings

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I do not understand how an air core inductor would have lower copper loss than one of same inductance wound on a magnetic core that would use much less wire. I suppose you could use thicker wire in the air core one to compensate a bit.
 

capslock

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I do not understand how an air core inductor would have lower copper loss than one of same inductance wound on a magnetic core that would use much less wire. I suppose you could use thicker wire in the air core one to compensate a bit.

The phrase used was "lower resistive losses in the core" -- well there are NO resisitive losses in an air core. Suppose you can allow some copper resistive loss in that case.
 
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