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Old 28th February 2015, 10:47 PM   #1
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Location: Germany near Munich
Cool My new single supply fullbridge amp

Let me introduce you to my new amplifier based on a delta sigma converter and a full bridge stage switching at 500kHz.

The key features are:

- very low power consumption (about 1W in idle).
- closed loop design (at least two feedback pathes)
- not a ucd design to get no problem with the patent
- single supply for saving costs

So I started to simulate a few circuits and got the ******* thing working.

That's what the simulation says:


Click the image to open in full size.

Then I tested the delta sigma converter in a first prototype:

Click the image to open in full size.

After the successfull test I started to design and build a first prototype of the hole amp:

Click the image to open in full size.

Click the image to open in full size.

And finally, that's what the oscilloscope says:

Click the image to open in full size.

Click the image to open in full size.

... stay tuned

Last edited by mantabernd; 2nd March 2015 at 05:30 AM.
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Old 3rd March 2015, 11:17 AM   #2
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Specifications plz?
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Old 3rd March 2015, 12:36 PM   #3
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Good Work!

The PCBs are single-sided?

Very nice lab btw, the UPD is marvelous
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Old 3rd March 2015, 01:23 PM   #4
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Quote:
Originally Posted by sweetperfume View Post
Specifications plz?
Not sure yet, I need to do some more tests. I expect arount 200W/8Ohm in this configuration, maybe more. But it should be no problem to use more fets or better fets for more power. These are rated at 100Vds so a maximum of 60V supply voltage should not be used to stay in SOA.

The first tests were at 30V with a sinewave output at 55Vpp without clipping. Due to the full Bridge design you don't have to use a split power supply.

I can give you some more information in a few days.


Quote:
Originally Posted by BlacK_Chicken View Post
Good Work!

The PCBs are single-sided?

Very nice lab btw, the UPD is marvelous

No, two sided. I use the bottom site for GND. There are no traces at bottom, just solid copper for massive GND.

Thanks, but it's a UPL ;-)
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Old 3rd March 2015, 01:52 PM   #5
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Okay with no specification for now but can share the design working and ups n down with it?
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Old 8th March 2015, 08:26 PM   #6
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So, I continued with my amp. The focus was the first feedback path over the delta sigma converter and the full bridge.

Unfortunately this wasn't that easy then I expected so I had to change a lot inside the delta sigma converter. Now the converter runs at 380kHz with just the first stage. I will try to redesign the second order stage the next days and I will try to come back to 500kHz.

On this screenshot you can see the bitstream, the output and a fft from the delta sigma converter. You can see how the converter works and how the noise is shaped to higher frequencies.

Click the image to open in full size.

But now the good news I get very good THD values, actually 0,037% at 1W so basically the amp runs. FFT plot also looks not bad but the noise could be a bit better.

The next steps are the second delta sigma stage, a feedback path in the analog part (over the output filter) and a better noise floor.

But, for the first shot, this is a very good basis.

Click the image to open in full size.

Click the image to open in full size.


Click the image to open in full size.

Last edited by mantabernd; 8th March 2015 at 08:28 PM.
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Old 9th March 2015, 03:05 PM   #7
stoc005 is offline stoc005  United States
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"The next steps are the second delta sigma stage, a feedback path in the analog part (over the output filter) and a better noise floor."

Any feedback before or after the output filter(s)?? Over the output filter? What does that mean?
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Old 9th March 2015, 04:55 PM   #8
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Post-filter-feedback.
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Old Yesterday, 04:51 AM   #9
stewin is offline stewin  Kenya
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cool good work can the amp handle 2ohms in btl mode??
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Old Today, 01:21 AM   #10
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Nice Design...
Regarding to the clock, do you use Crystal Oscillator to provide clock?
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