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Rabbedrengen 11th December 2007 11:26 PM

DIY Class D topology Question
 
Id like to build my first class d. Im not a newbie since I have done some projects within switch mode power supply.

But instead of starting from scratch I would like to hear your opinion on what topology I should use for my design, which has a goal of 500W into 8 ohms, I expect to switch around 200 kHz.

Should it be single output or BTL?
Should it be self-oscillating, or driven by a carrier?
If driven by carrier what type, triangular or
sawtooth/ramp?

Component suggestion for the design, Driver, Mosfet, reverse diodes?

Rabbedrengen 13th December 2007 02:02 PM

Anyone? :xeye:

djQUAN 13th December 2007 06:02 PM

I have the same question here.

I'm thinking of either self oscillating or clocked. most probably clocked since self oscillating designs (from what I read around here) tend to have latching problems when driven to clipping which would occur too often in my application.

power goal here is about 800wrms into 1ohm but for subwoofer duty only.

BWRX 15th December 2007 11:05 PM

Re: DIY Class D topology Question
 
Quote:

Originally posted by Rabbedrengen
...500W into 8 ohms, I expect to switch around 200 kHz.

Should it be single output or BTL?
Should it be self-oscillating, or driven by a carrier?
If driven by carrier what type, triangular or sawtooth/ramp?

I would start with a carrier-based single rail bridged output design using one of the popular driver chips. The bridged output will allow you to use a single lower voltage rail as well as lower voltage mosfets. The triangle or sawtooth choice is up to you. Comparing the audio signal to a triangle wave is more common than a sawtooth wave.

Rabbedrengen 16th December 2007 03:28 PM

Hi Brian.

Thanks, I do still have some questions left regarding the components. Should I design the driver circuit or use btw. IR2010?

Is it wise to use Goundplanes or should the high current paths be as normal track, so there is some sort of control of the high current paths?

BWRX 16th December 2007 06:32 PM

If you're comfortable designing the driver circuit then by all means go for it. If you'd like a more off the shelf solution then use a gate driver IC. IR has a few you can pick from if you want to go with them. There's already another thread in this forum by zox2003 who has chosen to use the IR2010.

Contiguous ground planes are the best; this is where the use of surface mount components really help. Remember that high frequency currents follow the path of least impedance. A good solid ground plane provides a lower impedance path than a dedicated trace. Investigate the circuit you want to implement to get a feel for where the currents will be flowing and then design the layout to keep the high current loops small.


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