LF: High Power Mono Reference Design

[J.R.Freeman]

Good afternoon all,

I am looking for a proven design, if only for the sake of interest, for a high-powered class D subwoofer amplifier. The general requirements would be:

- In the range of 750 to 1000 watts peak output power
- Stable with a 2 ohm load impedance ideally (4 ohms or less would be nice)
- For frequency response, a -3 dB lower knee of 10 to 15 Hz

For the purpose of this discussion, I will omit power supply requirements. Do any of you know of such a proven design? If not, would there be interest in a collaborative design of sorts? I am new to class D, and as such have no experience to offer. However, I have a background in electronics, and might be able to propose enough silly ideas to keep things interesting!

Jim

[J.R.Freeman]

Good evening,

It would seem such a design is rare. Would there be value in working together, on an open-source design for such an application? Just for fun, here are some (newbie!) thoughts.

The design goals:
- low frequency extension (down to 15 Hz @ -3 dB would be nice)
- able to drive low impedance loads (4 ohms or less)
- high power output (750 W peak or greater into 4 ohms within usable BW)
- modest parts count if possible
- reasonable cost
- reliable

Compromises:
- THD (within reason, distortion content is not as important)
- physical size (groups of output devices, for example)
- efficiency if need be (current sharing resistors added if needed, for example)

***

Just to get the ball rolling, here is a rough draft of the building blocks.

IRS2092 looks like a nice front end chip. My first thought is to mate it with a gate driver IC, namely IRS2011. IRS2092 appears (from the reference design) to be intended for half-bridge use. This brings us to the first of my newbie questions: could I use it in a full-bridge design, using multiple gate drivers? Also, if I wanted to use additional output devices, can I simply add gate drivers? I would imagine PCB trace length may become an issue in order to maintain synchronous switching, but that is getting ahead of things.

More to come, it's late for now! :P

Jim

[fredos]

Where are you located? Montreal?

[authlxl]

Originally Posted by J.R.Freeman

Good evening,

It would seem such a design is rare. Would there be value in working together, on an open-source design for such an application? Just for fun, here are some (newbie!) thoughts.

The design goals:
- low frequency extension (down to 15 Hz @ -3 dB would be nice)
- able to drive low impedance loads (4 ohms or less)
- high power output (750 W peak or greater into 4 ohms within usable BW)
- modest parts count if possible
- reasonable cost
- reliable

Compromises:
- THD (within reason, distortion content is not as important)
- physical size (groups of output devices, for example)
- efficiency if need be (current sharing resistors added if needed, for example)

***

Just to get the ball rolling, here is a rough draft of the building blocks.

IRS2092 looks like a nice front end chip. My first thought is to mate it with a gate driver IC, namely IRS2011. IRS2092 appears (from the reference design) to be intended for half-bridge use. This brings us to the first of my newbie questions: could I use it in a full-bridge design, using multiple gate drivers? Also, if I wanted to use additional output devices, can I simply add gate drivers? I would imagine PCB trace length may become an issue in order to maintain synchronous switching, but that is getting ahead of things.

More to come, it's late for now! :P

Jim

Excellent works!I think self osc topic is not good choose,we have developed one module use discrete parts like JBL EON518S or EON515 active modules,(JBL :: Product)
but we not use it at 10Hz low frequency,we cut off 40Hz low frequency due to woofer can't works and out of hearing.fixed frequency class D should good choose and usually use full bridge and low voltage added when 2ohm load,

If you like you can connect us ,our mail:authlxl@gmail.com

[81bas]

Try to look here first: ucd 25 watts to 1200 watts using 2 mosfets

[J.R.Freeman]

Originally Posted by fredos

Where are you located? Montreal?

In the land of the square-heads: eastern Ontario here

[J.R.Freeman]

Originally Posted by authlxl

Excellent works!I think self osc topic is not good choose,we have developed one module use discrete parts like JBL EON518S or EON515 active modules,(JBL :: Product)
but we not use it at 10Hz low frequency,we cut off 40Hz low frequency due to woofer can't works and out of hearing.fixed frequency class D should good choose and usually use full bridge and low voltage added when 2ohm load,

If you like you can connect us ,our mail:authlxl@gmail.com

Thank you for your comments. A commercial product may be the best solution here, but for interest's sake I would like to consider an alternate DIY design. Thank you for the email, however - I will keep that on hand!

Jim

[J.R.Freeman]

Originally Posted by 81bas

Try to look here first: ucd 25 watts to 1200 watts using 2 mosfets

Good afternoon,

Thank you for your comments. Hmm, that's interesting: so that circuit has a descrete PWM front end and a high-voltage gate-driver IC? An interesting design, but for heavy-duty, long-term use I wonder how such a few number of output devices would fare.

[J.R.Freeman]

Hey again all,

Here is a quick drawing I made to go along with some questions, concerning the IRS2092 IC. Could you do something like the following to use the IRS2092 in a full-bridge design? If VB and VCC were supplied with low (TTL) level voltages, could HO and LO be used to drive dedicated gate driver IC's in this way? My goal here is to drive multiple pairs of output fets, with each pair having its own driver. My guess is that the bootstrap circuitry will not be manipulated like this. Any thoughts? (be gentle, I'm new!)

edit: this drawing is intentionally simplified for the purposes of this discussion!

Jim

[J.R.Freeman]

Hey again all,

I may have killed the conversation by considering too many things at once. Here is a question then, that perhaps someone with experience might be able to help me with:

Assuming I'd like to go with a full-bridge design, is the IRS2092 a good choice as the front-end?

While considering this question, I have been thinking a bit about the basic circuit structure of such a design. One method of implementing a full-bridge makes use of 2 IRS2092 IC's, driven with a differential signal, generated by inverting the incoming audio signal to 1 of the IC's, with each IC running in half-bridge mode. Is this the preferred method? Would it be possible to use a single IRS2092, and a gate-drive-buffer section to drive all 4 fet groups?

Any and all comments are appreciated. This past weekend I managed to get a free schematic layout / PCB package up and running at home, so I will start to post some schematics as things progress.

Jim