"The Classic-D" - New Class-D Amp from Silicon Chip

[kpimage]

Silicon Chip is an Australia Electronics Magazine has just released their World first DIY high-power high-performance Class-D amplifier called “The Classic-D”.

It’s rated at 250W into 4ohms & 150W into 8ohms.

The magazine publish part 1 3 days ago, but their web site Silicon Chip still shows October issue.

Like with most designs/kits it pays to wait after part 2 the construction issue in case there’s any errata or changes to components due to availability.
I must say it looks like good project to sink your teeth in.

Normally Altronics and Jaycar Electronics are kit reseller and PCB’s and layouts from Silicon Chip downloads & online orders.

[DUG]

4 V DC protection?

A little too much for me.

[kpimage]

Are talking about the dc offset which is monitored by Q7 & Q8, which goes through RC filter to remove the frequencies above 0.3Hz on the amps output, if it occurs it the mosfet short circuits and the IC1 can't shut down, the full supply voltage will be applied to the speaker.

So the backup optional speaker board kicks-in triggering the relay to break the connection between the failed module and speaker the two boards work in conjunction to protect the speaker, this my understanding as quoted the designer.

[DUG]

I think I need a little help here.

Where are Q7 & Q8? ("...dc offset which is monitored by Q7 & Q8...")

The schematic of the "CLASSiC-D Loudspeaker Protector" shows protection from one polarity of catastrophic failure for two channels. This I can see...sort of.

What happens if the output transistor in the negative rail develops a short circuit?

With loud music (output greater than the 4V needed to turn on the opto-isolators) wouldn't the transistor outputs turn on enough to discharge the 4.7uF capacitor through the 1K resistor faster than the 100K resistor could charge it back up?

This could be a great SPL limiter.

[googlyone]

There is a schematic of the dc protection circuit missing from the op. the dc protection is very conventional and should work just fine.

[kpimage]

Found the protection circuit, this should make better sense now.

[alexcp]

The design seems to be close enough to the reference design from IR. There are some additional details and measurements in this PDF: http://www.irf.com/technical-info/re...iraudamp7s.pdf. Same with no SMD components: http://www.irf.com/technical-info/re...iraudamp7d.pdf

I have had that for some time, and it does sound nice. I use it with a Hypex SMPS400A180.

[DUG]

Originally Posted by kpimage

Found the protection circuit, this should make better sense now.

Yes, it does.

Thank you

[kpimage]

[QUOTE=alexcp;3234335]The design seems to be close enough to the reference design from IR. There are some additional details and measurements in this PDF: http://www.irf.com/technical-info/re...iraudamp7s.pdf. Same with no SMD components: http://www.irf.com/technical-info/re...iraudamp7d.pdf


Yes your quite right the article at the end credits it's References to;

(1). IR Application Note AN-1138(IRS-2029S) - http://www.irf.com/technical-info/appnotes/an-1138.pdf
(2). IRS2092 Data - http://www.irf.com/product-info/data...ta/irs2092.pdf and
(4). AN-1071 Class D Amplifier Basics-http://www.irf.com/technical-info/appnotes/an-1071.pdf - Entrée Forbidden

[alexcp]

An interesting part of the reference design is its scalability. The reference design documents discuss in detail how the same schematic and PCB can be used to build a 25W, 60W, 125W or 250W (into 8ohm) amplifier. The principal difference is the rail voltage (from 2x25V to 2x70V), which requires right power FETs and some other minor adjustments. This means that the SiliconChip design can easily scale up or down as well.