Hello,
Are here any tallented people willing to share a PCB design for Elliotts' Project 175 (Single Supply BTL Amplifier Speaker Protection)?
Project 175
Due to little interest, Elliott won't sell ready PCBs too soon (that's what he answered).
It seems curious there is so little interest in Class D speaker protection (yes , I know, the chips already have lots of built in protections), while the interest in the amplifiers themselves is quite high.
As I know, UPC1237 is not optimised for BTL configuration, and I really don't trust the chinese boards claiming BTL speaker protection capability.
Thanks.
Are here any tallented people willing to share a PCB design for Elliotts' Project 175 (Single Supply BTL Amplifier Speaker Protection)?
Project 175
Due to little interest, Elliott won't sell ready PCBs too soon (that's what he answered).
It seems curious there is so little interest in Class D speaker protection (yes , I know, the chips already have lots of built in protections), while the interest in the amplifiers themselves is quite high.
As I know, UPC1237 is not optimised for BTL configuration, and I really don't trust the chinese boards claiming BTL speaker protection capability.
Thanks.
Isn't the problem with speaker protection that you are never 100% safe, even with very competent designs? You may trust some more than other, of course.
Therefore, my approach is to design my own such that I at least know who made a mistake should it go wrong. I never use standard protection ICs and designing an own circuit is not rocket science.
Sorry, I haven't got a PCB design.
Therefore, my approach is to design my own such that I at least know who made a mistake should it go wrong. I never use standard protection ICs and designing an own circuit is not rocket science.
Sorry, I haven't got a PCB design.
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If DC appears on the speaker terminals of a class D switching amplifier, no amount of speaker protection will save the amp as it will be too late, the output stage will be damaged unless specifically designed for variable DC levels.
The IRS class D drivers check for DC levels and power off the output stage automatically.
The best protection, so far as your speaker is concerned, would be an inline speaker fuse.
The IRS class D drivers check for DC levels and power off the output stage automatically.
The best protection, so far as your speaker is concerned, would be an inline speaker fuse.
And I would not go for any speaker relay.
In case the amp melts and puts out full dc-voltage -
your relay might be arcing, until the voice coil of the speaker is some drop of metal.
A long time ago I checked this with 40DC into 4 Ohms with a 15amp relay -
no way, it was not capable to disrupt the current flow.
In case the amp melts and puts out full dc-voltage -
your relay might be arcing, until the voice coil of the speaker is some drop of metal.
A long time ago I checked this with 40DC into 4 Ohms with a 15amp relay -
no way, it was not capable to disrupt the current flow.
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Might automotive (rated) relays be an option? They "should" be designed to break DC, right?
Most "normal" relays i've seen, despite being rated for 3-10A AC at mains voltages, were only rated to break the same current at (up to) 30V DC.
Most "normal" relays i've seen, despite being rated for 3-10A AC at mains voltages, were only rated to break the same current at (up to) 30V DC.
As I know, DC arching is a thing and it occurs especially over 30V. The lower the voltage, the lower the chances of arching. A method to prevent/reduce arching effects is to connect relays in series (or the multiple contacts of a single relay).
I think this DC protection curcuit concerns mostly the speakers, not the amplifier - i've seen many people here (including me) willing to power expensive speakers with cheap class D boards.
I think this DC protection curcuit concerns mostly the speakers, not the amplifier - i've seen many people here (including me) willing to power expensive speakers with cheap class D boards.
The fuse seems to be one good ideea but it's not that easy to choose the right fuse (easy not at all).
Project 175 looks like a good solution for our purpose.
Project 175 looks like a good solution for our purpose.
A relay that is designed to switch a 30Amp DC load for a vehicle is not rated for an inductive load, ie; a loudspeaker. Use a fuse.
NO relay, no matter how good it is, will work for these scenarios. For any amplifier with rails above 40 or so volts, when a fault indeed occurs, the contacts will weld and the speaker most likely still be destroyed.
Instead, use a Mosfet relay, like here:
Project 198
Use IRF150P220 mosfets, they are rated at almost 300 amps and their Rds is about 2.5 milliohms, which is almost as good as 3 feet of 1 mm2 of copper wire (1.7 milliohms).
Those will never break, never arc and will always respond faster than a relay. The only negative is that you will not hear that familiar "click" when you switch on the amp 🙂
Instead, use a Mosfet relay, like here:
Project 198
Use IRF150P220 mosfets, they are rated at almost 300 amps and their Rds is about 2.5 milliohms, which is almost as good as 3 feet of 1 mm2 of copper wire (1.7 milliohms).
Those will never break, never arc and will always respond faster than a relay. The only negative is that you will not hear that familiar "click" when you switch on the amp 🙂
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