Hello
i am busy with a TDA8954 PCB.
the TDA8954 looks like a fairly easy IC for a high power amplifier.
PCB design should work out, PCB will be professionally made in china (so cheap
)
but one thing bothers me, the output filter, especially the inductors.
i can imagine these should be able to withstand some serious currents.
i want to make a stereo amplifier for 4 ohm speakers, so roughly 200 watts per channel.
but a classmate wants to make a BTL version of it (8 ohm 400 watts)
what coils are good for this kind of currents?
when looking trough the coilcraft site i found two types look promising:
Coilcraft PCV-1 Vertical Mount Power Chokes
Coilcraft VER2923 High Current Power Inductors
would one of those types be good enough to handle high currents and have decent audio performance?
datasheet TDA8954:
http://www.nxp.com/documents/data_sheet/TDA8954.pdf
Rik
i am busy with a TDA8954 PCB.
the TDA8954 looks like a fairly easy IC for a high power amplifier.
PCB design should work out, PCB will be professionally made in china (so cheap
)but one thing bothers me, the output filter, especially the inductors.
i can imagine these should be able to withstand some serious currents.
i want to make a stereo amplifier for 4 ohm speakers, so roughly 200 watts per channel.
but a classmate wants to make a BTL version of it (8 ohm 400 watts)
what coils are good for this kind of currents?
when looking trough the coilcraft site i found two types look promising:
Coilcraft PCV-1 Vertical Mount Power Chokes
Coilcraft VER2923 High Current Power Inductors
would one of those types be good enough to handle high currents and have decent audio performance?
datasheet TDA8954:
http://www.nxp.com/documents/data_sheet/TDA8954.pdf
Rik
t106-2 is fine, but it's only a core. Regarding to inductors the key is low AC idle loss. Sadly this is almost never specified (correctly). This requirement is generally contradictional to low DC resistance, so any inductor specified for very low DC resistance is likely to heat very much in a ClassD amp. DCR of 15 to 100 mohm is fine for 4 ohm load. But obviously this value doesn't guarantee anything, only a sign.
Generally a low AC loss comes together with high saturation current (air gap), but this also has to be checked.
Generally a low AC loss comes together with high saturation current (air gap), but this also has to be checked.
The core material makes a huge difference.
Iron cores at hf will get very hot.
My class d amp output filter inductors run very cool.
Hello
i am busy with a TDA8954 PCB.
the TDA8954 looks like a fairly easy IC for a high power amplifier.
PCB design should work out, PCB will be professionally made in china (so cheap
but one thing bothers me, the output filter, especially the inductors.
i can imagine these should be able to withstand some serious currents.
i want to make a stereo amplifier for 4 ohm speakers, so roughly 200 watts per channel.
but a classmate wants to make a BTL version of it (8 ohm 400 watts)
what coils are good for this kind of currents?
when looking trough the coilcraft site i found two types look promising:
Coilcraft PCV-1 Vertical Mount Power Chokes
Coilcraft VER2923 High Current Power Inductors
would one of those types be good enough to handle high currents and have decent audio performance?
datasheet TDA8954:
http://www.nxp.com/documents/data_sheet/TDA8954.pdf
Rik
first excuse me because of my english , its bad.
about current of filter :
if power supply is +-40 volts, for 200w+200w ,output current of Ic is 2.5 A+2.5A
for both BTL mode (400w )current is 5A because tow filters are series with 8 ohm speaker .
so the filter at least should be 2.5 A for normal and 5A in BTL mode.
For TDA8954 current protection kicks in at 12A. The inductors shouldn't saturate at least up to that current. Buy 7G17A from SAGAMI with 22uH inductance and live happily ever after. They don't saturate up to 13A.
Yes powder but I was comparing to EI core inductors.
I mistakenly bought power supply inductors for my first class d amp and they got to 120 degrees C with no audio out.
YOZHik is right, saturation current must exceed current limit of IC.
Nigel! What you wrote is contradictional to your own statement. You didn't compare EI in any sentence. You made a general statement about iron cores, although your own example already falsified it.
[...]
Yes, core material makes difference. Even my sister knows this. But how can you judge more or less correctly from the few specified parameters of a manufactured inductor when neither core material nor AC loss are specified? This is what my comment was about. And if you checked, you could see that your fully wound power supply inductor (at the right inductance) had a much lower resistance than the one wound on -2 core, which fact is in agreement with my selection rule of thumb. I could tell the logical background for this correlation, but I dont think it worth the effort.
Nigel! What you wrote is contradictional to your own statement. You didn't compare EI in any sentence. You made a general statement about iron cores, although your own example already falsified it.
[...]
Yes, core material makes difference. Even my sister knows this. But how can you judge more or less correctly from the few specified parameters of a manufactured inductor when neither core material nor AC loss are specified? This is what my comment was about. And if you checked, you could see that your fully wound power supply inductor (at the right inductance) had a much lower resistance than the one wound on -2 core, which fact is in agreement with my selection rule of thumb. I could tell the logical background for this correlation, but I dont think it worth the effort.
Sorry its a good few years since I got involved with class d the first time.
I was wrong to mention EI cores, I think now the power inductors were powder cores. They just got ridiculously hot.
Someone on DIYAUDIO suggested the t106-2 core and they worked great.
I just bought in good quality enamel coated copper wire for the cores and had no problems.
I wound on as many turns as I could on to the t106-2 core and that was about the right inductance.
As you say the resistance of the copper wire is important too.
As doctormord already pointed out t106-2 is an iron powder core also. The difference is in effective relative permeability. -2 material contains more resin between the iron dust particles, which forms a distributed "air" gap, therefore makes average permeability lower. This because you have to use higher number of turns, which leads to lower voltage per turns, which has a result of lower eddy current loss. Isolation between particles is also better, this further reduces eddy current compared to power supply materials like -26, where a high conduction can be measured.
I didn't say this. Actually the opposite tendency of one may think is true. If you compare otherwise similar inductors (same size, same inductance, same saturation current) most often the one with less resistance will heat more at idle. This was the essence of my post. Summarysing it as "resistance is important" is like you said Zootropolis was about cute bunnies and tricky foxes.
I dont know why Im writing here.
sorry ,my english language is bad.
the datasheet say inductance should be 15 or 22 uh.but with -+40 volts supply inductance and IC will be very hot.
i make this amp and understand inductance should be more than 22uh.
i replace inductance with 50uh one.now it works very well and the sound is high quality.