Hi DIYAudio members,
You probably get these kind of threads a lot, but I'm giving a shot. Not sure if it is a right category for this thread, so let me know if I need to move.
Bit of a background of myself - I've been an electronics engineer for about 4 years now. I have designed various PCB projects ranging from few dozens of components to 400 components from 2 to 8 layer boards. Problem is, that I've got experience only on digital domain and DC-DC power regulators. I want to improve myself on analog and AC circuits and due to my digital background, I'm amazed by the Class-D amplifiers.
Recently I ordered myself a TPA3116 amplifier board with Bluetooth module from Ebay. After analyzing it, it seems pretty straight-forward - a copy of a reference design from the TI datasheet. So I took a goal of designing myself a Class-D amplifier with my own little added funk.
Time to put down some of design constraints.
a) I want one board to power two 4ohm 200W peak, 100W RMS speakers.
b) It must run on a car battery (11.8-14.4V) so DC-DC converter is needed.
c) It must have a input capability of a standard 50W car stereo output.
d) As small as possible.
For b) it is clear for me; DC-DC converter is needed. So far I presume 48V (or more) 14A converter is sufficient to power 400W peaks. This will need a lot of filtering and preferrably a separate PCB, but should be manageable.
For a) I am not so sure. Digging into some integrated Audio Amplifiers from TI, Infineon and ST I found out that THD+N at these kinds of power levels is not pretty. So a Class-D audio driver with integrated PWM converter and separate output MOSFET-s seems a reasonable solution. Here comes my first question - what driver IC-s would you recommend for my application? I've found some from Infineon like IRS2052, but they are meant for single ended applications. I've read that one should aim for full bridge application because of lower harmonic distortion and no "pumping effect", should I aim for that too?
For c) I am also quite clueless. If car stereo amplifier outputs are single ended, then the solution is quite simple. However if a car stereo uses full bridge configuration, then tying one end of the output line to ground will cause short circuit. So using differential amplifier on the input side of my project, which converts differential signal to single ended, would be needed, right?
d) is basically my everyday job. Since heat is probably going to be a problem, I plan to use aluminum extruded profiles for my casing and mount the MOSFETs on the wall of the enclosure to spread the heat.
What are your opinions?
Best regards,
Kristjan
You probably get these kind of threads a lot, but I'm giving a shot. Not sure if it is a right category for this thread, so let me know if I need to move.
Bit of a background of myself - I've been an electronics engineer for about 4 years now. I have designed various PCB projects ranging from few dozens of components to 400 components from 2 to 8 layer boards. Problem is, that I've got experience only on digital domain and DC-DC power regulators. I want to improve myself on analog and AC circuits and due to my digital background, I'm amazed by the Class-D amplifiers.
Recently I ordered myself a TPA3116 amplifier board with Bluetooth module from Ebay. After analyzing it, it seems pretty straight-forward - a copy of a reference design from the TI datasheet. So I took a goal of designing myself a Class-D amplifier with my own little added funk.
Time to put down some of design constraints.
a) I want one board to power two 4ohm 200W peak, 100W RMS speakers.
b) It must run on a car battery (11.8-14.4V) so DC-DC converter is needed.
c) It must have a input capability of a standard 50W car stereo output.
d) As small as possible.
For b) it is clear for me; DC-DC converter is needed. So far I presume 48V (or more) 14A converter is sufficient to power 400W peaks. This will need a lot of filtering and preferrably a separate PCB, but should be manageable.
For a) I am not so sure. Digging into some integrated Audio Amplifiers from TI, Infineon and ST I found out that THD+N at these kinds of power levels is not pretty. So a Class-D audio driver with integrated PWM converter and separate output MOSFET-s seems a reasonable solution. Here comes my first question - what driver IC-s would you recommend for my application? I've found some from Infineon like IRS2052, but they are meant for single ended applications. I've read that one should aim for full bridge application because of lower harmonic distortion and no "pumping effect", should I aim for that too?
For c) I am also quite clueless. If car stereo amplifier outputs are single ended, then the solution is quite simple. However if a car stereo uses full bridge configuration, then tying one end of the output line to ground will cause short circuit. So using differential amplifier on the input side of my project, which converts differential signal to single ended, would be needed, right?
d) is basically my everyday job. Since heat is probably going to be a problem, I plan to use aluminum extruded profiles for my casing and mount the MOSFETs on the wall of the enclosure to spread the heat.
What are your opinions?
Best regards,
Kristjan
Seems to me that the tpa3255 or tpa3251 will fit your needs! Max 50V with the tpa3255 and 32V? with tpa3251. Both has differential input so less alternator whine. Low THD+N and very close to your power requirements. It's not the cheapest chip but its sounds very good! The TPA3251 produces less heat but with lower max voltage. It takes a lot of class D knowledge to make these chips sound flawless so why not buy a cheap chinese board and focus on making a custom car dc-dc converter board that would work with it? The cheapest chinese boards require some fixes btw.. I think a car amp with the tpa3251 would be really nice! I've gone through many class D amps and the tpa3255 amp from 3e-audio on ebay is in a league of its own at the moment with no flaws. so I would get some layout tips from that board if you were to make a new pcb for the tpa32XX chip. There is probably cheaper class D solutions at the moment but this approach would save you a lot of time, and the chips have a lot of safety features that is needed in car setup. Many car amps have a lot of components which fail after 5-10 years, but the tpa chips require so few components that I think it could last in a car enviroment for a very long time.
I am going to use 2x tpa3116 wiener boards in my car eventually, but getting araound the alternator whine problem proves to be a challenge with several boosters and several amp cards. So for now I use 1 booster and a small tpa3116 for micro sub duty which works great! But having a 2/4 channel amp with the tpa3251/55 would be epic!
I am going to use 2x tpa3116 wiener boards in my car eventually, but getting araound the alternator whine problem proves to be a challenge with several boosters and several amp cards. So for now I use 1 booster and a small tpa3116 for micro sub duty which works great! But having a 2/4 channel amp with the tpa3251/55 would be epic!
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