Have made a TPA3255 board thinking it would be super easy to get working 🙄
But it will not start up, and I'm a bit stuck .....
There is oscillation on OSC_IOM/IOP, see oscilloscope picture.
Had made some stupid mistakes with the reset circuit, but have replaced it with just a blue LED and the 5.6k to 12V which was already there. This means I get 2.6V on reset which should be ok. When I short the LED, bringing RESET to GND and let go again, there is short action on the output surely trying to start up, but it stops right away.
I have put red numbers on the Schematics, for the measured voltages.
Fault is low, and Clip_OTW is high.
This should mean "Overload (OLP) or undervoltage (UVP). Junction temperature lower than 125°C" .... but where is the Under voltage?
Nothing is hot.
When reset is set to GND Fault goes high.
Any suggestions?
Thanks
But it will not start up, and I'm a bit stuck .....
There is oscillation on OSC_IOM/IOP, see oscilloscope picture.
Had made some stupid mistakes with the reset circuit, but have replaced it with just a blue LED and the 5.6k to 12V which was already there. This means I get 2.6V on reset which should be ok. When I short the LED, bringing RESET to GND and let go again, there is short action on the output surely trying to start up, but it stops right away.
I have put red numbers on the Schematics, for the measured voltages.
Fault is low, and Clip_OTW is high.
This should mean "Overload (OLP) or undervoltage (UVP). Junction temperature lower than 125°C" .... but where is the Under voltage?
Nothing is hot.
When reset is set to GND Fault goes high.
Any suggestions?
Thanks
Attachments
Well, been there, done that. Same experience with my DIY-boards sometimes.
The mistake was always a solder blob causing a short circuit between an output pin to adjacent GND or PVDD pin.
Output pins are surrounded by power supply pins, so there is a good chance for such short.
On startup all output pins are checked for shorts to GND and PVDD.
Take a DVM and check pin-to-pin for shorts.
Desolder until ok.
Then restart.
You may find the TPA is now working - telling you the protection scheme is really effective making these chips robust for DIY
The mistake was always a solder blob causing a short circuit between an output pin to adjacent GND or PVDD pin.
Output pins are surrounded by power supply pins, so there is a good chance for such short.
On startup all output pins are checked for shorts to GND and PVDD.
Take a DVM and check pin-to-pin for shorts.
Desolder until ok.
Then restart.
You may find the TPA is now working - telling you the protection scheme is really effective making these chips robust for DIY
Last edited:
@zhaojunsong
Main power is ok at 24V
@bucks bunny
Could be it, for sure makes sense. Will try that tomorrow.
Thanks, both 🙂
Main power is ok at 24V
@bucks bunny
Could be it, for sure makes sense. Will try that tomorrow.
Thanks, both 🙂
Damn, no such luck.
No shorts on output, not to PVDD or GND.
Even de-soldered the 4 protection diodes on output (to protect over voltage on output if speaker removed during high output due to the filter coils).
Really strange!
No shorts on output, not to PVDD or GND.
Even de-soldered the 4 protection diodes on output (to protect over voltage on output if speaker removed during high output due to the filter coils).
Really strange!
The era of Class-D chips 😗
- Changed the chip already? You should just to be safe. (where did you source those chips) ?
- First time build using a TPA3255 schematic, compared it to eval board? or Self proposed. ?
Sourced and mounted by JLCPCB
Got 2 produced and mounted, so I can try the other board as well. Just strange that all the voltages seems good!
Basic schematic is the same. The core design is only a few caps and a few resistors. Then fed by the right PSU voltages.
Got 2 produced and mounted, so I can try the other board as well. Just strange that all the voltages seems good!
Basic schematic is the same. The core design is only a few caps and a few resistors. Then fed by the right PSU voltages.
Yeah, I would be very cautious on the source of those TPA3255 chips and keep at least two sourced from a reputable electronics supplier in your stock items used to compare/trace each part for variance. I'm not saying they bad but you never know.
I would also trace the capacitive coupling of the PCB traces, parts. Your DVM may give DC affirmative OK! but not AC continuity at Z_imp under load.. bad cap, chip? who knows.
I would also trace the capacitive coupling of the PCB traces, parts. Your DVM may give DC affirmative OK! but not AC continuity at Z_imp under load.. bad cap, chip? who knows.
Do not think JLCPCB are selling fake components!
I would think the problems are more basic than capacitive coupling.
I'm using 4 layer pcb with internal layer for GND, and one for Vcc on half, 12V on the other.
Think I took quite good care of the routing, but sure you never know!
Read somewhere that C_Start pin 15, should be around 2 V! ..... mine is only ca. 1.3V
I would think the problems are more basic than capacitive coupling.
I'm using 4 layer pcb with internal layer for GND, and one for Vcc on half, 12V on the other.
Think I took quite good care of the routing, but sure you never know!
Read somewhere that C_Start pin 15, should be around 2 V! ..... mine is only ca. 1.3V
I think that when I started it the first time, I had no 3V3 Zenner on D6, protecting RESET. Therefor it probably got 12V in!
I think it might have damaged the reset circuit internally in the chip.
Think I will have to build up the second PCB to test it out.
I think it might have damaged the reset circuit internally in the chip.
Think I will have to build up the second PCB to test it out.
VCC vs. 12V rail timing?
Try feeding the 12V from an external always-on rail, and then power up the amp. Or, see the above suggestion.
Try feeding the 12V from an external always-on rail, and then power up the amp. Or, see the above suggestion.
Are the output coils on the same core as symbolized in the diagram? I don't think this approach is correct. Moreover, according to the way it is symbolized in the diagram, the inductances of the two coils on the same core cancel out for the output signal in antiphase and the integrated circuit "sees" approximately zero inductance at the output which implicitly makes it generate a short circuit error at the output.
Also do a test with completely independent coils on the inputs.
Also do a test with completely independent coils on the inputs.
Hi sesebe, Extreme_Boky nd zhaojunsong
Firstly sorry for the very late replay. I have been swamped by work and have had no energy to work on this especially as it seemed I was at a dead end 🙄
But sesebe you are comepletely right, the two coils are mounted wrongly, both on schematics and on pcb. Nicely spotted
Thanks 🙂 .... should just have looked at my HIP4080 design from 20 years ago!!
Dismounted both coils completely, and the amp starts .... damn 🙂 ..... thanks a lot for the help ... I simply didn't see it!!
Mounting the 2 windings on the same coil has at least the benefit of a smaller layout and design. I'm using a T106-2 toroid, which should be more then enough for the 200W here.
Might/should also be some added benefit in reduced EMC.
As for the startup circuit, as said from the start ... just wrong design, so need to be fixed to ensure low pop operation.
Ok, next is to mount the coil correctly (with one winding reversed). Stay tuned 🙂
Firstly sorry for the very late replay. I have been swamped by work and have had no energy to work on this especially as it seemed I was at a dead end 🙄
But sesebe you are comepletely right, the two coils are mounted wrongly, both on schematics and on pcb. Nicely spotted
Thanks 🙂 .... should just have looked at my HIP4080 design from 20 years ago!!Dismounted both coils completely, and the amp starts .... damn 🙂 ..... thanks a lot for the help ... I simply didn't see it!!
Mounting the 2 windings on the same coil has at least the benefit of a smaller layout and design. I'm using a T106-2 toroid, which should be more then enough for the 200W here.
Might/should also be some added benefit in reduced EMC.
As for the startup circuit, as said from the start ... just wrong design, so need to be fixed to ensure low pop operation.
Ok, next is to mount the coil correctly (with one winding reversed). Stay tuned 🙂
Attachments
Too much work so too little time to experiment 😉
But now I can get both channels up and running with sound
I have replaced one of the differential coils with two single coils, for one channel, and kept the differential coil for the other.
But there is problems in getting it started up!
With input connected, but without the speaker connected, on the channel with 2 single 10uH coils, using a super simple delay circuit with 10uF cap, Blue LED (2.6V), and a 5.6k resistor, the start is as follow in the two videos.
It starts briefly, with 50/50 duty cycle, then clip turns on, and it goes to one "rail" almost, with very low duty cycle, and then it slowly returns to 50/50.
Seems it is the caps in the input stage which takes very long to get charged. Tried to slow the RESET by changing the 10uF to 100uF ... but still the same.
My coupling caps are 33uF in the front end.
Should probably just have stayed with the "standard" TPS3802K33DCKR circuit ......
But now I can get both channels up and running with sound
I have replaced one of the differential coils with two single coils, for one channel, and kept the differential coil for the other.
But there is problems in getting it started up!
With input connected, but without the speaker connected, on the channel with 2 single 10uH coils, using a super simple delay circuit with 10uF cap, Blue LED (2.6V), and a 5.6k resistor, the start is as follow in the two videos.
It starts briefly, with 50/50 duty cycle, then clip turns on, and it goes to one "rail" almost, with very low duty cycle, and then it slowly returns to 50/50.
Seems it is the caps in the input stage which takes very long to get charged. Tried to slow the RESET by changing the 10uF to 100uF ... but still the same.
My coupling caps are 33uF in the front end.
Should probably just have stayed with the "standard" TPS3802K33DCKR circuit ......
Attachments
33uF coupling caps are way too big - they take 3x as long to charge up to a steady value for DC offset protection. Change to 10uF and see if that helps.
Next time just use a startup voyage supervisor chip like the reference design and not worry about all the startup issues.
The clip light occasionally coming on and the 50:50 imbalance is probably from inputs not charging up evenly and still settling after the startup logic has been enabled to on.
Next time just use a startup voyage supervisor chip like the reference design and not worry about all the startup issues.
The clip light occasionally coming on and the 50:50 imbalance is probably from inputs not charging up evenly and still settling after the startup logic has been enabled to on.
You might consider using high quality shielded flat copper high current (10A) inductors like CoilCraft SER series. The shielded design reduces stray RF emission from the Class D switching frequency. The distortion will be less because the operational current is well below the upper saturation limit. It makes a difference in sound quality. Here is an example on my amp:
Wurth also makes similar ones. They are not cheap at $6ea but you can get free samples for a few first ones by requesting them.
Wurth also makes similar ones. They are not cheap at $6ea but you can get free samples for a few first ones by requesting them.