Hi all,
I had some troubles with my TPA3255 amplifier design a couple of years ago when I first built it.
I found it to be very unstable despite not using PFFB, I posted about it here on the forums but it's hard to solve online but I ended up finding adding an inductor to the PSU input solved the issue. This wasn't a satisfying fix but having tested with highly capacitive loads and square wave inputs, the design was proven to be stable. The instability was present with whichever PSU I used: a 1200W ACDC 48V PSU, the linear lab PSU or a toroidal transformer without any regulation.
Fast forward to this week and the 48V ACDC PSU I using for the project in its daily use failed despite years of zero trouble from this amplifier. In the meatime, before replacement arrived, I used the 32V lab PSU and noticed the volume with the exact same input level was much lower but the sound quality was perfectly good.
I've been reading trough the TPA3255 datasheet but can't find anything regarding gain dependacny on the power supply voltage. The diagram shows that the internal feedback is taken from the output so the ratiometric voltage effect on H bridges should not apply here.
This symptom seems to be a key insight into my original problem. Does anyone have any insight or pointers?
Attached is the schematic.
Many thanks!
I had some troubles with my TPA3255 amplifier design a couple of years ago when I first built it.
I found it to be very unstable despite not using PFFB, I posted about it here on the forums but it's hard to solve online but I ended up finding adding an inductor to the PSU input solved the issue. This wasn't a satisfying fix but having tested with highly capacitive loads and square wave inputs, the design was proven to be stable. The instability was present with whichever PSU I used: a 1200W ACDC 48V PSU, the linear lab PSU or a toroidal transformer without any regulation.
Fast forward to this week and the 48V ACDC PSU I using for the project in its daily use failed despite years of zero trouble from this amplifier. In the meatime, before replacement arrived, I used the 32V lab PSU and noticed the volume with the exact same input level was much lower but the sound quality was perfectly good.
I've been reading trough the TPA3255 datasheet but can't find anything regarding gain dependacny on the power supply voltage. The diagram shows that the internal feedback is taken from the output so the ratiometric voltage effect on H bridges should not apply here.
This symptom seems to be a key insight into my original problem. Does anyone have any insight or pointers?
Attached is the schematic.
Many thanks!