Hi all,
I custom built an 8 channel amplifier made from 4 separate TPA3255 dual channel amplifiers with a microcontroller coordinating their reset based on time and the input voltage levels. They all exhibit the same issue.
The issue is, when I first turn the amplifier on and it's at room temperature, the TPA3255 will be brought out of reset after the the microcontroller has seen the power supplies have settled (12V and PVDD) then the microcontroller will connect the speakers through the output relay. Now, everything will be fine for approximately 3-5 seconds when the TPA will go into fault mode (FAULT -> 0 and CLIP_OTW -> 1). The microcontroller then disconnects the amplifier by turning off the relays, puts the TPA3255 into reset, waits 1s, brings the TPA3255 out of reset then connects the speakers via the relay once again. Now the cycle repeats for about 10mins until the heatsinks are a little warm to the touch.
Could anyone suggest why the TPA3255s might be behaving this way? Attached is my schematic.
Many thanks,
Boscoe
I custom built an 8 channel amplifier made from 4 separate TPA3255 dual channel amplifiers with a microcontroller coordinating their reset based on time and the input voltage levels. They all exhibit the same issue.
The issue is, when I first turn the amplifier on and it's at room temperature, the TPA3255 will be brought out of reset after the the microcontroller has seen the power supplies have settled (12V and PVDD) then the microcontroller will connect the speakers through the output relay. Now, everything will be fine for approximately 3-5 seconds when the TPA will go into fault mode (FAULT -> 0 and CLIP_OTW -> 1). The microcontroller then disconnects the amplifier by turning off the relays, puts the TPA3255 into reset, waits 1s, brings the TPA3255 out of reset then connects the speakers via the relay once again. Now the cycle repeats for about 10mins until the heatsinks are a little warm to the touch.
Could anyone suggest why the TPA3255s might be behaving this way? Attached is my schematic.
Many thanks,
Boscoe
Hi,
It looks like you are using the TPA3255 in Single Ended mode. The output inductor should be 15mH as per the data sheet, but you have omitted the capacitor in the output of each speaker connection.
Regards,
Shadders.
Hi Shadders, thank you for your reply. I am using them in BTL mode (M1 and M2 are GND).
I understand now that my design is oscillating which is the root of these problems. Just investigating this now.
I understand now that my design is oscillating which is the root of these problems. Just investigating this now.