Hi CCSS,
I would be willing to bet that if you took a couple of 2000uF caps and wired them in series with a switch, you would get the same overshoot and OVP fault in the PSU. I suspect the huge overshoot of inrush current leads to a voltage spike upon recovery of the PSU. I don't think it has anything to do with the TPA3255.
I would be willing to bet that if you took a couple of 2000uF caps and wired them in series with a switch, you would get the same overshoot and OVP fault in the PSU. I suspect the huge overshoot of inrush current leads to a voltage spike upon recovery of the PSU. I don't think it has anything to do with the TPA3255.
It requires a hard power down to recover, which according to spec is how this PSU handles OVP. Hiccup mode is only for overcurrent protection on this one.
The internal wiring is all 16ga stranded (26 strands/30ga or 0.254mm each). I've tried several power cables between the PSU box and amp box (including a short 0.2m 14ga) and it makes no difference.
I really think the reason you're not seeing this is that the lrs-350-48 is rated to 52.8V, and can probably do more if it is like the mean well PSUs I have (they all exceed the spec voltage).
Link is in post 432. Also in the tiny little one is in this thread:
http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb-117.html#post5167921
@cccs, may you hook up a scope to plot the transient? Starting into empty caps shouldn't result OVP. May you try to test with separate capacitors what's the Max capacitance the supply can "cold crank"? Does it also happens when set to minimum output voltage?
Are any of the other supplies tested from "medical spec" like the actual?
Are any of the other supplies tested from "medical spec" like the actual?
Hi ccss
It looks like the two PSUs are over current protection when suddenly rise huge current to power up the amplifier board in no load power mode. Is it possible to place a dummy load on the 48V DC output of the PSU, such as an indicator lamp, to make the PSU always in load to prevent this error even not to switch on the amplifier board?
It looks like the two PSUs are over current protection when suddenly rise huge current to power up the amplifier board in no load power mode. Is it possible to place a dummy load on the 48V DC output of the PSU, such as an indicator lamp, to make the PSU always in load to prevent this error even not to switch on the amplifier board?
Finally captured the startup voltage spike...but not on the PSU that crashes. I'm still somewhat new to using a digital scope and I haven't yet been able to to capture the voltage spike on the RPS-400. so I used a different PSU, the mean well USP-500-48. This PSU does not crash but it does show the voltage spike. This is measured at the PSU. The biggest spike was one up to 65V, but that was not typical. I also tried different voltage adjustments on the PSU. The last attachment is the PSU that crashes.
I can't see any pattern here, other than the fact that there is invariably a surge on startup. And that is to be expected in some degree with any electronic device. I will have a current clamp for the scope later this week so I can measure the current surge as well.
I can't see any pattern here, other than the fact that there is invariably a surge on startup. And that is to be expected in some degree with any electronic device. I will have a current clamp for the scope later this week so I can measure the current surge as well.
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Cheers,
thanks for the plots. It would be better if you do measure as follows:
1. use 10:1 setting on probes
2. calibrate probes with 1kHz supplied by scope
3. set scope to 10:1 to have correct voltage labels
4. set to DC coupling
5. single shot trigger
6. capture the whole startup transient
From your plots, there's a lot of noise going on and it is unclear what scaling you use for X and Y.
I captured the startup of the LRS-350-48 set to ~51V:
Transient into connected TPA3255 with 2x2400uF:
Transient into no load:
No overshoot whatsoever.
thanks for the plots. It would be better if you do measure as follows:
1. use 10:1 setting on probes
2. calibrate probes with 1kHz supplied by scope
3. set scope to 10:1 to have correct voltage labels
4. set to DC coupling
5. single shot trigger
6. capture the whole startup transient
From your plots, there's a lot of noise going on and it is unclear what scaling you use for X and Y.
I captured the startup of the LRS-350-48 set to ~51V:
Transient into connected TPA3255 with 2x2400uF:
Transient into no load:
No overshoot whatsoever.
Attachments
Thanks very much for the tips. I wasn't using trigger in the previous shots. Here are some new ones. I think I am still doing something wrong because in these I only see voltage sag, not a spike. Voltage sag is around 30V.
rps-400-48 no-load startup:
rps-400-48 amp turned on:
usp-500-48 no-load startup:
usp-500-48 amp turned on:
hrp-100-48 amp turned on:
rps-400-48 no-load startup:
rps-400-48 amp turned on:
usp-500-48 no-load startup:
usp-500-48 amp turned on:
hrp-100-48 amp turned on:
Attachments
Apologies for using so much space in the thread for what turns out to be a very simple issue.
Here are the shots for the start-up current draw...first one is the PSU that crashes, the next 2 are a PSU that works.
The only issue is that the RPS-400-48 can't handle the startup load for the tpa3255 board. Per the spec, it can output up to 8.4A, but it shuts down at 2.54A if drawn too fast. The USP-500-48, with amperage adjusted to maximum, allows all of its rated 10.5A and doesn't crash.
Mean Well 48V PSUs that have a generous voltage adjustment range up to at least 53V include the HRP series, RSP series, and USP series if you want PFC, LRS series if you don't care about PFC. There's one smaller model in the RPS series, the RPS-160, which might work too.
So as you suggest I am using the PSU for on/off and leave the amp turned on all the time. I am undecided about adding a timed relay with shunt resistor as suggested by frammis. It would solve my issue but adds complexity.
Here are the shots for the start-up current draw...first one is the PSU that crashes, the next 2 are a PSU that works.
The only issue is that the RPS-400-48 can't handle the startup load for the tpa3255 board. Per the spec, it can output up to 8.4A, but it shuts down at 2.54A if drawn too fast. The USP-500-48, with amperage adjusted to maximum, allows all of its rated 10.5A and doesn't crash.
Mean Well 48V PSUs that have a generous voltage adjustment range up to at least 53V include the HRP series, RSP series, and USP series if you want PFC, LRS series if you don't care about PFC. There's one smaller model in the RPS series, the RPS-160, which might work too.
So as you suggest I am using the PSU for on/off and leave the amp turned on all the time. I am undecided about adding a timed relay with shunt resistor as suggested by frammis. It would solve my issue but adds complexity.
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Yes
Just noticed that you ask what speakers do I use. I use Radiotechnika S400Welcome to the Forum Linas.
What kind of speakers will you use the TPA3255 with?
just like this on the left in the photo attached in the link
http://evaizdai.lt/di/42FF/radiotechnika.jpg
Thanks for the suggestion. Because I wanted to be able to use the tpa3255 amp with some PSUs that can't handle the startup current, this is what I ended up doing. I found on ebay a buck converter to use as low voltage power source and an adjustable delay relay module. When I turn on the amp, DC power goes through a 100R/5W resistor for a few seconds, then the relay trips and bypasses the resistor. The relay is held closed while the amp is on. It works great and doesn't send any PSU into overcurrent or overvoltage protection.
I've moved on to building out the tpa3255evm, and for that project I am planning to use 2 delay relays, 1 for the startup resistor shunt and another to disable RESET. Delay times are set so the power shunt finishes before RESET is disabled.
But there are downsides:
* additional parts, which could fail, so I got spares
* more electrical noise inside the amp box, which could be addressed by putting the power shunt and the buck converter into a separate case outside the amp box
* higher energy usage (it's using a couple of watts to hold the relay closed), which could be reduced by using a more efficient relay, or changing the circuit so that the relay is held open instead of closed
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YJ-TPA3255 Board Test
just attach some test data here,with 4ohm load/48V SMPS
from the test it seems this board hasn't achieve the specification according to ti datasheet.
my board is very easy shutdown at high ouput even i re-add silica gel between TPA3255 and heat-sink again,but it didn't help.
so that will show at the THD+N plot, when output > around 250W,it drop due to the board shutdown.
just attach some test data here,with 4ohm load/48V SMPS
from the test it seems this board hasn't achieve the specification according to ti datasheet.
my board is very easy shutdown at high ouput even i re-add silica gel between TPA3255 and heat-sink again,but it didn't help.
so that will show at the THD+N plot, when output > around 250W,it drop due to the board shutdown.
Attachments
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