I have a device that uses a 400mA 9v wall wart, and since I have 12V DC available (which powers an associated deice), I wanted to use a 9V step down regulator to power this device from the 12V. Unfortunately, the D24V5F9 I purchased did not work in this case. I see 9V out of the regulator under no load, but when I try to power the device with it, I see only 3V. Would it be reasonable to assume this is due to inrush current? What’s the most straightforward way to verify that? I think I’m just going to order the 1A version of the regulator (to be able to handle more startup current) and try again. Thoughts?
Hello.
I moved your thread to the “Voltage Regulator” section of the forum since it is more appropriate.
Could you try powering up the regulator with no load connected, verifying that it is outputting correctly, then connecting the load while it is already powered up? Also, if you haven’t done so already, it would probably be good to measure your 12V input source to make sure it is handling the additional load you’re putting on it (and not dipping).
Brandon
12V is fine, 9V into a 47 Ohm resistive load works fine. When I plug the 9V into my device it drops to ~3V. Measured 233 mA draw from device when powered from another 9V source (the wall wart). I don’t have a way to measure inrush, but I suspect that is the issue. Do you think the 1A regulator would be more likely to work?
The current could be causing a problem with the soft-start feature of the regulator. Just to clarify, did you try powering up the regulator fully before connecting the load, and it still dropped to 3V?
There is no 1A version of the D24V5Fx regulators, so it sounds like you’re referring to the D24V10F5. That regulator might handle it better, but to say with more certainty, it would be ideal to characterize the startup behavior of your load device more carefully (e.g. with an oscilloscope current probe or possibly a multimeter in peak current measuring mode, but that might not be fast enough to reliably capture it).
Brandon
Yes, I had powered up the regulator first. Perhaps it’s overcurrent protection instead of soft-start? Yes, I meant the D24V10F9 as the 1A replacement. (I already ordered one that’s arriving today). But now I’m thinking it may be easier to power my device from an available USB3 port using a USB to 9V cable I can get from Amazon for $10.