Simple power supply or conditioning circuit for decisive power-on edge - Page 1
Forum section: electronics / projects

author: jmbreuer
author_rank: Newbie
timestamp: February 20, 2024, 06:06:27 pm
content: Hi,I'm faced with one of those niggling problems where I kinda (think that I) know what the issue is, and how I might fix it in a world where expense would be of no object.However, I'm fairly constrained financially, so I'm looking for a cheap/simple solution.I have a device (Hi-Fi DAC, MusicalFidelity V-DAC IIhttps://www.musicalfidelity.com/uploads/catalogerfiles/v-dacii/4_VDACii_24-96asynchUSB_manual.pdfif that's of any help) that I want to completely power off along with my stereo system when it's not in use. I got some Shelly / Tasmota WiFi power plugs for that.Now, it turns out, powering up the device by turning on the primary side of its power supply will about half of the time result in an error state where it will output an annoying buzz, and none of the digital audio fed to it. Power cycling itcanhelp, I've made the following observations:Power cycling the AC adapter helps some of the timePower cycling by removing the DC plug from the device and re-plugging it helps all of the time(s that I've tried)My informed guess is that the power-up ramp of that power supply might not quite meet the expectations/peculiarities of this device (and apparently both the device and its power supply lack a suitable internal reset controller). This guess is corroborated by the fact that the power supply has a power indicator LED, that slowly fades out when it is turned off. Upon being turned off this way, the DAC will output a significant pop and turn itself off quite early in the down ramp.How would I go about finding a simple/cheap/wall-plug-type power supply (12V, 1A) that would exhibit a clean power-on edge rather than a ramp? I'm in Germany, as far as AC power and available brands are concerned.Or, alternatively, is there a simple circuit I could implement on the DC side to delay passing power to the device until after the ramp has passed, or similar.?Thanks a lot for any and all pertinent suggestions!

author: jonpaul
author_rank: Super Contributor
timestamp: February 21, 2024, 12:59:51 am
content: Hello your note shows one of the classic symptoms of IC initialize failuer, esp te random fails.NO off the shelf power supply will have a controlled turn on with fast edge.Designer of ANY device is responsible for proper turn on/init/rest ckt IN ORIG DESIGN. with a standard power source!!Either1/ Device is defective, and needs replacement/repair2/ Device was poorly designed and tested contact mfg for refundbon chanceJon

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 21, 2024, 03:22:45 am
content: A ready made Li battery under voltage lockout board could do. A typical schematics is ashttps://www.circuits-diy.com/low-battery-voltage-cut-off-or-disconnect/,You’ll find many sellers of the same circuit on EBay and Ali. The relay will give you a nice snap.

author: jmbreuer
author_rank: Newbie
timestamp: February 21, 2024, 11:44:06 am
content: Thanks a lot, exactly the answer I was hoping for!I found a cheap ready-made board and will give it a try.

author: jmbreuer
author_rank: Newbie
timestamp: February 21, 2024, 11:49:22 am
content: Hi Jon,thank you. I understand where you're coming from; it's still something I want/need to 'solve' myself.The device is 15 years old (so no warranty or such), and the manufacturer mentions that it's only supposed to be run with its own, "included", dedicated power supply - which I take to understand, they're kinda aware of some issue there.That said power supply I never got in the first place, because I live in a different power socket standard country from the manufacturer. The one I picked out those oodles of years ago worked OK most of the time, when my usage pattern was to rarely turn it off at all. That has changed now.And I wouldn't want to return the DAC in the first place, because in the performance characteristics that matter to me it's a perfect fit and has been for a long time.So long,Joe

author: jmbreuer
author_rank: Newbie
timestamp: April 07, 2025, 05:45:30 am
content: OK so this took me a while, "life happening" and such.But, for posterity: I found a ready-made voltage monitor / lockout module, and it works  perfectly for my use case.I got this exact one:https://www.amazon.de/Heemol-Batteriew%C3%A4chter-Pr%C3%A4zisionsmodulen-Programmierbarer-Unterspannungsschalter/dp/B09GFL2CQ7/I guess there are oodles of copies of this design available globally.On the "almost" above: In maybe one in 30-45 power on events, the DAC still does not initialize correctly, but that's a fail rate I can live with (and simply power toggle it again when that happens).So, big thanks again to@dobsonr741for suggesting this solution!