Hi Guys,
I finished my PSU lunchbox for the 51X rack, that you maybe have seen?
And Harpo gave me some ideas for the noise issues i have and some other things, thanks to him.
One idea was maybe including a "crowbar" type protection, and a "tracking-shutdown" circuit as well to the PSU, two circuits that i wasn't aware of, and at the time of buidling this one
i was a little more concerned about the mechanical side of the build, omitting such things in the process, and some other things as well, you live you learn...
For those who don't know (like me) what is a crowbar circuit, there is some infos on the web for this one, a pretty simple circuit.
For the Tracking-shutdown circuit, Harpo was kind enough to provide a schematic taken from an Amek 9098EQ, that shows the tracking circuit.
Basically, it's a transistor (NPN for positive and PNP for negative rail of course) with collector connected to the voltage adjustement resistor of the Vreg (240R) and base kept at half supply voltage, using a voltage divider. So if one supply rail gets to fail, it will drop the opposite rail voltage down... (still need to try that out)
The crowbar is a pretty rude type of protection but it's effective, i tried it out, and the only minus to it, is that you need a pretty hefty
power Transformer to provide sufficient inrush current to blow the fuse when voltage has exceeded the desired threshold.
My little circuit was based on a TL431, a transistor and an SCR as most seen on the web.
I tried the circuit using a LAB PSU, and found that, for blowing the fuse it still takes a little time where the PSU gets a short, and i'm not sure if the Toroidal in situation will like it.
I'm not a pro in those domains, but try to do and understand the best i can.
I've actually stumbled into some, maybe more "fancy" ways of overvoltage protection, one was including a Linear Technology LTC4366 chip, that seem to provide MORE than enough protection, not sure if that would be an option, since it's made for "Surge" protection but could be, if so then a little expensive one, 8$ for the chip in SOT23-8 Package OUCH.
But when i think about it, since it's meant to protect DOA's and IC's etc... beeing vintage or new or whatever, at the end dunno if it's that much of an expensive option.
Dunno how it will behave in real world situation and beeing used on +/- rails, as well as noise and all, since some care must be taken for the components placement, and layout etc.....
Anyway that's maybe beeing overprotective at the end, but since Harpo gave me some food for tought, i'm having hard time taking this out of my mind now ;D
So i was just wondering what you guys would use as an overvoltage protection, or maybe could direct me to some things to look at etc....
Thanks a lot for your help, much appreciated.
T.
I finished my PSU lunchbox for the 51X rack, that you maybe have seen?
And Harpo gave me some ideas for the noise issues i have and some other things, thanks to him.
One idea was maybe including a "crowbar" type protection, and a "tracking-shutdown" circuit as well to the PSU, two circuits that i wasn't aware of, and at the time of buidling this one
i was a little more concerned about the mechanical side of the build, omitting such things in the process, and some other things as well, you live you learn...
For those who don't know (like me) what is a crowbar circuit, there is some infos on the web for this one, a pretty simple circuit.
For the Tracking-shutdown circuit, Harpo was kind enough to provide a schematic taken from an Amek 9098EQ, that shows the tracking circuit.
Basically, it's a transistor (NPN for positive and PNP for negative rail of course) with collector connected to the voltage adjustement resistor of the Vreg (240R) and base kept at half supply voltage, using a voltage divider. So if one supply rail gets to fail, it will drop the opposite rail voltage down... (still need to try that out)
The crowbar is a pretty rude type of protection but it's effective, i tried it out, and the only minus to it, is that you need a pretty hefty
power Transformer to provide sufficient inrush current to blow the fuse when voltage has exceeded the desired threshold.
My little circuit was based on a TL431, a transistor and an SCR as most seen on the web.
I tried the circuit using a LAB PSU, and found that, for blowing the fuse it still takes a little time where the PSU gets a short, and i'm not sure if the Toroidal in situation will like it.
I'm not a pro in those domains, but try to do and understand the best i can.
I've actually stumbled into some, maybe more "fancy" ways of overvoltage protection, one was including a Linear Technology LTC4366 chip, that seem to provide MORE than enough protection, not sure if that would be an option, since it's made for "Surge" protection but could be, if so then a little expensive one, 8$ for the chip in SOT23-8 Package OUCH.
But when i think about it, since it's meant to protect DOA's and IC's etc... beeing vintage or new or whatever, at the end dunno if it's that much of an expensive option.
Dunno how it will behave in real world situation and beeing used on +/- rails, as well as noise and all, since some care must be taken for the components placement, and layout etc.....
Anyway that's maybe beeing overprotective at the end, but since Harpo gave me some food for tought, i'm having hard time taking this out of my mind now ;D
So i was just wondering what you guys would use as an overvoltage protection, or maybe could direct me to some things to look at etc....
Thanks a lot for your help, much appreciated.
T.
