Hi guys.

I'm developing a power supply with remote sense capability. I don't want to discover hot water again so I would like to see what have people already done on this topic. Unfortunately, I didn't find ANY circuits by Google concerning remote sense.

If you know some book or site please share.

Thank you
Ivan

 

Remotely sensing what?

B. Morse

 

Here is a link - http://power-topics.blogspot.com/2008/07/what-is-remote-sensing.html

The method uses the remote sensing wires to be used by the error amplifier to control the voltage at the point of use rather then at the immediate output of the pass element.

 

Here is a link - http://power-topics.blogspot.com/2008/07/what-is-remote-sensing.html
The method uses the remote sensing wires to be used by the error amplifier to control the voltage at the point of use rather then at the immediate output of the pass element.

Hi,
thanks for your reply.
I already found the site you provided but it gives no information about the actual implementation.

Well, I will just do the best I can and hope that there isn't a better solution Certainly, one or two opamps will be employed only to accomodate remote sensing.

Answer to the question before: Remote sensing the voltage at the load side so that voltage drop on cable resistance can be alleviated.

 

Answer to the question before: Remote sensing the voltage at the load side so that voltage drop on cable resistance can be alleviated.

That is what I thought you were asking, never know what people are thinking till you ask .... Just didn't want to get the wrong assumption.....

B. Morse

 

You might get more hits if you try searching on 4T sensing.
http://en.wikipedia.org/wiki/Four-terminal_sensing
Or just click here: http://www.google.com/search?hl=en&q=4+wire+measurement

[eta]
One thing to keep in mind when doing remote sensing is that you can easily wind up with oscillations if you don't provide damping for the voltage sensing. The supply and return lines will have a significant amount of inductance; that will provide enough of a phase shift to cause oscillation.

 

One thing to keep in mind when doing remote sensing is that you can easily wind up with oscillations if you don't provide damping for the voltage sensing. The supply and return lines will have a significant amount of inductance; that will provide enough of a phase shift to cause oscillation.

Hi. I'm aware of that. That is the main reason I'm searching for working solutions on the web. Since I have no luck, I'm developing the thing myself. Damping is a major concern in my design.

 

One danger of remote voltage sensing is the unlimited rise of output voltage should the feedback signal become lost, due to a break in the feedback wire.

Under this condition full voltage will be applied to the load and can cause considerable damages.

The usual way to safeguard this happening is to parallel a diode across the output lines and the feedback lines at the regulated power supply side, or use a 100Ω resistor to replace the diode.

 

One danger of remote voltage sensing is the unlimited rise of output voltage should the feedback signal become lost, due to a break in the feedback wire.

Under this condition full voltage will be applied to the load and can cause considerable damages.

The usual way to safeguard this happening is to parallel a diode across the output lines and the feedback lines at the regulated power supply side, or use a 100Ω resistor to replace the diode.

Another way to safeguard a runaway power supply is with a crowbar circuit.

The SCR over voltage crowbar or protection circuit is connected between the output of the power supply and ground. The zener diode voltage is chosen to be slightly above that of the output rail. Typically a 5 volt rail may run with a 6.2 volt zener diode. When the zener diode voltage is reached, current will flow through the zener and trigger the silicon controlled rectifier or thyristor. This will then provide a short circuit to ground, thereby protecting the circuitry that is being supplied form any damage.

 

One danger of remote voltage sensing is the unlimited rise of output voltage should the feedback signal become lost, due to a break in the feedback wire.
Under this condition full voltage will be applied to the load and can cause considerable damages.
The usual way to safeguard this happening is to parallel a diode across the output lines and the feedback lines at the regulated power supply side, or use a 100Ω resistor to replace the diode.

Hi, thank you for the diode tip.
I will apply it definitely. There is a possibility that feedback will be implemented using digital signal processing since that gives me some nice possibilities. In that case diode can be omitted.

 

No, It shouldnt be omitted at all. If there is a uC failure, you will have an issue.

You want a path based fail-safe. If the feedback line from the UC fails, it must route the power to ground. This is also a good place to add the big RED "Somethings Broke" LED. If the SCR is conducting, light an LED with some of the juice. It will help tell you WHERE the problem occurred.

By the way, what size PS are you thinking about, and what size loads?

 

Another way to safeguard a runaway power supply is with a crowbar circuit.

Sure.

Try putting one on a power supply with variable output voltage. If you succeed, you might submit the idea to an electronic magazine and get some prize. Been there, done that.