Power Supplies

Thread Starter

mlkcampion

Joined Nov 16, 2006
59
Is it possible to limit how much a power supply can supply to a load. For example i have a 250w power supply where under normal running the load draws about 150w at 24vDc. However on start up the current draw overshoots and can draw upto the maximum the power supply can give for about 2 minutes. What i'd like to do is limit the power supply to give say 160watts at any time?
How do i go about this?

Thanks
Michael
 

Papabravo

Joined Feb 24, 2006
14,459
Is it possible to limit how much a power supply can supply to a load. For example i have a 250w power supply where under normal running the load draws about 150w at 24vDc. However on start up the current draw overshoots and can draw upto the maximum the power supply can give for about 2 minutes. What i'd like to do is limit the power supply to give say 160watts at any time?
How do i go about this?

Thanks
Michael
Yes, I believe it is possible. Most lab supplies have both a constant voltage and a constant current setting. The constant current mode allows any amount of current at the voltage setpoint upto and including some maximum. When the maximum current is reached the regulation circuit keeps the current constant and drops the voltage. That's not quite what you asked for; it is not constant power.

To do a multimode supply with your own circuitry is a bit more complicated, but still doable. You have to make sure the cost of building, what is mass produced in Asia, is worth it to you for some reason.
 

mrmeval

Joined Jun 30, 2006
833
You could use on of these.
http://www.ametherm.com/Inrush_Current/inrush_current_faq.html

It's at a very high resistance at first then reduces resistance as it gets warmer. You'd have to check if this would be compatible with your circuit.

Another variant that would need scaled up to your currnet limit.
http://www.discovercircuits.com/DJ-Circuits/lampcurrentlimit.htm

Nice article on inrush limiting with a circuit.
http://www.edn.com/article/CA244147.html

More
http://www.st.com/stonline/products/literature/ta/9115.pdf
 
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