DC to DC Converter voltage regulation

Thread Starter

Nik123456!!??

Joined Dec 14, 2022
4
Hi,
I have a circuit design problem. I am currently using a 500W DCDC converter with input 96V and output 13.5V 38A. My requirement is only 25A but i need the voltage to be a constant 13.8V. Right now I see the output voltage varying from 13.1V to 14.1V depending on load current. Is there a solution that I can use external to the DCDC Converter to fix the voltage at 13.8V?
 

BobTPH

Joined Jun 5, 2013
8,813
Is the converter open loop or closed loop? An open loop converter will vary with load, a closed loop can be regulated.
 

DickCappels

Joined Aug 21, 2008
10,152
What you are asking for is that the power supply voltage be in a closed loop. More information about the power supply is needed unless you are willing to crank up the output voltage from the pre-made power supply and then add an external regulator on the output.

I am thinking about a buck (switching) post regulator.
 

LesJones

Joined Jan 8, 2017
4,174
If you make the effort to trace out the schematic then someone MAY be able to make suggestions on how to make it into a regulated power supply.

Les.
 

BobTPH

Joined Jun 5, 2013
8,813
An open loop converter is only viable if the load is constant. What was the original purpose of this device? What are you using it for now?
 

DickCappels

Joined Aug 21, 2008
10,152
A car without a gas pedal would certainly be exciting, but I would not be interested in a ride in that! :- )

There are many applications for unregulated power supplies. Indeed no regulated supply has infinite loop gain. The only problem is that this time the supply seems to be too sloppy for the application.Let's see whether or not we can solve this problem,
 
A car without a gas pedal would certainly be exciting, but I would not be interested in a ride in that! :- )

There are many applications for unregulated power supplies. Indeed no regulated supply has infinite loop gain. The only problem is that this time the supply seems to be too sloppy for the application.Let's see whether or not we can solve this problem,
Presumably electic cars don't have a "gas pedal" - something more like a potentiometer I imagine? :)
Exactly right, there must be a way of taking an unregulated converter and tricking it to adjust the mark/space to maintain a set voltage over a required current range...
 

BobTPH

Joined Jun 5, 2013
8,813
Yes, that would make it a closed loop converter. But it might not be easy to do, depending on the existing design.

If I were doing this, I would probably keep the output stage and replace the PWM with a micro using feedback from the output voltage. Or even bolt on a DC to DC controller chip that is designed for use by external switches.
 
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