Author Topic: How to control Current in Regulated POwer supplies?  (Read 750 times)

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Offline techguru

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How to control Current in Regulated POwer supplies?
« on: April 04, 2018, 03:18:36 am »
Hi to all,,
            How to control Current in Regulated POwer supplies?
                      give me the methods, or reference Text or journal paper or design examples. Thank u all..
 

Offline Audioguru

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Re: How to control Current in Regulated POwer supplies?
« Reply #1 on: April 04, 2018, 05:11:49 am »
Most regulated power supplies also have current limiting or adjustable current regulation.
 

Offline David Hess

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Re: How to control Current in Regulated POwer supplies?
« Reply #2 on: April 04, 2018, 08:41:40 am »
Usually a current shunt resistor is placed in series with the output and the voltage across the current shunt resistor is used for feedback to an error amplifier which controls current.  The outputs of the two error amplifiers which control current and voltage are combined in so that the one which produces a lower output is in control.
 

Offline ledtester

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Re: How to control Current in Regulated POwer supplies?
« Reply #3 on: April 05, 2018, 11:06:39 pm »
Usually a current shunt resistor is placed in series with the output and the voltage across the current shunt resistor is used for feedback to an error amplifier which controls current.  The outputs of the two error amplifiers which control current and voltage are combined in so that the one which produces a lower output is in control.

On combining the error outputs I found this video explaining one way of doing it (starting at the 10 minute mark):



Some questions:

- Is this how it's done in real designs?
- I've run across the phrase "op amps with or-ed outputs". Does anyone have a link for an explanation of how that's done?

Btw - I found the entire series of videos (of which the above is part 3) to be a nice walk-through of the design of a linear power supply from first principles.

 
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Offline David Hess

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Re: How to control Current in Regulated POwer supplies?
« Reply #4 on: April 06, 2018, 01:06:05 am »
- Is this how it's done in real designs?

The example shown starting at 10:00 is normally how it is done but as the video shows, how it is implemented is important.

Quote
- I've run across the phrase "op amps with or-ed outputs". Does anyone have a link for an explanation of how that's done?

For operational amplifiers it means that the outputs are connected using diodes so either operational amplifier can reduce the drive to the pass transistors lowing the output voltage or current.  Since neither operational amplifier can provide drive to the pass transistor through the diodes in this configuration, a separate circuit provides current to drive the pass transistor and either operational amplifier reduces that current through the diodes as needed.

This is not the only good implementation of this idea however.  Another way is to have one operational amplifier provide limited drive current while the second reduces that current as required.  This avoids having to use a third circuit to provide the drive current.
 
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Offline ledtester

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Re: How to control Current in Regulated POwer supplies?
« Reply #5 on: April 06, 2018, 11:41:01 pm »
I found this example of how to or the outputs of op amps with diodes to achieve both CC and CV (starting around the 16 minute mark):


 
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Offline techguru

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Re: How to control Current in Regulated POwer supplies?
« Reply #6 on: April 15, 2018, 01:11:29 am »
Dear all,
              I want to control current using IC 723 voltage regulator. Kindly help me with circuit and schematics.
 

Offline Cliff Matthews

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Re: How to control Current in Regulated POwer supplies?
« Reply #7 on: April 15, 2018, 01:20:57 am »
Dear all,
              I want to control current using IC 723 voltage regulator. Kindly help me with circuit and schematics.
Is there a new requirement? or application similar to this?
https://www.eevblog.com/forum/beginners/need-circuit-for-current-adjust-circuit-for-lm723-ic/
 


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