Author Topic: DC Electronic Load  (Read 692 times)

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Offline KW

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DC Electronic Load
« on: January 23, 2019, 09:18:28 am »
Hi...

I am trying to construct a DC electronic load for a current rating from 0~5A. I found that there are different connection of resistors and capacitor at the Vout of the OP-AMP.

There are two sets of designs are taken from the Kerry D. Wong's blog by changing the model of OP-AMP and MOSFET are shown in the attachments below as Figure 1 (link 1) and Figure 2 (link 2).
The reference links are as below:
Link 1: http://www.kerrywong.com/2017/01/15/a-400w-1kw-peak-100a-electronic-load-using-linear-mosfets/
Link 2: http://www.kerrywong.com/2013/03/08/constant-current-dummy-load-in-an-hdd-cooler/

What is the difference between these two designs?
Kindly advise a suitable design to use in constructing a DC electronic load which has a current rating 0~5A.
 

Offline nsrmagazin

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Re: DC Electronic Load
« Reply #1 on: January 23, 2019, 09:43:19 am »
What is the problem with the circuit? If you are constructin the first one for 100A, I can not help you, do this at your own risk! For the second one I can help you, do this at your own risk!

If its only a current load that you need, you can use a potentiometer instead, but keep in mind that your wires need to be able to support at least 6A of current.
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Offline MasterT

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Re: DC Electronic Load
« Reply #2 on: January 23, 2019, 01:47:27 pm »
 

Offline mvs

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Re: DC Electronic Load
« Reply #3 on: January 23, 2019, 08:10:10 pm »
There are two sets of designs are taken from the Kerry D. Wong's blog by changing the model of OP-AMP and MOSFET are shown in the attachments below as Figure 1 (link 1) and Figure 2 (link 2).
...
What is the difference between these two designs?
In older design (link2) 1nF capacitor creates local negative feedback loop for AC to avoid oscillations.
In newer design (link1) he has used LT1636, opamp that can drive large capacitive loads. Compensation network (220pF and 150Ohm) is recommended in datasheet of LT1636. You can not replace LT1636 with TL071 here.


PS: IRF6201 is not suitable for electronic load. You need a lateral MOSFET or even special linear MOSFET, not a trench MOSFET.
It should be able to dissipate a lot of power, so you will need much better package then SO-8. Look for TO-220 or TO-247 packages and a big heatsink with fan.
Typical MOSFETs that you can find in 3-5A electronic load projects are IRFP150N, IRFP260N.
« Last Edit: January 23, 2019, 08:22:53 pm by mvs »
 

Offline MarkF

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Re: DC Electronic Load
« Reply #4 on: January 23, 2019, 11:41:01 pm »
Here is what I did. 
To have 0 to 5A range, you would need to change the sense resistor to 0.100 and have a serious heatsink and fan.

   

   
« Last Edit: June 05, 2019, 09:39:34 pm by MarkF »
 
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Offline not1xor1

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Re: DC Electronic Load
« Reply #5 on: January 24, 2019, 09:17:15 am »
Hi...

I am trying to construct a DC electronic load for a current rating from 0~5A. I found that there are different connection of resistors and capacitor at the Vout of the OP-AMP.

There are two sets of designs are taken from the Kerry D. Wong's blog by changing the model of OP-AMP and MOSFET are shown in the attachments below as Figure 1 (link 1) and Figure 2 (link 2).
The reference links are as below:
Link 1: http://www.kerrywong.com/2017/01/15/a-400w-1kw-peak-100a-electronic-load-using-linear-mosfets/
Link 2: http://www.kerrywong.com/2013/03/08/constant-current-dummy-load-in-an-hdd-cooler/

What is the difference between these two designs?
Kindly advise a suitable design to use in constructing a DC electronic load which has a current rating 0~5A.

the main difference is in the compensation network
I just wonder what is the reason for using TL07* rather than, e.g., LF356
From LF356 datasheet:
Quote
New Output Stage Allows Use of Large Capacitive Loads (5,000 pF) without Stability Problems
 


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