how do i design an electronic load.....??

[shreeks9]

electronic load irf

hi ........

i need to design an electronic load with the following spec's 240v,240w,1A.I tried doing tht with power mosfet's (IRF 840)but thier linearity region was limited to about a max of 20v.So i desperately need new ideas to design this electronic load.am new to the group and will be glad hear from u guys....

cheers
shreeks

 

[IanP]

electronic load design

Maybe you can consider switching dummy load .. it doesn't have "problems" with linearity ..
Here is one example of such a load:
**broken link removed**
Of course, for 240Vdc it has to be modified and you can add several R-MOSFET circuits in parallel ..
Also, power supply for the control circuit has to come from somewhere else, or has to be "safely" lowered ..

Regards,
IanP

 

[shreeks9]

hmmm....tht concept of dummy load was gud.but iam sorry , i forgot to mention tht my requirement was not jus switching alone but also to vary the voltage.thx for the reply anyway ,gave me a direction.


cheers
shreeks

 

[VVV]

Please see my reply to your other post on the same topic

 

[melc]

hi ........

i need to design an electronic load with the following spec's 240v,240w,1A.I tried doing tht with power mosfet's (IRF 840)but thier linearity region was limited to about a max of 20v.So i desperately need new ideas to design this electronic load.am new to the group and will be glad hear from u guys....

cheers
shreeks

The basic ideea shows by vvv in the indicated post is ok. You need a controlled curent source. You can't do it with one (even with 2 IRF840) because of huge power dissipation on the TO220AB package.
The non linearity problem comes from the feedback of the controlled constant generator or from the limitation in driving circuit. Near zero the OA will not be liniar too. You need also a protective zenner circuit in the gate to avoid reversible breackdowns via Vdg which could appear and distroy the driver's output.
You have to equilibrate the drain-source currents on the IRF using limiting resistors on every sources and a common sensing resistor. The sensing resistor must be keept cold over the whole load variation.