10A Driver with Modulation , First attempt

[DashApple]

Update , I have remade the circuit as small as I could The OpAmps are on SOIC to DIP baords to keep wire lengths down with a Lipo supply for +-12V , this is the current results with a current flow of 0.5A

The first picture is the voltage on the mosfet gate , so there is oscillations on the output and the second picture is the current waveform though the sense resistor .

Thanks , I will try as you said and see if there are any improvements

NewFile5 by TwirlyWhirly555, on Flickr

NewFile6 by TwirlyWhirly555, on Flickr

IMG_0733[1] by TwirlyWhirly555, on Flickr

 

[djQUAN]

You can also try adding local decoupling. 100nF caps between V+ to gnd, and gnd to V- VERY close to the op amps.

Also try increasing the 10pF caps to slow down the op amps. Then once it is stable, you can decrease the value to the minimum possible to meet your maximum modulation speed.

 

[DashApple]

Thanks for the help , I replaced the first op Amp with a LF356N and re jigged a few components .

Now at 5V I get 8.1A , 256mV across the resistor and there is no oscillations and I can adjust the current too , there a tiny amount of ripple but nothing like before .

Ill get some scope shots soon

 

[DashApple]

Well I tested the 7W diode up to the 8A , Didn't on / off modulate it just used the variable current setting .

It worked , as this was just to test it ill now move over to a proper driver .

IMG_0748[1] by TwirlyWhirly555, on Flickr

 

[djQUAN]

glad you got it working :beer:

 

[The Lightning Stalker]

Why does that TEC controller have such a
big coil on it?

+2 when I can

 

[DashApple]

glad you got it working :beer:

Thanks : D , I just need to still see if there are any spikes when its modulated on / off

Why does that TEC controller have such a
big coil on it?

+2 when I can

Thanks : ) , Not sure really The controller is rated to 8A TEC current so that's probably why , The controller is " Bang Bang " style with a half bridge doing the switching ,