help need to design a constant current source.

I want to design a 20 amp constant current source and voltage at 200 Millivolt.

Hi,

what does the 200mV mean?

Is it the maximum voltage it may use to "regulate" the current?
This is just a resitance of 10mV. Even the wiring will be hard....

Please give more informations.

Schematic, specifications like frequency, accuracy, precision...

Klaus

Thanks for help,
.
For the shunt calibration i want to flow current of 20 amp in copper strip at pcb.

very low voltage as 200 Milli volt for low power use.

so i want to design a power supply of output voltage of 200 milli volt and 20 amp.

If I take 200 mV as the max compliance voltage, the max resistance will be 0.2/20=0.01 Ohms - this will be tricky.

For a shunt, you should use a 4 point measure system- two terminals for current and two terminals for voltage.

Hi,

No I assume you want to calibrate your copper shunt, wich desiredvalue is 10 milliohms.
Am I right?

If so, what is your supply voltage?

Copper shunt?..
Don't wasre much time on calibrating a copper shunt...it will change about one percent every 4 degree in copper temperature change.
So don't expect precision.

Klaus

Best way to do this might be with a home built Wheatstone bridge.
You will need some calibrated reference shunts to measure against.
You can then use a much lower and more manageable current for measurement of large shunts.

Doing it your way, you will still need a calibrated reference shunt to compare against, otherwise how are you going to know your 200 calibration amps are not 207 amps, or 191 amps ?

In order to prevent self heating errors,current shunts are typically 50mV full scale for 20A. But for 200A , I suggest 5mV drop for 1W dissipation. Then use low offset high CM Op Amp or special Current sense amp,

Try to work around this instead.
This means 250uΩ using wide strip for low inductance and good heat dissipation. The current injection points ought to be at least the conductor width longer on each side, than the V sense points. Use the ampacity tables for copper weight and track width and multiply by 3 or more in width.

You can even use cheap steel flat bar instead of Copper with a smallish 1" length.

I suggest threaded bolts and suitable spade lugs for 200A with washer to busbar to increase contact area to match or exceed width. This should get you down to 50 µΩ contact resistance on oxide free gas tight flat contact with suitable torque with fine machine threads , then mounted to PCB , then tiny screw tap calibrated hole span for 500 uV using a precise 20 A DC load current etc. or any current and compute V/R ....From then on use an IC for 5mV full scale high rail current shunt like used in automotive or DIY with high CMMR using twisted pair sense lines. This will likely need to be chopper stabilized for zero Dc offset.

A piece of stainless steel or zinc steel is way cheaper than a 200A copper PCB.


btw 200 mV at 200A is a 40 Watt heater, not an ammeter