High Power Current Source

Hi,

I use lm324 op-amp and feed signal to non-inverting input.
Inverting input gets feedback to source of IRF640 power mosfet and source connected to GND with 10 Ohm resistor.

Please keep in your mind gate connected to output of LM324 and drain connected to transformer and other input of transformer connected to VCC=12Volts.

I can't find sine wave on other side of transformer

Please help me.

Regards

Post schematics, otherwise any ansver I might come with is just wild guesses.

Hi,

This is my schematic.
" "" I WANT TO CONVERT VOLTAGE TO CURRENT AND FEED IT TO TRANSFORMER TO CHANGE LEVEL"""
My circuit on PULSE INPUT works good but I can't use it for sine wave(Full Rectified with 100Hz )

Please let me know your opinion.
Help me, please.

Regards,
Ronak

Please consider the answer to your original post.

You surely get core saturation, and possible output overload, depending on the unsaid transformer windings ratio.

As FvM says, you'll never get a good sine wave output. Reason is that you're feeding the transformer with DC current.

I beleive as you tune frequenzy and current, you might get something out, but it wont be a nice looking sine wave.

Hi,

I test my circuit and simulate it.
I found MOSFET can't get in active mode.

I'm confused!!!

Regards,
Ronak

Apart from the said problems of driving DC current to transformer, LM324 won't work well at 100 kHz. You can't connect two voltage sources in parallel and driving the LM324 input below negative supply would immediately burn the device.

You also didn't tell a transformr specification.

Hi,

Thanks in Advance.
My transformer is step up transformer and converts 12volts to 70volts!!

Regards

I agree with the replies above that there is not an adequate current path (AC current) to drive a transformer. I hope you've found the replies helpful.
But I find the circuit interesting and unusual and would like to know what it is really for. Its called 'High Power Current' but your description doesn't require any more than a few tens of milliamps into the load. That's not 'High Current'. And there is that redundant non-inverting input op-amp. Is there some other processing required?
What is this circuit for, and what kind of load is it expected to drive?
That might make it easier to help.

If it helps you, I wonder if you should be looking at a simple audio amplifier? This would have 2 simple output devices in push-pull and a feedback loop around them to maintain the sine waveform. If your circuit is mains powered you could use the expense and weight of your output transformer in the mains transformer so that your circuit operates between +35v and -35v power rails.

Hi,
Thanks for your reply.

Actually, I want to design a TENS stimulator and my load is muscle.
When we apply current to muscle its resistance gets lower and current gets up!!!(V=IR)
This occurs for constant VOLTAGE MODE.

According to that, I have to use CONSTANT CURRENT MODE application and I should feed transformer with current source.
In my application, output current is about 70mA for 1KOhm load.(V=IR=70Volts)
For this reason I used transformer.
Input voltage of transformer is 12 volts and if I want to have 70Volts at output, my input current should be in AMPER level!!!
This is my thesis project.

If you have other useful circuit please help me.
I am confused!!!

please let me know your opinion.

Regards.
Ronak

With 12:70 windings ratio, 1 k load and 12 V supply, the current source can drive undistorted about 0.3 A to the transformer, respectively 50 mA to the secondary. The reduction is due to to the sense resistor voltage drop.

I don't think, that 100 kHz is suitable for TENS, I doesn't work with LM324. If the transformer is designed to carry a DC current, the circuit can possibly work, but it would be better to use an AC current source.