How do I limit the current on the output of a transformer?

Design Reviews
#1

I’m trying to build a TENs circuit and this is how I started out: https://www.circuitlab.com/circuit/xacuac/screenshot/1024x768/

I haven’t put the circuit on a breadboard yet, but the simulations on CircuitLab are not giving me what I was expecting. Instead of about 90V on the transformer output (it is a 1:10 transformer wired in reverse) I’m getting about 8 volts. Can anyone see the issue?

#2

After a quick look at your design,:
I’m not sure why you are using 2 MOSFETS. I Would recommend using a single one and to limit the current you should control the width of the pulse
applied to the gate of the MOSFET instead of the voltage level. So use a comparator instead of an opamp. For a reference of current mode control you should take a look at the internal diagram of an UC3845. That will give you an idea on how to implement cycle by cycle current mode control. Hope that helps!

#3

current limiting resistor?