At the negative end of the output with a small resistance value resistor sampling, take out the 0.001v voltage, with lm358 amplification to 2.5v, add a diode isolation into the PWM voltage sampling control foot, you can achieve voltage regulation, cross flow, change the magnification can adjust the current. The overcurrent protection circuit is modulated into a constant current mode. Or string a resistor in the output loop to sample the output current for constant current feedback.