Sorry about that.

In order to reduce the voltage, you ca use a capacitor with a MOS transistor. The idea is to charge the capacitor to a certain level with impulse current and during the resting period of the first MOS, a second MOS will turn on and power whatever you want.

You can also use a thyristor.

I am just waiting for my order to test the DC-DC Converter. In the meantime, I found a problem on the Opto Isolator ISD74X. If the output voltage is 1.2 to 1.6 volts, the Microcontroller does not trigger. If it is below 1.2 volts it is ok. Please advise why only the other pair. Why the second opto it is working fine.

 

I have found the answer and I will post it for reference maybe our readers may encounter the same. Since we will reduce the voltage to the MCU to a low level to enable it, I have changed the pull up resistor from 10K to 39K.