It is very important to observe the voltage drop on a power transistor, so switching windings is very useful. Otherwise, with an inept approach, you will receive burnt details and finances. I use a separate nutrition for LM324- 12V, when powerful from 24V, heated TL431 and R3 1K. Also, when powering LM324 from the total tire, and when the load is connected, the output voltage for some reason increases from the 1,5-2V. Therefore, a separate nutrition is better, and does not create excitement. I received a LBP with an adjustment of 0-40V, a load current of 5A. Great work of restrictions and protection, both trigger and from overheating of the power transistor. All elements are cold, including VT1-KT816. Once again, it is necessary to observe the voltage drop on the power transistor, and to make a small setup under your needs, both in terms of current and in existing protection, for which first delve into the operation of the circuit and the purpose of the elements.