Low power consumption regulated power supply circuit with overload protection b

They have overload and short circuit protection functions.
The overload and short-circuit protection circuit is composed of transistor VT2 and diode VD . VTz also has the function of current amplification. The resistance
    of resistor Rz has a great influence on the protection characteristics of the circuit. When the resistance of R2 is larger, it has better protection characteristics , otherwise it has worse protection characteristics.