Overcurrent protection circuit for TH78H5 adjustable integrated voltage regulator power supply

The circuit is a regulated power supply composed of TH78H5 precision
four-terminal adjustable integrated voltage regulator
. This power supply has the advantages of wide adjustable range of output voltage, large output current, few peripheral components, and no need for debugging. The disadvantage is that the
TH78H5 integrated voltage regulator has poor instantaneous overload capability, and overload protection must be added during use. In the picture, a TWH8751
is used for overload protection.
    Normally, relay KA is closed. When the regulated power supply is overloaded or short-circuited and the voltage at point A is lower than 1.6V, KA is released and
the working power supply of TH78H5 is cut off to achieve the purpose of protection.
    Adjusting resistor R4 can change the overcurrent setting value. Adjusting RP can change the output voltage value.