Power supply voltage selection circuit

The invention discloses a power supply voltage selection circuit which comprises a voltage division circuit, a comparator, a level conversion circuit, a power supply selection switch circuit and a VOUT short circuit detection circuit, when a VOUT end is short-circuited, the VOUT short circuit detection circuit generates positive Vdg voltage conduction due to the voltage difference between the VOUT end and a VIN end, and the VOUT short circuit detection circuit generates negative Vdg voltage conduction due to the voltage difference between the VOUT end and the VIN end. And the SELVOUTB of the level conversion circuit is pulled to the potential of the VIN end, the VOUT gating end in the power supply selection switch circuit is controlled to be closed, and the current from the VIN end to the VOUT end is quickly blocked. By improving the circuit structure and adding the quick switching circuit, when the VOUT is short-circuited, the comparator and the level switching circuit can be skipped, the VOUT gating end in