Power supply switching circuit

The invention provides a power supply switching circuit, which is characterized in that a lower-voltage power supply passes through a first resistor and a second resistor in sequence which are connected in series to be grounded; a high-voltage power supply passes through a fourth resistor and a fifth resistor in sequence which are connected in series to be grounded; the grid electrode of a first NMOS tube is connected with the common terminals of the first resistor and the second resistor, the drain electrode thereof is connected with the common terminals of the fourth resistor and the fifth resistor, and the source electrode thereof is grounded; the grid electrode of a second NMOS tube is connected with the common terminals of the fourth resistor and the fifth resistor, the drain electrode thereof passes through a seventh resistor and a sixth resistor in sequence which are connected in series to be connected with the high-voltage power supply, and the source electrode thereof is grounded; the grid electrode of a first PMOS tube is connected with the common terminals of the sixth resistor and the seventh resistor, the source electrode is connected with the high-voltage power supply, and the drain electrode thereof passes through a second diode as a first voltage output end; and the low-voltage power supply passes through a first diode as a second voltage output end. The circuit has simple structure, effectively reduces the area of a PCB, and has low power consumption and low cost.