Power conversion circuit

A power conversion circuit, comprising:

• a first input circuit, configured to receive a first input voltage through a first input terminal;
• a second input circuit, configured to receive a second input voltage through a second input terminal, wherein the first input voltage is higher than the second input voltage;
• a linear regulator, configured to receive the first input voltage or the second input voltage to output an output voltage;
• a switch, having a first terminal and a second terminal, wherein the first terminal is coupled to the first input circuit, and the second terminal is coupled to the second input circuit and the linear regulator;
• and
• a switch control circuit, configured to output a control signal to open the switch when receiving the second input voltage that reaches a predetermined level, so that the first input circuit is disconnected from the linear regulator, and the linear regulator outputs the output voltage according to the second input voltage,
• wherein the switch control circuit comprises:
• a test circuit, configured to output an enable signal when determining that the second input voltage has reached the predetermined level;
• and
• a control circuit, configured to receive the enable signal and output the control signal,
• wherein the test circuit comprises:
• a first transistor, having a first source terminal, a first gate terminal, and a first drain terminal;
• a first resistor, coupled between the voltage conversion circuit and a first node;
• a second resistor, coupled between the first node and a ground;
• and
• a capacitor, coupled between the first node and the ground,
• wherein the first gate terminal is coupled to the first node, the first source terminal is coupled to a second node and is arranged to output the enable signal, and the first drain terminal is coupled to the ground.