Level convert of serial port

The invention provide a level convert of a serial port for level convert between MCU and RS232. The invention is characterized in that the convert comprisesa first convert circuit, a second convertingcircuit, a common circuit and a protection circuit. The first conversion circuit comprises a PNP type transistor and a first current limiting member. The second conversion circuit comprises an NPN-type transistor and a second current limiting member. The common circuit includes: a cathode electrically connected to a fifth capacitor of the first conversion circuit; The protection circuit includesa first bi-directional TVS transistor electrically connected to the first conversion circuit and a second bi-directional TVS transistor electrically connected to the second conversion circuit. As thatlevel conversion is carry out by using independent electronic component, the circuit structure is simple on the premise that the communication quality of the serial port is guaranteed, and in addition, a protection circuit is