RS485 bus system containing power supply module

The invention discloses a RS485 bus system with power supply module, which comprises a RS485 receiving/transmitting circuit connected with the two differential signal lines of the RS485 in sequence and a terminal unit and further comprises a power converting circuit. The power converting circuit is connected with the two differential signal lines of the RS485, the RS485 receiving/transmitting circuit and the low-power mini terminal unit, respectively. The power converting circuit comprises a rectifying circuit, an input filter circuit, a voltage regulating circuit and an output filter circuit, which are connected in sequence. The power converting circuit is used for receiving a voltage from the two differential signal lines of the RS485 and supplying power to the RS485 receiving/transmitting circuit and the terminal unit. Preferably, the RS485 bus system with power supply module further comprises a diode and an energy-storage element, wherein the diode is connected in series between a filter capacitor and an output terminal and the energy-storage element is connected in parallel between the output terminals of the output filter circuit.