Voltage Source Design For Power Supplying Two-wire Bus System

For the existing two-wire bus system,the signal transmission is easily disturbed,with the advantages of short transmission distance,low transmission efficiency and poor load capacity,this thesis designs a kind of voltage source for the two-wire bus system for medical call system,which is a two-wire system bus technology which can carry out signal lossless transmission simultaneously in power supply,the voltage source can realize the transmission of digital signal and speech signal at higher baud rate with large load operation.During voltage source circuit designing,the circuit was divided into a reference voltage source module,a driving circuit and a power amplification module,a current detection module,and a coupling circuit module,which were analyzed and designed separately.In order to meet the requirement for the voltage source to carry heavy load,the voltage source was designed to have an output current up to 20A when the voltage reached 42V.There are two modes of signal transmission for the two-wire bus system designed in this thesis:one is that the host node transmits information to the extension node via a voltage signal,and the other is that the extension node transmits information to the host node through a current loop signal.The difficulty of this design lies in how to obtain and process the current signal transmitted by the extension from the bus.Therefore,the current detection circuit will detect and acquire the current signal on the bus and convert it into a voltage signal,and then the obtained voltage signal is subject to a series of operations to obtain the desired digital signal and voice signal such as amplification,coupling,filtration,differential amplification.The thesis carried out simulation tests and real prototype tests on each module of the voltage source,and adjusted related parameters by comparing the simulation and the real test results to determine the overall voltage source circuit of the two-wire system bus system.The real test shows that the designed voltage source can work stably for a long period of time under heavy load conditions and meet the design requirements.