Method And Theory Of Power/Signal Multiplexig Transmission Based On Power Electronics Circuits

This paper combines power electronics with communication technologies and presents a new method of integrating power conversion and digital signal transmission in power converter circuit, which is based on traditional power electronics circuit and PWM control technique. In time domain and frequency domain, the realizations of composite power/signal transmission, which are called power/signal frequency division multiplexing transmission(P/S FDMT) and power/signal time division multiplexing transmission(P/S TDMT), are analyzed.P/S FDMT system can be realized by power/signal frequency division composite modulation in the power electronic circuit, which is based on traditional PWM control and utilize the switching harmonic as a carrier to transfer data. There are two power/signal frequency division composite modulations:PWM/FSK modulation and PWM/PSK modulation. By composite modulation, the information of the data has been embedded in the input ripple and output ripple of the power supply. For the amplitude of the ripple is varied with the circuit topologies, input voltage, output voltage and load current, so it is essential to choose the topologies that the ripple range is relatively small. In the condition of constant output voltage and wide range of load current, by analyzing the input and output ripple of the basic DC/DC topology, it can be concluded:the input port of Boost circuit is suitable for ripple communication while the output port of Buck circuit is suitable, and the Cuk is suitable in both port while Buck-Boost is unsuitable in both ports.Take Boost Circuit as an example, this paper made a detailed analysis of the PWM/FSK and PWM/2PSK DSSS modulation. The principles for the selection of carrier frequency and carrier shape are deduced, and the digital demodulation algorithm corresponding to these two methods are designed. Finally, the experimental results verify the correctness of these two proposed methods.The basic principle of P/S TDMT based on power converter is utilize the gap of power transmission, in which data signal is transmitted. This method has the advantages of simple circuit structure and strong anti-interference capacity, but the output voltage can not be regulated. The equipment in the P/S TDMT system can be divided into two class:power sourcing equipment(PSE) and powered device(PD). A general method of designing a P/S TDMT system is proposed:Firstly, the sequence of the transmission slot in a period should be defined. Secondly, the circuits of sourcing power in PSE and the circuits of sinking power in PD should be determined. Lastly, data communication circuits be added to the PSE and PD. Several basic circuits for sourcing/sinking power and data communication are presented in the paper.For the instance that P/S TDMT system applied in distributed control system which has long transmission distance, the affections of transmission line should be considered. This paper investigates in detail the transmission process of switching circuit in the environment of transmission line. Theoretical analysis and experimental results show that impedance matching in the source can improve the voltage waveform at the end of the line, but unable to suppress the voltage of reflection spike as power turned off. Another way to eliminate the transmission line reflection effect is to increase the rise time and fall time of the pulsed power. A novel soft-switching circuit is employed as PSE sourcing circuit in which the rise time and fall time can be control by resonant time of L and C. The effectiveness of this circuit is verified by experimental result.To realize reliable data communication, communication circuit must be supported by appropriate communication protocol. This paper has also studied the protocol that suit for P/S TDMT system. In physical layer, the design of communication timing diagram and the calculation of transmission distance is discussed. In MAC layer, reservation-based protocol and competitive protocol are introduced. Finally, three examples applied in different circumstance are given, which show that P/S TDMT system have the advantages of convenient wiring, simple circuits, high anti-interference ability, and can adapt to different application.