48V Start-stop System Bi-directional DC_DC Converter

With the increasingly prominent problems of atmospheric pollution and shortage of fossil fuels,according to the GB27999-2014 standard,The average fuel consumption of China's passenger car manufacturers must be reduced to 5L/100 k M before 2020,or face a huge amount of negative integral penalty.Pure electric vehicles have a process to become mature due to the lag of charging network construction and cost,etc.The 48 V start-stop system can reduce fuel consumption by 15-20% with less cost through energy recovery technologies such as brake energy recovery and electronic turbines.It is the most feasible solution to meet the fuel vehicle emission standards at the current stage.The bi-directional DC/DC converter is one of the core components in the 48 V start-stop system and plays a crucial role in the system.It is compatible with the traditional 12 V power supply system and is responsible for bidirectional flow of energy.Therefore,it is of great significance to develop a high efficiency,high power density automotive 48 V start-stop system bi-directional DC/DC converter.In this paper,based on the research status and application status of traditional bi-directional DC/DC converters,a fully digitally controlled active clamp forward bidirectional DC/DC converter is proposed.Analyzed the working principle of active clamp forward bidirectional DC/DC converter for detailed,introduced three kinds of techniques to improve the efficiency of the converter,and gives the implementation.According to the actual application requirements,the technical parameters of the bi-directional DC/DC converter were determined,and the main circuit of the 1.2k W converter on the high-and low-voltage side was designed(including the clamp circuit,filter circuit,switch tube selection,drive circuit design,and high-frequency transformer the design of).The STM32F334 microprocessor is used as the control core to design the bidirectional DC/DC converter software system.The simulation model PSIM is used to establish the simulation model of the active-clamp forward bidirectional DC/DC converter,and a 1.2k W system is built.prototype.Simulation and experimental results verify the correctness and feasibility of the theoretical analysis and prototype design of the active-clamp forward bidirectional DC/DC converter.The bidirectional DC/DC converter studied in this paper solves the problem of electrical isolation from the topological point,realizes the synchronous rectification technology and soft-switching technology of the switching device,reduces the loss,and reduces the electromagnetic interference.The active clamping technology is introduced on the basis of the forward DC/DC converter,and the bidirectional flow of energy is achieved through the configuration of the switching tube driving signal.The active clamp technology is introduced to effectively solve the magnetic reset problem of the transformer,and the energy remaining in the winding is returned to the power supply during the reset process to improve the efficiency;the secondary side uses the MOSFET to replace the traditional diode and passesthe power MOSFET transistor drive signal.The control makes it realize the synchronous rectification technology,further reduce the loss,improve the efficiency;The switch tube can also realize the soft switch technology,make the switch tube current stress,voltage stress reduce,reduce the current ripple.The fully digitally controlled active clamp forward bidirectional DC/DC converter has good stability performance and dynamic performance,and meets the application requirements of the 48 V start-stop system.