Design And Research Of Constant Current Source Based On Asymmetric Half Bridge

With the power more important in people's lives and the rapid development of power electronics technology,the switching power becomes smaller,more efficient.In order to reduce the switching losses in the development process,soft-switching technology was born.Many of the topology with soft switching characteristics has gradually become a hot spot in the field of power electronics research.As the asymmetric half-bridge circuit not only in the circuit structure than the half-bridge circuit is simple and the use of the topology itself can achieve zero voltage switch.However,the presence of DC bias voltage in the transformer and the diode circuit imbalance,this paper proposes the use of symmetric control to improve the problem in the circuit based on the research contents of asymmetric half-bridge between domestic and foreign scholars.Firstly,In this paper,the switching state and steady-state operating waveform of asymmetric half-bridge are analyzed.The reason of the transformer bias problem in the circuit is introduced.Then,the switching state of the circuit with symmetrical control is analyzed to obtain the transformer and diode waveform under symmetrical control.And then derive the circuit steady-state output voltage calculation formula and the output current CCM / DCM boundary conditions.Secondly,using PSIM software establish the traditional asymmetric half-bridge simulation model,the circuit current loop and closed loop simulation.The simulation results are compared with the waveforms of the transformer and the switch in the circuit under the traditional control.The simulation results verify the use of symmetrical control of the circuit transformer bias problem improvement.Finally,based on the circuit simulation parameters,design the main circuit of the converter and the control circuit in the control chip UC3825 peripheral circuit.And then use Altium Designer 10 to complete the converter schematic and PCB.the experimental experiment of the converter is carried out on the experimental platform and the working state waveform of the converter is obtained.The experimental results are verified and the circuit of the traditional asymmetric half bridge is improved by the proposed control strategy.