| The dynamic characteristics of the Switch Mode Power Supply(SMPS) is one of its numerous performance indicators, with good dynamic characteristics, SMPS will response rapidly, get higher regulation accuracy and better stability when the load changes. Small-signal modeling of the SMPS’ loop is a common method to analyze and design its dynamic characteristics. In practice, however, due to the extensive use of non-linear device, such as switching power management chip and isolation transformers, it makes small-signal modeling of the SMPS more difficult. In this paper, it detailed the modeling process of a high efficiency flyback switching power management chip application topology based on practical engineering application, and the paper also analyzed and designed its loop to get a good dynamic response.Fully understand and master the basic principle of common switching converter topologies and their control processes is the foundation of switching converter smallsignal modeling. Firstly, the paper introduces the SMPS’ principle, analyzes the working process of several basic topology. Then we introduce few modeling methods of the basic topologies, including the small-signal modeling method, the state-space average method and the equivalent models of switching devices.In order to design the compensation network for flyback switching power management chip application circuit, the paper completed the following tasks:First, it briefly introduces the basic principles of power management chips used in this paper. To make the open-loop characteristics analysis process of the flyback converter topology more concise, we also separate the application circuit to some modules.Then, during the analysis of a Pulse Width Modulator(PWM), the paper presented the design process of a special multi-mode PWM controller. The controller improve the efficiency by working at different modes when the loads change, this working method greatly reduce the switching losses and achieve high efficiency. This introduction of multi-mode technology brings a certain difficulty in circuit design, but it doesn’t make the loop theoretical analysis more complicated.Finally, modeling main circuit and establishing the transfer function, combining with the PWM circuit transfer function we obtained before, we get the transfer functionin addition to the compensation network. According to the design objectives and the compensation guidelines in SMPS, we use mathematical analysis software to compensate the main circuit and get the best dynamic response. The simulation and test results show that our work meets the basic requirements of this article. It is a good reference for the engineering practice. |
