Research And Design Of High Efficiency And Low Power Flyback Power Supply

Switching power supply is multi-disciplinary technology that integrated power conversion technology, modern electronic technology, automatic control technology and power semiconductor devices. It has gradually developed into one integrated technical discipline with the multi-disciplinary mutual penetration. Due to the simple structure, low cost advantage, flyback converter is widely used in miniwatt power supply application. The task of this subject is to design an isolated power supply module with low voltage input(9V~18V), dual output( ? 12V), low power output(10W). Flyback converter topology is used to design this module which is an internal auxiliary power supply in electric locomotives.Firstly, the history, development trend and the basic theory of switching power supply are briefly introduced in this paper, and a comparison of the flyback and forward converter, voltage and current mode control are shown to select the current mode PWM control flyback converter. Then, this power supply module is designed through three aspects which are magnetic component design, the feedback loop stability analysis and hardware circuit design. This paper mainly focuses on the following: the core loss calculation methods with non-sinusoidal excitation; Calculation of the transformer parameters; Revise of core air gap calculation method; Based on the transformer equivalent model, detailed analysis of RCD clamp circuit and a new idea about calculating RCD parameters are given; Based on averaged equivalent current model, the small-signal model of power stage in a flyback converter, the code of feedback loop system stability and some typical compensation networks are introduced; Calculation of the parameters of the various components and components lectotype are given; A new start-up circuit is proposed to enhance the power efficiency; A single-pole single-zero compensation network is designed to stabilize the feedback loop according to the loop stability criterion; Finally, the prototype is tested to verify the performance.