Research And Realization Of A Novel High-Frequency Switching Power Supply For Wide Input Voltage

The modem electronic equipments cannot do without the reliable power supply, and have more and more high expectations for it. Distinguished from traditional Stabilized Voltage Power Supply, in order to stabilize its output voltage, Switching Power Supply regulates the duty ratio of the power semiconductor device. After nearly half a century of development, Switching Power Supply has replaced traditional Stabilized Voltage Power Supply because of smaller, lighter, less consumption, more steady performance, higher efficiency, etc.The main component of Switching Power Supply is DC-DC Converter. At first, the principle of Buck Converter, Boost Converter, Buck-Boost Converter and Boost-Buck Converter is analysed in the thesis. Then, the topologies of Forward Converter, Half-Bridge Converter and Full-Bridge Converter are discussed. Last, Flyback Converter is detailedly researched in the thesis, Flyback Converter evolves from Buck-Boost Converter. In Two-Transistor Flyback Converter circuit, a power semiconductor device in Flyback Converting circuit has been replaced by two power semiconductor devices which parallel connected with an ultra-fast diode with soft recovery characteristics. Two-Transistor Flyback Converter can reduce greatly the switching stress of the power switch and does not need to degausser, suitable for high input voltage Switching Power Supply.Another focal point of the switch power is controller. Switching Power Supply has three kinds of control circuits: Pulse Width Modulation (PWM), Pulse Frequency Modulation (PFM), Pulse Width and Frequency Modulation (PWM-PFM). First, the control principle and working characteristic of PWM, PFM, PWM-PFM is discussed in the thesis. PWM-PFM control has PWM and PFM specialties. As it can vary work frequency and duty ratio at the same time, it has better modulation performance. Then the principle of the PWM-PFM control circuit being made of the discrete component is analysed in the thesis. There arc less components in this control circuit, and Switching Power Supply with it can endure wide input voltage.The magnetic component plays a very important role in Switching Power Supply, for instance energy storage, converting voltage, filtering waves, etc. Four kinds of working state of the magnetic component is briefly introduced, and the calculation of the main parameters of high-frequency transformer and the choice of the magnetic core and Litzendraht line (high-frequency excitation line) is discussed in detail in the thesis.In order to enhance the dependability and reduce Electromagnetic Interference (EMI), Switching Power Supply must have protection circuit with complete performance and the ways and means that can reduce EML. All kinds of protection circuit and the produce mechanism of EMI is depicted, and the EMI Filter and EMI Absorber is introduced in the thesis.Test result of the Switching Power Supply prototype shows, the High-Frequency Switching Power Supply with Two-Transistor Flyback Converter and PWM-PFM control circuit can endure input voltage fluctuating on a large scale. It has high dependability, can apply extensively to abominable environment of power supply, such as the industry electric apparatus switch board, automatic elevator, etc., has certain advance and wide application prospect...