Key Module Design Of Synchronous And Step-Down DC-DC Switching Power Supply

In modern society,people’s dependence on electronic products is far more than at any time in the past.With the rapid development of integrated circuit technology,the volume of electronic products is becoming smaller and smaller,and the power consumption is getting lower and lower,but the function is becoming more and more powerful.As one of the core components of various electronic products,the performance of DC-DC switching power supply chip has a decisive influence on the endurance time and life of electronic equipment.In order to have higher application value for electronic devices,the low power and high conversion rate design of DC-DC switching power chip has gradually become a hot topic in the field of integrated circuit design.The paper based on the standard 0.5μm BCD process,mainly studies the design,simulation and layout of the two key circuit modules of the bandgap reference and the one-shot timer in the synchronous and step-down DC-DC switching power supply.The main contents of this paper are as follows:1.A brief description of the development of switching power supply and discuss the development trend of switching power supply in future.2.The basic principle of Synchronous Buck DC-DC switching power supply system is described.3.The system architecture of valley value current control is introduced,including the working principle of valley value control mode,synchronous rectification technology,selection of peripheral devices,and the advantages of constant conduction time valley current control are summarized.4.The design and Simulation of the bandgap reference circuit proposed in this paper,including the pre-modulation part and the core part of the bandgap reference,are described in detail.The output voltage of the bandgap reference not only has a low temperature coefficient,but also can work with a larger power supply voltage range and has a good linear adjustment rate.This is mainly due to the use of the pre-modulated circuit structure instead of the traditional starting circuit and two stage amplification with high gain in the core circuit.Under the TT process angle,the simulation results show that the temperature coefficient is 14.36ppm/C at the temperature range of-40 to 80 C.In the range of 3to 10V supply voltage,the output voltage of the output terminal is only 30μV/V,and the linear adjustment rate is 4.3μV/V.The PSRR of the circuit is 102dB,and its power consumption is 300μW at 3.3V typical working voltage.5.The design and simulation process of the one-shot timer is presented in detail.The design of Synchronous Buck DC-DC switching power supply is based on constant conduction time valley current control mode.The reason why this circuit control mode is adopted is that the mode has the characteristics of high conversion efficiency and stable working in high frequency environment.One-shot timer is the key circuit module used to generate fixed lead time.At the same time,in order to maintain the stability of the output voltage of the switching power supply,the switching tube frequency in the valley value current control mode should have an upper limit,and the upper limit is determined by the minimum T_ON of one-shot timer.The minimum T_ON in the circuit designed in this paper is about 40ns.6.The factors that need to be considered in the layout design,such as matching consideration,antijamming and parasitism consideration and reliability consideration,are described,and the designed bandgap reference and one-shot timer layout are presented.7.Summarize the shortcomings of the paper and the results of module design.