Fully Integrated Isolated DC-DC Power Supply Based On Full Bridge Topology

Since the 21st century,people have higher and higher requirements for the stabil-ity,safety,portability,and endurance of electronic products,so the power management chip has played an increasingly important role in the electronic technology field.Isolated power supply can realize power transmission in the case of electrical isolation,and has the characteristics of good interference immunity and user safety.With the development of isolation technology,the on-chip transformer makes it possible to realize the full inte-grated isolated power supply,which further improves the integration and reliability of the isolated power supply chip.Firstly,the thesis briefly introduces the isolation technology and isolated DC-DC converter,and describes the development status and trend of the isolated power supply.Then,based on the magnetic coupling isolation technology and the full bridge topology,it puts forward the fully integrated isolation power supply scheme designed in this thesis.The full-bridge inverter,full-bridge rectifier,soft switching and voltage mode pulse width modulation control are described in detail.The design and simulation verification of the power stage and the key blocks in the control stage,such as bias circuit,band-gap reference circuit and under-voltage lockout circuit is based on a 0.25μm 5V BCD process.This thesis is mainly based on the research and design of a fully integrated isolated DC-DC converter using the on-chip transformer and full-bridge topology.In terms of circuit topology,compared with the traditional resonant fully integrated isolation DC-DC converter,there is no resonant boost structure at the transmission chip.The converter relies on the transformer to boost the voltage,so the whole circuit does not require high-voltage devices,and only requires an off-chip capacitor.In terms of the control scheme,based on phase shift technology,the voltage mode pulse width modulation method and the frequency switching technology are used to control the power supply in this thesis to achieve stable output voltage and improve the transmission efficiency under light load.The post-layout simulation results show that the isolated power supply can work with an input voltage of 3.3～5V and an output voltage of 3.3V or 5V.The maximum output power is 0.75W,the maximum output efficiency is 43%,the voltage regulation is 2m V/V,and the load regulation is 0.125V/A.When the input voltage has a step change of-0.5V and+1V,the undershoot and overshoot of the output voltage are-18m V and+32m V,respectively,and the recovery time is less than 6μs.When the load current has a step change of±80m A,the undershoot and overshoot of output voltage are-40m V and+44m V,respectively,and the recovery time is less than 5μs.The output ripple is 14m V under 50m A load.The size of the transmitter chip is 2.23mm~2,and the size of the receiver chip is 1.9mm~2.