Topology Transformation And Circuit Realization Of Hybrid DC-DC Converter With High-conversion Ratio

This article focuses on application scenarios based on secondary power high transformation ratio conversion,such as data center platforms,automotive electronics and other intelligent industrial scenarios.The topological conversion and circuit realization of the high-conversion-ratio hybrid DC-DC converter are analyzed and studied.Firstly,the first stage of the 48-V two-stage scheme is discussed,and the three-level Ga N half-bridge LLC architecture is proposed as the first stage scheme,which can improve the overall efficiency of the two-stage system under medium and light load,reduce the volume of the matrix transformer,and improve the power density.Secondly,the challenges faced by the three-level Ga N half-bridge drive circuit are analyzed.The normal operation of the flying span capacitor is ensured by precharging,periodic sampling and adaptive adjustment of the voltage of the flying span capacitor.Ensure the reliability of off-chip low-power Ga N devices when the flying span capacitor is powered on quickly.The capacitor can adjust itself after misoperation has occurred.The dualswitch bootstrap charging scheme completes the low-voltage differential charging of the three high-side bootstrap capacitors,and the minimum bootstrap capacitor voltage is 3.5V.The closed-loop control avoids charging in the dead-zone negative pressure stage and protects the reliability of gate-source voltage of Ga N devices.Finally,the key functions of the chip were verified by the way of layout and post-simulation,and the test scheme was developed and the function verification was carried out.In the test,some basic functions of the chip were realized and verified.Based on the design experience of three-level Ga N driver chip,this thesis studies the topology and control circuit of 48V-1V one-level conversion and closed-loop control.A topology of Switch Capacitors(SCDS)based on switch capacitors(DSDS)is proposed,which can achieve automatic voltage stabilization of capacitors and self-current equalization of inductors during the same opening time.In combination with the topology,the COT control mode of superposed two-phase inductance current ripple is proposed in this thesis,which can not only improve the loop bandwidth to improve the transient response speed,but also ensure that the double phase has the same opening time.The equivalent switching frequency is 2MHz,the maximum output current is 5A,the output drop voltage is 39 m V at 48V-1V rotation ratio under the load switching condition of4A/20 ns,and the recovery time of 1% accuracy is 6.5μs.The overshoot voltage is 144 m V,and the 1% precision recovery time is 15μs.In terms of bootstrap circuit,this thesis adds two extra off-chip capacitors as auxiliary charging branches,and the saturation of highside bootstrap capacitor is 4.4V at the lowest level.In terms of drive control,ZCS of highside devices can be turned off and ZVS of some devices can be turned on by controlling the opening sequence of different power devices,thus reducing the circuit drive loss.