Research On Hybrid Power Inductors Used In DC-DC Converters

To minimize the size of DC-DC power modules,the traditional approach is to use Si P packaging technology to stack inductors into a single package.However,the integration achieved by the Si P approach is still limited.To further increase the integration,the inductor must be monolithically integrated using an on-chip integrated So C.Conventional on-chip spiral inductors achieve a small inductance value,and on the order of a few n H,the required switching frequency of the DC-DC converter is very high,exceeding 100 MHz.At this stage,it is difficult for semiconductor technology to stably achieve such a high switching frequency,which hinders the practical application of the spiral inductor and hinders the miniaturization process of the DC-DC overall power module.The research topic of this thesis is the project of the National Natural Science Foundation of China,“The research of active power inductor integration in DC-DC converters”.Aiming at the trend of miniaturization and integration of switch-inductive DC-DC converters,the thesis will make on-chip high-integration hybrid power inductors as the core design conception.The hybrid power inductor includes the spiral inductor and the active inductor.The system for the large inductance value of the spiral inductor and power inductor will be designed.And the in-depth and meticulous theoretical research on the active power inductor would be conducted.Summarizing various problems in current integrated design and exploring new active power inductors for DC-DC converters,it replaces some of the traditional passive power output inductors to achieve hybrid power inductors,and finally meets the single-chip integration of DC-DC converter power devices.The main research contents and results of this thesis are as follows:1.Based on the traditional differential spiral inductor structure,a multilayer differential asymmetric spiral inductor architecture(MDSI)is proposed to increase the spiral inductance value to the order of hundred n H.The MDSI applied to the DC-DC converter is a 5-layer structure.A layout condition boundary condition calculation method for spiral inductors is designed for the MDSI architecture.By controlling the target parameters of the spiral inductor,the number of turns,the line width,the outer diameter and the spacing,the objective function and the set of sampling points of all constraints are defined to solve the optimal inductance value problem.Using this method to find the limits in width and the corresponding inner or outer diameter within a known and limited chip area is very efficient and feasible.The MDSI spiral inductor is introduced in detail to increase the inductance value,which can greatly reduce the occupied chip area and reduce the parasitic capacitance effect.This is because,1)Multi-layer multi-turn differential spiral structure is designed,each layer of metal wiring layer has a plurality of helical metal coils,and a differential coupling is formed between any two turns,and optimal coupling is achieved by controlling the pitch,thereby increasing the spiral inductance value to the order of hundred n H;2)by controlling the spacing between adjacent two metal coils in each of the metal wiring layers to be greater than zero and less than or equal to the line width of one metal coil and any adjacent three metal wiring layers,the intermediate layer has two states of contraction and expansion with respect to the upper and lower layers,and the chip area occupied by the spiral inductor of the order of n n H is controlled to be 220 μm × 220 μm or less,thereby realizing integration of the inductive So C for DC-DC converter;3)by controlling the sum of the staggered spacing between any two metal coils less than or equal to the sum of the widths of the T-coil metal coils,and the staggered spacing between any two adjacent metal coils being greater than zero and less than or equal to the line width of one metal coil,the optimal parasitic capacitance effect of an on-chip hundred n H spiral inductor is realized.The proposed MDSI architecture was simulated and verified using HFSS software and compared with traditional differential and non-differential structures,the simulation and comparison results show that the MDSI spiral inductor designed in this paper is applied to the DC-DC converter with the best performance,the required frequency is below 10 MHz and has good versatility.2.The topology of an active power inductor is designed,which uses active devices to simulate inductance characteristics.The circuit structure is simple and efficient.The chip area occupied depends only on the chip area occupied by the power tube in the structure.The quality factor characterization of active inductors is studied for active device characteristics,and a method to improve the quality factor of active inductors is given.The simulation results are verified by Spectre.The simulation results show that the structure can generate a wide range of inductance values,with a load current of more than 10 m A,which can improve the power of the active inductor and can be used as a string of MDSI spiral inductors./ Parallel auxiliary inductors are suitable for DC-DC converters.Although the work of existing active inductors has been studied in terms of signal processing and low power consumption,there has been little research on power boosting applied to DC-DC converters.The content of this paper seeks to take the first step to solve the problem of improving the power level of active inductors.3.It is the first to propose a hybrid power inductor for DC-DC converters to achieve on-chip integration.The MDSI spiral inductor and active inductor designed in this paper are applied to the simulation verification of DC-DC converter.The performance of on-chip spiral inductors and active inductors are determined by their geometry/layout,circuit topology and process parameters.There are many trade-offs between performance and its design parameters.This paper analyzes the competition relationship and trade-offs of inductor parameters in the application process,recommendations for structure,topology,material selection,and process design that spiral inductors and active inductors used in DC-DC converters should be followed,and a verification simulation was performed using a Buck-type DC-DC converter and a Buck-Boost DC-DC converter architecture.The simulation results verify the feasibility of the scheme.The MDSI spiral inductor layout and active inductor circuit topology designed in this paper will be verified by the Dongbu Hitek 0.18μM 1P6 M BCD process in the next research project of the National Natural Science Foundation of China.