Design Of Single-Inductor Multiple-Output Switching Regulator

With the development of commercial portable electronic devices,small size,light weight and long use time have become urgent requirements of consumers.Single-inductor multi-output（SIMO,single-inductor multi-output）DC-DC converter uses one inductor to achieve multiple regulated outputs,which reduces the PCB area and reduces production costs,which has attracted widespread attention and research in the business and academic circles.This paper summarizes the design goals of SIMO inverters,including reducing crossregulation,increasing output power,improving work efficiency,and reducing output ripple.Compared with the traditional single-output structure,the single-inductance multi-output converter has multiple control loops,which increases the complexity and difficulty of analysis.Here,the stability analysis of the step-down SIMO converter based on charge balance control is carried out,the frequency domain model is established and the system compensation is guided,and the time domain model is established to verify the function and performance of the controller.Various structures of buck-boost are proposed.Characteristics and bipolar output topology,carry out stability analysis of one of them.The negative output channel deduced by the model has a stability problem.This paper proposes duty-cycle-constrained comparator control,and the distribution algorithm optimizes the transient response of the system and improves the crosstalk suppression performance.This paper uses GF 1P6 M 0.18μm CMOS technology for circuit design and simulation,including:（1）Single inductor multi-output step-down DC converter based on charge control,input voltage 3.6-4.5V,tri-output 1.1V,1.8 V and 2.8V,the maximum load current is 1A,the switching frequency is 1MHz,CR is 0.069 mV/mA,the maximum output power is 4W,and the peak efficiency is 91.6%;（2）Bipolar SIDO based on charge control: input voltage V_g=3.3V,flexible buck-boost output V_o1=（0.8-5.5）V,negative output V_o2=-4.8V,switching frequency1 MHz,peak efficiency is 94.7%,the maximum output power is 6.5W,and CR is 0.235 mV/mA;（3）auto buck-boost SIMO based on duty-cycle-constrained comparator control,input Voltage V_g= 3V,the four output voltages are V_o1 = 1.8V,V_o2 = 2.5V,V_o3 = 3.3V,V_o4 = 5V,the peak efficiency is 89.5%,the maximum power is 5W,which is 0.038 mV/mA.Through simulation,the feasibility of the optimization strategy proposed in this paper is verified;the problems pointed out by the stability analysis are verified,and the necessity of the stability analysis in the SIMO design process is explained.