Design Of Step-up Charge Pump DC-DC Converter

With the rapid increase in the demand for portable electronic products,power management chips have gradually developed in the direction of low power consumption,high efficiency,small size,and intelligence.The charge pump circuit is widely used because of its simple peripheral circuits,low EMI,low noise,and small chip area.The charge pump uses the energy storage element-capacitor to “carry” charge and “pump” the output voltage to a high or negative potential.It can be used in lithium-ion battery drive circuits,local power supplies,and power supplies for display LED backlights.This paper proposes a feasible solution to the problems of large power consumption and low efficiency of the charge pump circuit at the current stage,and verifies it through modules and overall simulation.This article uses a simple depletion reference and bias to reduce quiescent current.PFM modulation mode is used to stabilize the output voltage and reduce the dynamic loss of the switch.The PMOS switching transistor uses a dynamic substrate selection circuit to ensure that the substrate potential is always at the highest,which suppresses the parasitic triode effect and reduces the substrate leakage current.The non-overlapping clock controls the turning on and off of the switching transistor to avoid causing a path from power to output or to ground.The chip is reserved for off-chip trimming,and different output voltages can be selected according to needs.The chip also has soft start and enable functions.This article uses CSMC 0.5 ?m CMOS technology to simulate the designed charge pump circuit based on the Cadence Spectre simulation platform.The circuit simulation results prove that the design specifications meet the requirements,and the layout design work is completed on this basis.At the end of this article,a test analysis was performed on the chip.The test results show that when the load current is 10 m A,the output voltage range is 4.9V ? 5.1V,representing that the output voltage accuracy is ± 2%.The circuit static current consumption is 35?A,and the maximum operating frequency is 1MHz.Also,the maximum output current is 25 m A,and the voltage conversion efficiency can reach more than 90%,which means the design index of low power consumption and high efficiency is achieved.