Research And Design Of Multi-rate Charge Pump Circuit With Fast Transient Response

In recent years,due to the rapid development of micro-electronic intelligent terminal,the power management chip has higher requirements and performance requirements.Charge pump has become a hot research object due to its advantages of no inductance,easy integration,low electromagnetic interference and simple peripheral circuit,and is developing towards small size,high efficiency,low power consumption and fast transient response.At present,the research on improving the fast transient response of charge pump mainly focuses on frequency control and phase control,but only using these two control methods has the problem that the load range of charge pump can be adjusted is very limited.To solve this problem,based on the frequency control mode of VCO to improve the fast transient response of charge pump,the following work has been done.First of all,a charge pump scheme with 16 conversion ratios is proposed with conversion ratios of 1/16,1/8,3/16…to 1,and the output voltage of the charge pump is adjusted by rate conversion when the load changes greatly.Based on the charge pump unit with conversion ratio of 1/2 and 1,the charge pump adopts a four-stage cascade mode.When the output voltage undershoot or overshoot caused by load change is detected beyond the adjustable range of frequency control mode,the conversion ratio of the charge pump increases by 1/16 or decreases by 1/16 in turn until the output voltage of the charge pump falls within the adjustable range of the frequency control module,and then the output voltage can be stabilized near the reference voltage under the action of the frequency control module.This method increases the adjustable load range of the charge pump.Secondly,when the load of the charge pump changes from light load to heavy load,the phase control module works to change the clock signal of the charge pump from 8 phase to 4phase,so as to increase the output voltage ripple of the charge pump,and the duty cycle changes from 50% to 62.5%,so as to reduce the fast switching loss.This method further accelerates the fast transient response of charge pump load from light load to heavy load.After the charge pump has no load change and the output voltage is stable,the clock phase works in the mode of 8-phase and 50% duty cycle.Finally,after the theoretical analysis and design of the key sub-modules are completed,the fast transient response simulation of the charge pump circuit with different control modules and different load changes is carried out using Cadence software based on TSMC-0.18 um process.The simulation results show that the load changes from 0.5m A to 240 m A,the conversion ratio of charge pump increases by 1/8,and the transient recovery time is 180.2ns.When the load changes from240 m A to0.5m A,the conversion ratio of the point-load pump is reduced by1/8,and the transient recovery time is161.1ns.The output voltage ripple of the charge pump is less than 1m V under light load and less than 10 m V under heavy load.The peak conversion efficiency of the charge pump can reach 89.9%.The simulation results effectively verify that the addition of the charge pump rate conversion module increases the adjustable load range of the charge pump,and the adjustment of the clock duty cycle by the phase control module accelerates the rapid transient response of the charge pump.