Design And Implementation Of High-efficiency Switched Capacitor DC-DC For Light Load

For heavy duty-cycle sensor network node chips,the Always-on Block?AoB?will use low voltage operation technology to achieve lower sleep power consumption.Switched-capacitor Direct Current Converter?DC-DC?has low cost?high integration characteristics,and can obtain higher conversion efficiency under low voltage and light load condition;comparing to Low Dropout Regulator?LDO?and Inductor voltage converter?Buck?,the Switched-capacitor DC-DC is more suitable for AoB circuits.In order to further improve the power consumption of AoB circuits,it is necessary to study switched capacitor DC-DC with high conversion efficiency under light load condition.The scheme of switched capacitor DC-DC based on self-powered and stepped-pulse modulation mechanism is systematically expounded in this paper.In order to reduce the loss of the control circuits,a self-powered scheme is proposed.The domain of switched capacitor DC-DC circuit is divided into a V_DD domain and a V_OUT domain,which corresponding to a startup operation mode and a load adaptive adjustment operation mode respectively.The output voltage V_OUT of the switched capacitor topology is used as the supply voltage of the load adaptive regulation circuits,the low voltage and self-powered operation can greatly improve the conversion efficiency at light load condition.In order to overcome the shortcomings of the traditional clock frequency regulation scheme that can not achieve low power consumption and regulate continuously simultaneously,a stepped pulse modulation scheme is proposed.When the load current is at steady state,a several clock pulses are created intermittently to maintain the output voltage stable;when the load current changes,the number of clock pulses is adjusted according to the load level to response the load transient changes.At lighter load level,this intermittent regulation is beneficial to improve conversion efficiency.The circuit and layout design of the switched capacitor DC-DC are completed on the GF0.13?m process,the input voltage is 3V,the output voltage is 0.7V and the circuit area is0.14mm².The simulation results show that the output ripple voltage is less than 7mV in the load range of 200nA¹?A;the conversion efficiency is 62%and 49%under the load of 1?A and 200nA respectively,reaching the design goals.