This paper presents a switched-capacitor stepdown DC-DC converter using switch-width modulation (SWM) and digital capacitance modulation (DCM), to maintain the converter efficiency for various load currents. The proposed SWM technique dynamically selects the proper switch sizes to efficiently balance the switching and conductance losses, and hence, maintain the efficiency when the load current varies. This converter is simulated in a 180 nm CMOS technology. The peak of efficiency for Vin = 1.8 V and Vout = 0.85 V is 80%, while the maximum load current is 1.5 mA. The switching frequency is constant for different load currents and is equal to 10MHz. The output ripple is smaller than 35mV.

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