Static gate control for charge-transfer switches in DC-DC conversion

A gate controller was designed to improve the operation of switches in the static charge-transfer switch (CTS) converters. In this study, the gate controller was called as voltage level controller (VC) which would eliminate the reverse charge sharing effect in the static CTS. The proposed VC circuit operates with the higher voltage at the later stage to enhance the pumped voltage in the Dickson circuit without losing charges in the auxiliary path. Since the VC needs little current to control the transistor gates, compact layout with minimal sizes for the VC circuit can be achieved without consuming too much area in the chip. The function of the VC was verified both by HSPICE and chip testing. In the simulation, a CTS converter of 4 pumping stages would generate an output near 8 V with the input of 1.5 V. The generated power was estimated as 5 mW for a load of 10 KΩ. Based on the 0.35-μm CMOS technology of TSMC, a chip of 125*160 μ² was obtained for testing. Due to the voltage tolerance of the transistors, only 3 stages of pumping worked correctly for the 1.5-V input and the highest output in the measurement was 5.4 V.