Modelling and performance evaluation of a MEMS dc/dc converter

Abstract

Microelectromechanical (MEMS) structures for dc voltage conversion on a silicon substrate are presented. The boost conversion replaces the normal inductor for energy storage in a magnetic field by energy storage in a mechanical system. The mechanical design of the MEMS voltage converter is presented with good agreement between analytical and finite-element modelling (FEM) methods. A discrete analytical model for the converter output voltage at each MEMS actuation cycle is developed and results are compared with electrical device simulation in the PSpice environment. The model takes account of parasitic components in the system implementation, in particular in the blocking diode/switch. Typical MEMS and diode capacitance values are investigated and the voltage gain in these conditions is found to be negligible. The use of a MEMS switch in the blocking diode role can minimize these problems at the cost of more expensive control circuitry and increased power consumption. A suitable application in an RF receiver with intermittent electrostatic actuation of an array of MEMS resonators requiring high transient voltages is described. The efficiency of operation is less than 1.4% but total power consumption is around 1 mJ and this may be acceptable in this intermittent mode of operation.