An Equivalent Circuit Model for Vertical Comb Drive MEMS Optical Scanner Controlled by Pulse Width Modulation

Abstract

An equivalent circuit model for the resonant-type vertical comb-driven optical MEMS (micro electro mechanical system) scanner has been developed based on the simple extension of the parallel-plate model. Both the electrostatic torque and the induction charge models are interpreted by using the equation-defined nonlinear dependent current source on the electrical circuit simulator platform. A systematic procedure has been investigated to fit the analytical model with the experimental results by using fitting parameters including the damping coefficient, the suspension width, and the comb gap. The developed simulation model has been used to verify a new control scheme to tune the scanner's oscillation amplitude in resonance by means of the pulse-width modulation of voltage at a given pulse height; the result indicates the effective use of digital electronics for the comb-driven optical scanner.