Output Current Enhancement of Capacitance Varying Charge Pumps by Electret-Embedded Capacitors and Non-Uniform Capacitance Configuration

A Capacitance Varying Charge Pump (CVCP), a charge pump consisting of variable capacitors and rectifiers, has shown to generate an output voltage exponentially dependent on the stage number. Despite this high voltage generating capability, its output current is limited due to the small capacitance, when the variable capacitors are formed by Micro-Elector-Mechanical-Systems (MEMS) technologies. To address this issue, we propose two novel CVCP configurations that improve the current supplying capability. The first one employs electret-embedded capacitors that increase the charge capacity. The second one adopts a non-uniform capacitance configuration. It is shown that the effective charge pump resistance can be minimized when the capacitances are configured in an exponentially decaying manner with respect to the stage number. Theoretical analyses are validated by simulations, and the results demonstrate a significant improvement in output current.