A High Efficiency Orthogonally Switching Passive Charge Pump Rectifier for Energy Harvesters

The design and analytical modeling of a high efficiency energy harvester comprising a passive voltage-boosting network (VBN) and a switching charge pump rectifier (CPR) is presented in this paper. To improve the power conversion efficiency (PCE), the VBN increases the voltage at the input of the CPR and provides control signals for switching. Unlike traditional Schottky and diode-connected MOS transistor rectifiers, the proposed orthogonally switching CPR (OS-CPR) comprises MOS transistors as voltage-controlled switches. Analytical models for the OS-CPR are developed and presented. Circuit-level optimization techniques are employed to reduce conduction and switching losses. Simulated in a 90 nm standard CMOS technology (IBM 9RF), a 5-stage 915 MHz OS-CPR achieves a dc voltage of 1.35 V and a PCE of 11.9% with a 1 MΩ load at -18.2 dBm available input power (P_S,AV). To show technology scalability of the design, the OS-CPR is also validated using AMS 0.18 μm high-voltage (HV) CMOS technology. When benchmarked with traditional rectifiers, the OS-CPR (under similar conditions) achieves a higher PCE and a higher output dc voltage. The OS-CPR is easily scalable to operate over multiple sub-GHz ISM frequency bands.