LAUSR

An active diode IC-based full-wave charge pump is presented. It interfaces to a vibration harvester designed for low acceleration non-periodic bridge vibrations. The charge pump’s unique architecture uses only two comparators to switch the charge pump’s eight stages. This architecture reduces power and allows for a novel passive diode switching technique that also enables a reduction in the turn-on voltage. This switching technique initially functions based only on the AC input without a DC supply. This architecture is used to enable cold start-up using the charge pump’s external $100~{\mu }\text{F}$ capacitors. These large capacitors create a stable power supply for start-up from one low voltage AC input based off of bridge vibrations that are random and infrequent. Its rectification circuitry is fabricated in 180 nm CMOS on a 1.2 mm² die. The circuit inputs, generated using a shaker table, are periodic sine-waves or non-periodic mechanical frequency up-converted vibration harvester outputs. Measurements show that the diode drop reduction allows cold start-up and boosting to >1.5 V with low power ( $\sim 8.5~{\mu }\text{W}$ ) non-periodic harvester outputs or 220 mV open circuit voltage periodic (~100 Hz) inputs. This IC demonstrates ~50% efficiency with an up-conversion-based harvester and ${\sim } 1~{\mu }\text{W}$ active power dissipation.