Wideband dynamic voltage sensing mechanism for EH systems

In Energy Harvesting (EH) scenarios, the `survival zone' pertains to the state of power supply with insufficient energy to provide a nominal and stable Vdd. In this situation the system Vdd tends to be low and to vary over a wide band. Benefits can be had if the system can already function to some degree under survival zone conditions. Such functionalities may include providing control to improve the efficiency of power processing units and starting the computation load for light but crucial survival-related tasks. Knowledge of the Vdd is often indispensable for running these types of survival zone functionalities. A novel low-power voltage sensing scheme for EH based electronic systems is proposed to function in the survival zone to provide this vital Vdd information. The method is derived by combining voltage controlled delays and simple circuits to implement time comparison. This paper describes the design, implementation and analysis of this sensing subsystem, which itself draws power from the variable and low Vdd which it is sensing.