Step-up versus step-down DC/DC converters for RF-powered systems

We compare two designs for dual power supply RF-powered systems such as implantable stimulators and contactless smartcards. Specifically, we compare a traditional design using a step-up DC/DC converter versus a design that uses a step-down converter. We analyze which system can operate from a lower input source voltage, and show how non-idealities in DC/DC converters affect the relative merits of the step-up versus step-down designs. We demonstrate that the step-down architecture can increase maximum operable link distance and power available to the load in systems with high source resistances or inefficient DC/DC converters. Through simulation and experiment, we verify that source resistances greater than 250kΩ are possible in RF-powered systems, and that step-down converters can improve available load power by 100%.