Power supply topologies for biphasic stimulation in inductively powered implants

Biphasic stimulation is commonly used for electrical stimulation of tissue in many implants. A dual voltage scheme is often used for the operation of the stimulus circuitry. Due to the advantages of wireless power transmission, an inductive link is used to recover the transmitted power and generate these voltages. This paper identifies the problem of additional power dissipation in the implant when the traditional rectifier topology with one diode is used. A dual diode topology is proposed which reduces the power dissipated in the implant by half. A detailed analysis for both topologies is done through derivation of expressions for the power losses on the primary and secondary coils. A comparison of single diode and dual diode topologies is presented under different conditions and inferences are drawn that can be used as design guidelines.