A Thermal Energy Harvesting Power Supply With an Internal Startup Circuit for Pacemakers

A complete thermal energy harvesting power supply for implantable pacemakers is presented in this paper. The designed power supply includes an internal startup and does not need any external reference voltage. The startup circuit includes a prestartup charge pump (CP) and a startup boost converter. The prestartup CP consists of an ultralow-voltage oscillator followed by a high-efficiency modified Dickson. Forward body biasing is used to effectively reduce the MOS threshold voltages as well as the supply voltage in oscillator and CP. The steady-state circuit includes a high-efficiency boost converter that utilizes a modified maximum powerpoint tracking scheme. The system is designed so that no failure occurs under overload conditions. Using this approach, a thermal energy harvesting power supply has been designed using 180-nm CMOS technology. According to HSPICE simulation results, the circuit operates from input voltages as low as 40 mV provided from a thermoelectric generator and generates output voltages up to 3 V. A maximum power of 130 μW can be obtained from the output of the boost converter, which means that its efficiency is 60%. A minimum voltage of 60 mV and a maximum time of 400 ms are needed for the circuit to start up.