A Thermal Energy Harvesting Power Supply with an Internal Start up Circuit

Existing System:

The method to power up an implantable pacemaker is harvesting thermal energy. Harvesting ambient thermal energy using thermoelectric generators (TEGs) is a convenient means of supplying power to implantable sensors, especially pacemakers. Micro-TEG is scalable and reliable and does not require any moving parts like vibration energy transducers. As a consequence, it is very appealing in microscale energy harvesting systems, such as human body-powered biomedical devices. Recently, on-chip TE modules have been used to harvest electrical energy from waste heat. TEGs (also called Seebeck generators) are devices that convert heat (temperature differences) directly into electrical energy, using a phenomenon called the Seebeck effect (a form of TE effect). A voltage source in series with an internal resistance is a representative of TEGs. The open-circuit output voltage of the TEG is proportional to the temperature gradient. When implanting a TEG, the best place should be as close as possible to the superficial skin, where a maximum temperature difference between the two junctions of the TEG could be established. This would guarantee a good output of the TEG.

Disadvantages:

• Power consumption is high

Proposed System:

In the proposed system we are implementing the TE energy harvesting system architecture with low dropout regulator. An ultralow-voltage low-power oscillator generates the required clock phases for a CP system. A high-efficiency modified Dickson CP is used to increase the input voltage to the extent that is needed for the whole circuit to operate successfully. The output voltage of the TEG is applied to the input of CP. Consequently, CP begins to charge a small internal capacitor (CPST) placed at its output and the capacitor voltage (VPST) begins to rise. When VPST reached a predefined value, the output of the comparator 1 (VCMP1) sets. This enables the startup boost converter (SUBC) to work. The SUBC provides the required clock phases for the steady-state boost converter (SSBC), while the SSBC output voltage (VOUT) does not reach a preset value. When this is achieved, the output of the comparator 2 (VCMP2) sets and the normal operation of the system begins. In this mode, the SSBC itself generates its clock phases. A multiplexer is used to select the source of the required phases for the SSBC based on the VCMP2, whether from SUBC (VPH,ST), or a self-generated one (VPH,SS). In normal peration, the SSBC no longer requires the prestart up CP and SUBC, so it can continue to work on its own. It is designed so that VOUT becomes a regulated output voltage with a low voltage ripple. If, for any reason, VOUT falls out of the range of the output voltage, immediately, the SUBC becomes active and charges the output voltage until it comes within the range. This operation takes time no more than 400 ms. Therefore, the system offers high reliability.

Advantages:

1. Reduce the power level

Software implementation:

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