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Power management for a biotelemetry tag Sun, Jianzhong

Abstract

Power management for a biotelemetry tag implanted into the body of a sealion with the body temperature around 40°C is proposed in the aim for sustaining the tag's operation for at least three years without changing power sources under the constraint of a bounded energy budget and low physical profiles of all electronic components. Various primary battery and capacitor technologies and converter topologies are studied and compared. Two types of commercially available batteries, a silver oxide battery and a lithium manganese dioxide battery, are discharged at several constant current levels and at two different temperatures to establish the Peukert equation with temperature dependence for each type of battery technology, I[sup n] x t = K[sub 0] ( 1 + α T). It is concluded that a silver oxide battery is a better battery technology in that it has a more flat discharge profile and can deliver higher power and energy when they are normalized (with respect to nominal power and energy), than lithium manganese dioxide battery does. The supercapacitor in parallel with battery cells is incorporated into the input power source to enhance the power capability required by electronic components when the battery cells alone cannot supply such high power. The supercapacitor is adopted for its highest volumetric efficiency among all capacitor technologies and relatively low leakage current, which is measured at 40°C and confirmed to be well under 0.5 μ A. A converter topology is necessary to meet different voltage requirements from all electronic components. For maximum simplicity, a converter topology using two silver oxide batteries in series producing an input voltage of 3V can involve only one boost converter in the topology based upon the unique characteristics of a silver oxide battery from test results. A commercially available compact boost converter including the battery stacks in parallel with the supercapacitor as the input power source is tested under the voltage and current requirement of a power amplifier. The result shows that the chosen boost converter can meet the input power requirement of the power amplifier. It is concluded that under the constraint of current energy budget the proposed converter topology will operate for at most 6 years with the duration between adjacent activations for a low noise amplifier to be 46 minutes.

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