5. Conclusions

respectively. At a higher output current, the effective voltage across the primary inductor is lower; due to the increased voltage drop across the parasitic resistance in the inductor, resulting in a lower induced voltage in the secondary winding. As described for the 100 kΩ load above, if this gate voltage on the JFET, which is equal to the voltage induced in the secondary winding does not reach the pinch off potential of the device, the converter will not oscillate. Hence for the higher output current (10 kΩ load) the converter is capable of self-starting operation at lower

The converter overall efficiency as a function of temperature is shown by the data in Figure 15. As can be seen from the data, the efficiency of the converter is approximately twice that of the

temperatures in comparison to the case with a 100 kΩ load resistor.

16 Advanced Electronic Circuits - Principles, Architectures and Applications on Emerging Technologies

Figure 14. Output voltage as a function of temperature.

Figure 15. Efficiency of boost converter as a function of temperature.

A novel self-starting converter technology has been described, which is suitable for powering wireless sensor nodes by means of energy harvesting from a thermal gradient. The converter was constructed from silicon carbide devices and proprietary high temperature passives to enable deployment in hostile environments, such as those found in aerospace, oil and gas and nuclear applications. The self-oscillating nature of the circuit along with high temperature capability result in reduced component count and hence a more reliable approach for powering SiC based WSNs for hostile environments. The self-oscillating nature of the circuit along with high temperature capability result in reduced component count and hence a more reliable approach for powering SiC based WSNs for hostile environments. The operation principle of the self-starting converter was detailed for two configurations which reflect low and high output current. The effect of input voltage and primary inductance on the converter operation and switching frequency was correlated with the characteristics of the components used in the circuit manufacture and the operating conditions for the circuit. Experimental measurements on a converter showed that whilst the performance of the circuit is influenced by the ambient temperature, it is possible to boost the voltage from a thermoelectric generator to a level that is suitable for the operation of high temperature circuits.
