Extreme temperature switch mode power supply based on vee-square control using silicon carbide, silicon on sapphire, hybrid technology

Scope and Method of Study:Switch mode power supplies, commonly known as SMPS are basic building blocks of the electronic systems. SMPS performs power regulation by accepting a raw input voltage and transforming it to required voltage at output with desired characteristics. Electronic systems used in applications such as deep well oil drilling, geothermal wells and deep space explorations is expected to operate under extremely harsh conditions like elevated temperature, high pressure and radiation prone environments. To support the onboard electronics in these applications, SMPS capable of operating at extreme temperatures are of high interest.This research work deals with the design and development of a switch mode power supply capable of operating over the temperature range of 300 degree centigrade (C). Silicon carbide field effect transistors are used as power devices in the design to tolerate these extreme high ambient temperatures without compromising power handling capability. The simplest yet robust vee square control architecture is adopted for control mechanism. The control electronics are implemented as an integrated circuit in 0.5 mm silicon on sapphire process. The supporting components like high temperature tolerant inductors and capacitors are identified by evaluating various samples at elevated temperature.Findings and Conclusions: This is the first demonstration of SMPS capable of operating at 275 degrees C as a standalone component. Also for the first time, a gate drive mechanism based on planar transformer architecture is studied and presented for high temperature operation. A low cost packaging technique suited for harsh environment operation is proposed based on gold on aluminum nitride thin film technology. The basic analog building blocks of the system, such as comparator, voltage reference and rail-to-rail amplifiers are made available in discrete packages for use at temperatures above 275 degrees C. A SMPS prototype on a 1.8 square inches substrate is developed and tested. Test results indicate that the system is capable of operating continuously at 275 degrees C for extended period of time, providing the desired performance characteristics