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Radiation Hardened SMPS, Power Converter and Integrated Circuit Design Controller

Mauro, M. ; Pires, C. ; Guilherme, J.G. ; Horta, N.

Radiation Hardened SMPS, Power Converter and Integrated Circuit Design Controller, Proc International Workshop on Analog and Mixed-Signal Integrated Circuits for Space Applications - AMICSA, Cascais, Portugal, Vol. 1, pp. 1 - 8, August, 2008.

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Abstract
The European Space Agency (ESA) is stimulating European industry to develop and manufacture radiation hardened power converters to be more independent from American suppliers. The dependence on American suppliers causes a considerable delay and increases the cost of the missions. There are several constraints imposed on smps intended to operate in space, namely, high efficiency, radiation tolerance, lowest cost possible, high reliability, low volume and weight, the ability to cope with large temperature variations, mechanical stress and the types of components that can be used. Size and weight can be reduced by increasing the operating frequency of the power converter, however switching losses increase and the efficiency is reduced. Achieving the lowest cost possible can be done by using commercial of the shelf (COTS) parts but radiation performance of some parts is hard to predict or completely unknown. Power converter topologies to be used have to comply with the requirement to provide isolation from the input to the output and no short circuit can ever be created in the supply rail due to upsets caused by radiation events. Several converter topologies which are suitable for space and radiation environments operation as the Forward, Flyback and the Insulated Boost have been analyzed taking into account the ease of control, number of discrete components and their cost. An appropriate circuit controller must be selected to achieve high performances. This proves to be a difficult task because space qualified controller circuits are generally old and outdated parts, which lacks in functionality compared to modern state-of-the-art controllers. To toggle with those challenges, a radiation resistant controller using a bulk CMOS process was develop, in order to achieve advanced control features while keeping the total cost of the converter low. To achieve good radiation resistance, different project and layout rules need to be applied, among others, memory elements redundancy and different transistor geometries as the enclosed mos transistor are mandatory to achieve stable and long term operation. This novel control integrated circuit implement current mode control with pulse frequency modulation, startup overshoot mitigation, adjustable operating frequency up to a maximum of 2MHz, shutdown and integrated power mos drive capable of driving loads up to 2nF.