Development and power device reliability assessment of resonant pulsed power converters for RF applications

This paper considers the calorimetric measurements of losses and the semiconductor thermal cycling monitoring of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10%, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms-2 ms) of RF tubes when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is to monitor semiconductor losses of the IGBT modules through calorimetry and the device temperature using high speed thermal imaging, during the pulse, to identify the limitations and reliability of the modulator technology proposed. The paper provides an overview of the technology and design of the prototype test rig studied. Experimental results, showing semiconductor losses obtained through calorimetry and high quality chip thermal images are provided to validate the effectiveness of the proposed approaches.