“Active Gate Switching Control of IGBT to Improve Efficiency in High Power Density Converters”
Thesis submitted in partial fulfilment of the requirement for the PhD degree issued by the Universitat Politècnica de Catalunya, in its Electronic Engineering Program
by Hamidreza Ghorbani
Director: Dr. Prof. Jose Luis Romeral Martinez
Co-Director: Dr. Eng. Vicent Sala
Insulated gate bipolar transistor (IGBT) power semiconductors are widely employed in industrial applications. This power switch capability in high voltage blocking and high current-carrying has expanded its use in power electronics. However, efficiency improvement and reducing the size of products is one of main tasks of engineers in recent years. In order to achieve high-density power converters, attentions are focused on the use of fast IGBTs. Therefore, for achieving this desire the trend is designing more effective IGBT gate drivers.
In gate drive (GD) controlling, the main issue is maintaining transient behavior of the MOS-channel switch in well condition; when it switches fast to reduce losses. It is well known that fast switching has a direct effect on the efficiency improvement; meanwhile, it is the major reason of appearing electromagnetic interference (EMI) problems in switched-mode power converters.
Nowadays the most expectant of an active gate driver (AGD) is actively adjusting the switching transient through simple circuit implementation. Usually its performance is compared with the conventional gate driver (CGD) with fixed driving profile. As a result a proposed AGD has the capability of increasing the switching speed while minimizing the switching stress. Different novel active gate drivers (as feed-forward and closed-loop topologies) have been designed and analysed in this study. To improve the exist trade-off between switching losses and EMI problem, all effective factors on this trade-off are evaluated and considered in proposed solutions. Theoretical developments include proposed controlling methods and simulated efficiency of IGBTs switching control. The efficiency improvement has been pursued with considering EMI study in the proposed active gate controller. Experimental tests have been conducted to verify the design and validate the results. Beside technical aspects, cost study has also considered in the closed-loop GD. The proposed gate drivers are simple enough to allow its use in real industrial applications.
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