The series connection of IGBTs with active voltage sharing

This paper presents the reasons that make series operation of insulated gate bipolar transistors (IGBT's) attractive and challenging and reviews the methods that may be used. Then, a new approach, which uses the IGBT's gate-controlled active regime in place of large voltage-sharing snubbers, is proposed. Analytical and simulation techniques are used to study the performance and conditions for stability given. It is concluded that when making each IGBT voltage follow a reference input, with closed-loop voltage control, the IGBT's are able to share the transient turn-off voltage without turn-off snubbers. This technique may lead to more compact and efficient high-voltage-power modules. Index Terms - Active voltage control, gate drives, high-voltage switching, IGBT, series connection.