Abstract
IGBTs (Insulated Gate Bipolar Transistor) can be used for power DC-DC converters at higher voltages. A series connection is needed due to the blockingcapability limit of 6500V. The voltage must be shared among the IGBTs both dynamic when switching and blocking mode. A non-synchronized switching creates transient voltage that might damage the IGBT. The non-synchronized switching comes from different delays in the gate drivers and deviation in the IGBT parameters. This paper investigates in theory and practice a solutioncontains of clamp circuit, dynamic and static circuit. Turning on process of the stack of three IGBTs are in focus in a buck converter design. An operatingvoltage closer to the IGBT limit is used in order to press the system. For the simulations (Pspice) and experimental tests, fast IGBTs (1200V /30A IXYH40N120C3) are used to show the good dynamic of the chosen solution. The Lab tests also show that because of the deviation in parameters preadjustment of the gate signals is needed. The experimental tests have been carried out in different clamp voltage to finally have clamp voltage close tothe blocking voltage of the IGBTs and maximum 2A as output current. Examples of wave forms for voltages are given and discussed.
Highlights
Series connection of the IGBTs is used to avoid costly and complicated methods such as using transformer and multilevel topologies to increase the voltage rate in the converters [1]
Three 1.2kV silicon diodes are used as free-wheeling diodes in the converter structure
During switching on delay between the IGBTs, fastest IGBT turn on faster and two other IGBTs should share the voltage during this delay
Summary
Series connection of the IGBTs is used to avoid costly and complicated methods such as using transformer and multilevel topologies to increase the voltage rate in the converters [1]. The zener diode with at least surge reverse current equal to the maximum current which is passing through the gate resistance during switching process is needed. Three series IGBTs are used in a buck converter and tested in different level of voltages. They are tested by clamp voltage close to the blocking voltage of the IGBT. Maximum 2A current is in the output of the converter Both switching off and on process are the focus in this paper. Both simulation and experimental results are compared but stray inductances of the circuit and parasitic capacitances of the components have influence on the experiments. Both results of the simulations and the experiments are in the following
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