With increasing voltage ratings, insulated gate bipolar transistors (IGBT) are being used in power converter and inverter applications. such as motor drives and uninterruptible power supplies. The operating power-frequency bounds of any power semiconductor device can be extended and EMI decreased, by the use of snubbers. With device users wanting to extend the power-frequency bounds of IGBTs, the use of an inductive turn-on snubber is becoming viable. Since the use of a turn-on snubber with the IGBT would only be considered at high powers, significant snubber energy exist and recovery circuits are viable. In this paper, three turn-on snubber energy recovery circuits for IGBT power inverters are presented. Each configuration incorporates a soft-clamping circuit to limit switch over-shoot voltage at turn-off. The snubber energy is passively recovered into the DC supply through a high frequency transformer, and the transformer core flux is reset automatically. The operation process and circuit equations are given for each energy recvery circuit and can be used for practical inverter snubber optimal design. The presented circuits are suitable for use in high power IGBT inverters.
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