![]() On and off drive voltagesĪn initial consideration is to set the on and off-state gate voltages. We will now consider how DC-DC converters can provide optimum power rails for these ‘floating’ drive circuits using a typical IGBT from Infineon as an example, type FZ400R12KE4. In many instances, the bridge circuit requires safety agency-rated isolation from the control circuitry and therefore the barrier must be robust and show no significant degradation over the design life time due to partial discharge effects. Additional requirements are that the drive circuit should be immune to the high ‘dV/dt’ of the switch node and have a very low coupling capacitance. ![]() Bridge circuits include IGBTs whose emitters are switching nodes at high voltage and high frequency so the gate drive PWM signal and associated drive power rails, which use the emitter as a reference, have to be ‘floating’ with respect to system ground, so called ‘high side’ drives. When IGBTs are paralleled, the gate drive power required is higher still.Īt high power, inverters or converters typically use ‘bridge’ configurations to generate line-frequency AC or to provide bi-directional PWM drive to motors, transformers or other loads. Although this capacitance has simply to be charged and discharged to turn the IGBT on and off, the circulating current to do so causes significant power dissipation in voltage drops in the gate driver circuit and within the IGBT. IGBTs now find their natural home in applications at high power using devices with effective gate capacitances measured in hundreds of nanofarads. When the Insulated Gate Bipolar Transistor (IGBT) was invented by Professor Jayant Baliga in 1980, it was seen as an ideal combination of the low on-state saturation voltage of a bipolar transistor and ease of gate drive of a MOSFET. PRODUCT FOCUS Powering IGBT Gate Drives with DC-DC Converters
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