Load Current and Temperature Dependent Optimization of Active Gate Driving Vectors

A load current and temperature dependent optimization of the active gate driving waveforms is proposed to always solve the trade-off between the switching loss and the current/voltage overshoot of power transistors under load current and temperature variations. The switching loss and the current/voltage overshoot in turn-on/off state of IGBT using optimized gate driving vectors obtained by an automatic optimization are measured by using a 6-bit programmable digital gate driver IC across nine conditions including different load currents (20 A, 50 A, and 80 A) and temperatures (25 °C, 75 °C, and 125 °C). They are compared with those with conventional single-step gate driving waveforms using an object function as a function of the normalized loss and overshoot. When the optimized gate driving vector at a typical operation point of (50 A, 25 °C) is reused in other eight conditions, the object functions at eight conditions are better or worse than those of the conventional single-step driving. In contrast, when the gate driving vector is optimized at each condition, the object functions at all eight conditions are better than those of the conventional single-step driving in both turn-on and turn-off states, which clarifies the necessity of the proposed optimization. To implement the proposed optimization, a lookup table based active gate controller, which provides a preset optimum driving vector depending on the load current and the temperature, will be effective.