A novel RCD level shifter for elimination of spurious turn-on in the bridge-leg configuration

With the increase in the switching speed and power level in the bridge-leg configuration, the spurious triggering pulse in the synchronous switch is prone to exceed the threshold voltage and cause spurious turn-on. Eliminating the spurious turn-on phenomenon plays an important role in preventing excessive switching loss, self-oscillation, and shoot-through in the bridge-leg configuration. A novel resistor-capacitor-diode (RCD) level shifter is proposed to generate a negative gate voltage so that the spurious triggering pulse can be shifted below the threshold voltage, and thereby, the spurious turn-on can be avoided. The merits of the devised auxiliary circuit lie not merely in that it consists only of passive components and can easily be co-packaged with the existing gate driver, but also in that the negative voltage level is tunable and independent of the duty cycle of the converter. The effectiveness of this circuit has been verified by the experimental results. It is shown that when the spurious turn-on occurs in a bridge-leg configuration, the adoption of the proposed circuit can eliminate the spurious turn-on and reduce the turn-off switching loss by more than 40%.