Digital Control for Voltage Balancing under Switching Operations of Series Connection SiC-MOSFETs

Voltage balancing control based on gate signal delay in series connection of SiC‐MOSFET

“…16 However, due to individual differences, temperature dependence and F I G U R E 1 Circuit configuration aging/deterioration of gate drive ICs and the power devices themselves, we found that it is difficult to apply this method practically in feedforward control with fixed delay times. We also proposed a method of digitally controlling the delay time provided to the gate signal to improve the voltage unbalance and confirmed the effectiveness of the method through experiment.…”

“…We also proposed a method of digitally controlling the delay time provided to the gate signal to improve the voltage unbalance and confirmed the effectiveness of the method through experiment. 16 However, due to individual differences, temperature dependence and F I G U R E 1 Circuit configuration aging/deterioration of gate drive ICs and the power devices themselves, we found that it is difficult to apply this method practically in feedforward control with fixed delay times.…”

“…1 We will show that, by applying this method, it is possible to control voltage unbalances caused by the individual differences between series-connected MOSFET devices and the characteristic differences of the gate drive circuits. 16 Figure 1, the resistors R s1 and R s2 that are connected in parallel to the MOSFET devices are provided to balance the steady state voltage when the MOSFET devices are off. Note that, in this control method, since we are using feedback control, we cannot control the voltage unbalances that occur at the start of switching.…”

“…Note that, in this control method, since we are using feedback control, we cannot control the voltage unbalances that occur at the start of switching. 16 proposes a method of providing a delay time to the gate signal as a method to improve the voltage unbalance at turn-off of series-connected SiC-MOSFET devices. To demonstrate the effectiveness of the method proposed in this article, we fabricated a stepdown chopper circuit by series-connecting two 1.2 kV SiC-MOSFET devices, and conducted a 500 V, 25 A experiment.…”

“…According to Ref. 16 , a gate signal delay time on the order of 1 ns or shorter Figure 1, the resistors R s1 and R s2 that are connected in parallel to the MOSFET devices are provided to balance the steady state voltage when the MOSFET devices are off. Note that the resistance value was set to 1 MΩ so that the time constant with the output capacitor (150 pF) would be 150 s, which is sufficiently longer than the turn-off time, thereby not affecting the voltage at the MOSFET device turnoff transient.…”