This paper discusses a problem that a half-bridge circuit can generate, namely a false trigger by high-speed switching transition. In general, a false trigger occurs by charging a gate-source capacitance because of high-speed voltage transition and influx of current via a reverse transfer capacitance. Therefore, it is thought that the ratio of the input capacitance and the reverse transfer capacitance is important to check whether a false trigger occurs. However, we find another reason and propose a novel assumption. A novel false triggering mechanism appears by considering the source-side parasitic inductance.