Analysis of a self turn-on phenomenon on the synchronous rectifier in a DC-DC converter

In the buck converter with MOSFETs, the low side switch, which must be still in cutoff state, becomes turn-on when the high side switch is turned-on and the current flows through the circuit of the power supply. We call this phenomenon self turn-on. The power dissipation by this current becomes higher when the switching frequency of the converter is high as MHz. This self turn-on occurs easily in the converter of low output voltage and high voltage conversion ratio. We present the principle of self turn-on phenomenon on circuit simulation and experimental results.