A self turn-on mechanism of the synchronous rectifier in a DC-DC converter

The voltage of the power supplies of the microprocessor becomes low for the small heat generation. The synchronous rectifier of the MOSFET is used in the DC-DC converter of low output voltage for making the conversion efficiency high. When the high-side switch is turned on in this buck converter, the low-side switch which must stay in the off state becomes the active state and the power dissipation of the low-side switch increases. A mechanism of the self turn-on phenomenon was presented in Intelec´03 (see ibid K. Murata et al., 2003) when the gate drive impedance is high. This self turn-on can be removed by making the gate drive impedance low, however, a self turn-on of another mechanism occurs. The latter turn-on is a serious problem in the actual cases because that we cannot make the dissipation low even if the gate drive impedance is low. Another mechanism is made clear when the gate drive impedance is low.