Simple adaptive gate drive circuits, applicable to switches that turn on at zero voltage, such as mosfets or IGBTs, are revealed. The new gate drive circuits improve the timing for turn on of the switches, reduce gate drive losses, and limit gate voltage stress. In its simplest form the gate drive circuit requires only a single small mosfet and two diodes. The adaptive gate drive circuit provides optimal switch turn on timing for the case in which the drive energy available to drive the turn on transition is sufficient to drive the main switch to zero volts. The adaptive gate drive circuit also provides optimal switch turn on timing for the case in which the energy available to drive the transition is insufficient to drive the transition all the way to zero volts, turning the main switch on at the minimum main switch voltage thereby minimizing main switch switching losses.