Improvements in the efficiency of two charge pump designs are presented. As a charge pump switches between modes, capacitances are charged. Due to charge sharing between capacitances, inefficiencies are introduced. Techniques for reducing these inefficiencies are presented for two different charge pump designs are presented. For a clock voltage doubler type of pump, a four phase clock scheme is introduced to pre-charge the output nodes of the pump's legs. For a pump design where a set of capacitances are connected in series to supply the output during the charging phase, one or more pre-charging phases are introduced after the reset phase, but before the charging phase. In this pre-charge phase, the bottom plate of a capacitor is set to the high voltage level prior to being connected to the top plate of the preceding capacitor in the series.