A power circuit combination includes a series capacitor buck converter including a first half-bridge including a first high side power switch (HSA), first low side power switch (LSA) and a second half-bridge. A transfer capacitor (Ct) is connected in series with HSA and LSA, and between the first and second half-bridges. An adaptive HS driver circuit has an output coupled to a gate of HSA and includes a power supply circuit including a summing circuitry that dynamically outputs a variable power supply level (VGX) based on a fixed voltage and a voltage across Ct, a buffer driver, and a boost capacitor (CA) across the buffer driver. VGX is coupled to a positive terminal of CA. The power supply circuit is configured so that as a voltage across Ct varies, VGX adjusts so that a voltage across CA is changed less than a change in voltage across Ct.