A common output terminal 1070 electrically couples the output of the first powertrain phase 1001 and each second powertrain phase 1002N to the output power line. A common input line 1080 electrically couples the input of the first powertrain phase 1001 and each second powertrain phase 1002N.

The DC-DC power converter chiplet 1000 includes control circuitry 1020 that can turn on or off any of the first powertrain phase 1001 and/or any second powertrain phase 1002N that are electrically connected to the load current (e.g., to the output power line) to improve the power conversion efficiency, which can vary as a function of the load current. The power conversion efficiency of a DC-DC power converter chiplet, such as DC-DC power converter chiplet 1000 is calculated as the ratio of the output power to the input power. In other words,

${\eta }_{\mathrm{chiplet}}=\frac{P_{\mathrm{out}}}{P_{\mathrm{in}}}.$
The power conversion efficiency of any phase is determined in the same way,

${\eta }_{\mathrm{phase}}=\frac{P_{\mathrm{out}?\_?\mathrm{phase}}}{P_{\mathrm{in}?\_?\mathrm{phase}}}.$