We describe a semiconductor-on-insulator integrated circuit die comprising a substrate bearing a power conditioning circuit, the power conditioning circuit comprising at least two power devices, a lateral power device and a vertical power device. The power conditioning circuit comprises: a DC input to receive DC power, an AC output for connection to AC mains; a DC-to-DC converter having an input coupled to said DC input; a DC-to-AC converter having a DC input and an AC output to convert DC power to AC power for mains output; and a DC voltage regulator coupled between the output of said DC-to-DC converter and the input of said DC-to-AC converter to regulate said DC voltage input to said DC-to-AC converter. The regulator is configured to control an AC output current of said circuit by controlling said DC voltage input to the DC-to-AC converter.