POWER DELIVERY CIRCUIT MONITORING

A power delivery circuit comprising power delivery components and a load (ZT) terminal, detectors for measuring voltages at two or more measuring nodes (V1, V3) of the power delivery circuit, and an estimation circuit for using the measurements to estimate current, voltage, or power delivered to a load by the power delivery circuit. The detectors may measure voltages at nodes of transistor switches of the power delivery circuit, particularly at the gates. The power delivery circuit may have a plurality of switches in series, and the detectors measure voltages at nodes of only a subset of the switches. The detectors in one example measure switch voltages and the estimation circuit estimates power delivered to the load according to a switch voltage and impedance between two nodes of the switch. The switch impedance may be provided during calibration using a reference load. The estimation circuit may be a simple analogue circuit such as an amplifier (AMP1) and a multiplexer (MX1). The invention is of particular benefit for measuring power delivered to a load of unknown impedance, such as an antenna of a mobile phone.