Power measurements generally entail measuring voltage and current waveforms and creating a product of the two with a perfectly aligned time axis. Misaligned timing axes in voltage and current will distort the actual power value, severely undermining the credibility of it. Voltage and current waveforms are sampled through different probes with different sampling circuits, different amplifiers, different cable lengths, and using different processing algorithms inside the oscilloscope. Their timing axes are independent and the effect of the timing misalignment (skew), generally overwhelms the real, physical power being
measured.
The In-Situ method non-intrusively performs the precise power measurement during when the target circuit (e.g., a power converter) is in operation and while completely free from the effects of the timing skew between the voltage and current. Aside from precisely extracted voltage and current waveforms, information about the timing alignment of the voltage and current is extracted with this method and is based on the circuit topology and expected operation waveforms. This method enables In-Situ power measurements in general power converters, which has been never practiced before, and can be applied to power converters with non-sinusoidal waveforms, DC-bias, and multiple, local, minor B-H loops. This direct power measurement method accurately accounts for all nonlinear loss mechanisms of a component.
