Heat flux-based sensor for the measurement of the power dissipated by switching devices

The precise measurement of the power dissipated by a semiconductor device operating in fast dynamic conditions is an important issue in power conversion circuits to evaluate their overall efficiency. Measurement errors can be introduced in particular by the probes or by instruments that are transparent to high dv/dt and di/dt rates. For this reason, the use of bulky and expensive set-up´s is often required. We present a simple method based on a micromachined dual-sensor heat-flux measurement device, coupled to a readout circuit, that allows the estimation by calorimetry of the dissipated power. By means of a controlled Peltier heat pump, the switching device is held at room temperature in order to minimise the heat exchanged with the ambient and improve therefore the precision of the measurement. The sensor could be in principle integrated within the switching device case itself, to allow the lifelong monitoring of the produced heat.