| Abstract |
This paper presents new technological enhancements for current sensing by means of the parasitic inductance of a semiconductor module. Across this measurement section, a signal, which is proportional to di/dt, can be tapped. Traditionally, the connections for emitter (E) and auxiliary emitter (E') of an IGBT module are used. The measured signal has to be processed with an integrating component to get the reconstructed current. Doing this, many peculiarities and challenges of this method arise, which have to be overcome when the accuracy of state of the art current sensors must be reached. A first error source is the parasitic resistance in the measurement section, which makes it impossible to use a simple integrator. However, it was found that also an active low pass filter, which seems to be a more appropriate integrator, cannot be adapted in such a manner that an exact representation of the current is possible. Resulting from this, an exact timing of the integrator's output is necessary to get an error-resistant current signal, which may be used for the control loop. Also further approaches are presented in this paper, which try to mitigate the module temperature dependence of the current sensing method. Because this method needs taps with current flow and inductance between them integrated in the module to work at all, it was a motivation to test also other measurement positions, which have not been examined yet but make the current sensing method more flexible. It was found that also in these positions current sensing is possible but only with a downstream correction of the sensed signal. These corrections are also outlined in this work. With this perceptions, an alternative current measurement approach, which takes the semiconductor module itself as a sensor, can be designed more accurately and makes it more comparable to the state-of-the-art current sensors. |
