Current injection technique: Difference between revisions

Revision as of 16:59, 16 June 2009

Revision as of 17:02, 16 June 2009

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== Details of the Technique ==

The current injection technique examined in Dr Eio's publications optimize the switching transient of power diodes, [[Thyristor|thyristors]] and [[Insulated Gate Bipolar Transistor|insulated gate bipolar transistors]] (IGBTs) without the need of changing the structure of these devices. To implement the current injection technique, [[current]] injection circuit was developed with results indicating that the injection of an additional current during its switching transient can reduce the reverse recovery charge of a given power diode and [[Thyristors|thyristor]], and also reduce the tail current of [[Insulated Gate Bipolar Transistor|insulated gate bipolar transistors]].

Practical experimental results on [[diodeDiode|diodes]]s and [[thyristorThyristor|thyristors]]s showed that the amplitude of the injected current required is proportional to the peak reverse recovery current and proved that these devices experience a momentary increase in recombination of current carriers during the injection of the additional current. This help to prevent the device from conducting large negative current, which in turn reduce its reverse recovery charge and reverse recovery time. Results obtained from experiments with an IGBT showed a significant reduction in the time where current falls to zero when opposing current was injected into the device during its turn-off transient. Further simulation results from numerical modeling showed that the injected opposing current temporary increase recombination in the device and therefore reduce the extracted excess carriers that was stored within the device.

To prevent circuit commutation and bonding between the current injection circuit and the main test circuit where the Device under Test (DUT) is connected to, a non-invasive circuit was developed to magnetically couple the two circuits.

In summary, the proposed technique makes it possible to use devices with low forward voltage drop for high frequency applications. This also imply cheaper cost of devices as less processing steps are required during the manufacturing stages where the need of carrier lifetime control techniques are reduced.n test circuit where the Device under Test (DUT) is connected to, a non-invasive circuit was developed to magnetically couple the two circuits. This removed the need for the semiconductor device used in the current injection circuit to have high breakdown voltage rating and also provided electrical isolation. Typical application of this technique in an inductive load chopper circuit showed a significant reduction in the IGBT tail current, and the reverse recovery time and charge of the freewheeling diode used.