IGBT driver optimises slew rate for minimum losses, in real time

May 21, 2014 // By Graham Prophet
For power switching applications up to 1200V, Infineon's latest single channel gate driver in its EiceDRIVER product family has been developed for high-end systems in the industrial sector. The type 1EDS20I12SV EiceDRIVER Safe driver component features Slew Rate Control (“SRC”) adjustable in real-time at the IGBT.

Slew Rate Control lets developers choose from among a total of eleven collector emitter voltages at turn-on. Depending on design requirements, this means the switching speed of the IGBTs and the EMI behaviour can be varied flexibly during operations. Fast IGBT turn-on enables high switching frequencies. On the other hand, slow turn-on reduces electromagnetic interference (EMI) and voltage peaks by reflection at the motor. This means a reduced burden on isolations and increased motor service life, and thus lower overall system costs.

If the slew rate is too fast, switching transients will induce ringing in the power waveforms, with high levels of EMI. If too slow, then not enough energy is delivered to the gate of the power switch to properly drive it, and switching losses increase. This driver allows setting of the optimum point of operation to minimise both EMI and switching losses.

The improved switching behaviour lets developers use smaller dv/dt filters or even eliminate them completely in an application design. Compared to conventional driver components without Slew Rate Control, the 1EDS-SRC EiceDRIVER Safe saves approximately 30% of turn-on loss reduction. Infineon says that the combination of SRC and secure electric insulation has not previously been available.

Protective functions prevent overload and damage to the system at turn-off. The basic configuration includes both UVLO (under voltage lockout) and optionally available automatic turn-off in case of a short circuit. The short circuit itself can be detected in two different ways: By monitoring collector emitter voltage (desaturation detection) or by detecting voltage drop at a current-sensing resistor. In both cases the 1EDS-SRC EiceDRIVER Safe implements a soft off, slower than a normal transition. The voltage drop in case of failure can be controlled even more precisely using TLTO (two-level turn-off). The 1EDS-SRC EiceDRIVER Safe offers optimum control of short circuits in three-level inverters in particular, since the automatic short-circuit turn-off can be deactivated for the driver IC.

Infineon; www.infineon.com/eicedriver