Why dont CONCEPT drivers turn off slowly in the event of a short circuit?
The driver circuits known under various designations, such as “two-stage turn-off”, “soft switch-off”, “slow turn-off” uses a low-ohmic gate resistor in normal operation to turn the IGBT off in order to minimise the switching losses, and a high-ohmic resistor (or lower gate current) whenever a short-circuit or over-current is detected. However the problem lies in the reliable detection of these conditions: VCE monitoring always involves a delay (known in this case as the response time) that must elapse before an error is detected. This time is as a rule up to 10us. If a short circuit is in fact present and the IGBTs are driven with a pulse which is shorter than the response time, the error is not detected and the circuit switches off too quickly. The IGBT is then destroyed via an over-voltage. Moreover the coverage of limit cases (between over-current / not over-current) poses a problem. As a rule, such circuits must be regarded as dangerous and are therefore not used in CONCEPT produc
