AN2123

Active Miller clamp

7/15

For very high-power applications, the active clamp function cannot replace the negative gate drive, due to

the effect of the parasitic inductance of the active clamp path. In these cases, the application can benefit

from the CLAMP output as an secondary gate discharge path (see Figure 11 below).

With the above schematic, when the gate voltage goes close to VL+2 V (i.e. the IGBT is already driven

off), the CLAMP pin is activated. Again, the benefit is to lower the resistance between gate and emitter

when the IGBT is in the OFF state without affecting the IGBT turn-off characteristics.

Tip:

What should one do with the CLAMP pin when not used in application?

Connect CLAMP to VL.

Figure 11. High power application: negative gate drive and secondary gate discharge path

VH

1

2

3

4

5

6

7

8

TD351

CD

IN

VREF

LVOFF

OUT

VL

CLAMP

VH

T1

T2

T3

16V

-10V