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2SMLT0220D2I0C

Rev. A 04/25

Advanced Active Clamping (AAC)

Active clamping is a technique designed to partially turn on the power

semiconductor in case the drain-source voltage exceeds a predefined

threshold. The power semiconductor is then kept in linear operation.

Figure 4 illustrates the general behavior of active clamping and its

voltage thresholds. Basic active clamping topologies implement a

single feedback path from the power semiconductor collector/drain

through transient voltage suppressor (TVS) diodes to the power

semiconductor gate. The gate driver contains Power Integrations’

Advanced Active Clamping (AAC) based on this principle: When active

clamping is activated, the turn-off MOSFET of the gate driver is

switched off in order to improve the effectiveness of the active clamping

and to reduce the losses in the TVS diodes. This feature is mainly

integrated in the secondary-side ASIC of the gate driver.

To ensure that the gate-source voltage stays close to the nominal turn-

on voltage each MAG features a gate-clamping circuitry. The gate

clamping provides a voltage similar to V

VISO to the gate, i.e.

15 V. As the effective short-circuit current is a function of the gate-

source voltage the short-circuit current is limited. As consequence, the

energy dissipated in the power semiconductor during the short-circuit

event is reduced, leading to a junction temperature within the short-

circuit safe operating area (SCSOA) limits and enables a safe turn-off

of the device.

It should be noted that AAC should not be activated during regular

operation to avoid excessive heating of the transient voltage suppressor

diodes.

Conformal Coating

The electronic components of the gate driver are protected by a layer

of acrylic conformal coating with a typical thickness of 50µm using

ELPEGUARD SL 1307 FLZ/2 from Lackwerke Peters on both sides of the

PCB. This coating layer increases the product reliability when exposed

to contaminated environments.

Figure 4. Advanced Active Clamping

V

IGBT

with AAC

without AAC

V

TVS

V

DC

I

Load

v

CE

i

C

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