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## Switching losses of an IGBT

Employee
Employee
Hi, one question, how do you measure the switching losses of an IGBT?
1 Solution

## Re: Switching losses of an IGBT

Moderator
Moderator
Hi TechGirl,

the switching losses of an IGBT are measured using so-called double-pulse tests. The corresponding test circuit is depicted in all of our discrete IGBT data sheets (e.g. IKQ75N120CH3, p. 14, fig. E):

The picture below shows the principle current and voltage waveforms of the low side (LS) IGBT "DUT (IGBT)" during the double pulse test. Initially, the LS IGBT blocks the full DC link voltage, thus Vce=Vcc. At T0 the switch turns on and the current IC(t) rises with a rate Vcc/L. When the switch turns off at T1, the load current commutates from the LS IGBT to the high side (HS) diode "DUT (Diode)" where it is freewheeling until T2. Then, the LS IGBT turns on and takes over the current again. After a few microseconds it is turned off again. The load current commutates to the diode one last time and slowly decays to zero in tens or hundreds of milliseconds. Using this approach it is simple to produce defined turn-off and turn-on events at T1 and T2, respectively: while the voltage level is set directly with the DC link voltage Vcc the current value is adjusted with the width of the first pulse (T1-T0).

The switching losses during the turn-off (at T1) and turn-on events (at T2) are determined using an oscilloscope. With the oscilloscope, the voltage and current waveforms Vce(t) and Ic(t) of the devices under test are acquired. Multiplying Vce(t)*Ic(t) leads to a power waveform, integrating the power curve leads to the switching energy. The integration boundaries are standardized and described in each data sheet (e.g. IKQ75N120CH3, p. 14, fig. B).

If you want to perform double pulse tests yourself you might use one of our evaluation boards, for instance the EVAL-IGBT-1200V-247. For more information on this board refer to the application note AN2017-44

Hope this helps!
Best regards,
Klaus
1 Reply

## Re: Switching losses of an IGBT

Moderator
Moderator
Hi TechGirl,

the switching losses of an IGBT are measured using so-called double-pulse tests. The corresponding test circuit is depicted in all of our discrete IGBT data sheets (e.g. IKQ75N120CH3, p. 14, fig. E):

The picture below shows the principle current and voltage waveforms of the low side (LS) IGBT "DUT (IGBT)" during the double pulse test. Initially, the LS IGBT blocks the full DC link voltage, thus Vce=Vcc. At T0 the switch turns on and the current IC(t) rises with a rate Vcc/L. When the switch turns off at T1, the load current commutates from the LS IGBT to the high side (HS) diode "DUT (Diode)" where it is freewheeling until T2. Then, the LS IGBT turns on and takes over the current again. After a few microseconds it is turned off again. The load current commutates to the diode one last time and slowly decays to zero in tens or hundreds of milliseconds. Using this approach it is simple to produce defined turn-off and turn-on events at T1 and T2, respectively: while the voltage level is set directly with the DC link voltage Vcc the current value is adjusted with the width of the first pulse (T1-T0).

The switching losses during the turn-off (at T1) and turn-on events (at T2) are determined using an oscilloscope. With the oscilloscope, the voltage and current waveforms Vce(t) and Ic(t) of the devices under test are acquired. Multiplying Vce(t)*Ic(t) leads to a power waveform, integrating the power curve leads to the switching energy. The integration boundaries are standardized and described in each data sheet (e.g. IKQ75N120CH3, p. 14, fig. B).

If you want to perform double pulse tests yourself you might use one of our evaluation boards, for instance the EVAL-IGBT-1200V-247. For more information on this board refer to the application note AN2017-44

Hope this helps!
Best regards,
Klaus