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Lewin_Sa
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5 sign-ins First reply posted First question asked

Hello, regarding the IGBT product of the FF600R12ME4 model, I am conducting a double pulse test and found that adding a Snubber capacitor between the capacitor busbar and the IGBT driver reduces the peak of the lower tube Vce, but Ic also exhibits significant oscillations. As shown in the figure below, the yellow channel represents the lower tube Vge, the green channel represents the Ic current, and the red channel represents the lower tube Vce. May I ask if there is a way to reduce the oscillation of Ic.

600V 30US_000.png

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Rachel_G
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50 likes received 250 solutions authored 250 replies posted

Hello,

It is recommended to increase the gate resistance(Rg) of the lower tube to slow down the switching speed, which is helpful to reduce Vce voltage spike and improve oscillation. The oscillation of the current waveform is mainly caused by the parasitic inductance and parasitic capacitance of the power loop.  You need to adjust the value of Rg and snubber capacitor to balance the voltage spike and oscillation.

Best regards,

Rachel

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Rachel_G
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50 likes received 250 solutions authored 250 replies posted

Hello,

The oscillation phenomenon is mainly caused by the parasitic inductance of the driver loop and power loop, and fast di/dt, it is recommended to appropriately increase the gate resistance (Rg) and optimize the PCB parasitic inductance of the driver loop and power loop.

Best regards,

Rachel

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Dear Rachel:

The following figure shows the connection diagram of the power circuit we measured. The driver loop and IGBT power loop are independent of each other, so we are currently working to determine whether the power loop can reduce parasitic inductance.

In this dual pulse test, we used The inductance of  62 μH is parallel connected to the upper tube of IGBT, and the parasitic inductance calculated based on the test waveform is about 50nH. As shown in the figure below, the oscillation of the Vge gate position in our lower transistor appears to be very small, and the current oscillation is mainly reflected in the Ic waveform of the lower transistor.

Best regards,

Lewin

Lewin_Sa_0-1686884252487.jpeg

 

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Dear Rachel:


If the Snubber capacitor in the figure below is removed, this Ic oscillation will be eliminated, but Snubber is an essential component of the product. May I ask for your advice again。

Best regards,

Lewin

600V 30US_014.png

Snubber.jpg

 

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Rachel_G
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50 likes received 250 solutions authored 250 replies posted

Hello,

It is recommended to increase the gate resistance(Rg) of the lower tube to slow down the switching speed, which is helpful to reduce Vce voltage spike and improve oscillation. The oscillation of the current waveform is mainly caused by the parasitic inductance and parasitic capacitance of the power loop.  You need to adjust the value of Rg and snubber capacitor to balance the voltage spike and oscillation.

Best regards,

Rachel

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