3rd generation SiC MOSFETs with New package TO-247-4L(X) released

Compared to Si (silicon) IGBTs and MOSFETs, which are currently mainstream, power MOSFETs using SiC (silicon carbide) not only excel in low conduction loss and operation in high-temperature environments, but also contribute to low-loss application through high-speed switching.
TO-247-4L(X), a new package for our 3rd generation SiC MOSFETs, is a 4-terminal type, and by reducing the influence of the inductance of the source wire inside the package, it is possible to draw out high-speed switching performance. This contributes to lower loss in applications such as servers, uninterruptible power supplies (UPS), and Photovoltaics Inverter.
Below is a comparison of features and switching loss reduction effects for our new package TO-247-4L(X) (4-terminal type) and our existing product TO-247 (3-terminal type).

3rd generation SiC MOSFETs with New package TO-247-4L(X) released

Features of TO-247-4L(X) package

In the three-terminal type, As shown in Fig. 1, when the gate drive voltage VDRV is applied, the inductance component L of the source wire and the gradient dID / dt component of the drain current ID generate a counter electromotive voltage VLS.
Therefore, the gate drive voltage VDRV is reduced by the back electromotive voltage VLS. The voltage VGS applied between the gate and source of the FET chip is the gate drive voltage VDRV reduced by the counter electromotive voltage VLS. This slows down the switching speed of SiC MOSFETs.

Fig. 1 3-terminal type
Fig. 1 3-terminal type

On the other hand, As shown in Fig. 2, 4-terminal type reduces the effect of back electromotive voltage VLS by connecting the signal source terminal for gate drive close to the FET chip. As a result, in the 4-terminal type, the voltage VGS applied between the gate and source and the gate drive voltage VDRV are approximately the same value, and the switching speed of the SiC MOSFET is improved compared to the 3-terminal type.

Fig. 2 4-terminal type
Fig. 2 4-terminal type

Switching loss reduction effect

Fig. 3 shows the turn-on switching waveforms of the 4-terminal type and the 3-terminal type by inductive load switching. At turn-on, the drain current ID (dotted red line) of the 4-terminal type rises steeper than the drain current ID (dotted blue line) of the 3-terminal type.
This is because the 4-terminal type shown in Fig. 2 reduces the influence of the inductance of the source wire compared to the 3-terminal type, and it suppresses lowering the gate drive voltage during switching. Therefore, the 4-terminal type has a faster turn-on speed than the 3-terminal type.

Fig.4 also shows the turn-on loss Eon of 4-terminal type and 3-terminal type. The turn-on loss Eon of 4-terminal type is approximately 40% lower than that of the 3-terminal type.

Fig. 3 Turn-on switching waveform
Fig. 3 Turn-on switching waveform
Fig. 4 Turn-on loss (E<sub>on</sub>)
Fig. 4 Turn-on loss (Eon)

 

Measurement condition
VDD = 800 V, VGS = 18 V / 0 V, ID = 20 A, Ta = 25 ℃, L=100 μH, Rg (external gate resistor) = 4.7 Ω
The freewheeling diode uses the diode between the source and drain of each product.
(Toshiba internal comparison, as of July 2023)

Fig. 5 shows turn-off switching waveforms for 4-terminal and 3-terminal types due to inductive load switching. At turn-off, the drain current ID (dotted red line) of the 4-terminal type decreases faster than the drain current ID (dotted blue line) of the 3-terminal type. In other words, the 4-terminal type turns off is faster than the 3-terminal type.

Fig. 6 also shows the turn-off loss Eoff for the 4-terminal type and 3-terminal type. The turn-off loss Eoff of the 4-terminal type is approximately 34% lower than the turn-off loss Eoff of the 3-terminal type.

Fig. 5 Turn-off switching waveform
Fig. 5 Turn-off switching waveform
Fig. 6 Turn-off loss (E<sub>off</sub>)
Fig. 6 Turn-off loss (Eoff)

 

Measurement condition
VDD = 800 V, VGS = 18 V / 0 V, ID = 20 A, Ta = 25 ℃, L=100 μH, Rg (external gate resistor) = 4.7 Ω
The freewheeling diode uses the diode between the source and drain of each product.
(Toshiba internal comparison, as of July 2023)

To summarize the above, Fig. 7 shows the relationship between turn-on loss Eon and turn-off loss Eoff with respect to external gate resistance Rg for 4-terminal and 3-terminal types.

  • Both the 4-terminal type and the 3-terminal type tend to increase turn-on loss Eon and turn-off loss Eoff as the external gate resistance Rg increases.
  • The 4-terminal type has smaller turn-on loss Eon and turn-off loss Eoff than the 3-terminal type.
Fig. 7 R<sub>g</sub> dependence of turn-on loss (E<sub>on</sub>) and turn-off loss (E<sub>off</sub>)
Fig. 7 Rg dependence of turn-on loss (Eon) and turn-off loss (Eoff)

 

Measurement condition
VDD = 800 V, VGS = 18 V / 0 V, ID = 20 A, Ta = 25 ℃, L=100 μH, Rg (external gate resistor) = 4.7 Ω
The freewheeling diode uses the diode between the source and drain of each product.
(Toshiba internal comparison, as of June 2023)

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