SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

[Guide]Modern industry has put forward many requirements for power Electronic equipment: small size, light weight, high power, and low heat generation. Faced with these requirements, Si MOSFETs are unable to do anything due to the limitations of Si materials. SiC MOSFETs have begun to show their magical powers due to the inherent advantages of SiC materials. The only disadvantage of large-scale commercial use of SiC MOSFETs is the price.

Modern industry has put forward many requirements for power electronic equipment: small size, light weight, high power, and low heat generation. Faced with these requirements, Si MOSFETs are unable to do anything due to the limitations of Si materials. SiC MOSFETs have begun to show their magical powers due to the inherent advantages of SiC materials. The only disadvantage of large-scale commercial use of SiC MOSFETs is the price. However, with the increase in yield and the use of larger wafers, the cost gap between SiC and Si is narrowing, and there is a clear advantage in the overall cost of the vehicle system. SiC MOSFET has become a new choice for more and more manufacturers to replace Si MOSEFET.

One of the differences between the driving of SiC MOSFET and Si MOSFET is the difference in driving voltage. Traditional Si MOSFET driving requires only a single positive voltage supply, while SiC MOSFET requires a single positive and negative voltage drive. To replace Si MOSFET with SiC MOSFET, it is necessary to solve the problem of how to realize the negative voltage circuit.

Currently, SiC MOSFETs are mostly driven by +15/-3V and +20/-5V voltages. To realize the negative voltage circuit in the Si MOSFET single power supply positive voltage drive circuit, a small number of components can be added to the drive loop to generate the required negative voltage. If a drive voltage of +15/-3V is required, a single voltage needs to provide +18V That is, the following two solutions can be implemented specifically.

Option One:

Use the +14V voltage regulator tube Z1 plus the forward voltage drop of the Z2 tube to stabilize the voltage at about +15V when it is turned on, so that there will be a 3V voltage drop on the capacitor C10 when the switching tube is turned on; the switching tube is off When it is off, the lower tube inside the drive chip is turned on and the voltage applied to GS is -3V.

SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

figure 1

Option II:

Use the 3V Zener tube Z1 to stabilize the negative voltage for driving. When the capacitor C10 is turned on, the voltage of 3V is stabilized, and the positive driving voltage is maintained at 15V. When it is turned off, the voltage applied to GS is the voltage of capacitor C10, which is -3V.

SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

figure 2

The driving waveforms of Scheme 1 and Scheme 2 are as follows:

SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

Figure 3: Scheme 1 driving waveform

SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

Figure 4: Scheme 2 drive waveform

It can be seen from the above two driving waveform diagrams that both solutions can use very few components to achieve the required driving negative pressure, but the device is 0V before the first operation, and cannot maintain a stable negative pressure in the normally-off state , It is easy to be disturbed and opened by mistake. To solve this problem, you can add a resistor R1 to pull up. After power on, the capacitor C10 is pre-charged and stabilized at 3V, so that the negative voltage can be maintained when it is not working, as shown in Figure 5.

SiC MOSFET replaces Si MOSFET. How to achieve negative voltage when there is only a single power supply with positive voltage?

Figure 5

In summary, in the case of a single power supply, only minor adjustments to the circuit are required to realize the replacement of Si MOSFET with SiC MOSFET.

Pinejie has mass-produced SiC MOSFETs for 650V-1700V voltage platforms. The products are manufactured by X-FAB, a SiC foundry with a 30-year history of automotive regulations. They comply with automotive regulations and can replace Si MOSFETs in photovoltaics, new energy vehicles and other applications. And IGBT.

sample application

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(Source: Pine Jie)

The Links:   LM64P844 1DI300MN-050

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