Detailed explanation of five damage modes of power MOS tube

时间2018/11/4 15:21:05
The first type: avalanche destruction

If A surge voltage exceeding the rated VDSS of the device is applied between the drain and the source, and the breakdown voltage V(BR)DSS is reached (depending on the value of the breakdown current), and damage occurs after a certain amount of energy is exceeded.

in The flyback voltage generated when the switch of the medium load is turned off, or the peak voltage generated by the leakage magnetic inductance exceeds the powerMOSFET drain rated withstand voltage and enter the breakdown zone to cause damage will cause avalanche damage.

Typical circuit:

Second type: device thermal damage

It is caused by heating caused by exceeding the safe area. The cause of heating is divided into two types: DC power and transient power.

DC power reason: heat caused by loss caused by external DC power

On-resistance RDS(on) loss (RDS(on) increases at high temperature, resulting in increased power consumption at a certain current)

● Loss caused by leakage current IDSS (very small compared to other losses)

Cause of transient power: additional one-shot pulse

Load short circuit

Switching loss (on, off) * (related to temperature and operating frequency)

the trr loss of the built-in diode (short-circuit loss of the upper and lower arms) (related to temperature and operating frequency)

The overcurrent caused by the load short circuit that does not occur during the normal operation of the device causes instantaneous local heating and causes damage. In addition, when the heat is not matched or the switching frequency is too high to allow the chip to dissipate normally, the continuous heat will cause the temperature to exceed the channel temperature and cause the destruction of thermal breakdown.

The third type: built-in diode destruction

When the parasitic diode formed between the DS terminals is operating, because the parasitic bipolar transistor of the power MOSFET operates during Flyback,

the pattern that led to the destruction of this diode.

The fourth type: damage caused by parasitic oscillation

This destruction method is especially easy in parallelhappen

The parasitic gate oscillation occurs when power MOS FETs are connected in parallel without inserting gate resistors. High-speed repeated switching on and offWhen the drain-source voltage is open, the gate This parasitic oscillation occurs in the resonant circuit formed by the pole-drain capacitance Cgd (Crss) and the gate pin inductance Lg. When the resonance condition (ωL=1/ωC) is established, a vibration voltage far greater than the driving voltage Vgs(in) is applied between the gate and the source, and the gate is destroyed due to exceeding the rated voltage between the gate and the source, or The vibration voltage when the drain-source voltage is turned on and off causes positive feedback due to the overlap of the gate-drain capacitance Cgd and the Vgs waveform, which may cause oscillation damage due to malfunction.

the fifth type: grid surge, electrostatic damage

The main damage is caused by voltage surge and static electricity between the gate and source, that is, gate overvoltage damage and static electricity on both ends of GS ( Including the grid damage caused by installation and testing equipment)




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