Study On Failure Characteristics And Condition Monitoring Method Of Power MOSFET Device

In recent years,with the continuous development of crucial fields of the safety reliability such as renewable energy,aircraft carrier on water and aerospace construction,more and more attention has been paid to the reliability of switching power supply devices.Power device is one of the most easily damaged and aging parts in switching power supply device.Once the unpredictable failure of the switching power supply occurs owing to the power device,it will cause unpredictable economic losses.In order to improve the service life and reliability of power devices,characteristics of aging and failure,and methods of monitoring state of power devices in the switching power supply devices have become a research hotspot.The power MOSFET device has been widely used in the switching power supply devices in aircraft carrier,aerospace and other related fields on account of its characteristics including the low on-resistance,low power dissipation in the driving,fast speed in the switching and easy integration.For this reason,this paper will focus on the characteristics of aging and failure,and the reliability of MOSFET of the switching power supply device.And the research will be carried out from the establishment of electrothermal model,simulation analysis of aging characteristics,extraction of state characteristics and method of monitoring state.The specific contents are as follows:The accurate and fast electrothermal simulation models of power MOSFET device have been established.Firstly,the electrical behavior model of the device was established based on the SABER simulation platform to obtain the electrical network parameters.And then,based on the thermal conductivity characteristics of each layer of the MOSFET,the Cauer heat network model reflecting the thermal characteristics of the device was established,and its thermal network parameters were extracted according to the Datasheet thermal impedance curve.On the basis of the above models,the simulation of the aging characteristics of bonding wire indicated that the safety and reliability of the device in operation decreased with the increase of on-resistance.By building the Buck circuit to simulate the aging characteristics of the solder layer,the study suggested that the junction temperature would fluctuate during the switching process of the MOSFET,and the device would withstand great temperature stress,which led to the increase of thermal resistance and decrease of the reliability of the MOSFET device.A power cycle aging test bed for accelerated aging of power MOSFET devices was designed,and the concrete proposals for the main circuit aging and the aging control were put forward,which achieved accelerated aging of multiple power devices at the same time.Meanwhile,according to the simulation of the aging characteristics of the bonding wire and the solder layer,the on-resistance and thermal resistance were selected as the parameters of aging characteristics for the power MOSFET device.On the one hand,the research,taking the on-resistance as the study object,summarized the influence of devices on the on-resistance under different aging states,drain-source current,gate driving voltages and junction temperatures.On the other hand,the research whose study object was the thermal resistance found out the rule of changing with the aging.For the state monitoring of the bonding wire and the connection part,the direct onresistance monitoring method could directly measure the change of on-resistance.The generalized output characteristics based on the converter,such as the transient voltage peak of the Buck converter output and the frequency response of the Boost converter,could indirectly achieve monitoring the health status of the internal MOSFET.The monitoring of the fatigue state of the MOSFET welding layer mainly referred to the identification of the thermal network parameters of junction temperature curve and cooling curve.The two curves were vital for the comprehensive identification of the health status of the device and even the power supply device.Monitoring the aging change law of its parameters could ensure that the device temperature was in the safe scope for working to reduce the risk of failure to a certain extent,so that the entire switching power supply device could operate safely and reliably.