Study On The Active Thermal Control Method For Discrete Type MOSFET

With the rapid development of new energy electric vehicles and industrial converters,power devices have been widely applied in contemporary industry.Due to the development of high power,high frequency and integrated technology,power devices usually suffer from excessive temperature rise,and thus their reliability have been greatly challenged.Device malfunctioning not only brings economic loss,but also causes significant accidents.In this context,the active thermal control method for power devices has been proposed.The main method of passive thermal protection is to turn off the output or work according to the pre-set reduction curve.In contrast,active thermal control is based on the power device temperature feedback and control strategy.Under the permitting condition of operation,the current output potential of power devices is stimulated dynamically and securely based on thermal inertia process.Therefore,the active thermal control method can improve the efficiency of the device and enhance the economic performance of the device,which is of both theoretical importance and practical value in engineering.The current temperature acquisition in active thermal control is generally realized by sensor temperature measurement or finite element method.However,for the medium and low speed electric vehicle controllers,the portable inverters and other object equipment,their internal power devices are mainly small discrete packages.The discrete device is relatively compact in layout and is easy to work in vibratory occasions.When using the sensor to measure the temperature,there are some problems such as difficulty in probe mounting and precision assurance,while the finite element method suffers from complicated computation and low engineering practicability.Hence,the application of the active thermal control method in the discrete power device is still difficult.Therefore,this paper has carried out research on the active thermal control method of discrete power device.Taking AOT470 MOSFET as object,the lumped parameter thermal circuit model has been built.Through parameter identification,the model parameters which were difficult to be calculated are obtained.The active thermal control method of the discrete power device based on the proposed thermal circuit model is proposed,which can reduce the difficulty of obtaining the temperature of discrete power and improve the engineering practicability of active thermal control in small devices.To verify the performance of thermal circuit model and the active thermal control method,an experimental platform is designed.The results have confirmed the effectiveness of the method.The results will help to improve the economic feasibility and safety of the discrete power device,and provide an important foundation for future applications in electric motor control of electric vehicle or industrial frequency conversion control and so on.