What is the relationship between switching loss and performance of IGBT module?
In the development of IGBT, power switching devices are required to reduce losses, improve efficiency and improve performance. The losses of switches can be divided into two categories, one is the losses of devices with normal on-state; The other is the switching loss from on state to off state (from off state to on state). The main technical characteristics of IGBT are collector-emitter saturation voltage VCE(sat) characteristics and switching characteristics tf (the sum of off time toff and on time ton). The breakdown performance of IGBT depends on blocking performance, short circuit performance, di/dt and dv/dt performance.
(1) Technology for improving switching characteristics
The technology developed to improve the switching characteristics is mainly to optimize the concentration and layer thickness, reduce the holes that become carriers, and reduce the unique collector current tailing of IGBT. By optimizing the cell pattern, the input impedance RG is reduced, and the charging and discharging time of some gates of power MOSFET is increased. On the basis of increasing the speed of power devices, the technology adopted is to shorten the life of the carrier. As the methods of life limitation, heavy metal diffusion method and electron ray irradiation method are commonly used. By controlling the lifetime, the turn-off characteristics of IGBT collector current Ic can be controlled. Reducing the gate capacitance of power MOSFET can make the charging and discharging time reach high speed.
(2) Reduce VCE technology
The technology of reducing VCE(sat) is to reduce the resistance part by optimizing the concentration, thickness and depth of the layer, and improve the current density per unit area by means of refinement, so as to optimize the ratio of Lg to Ls, enlarge the unit chip area of the inversion layer (channel) of power MOSFET and reduce the channel resistance.
By using improved switching characteristics technology and increasing the life limit, the switching characteristics can be accelerated. In IGBT, VCE(sat) is correlated with switching characteristic tf. With the help of life time control, any required working state can be found in this relationship.
(3) Technology to improve performance
In order to improve the breakdown performance of IGBT, the IGBT performance improvement technology is adopted, which suppresses the work of parasitic NPN transistor in IGBT and the concentration of electric field and current in IGBT, thus improving.了
IGBT的击穿性能。
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