Those who design with IGBTs or Insulated Gate Bipolar Transistors know how difficult it is to select the proper component for a specific application. Several factors have to be carefully weighed simultaneously before you can zero in on the right product. IGBTs are very useful in equipment handling high power, with huge currents passing through them. Failure due to a mismatch involves high expensive replacements. Therefore, engineers have to be very selective when deciding on the right component to use.
For IGBTs, just as for any other semiconductor component, the junction temperature plays a very crucial role in maintaining the proper operation and life of the component. Other parameters that the designer must take into account are the operational voltage, the continuous and maximum currents and the power that the IGBT must handle. While the designer has to rely solely on the information provided to him by the manufacturer, the datasheet of a specific component may be cumbersome and static. From the steady-state figures provided by the manufacturer, it may be difficult to estimate the performance a particular part will play when placed in a circuit.
The website of ezIGBT makes things easier for the designer. It liberates him from the paper data and allows him to model the performance of a part, given specific conditions of junction temperature, operating frequency, applied voltage, current and size of heat sink. The website provides several IGBT models and ezIGBT takes great care to maintain the accuracy of the data.
On the website of ezIGBT, the designer has to supply several operational parameters. These include the on-time voltage across the Collector and Emitter or Vceon, the forward voltage across the copak diode or Vf, on-time voltage or Von, off-time voltage or Voff and the reverse recovery voltage or Err. The website then uses Industry standard techniques to generate equations in two sets: one at 25°C and the other at the highest possible junction temperature.
The equations compute the losses and thermal conditions for the device selected, with the parameters being linearly interpolated between the two temperatures. The datasheet graphs are generally curve-fitted, and expected errors remain less than 10%, which are below the normal variations in manufacturing these devices. At present, ezIGBT is only providing calculations based on “hard switching” type of converters. Calculations for resonant operations are planned for the future.
The website provides three types of tools: Analyze, Compare and Recommend. The Analyze tool helps the designer calculate the power loss at the operating frequency, when the designer specifies the junction temperature and duty cycle. This tool also allows an understanding of how the losses are split between the IGBT and its diode. With this data, the website also estimate the size of the heat sink required.
On the Compare page, you can run the analysis calculated in the previous Analyze section, along with the additional ability to compare the performance of multiple IGBTs.
When you choose your operating conditions, ezIGBT can recommend the parts that will most closely match the requirements of your application. This is done in the Recommend section. At present, the selection depends on the incremental junction temperature rise over the case temperature. Other criteria are expected to be addressed in the future.
