high-currenttransistors
In the datasheet, the transistor has two max current values, in the case of the IRF510
Continuous Drain Current = 5.6A
Pulsed Drain Current a IDM = 20A
with a pulse width of 20uS
Which is the assumed duty cycle for this values? Ts = 40uS and D = 50%?
Which current value should I consider if I want to work with a different duty cycle? 80% for example.
Here's a guide published by On Semiconductor on how to interpret their IGBT datasheets. It says that:
The pulsed collector current describes the peak collector current pulse above the rated collector current specification that can flow while remaining below the maximum junction temperature. The maximum allowable pulsed current in turn depends on the pulse width, duty cycle and thermal conditions of the device. (P. 2)
Look at page 4, fig.12, graph of safe operating area. That is exactly what you need.
You are talking about single pulse, right? You didn't mention any repetition or timing at all.
If you open mosfet hard, say Rdson is 0.85mOhms. In case of 1000A the Vds will be less than 1V, so you have to look at the left side of graph.
There is no line for 100ms pulse, so you have to interpolate between DC and 10ms pulse. The safe current is much lower than 1000A. It is like 400A. And it is the maximum.
Best Answer
From the notes underneath that part of the datasheet:
Fig. 11:
From this, you can see that for 80% duty cycle (Duty factor, D = 0.8) we are beyond the scope of the graph (it only covers D <= 0.5). For that reason, you will need to work within the continuous rated current of the device.
For duty cycles <= 50%, you can read off the transient thermal impedance reduction for short pulses & low duty cycle, add in the impact of the case-to-ambient conditions and then ensure that the junction temperature stays below the absolute maximum rating for your power dissipation.
That said, I would just work well within the continuous current rating of the device and in fact overrate it by a significant margin to ensure that the circuit you design is robust in a wide variety of conditions.