The switching component must be suitably cooled so that the junction temperature does not exceed the values specified : usually 125 or 150°C (this value depends on the power components) and so that the temperature of the heatsink does not exceed 90 or 100°C.
The heatsink can be determined either by calculation (see technical note - pages 4 to 6) or directly from the curves provided by celduc.
How to use thermal curves from our technical data-sheets ?
The type of heatsink to be used can be determined directly according to the switched currrent and the ambient temperature.
Example Ieff = 6 A and ambiant temperature max = 38°C
Operating mode of the above curves :
1- identify the current to be switched on the abscissa of the left hand curve
2- plot a vertical line from this point up to the curve (1)
3- from the point obtained, a horizontal line is plotted to the right hand curve (2)
4- identify the ambient temperature on the abscissa of the right hand curve
5- plot a vertical line from this point until you meet the horizontal line previously plotted (3)
6- this point determines the type of heatsink to the used
7- choose the heatsink corresponding to the curve located above this point. In this example 1,2°/W (4)
You can see that with a heatsink of 1,2°/W and 6A, the ambient temperature should not exceed 54°C (8) (9)
And with a heatsink of 1,2°/W and an ambient temperature of 38°C the maximum current could reach 8A (5) (6) (7)
To have access to our complete range of heatsinks - click here
To be also consulted :
Thermal Pads or Thermal Paste – Differences and Advantages