AN3401

Application information

Doc ID 018842 Rev 1

9/18

5

Application information

Typically, standard panels are split into three different cell groups (strings) and each one

needs a bypass device.

In order to test the devices, such as they are already used in the field application, a

dedicated PCB has been realized. Its size is suitable for many junction box dimensions, with

three separated heat sinkers for each bypass device, and thermal vias through the two

layers. Layer thickness is 35 µm.

The PCB image is shown in Figure 4 and the sizes for the 3 heat sinkers are:

Right --> 10.5 cm

2

Different characterizations have been carried out in order to evaluate the device

performance in terms of current capabilities, heat power dissipation, and average voltage

drop, in four different operative conditions.

1.

Device only, without any heat sinker @ oven temperature.

2.

Just one device soldered on the PCB @ ambient temperature.

3.

Three devices soldered on the PCB, at the temperature defined by IEC 61215

procedures (@ 85 °C).

4.

The same as point 3 but at a different temperature (105 °C, to emulate the temperature

inside a junction box when ambient temperature is 85 °C).

This analysis tries to evaluate the thermal performance of all devices in the conditions

mentioned above. But note that the performances are strictly related to the PCB design.

Also, performances can be affected by how the PCB is placed inside the junction box, and

by the junction box material itself. Each of these elements can create an important

bottleneck in the correct heat dissipation that must be guaranteed for every device used in

this application field.

Figure 8.

Typical junction box PCB to solder and connect the devices on PANEL