R classroom | PMDE packaged real machine evaluation

Circuit diagram and PCB layout

The LED drive circuit (DC-DC part) on BD81A44EFV-M evaluation board is shown below. The LED driver controls the output current through a voltage up and voltage down DCDC converter. In this circuit, diodes D1 and D2 use PMDE to package SBD products RBR2VWM40ATF , and PMDU packaged SBD products RBR2MM40ATF Compare. The internal components of these two SBDs are the same, but the packaging is different.

LED driver circuit in BD81A44EFV-M evaluation board

(DC-DC part) and diodes D1, D2

In addition, the PCB layout of the evaluation board is also given below. The evaluation board has 4 layers in total. The thickness of copper foil on the surface and the fourth layer (back) is 70 μ m, and that of the second and third layers is 35 μ m. The pattern of the first layer is as shown in the figure, and the second, third and fourth layers are 74.2 μ m square patterns. Diodes D1 and D2 are installed in the pink area.

RBR2VWM40ATF (PMDE) and RBR2MM40ATF (PMDU) are respectively installed at this position and compared and evaluated.

PCB layout of BD81A44EFV-M evaluation board

Comparison of fever

The following is the thermal imaging results (package temperature Tc) of PMDU and PMDE when running on the evaluation board.

Compare Tc by evaluating the thermal imaging images of PMDE and PMDU on the board

The results show that the Tc difference between PMDE and PMDU is very small. The temperature difference at the step-down side is △ Tc (D1)=1.7 ℃, and the temperature difference at the step-up side is △ Tc (D2)=1.2 ℃. Although the size of PMDE package is smaller, by effectively cooling the circuit board, PMDE package can restrain the package temperature Tc at the same level as PMDU package.

Efficiency comparison

From the efficiency comparison results, it can be seen that the peak efficiency η peak (PMDE) of PMDE is 88.6%, and the η peak (PMDU) of PMDU is 88.7%, which are almost the same. Since the internal components of the SBD used are the same (each temperature coefficient is the same), it can be inferred that the component temperature Tj is also the same. That is to say, under the conditions of this assessment, although the PMDE package is smaller than the previous PMDU package size, it has achieved the same heat dissipation performance as the PMDU, and the risk of thermal runaway can be controlled at the same level.

Comparison of PMDE and PMDU efficiency of SBD on evaluation board