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Appendix A
In regard of the blooming EV, the test application for high power battery has become more
and more. However, since it is to test the battery with high power and voltage, it is
necessary to pay more attention to the application safety.
According to the RMA data, the damage part is MOSFET mainly for large power, high
voltage Electronic Load to be repaired in general and the most possible cause is over
voltage between the connection of MOSFET and UUT. It may be just a transient, but it could
cause the MOSFET to be damaged by a little energy if it exceeds the maximum voltage.
Common battery application often forms high voltage by paralleling multiple batteries to
avoid the transmission lost caused by low voltage high current. As the switch is uses directly
to connect the battery and applied object, the study shows it is the main cause of LOAD
damage. Figure A-1 shows the wire connection of Electronic Load & Battery. When the
switch is shorted same as inputting a pulse signal, the effect caused by the stray element on
the circuit (series inductance and parallel capacitance resonance) will generate a transient
high voltage to damage the MOSFET and cause short circuit explosion as the simulation
shows in Figure A-2. It can be seen that it will generate the Spike exceeding the previous
setting when the switch effects and it may beyond the IC maximum withstand voltage.
Figure A-1 Wire Connection of Electronic Load & Battery
The figure below shows the simulated circuit diagram of the application that causes damage.
Precautions for Loading
Battery
+LD
Switch
MOSFET
Capacitance
R
-LD
Appendix A Precautions for Loading Battery
Inductance
Effect
Battery
A-1
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