Schaltverluste von Wide-Bandgap Halbleitern messen

Schaltverluste von Wide-Bandgap Halbleitern messen? Ohne zusätzliche Parasiten unter realen Bedingungen?

Klassische Methoden Schaltverluste zu messen, wie der Doppelpuls, verwenden die Messung des Stromes durch den Halbleiter und dessen Spannungsabfall im Schaltmoment. Die parasitären Effekte der Messgeräte beeinflussen die Messungen negativ, sodass die angezeigten Schaltverluste nicht der Realität entsprechen.

Für die Lösung des Problems wurden verschiedene Messmethoden entwickelt, die Schaltverluste passiv unter realen Arbeitsbedingungen messen. Die Schaltverluste können bestimmt werden für verschiedene Spannungen, Ströme und Temperaturen. Die Schaltzelle muss nicht modifiziert werden, sodass voll integrierte Module vermessen werden können.

Direkte Schaltverlustmessung:

In switching cell measurement (classic double pulse) for GaN and SiC
Commutation loop current measurement
Low additional inductance of 300 pH
Bandwidth of 500 MHz
High resolution control signal
Up to 4 gate signals
Configuration script
Pulse and dead time resolution of 250 ps
Coil for measurement purposes
Calibrated up to 100 MHz
Low stray field due to toroid shape
Low HF losses due to litz wire
Pulse resistant up to 150 A because no magnetic material is used
U_DC = 600 V
I_L = 20 A
L = 7 uH
dU/dt = 70 V/ns --> 600 V in 8.5 ns !!!
dI/dt = 18 A/ns

Indirekte Schaltverlustmessung:

Measuring switching losses under real working conditions without commutation loop current measurement
This measurement method does not add parasitics to the switching cell and does not influence the switching behavior
Principle:
Measuring the input power with a high class power analyzer and subtract the known losses of the inductor
Measuring short period of time to reduce the thermal influence (100 ms)
Well known air core inductor with low losses
Very accurate PWM Unit
Forced air cooling of semiconductors and inductor
Features:
Separating turn-on and turn-off losses by different control modes
Zero Voltage switching to measure the switching-off losses
Hard switching mode for measuring switching-on and -off losses
System controlled by software
Software communicates with
Precision power meter
PWM signal timer
Oscilloscope
Power supply
High resolution control signal
Up to 4 gate signals
Pulse and dead time resolution up to 250 ps
Coil for measurement purpose
Calibrated up to 100 MHz
Low stray field due to toroid shape
Low HF losses due to litz wire
Pulse resistant up to 150 A because no magnetic material is used
Inductor losses can be determined precisely due to calculation and impedance measurement

Forschungsschwerpunkte