Wolfspeed SPEEDVAL KIT HALF-BRIDGE MOD-MB-HB-0900V-40A User Manual page 25

The motherboard contains an interlock circuit to prevent accidentally commanding a shoot-
through, which can occur if both PWM signals are high. This would turn on both MOSFETs at the
same time, resulting in extremely high currents through the MOSFETs by effectively shorting out
the DC bus. The circuit in Figure 19 sets both LS-PWM and HS-PWM signals low if the incoming
signals are both high, preventing the two MOSFETs from being gated on at the same time. If you
want to test the short-circuit protection of the gate driver to protect against this condition, you
will need to remove U4 and U9 and install R9 and R49 to bypass the interlock circuit. There may
be additional interlocking on the gate driver card that would need to be bypassed as well to
allow for overlapping PWM signals.
Note that this should only be done when using a gate driver that provides short-circuit
protection. The short-circuit protection on the gate driver cards may require tuning of the trip
level and timing in order to provide adequate protection of the SiC MOSFETs during a short-
circuit test. It is highly recommended to start this testing at a low voltage (approximately 100-
200 V) and verify proper functionality before increasing the bus voltage to reduce the possibility
of damage to the board or devices. The-short circuit protection should be tuned to provide turn-
off of the MOSFET such that the total duration of the short-circuit current is approximately 1us or
less.
PRD-06829 REV. 1, December 2022
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SpeedVal Kit™ and Wolfspeed logo is a trademark of Wolfspeed, Inc. Other trademarks, product and company names
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sponsorship or association.
F 19: PWM I
IGURE NTERLOCK
SpeedVal Kit™ Half-Bridge User Guide
C
IRCUIT
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