Abnormality detection apparatus

An abnormality detection apparatus, comprising:

• a control unit configured to cause an upper arm element and a lower arm element to perform complementary switching operations in an inverter in which the upper arm element and the lower arm element of multiple phases are bridge-connected;
• a monitoring voltage output unit configured to output a monitoring voltage that has a positive correlation with current flowing through a shunt resistor connected in series with the upper arm element and the lower arm element of each phase;
• and
• a monitoring circuit configured to monitor an inverter overcurrent abnormality due to an upper arm element or a lower arm element of one or more phases being stuck in an ON state based on the monitoring voltage during operation of the inverter,
• wherein
• the monitoring voltage output unit holds an output state of the monitoring voltage for a predetermined hold time from input of a trigger signal,
• the monitoring circuit includes
• a comparator configured to output an overcurrent flag of a pulse signal when the monitoring voltage is larger than a reference value, and
• a determination unit configured to determine that an inverter overcurrent is abnormal and stop energization of the inverter, when a cumulative output time of the overcurrent flag of at least one phase reaches a time threshold, and
• the determination unit determines that there is the inverter overcurrent abnormality at the earliest timing of when a cumulative output time of the overcurrent flag reaches the time threshold for at least one phase, or when number of outputs of the overcurrent flag reaches a number threshold.