Failure detection device for power circuit including switching element
AssigneeMitsubishi Electric Corporation
InventorTakeshi Omaru
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Abstract
A failure detection device detects the voltage across the main electrodes of an IGBT via a diode. The failure detection device determines occurrence of short-circuit failure in the IGBT when the anode voltage of the diode is lower than a first predetermined reference voltage. Determination can be made, excluding the case of a proper operation corresponding to a flywheel diode in an ON state, preferably together with the condition that the anode voltage of the diode is higher than a second predetermined reference voltage.
Claims9
A failure detection device for a power circuit including a switching element having a main current flowing from a first main electrode to a second main electrode altered according to a control signal, said failure detection device comprising:
- a first rectifying element having a cathode connected to said first main electrode,
- a first resistance element having one end connected to an anode of said first rectifying element, and having the other end to which a voltage positive to said second main electrode is applied, and
- a failure determination unit determining whether a failure determination condition to detect failure in said switching element is satisfied or not, wherein
- said failure determination condition includes a condition that a monitor voltage between the anode of said first rectifying element and said second main electrode is lower than a first reference voltage that is determined in advance,
- said first reference voltage is set to a voltage lower than a sum of a voltage across the first and second main electrodes of said switching element at an ON state and a forward voltage of said first rectifying element, and higher than the forward voltage of said first rectifying element.
A failure detection device for a power circuit including a switching element having a main current flowing from a first main electrode to a second main electrode altered according to a control signal, said failure detection device comprising:
- a first rectifying element having a cathode connected to said first main electrode,
- a first resistance element having one end connected to an anode of said first rectifying element, and having the other end to which a voltage positive to said second main electrode is applied, and
- a degradation determination unit to determine degradation in said switching element, wherein
- said degradation determination unit detects a monitor voltage between the anode of said first rectifying element and said second main electrode to determine whether said detected monitor voltage exceeds a third reference voltage determined in advance when a level of said main current matches a predetermined reference current,
- said reference current is set to a level where the level of said main current corresponds to a boundary between a first region and a second region,
- said first region is a region where a voltage across said first and second main electrodes of said switching element has a negative temperature dependency, and
- said second region is a region where a voltage across said first and second main electrodes of said switching element has a positive temperature dependency.
Dependencies are inferred from the claim text.