Dual-monitoring protection circuit for switching transistor
AssigneeReliance Electric Company
InventorsMiroslav Glogolja, Arthur A. Baumgarten
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Abstract
A transistor having a selectively saturated emitter collector path is protected. The emitter collector voltage level is sensed as being greater than a predetermined level to indicate saturation as is the presence and absence of drive current to the base. In response to the transistor not being activated to saturation while the drive current is applied to the base, a fault indication is derived. In response to the fault being indicated, the transistor is prevented from conducting by decoupling a source of operating voltage and current from the emitter collector path and/or decoupling the drive current from the base.
Claims17
Apparatus for monitoring a fault in a main current conducting path of a transistor activated into saturation between first and second opposite electrodes of the path in response to a drive current applied to a control electrode of the transistor, the fault occurring with the drive current being applied to the control electrode while the transistor is not in saturation, comprising first sensing means for detecting that the transistor is and is not activated to saturation, second sensing means for detecting the presence of drive current to the control electrode, and means responsive to the first and second sensing means for indicating a fault in response to the first sensing means detecting that the transistor is not activated to saturation while the second sensing means detects the presence of the drive current.
Apparatus for protecting against a fault in a main current conducting path of a transistor activated into saturation between first and second opposite electrodes of the path in response to a drive current applied to a control electrode of the transistor, the fault occurring with the drive current being applied to the control electrode while the transistor is not in saturation, comprising first sensing means for detecting that the transistor is and is not activated to saturation, second sensing means for detecting the presence of drive current to the control electrode, and means responsive to the first and second sensing means for preventing conduction of the transistor main current path in response to the first sensing means detecting that the transistor is not activated to saturation while the second sensing means detects the presence of the drive current.
A method of protecting against a fault in a main current conducting path of a transistor activated into saturation between first and second opposite electrodes of the path in response to a drive current applied to a control electrode of the transistor, the fault occurring with drive current being applied to the control electrode while the transistor is not in saturation, comprising:
- preventing conduction of the transistor main current path in response to the transistor not being activated to saturation while drive current is being applied to the control electrode by decoupling from the main current conducting path a source of operating voltage and current normally applied to the main current conducting path.
Dependencies are inferred from the claim text.