Current-sensing circuit for an IC power semiconductor device
First Claim
1. A current-sensing circuit for sensing an output current of a power semiconductor arrangement of the type having a semiconductor body including a first and a second current-carrying section each containing at least one basic semiconductor element, wherein the first current-carrying section is arranged to carry a significantly higher current than the second current-carrying section and the first and second current-carrying sections have a common anode, respective control electrodes interconnected to a signal input terminal, and a separate first and second cathode, respectively, a voltage impression device connected to the first cathode which impresses a voltage of the first cathode on the second cathode, and an output terminal of the circuit coupled to said first cathode.
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Abstract
A circuit for measuring the current through a power transistor comprising at least two groups of parallel-switched transistors. A first large group of transistors carries the power current and a second group of transistors carries a current to be measured which is proportional to the power current when the base-emitter voltage or the gate-source voltage (in the case of bipolar or field effect transistors) of all the transistors in the groups is the same. The voltage difference between the parallel-switched emitters or sources of the two groups is measured by means of a differential amplifier and the emitter or source voltage of the first group is impressed on the emitters or sources of the second group by means of a control transistor driven by the differential amplifier. Except in extreme cases (for example, a short-circuit) the current to be measured through the second group follows the power current through the first group on a proportional basis.
103 Citations
24 Claims
- 1. A current-sensing circuit for sensing an output current of a power semiconductor arrangement of the type having a semiconductor body including a first and a second current-carrying section each containing at least one basic semiconductor element, wherein the first current-carrying section is arranged to carry a significantly higher current than the second current-carrying section and the first and second current-carrying sections have a common anode, respective control electrodes interconnected to a signal input terminal, and a separate first and second cathode, respectively, a voltage impression device connected to the first cathode which impresses a voltage of the first cathode on the second cathode, and an output terminal of the circuit coupled to said first cathode.
- 20. A circuit for indicating an output current of a power semiconductor device that includes a body of semiconductor material having first and second sections wherein the first section includes at least one transistor and the second section includes at least one further transistor, said sections being arranged so that the at least one transistor of the first section carries a substantially higher level of current than the at least one further transistor of the second section, first and second terminals for connection to a source of supply voltage for the power semiconductor device, means coupling a first main electrode of sad one and said one further transistors of said first and second sections to the first supply terminal, a signal control input terminal coupled to control electrodes of the at least one transistor and the one further transistor, a voltage coupling device including a control transistor connected in series with said one further transistor of the second section between said first and second supply terminals, said voltage coupling device further comprising means having an input coupled to second main electrodes of the transistors of said first and second sections and an output coupled to a control electrode of the control transistor for maintaining drive voltages between control elctrodes and second main electrodes of the ransistors of the first and second sections equal to one another whereby a current in the control transistor is proportional to a current in said at least one transistor of the first section, and an output terminal of the circuit connected to the second main electrode of the one transistor of the first section.
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24. A current-sensing circuit for sensing an output current of a power semiconductor arrangement of the type having a semiconductor body including a first and second current-carrying section each containing at least one basic semiconductor element, wherein the first current-carrying section is arranged to carry a significantly higher current than the second current carrying section and the first and second current-carrying sections have a common anode coupled to one terminal of a DC supply voltage, interconnected control electrodes coupled to a signal input terminal, and separate first and second cathodes, and a feedback circuit coupled to the first and second cathodes, said feedback circuit including a control transistor for maintaining a voltage on the second cathode equal to a voltage on the first cathode and further connected so that current flowing in the control transistor is equal to a current in the second current-carrying section with each said current being proportional to but significantly less than current in the first current-carrying section, and a current sensing terminal coupled to a main electrode of the control transistor.
Specification