Incremental base drive circuit for a power transistor
First Claim
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1. A base drive circuit for a power transistor having base, collector and emitter elements and a load circuit connected in series with the collector and emitter elements, comprising:
- a source of control signal which represents an operating current level of said transistor wherein said control signal is a digital signal;
a plurality of discrete current sources for providing increments of base current to the base element of said transistor; and
means responsive to said control signal for connecting a controlled number of said discrete current sources with the base element of said transistor to provide the desired base current dependent on the operating current level.
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Abstract
A base drive circuit for a power transistor includes a plurality of discrete current sources. A condition of the power transistor circuit, which is a function of the transistor current, is sensed and controls the number of discrete current sources that are activated.
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Citations
10 Claims
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1. A base drive circuit for a power transistor having base, collector and emitter elements and a load circuit connected in series with the collector and emitter elements, comprising:
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a source of control signal which represents an operating current level of said transistor wherein said control signal is a digital signal; a plurality of discrete current sources for providing increments of base current to the base element of said transistor; and means responsive to said control signal for connecting a controlled number of said discrete current sources with the base element of said transistor to provide the desired base current dependent on the operating current level. - View Dependent Claims (2, 3, 4)
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5. A base drive circuit for a power transistor having base, collector and emitter elements and a load circuit connected in series with the collector and emitter elements, comprising:
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a source of analog control signal representing an operating current level of said transistor; a plurality of discrete current sources providing increments of base current to the base element of said transistor; and means responsive to said control signal for connecting a controlled number of said discrete current sources with the base element of said transistor to provide the desired base current dependent on the operating current level; wherein the connecting means includes a plurality of threshold detectors each having an input responsive to said control signal and a different current level threshold, a discrete current source being responsive to each threshold detector. - View Dependent Claims (6, 7)
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8. A base drive circuit for a power transistor having base, collector and emitter elements in a load circuit connected in series with the collector and emitter elements, comprising:
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a source of analog control signal representing an operating current level of said transistor; a source of on-off signal for the transistor; a first discrete current source responsive to said on-off signal to provide a first increment of base drive current to said transistor; a threshold detector responsive to said control signal, connected with a second discrete current source to provide a second increment of base current to said transistor; an AND gate having inputs connected with the on-off signal source and with the threshold detector and an output connected with said second discrete current source; and means responsive to said control signal for connecting a controlled number of said discrete current sources with the base element of said transistor to provide the desired base current dependent on the operating current level. - View Dependent Claims (9)
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10. A base drive circuit for a power transistor having base, collector and emitter elements and a load circuit connected in series with the collector and emitter elements, comprising:
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a source of analog control signal derived from the collector-emitter voltage of the transistor; a source of on-off signal for the transistor; a first discrete current source responsive to said on-off signal to provide a first increment of base drive current to said transistor; a threshold detector responsive to said control signal, connected with a second discrete current source to provide a second increment of base drive current to said transistor; an AND gate having inputs connected with the on-off signal source and with the threshold detector and an output connected with said discrete current source; a latch circuit having an output connected with said AND gate, a SET input connected with the threshold detector and a RESET input connected with said on-off signal source; and means responsive to said control signal for connecting a controlled number of said discrete current sources with the base element of said transistor to provide the desired base current dependent on the operating current level.
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Specification