Combined bipolar and MOSFET switch
First Claim
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1. An electronic switch, comprising:
- (a) a bipolar transistor having collector, emitter and base terminals, one of said collector and emitter terminals being connectable through a load to a voltage source;
(b) a first MOSFET transistor having source, drain and gate terminals, one of said source and drain terminals thereof being connected to the other of said emitter and collector terminals of said bipolar transistor;
(c) a second MOSFET transistor having source, drain and gate terminals, one of said source and drain terminals thereof being connectable through said load to said voltage source;
(d) a threshold element having at least two terminals, one of said two terminals being connected to the other of said source and drain terminals of said second MOSFET transistor and the other of said two terminals being connected to the other of said source and drain terminals of said first MOSFET transistor;
the threshold element for defining a threshold voltage for operating the bipolar transistor;
(e) input means connected to said gate terminals of said first and second MOSFET transistors for coupling a control signal to said gate terminals of said first and second MOSFET transistors; and
(f) means connecting said one terminal of said threshold element to said base terminal of said bipolar transistor.
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Abstract
Power MOSFETs for switching high voltages have a relatively high on-state DC resistance. The invention provides for the connection in series of a low voltage MOSFET with a higher voltage bipolar transistor. This series circuit is connected in parallel with a series circuit consisting of another MOSFET and a threshold switch. The threshold switch is placed between the base terminal and the free terminal of the low voltage MOSFET. The MOSFETs receive a joint control signal (u1) which is routed to the low voltage MOSFET. In the case of an inductive load with recovery operation, the signal is routed through a delay element that becomes active when the circuit is turned on.
61 Citations
17 Claims
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1. An electronic switch, comprising:
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(a) a bipolar transistor having collector, emitter and base terminals, one of said collector and emitter terminals being connectable through a load to a voltage source; (b) a first MOSFET transistor having source, drain and gate terminals, one of said source and drain terminals thereof being connected to the other of said emitter and collector terminals of said bipolar transistor; (c) a second MOSFET transistor having source, drain and gate terminals, one of said source and drain terminals thereof being connectable through said load to said voltage source; (d) a threshold element having at least two terminals, one of said two terminals being connected to the other of said source and drain terminals of said second MOSFET transistor and the other of said two terminals being connected to the other of said source and drain terminals of said first MOSFET transistor;
the threshold element for defining a threshold voltage for operating the bipolar transistor;(e) input means connected to said gate terminals of said first and second MOSFET transistors for coupling a control signal to said gate terminals of said first and second MOSFET transistors; and (f) means connecting said one terminal of said threshold element to said base terminal of said bipolar transistor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In an electronic switch having a first MOSFET and at least one bipolar transistor, in which the collector-emitter section of the bipolar transistor and the drain-source section of the first MOSFET are connected in series to form a first series circuit, the improvement comprised in that:
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(a) said bipolar transistor is a Darlington amplifier comprising an input and an output bipolar transistor and the drain-source section of the first MOSFET is connected in series to the collector-emitter section of the output bipolar transistor of said Darlington amplifier; (b) a second series circuit comprising a second MOSFET and a threshold element is connected in parallel with the first series circuit of said bipolar transistor and said first MOSFET, said first and second series circuits being connectable in parallel through a load to a source of voltage; (c) said threshold element is connected between first MOSFET that is not connected to the output bipolar transistor; and (d) a control signal is routed to the gate terminals of said first MOSFET and said second MOSFET. - View Dependent Claims (8)
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9. A switching circuit for an inductive load energized from a d-c source, said switching circuit comprising:
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a bipolar transistor having first and second power electrodes and a control electrode; a first field effect transistor (FET) having first and second power electrodes and a gate electrode; means for connecting the power electrodes of the bipolar transistor and the first FET serially with the load cross the d-c source; a second FET having first and second power electrodes and a gate electrode, said first and second power electrodes being connected between the first power electrode and the control electrode of the bipolar transistor; gate drive means connected to the gate electrodes of both FETs and providing rectangular voltage pulses thereto, the FETs being in a conductive stage during the existence of any positive rectangular pulse whereby load current passes through the load, the bipolar transistor and the first FET, the second FET applying a control signal to the control electrode of the bipolar transistor. - View Dependent Claims (10, 11, 12)
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13. A switching circuit for an inductive load energized from a d-c source and comprising:
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a bipolar transistor having collector base and emitter electrodes, the collector electrode connected to a first polarity of the d-c source by means of the inductive load; a first switch connected between the emitter electrode of the bipolar transistor and a second polarity of the d-c source; a second switch connected between the inductive load and the base electrode of the bipolar transistor; means for simultaneously closing or opening said first and second switches in accordance with current requirements of the load, the closing of the first switch providing a load current path from the emitter of the bipolar transistor to the second polarity of the d-c source, the closing of said second switch providing current to the base electrode of the bipolar transistor causing it to switch on, the opening of said switches establishing an emitter open condition on the bipolar transistor and elimination of its base current drive to render it non-conducting. - View Dependent Claims (14, 15, 16, 17)
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Specification