US3906310A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Protective circuit for a main transistor in a monolithic integrated circuit
Assignee: Sony Corp
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Filing: 1973-10-15
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Granted: 1975-09-16
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Expires: 1993-10-15
Abstract
Abstract A protective circuit for a power or other main transistor in a monolithic integrated circuit is provided which gives protection for any potentially destrucive rise in temperature of such transistor. A temperature sensing Zener diode and one or more normal diodes are located in the same substrate and in position where they are directly subject to any rise in temperature of the main transistor. Through a particular circuit arrangement, the main transistor will be turned off when its temperature rises a predetermined value below its destructive value. This is accomplished by utilizing a circuit in which as the temperature of the Zener diode rises the voltage across the Zener diode rises due to its positive temperature coefficient and voltage across the ordinary diode decreases due to its negative temperature coefficient. The Zener diode and the normal diode are connected in a circuit in which the two diodes, one having a positive coefficient and the other have a negative temperature coefficient, acting together provide a control voltage which modifies the base bias of the main transistor to cut off the main transistor when the temperature of the main transistor reaches a predetermined point, such for example as about 160*C. The protective circuit of the present invention is particular useful in combination with a circuit which provides protection against excessive load current in the output of the main transistor, such as might be caused by a short circuit. It is also useful in combination with a voltage controlled circuit.
Inventors
- 👤 Tadashi Esashika
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:10
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/20; H02H7/205; G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/56; G05F1/565; G05F1/569; G05F1/573; H02H5/00; H02H5/04; H02H5/044; H10; H10D; H10D89/00; H10D89/10; H10D89/105
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
168 words
A protective circuit for a voltage controlled power transistor comprising differential amplifier, means connected to said power transistor to maintain a constant output voltage, overload detecting means connected to output circuit of said power transistor, means connected to said overload detecting, means for biasing said power transistor to cut-off when an overload occurs, a control transistor having a base and an emitter, temperature sensing means for detecting the temperature of the power transistor body, said temperature sensing means including a Zener diode and a forwardly bias normal diode connected in a circuit with each other, means for connecting said base and emitter to one electrode of said Zener and normal diode, respectively, and means for taking a voltage from the Zener diode-normal diode circuit to modify the bias of said control transistor and said power transistor to cut off when the temperature thereof reaches a predetermined point, the circuit of said overload detecting means and the circuit of said temperature sensing means having at least portions in common.
Claim 2
Dependent Claim
168 words
A protective circuit for a voltage controlled power transistor comprising differential amplifier, means connected to said power transistor to maintain a constant output voltage, overload detecting means connected to output circuit of said power transistor, means connected to said overload detecting, means for biasing said power transistor to cut-off when an overload occurs, a control transistor having a base and an emitter, temperature sensing means for detecting the temperature of the power transistor body, said temperature sensing means including a Zener diode and a forwardly bias normal diode connected in a circuit with each other, means for connecting said base and emitter to one electrode of said Zener and normal diode, respectively, and means for taking a voltage from the Zener diode-normal diode circuit to modify the bias of said control transistor and said power transistor to cut off when the temperature thereof reaches a predetermined point, the circuit of said overload detecting means and the circuit of said temperature sensing means having at least portions in common.
Claim 3
Dependent Claim
27 words
A protective circuit according to claim 1 which said Zener diode and said normal diode are subjected to substantially the same temperature conditions as said power transistor.
Claim 4
Dependent Claim
118 words
A protective circuit for power transistor comprising a Zener diode and first resistor connected in series across the input of said power transistor, a second transistor to detect variations in said Zener diode, a plurality of serially connected forwardly biased diodes connected to the output of said second transistor, a plurality of serially connected bleeder resistors connected to the cathode end of said serially connected diodes and to a reference potential, a third transistor is connected to an intermediate point of the serially connected bleeder resistors, circuit means for deriving a voltage from said third transistor which connects with base of said power transistor to render said power transistor non-conductive when its body temperature reaches a predetermined point.
Claim 5
Dependent Claim
118 words
A protective circuit for power transistor comprising a Zener diode and first resistor connected in series across the input of said power transistor, a second transistor to detect variations in said Zener diode, a plurality of serially connected forwardly biased diodes connected to the output of said second transistor, a plurality of serially connected bleeder resistors connected to the cathode end of said serially connected diodes and to a reference potential, a third transistor is connected to an intermediate point of the serially connected bleeder resistors, circuit means for deriving a voltage from said third transistor which connects with base of said power transistor to render said power transistor non-conductive when its body temperature reaches a predetermined point.
Claim 6
Dependent Claim
93 words
A monolithic integrated circuit comprising a main transistor, a control transistor having base and emitter, a reversely biased first diode having positive voltage temperature coefficient, a forwardly biased second diode having negative voltage temperature coefficient, said diodes being thermally related with said main transistor, means for connecting said base and said emitter to one electrode of said first and said second diode respectively, means for connecting the other electrodes of said first and said second diode, and means for rendering said main transistor non-conductive when the emitter current of said control transistor increases.
Claim 7
Dependent Claim
93 words
A monolithic integrated circuit comprising a main transistor, a control transistor having base and emitter, a reversely biased first diode having positive voltage temperature coefficient, a forwardly biased second diode having negative voltage temperature coefficient, said diodes being thermally related with said main transistor, means for connecting said base and said emitter to one electrode of said first and said second diode respectively, means for connecting the other electrodes of said first and said second diode, and means for rendering said main transistor non-conductive when the emitter current of said control transistor increases.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-15 | 1979-03-17 | 1979-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-15 | 1983-03-17 | 1983-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-15 | 1987-03-17 | 1987-09-16 | $7700.00 | Window Closed / Lapsed |