With Thermistor Patents (Class 361/106)
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Patent number: 6075689Abstract: A device and method for protection of heating, ventilation, and air conditioning (HVAC) control circuits. The device includes a positive temperature coefficient (PTC) member which is a multi-use, non-bulky, element which will reset after tripping without requiring the user to access the device. The device also includes a pair of connective members to provide the external electrical interface for the device, such that the PTC member is disposed between and in electrical contact with the connective members. Each embodiment also includes a protective member covering portions of the PTC member and connective members chosen or formed sufficient to insulate a user from contact with electrical hazard and sufficient to protect the device from electrical and physical contact which would affect its performance or the performance of the HVAC control circuit to be protected.Type: GrantFiled: August 21, 1998Date of Patent: June 13, 2000Inventor: Dennis Mitchell
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Patent number: 6072679Abstract: An electrical protection system includes a control element of a series combination of a PTC device thermally coupled with a resistive device, and a relay coil coupled with relay contacts. If the relay contacts are open the only way in which they can be closed is by supplying current to the relay coil through a resistance-capacitance network. A diode permits current to pass through the resistance-capacitance network to the relay coil but prevents current from flowing in the opposite direction thereby preventing relay contact chatter, contact fusing, and potential relay catastrophic failure.Type: GrantFiled: March 23, 1999Date of Patent: June 6, 2000Inventor: Inho Myong
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Patent number: 6072681Abstract: The present invention provides a simple, low cost power line protection device and method suitable for protecting data bus and power lines such as in the USB (Universal Serial Bus) configurations and other power management circuits. In one embodiment of the invention, an improved protection device, controllable by a control circuit, for protecting a power line is provided. The device includes a switch for switching on and off power supplied on the power line, and a detector for detecting a fault condition, such as an overload condition, on the power line. The detector includes a positive temperature coefficient (PTC) resistor thermally coupled to the switch for causing the fault condition to be reported to the control circuit. In this way, when a fault condition occurs, the control circuit activates the switch to switch off power supplied on the power line.Type: GrantFiled: August 3, 1998Date of Patent: June 6, 2000Inventors: Adrian I. Cogan, Ram G. Bommakanti
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Patent number: 6040972Abstract: A protection device for a communication system is inserted between a circuit side and a subscriber side and includes a protection circuit part and trimmable resistors. The protection circuit part includes a tip line and a ring line each extending between an input terminal and an output terminal. The tip line and the ring line each contain at least one thermistor with positive temperature characteristic or one protection resistor as overcurrent-protecting element. The output terminals of the tip line and the ring lines are connected, say, by a diode bridge of which one terminal is grounded and another terminal connected to a power source. Trimmable resistors are each connected to a corresponding one of the output terminals of the protection circuit part and are adapted to be trimmed such that impedance imbalance between the tip and ring lines can be reduced.Type: GrantFiled: October 10, 1997Date of Patent: March 21, 2000Assignee: Murata Manufacturing Co., Ltd.Inventor: Haruyuki Takeuchi
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Patent number: 6028470Abstract: An integrated circuit comprising a power transistor and a circuit arrangement. The circuit arrangement is thermally coupled to the power transistor and operates in a temperature-dependent fashion. The integrated circuit includes a pnp or npn transistor with a temperature dependent resistor coupled between the base and emitter of the transistor. The off-state current of the transistor changes as a function of temperature and initiates a change in a base current of the power transistor.Type: GrantFiled: October 14, 1997Date of Patent: February 22, 2000Assignee: Robert Bosch GmbHInventors: Hartmut Michel, Christian Pluntke
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Patent number: 6023402Abstract: A control circuit for the regulation of fan speed control in a computer power supply with software controlled shutdown and automatic restart for over-temperature protection. The control circuit overrides the control inputs when the temperature inputs indicate a temperature above a specific level.Type: GrantFiled: February 11, 1998Date of Patent: February 8, 2000Assignee: Compact Computer CorporationInventor: George A. Kaminski
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Patent number: 6023403Abstract: The present invention is a device for protecting an electrical circuit. The device includes a resistive element having a first and a second surface. A first electrode is in electrical contact with the first surface of the resistive element and a second electrode is in electrical contact with the second surface of the resistive element. A first end termination electrically connects the circuit and the first electrode. A second end termination electrically connects the second electrode and the circuit. An electrically insulating layer is interposed between the first and second end terminations and is in contact with the first and second electrodes. The end terminations allow for an electrical connection to be made to both electrodes from the same side of the electrical device.Type: GrantFiled: November 26, 1997Date of Patent: February 8, 2000Assignee: Littlefuse, Inc.Inventors: Katherine M. McGuire, Honorio Luciano
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Patent number: 6021037Abstract: A device (1) for supplying electric power to a load (4) connected to the device (1) in a power-on mode comprises a driver stage (7), a control unit (9), adapted to supply turn-on pulses to the driver stage (7), and an output stage (12) with a switching transistor (1) which can be driven into its conductive state for a time interval (T.sub.EIN) by the driver stage (7) in the power-on mode when turn-on pulses occur, and which can be driven into its non-conductive state after expiry of the time interval (T.sub.EIN), the driver stage (7) being also adapted to monitor the operating temperature (T.sub.S) of the switching transistor (11) and to activate a power-off mode when the operating temperature (T.sub.S) of the switching transistor (11) exceeds a first limit temperature (T.sub.G1), in which power-off mode the switching transistor (11) is permanently driven into its non-conductive state by the driver stage (7) in spite of the occurrence of turn-on pulses (I.sub.Type: GrantFiled: December 8, 1997Date of Patent: February 1, 2000Assignee: U.S. Philips CorporationInventor: Rudolf Hasler
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Patent number: 5999384Abstract: A circuit protection apparatus employs a PTC element for overload and/or short circuit protection and an arcing fault interruption arrangement. The circuit protection apparatus may be employed in a ground fault receptacle for interrupting the flow of electrical current in a line in response to any of a plurality of different types of fault conditions on the line. The circuit protection apparatus may include a set of contacts connected in series with the line, and having an open position and a closed position, a trip device coupled to the contacts, adapted to be actuated by a trip signal, to move the contacts from the closed position to the open position and an element having a positive temperature coefficient of resistivity (PTC) connected in series with the contacts. The PTC element is connected to the trip device to provide the trip signal to the device in response to overload or short circuit conditions in the line.Type: GrantFiled: August 5, 1998Date of Patent: December 7, 1999Assignee: Square D CompanyInventors: William W. Chen, Andy A. Haun, George D. Gregory, Gary W. Scott
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Patent number: 5991136Abstract: A protector unit for use in retrofitting connector blocks, such as a 300-type connector block or a C-50 frame includes a housing; a back-up, fail-safe assembly for providing a connection to ground; and a positive temperature coefficient limiter ("PTCR") for temporarily preventing the passage of current through the protector unit when an over-current condition is detected and for allowing the passage of current through the protector unit when the over-current condition is no longer detected. The back-up, fail-safe assembly permanently prevents the passage of current through the protector unit when a sustained over-current condition is detected.Type: GrantFiled: December 1, 1997Date of Patent: November 23, 1999Assignee: RELTEC CorporationInventors: Richard T. Kaczmarek, Arnold M. Ladd
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Patent number: 5977862Abstract: A polymer high voltage current limiter comprising, per phase, a fast circuit-breaker pole, a semi-fast protection circuit-breaker pole, and a set of polymer-based elements having very low resistivity, filled with carbon black, and connected in series and in parallel, wherein each element comprises a carbon-filled polymer matrix of elongate shape and including in its interior two parallel metal conductors.Type: GrantFiled: April 25, 1997Date of Patent: November 2, 1999Assignee: GEC Alsthom T & D SAInventor: Van Doan Pham
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Patent number: 5969928Abstract: A method for determining the resistance of a shunt for use with a current limiting device that exhibits PTC characteristics to protect an electrical circuit. The method comprises steps for determining maximum and minimum resistance values based on operating criteria and component characteristics and selecting resistance values that fall within selected ranges.Type: GrantFiled: December 3, 1997Date of Patent: October 19, 1999Assignee: Gould Electronics Inc.Inventors: Masato Hashimoto, William R. Crider, Alan F. Wilkinson, Jr., Robert Wilkins, Arnav Mukherjee
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Patent number: 5939968Abstract: An electrical apparatus comprising first and second PTC elements composed of a polymer composition with conductive particles dispersed therein, an insulating body, and first and second conductive terminals. Flexible conductive members having a first end that can be electrically connected to a source of electrical power and a second end that is adapted to receive and make electrical contact with the apparatus are provided. The PTC element and the insulating body are positioned between the first and second conductive terminals so that when the apparatus is inserted between the flexible conductive members, the members exert a pressure on the insulating body.Type: GrantFiled: September 15, 1998Date of Patent: August 17, 1999Assignee: Littelfuse, Inc.Inventors: Thinh Nguyen, Anthony Minervini
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Patent number: 5933311Abstract: A circuit breaker including a switch having an open and a closed position connected to a line of the circuit breaker. A first actuating device, actuated by a first activating signal, is connected to the switch to move the switch from the closed position to the open position wherein the flow of electric current in the line is interrupted. A positive temperature coefficient resistivity element (PTC element) is tripped at least once wherein the tolerance of the PTC element is reduced and the PTC element is connected to the first actuating device for providing the first activating signal. In another embodiment of the present invention, a second actuating device, actuated by a second activating signal provided by the circuit breaker current, is connected to the switch to move the switch from the closed position to the open position wherein the flow of electric current in the line is interrupted.Type: GrantFiled: April 2, 1998Date of Patent: August 3, 1999Assignee: Square D CompanyInventors: William W. Chen, Brett E. Larson
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Patent number: 5896264Abstract: A current-limiting device comprises at least one polymer-based electrically conducting body with two contact surfaces and at least two electrodes. Close to a first one of the two contact surfaces of the polymer-based electrically conducting body, a surface layer is arranged. The resistivity of the surface layer is reduced relative to the resistivity of the bulk of the polymer body, and at the same time at least the second contact surface of the body is adapted to make free contact with at least one of the electrodes or other electrically conducting body.Type: GrantFiled: October 16, 1997Date of Patent: April 20, 1999Assignee: ABB Research Ltd.Inventors: Maria Bijlenga, Lars Banghammar, Tomas Hansson, Ola Jeppsson
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Patent number: 5892413Abstract: A distribution apparatus is provided which, if a short circuit occurs in a secondary line from a branch output terminal of the apparatus or in terminal equipment connected to the secondary line, stops supplying electric currents to the concerned branch output terminal. In the distribution apparatus, external taps (22) which serve as distribution output terminals are connected to a current passage network (26). A positive thermistor (27) is connected to each external tap (22) in the current passage network (26).Type: GrantFiled: April 10, 1997Date of Patent: April 6, 1999Assignee: Maspro Denkoh, Co., Ltd.Inventor: Kazuyoshi Okimura
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Patent number: 5886860Abstract: A Positive Temperature Coefficient Resistivity (PTC) element has a resistivity that increases as the temperature increases. Circuit breakers having PTC elements can achieve better overload and short circuit protection than existing products. Breakers with PTC elements can also be combined with ground fault detection circuits to activate the circuit breaker under ground fault conditions that are less severe than the overcurrent conditions that would normally activate the circuit breaker. A shunt trip assembly incorporating a PTC resistor reduces the required power rating of the clearing switch.Type: GrantFiled: August 25, 1997Date of Patent: March 23, 1999Assignee: Square D CompanyInventors: William Weizhong Chen, Colin Cornhill, Andy Haun, Gary Scott, Manzoor Ali, William Rezac, Kevin James Green
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Patent number: 5867083Abstract: A small-size high-performance electronic protective device (10) is provided for use in protecting communication equipment including an exchange servicing module against application of abnormal surge current due to accidental shorts between adjacent ones of power feed lines in a communications system. The protective device (10) includes positive thermistors (3a, 3b) connected between communication link input terminals (1a, 1b) and output terminals (1c, 1d) coupled to an associative equipment being protected. The protective device (10) also includes thick-film resistive elements (5a, 5b), which are connected in parallel with the thermistors (3a, 3b), respectively.Type: GrantFiled: June 28, 1996Date of Patent: February 2, 1999Assignee: Murata Manufacturing Co., Ltd.Inventors: Haruyuki Takeuchi, Michio Miyazaki, Tadao Bekku
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Patent number: 5864458Abstract: Electrical circuit protection arrangements with PTC devices and mechanical switches. The combinations of this invention permit the use of mechanical switches and PTC devices to switch voltages and currents in normal circuit operations, wherein the voltage and/or current ratings of the mechanical switches and PTC devices are much less than the normal operating voltages and currents of the circuits. This feature permits the use of smaller and less expensive mechanical switches and PTC device than would otherwise be required in such circuits. The arrangements of switches and PTC devices also permit the PTC devices to limit the magnitude of the fault current passed to the circuit.Type: GrantFiled: November 29, 1995Date of Patent: January 26, 1999Assignee: Raychem CorporationInventors: Hugh Duffy, Justin Chiang, John Midgley
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Patent number: 5862030Abstract: An electrical safety device comprises a sensor strip disposed in the insulation of a wire or in the insulation of a sheath enclosing a bundle of insulated electrical conductors. The sensor strip comprises a distributed overtemperature sensing portion comprising a conductive polymer having a positive temperature coefficient of resistivity which increases with temperature sufficient to result in a switching temperature. A mechanical damage sensing portion comprises a strip disposed in the sheath in a mechanical damage sensing pattern which becomes damaged or open upon mechanical damage of the sheath before the bundle of conductors are damaged. The overtemperature sensing portion and the mechanical damage sensing portion may be the same sensing strip disposed in the sheath and arranged in a helical relationship with a longitudinal axis of the sheath.Type: GrantFiled: June 2, 1998Date of Patent: January 19, 1999Assignee: BPW, Inc.Inventors: Kenneth S. Watkins, Jr., Shelby J. Morris, Jr.
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Patent number: 5852539Abstract: An overheat protection circuit includes a resistor having a first lead connected to the engine temperature switch and the power take off (PTO) relay coil circuit. The second lead of the resistor is connected to the output of an interlock circuit to provide an energizing voltage signal to the PTO relay for operation of the PTO driven attachment when preselected operating conditions are present on the vehicle. If for any reason the engine temperature rises above a preselected maximum operating temperature, the engine temperature switch will close and cause the voltage at the second lead to drop below the minimum operating voltage of the PTO relay. The PTO relay deenergizes to remove drive from the attachment. The PTO cannot be reengaged until the engine operating temperature drops below the maximum operating temperature. The resistor preferably is a positive temperature coefficient thermistor to reduce power dissipation through the circuit while the temperature switch is closed and the PTO relay is deenergized.Type: GrantFiled: June 26, 1996Date of Patent: December 22, 1998Assignee: Deere & CompanyInventor: Rudolph Andrew Peterson, Jr.
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Patent number: 5847436Abstract: A bipolar transistor includes a chip having a base electrode and an emitter electrode on a surface thereof and a film resistor provided on a surface of the chip and electrically connecting the base electrode and the emitter electrode to each other, the film resistor having a negative resistance characteristic with temperature change.Type: GrantFiled: April 29, 1997Date of Patent: December 8, 1998Assignee: Kabushiki Kaisha Tokai Rika Denki SeisakushoInventor: Hitoshi Iwata
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Patent number: 5841617Abstract: An electrical safety device comprises a sensor strip disposed in the insulation of an electrical power cord or other electrical apparatus. The sensor strip is made of a conductive polymer with a positive temperature coefficient of resistivity which increases with temperature. The sensor strip forms a series connected loop connected to an impedance measuring circuit. A relay interrupts current to the conductors of the cord when the impedance of the sensor strip increases due to an overtemperature condition. The sensor strip is positioned between the conductors of the cord and the outside surface of the cord. The position of the sensor strip allows the strip to act as a mechanical damage sensor, opening the series connected loop before an energized conductor is exposed.Type: GrantFiled: April 7, 1997Date of Patent: November 24, 1998Assignee: BPW, Inc.Inventors: Kenneth S. Watkins, Jr., Shelby J. Morris, Jr.
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Patent number: 5835320Abstract: An electronic circuit interrupter is protected against thermal damage upon loosening of the lug connectors that connect the circuit interrupter with the load circuit. Thermal sensing elements attached to the lugs connect with the circuit interrupter trip unit to initiate circuit interruption when the temperature sensed exceeds a predetermined value.Type: GrantFiled: May 28, 1997Date of Patent: November 10, 1998Assignee: General Electric CompanyInventors: Joseph M. Palmieri, George J. Boucher, J. Peter McCuin, Edward E. Kim
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Patent number: 5834921Abstract: A safety device for a portable battery-powered electric apparatus having a battery unit with one or more battery cells for supplying power to electric circuitry in the apparatus. The apparatus is connectable to a charging device for charging the battery unit while maintaining the supply of power to the apparatus. The safety device has a first fuse device connected between the battery unit and a first terminal of the apparatus for receiving charging current from the charging device, and a second fuse device connected between the battery unit and a second terminal of the apparatus for supplying power to electric circuitry in the apparatus. The fuse devices are operatively independent of each other, particularly in that the second fuse device maintains the electric connection between the battery unit and the electric circuitry in the apparatus, even when or if the first fuse device releases or opens in response to an undesired condition in the charging device.Type: GrantFiled: July 1, 1997Date of Patent: November 10, 1998Assignee: Telefonaktiebolaget LM EricssonInventors: Johan Mercke, Bjorn Frannhagen
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Patent number: 5831803Abstract: A circuit protection system employing arrangements of PTC devices and mechanical switches. The PTC device is not involved in the circuit until a fault is sensed. A current sensing relay senses an overcurrent and directs the current to the PTC device. As the voltage across the PTC device increases, a parallel arrangement of voltage sensing relays completes the operation of the protection system, and disconnects the load until the protection system is reset. The protection system may be reset manually or remotely.Type: GrantFiled: June 2, 1997Date of Patent: November 3, 1998Assignee: Raychem CorporationInventors: Craig Wynn, St. Elmo Nickols, III
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Patent number: 5818676Abstract: A self-resetting circuit overcurrent protection device comprises two or more flat positive temperature coefficient (PTC) elements, each comprising a layer of PTC material sandwiched between two metal plates, disposed in a parallel, overlapping configuration and connected in electrical parallel. The resulting circuit protection device has a hold current equal to the sum of the hold currents of the component PTC elements, while having a surface area no greater than that of a PTC device comprising only one of the component PTC elements. In the preferred embodiment of the invention, two PTC elements are used and one of the metal plates belonging to each of the PTC elements has a blade terminal integrally formed therewith, the terminals being substantially identical in configuration to the terminals of a standard automotive fuse which the device is intended to replace.Type: GrantFiled: May 16, 1997Date of Patent: October 6, 1998Assignee: Yazaki CorporationInventor: William Gronowicz, Jr.
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Patent number: 5815351Abstract: In a computer, an overload protection circuit for protecting the computer's power supply from overload over a wide ambient temperature range. The overload protection circuit, which compares two voltage signals in order to shut off the computer power supply when certain limits are exceeded, is implemented without any pots or other trim circuits. Instead, a resistive temperature device is utilized to counter the effects of increasing ambient temperature on the overload protection circuit.Type: GrantFiled: July 21, 1997Date of Patent: September 29, 1998Assignee: Dell Computer CorporationInventors: Gerard Ashok, Fred M. Henegar
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Patent number: 5814791Abstract: An electrical assembly (10) comprising a first electrical device (12) comprised of a non-linear resistant, temperature responsive element (14) and first and second electrodes (16,18), the device (12) being connectable to a first power supply (20) such that a first electrical current (i.sub.1) travels through the resistive element (14) from the first electrode (16) to the second electrode (18). A second electrical circuit (24) is in electrical contact with the electrical device (12) such that the second circuit (24) may introduce a secondary electrical current (i.sub.2) into a localized portion of the non-linear resistant element (14), the second current (i.sub.2), when applied to the non-linear resistant element (14), causes the element (14) to change from a first resistant state to a second resistant state.Type: GrantFiled: June 17, 1997Date of Patent: September 29, 1998Assignee: Littelfuse, Inc.Inventor: Wallace C. Rudd
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Patent number: 5808538Abstract: An electrical apparatus comprising first and second PTC elements composed of a polymer composition with conductive particles dispersed therein, an insulating body, and first and second conductive terminals. Flexible conductive members having a first end that can be electrically connected to a source of electrical power and a second end that is adapted to receive and make electrical contact with the apparatus are provided. The PTC element and the insulating body are positioned between the first and second conductive terminals so that when the apparatus is inserted between the flexible conductive members, the members exert a pressure on the insulating body.Type: GrantFiled: June 19, 1996Date of Patent: September 15, 1998Assignee: Littelfuse, Inc.Inventor: Thinh Nguyen
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Patent number: 5796568Abstract: A reversible short circuit current limiter which has at least one PTC thermistor connected in parallel with a shunt impedance branch, and is connected in series with at least one capacitor or a capacitor bank of the DC intermediate circuit. The short circuit current limiter may be arranged in the DC intermediate circuit or in the current convertor. A diode may be connected in the reverse-bias direction of a short circuit path in parallel with the PTC thermistor. The shunt impedance branch has a varistor connected in series with an ohmic resistor or a PTC thermistor and, if appropriate, an inductor. Structures of metal-based nonblocking PTC thermistors are specified.Type: GrantFiled: March 20, 1997Date of Patent: August 18, 1998Assignee: Asea Brown Boveri AGInventor: Tudor Baiatu
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Patent number: 5796569Abstract: A self-resetting circuit overcurrent protection device suitable for use as a replacement for a conventional cylindrical fuse has at least one semi-tubular positive temperature coefficient (PTC) element surrounded by a tubular, electrically insulating body and connected to terminal caps disposed at either end of the cylinder. In a first embodiment of the invention, first and second PTC elements are disposed such that the concave surfaces thereof are oriented toward one another and are connected in electrical parallel so that the hold current of the PTC device is equal to the sum of the hold current values of each of the two elements. In a second embodiment, a first pair of semi-tubular PTC elements are disposed in nested, concentric relationship to one another and a second pair of semi-tubular PTC elements are disposed in nested, concentric relationship to one another, the two pairs of PTC elements being disposed with concave surfaces thereof facing one another.Type: GrantFiled: June 19, 1997Date of Patent: August 18, 1998Assignee: Yazaki CorporationInventor: William Gronowicz, Jr.
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Patent number: 5793277Abstract: A plurality of supporting columns extend downwardly from a top wall of a cover attached to the electrical junction box body. A case surrounding the PTC element has projecting bars extending in the cover attaching direction. Each of the supporting columns has a guide groove receives the associated projecting bar so as to hold the case. The PTC element joints to connecting terminal strips having a heat radiation face. Further, the connecting terminal strip has a saw-tooth face at each side end thereof.Type: GrantFiled: March 19, 1997Date of Patent: August 11, 1998Assignee: Yazaki CorporationInventors: Yuichiro Ichikawa, Hidenori Yamanashi
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Patent number: 5790363Abstract: An overvoltage/overcurrent protection system for Ethernet networks using unshielded twisted pair cabling, the system comprising two overvoltage/overcurrent protection circuits, one circuit for the twisted pair carrying incoming digital signals and one circuit for the twisted pair carrying outgoing digital signals.Type: GrantFiled: December 3, 1997Date of Patent: August 4, 1998Assignee: TII Industries, Inc.Inventor: Nisar A. Chaudhry
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Patent number: 5790359Abstract: A surge protection device comprising surge protector having a first terminal and a second terminal, one of the terminals being conductively connected to a first power transfer mechanism, such as a source of electrical power, and another of the terminals being conductively connected to a second power transfer mechanism, such as a sink of electrical power. The surge protector is operable to conduct current form one of the power transfer mechanism to another of the power transfer mechanism in the presence of a prolonged overvoltage surge across the first and second terminals of the surge protector. The surge protection device includes a mechanism for automatically disconnecting one of the terminals from one of the power transfer mechanisms in the presence of a prolonged overvoltage surge across the first and second terminals.Type: GrantFiled: October 17, 1997Date of Patent: August 4, 1998Assignee: Joslyn Electronic Systems CorporationInventors: Wilhelm H. Kapp, Manfred W. Wilms
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Patent number: 5784232Abstract: The present invention involves control and protection circuit for a compressor motor which includes an inductively activated contactor for controlling the flow of current to the compressor motor. The circuitry of the present invention includes a plurality of current detectors associated with each phase winding of the compressor motor for sensing the current in each phase winding. The sensed currents are combined in a predetermined manner and used to provide protection against an overcurrent condition, single phase operation and light loading condition. Additional detector circuits are also connected to the present control and protection circuit to provide protection against high temperature in the compressor motor windings, high temperature in various component of the compressor motor, and undervoltage in the power supply.Type: GrantFiled: June 3, 1997Date of Patent: July 21, 1998Assignee: Tecumseh Products CompanyInventor: James B. Farr
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Patent number: 5763929Abstract: A transistor package includes a power bipolar transistor chip having a thermistor on and electrically connected to a bipolar transistor collector electrode. The thermistor exhibits a positive thermal coefficient (PTC) resistance characteristic and is series connected to the transistor collector. Collector current is interrupted by thermistor response to heat generated during excess transistor collector current events to thereby avoid thermal destruction of the device.Type: GrantFiled: June 16, 1997Date of Patent: June 9, 1998Assignee: Kabushiki Kaisha Tokai Rika Denki SeisakushoInventor: Hitoshi Iwata
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Patent number: 5764470Abstract: A rush current suppression circuit suppresses a peak value of a rush current flowing into a heater. The rush current suppression circuit includes a parallel circuit formed by a positive-characteristic thermistor and a negative-characteristic thermistor. The negative-characteristic thermistor has a resistance at a normal temperature higher than that of the positive-characteristics thermistor. The parallel circuit is connected in series to the heater.Type: GrantFiled: December 4, 1996Date of Patent: June 9, 1998Assignee: Murata Manufacturing Co., Ltd.Inventors: Kenjiro Mihara, Hideaki Niimi, Yuichi Takaoka
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Patent number: 5748429Abstract: A self-checking temperature sensing circuit in which temperature sensitivity is provided by first and second resistive elements having positive and negative temperature coefficients respectively. The resistive elements are connected in parallel current paths, one of which includes a diode for allowing only unidirectional current flow. The resistances of the restrictive elements are determined by a circuit which periodically reverses the polarity of a voltage applied across the parallel paths.Type: GrantFiled: September 9, 1996Date of Patent: May 5, 1998Assignee: Honeywell Inc.Inventor: Scott M. Peterson
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Patent number: 5739999Abstract: A current limiting circuit for use in broadband and combined broadband and telecommunications networks is described. A current limiting element is triggered into a high impedance state in the event of excess current on the line. A sensing element detects the resulting decrease in voltage and operates a switch which disconnects the current limiting element. Timing circuitry reconnects the current limiting element a predetermined period of time after the current limiting element returns to its low impedance state.Type: GrantFiled: August 5, 1996Date of Patent: April 14, 1998Assignee: Lucent Technologies Inc.Inventors: Patricia Lynn Gruber, David Stevens Kerr, Roman Ostapiak
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Patent number: 5737170Abstract: The base of a thermal shutdown bipolar transistor having a V.sub.BE(on) which decreases with increasing temperature is biased with a bias voltage V.sub.PTATbias which increases proportionally with increasing absolute temperature. By supplying the base of the thermal shutdown transistor with a bias voltage V.sub.PTATbias which increases with increasing temperature rather than a bias voltage that remains constant or decreases with increasing temperature, the temperature at which the thermal shutdown transistor turns on is made more predictable and the thermal shutdown transistor is made to turn on more sharply at a desired thermal shutdown temperature. The bias voltage V.sub.PTATbias may be generated by driving a current which increases proportionally with increasing absolute temperature across a resistor. Current sources employing feedback control loops are disclosed for generating such a current. Startup current sources are disclosed for starting control loop operation.Type: GrantFiled: September 27, 1994Date of Patent: April 7, 1998Assignee: Micrel, Inc.Inventor: James C. Moyer
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Patent number: 5714938Abstract: A temperature protection device and method for an air-cooled housing containing electronic equipment is disclosed. A fan forces air to circulate through the housing with air being expelled from the housing at a normal operating temperature inside the housing and with air at an ambient temperature being drawn into the housing. A temperature sensitive element such as a temperature sensitive switch is mounted to the housing such that it is maintained cooler than the operating temperature in the housing as a result of air being drawn into the housing and such that it is exposed to the operating temperature only upon failure of the air circulation. The temperature sensitive element or switch generates an interrupt signal when it senses a response temperature which is near the operating temperature in the housing. In the case of a temperature sensitive switch, power to the electronic equipment may be shut down by the switch.Type: GrantFiled: November 19, 1996Date of Patent: February 3, 1998Assignee: CAE Electronics Ltd.Inventor: Alphonse Schwabl
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Patent number: 5703746Abstract: Wiring harnessess are current feedback paths from the loads to a battery, thereby forming a closed-circuit. For each load, there are provided a current detector and a current control; each current detector compares the current input to a junction box to the output current from the corresponding load via a corresponding wiring harness, and outputs a normal state signal when the two currents are equal. When the input and output currents are at variance with each other, it outputs an abnormal state signal. Each current controller causes, upon receipt of the normal state signal, the input current to flow into the corresponding load along normal current path; upon receipt of the abnormal state signal, the input current is directed to flow to a current cutoff which includes a thermal device which is disposed in parallel with the current path and whose resistance value changes with temperature, thereby cutting off the flow of current to the load.Type: GrantFiled: February 16, 1996Date of Patent: December 30, 1997Assignee: Sumitomo Wiring Systems, Ltd.Inventors: Takahiro Onizuka, Yuuji Saka
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Patent number: 5689395Abstract: An overcurrent protection system which will give a rapid response to relatively small overcurrents. The system, which can be connected between an electrical power supply and an electrical load to form an operating circuit, and which when so connected protects the circuit from overcurrents, has a normal operating condition and a fault condition, and comprises: a circuit interruption element having, (1) a normal state which permits the flow of a normal current, I.sub.NORMAL, when the system is in the normal operating condition, and (2) a fault state which permits the flow of at most a reduced current, substantially less than I.sub.NORMAL, when the system is in the fault condition; and a control element, connected in series with the circuit interruption element, the control element having a variable resistance which (1) is low when the current in the system does not exceed the normal current, I.sub.Type: GrantFiled: November 29, 1995Date of Patent: November 18, 1997Assignee: Raychem CorporationInventors: Hugh Duffy, Craig Wynn, St. Elmo Nickols, III, Brian Thomas
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Patent number: 5684663Abstract: A protection element (10) protects a battery pack (36) from potential faulty conditions in a load (38). The protection element (10) includes a switch (12), a control FET (14), and three resistors (16, 18, and 22). Under normal operating conditions, the switch (12) is conductive and the control FET (14) is non-conductive. If a short circuit is detected, the controller (14) becomes conductive and turns off the switch (12). The switch (12) remains non-conductive until the load (38) is disconnected from the protection element (10). The protection element (10) further includes a temperature sensor (24) that turns off the switch (12) at high temperatures and a current limiting element (28) that imposes an upper limit on the current flowing through the protection element (10). Control signals can be applied to the gate electrodes of the switch (12) and the control FET (14) to modulate the current in the protection element (10).Type: GrantFiled: September 29, 1995Date of Patent: November 4, 1997Assignee: Motorola, Inc.Inventor: Chang Su Mitter
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Patent number: 5663861Abstract: A circuit protection device including a pair of terminals to be electrically connected into an electrical circuit, a pair of spaced current-carrying extensions of the terminals, and an initially low resistance current limiting element extending between the current-carrying extensions. The current-limiting element includes flexible conductive current-feeding arms having inner and outer end portions, the inner end portions thereof being electrically connected to the current-carrying extensions of the terminals. The outer end portions of the current-feeding arms are cantilevered and flexible relative to the inner end portions. The device further preferably includes a PTC current-limiting element sandwiched between the flexible outer end portions of the current-feeding arms.Type: GrantFiled: June 7, 1995Date of Patent: September 2, 1997Assignee: Littelfuse, Inc.Inventors: Nagi Reddi Kanamatha Reddy, Robert Swensen, Thomas F. Draho
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Patent number: 5659454Abstract: The apparatus detects the fact that a predetermined temperature threshold, in particular a low temperature threshold, has been crossed, and prevents any subsequent use of the appliance. The apparatus includes a reversible thermostatic switch capable of changing from a first stable state to a second stable state, and of delivering an alarm signal when it finds itself in the second state; and control means co-operating with the switch to respond to the alarm signal by delivering a disable signal for disabling the electronic appliance. According to the invention, the apparatus further includes a DC voltage source (15), an electrical or electronic component (17) capable of taking two states corresponding to said first and second stable states connected in a loop with the voltage source and the switch so that a current passing through the thermostatic switch causes a change from the first state to the second state.Type: GrantFiled: November 30, 1994Date of Patent: August 19, 1997Assignee: Neopost IndustrieInventor: Bernard Vermesse
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Patent number: 5645746Abstract: Use of PTC circuit protection devices in motor vehicle wiring systems. The devices can replace some or all of the fuses conventionally used. Preferred devices contain PTC conductive polymers. Because the PTC devices can be reset without physical access to them, the wiring system can be arranged more efficiently and more economically. For example, the size of at least some of the wires of the harness can in many cases be reduced.Type: GrantFiled: November 30, 1995Date of Patent: July 8, 1997Assignee: Raychem CorporationInventor: Malcolm R. Walsh
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Patent number: 5644461Abstract: A current limiter for protecting a circuit at a predetermined driving voltage in excess of 50 volts which includes a plurality of PTC resistors connected in series, with a zener diode connected in parallel with each of the PTC resistors, and wherein each of the PTC resistors has a predetermined voltage capacity limit such that the total of the predetermined capacity limits of the PTC resistors exceeds the predetermined driving voltage, and each of the zener diodes has a zener voltage rating less than the predetermined voltage capacity limit of the individual PTC resistor connected in parallel therewith, and the total of the zener voltage ratings of the zener diodes also exceed the predetermined driving voltage.Type: GrantFiled: July 30, 1996Date of Patent: July 1, 1997Assignee: Westinghouse Air Brake CompanyInventors: Craig A. Miller, Joseph C. Fray
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Patent number: 5640059Abstract: A power supply system including a thermal current limiting device operating due to high temperatures. At predetermined temperatures, the device acts to incrementally control the output of a power supply. An implementation of the device may be found in a voltage or power regulator wherein a constant output voltage or power is desired. As temperature increases, the power supply system is not switched off, rather current output is adjusted in a controlled manner thereby eliminating the need for the device to be entirely shut down for a time period. A back-up battery is used to provide supplementing current needed by the load.Type: GrantFiled: December 21, 1995Date of Patent: June 17, 1997Assignee: Reltec CorporationInventors: Neil A. Kammiller, Brian D. Goodlive, Zissis L. Kalivas