US3794859A - Apparatus for obviating undesirable operation of an electric circuit due to faulty switching - Google Patents
Apparatus for obviating undesirable operation of an electric circuit due to faulty switching Download PDFInfo
- Publication number
- US3794859A US3794859A US00295612A US3794859DA US3794859A US 3794859 A US3794859 A US 3794859A US 00295612 A US00295612 A US 00295612A US 3794859D A US3794859D A US 3794859DA US 3794859 A US3794859 A US 3794859A
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- United States
- Prior art keywords
- circuit
- electric circuit
- voltage
- switch
- gating circuit
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/35—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar semiconductor devices with more than two PN junctions, or more than three electrodes, or more than one electrode connected to the same conductivity region
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/72—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region
- H03K17/73—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region for dc voltages or currents
Definitions
- the disclosure relates to a gating circuit which is normally operated by means of an external switching de vice which supplies the necessary power to the gating circuit.
- a PTC element is provided in parallel with the gating circuit whereby, in the event that the switch which supplies power to the gating circuit is leaky and presents a high resistance rather than an infinite resistance in its open state, the currents provided to the.
- the disclosure relates to the use of a PTC element in parallel with an electrical circuit and, more specifically, to the use of a PTC element in parallel with an electrical circuit to prevent operation of the electrical circuit in the event that theswitch in the power circuit supplying power thereto is faulty and provides a reduced level of voltage thereacross, even when in its open state.
- the above problems of the prior art are overcome by providing an impedance in shunt with the electrical circuit.
- the im pedance has the property of having a low resistance value when a low voltage is presented thereacross.
- the impedance also has the property that when a'predetermined high voltage is placed thereacross, the resistance thereof increases dramatically. Accordingly, when the switch element is in the open state, the voltage across both the electric circuit and-the impedance is relatively low and most of the current is thereby shunted arognd the electric circuit and through the impedance element.
- the FIGURE is a circuit diagram of a relay gating circuit with a protective element thereacross in accordance with the present invention.
- the circuit includes a relay coil 1 which is utilized to operate external switches or other appropriate elements. Current to the coil 1 is provided from the line 5 via a triac 3 having a gate 7 thereon. The triac 3 is energized by a pulse transformer having secondary winding 9 and primary winding 11. Pulses are supplied from the primary winding 11 to the secondary winding 9 of the pulse transformer via a relaxation oscillator 13 which includes the primary winding 11, a
- the relaxation oscillator 13 A 19 whereupon a pulse is provided for the relaxation 05- l cillator 13, the pulse being transferred from the primary winding 11 to the secondary winding 9 of the pulse transformer and causing the triac 3 to operate due to the increased voltage on the gate 7 thereof. This will allow voltage from the line to pass through the triac 3 and the coil 1 and allow operation of the coil in well known manner.
- the switch 19 which can be a normal electrical switch, a semiconductor switch or the like, does not present an open circuit when in its open condition, but rather is leaky in nature (i.e., 10K ohms)
- current from the line 5 will pass to the line 25 through the relaxation oscillator 13, the switch 19 thereby merely acting as a high resistance and providing a voltage which is less than the normal line voltage at the point marked 27 in the FIGURE which is the junction of the switch 19 and the resistor 21.
- This voltage can still be of sufficiently high value to cause the relaxation oscillator 13 to operate and provide a pulse to winding 9, thereby providing unwanted and undesired operation of the triac 3 and the coil 1 in the same manner as described for normal operation.
- an impedance element 29 in shunt with the entire electrical circuit composed of the components of the relaxation osals have a relatively constant resistance for increase in temperature until a particular threshold temperature is reached whereupon, at the anomaly temperature, the temperature coefficient of the material increases dramatically.
- the PTC sensors are usually formed from doped barium titanate, the anomalous behavior being caused by a change in the crystal structure of the doped barium titanate ceramic.
- the characteristic anomaly temperature and resultant temperature coefficient are determined by the chemical composition of the barium titanate. Resistance changes of the PTC devices in a steep slope region after the anomaly temperature has been reached fall in the range of 25 to percent per degree centigrade.
- the anomaly temperature herein is reached due to the R heating therein generated by the increase in the voltage thereacross.
- the switch 19 When the switch 19 is open, the voltage across the impedance element 29 as well as the electric circuit will be relatively low, even in the event of leakage. In this event the resistance of the impedance element 29 will be low compared to that of the electric circuit composed of the oscillator 13 and resistors 21 and 23. The impedance 29 will therefore act as a shunt and cause current to flow substantially therethrough rather than through the electric curcuit, thereby preventing any false operation of the electric circuit.
- the switch 19 When the switch 19 is closed, the entire line voltage is placed across both the electric circuit and the impedance element 29. At this voltage, the PTC element will heat up and substantially increase its resistance, whereby a substantial part of the current from the line will pass through the electric circuit and cause normal operation thereof. It can therefore be seen that the particular type of impedance element utilized herein will substantially eliminate faulty operation of the electric circuit due to the inability to completely switch off power from a power supply.
- the capacitor 31 and resistor 33 which are in shunt with the triac 3 are placed in the circuit to prevent operation of the triac due to spurious transients in the line.
- the resistor 35 performs the same function.
- a circuit operation connection device which comprises, in combination: a. an electric circuit,
- switch means coupled to said electric circuit, 0. a source of power coupled across said electric circuit and said switch means, and d. impedance means connected in shunt with said electric circuit, having a low resistance relative to said electric circuit when the voltage across said electric circuit is below a predetermined value and having a high resistance relative to said electric circuit when the voltage across said electric circuit is above said predetermined value.
- impedance means is a PTC device.
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- Electronic Switches (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
The disclosure relates to a gating circuit which is normally operated by means of an external switching device which supplies the necessary power to the gating circuit. A PTC element is provided in parallel with the gating circuit whereby, in the event that the switch which supplies power to the gating circuit is leaky and presents a high resistance rather than an infinite resistance in its open state, the currents provided to the gating circuit under these conditions will be shunted around the gating circuit through the PTC elements. Under operation where the switch is closed, the PTC elements will rapidly change to high resistance elements and thereby effectively remove themselves from the circuit.
Description
United States Patent [1 1 Finnegan [451 Feb. 26, 1974 APPARATUS FOR OBVIATING UNDESIRABLE OPERATION OF AN ELECTRIC CIRCUIT DUE TO FAULTY SWITCHING [75] Inventor:
[73] Assignee: Texas Instruments Incorporated,
Dallas, Tex.
221 Filed: Oct. 6, 1972 21 Appl. No.: 295,612
Francis Finnegan, Wrentham, Mass.
[52] U.S. Cl 307/238, 307/240, 307/310, 215/504 [51 Int. Cl. H03k 5/08, H03k 17/00 [58] Field of Search 317/234 G, 234 H; 215/504, 215/505; 307/238, 239, 240, 310
[56] References Cited UNITED STATES PATENTS 2,947,844 ,8/1960 Howling 219/505 3,252,052 5/1966 Nash 307/239 3,325,598 6/1967 O'Neill 307/239 3,426,441 2/1969 Broski 219/505 3,467,817 9/1969 Fricker 219/505 3,474,963 10/1969 Buiting et a1. 219/505 3,582,762 6/1971 Mori 317/234 H 3,590,365 6/1971 Nelson 219/505 3,600,650 8/1971 Obenhaus 317/234 H 3,619,560 11/1971 Buiting 219/505 Primary Examiner-John S. Heyman Assistant Examiner-Andrew J. James Attorney, Agent, or Firm-John A. l-laug; Edward .1. Connors, Jr.; James P. McAndrews 5 7] ABSTRACT The disclosure relates to a gating circuit which is normally operated by means of an external switching de vice which supplies the necessary power to the gating circuit. A PTC element is provided in parallel with the gating circuit whereby, in the event that the switch which supplies power to the gating circuit is leaky and presents a high resistance rather than an infinite resistance in its open state, the currents provided to the.
gating circuit under these conditions will be shunted around the gating circuit through the PTC elements. Under operation where the switch is closed, the PTC elements will rapidly change to high resistance elements and thereby effectively remove themselves from the circuit.
6 Claims, 1 Drawing Figure 1 PAIENIEDFEBZBIBH I 3794.859
APPARATUS FOR OBVIATING UNDESIRABLE OPERATION OF AN ELECTRIC CIRCUIT DUE TO FAULTY SWITCHING The disclosure relates to the use of a PTC element in parallel with an electrical circuit and, more specifically, to the use of a PTC element in parallel with an electrical circuit to prevent operation of the electrical circuit in the event that theswitch in the power circuit supplying power thereto is faulty and provides a reduced level of voltage thereacross, even when in its open state.
It is well known that power is applied to electrical circuits on an on and off basis by means of switching elements such as electrical switches, electronic switches and the like. It is often the case, due to faulty electronic switches or dueto deterioration of poor environmental conditions of the electrical switch, that when the switches are in their open state, they can merely provide a high resistance rather than an open circuit from the source of power to the electrical circuit and they therefore continue to provide a voltage across the electrical circuit. Often, the level of voltage supplied to the electrical circuit, even when the switch is in the open condition, is sufficient to cause undesired operation of such electrical circuits. It is such undesired operation which it is desired to correct.
In accordacne with the present invention, the above problems of the prior art are overcome by providing an impedance in shunt with the electrical circuit. The im pedance has the property of having a low resistance value when a low voltage is presented thereacross. The impedance also has the property that when a'predetermined high voltage is placed thereacross, the resistance thereof increases dramatically. Accordingly, when the switch element is in the open state, the voltage across both the electric circuit and-the impedance is relatively low and most of the current is thereby shunted arognd the electric circuit and through the impedance element. When the switch is in the closed state, the volt age across the electric circuit and impedance element is materially increased, thereby substantially increasing the resistance of the impedance element and causing substantially all of the current from the power supply to pass through the electric circuit. In this way, the problems caused by leaky switching elements as described above are overcome.
It is therefore an object of this invention to provide a protective circuit for an electric circuit which precludes operation of the electric circuit due to a leaky switch at the power supply.
It is a further object of this invention to provide a PTC element in shunt with an electric circuit for shunting current around the electric circuit below predetermined voltage conditions thereacross.
It is a yet further object of this invention to provide a circuit element configuration which overcomes faulty operation of an electric circuit due to faulty switches or switching elements in the power supply circuit thereto.
The above objects and still further objects of the invention will immediately become apparent to those skilled in the art after consideration of the following preferred embodiment thereof, which is provided by way of example and not by way of limitation, wherein:
The FIGURE is a circuit diagram of a relay gating circuit with a protective element thereacross in accordance with the present invention.
Referring now to the FIGURE, there is shown a relay gating circuit of a type known in the prior art with an impedance element in shunt therewith which presents a low impedance relative to the impedance of the gating circuit when the voltage thereacross is below some predetermined value and presents a very high impedance relative to the impedance across the gating circuit when the voltage thereacross is above the predetermined voltage level. The circuit includes a relay coil 1 which is utilized to operate external switches or other appropriate elements. Current to the coil 1 is provided from the line 5 via a triac 3 having a gate 7 thereon. The triac 3 is energized by a pulse transformer having secondary winding 9 and primary winding 11. Pulses are supplied from the primary winding 11 to the secondary winding 9 of the pulse transformer via a relaxation oscillator 13 which includes the primary winding 11, a
diac 15 and a capacitor 17. The relaxation oscillator 13 A 19, whereupon a pulse is provided for the relaxation 05- l cillator 13, the pulse being transferred from the primary winding 11 to the secondary winding 9 of the pulse transformer and causing the triac 3 to operate due to the increased voltage on the gate 7 thereof. This will allow voltage from the line to pass through the triac 3 and the coil 1 and allow operation of the coil in well known manner.
When the switch 19, which can be a normal electrical switch, a semiconductor switch or the like, does not present an open circuit when in its open condition, but rather is leaky in nature (i.e., 10K ohms), current from the line 5 will pass to the line 25 through the relaxation oscillator 13, the switch 19 thereby merely acting as a high resistance and providing a voltage which is less than the normal line voltage at the point marked 27 in the FIGURE which is the junction of the switch 19 and the resistor 21. This voltage can still be of sufficiently high value to cause the relaxation oscillator 13 to operate and provide a pulse to winding 9, thereby providing unwanted and undesired operation of the triac 3 and the coil 1 in the same manner as described for normal operation. Accordingly, there is provided an impedance element 29 in shunt with the entire electrical circuit composed of the components of the relaxation osals have a relatively constant resistance for increase in temperature until a particular threshold temperature is reached whereupon, at the anomaly temperature, the temperature coefficient of the material increases dramatically. The PTC sensors are usually formed from doped barium titanate, the anomalous behavior being caused by a change in the crystal structure of the doped barium titanate ceramic. The characteristic anomaly temperature and resultant temperature coefficient are determined by the chemical composition of the barium titanate. Resistance changes of the PTC devices in a steep slope region after the anomaly temperature has been reached fall in the range of 25 to percent per degree centigrade. The anomaly temperature herein is reached due to the R heating therein generated by the increase in the voltage thereacross.
When the switch 19 is open, the voltage across the impedance element 29 as well as the electric circuit will be relatively low, even in the event of leakage. In this event the resistance of the impedance element 29 will be low compared to that of the electric circuit composed of the oscillator 13 and resistors 21 and 23. The impedance 29 will therefore act as a shunt and cause current to flow substantially therethrough rather than through the electric curcuit, thereby preventing any false operation of the electric circuit. When the switch 19 is closed, the entire line voltage is placed across both the electric circuit and the impedance element 29. At this voltage, the PTC element will heat up and substantially increase its resistance, whereby a substantial part of the current from the line will pass through the electric circuit and cause normal operation thereof. It can therefore be seen that the particular type of impedance element utilized herein will substantially eliminate faulty operation of the electric circuit due to the inability to completely switch off power from a power supply.
The capacitor 31 and resistor 33 which are in shunt with the triac 3 are placed in the circuit to prevent operation of the triac due to spurious transients in the line. The resistor 35 performs the same function.
Although the invention has been described with respect to a specific preferred embodiment thereof, many variations and modifications thereof will immediately become apparent to those skilled in the art. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.
What is claimed is;
1. A circuit operation connection device which comprises, in combination: a. an electric circuit,
b. switch means coupled to said electric circuit, 0. a source of power coupled across said electric circuit and said switch means, and d. impedance means connected in shunt with said electric circuit, having a low resistance relative to said electric circuit when the voltage across said electric circuit is below a predetermined value and having a high resistance relative to said electric circuit when the voltage across said electric circuit is above said predetermined value. 2. A circuit as set forth in claim 1 wherein said impedance means is a PTC device.
3. A circuit as set forth in claim 2 wherein said PTC device is a doped barium titanate device wherein the Curie point of said PTC device is reached when a voltage of at least said predetermined voltage is placed thereacross.
4. A circuit as set forth in claim 1 wherein said switch means has open and closed states, said switch, when in its open state providing a voltage less than said predetermined voltage, across said electric circuit.
Claims (6)
1. A circuit operation connection device which comprises, in combination: a. an electric circuit, b. switch means coupled to said electric circuit, c. a source of power coupled across said electric circuit and said switch means, and d. impedance means connected in shunt with said electric circuit, having a low resistance relative to said electric circuit when the voltage across said electric circuit is below a predetermined value and having a high resistance relative to said electric circuit when the voltage across said electric circuit is above said predetermined value.
2. A circuit as set forth in claim 1 wherein said impedance means is a PTC device.
3. A circuit as set forth in claim 2 wherein said PTC device is a doped barium titanate device wherein the Curie point of said PTC device is reached when a voltage of at least said predetermined voltage is placed thereacross.
4. A circuit as set forth in claim 1 wherein said switch means has open and closed states, said switch, when in its open state providing a voltage less than said predetermined voltage, across said electric circuit.
5. A circuit as set forth in claim 2 wherein said switch means has open and closed states, said switch, when in its open state providing a voltage less than said predetermined voltage, across said electric circuit.
6. A circuit as set forth in claim 3 wherein said switch means has open and closed states, said switch, when in its open state providing a voltage less than said predetermined voltage, across said electric circuit.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US29561272A | 1972-10-06 | 1972-10-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3794859A true US3794859A (en) | 1974-02-26 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US00295612A Expired - Lifetime US3794859A (en) | 1972-10-06 | 1972-10-06 | Apparatus for obviating undesirable operation of an electric circuit due to faulty switching |
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| Country | Link |
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| US (1) | US3794859A (en) |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2947844A (en) * | 1958-03-24 | 1960-08-02 | Mc Graw Edison Co | Positive temperature coefficient semiconductor device |
| US3252052A (en) * | 1963-08-23 | 1966-05-17 | Jacuzzi Bros Inc | Leakage detection and control circuit |
| US3325598A (en) * | 1963-09-18 | 1967-06-13 | Bell Telephone Labor Inc | Remote condition monitoring circuit with ringing current actuated switch connecting twomode oscillator to telephone line |
| US3426441A (en) * | 1967-01-30 | 1969-02-11 | Curtis Helene Ind Inc | Electric hair dryer |
| US3467817A (en) * | 1967-02-23 | 1969-09-16 | West Bend Co | Temperature control circuit |
| US3474963A (en) * | 1967-05-24 | 1969-10-28 | Texas Instruments Inc | Thermistor temperature control system |
| US3582762A (en) * | 1968-04-27 | 1971-06-01 | Nippon Denso Co | Integrated circuit semiconductor-type voltage regulator and charging generator apparatus equipped with the same |
| US3590365A (en) * | 1969-09-03 | 1971-06-29 | Eastman Kodak Co | Temperature control apparatus |
| US3600650A (en) * | 1968-12-30 | 1971-08-17 | Texas Instruments Inc | Protected semiconductor device having sensor thermally coupled to electrode |
| US3619560A (en) * | 1969-12-05 | 1971-11-09 | Texas Instruments Inc | Self-regulating thermal apparatus and method |
-
1972
- 1972-10-06 US US00295612A patent/US3794859A/en not_active Expired - Lifetime
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2947844A (en) * | 1958-03-24 | 1960-08-02 | Mc Graw Edison Co | Positive temperature coefficient semiconductor device |
| US3252052A (en) * | 1963-08-23 | 1966-05-17 | Jacuzzi Bros Inc | Leakage detection and control circuit |
| US3325598A (en) * | 1963-09-18 | 1967-06-13 | Bell Telephone Labor Inc | Remote condition monitoring circuit with ringing current actuated switch connecting twomode oscillator to telephone line |
| US3426441A (en) * | 1967-01-30 | 1969-02-11 | Curtis Helene Ind Inc | Electric hair dryer |
| US3467817A (en) * | 1967-02-23 | 1969-09-16 | West Bend Co | Temperature control circuit |
| US3474963A (en) * | 1967-05-24 | 1969-10-28 | Texas Instruments Inc | Thermistor temperature control system |
| US3582762A (en) * | 1968-04-27 | 1971-06-01 | Nippon Denso Co | Integrated circuit semiconductor-type voltage regulator and charging generator apparatus equipped with the same |
| US3600650A (en) * | 1968-12-30 | 1971-08-17 | Texas Instruments Inc | Protected semiconductor device having sensor thermally coupled to electrode |
| US3590365A (en) * | 1969-09-03 | 1971-06-29 | Eastman Kodak Co | Temperature control apparatus |
| US3619560A (en) * | 1969-12-05 | 1971-11-09 | Texas Instruments Inc | Self-regulating thermal apparatus and method |
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