US3619703A - Degaussing device having series connected ptc and ntc resistors - Google Patents

Degaussing device having series connected ptc and ntc resistors Download PDF

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Publication number
US3619703A
US3619703A US831451A US3619703DA US3619703A US 3619703 A US3619703 A US 3619703A US 831451 A US831451 A US 831451A US 3619703D A US3619703D A US 3619703DA US 3619703 A US3619703 A US 3619703A
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United States
Prior art keywords
resistor
ntc
resistance
degaussing
ptc
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Expired - Lifetime
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US831451A
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English (en)
Inventor
Hiroshi Yamashita
Kazuo Ishikawa
Masanori Fujimura
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/16—Picture reproducers using cathode ray tubes
    • H04N9/29—Picture reproducers using cathode ray tubes using demagnetisation or compensation of external magnetic fields

Definitions

  • a degaussing device for the picture tube of a color television receiver magnetized by terrestrial magnetism causing color-contamination is described.
  • the device com prises a resistor having a positive temperature coefficient of resistance (PT C resistor), a resistor having a negative temperature coefficient of resistance (NTC resistor), and a coil wound on the picture tube for degaussing, the FTC resistor being connected in series to a parallel circuit of the NTC resistor and the degaussing coil, wherein the FTC resistor and the NTC resistor are in good thermal contact.
  • PT C resistor positive temperature coefficient of resistance
  • NTC resistor negative temperature coefficient of resistance
  • a sufficiently large current for degaussing first flows through the coil and then the PTC resistor, the resistance of which is thereby raised,- reduces the current.
  • the NTC resistor heated by the PTC resistor therefore shows a lower resistance than that of the coil. Consequently, a further reduced current flows through the coil which gives little interference with the working of the picture tube.
  • This invention relates to a degaussing device for the picture tube of a color television receiver which is magnetized by terrestrial magnetism causing color-contamination. More particularly the invention relates to a degaussing device which comprises a resistor having a positive temperature coefi'icient of resistance (a PTC resistor), connected in series with a parallel circuit consisting of a resistor having a negative temperature coefficient of resistance (an NTC resistor) and a coil for degaussing, the PTC resistor and the NTC resistor being in good thermal contact.
  • a PTC resistor positive temperature coefi'icient of resistance
  • an NTC resistor negative temperature coefficient of resistance
  • Two types of degaussing devices have been used in a color television receiver.
  • One comprises an electrical relay contact to be actuated by a bimetal strip which is electrically connected in parallel with a degaussing coil.
  • an electrical relay contact is liable to be oxidized by arcing and this causes an imperfect electrical contact.
  • the onoff action of the relay contact gives rise to high frequency interference. This interference is particularly a serious problem for a color television receiver which works quickly after switch-on.
  • the other comprises a voltage dependent resistor, an NTC resistor, and an ordinary resistor which are electrically connected to a degaussing coil.
  • a voltage dependent resistor an NTC resistor
  • an ordinary resistor which are electrically connected to a degaussing coil.
  • three kinds of resistors require much space and cost.
  • a degaussing device for a picture tube of a color television receiver comprising a resistor having a positive temperature coefficient of resistance (PTC resistor), a resistor having a negative temperature coefficient of resistance (NTC resistor) connected in series with said PTC resistor and a coil wound on said picture tube, said PTC resistor being in thermal contact with said NTC resistor.
  • PTC resistor positive temperature coefficient of resistance
  • NTC resistor negative temperature coefficient of resistance
  • the PT C resistor is a semiconductive barium titanate ceramic having the electrical resistance lower than that of the NTC resistor and an impedance of the degaussing coil at room temperature.
  • the impedance of the degaussing coil is much lower than the resistance of the NTC resistor at room temperature.
  • the FTC resistor shows a rapid and large increase in electrical resistance near the Curie temperature thereof whereas the NTC resistor shows a relatively large decrease in electrical resistance with increasing temperature.
  • the FTC resistor and the NTC resistor are in good thermal contact.
  • Temperature-resistance characteristics of the PTC resistor and the NTC resistor and good thermal coupling between the two resistors of the novel device according to the invention cause an abrupt reduction in the current flowing through the degaussing coil for the picture tube of a color television receiver so as to minimize the current during working of the picture tube after degaussing.
  • FIG. I shows a circuit diagram of the current regulating system of the present invention
  • FIG. 2 shows temperature-resistance characteristics of a PTC resistor and an NTC resistor
  • FIG. 3 shows electrical current variations with time through the PT C resistor, NTC resistor and degaussing coil connected to the present novel current regulating system
  • FIG. 4 shows a cross-sectional view of the present device.
  • a PT C resistor l is electrically connected in series with a parallel circuit consisting of an NTC resistor 2 and a resistor 3. A voltage is applied to the terminals 4 and 5.
  • Temperature-resistance characteristics of the PT C resistor and the NTC resistor in the present current regulating system according to the invention are selected to satisfy the interrelation between their resistances as shown in FIG. 2, where the curves 6 and 7 show respectively temperature-resistance characteristics of the PT C resistor and the NTC resistor.
  • the resistance of the PT C resistor is represented by a resistance 8 and its notation is Rp,.
  • the temperature T is supposed to be room temperature.
  • the notations are respectively Rp, for 9, Rn, for 10 and Rn for 11.
  • the temperature T is a higher temperature than T, where the PT C resistor shows a high resistance value and the NTC resistor shows a low resistance value compared with the resistor 3.
  • the current flowing through the resistor 3 can be calculated by the following equation at temperature T,.
  • I is respectively the current through the resister 3 at T, and T, and R is resistance of the resistor 3.
  • the present novel current regulating system can be used as a degaussing device for a picture tube of a color television receiver by substituting a degaussing coil for the resistor 3.
  • the current I should be large enough for degaussing and the current I, should be a small one so as to give little interference with a picture tube during working.
  • the current reduction from I, to I, should take place before the picture tube begins to work.
  • the FTC resistor, the NTC resistor andthe degaussing coil are selected so as to produce the interrelations between their resistances such that the ratio of the impedance of degaussing coil Rz to Rp, is from to 1:! and the ratio of Rn, to Rz is from 100:1 to 121 at room temperature T, and the ratio of Rp, to Rz is from l000:1 to I021 and the ratio of R: to Rn, is from 10:1 to l000z1 atT,.
  • Time required for the current reduction from I, to I depends on the current value, resistance of the PT C and NTC resistors, their size, their thermal radiation and their temperature-resistance characteristics.
  • the time required for the current reduction should be within 5 seconds for usual television receiver. This quick current reduction has recently become significant for a color television receiver which quickly starts to work after switch-on.
  • the FTC resistor can'be made of any semiconductive barium titanate ceramic having an abrupt increase in electrical resistance above a certain temperature.
  • the semiconductive barium titanate ceramic can be prepared by well-known ceramic techniques. For example, 65 to '70 percent by weight of BaCo,, 28 to 30 percent by weight of TiO,, 0.I to 3 percent by weight of SiO,, and La,0,, Nb,0,, O, or Bi,0 less than 0.5 percent by weight are wet-milled for mixing. The resultant mixture is calcined at 1,2000 C. for 2 hours, pressed into pellets, and fired at about 1,350" C. in air for l to 2 hours.
  • the fired pellets are provided with electrodes by any available method.
  • Preferred electrodes for a ceramic body are silver electrodes made by painting a silver paste on opposite surfaces of the pellet and firing in a nitrogen atmosphere, or a nickelphosphor alloy electrode made by electroless plating.
  • the Curie temperature of barium titanate can be shifted to a higher temperature side by substituting lead for barium and to a lower side by substituting strontium for barium, tin for titanium, or zirconium for titanium.
  • the PTC resistor having a low Curie temperature may be used for the degaussing device which quickly reduces the degaussing current.
  • the FTC resistor with a high Curie temperature may be used for the degaussing device which requires a relatively large degaussing current.
  • the NTC resistor can also be made by well-known ceramic technique. For example, 30 to 38 percent by weight of MnO, 50 to 60 percent by weight of C 0 and 2 to 3 percent by weight of CuO are mixed, calcined at 900 C. for 0.5 to 1 hour, and fired at 1,300 C. in air for 1 to 2 hours. These compositions may be modified by incorporating Cr O MO and TiO The fired body is provided with electrodes by similar method to the preparation of PTC resistors.
  • 15 and 16 designate a disk-type PT C resistor and a disk-type NTC resistor, respectively.
  • the electrodes of the resistors are represented by 17 and 17 and 18 and 18'.
  • soldering In order to keep good thermal coupling between the PTC resistor and the NTC resistor, they are adhered by soldering as shown by 19. Lead wires are soldered to the electrodes 17 and 18.
  • a thin metal sheet is inserted between the electrodes 17' and 18' and it serves as a common terminal of the PTC resistor and NTC resistor for connecting to the degaussing coil.
  • a degaussing device for use with a picture tube of the type employed in color television receivers comprising a. a degaussing coil, b. a resistor having a negative coefficient of resistance (NTC) connected in parallel with said coil, and
  • PTC positive coefficient of resistance

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
US831451A 1968-06-17 1969-06-09 Degaussing device having series connected ptc and ntc resistors Expired - Lifetime US3619703A (en)

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Application Number Priority Date Filing Date Title
JP4239668 1968-06-17

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US3619703A true US3619703A (en) 1971-11-09

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US (1) US3619703A (enrdf_load_stackoverflow)
DE (1) DE1930266B2 (enrdf_load_stackoverflow)
FR (1) FR2011053B1 (enrdf_load_stackoverflow)
GB (1) GB1251453A (enrdf_load_stackoverflow)
NL (1) NL150299B (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2349485A1 (de) * 1972-10-10 1974-04-25 Texas Instruments Inc Heizvorrichtung
US4024427A (en) * 1974-12-16 1977-05-17 U.S. Philips Corporation Degaussing circuit
US4031499A (en) * 1974-07-09 1977-06-21 Siemens Aktiengesellschaft Thermistor device
US4164775A (en) * 1976-07-14 1979-08-14 U.S. Philips Corporation Degaussing circuit in a color television receiver
US5675219A (en) * 1995-12-21 1997-10-07 Thomson Consumer Electronics, Inc. Degaussing circuit for wide-range ac
US5715130A (en) * 1996-02-19 1998-02-03 Murata Manufacturing Co., Ltd. Demagnetization circuit and components therefor
US5722632A (en) * 1995-04-20 1998-03-03 Borg-Warner Automotive, Inc. Temperature-compensated exhaust gas recirculation system
DE19641727A1 (de) * 1996-10-10 1998-04-16 Abb Research Ltd Kaltleiter
US20140110388A1 (en) * 2012-10-23 2014-04-24 Ford Global Technologies, Llc Heated steering wheel

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4654511A (en) * 1974-09-27 1987-03-31 Raychem Corporation Layered self-regulating heating article
US4330703A (en) 1975-08-04 1982-05-18 Raychem Corporation Layered self-regulating heating article
US4177376A (en) 1974-09-27 1979-12-04 Raychem Corporation Layered self-regulating heating article
US4543474A (en) * 1979-09-24 1985-09-24 Raychem Corporation Layered self-regulating heating article
DE3632598A1 (de) * 1986-09-25 1988-04-07 Siemens Ag Bauelement aus mindestens einem heissleiter und mindestens einem kaltleiter

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3486080A (en) * 1966-11-22 1969-12-23 Northern Electric Co Time delay de-energization of relays using thermistors
US3492543A (en) * 1966-05-30 1970-01-27 Victor Company Of Japan Automatic degaussing apparatus
US3495136A (en) * 1965-11-03 1970-02-10 Philips Corp Degaussing circuits

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3495136A (en) * 1965-11-03 1970-02-10 Philips Corp Degaussing circuits
US3492543A (en) * 1966-05-30 1970-01-27 Victor Company Of Japan Automatic degaussing apparatus
US3486080A (en) * 1966-11-22 1969-12-23 Northern Electric Co Time delay de-energization of relays using thermistors

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2349485A1 (de) * 1972-10-10 1974-04-25 Texas Instruments Inc Heizvorrichtung
US4031499A (en) * 1974-07-09 1977-06-21 Siemens Aktiengesellschaft Thermistor device
US4024427A (en) * 1974-12-16 1977-05-17 U.S. Philips Corporation Degaussing circuit
US4164775A (en) * 1976-07-14 1979-08-14 U.S. Philips Corporation Degaussing circuit in a color television receiver
US5722632A (en) * 1995-04-20 1998-03-03 Borg-Warner Automotive, Inc. Temperature-compensated exhaust gas recirculation system
US5675219A (en) * 1995-12-21 1997-10-07 Thomson Consumer Electronics, Inc. Degaussing circuit for wide-range ac
US5715130A (en) * 1996-02-19 1998-02-03 Murata Manufacturing Co., Ltd. Demagnetization circuit and components therefor
DE19641727A1 (de) * 1996-10-10 1998-04-16 Abb Research Ltd Kaltleiter
US20140110388A1 (en) * 2012-10-23 2014-04-24 Ford Global Technologies, Llc Heated steering wheel
US10292207B2 (en) * 2012-10-23 2019-05-14 Ford Global Technologies, Llc Heated steering wheel

Also Published As

Publication number Publication date
NL150299B (nl) 1976-07-15
DE1930266B2 (de) 1971-08-15
DE1930266A1 (de) 1970-01-22
FR2011053A1 (enrdf_load_stackoverflow) 1970-02-27
GB1251453A (enrdf_load_stackoverflow) 1971-10-27
FR2011053B1 (enrdf_load_stackoverflow) 1975-01-10
NL6909138A (enrdf_load_stackoverflow) 1969-12-19

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