EP0776148A1 - Sicherheitsschaltkreis im Vorschaltgerät für Leuchtstofflampen - Google Patents

Sicherheitsschaltkreis im Vorschaltgerät für Leuchtstofflampen Download PDF

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Publication number
EP0776148A1
EP0776148A1 EP96660082A EP96660082A EP0776148A1 EP 0776148 A1 EP0776148 A1 EP 0776148A1 EP 96660082 A EP96660082 A EP 96660082A EP 96660082 A EP96660082 A EP 96660082A EP 0776148 A1 EP0776148 A1 EP 0776148A1
Authority
EP
European Patent Office
Prior art keywords
ballast
lamp
resistance
set forth
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP96660082A
Other languages
English (en)
French (fr)
Other versions
EP0776148B1 (de
Inventor
Arkki Ahonen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Helvar Oy AB
Original Assignee
Helvar Oy AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Helvar Oy AB filed Critical Helvar Oy AB
Publication of EP0776148A1 publication Critical patent/EP0776148A1/de
Application granted granted Critical
Publication of EP0776148B1 publication Critical patent/EP0776148B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
    • H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2851—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
    • H05B41/2855—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against abnormal lamp operating conditions

Definitions

  • the present invention relates to a regulable or controllable electronic ballast for a low-pressure discharge lamp, especially a fluorescent lamp, the operation thereof being based on regulating the light output of a lamp by modifying the frequency of a voltage supplied to the lamp.
  • the invention concerns a method and a circuit system for safeguarding such a ballast against stresses induced by an ageing or otherwise damaged lamp.
  • the ballast shown in fig. 1 of the drawing includes a rectifier V1 connected to a supply voltage Uv, an equalizing capacitor C1, a high-frequency oscillator A1, as well as transistors TR1 and TR2 providing a half-bridge circuit.
  • a lamp LL is connected as part of a resonance circuit, which consists of a capacitor C2 and a coil L1 and which is supplied by alternately conducting transistors TR1 and TR2.
  • a pre-incandescence current for the cathodes of a lamp LL as the lamp is switched on is supplied over a capacitor C3.
  • the oscillator A1 is provided with a control circuit CO1 - CO2, over which the control signal has an effect on the oscillating frequency of the oscillator.
  • this type of ballast includes a special safety feature, often referred to as a stand-by state, for abnormal operating conditions.
  • a special safety feature is e.g. a mains undervoltage, which the oscillator A1 identifies over a circuit C3 and stops for protecting the ballast and the lamp.
  • ballast and similar types of frequency-regulation based ballasts are the functioning of a circuit in a situation, in which the characteristics of a discharge lamp - particularly a fluorescent lamp - for one reason or another differ substantially from the nominal ratings thereof.
  • a situation develops normally along the ageing of a lamp, whereby the emission medium serving as a coating for incandescable lamp cathodes gradually wears away and this deteriorates considerably e.g. the switch-on characteristics of a lamp.
  • the lamp is said to assume a deactivated condition.
  • this condition is quite normal at a certain point over the life-span of a lamp, the time lapse for this phenomenon to develop depending upon factors relating to the design and manufacture of a lamp as well as upon the operating characteristics of a ballast.
  • the ballasts shown in fig. 1 and described in the accompanying specification are characterized in that, in a deactivated lamp, the switch-on timing of a current passing through transistors TR1 and TR2 included in the oscillator circuit of a ballast changes in such a manner that said transistors begin to momentarily conduct simultaneously, which results in the passage of major current surges through the transistors. If the occurrence of this so-called co-conductivity is not somehow precluded, the consequence may be the failure of said half-bridge transistors TR1 and TR2 as a result of an excessive current or a thermal overload.
  • the half-bride transistors TR1 and TR2 with such a control circuit which synchronizes the switching-on of said transistors to the mid-point voltage of the half-bridge, i.e. to the voltage of a connection point between the emitter of TR1 and the collector of TR2.
  • the mid-point voltage higher than a given set value precludes the switching of said transistors to a conducting state.
  • This method requires circuit elements for measuring said mid-point voltage, for setting a set value, as well as for precluding an incorrect base control signal.
  • An object of this invention is to introduce a method and a circuit configuration for eliminating in a simple and reliable manner the simultaneous conduction, i.e. a so-called co-conductivity phenomenon, of transistors included in an electronic ballast.
  • FIG. 3 illustrates an alternative circuit embodiment with respect to a lamp circuit. In a method of the invention, this is performed by measuring the frequency of a voltage being supplied to a lamp LL and by using the obtained measuring result to alter a voltage threshold leading to the activation of a safety circuit.
  • Usefulness of the invention is based on the fact that a control signal proportional to the frequency of a lamp can be produced by means of an extremely simple circuit system by utilizing the frequency-dependency of the impedance of a capacitive circuit element C6. It should be noted that several circuit elements included in the measuring signal circuit are found as such in the basic circuit of a ballast and, thus, can be directly exploited.
  • the frequency of a voltage operating over a lamp is measured with a measuring circuit consisting of a resistance R1 and a capacitor C6. Resistances R2 and R3 are used for setting a suitable voltage level for the measured signal.
  • the measuring signal is guided over a capacitor C7 to a rectifier D1-D2 and further over an equalizing capacitor C8 to a difference element A2, one terminal thereof being set with a reference voltage Vref.
  • an output C04 switches its logic state and stops a ballast oscillator A1.
  • FIG. 4 depicts how the activating voltage for a safety feature of the invention varies in the case of a regulable or controllable ballast as a function of the light intensity level produced by a lamp (LL).
  • a graph 1 represents the behaviour of a lamp voltage in a conventional ballast circuit and a graph 2 in a circuit of the invention.
  • the invention is by no means limited to the described embodiments but is just as well applicable to a number of other ballast circuits based on frequency control, e.g. to multi-lamp ballast versions.
  • Especially the technology relating to switching transistors usable in a half-bridge does not affect the usefulness of the described invention, i.e. this can be achieved by using e.g. a bipolar transistor and a variety of field effect transistors.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
EP19960660082 1995-11-27 1996-11-14 Sicherheitsschaltkreis im Vorschaltgerät für Leuchtstofflampen Expired - Lifetime EP0776148B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI955695 1995-11-27
FI955695A FI98263C (fi) 1995-11-27 1995-11-27 Loistelampun elektronisen liitäntälaitteen suojapiiri

Publications (2)

Publication Number Publication Date
EP0776148A1 true EP0776148A1 (de) 1997-05-28
EP0776148B1 EP0776148B1 (de) 1999-07-28

Family

ID=8544447

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19960660082 Expired - Lifetime EP0776148B1 (de) 1995-11-27 1996-11-14 Sicherheitsschaltkreis im Vorschaltgerät für Leuchtstofflampen

Country Status (3)

Country Link
EP (1) EP0776148B1 (de)
DE (1) DE69603443T2 (de)
FI (1) FI98263C (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0727921A2 (de) * 1995-02-17 1996-08-21 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Schaltungsanordnung zum Betrieb einer Entladungslampe
EP1135006A1 (de) * 2000-03-14 2001-09-19 Société Developpement Industriel et Commercial de Systèmes d'Alimentation DICA Verfahren, System und Erkennungsgerät zur Fernüberwachung von Defekten in Einrichtungen von Gasentladungslampen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4071884A (en) * 1976-06-14 1978-01-31 Micro Components Corporation Integrated circuit high voltage DC converter
JPS6431393A (en) * 1987-07-27 1989-02-01 Matsushita Electric Works Ltd Discharge lamp lighting device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4071884A (en) * 1976-06-14 1978-01-31 Micro Components Corporation Integrated circuit high voltage DC converter
JPS6431393A (en) * 1987-07-27 1989-02-01 Matsushita Electric Works Ltd Discharge lamp lighting device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 013, no. 220 (E - 762) 23 May 1989 (1989-05-23) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0727921A2 (de) * 1995-02-17 1996-08-21 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Schaltungsanordnung zum Betrieb einer Entladungslampe
EP0727921A3 (de) * 1995-02-17 1998-05-27 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Schaltungsanordnung zum Betrieb einer Entladungslampe
EP1135006A1 (de) * 2000-03-14 2001-09-19 Société Developpement Industriel et Commercial de Systèmes d'Alimentation DICA Verfahren, System und Erkennungsgerät zur Fernüberwachung von Defekten in Einrichtungen von Gasentladungslampen

Also Published As

Publication number Publication date
FI98263C (fi) 1997-05-12
FI98263B (fi) 1997-01-31
EP0776148B1 (de) 1999-07-28
DE69603443T2 (de) 1999-11-25
DE69603443D1 (de) 1999-09-02
FI955695A0 (fi) 1995-11-27

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