WO2004057930A1 - Apparatus for igniting a high pressure gas discharge lamp - Google Patents

Apparatus for igniting a high pressure gas discharge lamp Download PDF

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Publication number
WO2004057930A1
WO2004057930A1 PCT/IB2003/005743 IB0305743W WO2004057930A1 WO 2004057930 A1 WO2004057930 A1 WO 2004057930A1 IB 0305743 W IB0305743 W IB 0305743W WO 2004057930 A1 WO2004057930 A1 WO 2004057930A1
Authority
WO
WIPO (PCT)
Prior art keywords
lamp
ignition
voltage
generator
gas discharge
Prior art date
Application number
PCT/IB2003/005743
Other languages
French (fr)
Inventor
Winston D. Couwenberg
Ronald H. Van Der Voort
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Priority to AU2003303172A priority Critical patent/AU2003303172A1/en
Publication of WO2004057930A1 publication Critical patent/WO2004057930A1/en

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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
    • H05B41/2821—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 by means of a single-switch converter or a parallel push-pull converter in the final stage
    • H05B41/2822—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 by means of a single-switch converter or a parallel push-pull converter in the final stage using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations

Definitions

  • the invention relates to an apparatus for igniting a high pressure gas discharge lamp, comprising a generator for generating a AC voltage and a piezo-electric transformer of which the input is coupled to the output of the generator and of which the output is adapted for coupling with said gas discharge lamp and which is adapted to generate a voltage sufficiently high to cause ignition of the high pressure gas discharge lamp.
  • This prior art apparatus is adapted to generate an ignition voltage for igniting a gas discharge lamp connected to the apparatus.
  • complicated features, like antenna's in the lamp, etc. have to be provided.
  • the aim of the invention is to provide an ignition apparatus which does not only provide sufficient voltage to cause ignition, but which also is adapted provide for the 'take over' the power supply after ignition until normal operation through thermal emission of the gas discharge lamp has been established.
  • the output voltage of the piezoelectric transformer is at least partially dependent on the impedance of the lamp such that the voltage applied over the lamp decreases after ignition has taken place.
  • the running of a gas discharge lamp takes place in one of the three following phases: the ignition phase in which a high voltage is required to cause the initial ignition but wherein the required power is limited; the 'take over' phase in which the discharge is maintained through the glow discharge. In this phase the required voltage is substantially lower while the required power is much higher than in the ignition phase; and the steady state phase in which the discharge is maintained through thermal emission.
  • the impedance of the lamp is significantly lowered.
  • the invention makes use of this effect by making the output voltage, that is the voltage supplied to the lamp dependant on said impedance of the lamp. This allows a high voltage to be applied during the ignition phase so that ignition can be caused.
  • the frequency of the supply generator is substantially equal to the resonance frequency of the piezoelectric transformer. Consequently the output voltage of the piezoelectric transformer is at its maximum.
  • a first embodiment teaches that the generator comprises a resonance circuit of which the impedance of the lamp forms a part. This feature offers the possibility to let the voltage applied on the lamp 'swing up' as caused by the high impedance of the lamp during ignition and to lower the voltage substantially after the ignition during the 'take over' phase in which a glow discharge develops.
  • the piezoelectric transformer is adapted to supply sufficient power to the lamp to 'take over' the power supply thereof during the phase directly following the ignition.
  • the generator is adapted to initially generate an AC voltage which coincides substantially with the resonance frequency of the piezoelectric transformer.
  • This feature allows a maximum voltage to be obtained at the output of the piezo electric transformer, in particular during the ignition phase, but also subsequently during the 'take over' phase during which the high power transfer possibility of the piezoelectric system is required.
  • the features of the invention provide in the adaptation of the lamp voltage during the ignition phase and the 'take over' phase following thereupon, there may be reasons that the adaptation thus caused is insufficient.
  • the generator is adapted to gradually change its frequency after ignition has taken place. This change of frequency causes a change of output voltage of the piezoelectric transformer and hence of the lamp voltage as the transfer characteristic of the piezoelectric transformer is frequency dependent.
  • the high pressure gas discharge lamps receive their power supply in the steady state directly from the mains through a ballast which may be conventional or which may be formed by an electronic ballast.
  • the invention is primarily directed to the first and second phase of the lamp operation, it is likely that the invention will also be implemented in the complete power supply units for high pressure gas discharge lamps. Such units will, of course be comprised of ballasts for supply of the lamp during the normal steady state phase.
  • the complete power supply according to the invention will however also provide the elements for ignition and 'take over' the lamp.
  • possibilities open allowing the ballast to be incorporated into the elements already present for the start of the circuit, allowing substantial savings in costs, volume and weight.
  • Figure 1 a diagram of an advantageous embodiment of the invention
  • Figure 2 a time- voltage diagram of the output voltage of the piezoelectric transformer of Fig. 1.
  • Fig. 1 shows a lamp 1 which is connected to a power supply circuit 2 through a ballast 3. These two components provide power supply of the lamp during normal steady state operation of the lamp.
  • a dedicated ignition circuit is provided which comprises a generator 4 and a piezoelectric transformer 5.
  • the generator 4 is adapted to generate a high frequent voltage which is supplied to the input of the piezoelectric transformer 5.
  • piezoelectric transformer transformers the supplied voltage to a high voltage which is supplied to the lamp to cause ignition.
  • the ignition of the lamp 1 takes place in two phases; the initial ignition phase in which the lamp 1 ignites and the so called 'take over' phase in which the discharge in the lamp is formed by a glow discharge, requiring less voltage but a substantially higher power than during ignition.
  • the generator 4 is adapted for initially generating a signal with the resonance frequency of the piezoelectric transformer 5.
  • the secondary voltage developed at the output of the piezoelectric transformer is at its maximum to cause ignition of the lamp.
  • Fig. 2 shows a time- voltage diagram of the output voltage of the piezoelectric transformer.
  • the discharge in the lamp amends to a glow discharge.
  • the apparatus according to the invention provides the lamp with enough energy to heat up the electrodes until thermionic emission is reached.
  • the lamp voltage during this phase is between 200V and 300V.
  • This change of frequency may be caused by the change of the resistance of the lamp, as caused by the transition of one phase to the other, but also under control of a control apparatus, (incorporated in the generator) which may be adapted to detect the transition of phases in the lamp.
  • the glow discharge consumes a larger current than the ignition current.
  • the recent availability of new materials allowing larger powers to be transformed by piezoelectric transformer makes the supply of such powers feasible.
  • the electrodes of the lamp are heated. After sufficient heat has been captured by the electrodes normal thermal emission develops and steady state operation of the lamp is obtained.
  • the apparatus may comprise control facilities to end the starting operation by the start circuit.
  • These facilities may comprise a timer, a thermal sensor for sensing the existing of the normal thermal operation of the lamp or a voltage sensor.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

The invention relates to an apparatus for igniting a high-pressure gas discharge lamp, comprising:- a generator for generating a AC voltage; and- a piezoelectric transformer of which the input is coupled to the output of the generator and of which the output is adapted for coupling with said gas discharge lamp and which is adapted to generate a voltage sufficiently high to cause ignition of the high pressure gas discharge lamp, wherein the output voltage of the piezoelectric transformer is at least partially dependent on the impedance of the lamp such that the voltage applied over the lamp decreases changes after ignition has taken place. This allows a high voltage to be applied during the ignition phase so that ignition can be caused. In this initial phase the frequency of the supply generator is substantially equal to the resonance frequency of the piezo-electric transformer.

Description

Apparatus for igniting a high pressure gas discharge lamp
The invention relates to an apparatus for igniting a high pressure gas discharge lamp, comprising a generator for generating a AC voltage and a piezo-electric transformer of which the input is coupled to the output of the generator and of which the output is adapted for coupling with said gas discharge lamp and which is adapted to generate a voltage sufficiently high to cause ignition of the high pressure gas discharge lamp.
Such an apparatus is known from EP-A-0665 600.
This prior art apparatus is adapted to generate an ignition voltage for igniting a gas discharge lamp connected to the apparatus. However no provisions appear to have been taken for the phase following the ignition. To keep the lamp running after ignition, complicated features, like antenna's in the lamp, etc. have to be provided.
The aim of the invention is to provide an ignition apparatus which does not only provide sufficient voltage to cause ignition, but which also is adapted provide for the 'take over' the power supply after ignition until normal operation through thermal emission of the gas discharge lamp has been established.
This aim is reached in that the output voltage of the piezoelectric transformer is at least partially dependent on the impedance of the lamp such that the voltage applied over the lamp decreases after ignition has taken place. Generally the running of a gas discharge lamp takes place in one of the three following phases: the ignition phase in which a high voltage is required to cause the initial ignition but wherein the required power is limited; the 'take over' phase in which the discharge is maintained through the glow discharge. In this phase the required voltage is substantially lower while the required power is much higher than in the ignition phase; and the steady state phase in which the discharge is maintained through thermal emission. Although it is possible to use a piezoelectric transformer for the ignition phase, hitherto it was not possible to use this piezoelectric transformer for the 'take over' phase as well, due to the different requirements needed for this phase.
During the 'take over' phase the impedance of the lamp is significantly lowered. The invention makes use of this effect by making the output voltage, that is the voltage supplied to the lamp dependant on said impedance of the lamp. This allows a high voltage to be applied during the ignition phase so that ignition can be caused. In this initial phase the frequency of the supply generator is substantially equal to the resonance frequency of the piezoelectric transformer. Consequently the output voltage of the piezoelectric transformer is at its maximum.
When the high pressure gas discharge lamp has ignited, the phase of the discharge goes to the 'take over' phase in which there is much less voltage required to maintain the glow discharge then in force. The dependency of the voltage applied to the lamp from the impedance of the lamp provides a substantially lower voltage to be applied to the lamp. Due to the fact that recently much more powerful piezoelectric transformers have become available the power supplied to the lamp in this 'take over' phase is sufficient to maintain the glow discharge.
A first embodiment teaches that the generator comprises a resonance circuit of which the impedance of the lamp forms a part. This feature offers the possibility to let the voltage applied on the lamp 'swing up' as caused by the high impedance of the lamp during ignition and to lower the voltage substantially after the ignition during the 'take over' phase in which a glow discharge develops.
The current flowing during this glow discharge is much larger than the initial current. Hence the required power is substantially more than the power during ignition.
According to another preferred embodiment the piezoelectric transformer is adapted to supply sufficient power to the lamp to 'take over' the power supply thereof during the phase directly following the ignition.
The fact that in the 'take over' phase more power is required is catered for by the fact that recently piezo electric transformers have become available which are adapted to transform much higher powers than hitherto.
According to yet another preferred embodiment, the generator is adapted to initially generate an AC voltage which coincides substantially with the resonance frequency of the piezoelectric transformer. This feature allows a maximum voltage to be obtained at the output of the piezo electric transformer, in particular during the ignition phase, but also subsequently during the 'take over' phase during which the high power transfer possibility of the piezoelectric system is required. Although the features of the invention provide in the adaptation of the lamp voltage during the ignition phase and the 'take over' phase following thereupon, there may be reasons that the adaptation thus caused is insufficient. For such circumstances another preferred embodiment teaches that the generator is adapted to gradually change its frequency after ignition has taken place. This change of frequency causes a change of output voltage of the piezoelectric transformer and hence of the lamp voltage as the transfer characteristic of the piezoelectric transformer is frequency dependent.
Usually the high pressure gas discharge lamps receive their power supply in the steady state directly from the mains through a ballast which may be conventional or which may be formed by an electronic ballast.
Although the invention is primarily directed to the first and second phase of the lamp operation, it is likely that the invention will also be implemented in the complete power supply units for high pressure gas discharge lamps. Such units will, of course be comprised of ballasts for supply of the lamp during the normal steady state phase. The complete power supply according to the invention will however also provide the elements for ignition and 'take over' the lamp. Herein possibilities open allowing the ballast to be incorporated into the elements already present for the start of the circuit, allowing substantial savings in costs, volume and weight.
Subsequently the present invention will be elucidate with the help of the accompanying drawings showing:
Figure 1: a diagram of an advantageous embodiment of the invention; and Figure 2: a time- voltage diagram of the output voltage of the piezoelectric transformer of Fig. 1.
Fig. 1 shows a lamp 1 which is connected to a power supply circuit 2 through a ballast 3. These two components provide power supply of the lamp during normal steady state operation of the lamp. For ignition of the lamp, a dedicated ignition circuit is provided which comprises a generator 4 and a piezoelectric transformer 5. The generator 4 is adapted to generate a high frequent voltage which is supplied to the input of the piezoelectric transformer 5. piezoelectric transformer transformers the supplied voltage to a high voltage which is supplied to the lamp to cause ignition.
As stated before, the ignition of the lamp 1 takes place in two phases; the initial ignition phase in which the lamp 1 ignites and the so called 'take over' phase in which the discharge in the lamp is formed by a glow discharge, requiring less voltage but a substantially higher power than during ignition. The generator 4 is adapted for initially generating a signal with the resonance frequency of the piezoelectric transformer 5. The secondary voltage developed at the output of the piezoelectric transformer is at its maximum to cause ignition of the lamp.
Fig. 2 shows a time- voltage diagram of the output voltage of the piezoelectric transformer. Once ignition has taken place which is indicated by 6 in Fig. 2, the discharge in the lamp amends to a glow discharge. The apparatus according to the invention provides the lamp with enough energy to heat up the electrodes until thermionic emission is reached. The lamp voltage during this phase is between 200V and 300V. This change of frequency may be caused by the change of the resistance of the lamp, as caused by the transition of one phase to the other, but also under control of a control apparatus, (incorporated in the generator) which may be adapted to detect the transition of phases in the lamp.
Another matter is that the glow discharge consumes a larger current than the ignition current. The recent availability of new materials allowing larger powers to be transformed by piezoelectric transformer makes the supply of such powers feasible. During the glow discharge the electrodes of the lamp are heated. After sufficient heat has been captured by the electrodes normal thermal emission develops and steady state operation of the lamp is obtained.
Although not described above the apparatus according to the invention may comprise control facilities to end the starting operation by the start circuit. These facilities may comprise a timer, a thermal sensor for sensing the existing of the normal thermal operation of the lamp or a voltage sensor.
It will be clear that numerous other amendments can be made to the described embodiment without departing from the claims.

Claims

CLAIMS:
1. Apparatus for igniting a high pressure gas discharge lamp, comprising: a generator for generating a AC voltage; and a piezoelectric transformer of which the input is coupled to the output of the generator and of which the output is adapted for coupling with said gas discharge lamp and which is adapted to generate a voltage sufficiently high to cause ignition of the high pressure gas discharge lamp, characterized in that the output voltage of the piezoelectric transformer is at least partially dependent on the impedance of the lamp such that the voltage applied over the lamp decreases changes after ignition has taken place.
2. Apparatus as claimed in claim 1, characterized in that the generator is coupled to a resonance circuit of which the impedance of the lamp forms a part.
3. Apparatus as claimed in claim 1 or 2, characterized in that the piezoelectric transformer is adapted to supply sufficient power to the lamp to 'take over' the power supply thereof during the phase directly following the ignition.
4. Apparatus as claimed in claim 1, 2 or 3, characterized in that the generator is adapted to initially generate an AC voltage which coincides substantially with the resonance frequency of the piezoelectric transformer.
, 5. Apparatus as claimed in one of the preceding claims, characterized in that the apparatus further comprises a control circuit for the control of the generator and which is adapted to gradually change the frequency of the generator after ignition has taken place.
6. Power supply apparatus for a high pressure gas discharge lamp, comprising an ignition apparatus as claimed in any of the preceding claims.
7. Power supply apparatus as claimed in claim 6, characterized in that the piezoelectric transformer as adapted to be used during the steady state of the lamp.
PCT/IB2003/005743 2002-12-20 2003-12-03 Apparatus for igniting a high pressure gas discharge lamp WO2004057930A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003303172A AU2003303172A1 (en) 2002-12-20 2003-12-03 Apparatus for igniting a high pressure gas discharge lamp

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP02080517.2 2002-12-20
EP02080517 2002-12-20

Publications (1)

Publication Number Publication Date
WO2004057930A1 true WO2004057930A1 (en) 2004-07-08

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PCT/IB2003/005743 WO2004057930A1 (en) 2002-12-20 2003-12-03 Apparatus for igniting a high pressure gas discharge lamp

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0706306A2 (en) * 1994-10-05 1996-04-10 Nec Corporation A hardware arrangement and method of driving a piezo-electric transformer
US6208064B1 (en) * 1998-07-29 2001-03-27 Nec Corporation Piezoelectric transformer drive circuit and drive method
US6285136B1 (en) * 1999-03-18 2001-09-04 Denso Corporation Lighting driver for discharge lamp
US20020011764A1 (en) * 1999-06-07 2002-01-31 Hiroshi Nakatsuka Piezoelectric transformer, piezoelectric transformer drive circuit, piezoelectric transformer drive method and cold cathode tube drive apparatus using piezoelectric transformer
US20020014865A1 (en) * 2000-06-08 2002-02-07 Katsuhide Akimoto Discharge-lamp drive apparatus
US6353278B1 (en) * 1999-03-18 2002-03-05 Denso Corporation Piezoelectric transformer having increased voltage output
US20030137222A1 (en) * 2001-09-28 2003-07-24 Katsu Takeda Piezoelectric transformer
US20030146718A1 (en) * 2002-01-15 2003-08-07 Makoto Horiuchi Image display apparatus and method for operating the same and lamp unit for image display apparatus

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0706306A2 (en) * 1994-10-05 1996-04-10 Nec Corporation A hardware arrangement and method of driving a piezo-electric transformer
US6208064B1 (en) * 1998-07-29 2001-03-27 Nec Corporation Piezoelectric transformer drive circuit and drive method
US6285136B1 (en) * 1999-03-18 2001-09-04 Denso Corporation Lighting driver for discharge lamp
US6353278B1 (en) * 1999-03-18 2002-03-05 Denso Corporation Piezoelectric transformer having increased voltage output
US20020011764A1 (en) * 1999-06-07 2002-01-31 Hiroshi Nakatsuka Piezoelectric transformer, piezoelectric transformer drive circuit, piezoelectric transformer drive method and cold cathode tube drive apparatus using piezoelectric transformer
US20020014865A1 (en) * 2000-06-08 2002-02-07 Katsuhide Akimoto Discharge-lamp drive apparatus
US20030137222A1 (en) * 2001-09-28 2003-07-24 Katsu Takeda Piezoelectric transformer
US20030146718A1 (en) * 2002-01-15 2003-08-07 Makoto Horiuchi Image display apparatus and method for operating the same and lamp unit for image display apparatus

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Publication number Publication date
AU2003303172A1 (en) 2004-07-14

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