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WO2008129325A1 - Circuit d'entraînement pour un tube à décharge et procédé d'entraînement d'un tube à décharge - Google Patents

Circuit d'entraînement pour un tube à décharge et procédé d'entraînement d'un tube à décharge Download PDF

Info

Publication number
WO2008129325A1
WO2008129325A1 PCT/GB2008/050279 GB2008050279W WO2008129325A1 WO 2008129325 A1 WO2008129325 A1 WO 2008129325A1 GB 2008050279 W GB2008050279 W GB 2008050279W WO 2008129325 A1 WO2008129325 A1 WO 2008129325A1
Authority
WO
WIPO (PCT)
Prior art keywords
drive circuit
discharge
circuit according
voltage
discharge tube
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.)
Ceased
Application number
PCT/GB2008/050279
Other languages
English (en)
Inventor
Jan Simonsen
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.)
Cyden Ltd
Original Assignee
Cyden Ltd
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
Priority claimed from GB0717322A external-priority patent/GB2448560A/en
Application filed by Cyden Ltd filed Critical Cyden Ltd
Priority to DK08737204.1T priority Critical patent/DK2181568T3/da
Priority to ES08737204T priority patent/ES2374420T3/es
Priority to HK10110011.2A priority patent/HK1143486B/en
Priority to EP08737204A priority patent/EP2181568B1/fr
Priority to AT08737204T priority patent/ATE532388T1/de
Publication of WO2008129325A1 publication Critical patent/WO2008129325A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp

Definitions

  • the present invention relates to a drive circuit and particularly, but not exclusively, to a drive circuit for a discharge tube and a method of driving a discharge tube (also known as a discharge lamp).
  • Discharge tubes typically comprise an arrangement of electrodes in a gas, housed within an insulating, temperature resistant glass or ceramic envelope. Discharge tubes operate by ionising the gas with an applied voltage across the electrodes, to create a conduction path within the gas between the electrodes. The electrical breakdown of the gas produces a plasma discharge with the result that upon passing a current through the plasma, an intense optical pulse is generated as the free electrons within the plasma combine with the ionised gas atoms.
  • Discharge tubes are typically powered using a circuit such as that illustrated in Figure 1 of the accompanying drawings.
  • a capacitor 11 is charged by a direct current (dc) source 10.
  • the dc supply 10 and capacitor 11 are electrically connected to a discharge tube 12 by a first series of windings arranged upon the core of a transformer (not shown).
  • the discharge tube 12 does not produce any output in this initial state, since there is no conductive path through the gas 13 between electrodes 14.
  • the conductive path is created by ionising the gas within the tube 12, and this is performed using a trigger circuit 15.
  • the trigger circuit 15 induces a high voltage supply on the first series of windings (not shown) causing the gas 13 within the discharge tube 12 to break down.
  • the trigger circuit is typically controlled by a controller 16 and comprises a second series of fewer windings on the same transformer core as the first series of windings, to create a step up in voltage. This high voltage produced across the tube creates a conduction path between the tube electrodes, thereby allowing the capacitor 1 1 to discharge and thus produce an intense arc.
  • US Patent 6,965,203 discloses a method and circuitry for repetitively firing a flash lamp that is powered with a periodic voltage signal.
  • a problem with powering discharge tubes using a rectified mains supply is that the optical output is limited to a flash rate of twice the mains frequency (that is 100 Hz for a 50 Hz mains supply and 120 Hz for a 60 Hz mains supply) and the optical output from the discharge tube will only continue while the mains voltage exceeds the threshold voltage. Once the mains voltage drops below the threshold voltage, the optical output from the discharge tube will terminate.
  • a known solution to this problem is to incorporate a capacitor bank after the diode bridge in order to hold the voltage above the threshold voltage.
  • Such a capacitor bank is found to smooth the voltage supply to the discharge tube.
  • Such an arrangement is prone to fluctuations in the voltage supply 18 as shown in Figure 3 of the accompanying drawings and this manifests as a fluctuation in the optical output of the discharge arc.
  • a drive circuit for a discharge tube comprising a primary circuit and a secondary circuit both arranged to deliver power to the discharge tube, the primary circuit comprising a power supply and a first controller for controlling the delivery of power from the first power supply to the discharge tube, the secondary circuit comprising power storage means and at least one second controller for controlling the discharge of the power storage means, the second controller being arranged to selectively discharge the power storage means at intervals determined by the first controller, such that the selective discharge maintains the voltage across the discharge tube above a threshold voltage necessary to maintain a discharge arc.
  • the drive circuit according to the invention is enabled to supply a substantially constant power supply to the discharge tube.
  • the primary circuit preferably includes a diode bridge for rectifying ac mains supply.
  • a diode bridge for rectifying ac mains supply.
  • Such a diode bridge preferably provides full wave rectification of the ac mains.
  • the primary circuit includes a trigger mechanism for inducing a high voltage spike across the discharge tube to ionise the gas within the discharge tube.
  • the first controller preferably comprises a timing circuit to time the triggering of the trigger mechanism with the rectified ac mains supply.
  • a timing circuit preferably enables the trigger mechanism to be triggered only in those intervals when the rectified ac mains voltage is above a threshold voltage.
  • the threshold voltage is the minimum voltage necessary to sustain a discharge arc.
  • the rectified mains supply is continuously monitored by the first controller.
  • the secondary circuit preferably comprises a power supply such as a direct current (dc) supply for charging the power storage means.
  • a power supply such as a direct current (dc) supply for charging the power storage means.
  • the power storage means comprises at least one capacitor, such as a capacitor bank.
  • the at least one second controller preferably causes such a capacitor bank to discharge in order to compensate for the drop in voltage from the rectified ac mains supply and to maintain the voltage across the discharge tube above the threshold voltage, between duty cycles of the rectified mains voltage.
  • the discharge arc is terminated by a switch, such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET).
  • MOSFET Metal Oxide Semiconductor Field Effect Transistor
  • the first controller and the at least one second controller are arranged in electronic communication to enable synchronous discharge of the capacitor (such as the capacitor bank) with the rectified voltage.
  • the first embodiment of the present invention provides for the discharge of a substantially uniform pulse of radiation from the discharge tube for durations greater than the given duty cycle of the rectified mains voltage.
  • the power storage means preferably further comprises an inductor.
  • the at least one second controller preferably comprises a semiconductor switch, such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), which in the "OFF" state prevents the current from the power supply in the primary circuit and the charge from the capacitor bank from passing through the discharge tube.
  • MOSFET Metal Oxide Semiconductor Field Effect Transistor
  • the inductor preferably discharges across the discharge tube to maintain a discharge while the MOSFET is "OFF”. While the MOSFET is "OFF”, this further enables the capacitor bank to preferably recharge from the power supply in the primary circuit, such that it can subsequently discharge across the tube when the MOSFET is switched back "ON".
  • the switched state of the MOSFET is controlled by the first controller.
  • the source terminal of the MOSFET is connected to substantially zero voltage, or ground.
  • the second embodiment of the present invention provides for the discharge of a substantially uniform pulse of radiation from the discharge tube for durations less than a given cycle period of the power supply signal in the primary circuit.
  • a method of driving a discharge tube comprising providing a drive circuit according to the invention: powering the discharge tube using the primary circuit; - selectively powering the discharge tube using the secondary circuit at times when the first power supply is below a threshold value.
  • Figure 1 is a circuit diagram of a conventional drive circuit for a discharge tube, as described above;
  • Figure 2 is a graphical representation of the voltage waveform of the rectified ac mains supply using such a conventional circuit, as described above;
  • Figure 3 is a graphical representation of the voltage waveform of a rectified ac mains supply, following smoothing by a capacitor bank as described above;
  • Figure 4 is a circuit diagram of an exemplary drive circuit according to a first embodiment of the present invention.
  • Figure 5 is a circuit diagram of an exemplary drive circuit according to a second embodiment of the present invention.
  • a drive circuit 100 comprising a primary circuit 101 and a secondary circuit 102a, for powering a discharge tube 103.
  • the primary circuit 101 powers the discharge tube 103 and the secondary circuit 102a compensates for the variation in the rectified ac power supply in the primary circuit 101 to provide a substantially constant voltage between duty cycles of the rectified power supply.
  • the primary circuit 101 comprises a diode bridge 106, which rectifies the incoming ac mains power supply 104 from an isolation transformer 105, to provide a full wave rectified voltage signal.
  • the output of the diode bridge 106 is electrically connected to the discharge tube 103 via a single diode 107 which ensures unidirectional flow of current toward the discharge tube 103 from the power supply 104.
  • the rectified voltage is insufficient to initiate a discharge within the tube 103, since there is no conduction path between the electrodes 108 of the discharge tube 103.
  • the primary circuit 101 includes a controller 109 for controlling a trigger circuit 1 10.
  • the controller 109 receives an input signal from the output of the diode bridge 106 and monitors the variation in waveform via digital signal processing means (not shown).
  • the controller 109 includes an output for outputting a voltage as input to the trigger circuit 110.
  • the trigger circuit 110 typically includes a step-up transformer (not shown) which produces a high voltage spike across the tube electrodes 108.
  • the high potential difference created across the electrodes 108 by the trigger circuit 1 10, causes the gas 11 1 within the tube 103 to ionise, thereby reducing the impedance of the tube 103.
  • the controller 109 monitors the rectified voltage via connection 112 and outputs a signal to the trigger circuit 1 10 at a time determined by digital signal processing means (not shown) to cause the trigger circuit 1 10 to produce the voltage spike.
  • digital signal processing means not shown
  • the circuit 100 further comprises a secondary drive circuit 102a which includes a second (dc) power supply 113 arranged in series with the rectified voltage supply, and which used to charge a capacitor bank 1 14.
  • a secondary drive circuit 102a which includes a second (dc) power supply 113 arranged in series with the rectified voltage supply, and which used to charge a capacitor bank 1 14.
  • the secondary circuit further includes a second controller 1 15 arranged in electronic communication with the first controller 109 to control selective discharge of the capacitor bank 1 14.
  • the first controller 109 causes the trigger circuit 110 to produce a high voltage across the electrodes 108, causing the gas 1 11 within the tube 103 to ionise, when the rectified voltage across the tube electrodes 108 from a given duty cycle reaches the minimum value necessary to maintain a discharge arc.
  • the second controller 115 causes the capacitor bank 1 14 to progressively discharge, so as to compensate for the fall in voltage on the rectified voltage input. This maintains a constant voltage across the tube electrodes 108 and therefore a uniform discharge arc.
  • the discharge of the capacitor bank 114 is quite small. However, as the rectified voltage is reduced further from the threshold voltage, the rate of discharge of the capacitor bank 1 14 increases, so as to offset the fall in rectified voltage. As the rectified voltage begins to rise again on the next duty cycle, the capacitor bank 1 14 begins to progressively recharge from the second power supply 1 13, so that it is ready to discharge again in accordance with the fall in rectified voltage.
  • the second controller 115 monitors the first controller 109 in order to time the selective charge and discharge of the capacitor bank 1 14. In this manner, the cyclic charge and discharge of the capacitor bank 114 can be used to maintain the discharge arc for a desired time period.
  • a semiconductor switch 116 such as a metal oxide semiconductor field effect transistor (MOSFET), arranged in electrical connection with the cathode of the discharge tube 103, is switched to the "OFF" state by the first controller 109 to inhibit the flow of current between the electrodes 108 of the discharge tube 103.
  • MOSFET metal oxide semiconductor field effect transistor
  • the primary circuit 101 can be seen to comprise those components of the primary circuit according to the first embodiment.
  • the secondary circuit 102b however, comprises a first secondary controller 117 and a second secondary controller 118.
  • the first secondary controller 1 17 is arranged in electrical communication with the first controller 109 arranged in the primary circuit 101 and is arranged to discharge a capacitor bank 119 arranged in the secondary circuit 102b at a time which corresponds to a period following the application of a pulse to the trigger circuit 110.
  • the first controller 109 arranged in the primary circuit 101 monitors the variation of the rectified mains voltage and outputs a pulse to the trigger circuit 110 when the voltage level of the rectified mains voltage passes above a threshold value for producing a discharge arc, which may be 60-70V.
  • the trigger pulse causes a high voltage spike to be applied across the electrodes 108 of the discharge tube 103 which ionises the gas 11 1 within the tube 103 and thus creates a conduction path between the electrodes 108 such that the charge stored on the capacitor bank 119 can discharge across the tube 103 to produce a pulse of radiation.
  • the current which exits the tube 103 passes through an inductor coil 120 arranged in the secondary circuit 102b and subsequently though the second secondary controller 118, which may comprise a semiconductor switch, such as a MOSFET, also arranged in the secondary circuit 102b, before passing to ground.
  • the gate terminal of the MOSFET 118 is connected to the first controller 109 arranged in the primary circuit 101 , such that the first controller 109 arranged in the primary circuit 101 can control the "ON/OFF" state of the switch 118 and thus control the current passing from the capacitor bank 119 and the primary circuit 101 through the tube 103.
  • the capacitor bank 119 Following the discharge of the capacitor bank 119, which may take place over a time period significantly less that the duty cycle of the rectified mains voltage, the
  • MOSFET 1 18 is switched to the "OFF" state. This causes the magnetic field in the inductor 120 to collapse creating a high voltage spike which is applied across the electrodes 108 of the tube 103 so as to maintain a voltage above the threshold. This collapse of magnetic field causes a current to flow within the secondary circuit 102b through diode 121 and between the electrodes 108 of the tube 103 to maintain a discharge arc. During this period, the capacitor 119 is recharged by the voltage from the rectified mains voltage within the same duty cycle and once charged, the
  • MOSFET 120 is then switched back "ON", so as to discharge the capacitor 119 across the tube 103.
  • a modulated pulsed signal to the gate terminal of the MOSFET 120 once the voltage of the rectified mains signal initially passes above a threshold value, it is possible to maintain a discharge arc for a desired period of time.
  • the drive circuit of the present invention enables a discharge tube, powered from a mains supply, to produce a discharge arc of a desired period of time.

Landscapes

  • Generation Of Surge Voltage And Current (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
  • Control Of Gas Discharge Display Tubes (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)
  • Preparation Of Compounds By Using Micro-Organisms (AREA)

Abstract

La présente invention concerne un circuit d'entraînement comprenant un circuit principal et un circuit auxiliaire, agencés pour fournir l'énergie à un tube à décharge. Le circuit principal comporte une première alimentation et un premier contrôleur pour contrôler la fourniture d'énergie de la première alimentation vers le tube à décharge. Le circuit auxiliaire comporte un dispositif de stockage d'énergie, et au moins un second contrôleur pour contrôler la décharge du dispositif de stockage d'énergie. Le second contrôleur est agencé pour décharger sélectivement le dispositif de stockage d'énergie à des intervalles déterminés par le premier contrôleur, de sorte que la décharge sélective maintient la tension à travers le tube à décharge au-dessus d'une tension seuil pour maintenir un arc à décharge.
PCT/GB2008/050279 2007-04-20 2008-04-21 Circuit d'entraînement pour un tube à décharge et procédé d'entraînement d'un tube à décharge Ceased WO2008129325A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DK08737204.1T DK2181568T3 (da) 2007-04-20 2008-04-21 Drivkredsløb til et udladningsrør samt fremgangsmåde til drift af et udladningsrør
ES08737204T ES2374420T3 (es) 2007-04-20 2008-04-21 Circuito de excitación para un tubo de descarga y método de excitación de un tubo de descarga.
HK10110011.2A HK1143486B (en) 2007-04-20 2008-04-21 Drive circuit for a discharge tube and a method of driving a discharge tube
EP08737204A EP2181568B1 (fr) 2007-04-20 2008-04-21 Circuit d'entraînement pour un tube à décharge et procédé d'entraînement d'un tube à décharge
AT08737204T ATE532388T1 (de) 2007-04-20 2008-04-21 Ansteuerschaltung für eine entladungsröhre und verfahren zum ansteuern einer entladungsröhre

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
DKPA200700578 2007-04-20
DKPA200700578 2007-04-20
DKPA200700582 2007-04-20
DKPA200700582 2007-04-20
GB0717322.2 2007-09-06
GB0717322A GB2448560A (en) 2007-04-20 2007-09-06 Drive circuit for discharge tube

Publications (1)

Publication Number Publication Date
WO2008129325A1 true WO2008129325A1 (fr) 2008-10-30

Family

ID=39671491

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2008/050279 Ceased WO2008129325A1 (fr) 2007-04-20 2008-04-21 Circuit d'entraînement pour un tube à décharge et procédé d'entraînement d'un tube à décharge

Country Status (5)

Country Link
EP (1) EP2181568B1 (fr)
AT (1) ATE532388T1 (fr)
DK (1) DK2181568T3 (fr)
ES (1) ES2374420T3 (fr)
WO (1) WO2008129325A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4486691A (en) * 1980-07-02 1984-12-04 Beggs William C Sequential capacitive discharge circuit for flash lamps
US6193711B1 (en) 1997-12-12 2001-02-27 Coherent, Inc. Rapid pulsed Er:YAG laser
US20050168158A1 (en) * 2001-03-01 2005-08-04 Palomar Medical Technologies, Inc. Flash lamp drive circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4486691A (en) * 1980-07-02 1984-12-04 Beggs William C Sequential capacitive discharge circuit for flash lamps
US6193711B1 (en) 1997-12-12 2001-02-27 Coherent, Inc. Rapid pulsed Er:YAG laser
US20050168158A1 (en) * 2001-03-01 2005-08-04 Palomar Medical Technologies, Inc. Flash lamp drive circuit

Also Published As

Publication number Publication date
DK2181568T3 (da) 2012-02-13
HK1143486A1 (en) 2010-12-31
EP2181568A1 (fr) 2010-05-05
EP2181568B1 (fr) 2011-11-02
ES2374420T3 (es) 2012-02-16
ATE532388T1 (de) 2011-11-15

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