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
  • H05B41/2825—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 bridge converter in the final stage
  • H05B41/2828—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 bridge converter in the final stage using control circuits for the switching elements
• • 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
  • H05B41/36—Controlling
  • H05B41/38—Controlling the intensity of light
  • H05B41/39—Controlling the intensity of light continuously
  • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
  • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
  • H05B41/3925—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by frequency variation

Definitions

• the present invention relates to a circuit arrangement for operating a discharge lamp with an inverter which is designed to provide at its output a signal with a predeterminable frequency, at least one terminal for the discharge lamp, at least one lamp inductor connected between the output of the inverter and the at least one connection for the discharge lamp is coupled, at least one capacitor, which is coupled to the lamp inductor, a drive device for driving the inverter with the signal with the predetermined frequency, a control device for controlling a dependent of the lamp current control parameter to a predetermined value due to a change the predeterminable frequency, wherein the regulating device has a first time constant, wherein the discharge lamp has a second time constant, with which they respond to a change of the predeterminable frequency with a change of a dependent on the lamp current Pa Due to the temperature-dependent UI characteristic of the discharge lamp and the frequency-dependent UI characteristic of a resonant circuit comprising at least the capacitor and the lamp inductor, the circuit arrangement has at least one region with a first and a second
• the time constant of the lamp was 10 ⁇ s
• the control device was designed as a digital control device with a time constant of 50 ⁇ s.
• maintaining the frequency f constant, in accordance with keeping the voltage Uf constant results in a discharge of the discharge lamp, as can be seen from the return of the current I L and an increase in the voltage U L.
• the control device only reacts with a frequency reduction when the discharge lamp has already gone out. This leads to a renewed ignition of the -A-
• a control device which is suitable for operating the lamp in the unstable operating range is characterized in the prior art in that the regulation takes place more quickly than the lamp can react due to its inertia.
• a control device for operating the discharge lamp for example at the point Pio-i, initially increased the frequency f starting from the operating point P10-2. Then, due to its inertia, the discharge lamp does not decrease abruptly, but continuously, ie with a certain time constant, the lamp current and its power to the working point P 10 - to achieve.
• control device falls below the set for the point P 10 - 1 lamp current, it lowers the frequency until the lamp current to be set is exceeded again and thus the frequency is increased again. If the control device is fast enough, the discharge lamp is operated dynamically within a small working range around the operating point Pio-i. With decreasing control speed, the working area thus traversed becomes ever larger, until finally two stable operating points are achieved. The larger this work area becomes, the greater the crest factor of the lamp current, which leads to premature aging of the lamp. In addition, flicker and flicker appear.
• the control device If the control device is fast enough, it can be achieved that the lamp is in the desired working range between two stable, depending on the frequency f working point. operated.
• the desired desired working range can thus be set if a control device is used whose time constant is significantly smaller than the time constant which is predetermined by the discharge lamp, ie with which the discharge lamp to a change in frequency with a change in the lamp current or the Lamp power reacts.
• An alternative to preventing the lamp from operating or operating in the unstable operating range is that the dimming range of the discharge lamp is limited downwards, for example to 3, 10 or 30% of the maximum power converted in the lamp.
• the object of the present invention therefore consists in developing the circuit arrangement mentioned at the beginning or the method mentioned at the outset in such a way that the operation of a discharge lamp in the desired working range is also made possible with slower and thus more cost-effective control devices.
• the present invention is based on the recognition that the operation with slow control devices, ie with control devices having a time constant which is much the same as the time constant, by the Given the response time of the discharge lamp is predetermined for a Frequenzand- tion, when the drive device is designed, the frequency at which the inverter is operated, continuously, ie continuously and / or in jumps, to vary in such a way that the Circuit arrangement is operated in the unstable work area. It is further based on the finding that the articular frequency changes quasi an artificially slowing the reaction time of the lamp in the range of unstable desired working range is achieved, whereby slower control devices more time to determine the manipulated variable is maintained before one of the undesirable stable operating points is reached.
• the manipulated variables of the regulating device can be, for example, the lamp power P, the lamp voltage U L or the lamp current I L.
• the control device preferably regulates the corresponding mean values with regard to the temporal variation of the frequency.
• the optimum time periods with which the inverter is driven with the respective frequency depend on the response time of the lamp. If, as mentioned, the time constant of the lamp is smaller than the time between two frequency changes, the stable operating points can be set. If the time constant of the lamp is greater than the time between two frequency changes, the stable operating points are no longer reached, whereby the operating range of the lamp increases as the rate of change increases. Density, ie decreasing duration, during which the respective frequency is applied, moves ever closer to the target working point within the unstable work area. With respect to the unstable operating point Pio-i, see Fig. 1, this is no longer taken fixed, but constantly exceeded and fallen below. In other words, if the changes happen so quickly that the lamp can no longer follow them due to their inertia, tilting to a stable operating point is no longer possible.
• the center frequency is changed in a simple exemplary embodiment, in which switching back and forth between two frequencies, which then affects the two actual operating frequencies with which the lamp is operated.
• the drive device is accordingly designed to operate the discharge lamp at a first predeterminable frequency at least during a first period of time and at a second predeterminable frequency for at least a second period of time.
• the drive device is designed to operate the discharge lamp during at least one further time duration with at least one further predeterminable frequency. This includes the case of operating the discharge lamp at a plurality of predeterminable frequencies, the associated time periods being equal or unequal. It is preferable if the periods are repeated cyclically.
• the drive device can also be designed to keep the specific, predetermined frequencies associated durations constant during operation of the discharge lamp or to vary.
• the drive device is preferably designed to vary the predefinable frequency (s) in such a way that operation of the discharge lamp in a stable operating point is prevented. This will allow the lamp to operate in the desired unstable working range between the two stable operating points.
• the time duration (s) can be varied accordingly so that operation of the discharge lamp in a stable operating point is prevented.
• the drive device is designed to vary the predefinable frequency (s) and / or the duration (n) in such a way that the set operating point moves dynamically between the first and the second stable operating point.
• the control parameter of the control device is preferably the actual value of the lamp current and / or the actual value of the lamp power and / or the actual value of the lamp voltage.
• the control device is preferably designed to supply a dimming signal which corresponds to a nominal value of the lamp current or the lamp power or the lamp voltage, wherein the control device is assigned a table or a formulaic relationship, so that on the basis of at least the dimming signal and the actual value of the lamp current or Lamp power or the lamp voltage the predetermined frequencies and / or the predetermined periods are available. It is special preferred if the table or formula relationship continues to take into account the crest factor.
• control device is designed to work with a step size of 10 ⁇ s and greater, in particular with a step size of 50 ⁇ s.
• FIG. 1 shows a UI characteristic field in which three temperature-dependent UI characteristics of a discharge lamp and a plurality of frequency-dependent UI characteristics of a resonant circuit of a circuit arrangement known from the prior art for operating a discharge lamp are shown;
• FIG. 2 shows the time profile of the lamp current I L , the lamp voltage U L and a voltage U f correlated with the frequency f in a circuit arrangement known from the prior art; 3 shows a schematic representation of the structure of an embodiment of a circuit arrangement according to the invention;
• Fig. 5 shows the time course of the lamp current I L , the lamp voltage U L and a frequency f correlated voltage U f in one embodiment of a circuit arrangement according to the invention.
• Fig. 3 shows a schematic representation of the structure of an embodiment of a circuit arrangement according to the invention.
• the so-called intermediate circuit voltage U zw is applied to the series connection of the two switches S 1, S 2 in a half-bridge arrangement.
• this is approximately 100 to 450 V and is usually generated from the mains voltage via a rectifier and a smoothing capacitor.
• the half-bridge center HB is connected to a first terminal of the lamp LA via a lamp inductor L D.
• a capacitor C 1 is connected to this connection, which forms a resonant circuit together with the lamp inductor L D and is designed, in particular, to ignite the lamp LA.
• the current flowing through the lamp LA is denoted by I L , the voltage drop across the lamp is U L.
• the other terminal of the lamp LA is connected via the primary inductance Ll of a transformer Tr on the one hand via a NEN coupling capacitor C ⁇ i connected to the intermediate circuit voltage U zw , on the other hand via a coupling capacitor C ⁇ 2 with a reference potential, in this case ground.
• the first lamp terminal is connected via a first voltage divider comprising the resistors Rl and R2, the second terminal of the lamp LA via a second voltage divider comprising the resistors R3 and R4 to the reference potential.
• the respective taps of the two voltage dividers are connected to a measuring device 10 for determining a voltage, which is correlated with the lamp voltage U L.
• the measuring device 10 can furthermore be designed to determine the power P converted in the lamp from the lamp current I L and the lamp voltage U L.
• the crest factor can be determined from the lamp current I L.
• One of several alternatives for determining the lamp output is to couple a shunt resistor between the switch S2 of the half-bridge arrangement and the reference potential and to calculate the power converted in the lamp from the voltage dropping across this shunt resistor.
• a reference value device 12 provides a setpoint value for the lamp current I L and / or for the lamp voltage U L and / or for the lamp power P, specifically as a function of a dimming signal S 0 supplied via an interface.
• FIG. 4 shows the time sequence of the frequency variation for a simple exemplary embodiment.
• the switches Sl, S2 of the half-bridge are operated at a frequency I 1 during the time t 2 minus ti at a frequency f 2 .
• this variation of the frequency is reflected in the time course of the lamp current I L :
• the lamp current I L has the frequency f 1 , during the time t 2 minus t i the higher frequency f 2 on.
• both the time periods as well as the frequencies fi and f 2 can ti and t 2 are varied.
• the invention includes other frequencies and corresponding time periods.
• a constant variation of the frequency (corresponding to each individual frequency infinitesimal small associated time) is also included.
• 5 shows the time profile of the lamp current I L , the lamp voltage U L and a voltage Uf, which is correlated with the frequency f, for an exemplary embodiment of a circuit arrangement according to the invention.
• the time course of the voltage U f is shown as triangular, it is actually rectangular. The triangular shape is due to the limited slope of the D / A converter used in the embodiment. A comparison with FIG.
• the drive device (18) is designed to vary the predefinable frequency during operation of the discharge lamp (LA) in such a way that the circuit arrangement is operated in the unstable operating range. It also relates to a method for operating a discharge lamp (LA) on such a circuit arrangement.

Landscapes

• Circuit Arrangements For Discharge Lamps (AREA)
• Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=38197921

Family Applications (1)

Country Status (8)

Family Cites Families (10)

• 2006
  • 2006-04-13 DE DE102006017521A patent/DE102006017521A1/de not_active Withdrawn
• 2007
  • 2007-04-05 CN CN200780013104.4A patent/CN101422086B/zh not_active Expired - Fee Related
  • 2007-04-05 US US12/226,278 patent/US8098020B2/en not_active Expired - Fee Related
  • 2007-04-05 EP EP07727864A patent/EP2005804B1/fr not_active Not-in-force
  • 2007-04-05 CA CA002647959A patent/CA2647959A1/fr not_active Abandoned
  • 2007-04-05 AT AT07727864T patent/ATE511341T1/de active
  • 2007-04-05 WO PCT/EP2007/053396 patent/WO2007118808A1/fr not_active Ceased
  • 2007-04-11 TW TW096112689A patent/TW200746909A/zh unknown

Non-Patent Citations (1)

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