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
  • H05B41/295—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 and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps

Definitions

• the present invention relates to an electronic ballast for gas discharge lamps.
• the invention relates to an electronic ballast for gas discharge lamps according to the preamble of claim 1
• the electronic ballast comprises a rectifier 1 that can be connected to a supply voltage source, for example a full-bridge or multi-way rectifier to an output of the Rectifier 1 is connected to a circuit arrangement comprising at least a first capacitance 2 and at least a second capacitor 3.
• This capacitor circuit arrangement is connected to a series circuit comprising two controllable switches 4 and 5 and a Giattungs electrolytic capacitor.
• the actual load circuit with the gas discharge lamp 8 to be controlled and a resonance circuit with a resonance inductance 6 and a resonance capacitor 7 connected in parallel with the gas discharge lamp can also be connected.
• a D rossel coil 1 1 between the rectifier 1 and the first capacitor 2 also be present, a diode 12 between the first capacitor 2 and the first switch 4 is necessary
• the excess voltage at the resonance capacitor 7 can be used to ignite the gas discharge lamp by changing the frequency of the AC voltage, the operating point for the gas discharge lamp is set, and so these are dimmed.
• the following problems occur in the circuit shown in FIG.
• the second capacitor 3, which acts as a control capacitor, fulfills two functions with the rectifier 1, the return capacitor 2 and the optional choke 11 as a harmonic filter, which is intended to keep the harmonic radiation into the supply network as low as possible.However, this results in different or conflicting requirements for the dimensioning of the control capacitor 3, so that when it is dimensioned, there are either reductions in the co-determination of the resonance frequency or the harmonic filter effect must be made. This applies in particular during the preheating and ignition of the gas discharge lamp
• Fig. 6 shows that a current I is fed in at the connection point between the two capacitors 2 and 3, which current can assume very different values from the start of the lamp to its operation, as a result of which the operating point of the entire circuit arrangement is shifted
• 8 can only work optimally on a single operating point dependent on the dimensioning of the capacitors 2 and 3 and the series resonance circuit 6 and 7 and the smoothing capacitor 13, i.e.
• the lamp burns satisfactorily only at this single operating point and the harmonic content reflected back into the supply network is determined within a certain range Limits kept in particular when igniting or preheating the lamp 8 flows through the resonance inductance 6 and the resonance capacitor 7, a strong resonance current I in the connection point between the two capacitors 2 and 3, so that the voltage across the capacitor 3 increases significantly above that value, be i that the previously described optimal working point is available
• the present invention is based on the object of specifying an electronic ballast in which no compromises have to be made in the dimensioning of the second capacitor 3 and in which the current I fed in at the connection point between the capacitors 2 and 3 when igniting or preheating the gas discharge lamp 8 is kept as low as possible
• FIG. 6 shows an exemplary embodiment of a known electronic ballast
• FIG. 1 shows a first exemplary embodiment of the present invention.
• the components already explained with reference to FIG. 6 are provided with the same reference numerals, so that a repeated description of these components can be dispensed with
• the resonance capacitor 7 is no longer parallel to the gas discharge lamp 8, but is connected in series with one of two coupled windings 9, 10 of a transformer. In FIG. 1, these two windings 9 and 10 coupled in opposite directions It is pointed out, however, that the sense of coupling is irrelevant for the effect to be sought here.
• the left heating filament of the gas discharge lamp is connected to ground via the capacitor 3 in alternating current.
• the coil resistance of the left heating coil is connected by the transformer in parallel to the right winding 10 of the transformer, so that the resonance capacitor 7 is connected to the right heating coil of the gas discharge lamp 8 via the transformed coil resistance of the left heating coil.
• the resonance capacitor 7 is above the lamp 8 and thus, as in the known case, the voltage increase at the resonance capacitor 7 for igniting the Gas discharge lamp 8 can be used, but when the lamp 8 is heated or ignited, the resonance current is not fed directly to the connection point between the two capacitors 2 and 3.
• the capacitor 3 no longer co-determines the resonance frequency of the series resonance circuit, so that it can only be dimensioned taking into account the harmonic reflection.
• the problems described in connection with the known circuit using FIG. 6 no longer occur.
• FIG. 2a shows a variant of the first exemplary embodiment according to the invention shown in FIG. 1 for two gas discharge lamps 8 and 16, the essential components correspondingly being duplicated.
• a further transformer with coupled windings 17 and 18 and a further load circuit with the second lamp 16 and a further resonance inductance and a further resonance capacitance 15 are thus provided for the second gas discharge lamp 16.
• the optional choke coil 11 has been omitted in FIG. 2a.
• a measuring resistor 19 is provided in series with the resonance capacitors 7 and 15 and the second switch 5. With the help of this resistor 19, both the Are current and the preheating current can be measured. The Are current determines the brightness of the lamp, so that a measurement of this current is of great importance for the monitoring and regulation of the lamp brightness.
• the resonance inductors 6 and 14 and the resonance capacitors 7 and 15 are at the same potential since they are connected to one another.
• the Are current flows through the measuring resistor 1 during the time when the switch 5 is closed and can therefore be measured at this point in time via the voltage drop across the measuring resistor 19.
• the preheating current flows when the switch 5 is open via the resonance capacitors 7, 15, the resonance inductors 6, 14 and the closed switch 4.
• the preheating current is of particular interest in the preheating phase, so that the circuit according to the invention both in the preheating phase and in the operating phase on one and the same component, namely the measuring resistor 19, the parameter of interest can be measured if the measuring time is correctly selected.
• the measurability of the parameters of interest in each case via the resistor 19 can generally be transferred to all circuit variants in which the Resonance capacitor is freely accessible, ie in an analogous manner, for example, also to the circuit shown in FIG. 1, FIG. 26 or FIG. 5
• FIG. 2b shows a further variant of the exemplary embodiment shown in FIG. 1 for two gas discharge lamps, a separate transformer being dispensed with for the second gas discharge lamp 16 and instead this lamp being connected on the one hand to the second winding 10 of the transformer of the first lamp 8 and on the other hand to one own winding 17 is provided, which is coupled to the windings 9 and 10 of the transformer of the first gas discharge lamp 8.
• the two gas discharge lamps are preceded by a balancing element, which advantageously consists of a balancing transformer with coils 20 and 21 coupled in opposite directions.
• the balancing transformer is used to adjust the lamp currents of the two gas discharge lamps 8 and 16, so that both lamps burn evenly during operation.
• the two windings 20 and 21 of the balancing transformer are flowed through in opposite directions by the lamp currents of the two gas discharge lamps, so that the balancing transformer carries the lamp currents is magnetized in opposite directions
• FIGS. 2a, b is also operated like the first gas discharge lamp 8, so that the advantageous effects of the invention described with reference to FIG. 1 also apply to the second gas discharge lamp 16
• Fig. 3 shows a second embodiment of the invention, wherein a transformer with three coupled windings 9, 10 and 22 is used.
• This exemplary embodiment is particularly advantageous for radio interference suppression, since the gas discharge lamp 8 is set to ground via its left connection and the central transformer winding 22
• This exemplary embodiment is advantageous for the measurability of voltages or currents at the individual circuit points, since these variables can be measured directly in this exemplary embodiment, while in the circuits of FIGS. 1 and 6 only these variables can be measured as difference values
• three transformer windings are provided in order to supply the connection point between the capacitors 2 and 3 with as little or no current as possible in the case of preheating and in the event of ignition Transfer windings 22, 10, which is caused by the current flowing through the resonance inductance 6 and through the middle and right-hand transmission windings 22, 10, since these have the same number of turns.
• the current flowing through the gas discharge lamp 8 is transferred to the left-hand transmission winding 9 transmitted and fed to the connection point between the two capacitors 2 and 3.
• the object according to the invention is achieved in that the lowest possible current is supplied to the connection point in preheating and ignition mode.
• the capacitor 3 does not determine the resonance frequency of the series resonance circuit and thus can only be dimensioned taking into account the avoidance of harmonic radiation into the supply network.
• the number of turns of the left transmission winding 9 can be designed independently of that of the other two windings 22 and 10, so that the current to be fed to the connection point between the capacitors 2 and 3 can be set in particular via this winding 9
• an isolating capacitor 23 is additionally provided.
• FIG. 6 the center point of the half bridge between the switches 4 and 5 before the gas discharge lamp 8 is ignited by the capacitors 7 and 3 and after the ignition only by the capacitor 3 in terms of AC current from ground 3, this is not the case in the circuit shown in FIG. 3 after the ignition, so that the isolating capacitor 23 is provided to avoid asymmetries on the half-bridge consisting of the switches 4, 5 and the smoothing capacitor 13
• FIG. 4 shows a variant of the second exemplary embodiment for the operation of two gas discharge lamps 8 and 16. Accordingly, four transformer windings 9, 18, 22 and 10 are required in this case, the effect of the circuit according to the invention corresponding to the advantageous effect described with reference to FIG. 3 for each gas discharge lamp
• a balancing transformer with windings 20, 21 coupled in opposite directions is also provided in FIG. 4 for balancing the lamp currents of the two lamps 8, 16
• FIG. 5 shows a third exemplary embodiment of the electronic ballast according to the invention. This exemplary embodiment is a further development of the exemplary embodiment shown in FIGS. 1 and 2, but in addition to the two coupled
• Uebertragerwicklept 9 and 10 a third coupled Uebertragerwick 22 provided
• the measuring resistor 19 is in turn present in series with the resonance capacitor 7 and the lower controllable switch 5, so that the resonance capacitor is connected to the left connection of the gas discharge lamp 8 via the resistor 19, which can be neglected in terms of its size, and the capacitor 3, and the resonance capacitor 7
• the gas discharge lamp 8 can thus also be ignited in the circuit shown in FIG. 5 by increasing the resonance at the resonance capacitor 7.
• a certain voltage is generated via the resonance capacitor 7, which is also applied to the lamp 8 via ground
• the transformer receives this voltage, which drops across the resonance capacitor 7, with its primary winding 22 and converts it into a corresponding heating voltage on the two filaments
• the current is transformed up from the primary winding 22 into the spiral windings 9 and 10, so that, conversely, the spiral resistances are transformed up into the primary winding 22 and a low alternating current occurs in the primary winding 22 due to the high resistance the heating or ignition phase only a very small current is fed to the connection point between the capacitors 2 and 3, which solves the task originally set
• additional free-wheeling or overshoot diodes 24 and 25 are advantageously additionally provided, each of which bridges one of the two controllable switches 4 and 5, which are preferably MOS field effect transistors

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• Circuit Arrangements For Discharge Lamps (AREA)
• Discharge Lamp (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=7803969

Family Applications (1)

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• 1996
  • 1996-08-28 DE DE19634850A patent/DE19634850A1/de not_active Withdrawn
• 1997
  • 1997-07-30 AT AT97942836T patent/ATE214863T1/de not_active IP Right Cessation
  • 1997-07-30 AU AU44530/97A patent/AU4453097A/en not_active Abandoned
  • 1997-07-30 EP EP97942836A patent/EP0922376B1/fr not_active Expired - Lifetime
  • 1997-07-30 WO PCT/EP1997/004150 patent/WO1998009483A1/fr not_active Ceased
  • 1997-07-30 DE DE59706691T patent/DE59706691D1/de not_active Expired - Fee Related
  • 1997-08-14 ZA ZA9707311A patent/ZA977311B/xx unknown

Non-Patent Citations (1)

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