JP5122838B2 - Discharge lamp lighting device and lighting fixture - Google Patents

Description

  The present invention relates to a discharge lamp lighting device capable of lighting a plurality of discharge lamps at a high frequency and continuously adjusting light to a low luminous flux and a lighting fixture using the same.

  Conventionally, when an inverter-type lighting device capable of continuously dimming a plurality of discharge lamps over a wide range is used to turn on the same type of discharge lamps, the light output of each discharge lamp is not normal. Although it should be the same, it is generally known that there is a difference in light output due to variations in circuit elements, variations in characteristics of discharge lamps, and the like. When the light output is large, for example, when the discharge lamp is lit near the rated lighting, the difference in light output is less noticeable between the discharge lamps. This is because the lamp brightness is high at the rated output of the discharge lamp and a minute light output difference cannot be recognized with the eyes, so that a small difference does not cause a problem. However, when dimming deeper than when the discharge lamp is rated on (for example, the light output ratio is 5% or less), the lamp brightness decreases and even a small difference in light output can be recognized by the eyes. The difference in the light output between the discharge lamps becomes conspicuous.

  In order to solve this problem, for example, a lighting device as shown in FIG. 10 is proposed in Japanese Patent No. 3291852 (Patent Document 1). In this apparatus, two discharge lamps 11 and 12 are connected in parallel to the output of the high-frequency power source 10 via a balancer T. In the case of such a parallel lighting system using the balancer T, the balancer T supplies a sufficient starting voltage to both the discharge lamps 11 and 12 in addition to the function of making the lamp currents of the two lamps equal. There is a function to do. That is, normally, when starting the discharge lamp, one of the discharge lamps starts to discharge first due to variations in the starting voltage of the two discharge lamps 11 and 12. At this time, since the equivalent impedance of the lit discharge lamp is reduced, if there is no balancer T, a voltage sufficient to start the other discharge lamp cannot be obtained, and only one of the discharge lamps can be obtained. It can only be lit. Here, by inserting the balancer T, when one of the discharge lamps starts to discharge first, a current flows through the winding connected to the discharge lamp on the other side of the balancer T. A voltage is induced in the winding and a sufficient starting voltage can be supplied to the other discharge lamp.

  However, the optical output difference is caused by the characteristics of the balancer T (mainly the difference between the inductance values of the two windings). When two discharge lamps of the same type are lit, the lamp currents of the two discharge lamps must be made equal, so the inductance values of the two windings of the balancer must be designed to be equal. However, depending on the structure of the balancer, there may be a large difference or variation in the inductance values of the two windings, which causes a difference in optical output.

  In Patent Document 1, as shown in FIG. 11, the balancer T generates almost the magnetic flux passing through the two windings N1 and N2 by alternately winding the first winding N1 and the second winding N2. The difference between the inductance components is reduced by making them equal. The bobbin B is mounted on an E-type core Ec, and forms a magnetic circuit by joining the I-type core Ic via a gap paper Gp. By connecting the discharge lamps 11 and 12 in parallel to the output of the high-frequency power supply 10 through the balancer T configured in this way, the circuit configuration is simple and the difference in the light output of each discharge lamp can be reduced. it can.

  FIG. 12 shows frequency characteristics of output voltage of the discharge lamp lighting device of FIG. Since the discharge lamps 11 and 12 have not yet started discharging at the time of pre-heating, the equivalent impedance of the discharge lamp is usually a very large value (Rla≈∞) as shown by the curve shown in FIG. . fr is a no-load resonance frequency. Here, if the oscillation frequency at the time of pre-heating is fy, the operating point is point A in FIG. The secondary voltage Vy at this time is set so as to be a low voltage that does not cause a cold start of the discharge lamp.

Next, when the pre-heating time has elapsed, the oscillation frequency is lowered and the output voltage is increased to a voltage sufficient for starting the discharge lamp. The oscillation frequency at this time is assumed to be fstr. The operating point is point B in FIG. The oscillation frequency fstr is set so that the secondary voltage Vs at this time is equal to or higher than the starting voltage of the discharge lamp. When both discharge lamps start to discharge, the equivalent impedance of the lamps becomes small, and the frequency characteristics of the output voltage at the time of lighting change to a curve shown in FIG.
Japanese Patent No. 3291852

  In the technique of Patent Document 1, considering the case where deep light control is performed to a light output ratio of 5% or less, or when the ambient temperature decreases and the illuminance of the discharge lamp decreases, the inductance value of the balancer T is set to two. It is necessary to sufficiently increase the optical output difference between them to a level where it is not noticeable. However, if the inductance value of the balancer T is too large, the light output difference between the discharge lamps 11 and 12 is reduced. For example, when one discharge lamp does not start normally when starting the discharge lamp, Since current is generated only in the discharge lamp, the equivalent circuit of the resonance circuit including the discharge lamp becomes the circuit shown in FIG. 7B, and a new circuit different from that in the preceding preheating is generated by the inductance L1 of the balancer winding and the capacitor C3. A resonant circuit is generated. The frequency characteristic of the output voltage of the device when only one lamp is lit is a curve shown in FIG. At this time, the operating point at the oscillation frequency fstr at the start changes from the point B to the point B ′, and an excessively high voltage stress exceeding the starting voltage required for the other discharge lamp occurs. Therefore, when the inductance value of the balancer T is increased in order to reduce the light output difference at the time of deep dimming, there is a possibility that the circuit element is destroyed by this high voltage stress.

  The present invention is an inverter-type lighting device capable of continuously dimming over a wide range, and can reduce the light output difference of the discharge lamp even when the light is dimmed to a low luminous flux or when the ambient temperature is lowered, and the stress can be reduced. It is an object of the present invention to provide a discharge lamp lighting device that can perform stable dimming that can be reduced.

In order to solve the above-mentioned problem, the invention of claim 1 is connected to a DC power source 1 and converts an DC voltage into a high frequency voltage as shown in FIG. A plurality of discharge lamps 11 and 12 are connected in parallel via a balancer T between a resonance circuit 3 connected and having at least one inductor CH and a capacitor C2, and both ends of the resonance capacitor C2 in the resonance circuit 3. In a discharge lamp lighting device including a load circuit 40 and an oscillation control unit 5 that performs start-up and dimming control of the discharge lamps 11 and 12 by changing the oscillation frequency of the inverter unit 2, the balancer T and each discharge lamp The capacitive element C1 is connected between the connection paths to the first and second terminals 12 and 12, and the balancer T is generated by the resonance action of the inductance of the balancer T and the capacitive element C1. Combined impedance when occurring dimming lower limit lit between windings Ri der least 7 times more synthetic impedance at full lighting, the inductance of the balancer T, the parallel resonance frequency fo of the capacitive element C1, tone The relationship of the oscillation frequency fdim of the inverter unit 2 at the time of light lower limit lighting is 0.8 × fdim ≦ fo ≦ 1.6 × fdim, and the parallel resonance frequency fo between the inductance of the balancer T and the capacitive element C1. And the oscillation frequency fstr of the inverter unit 2 at the start of the discharge lamp is fo ≧ 1.3 × fstr, and the balancer T is composed of a transformer having a plurality of windings, each winding being a single It is characterized by being constituted by layer aligned winding .

Invention of Claim 2 is a lighting fixture provided with the discharge lamp lighting device of Claim 1 .

According to the first aspect of the present invention, the capacitive element is connected in parallel between the connection paths of the balancer and the plurality of discharge lamps, and the balancer winding and the winding of the balancer are resonated by the resonance action of the capacitive element. By making the combined impedance at the time of dimming lower limit lighting occurring at least 7 times or more the combined impedance at the time of full lighting, the light output difference of each discharge lamp at low temperature and low luminous flux can be reduced. Moreover, since the inductance of the balancer can be set to a relatively small value, the balancer can be reduced in size . Further, the relationship between the resonance frequency fo due to the inductance value of the capacitor as the capacitive element and the balancer and the oscillation frequency fdim of the inverter unit at the time of lighting control lower limit lighting of the discharge lamp is 0.8 × fdim ≦ fo ≦ 1.6 × fdim. As a result, the illuminance difference between the discharge lamps at low temperatures and low luminous flux can be reduced. Further, since the relationship between the resonance frequency fo due to the inductance value of the capacitor and the balancer as the capacitive element and the operating frequency fstr of the inverter unit at the start of the discharge lamp is fo ≧ 1.3 × fstr, the stress at the start The voltage can be reduced. Furthermore, by using a single-layer aligned winding with little parasitic capacitance between the windings, it is possible to reduce the influence of variations in parasitic capacitance between the windings .

According to the second aspect of the present invention, in a lighting fixture that lights a plurality of discharge lamps in parallel, a difference in light output between the discharge lamps at a low temperature and a low luminous flux can be reduced.

(Embodiment 1)
Hereinafter, a discharge lamp lighting device according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 1 shows a circuit diagram of the present embodiment, and FIG. 2 shows the balancer winding by the parallel resonance action of the balancer T and the capacitive element C1 connected between the connection paths of the balancer T and each discharge lamp. The frequency characteristic of the synthetic impedance produced between lines is shown. FIG. 3A shows the effective value characteristics of the lamp current and the lamp voltage when a 4 ft straight tube fluorescent lamp (FHF32) is dimmed at an ambient temperature of 25 ° C. and 0 ° C. (B) shows the negative resistance value characteristic, that is, the slope of the effective value characteristic of the lamp current and lamp voltage shown in FIG. First, the configuration of the discharge lamp lighting device will be described with reference to FIG.

  The discharge lamp lighting device of the present embodiment includes an inverter unit 2 composed of a pair of switching elements Q1 and Q2 connected to a half bridge for inputting a DC power source 1, a drive circuit 6 for driving the switching elements Q1 and Q2, and this An oscillation control unit 5 that supplies an oscillation signal to the drive circuit 6 is provided. The switching elements Q1 and Q2 are alternately switched by the drive circuit 6 to convert the DC voltage of the DC power supply 1 into a high frequency voltage. A choke coil CH, a capacitor C2, and a DC cut capacitor C3 constituting the resonance circuit 3 are connected to both ends of the switching element Q2. The resonance circuit 3 may be connected to both ends of the switching element Q1. Two discharge lamps 11 and 12 are connected in parallel to the output terminal of the resonance circuit 3 via a balancer T. The oscillation frequency of the inverter unit 2 is determined by the oscillation control unit 5, and the switching elements Q1 and Q2 are alternately switched at the oscillation frequency. Further, the discharge lamps 11 and 12 are dimmed by changing the oscillation frequency according to the dimming signal 4.

  FIG. 4 shows the frequency characteristics of the output voltage of the discharge lamp lighting device of FIG. Here, the frequency characteristic (a) at the time of full lighting, the frequency characteristic (b) at the time of dimming lighting, and the frequency characteristic (c) at no load change as shown in FIG. Therefore, by varying the oscillation frequency between ffull and fdim, the frequency characteristic of the resonance system changes from (a) to (b), and continuous dimming of the discharge lamp can be performed. For example, when an FHF32 lamp is used, the current value can be adjusted to about 25% or less by reducing the current value to a discharge lamp current ≦ about 100 mA, and the current value up to a discharge lamp current ≦ about 20 mA. Can be adjusted to a light output ratio of about 5% or less.

  Although the inverter unit 2 is a half-bridge type circuit, it may have another inverter circuit configuration such as a single-bridge type or a full-bridge type.

  FIG. 2 shows the balancer T when the inductance per winding of the balancer T is 1.3 mH and the capacitance of the capacitive element (capacitor) C1 connected between the connection paths between the balancer T and each discharge lamp is 470 pF. And the frequency characteristic of the combined impedance generated between the balancer windings due to the parallel resonance action with the capacitor C1. The parallel resonance frequency fo due to the inductance of the balancer T and the capacitance of the capacitor C1 is calculated to be about 102 kHz from the inductance of the two windings of the balancer T = 1.3 mH × 4 and the capacitance 470 pF of the capacitor C1. Therefore, as shown in FIG. 2, the combined impedance increases exponentially with the increase of the oscillation frequency due to the parallel resonance action, and when the oscillation frequency becomes higher than the parallel resonance frequency fo, the combined impedance decreases exponentially. Impedance characteristics are shown.

  Next, as shown in FIG. 3 (a), the effective characteristics of the lamp current and the lamp voltage when the 4ft straight tube fluorescent lamp (FHF32) is dimmed at an ambient temperature of 25 ° C. and 0 ° C. It shows a negative resistance characteristic peculiar to a so-called discharge lamp in which the lamp voltage rises with a decrease in. When the lamp current is about 50 mA or less at an ambient temperature of 25 ° C., the lamp voltage decreases as the lamp current decreases, but at the ambient temperature of 0 ° C., the lamp voltage continues to increase as the lamp current decreases. FIG. 3B is a plot of the slope (negative resistance value) of the lamp current-voltage characteristic for each lamp current. At an ambient temperature of 0 ° C., 25% dimming (lamp current = about 100 mA). ) Negative resistance value increases to about 4 times (= about 400Ω) of the negative resistance value (= about 100Ω) at full lighting, and negative resistance at 5% dimming (lamp current = about 20mA) It can be seen that the value increases to about 7 times (= about 700Ω) of the negative resistance value (= about 100Ω) at the time of full lighting. The output difference between the plurality of discharge lamps that are lit by the inverter circuit at the time of dimming or at a low temperature is due to an increase in the negative resistance value of the discharge lamp, and the parallel resonance action of the balancer T and the capacitor C1. By constructing so that the change in the combined impedance generated between the balancer windings is greater than the change in the negative resistance value of the discharge lamp that is lit, a plurality of lamps that are lit even during dimming or at low temperatures are used. It becomes possible to reduce the output difference generated between the lamps.

  Therefore, assuming that the minimum ambient temperature normally assumed for general lighting applications is 0 ° C., for example, when the dimming ratio is to be dimmed to about 25% or less of the light output at the time of full lighting, the inverter circuit The inductance of the balancer T and the capacitance of the capacitor C1 are configured so that the combined impedance of the balancer T and the capacitor C1 at the time of lighting the lower limit of lighting changes to about four times or more of the combined impedance at the time of full lighting according to the change of the oscillation frequency. It is necessary to do. When the dimming ratio is to be dimmed to about 5% or less of the light output during full lighting, the balancer T and the capacitor C1 during dimming lower limit lighting according to the change in the oscillation frequency of the inverter circuit. It is necessary to configure the inductance of the balancer T and the capacitance of the capacitor C1 so that the combined impedance changes to about 7 times or more of the combined impedance when all the lights are on.

  In the case where a so-called bifilar winding in which the first winding and the second winding of the balancer T are alternately wound as described in the conventional example (Patent Document 1) or a transformer having a sandwich winding configuration is used as the balancer T. Since a corresponding parasitic capacitance is generated between the windings and the combined impedance characteristic is affected, it is necessary to determine the capacitance of the capacitor C1 in consideration of the influence of the parasitic capacitance component. However, in consideration of variations in the parasitic capacitance between the windings, it is desirable to use a transformer having a single-layer aligned winding configuration with a small parasitic capacitance between the windings as the balancer T.

  In FIG. 3, the characteristic of the FHF32 (tube diameter = about 25.4 mm) fluorescent lamp is described as an example of typical characteristics of the discharge lamp, but the same applies to other discharge lamps such as a straight tube fluorescent lamp and a compact fluorescent lamp. It is known to exhibit negative resistance characteristics. Further, in some discharge lamps having a tube diameter smaller than that of the FHF 32, there are those in which the fluctuation characteristic of the negative resistance value at the time of dimming or at a low temperature is larger than the fluctuation characteristic of the FHF 32. Thereby, the improvement effect of the light output difference between discharge lamps can be obtained similarly.

  According to the present embodiment, the light output difference between the plurality of discharge lamps that are lit by the inverter circuit at the time of dimming or at a low temperature can be reduced without increasing the inductance of the balancer T more than necessary. Miniaturization is possible.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows the inductance of the balancer T, the parallel resonance frequency fo of the capacitor C1, and the current flowing through each of the discharge lamps 11 and 12 when the inductance of the balancer T is 1.3 mH and the capacitance of the capacitor C1 is changed. It shows the relationship with the difference ratio. The lighting conditions are dimming lower limit dimming ratio = 5% (inverter oscillation frequency = 100 kHz), and discharge lamps 11 and 12 have equivalent resistance values of 5 kΩ and 10 kΩ, respectively, in consideration of variations in discharge lamp characteristics at low temperatures. Replaced with a fixed resistor. The current difference ratio indicates the ratio of the difference (absolute value) between the average value of the current flowing through the discharge lamps 11 and 12 and the current flowing through one of the discharge lamps to the average current value.

  According to FIG. 5, if the parallel resonance frequency fo is in the range of 80 kHz to 160 kHz with respect to the inverter oscillation frequency = 100 kHz, the current difference ratio can be reduced to about 30% or less. It is possible to reduce the current difference ratio to a level where the optical output difference is substantially difficult to recognize.

  According to the present embodiment, the relationship between the parallel resonance frequency fo of the inductance of the balancer T and the capacitance of the capacitor C1 and the oscillation frequency fdim of the inverter unit at the time of dimming lower limit lighting is 0.8 × fdim ≦ fo ≦ 1. By configuring the inductance of the balancer T and the capacitance of the capacitor C1 so as to be 6 × fdim, the light output difference to a level that makes it difficult to visually recognize the light output difference between the discharge lamps even during dimming. Can be improved.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIG. FIG. 6 shows that when the inductance of the balancer T is 1.3 mH and the capacitance of the capacitor C1 is changed, the inductance of the balancer T, the parallel resonance frequency fo of the capacitor C1, and one of the discharge lamps 11 and 12 is discharged. Shows the relationship with the voltage generated at both ends of the other discharge lamp when the discharge is started first. An equivalent circuit at this time is shown in FIG. The lighting condition was assumed to be the inverter oscillation frequency at the start of the discharge lamp, and the inverter oscillation frequency fstr = 70 kHz.

  According to FIG. 6, when the parallel resonance frequency fo is 90 kHz or higher with respect to the inverter oscillation frequency fstr = 70 kHz at the time of starting, a voltage sufficient to start the other discharge lamp that is not lit is generated, and 1000 V It is possible to reduce component stress due to the generation of excessive voltage as described above.

  According to the present embodiment, the relationship between the parallel resonance frequency fo of the inductance of the balancer T and the capacitance of the capacitor C1 and the oscillation frequency fstr of the inverter unit at the start of the discharge lamp satisfies fo ≧ 1.3 × fstr. In addition, since the inductance of the balancer T and the capacitance of the capacitor C1 are configured, a voltage sufficient to start the other discharge lamp even when one discharge lamp starts discharging at the start of the discharge lamp. It is possible to reduce the stress applied to the components constituting the circuit.

(Embodiment 4)
A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, instead of the DC cut capacitor C3 of FIG. 1, two DC cut capacitors C4 and C5 are connected with their capacitances halved as shown in FIG. Even in such a configuration, operations and effects similar to those of the first to third embodiments can be obtained. This is because the capacity of the DC cut capacitors C4 and C5 is sufficiently larger than the capacity of the capacitor C1, so that even if the DC component is cut before passing through the balancer T, the DC component is cut after passing through the balancer T. This is because similar characteristics can be expressed.

  Further, as shown in FIG. 9, the capacitor C1 can be connected to the discharge lamp side of the DC cut capacitors C4 and C5.

  Even in this case, the capacitance of the capacitor C1 is a small capacitance such as several hundred pF, and the DC cut capacitors C4 and C5 are selected to have a sufficiently large capacitance compared to the capacitor C1. Therefore, also in this structure, the same effect as Embodiment 1-3 can be acquired.

(Embodiment 5)
FIG. 13 shows an example of the appearance of a lighting fixture equipped with the discharge lamp lighting device of the present invention. In the figure, R is a reflector, S1 and S2 are lamp 11 sockets, and S3 and S4 are lamp 12 sockets.

It is a circuit diagram of Embodiment 1 of the present invention. It is a frequency characteristic figure of the synthetic | combination impedance by the balancer and capacitive element which are used for Embodiment 1 of this invention. It is a characteristic view of the discharge lamp load used for Embodiment 1 of this invention. It is a characteristic view which shows the resonance characteristic of the load circuit of Embodiment 1 of this invention. It is a frequency characteristic figure for operation | movement description of Embodiment 2 of this invention. It is a frequency characteristic figure for operation | movement description of Embodiment 3 of this invention. FIG. 2 is an equivalent circuit diagram of the present invention and the conventional example when one lamp is not lit, (a) is an equivalent circuit diagram of the present invention of FIG. 1, and (b) is an equivalent circuit diagram of the conventional example of FIG. It is a circuit diagram of Embodiment 4 of the present invention. It is a circuit diagram of the modification of Embodiment 4 of this invention. It is a circuit diagram of a conventional example. It is a schematic sectional drawing of the balancer used for a prior art example. It is a characteristic view which shows the resonance characteristic of a prior art example. It is a perspective view which shows the external appearance of the lighting fixture carrying the discharge lamp lighting device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter part 3 Resonance circuit 5 Oscillation control part T Balancer 11 Discharge lamp 12 Discharge lamp 40 Load circuit C1 Capacitor

Claims (2)

An inverter unit connected to a DC power source for converting a DC voltage into a high frequency voltage, a resonance circuit connected to an output of the inverter unit and having at least one inductor and a capacitor, and both ends of the resonance capacitor in the resonance circuit A discharge lamp lighting device comprising: a load circuit in which a plurality of discharge lamps are connected in parallel via a balancer; and an oscillation control unit that performs start-up and dimming control of the discharge lamp by changing the oscillation frequency of the inverter unit In this case, a capacitive element is connected between the connection path between the balancer and each discharge lamp, and a combination of the balancer inductance and the balancer winding caused by the resonance action between the balancer and the dimming lower limit lighting is combined. impedance Ri der least 7 times more synthetic impedance at full lighting,
The relationship between the inductance of the balancer, the parallel resonance frequency fo of the capacitive element, and the oscillation frequency fdim of the inverter unit at the time of dimming lower limit lighting is 0.8 × fdim ≦ fo ≦ 1.6 × fdim,
The relationship between the parallel resonance frequency fo and the oscillation frequency fstr of the inverter unit at the start of the discharge lamp is fo ≧ 1.3 × fstr,
The balancer is constituted by a transformer having a plurality of windings, and each winding is constituted by a single layer aligned winding . A lighting fixture comprising the discharge lamp lighting device according to claim 1.

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