JP4259534B2 - lighting equipment - Google Patents

Description

  The present invention relates to a lighting fixture.

  In general, it is known that when a direct current voltage is applied between both electrodes of a discharge lamp such as a fluorescent lamp to light it, the luminance decreases near the anode. This phenomenon is caused by mercury ions in the discharge lamp gathering on the cathode side, and is called an electrophoretic phenomenon or a cataphoresis phenomenon (hereinafter referred to as a cataphoresis phenomenon).

  In order to prevent the occurrence of the catalysis phenomenon, it has been considered effective to apply an AC voltage between both electrodes of the discharge lamp. However, when technology for lighting a discharge lamp at a high frequency using an inverter circuit as in recent years has become widespread, it has been found that even when a high-frequency AC voltage is applied to the discharge lamp, a catalysis phenomenon may occur. I came. Such a cataphoresis phenomenon becomes more prominent as the environmental temperature at which the discharge lamp is turned on is lower.

  The cataphoresis phenomenon occurs when the discharge lamp is turned on at a high frequency for the following reason. In general, since a capacitive component (floating capacitance) exists between the discharge plasma in the discharge lamp and the ground, the high-frequency current flows from the discharge plasma formed by applying a high-frequency alternating voltage between the electrodes to the ground through the stray capacitance. Flowing. On the other hand, the charge carriers inside the discharge plasma are mercury ions and electrons, and electrons have a much higher mobility than mercury ions, so when high-frequency current flows through stray capacitance, Much more electrons are injected than mercury ions, resulting in a negatively charged discharge lamp wall. The negative charge amount on the tube wall of the discharge lamp increases as the potential difference of the discharge plasma with respect to the ground (hereinafter referred to as voltage to ground) increases.

  That is, if the voltage to ground is different at each part in the tube length direction of the discharge lamp, a negative potential gradient occurs on the tube wall of the discharge lamp. Since mercury ions collect on the larger negative charge amount, the higher the negative charge amount, the higher the brightness. As a result, when the voltage to ground has a gradient in the tube length direction of the discharge lamp as described above, a cataphoresis phenomenon occurs. Here, if the higher voltage to ground is the high voltage side, the high voltage side has a larger negative charge amount, so the luminance on the low voltage side is lower than that on the high voltage side.

Various configurations are known for a lighting circuit that applies a high-frequency voltage to a discharge lamp, but a circuit configuration as shown in FIG. 7 is widely employed (not identical, but see, for example, Patent Document 1). This lighting circuit performs full-wave rectification of an AC power supply AC with a rectifier DB ₁ composed of a diode bridge, performs DC-DC conversion with a chopper circuit CHP, and then performs DC-AC conversion with an inverter circuit INV. The high frequency output of INV is applied to the load circuit 1 including the discharge lamp La. Here, as the inverter circuit INV, a series circuit of a pair of switching elements Q ₂ and Q ₃ connected between the output ends of the chopper circuit CHP is provided, and the load circuit 1 and the direct current are connected between both ends of the one switching element Q _3. It is adopted as a half-bridge with a series circuit of the capacitor C ₃ for cutting.

  If such a configuration is adopted as the inverter circuit INV, the number of circuit components can be reduced and the cost can be reduced compared to an inverter circuit in which four switching devices are bridge-connected. Even when compared with an inverter circuit in which a series circuit and a series circuit of two capacitors are connected in parallel, the number of circuit component elements is small and the circuit can be provided at low cost. Moreover, in the latter case, there is a disadvantage that the steady operation is not performed until the capacitor is charged immediately after the operation is started, and stress is applied to the load circuit 1 during this period, whereas in the inverter circuit INV shown in FIG. Since no problems arise, the inverter circuit INV having the configuration shown in FIG. 7 is widely used.

The lighting circuit and the discharge lamp La are incorporated in the instrument main body 10, and the instrument main body 10 is generally formed of metal (sheet metal). The chopper circuit CHP and the inverter circuit INV in the negative electrode side of the output end rectifier DB _1, is grounded to the fixture main body 10 through the capacitor C ₀ which is provided to the chopper circuit CHP, the instrument body 10 is grounded to the earth. Thus, the appliance body 10 that is closest to the discharge lamp La is a reflector that controls the light distribution of the light output of the discharge lamp La, so that a high-frequency current flows from the discharge lamp La to the ground through the reflector. Will flow. Note that the distance between the center line and the reflector in the tube length direction of the discharge lamp La is constant.
JP-A-9-97698

Incidentally, the inverter circuit INV described above, since one end of the discharge lamp La is one that is grounded at all times via a capacitor C ₃ and the capacitor C _0, there is a bias in electric potential in the pipe length direction of the discharge lamp La. That is, the ground side (the lower end side in FIG. 7) is the low pressure side, and the non-ground side is the high pressure side. Therefore, as described above, a gradient occurs in the negative charge amount of the tube wall of the discharge lamp La, the mercury ions are unevenly distributed, and a catalysis phenomenon occurs.

Such a catalysis phenomenon will be described in terms of leakage current from the discharge lamp La. That is, if the stray capacitance between the discharge plasma position x and the ground is Cx, the ground voltage at the same position is Vx, and the output frequency of the inverter circuit INV is f ₀ , the high frequency flowing from the discharge lamp La to the ground. Leakage current ix is ix = 2πf ₀ CxVx. Here, since the distance between the center line and the reflector in the tube length direction of the discharge lamp La is constant, Cx can be regarded as constant regardless of the position x, and the current ix is determined by the ground voltage Vx after all. Will be. In the circuit configuration shown in FIG. 7, the voltage Vx to ground is higher at the high-voltage end of the discharge lamp La than at the low-voltage end, so that the leakage current ix is also on the high-pressure side of the discharge lamp La. The end portion of the is larger than the end portion on the low pressure side. If the leakage current ix is large, the negative charge amount on the tube wall is increased, and mercury ions are collected. That is, the brightness at the end portion on the high voltage side is higher.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a luminaire that prevents the occurrence of a catalysis phenomenon by controlling a high-frequency leakage current when a discharge lamp is lit at a high frequency. There is.

The invention of claim 1 uses a lighting circuit for lighting a discharge lamp at a high frequency, and a leakage current flowing between the discharge lamp and the tool body in the vicinity of each electrode of the discharge lamp when the discharge lamp is turned on, using a part of the tool body. And a leakage current balancing means that balances and prevents the occurrence of cataphoresis phenomenon , the fixture body is provided with a reflector that controls light distribution in the vicinity of the discharge lamp, and the leakage current balancing means is an output of the lighting circuit. The stray capacitance with respect to the reflector at one end of the discharge lamp connected to one end on the high potential side of the end is set smaller than the stray capacitance with respect to the reflector at the other end of the discharge lamp. It is.

According to this configuration, with respect to the high-frequency leakage current from the discharge lamp to the fixture body, the impedance to the leakage current can be adjusted by adjusting the stray capacitance between the discharge lamp and the reflector, and the tube length of the discharge lamp can be adjusted. Since the leakage current can be made substantially equal in each part in the direction, the occurrence of a potential gradient in the tube length direction of the discharge lamp can be suppressed , and as a result, the occurrence of the catalysis phenomenon can be prevented.

According to a second aspect of the present invention, in the first aspect of the invention, the distance between the one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit and the reflecting plate is the other end of the discharge lamp. The stray capacitance is set by setting the distance larger than the distance between the reflector and the reflector.

The invention of claim 3 is the invention of claim 1, a coating film was formed on the surface facing the discharge lamp in the reflector, the discharge lamp is connected to one end of a high-potential side of the output terminal of the lighting circuit the dielectric constant of the coating film of the portion opposed to the one end, by setting smaller than the dielectric constant of the coating film portion facing the other end of the discharge lamp, Ru der that sets the stray capacitance.
The invention of claim 4 is the invention of claim 1, a coating film was formed on the surface facing the discharge lamp in the reflector, the discharge lamp is connected to one end of a high-potential side of the output terminal of the lighting circuit The stray capacitance is set by setting the thickness of the coating film at the part facing the one end to be smaller than the thickness of the coating film at the part facing the other end of the discharge lamp.

According to a fifth aspect of the present invention, in the first aspect of the invention, the area of the reflecting plate facing one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit is defined as the other end of the discharge lamp. The stray capacitance is set by setting it smaller than the area of the reflecting plate facing the part.

According to the configuration of the present invention, with respect to the high-frequency leakage current from the discharge lamp to the fixture body, the impedance with respect to the leakage current can be adjusted by adjusting the stray capacitance between the discharge lamp and the reflection plate. Since the leakage current can be made substantially equal at each part in the tube length direction, it is possible to suppress the occurrence of a potential gradient in the tube length direction of the discharge lamp and to prevent the occurrence of the catalysis phenomenon. is there.

  In each embodiment described below, the occurrence of a catalysis phenomenon is suppressed by the configuration of the appliance main body including the discharge lamp. The lighting circuit for lighting the discharge lamp is the same as the conventional configuration, and includes a rectifier, a chopper circuit, and an inverter circuit, and has a basic configuration in which a high-frequency voltage output from the inverter circuit is applied to a load circuit including the discharge lamp. . However, the technical idea of the present invention can be applied to lighting circuits having other configurations. Further, a discharge lamp containing mercury vapor as a discharge gas is used. The load circuit includes a resonance capacitor connected in parallel to the discharge lamp, and a resonance inductor connected in series to the resonance capacitor. The discharge lamp is held by the appliance main body, and a metal reflector for light distribution control provided in the appliance main body is disposed in the vicinity of the discharge lamp.

(Embodiment 1)
In the present embodiment, as shown in FIG. 1, the distance between the reflector 11 provided on the instrument main body 10 and the discharge lamp (here, a straight tube type) La is made different at each part in the tube length direction of the discharge lamp La. Is. Since the lighting circuit of the discharge lamp La has the above-described configuration, the discharge lamp La has a high pressure side and a low pressure side. Therefore, the distance dH between the high pressure side end of the discharge lamp La and the reflecting plate 11 is set to be larger than the distance dL between the low pressure side end and the reflecting plate 11 (dH> dL). Here, the reflecting plate 11 has a flat plate shape and is inclined at a constant angle with respect to the center line along the longitudinal direction of the discharge lamp La. In addition to the reflector 11, the appliance body 10 includes a lamp socket 12 that holds the discharge lamp La.

  In the above-described configuration, the stray capacitance with respect to the reflecting plate 11 at each end of the discharge lamp La (the reflecting plate 11 is grounded in common with the circuit unit) is smaller on the high pressure side than on the low pressure side. That is, the impedance is higher on the high voltage side with respect to the same frequency. As a result, compared to the case where the center line along the longitudinal direction of the discharge lamp La and the reflector 11 are parallel, the difference in the amount of leakage current between the high pressure side and the low pressure side of the discharge lamp La can be reduced. Thus, the occurrence of the cataphoresis phenomenon is prevented (that is, the reflector 11 functions as a leakage current balancing means depending on its shape). Incidentally, in the discharge lamp La called the T8 type or the T5 type, each having a tube diameter of 8/8 inch and 5/8 inch, it is desirable to set the distance dH between the high pressure side end and the reflecting plate 11 to 15 mm or more. We have knowledge.

(Embodiment 2)
As apparent from the first embodiment, in order to reduce the difference between the leakage current on the high-pressure side and the leakage current on the low-pressure side of the discharge lamp La, the gap between the end portion on the high-pressure side of the discharge lamp La and the reflector 11 is reduced. What is necessary is just to make impedance larger than the low voltage | pressure side. Therefore, in this embodiment, the dielectric constant of the coating film 11a (see FIG. 2) applied to the reflector 11 is made different between the high pressure side and the low pressure side of the discharge lamp La. That is, when the dielectric constant of the coating film 11a facing the high-pressure side of the discharge lamp La is εH, and the dielectric constant of the coating film 11a facing the low-pressure side is εL, the relationship is εH <εL, and the dielectric constant is in the middle portion. The coating film 11a is formed so as to continuously change at a constant rate. Here, the lighting circuit of the discharge lamp La is assumed to be the same as that of the first embodiment.

  Since the stray capacitance between each part in the longitudinal direction of the discharge lamp La and the reflector 11 is proportional to the dielectric constant of the coating film 11a at each part, the stray capacity at the end on the high-pressure side of the discharge lamp La is low. As in the first embodiment, the impedance is higher on the high voltage side with respect to the same frequency. That is, the difference in the amount of leakage current between the high voltage side and the low voltage side is reduced, and the occurrence of the catalysis phenomenon is suppressed (that is, the reflecting plate 11 functions as a leakage current balancing means by the coating film 11a). In addition, although the relative dielectric constant of a general coating material is 7 or more, a material having a relative dielectric constant smaller than 7 is used on the high voltage side. In order to continuously change the dielectric constant, for example, two types of paints having different dielectric constants are used, and the thickness is continuously changed and the two layers are coated to have a constant thickness. Thus, it is possible to form the coating film 11a whose dielectric constant continuously changes.

(Embodiment 3)
In the present embodiment, as shown in FIG. 3, the thickness of the coating film 11a applied to the reflector 11 is continuously changed in the longitudinal direction of the discharge lamp La. The coating film 11a is formed so that tH <tL when the thickness of the coating film 11a corresponding to the high pressure side of the discharge lamp La is tH and the thickness of the coating film 11a on the low pressure side is tL. Here, the lighting circuit of the discharge lamp La is assumed to be the same as that of the first embodiment.

  Even with this configuration, the stray capacitance between the high-pressure end of the discharge lamp La and the reflecting plate 11 is smaller than the stray capacitance on the low-pressure side, so that the difference in the leakage current amount at both ends of the discharge lamp La is reduced. Can be small. That is, the occurrence of the cataphoresis phenomenon can be prevented (that is, the reflector 11 functions as a leakage current balancing means by the coating film 11a as in the second embodiment).

(Embodiment 4)
In the present embodiment, as shown in FIG. 4, a hole 11 b is formed in a portion of the reflector 11 that faces the end portion on the high-pressure side of the discharge lamp La. Here, the lighting circuit of the discharge lamp La is assumed to be the same as that of the first embodiment.

  As described above, if the hole 11b is formed in a part of the reflector 11 facing the discharge lamp La, the area where the reflector 11 and the discharge lamp La are opposed decreases in the part where the hole 11b is formed. The stray capacitance is also reduced at the site. That is, the stray capacitance on the high-pressure side of the discharge lamp La is reduced from that on the low-pressure side. As a result, the difference in leakage current amount at both ends of the discharge lamp La is reduced, and the occurrence of the catalysis phenomenon is suppressed (that is, The reflecting plate 11 functions as a leakage current balancing means due to its shape).

(Embodiment 5)
In the present embodiment, as in the fourth embodiment, a part of the opposed part of the discharge lamp La and the reflecting plate 11 is partially different from the other part. However, rather than reducing the area of the discharge lamp La facing the high pressure side, as shown in FIG. 5, a large number of irregularities are formed on the surface of the reflector 11 in order to increase the area facing the low pressure side. The uneven surface 11c is provided. In other words, the stray capacitance between the reflection plate 11 on the low pressure side of the discharge lamp La and the reflection plate 11 is made larger than the high pressure side by increasing the facing area between the low pressure side end of the discharge lamp La and the reflection plate 11. It is getting bigger. As a result, the difference in the amount of leakage current at both ends of the discharge lamp La is reduced, and the occurrence of the catalysis phenomenon is suppressed. Also in the present embodiment, the discharge lamp La is turned on by a circuit similar to that in the first embodiment (that is, the reflector 11 functions as a leakage current balancing means depending on its shape).

(Reference example)
In this example , as shown in FIG. 6, a plurality (two in the illustrated example) of lamp holders 13H and 13L for holding the discharge lamp La are provided in the middle of the discharge lamp La. The lamp holders 13H and 13L are made of metal and are made of materials having different electrical conductivities. That is, if the conductivity of the lamp holder 13H close to the high pressure side of the discharge lamp La is σH, and the conductivity of the lamp holder 13L close to the low pressure side is σL, the material is selected so that σH <σL. The lighting circuit of the discharge lamp La is assumed to be the same as that of the first embodiment.

  Considering the leakage current flowing between the discharge lamp La and the reflector 11 through the lamp holders 13H and 13L, the leakage current IH passing through the lamp holder 13H is IH∝σH × VH, and the leakage passing through the lamp holder 13L. The current IL is IL∝σL × VL. However, VH and VL are potential differences between the discharge lamp La and the reflecting plate 11 at portions corresponding to the lamp holders 13H and 13L, respectively. That is, VH> VL. If the shape and dimensions of the lamp holders 13H and 13L are exactly the same, the proportional constants in the above two formulas are equal. Here, since the leakage currents IH and IL passing through the lamp holders 13H and 13L are sufficiently larger than the leakage current generated by the stray capacitance between the discharge lamp La and the reflector 11 at the same position, the lamp holders 13H and 13L are The leakage current at the provided position is determined by IH and IL. Therefore, if the conductivity σH and σL are set appropriately, the relationship of IH <IL can be obtained regardless of VH> VL.

  If set so as to obtain this relationship, the sum of the leakage current due to the stray capacitance between the discharge lamp La and the reflector 11 and the leakage current flowing through the lamp holders 13H and 13L at each end of the discharge lamp La is set. As a result, it is possible to prevent the occurrence of a catalysis phenomenon (that is, the lamp holders 13H and 13L provided in the instrument body 10 function as a leakage current balancing means). In the above description, the lamp holders 13H and 13L are formed of materials having different electrical conductivities σH and σL. However, the leakage currents IH and IL are different by changing the shapes of the lamp holders 13H and 13L. You may make it let.

1 is a schematic side view showing a first embodiment. 6 is a schematic side view showing a second embodiment. FIG. FIG. 5 is a schematic side view showing a third embodiment. FIG. 6 is a schematic plan view showing a fourth embodiment. FIG. 10 is a schematic side view showing a fifth embodiment. It is a schematic side view which shows a reference example . It is a circuit diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Load circuit 10 Appliance main body 11 Reflector 11a Paint film 11b Hole 11c Uneven surface 13H, 13L Lamp holder AC AC power supply CHP Chopper circuit C ₀ capacitor DB ₁ Rectifier INV Inverter circuit La Discharge lamp

Claims (5)

A lighting circuit that turns on the discharge lamp at a high frequency, and a catalysis that balances the leakage current that flows between the discharge lamp and the instrument body in the vicinity of each electrode of the discharge lamp when the discharge lamp is lit by using a part of the instrument body. Leakage current balancing means for preventing the occurrence of the phenomenon , the fixture body is provided with a reflector that controls light distribution in the vicinity of the discharge lamp, and the leakage current balancing means is connected to the high potential side of the output end of the lighting circuit. A lighting fixture comprising: a stray capacitance with respect to a reflecting plate at one end of a discharge lamp connected to one end of the discharge lamp being set smaller than a stray capacitance with respect to a reflecting plate at the other end of the discharge lamp . By setting the distance between one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit and the reflecting plate to be larger than the distance between the other end of the discharge lamp and the reflecting plate, The lighting apparatus according to claim 1, wherein the stray capacitance is set . Forming a coating film on the surface of the reflector facing the discharge lamp, the dielectric constant of the coating film at the portion facing the one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit, The lighting apparatus according to claim 1 , wherein the stray capacitance is set by setting the dielectric constant smaller than a dielectric constant of a coating film at a portion facing the other end of the discharge lamp . A coating film is formed on the surface of the reflector facing the discharge lamp, and the thickness of the coating film at the portion facing the one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit is discharged. The lighting apparatus according to claim 1 , wherein the stray capacitance is set by setting the thickness smaller than a thickness of a coating film at a portion facing the other end of the lamp . The area of the reflecting plate facing one end of the discharge lamp connected to one end on the high potential side of the output end of the lighting circuit is set smaller than the area of the reflecting plate facing the other end of the discharge lamp. the lighting fixtures according to claim 1, characterized in that setting the stray capacitance.

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