JP2810663B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device that performs high-frequency lighting by supplying high-frequency power to a discharge lamp in which low-pressure mercury vapor containing an inert gas is sealed. [Background Art] When a discharge lamp filled with low-pressure mercury vapor containing an inert gas having a large atomic weight, such as argon or krypton, is turned on at a high frequency, a stripe pattern (hereinafter referred to as a moving stripe) moving on the wall of the discharge tube is generated. It is conventionally known that a phenomenon that appears appears. Although the cause of the generation of the moving fringes is not clear, the moving fringes tend to occur particularly when the ambient temperature is low or when the current applied to the discharge lamp is reduced. There is a problem that flickering of the proof is caused by the generation of the moving fringes. This moving fringe is generated over a part or the whole of the discharge tube wall, unlike so-called flicker or the like generated near the electrode. For example, when moving stripes are generated in a case where light is adjusted by adjusting a supplied current in order to enhance a staging effect in a stage, a store, or the like, flickering of lighting causes discomfort. In addition, there may be a case where the dimming function cannot be exhibited due to the generation of such moving fringes. This moving fringe is likely to occur when a so-called power-saving discharge lamp using a mixed gas of argon and krypton is operated at high frequency, and hardly occurs in a general discharge lamp in which krypton gas is not sealed. In order to prevent the occurrence of the above-described moving fringes, conventionally, for example, a measure disclosed in Japanese Patent Application Laid-Open No. 57-118396 has been taken. The structure is as shown in FIG. 8 and FIG. In this conventional example, a DC bias circuit 7 is provided, the DC bias is applied to the discharge lamp 1, and a high-frequency current generated by a high-frequency power supply 8 for lighting the discharge lamp 1 is set as an asymmetrical object to prevent the generation of moving stripes. However, in such a conventional example, a component that allows a high withstand voltage and a large current is required as a component constituting the DC bias circuit 7, and the reliability and cost of the component increase. As another conventional example, the discharge lamp 1 is turned on with a high-frequency current 8 that is equal to or higher than a limit current at which no moving fringes are generated. You can't do that. Further, as another conventional example, a pair of filaments F ₁ and F ₂ of the discharge lamp 1 are preheated by DC power supplies 9 and 10, and the polarities of the preheating power supplies 9 and 10 of the filaments F ₁ and F ₂ are mutually changed. Japanese Patent Application Laid-Open No. 61-171089 shown in FIGS. 10 and 11 in which moving stripes are prevented by reversing FIG. However, in this conventional example, it is necessary to provide the preheating power supplies 9 and 10 as described above, which causes an increase in cost. In Japanese Patent Application Laid-Open No. 61-171090, a pair of filaments is used.
The preheating voltages of F ₁ and F ₂ are not equalized, but are imbalanced to prevent moving fringes. FIG. 12 shows a conventional circuit in which the preheating voltages of the pair of filaments F ₁ and F ₂ are unbalanced. In this circuit, the commercial power AC
Is subjected to voltage doubler rectification and smoothing by a voltage doubler rectifying and smoothing circuit 5 composed of diodes D ₃ and D ₄ and capacitors C ₁₀ and C ₁₁ to obtain a DC power source E. The inverter 2 for converting the DC power supply E output from the voltage doubler rectifying / smoothing circuit 5 to a high-frequency power supply is constituted by a so-called modified half-bridge inverter. The In the inverter 2 the fold rectifying smoothing circuit 5 the switching element Q ₁ to the DC power source E is output, Q ₂ connected in series, on the switching element Q _1, Q ₂ alternately by the control circuit 3, off to the discharge lamp 1 is turned on at high frequency. The control circuit 3 of the inverter 2 is constituted by using a switching regulator IC (TL494 or the like) 6 and outputs mutually opposite outputs of the IC 6 to a switching element comprising output transformers T ₁ and T ₂ and a MOSFET.
Gate signals are given to switching elements Q ₁ and Q ₂ composed of MOSFETs via an output circuit composed of Q ₃ and Q ₄ . Note that damping diodes D ₁ and D ₂ are connected in anti-parallel to the switching elements Q ₁ and Q ₂ , respectively. A load circuit 4 connected to the inverter 2 outputs' includes a capacitor C ₁ connected in parallel to the discharge lamp 1, a coil L ₁ constituting the capacitor C ₁ and the series resonant circuit, the inverter 2 switching element Q ₁ is charged during conduction are constituted by a capacitor C ₂ to be used as a power source to flow a reverse current to the load circuit 4 'during conduction of the switching element Q _2. The capacity of the capacitor C ₂ is Yes choose sufficiently larger than the capacitance of the capacitor C _1, it is so as not to affect the resonance of the coil L ₁ and capacitor C _1. When the discharge lamp 1 to start discharge, after the conduction of the switching element Q ₁ is, the coil L _1, passing a unidirectional current to the discharge lamp 1 via the capacitor C _1, C _2, by blocking the switching element Q ₁ switching elements by Q ₂ conducts, the coil L ₁ of the electric charge charged in the capacitor C _2, the capacitor C ₁ from
To discharge through the switching element Q _2, a current flows in the opposite direction to the discharge lamp 1. The above operation is repeated to supply high frequency power to the discharge lamp 1. Note that the inverter 2
In the control circuit 3, in order to prevent a short circuit across the DC power source E by the simultaneous ON of the switching element Q _1, Q _2, the dead time to the control output so that both switching elements Q _1, Q ₂ are both turned off It is provided. By the way, in this circuit, a transformer Tr is used to unbalance the preheating currents of the filaments F ₁ and F _2. An AC power supply AC is applied to the primary winding n ₁ of the transformer Tr, and the secondary winding n _The voltage induced at ₂ , n ₃ is applied to the filaments F ₁ , F ₂ for preheating. In this case, the filament
In order to make the preheating currents of F ₁ and F ₂ unbalanced, it is necessary that n ₂ ≠ n ₃ . In the preheating method described above, the transformer
Tr and the like are necessary, and there is a problem that the weight increases, the bulk increases, and the cost increases. [Object of the Invention] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a discharge lamp which comprises a simple circuit configured to unbalance the preheating current of a pair of filaments. It is an object of the present invention to provide a discharge lamp lighting device capable of preventing moving stripes and flickering. [Disclosure of the Invention] (Constitution) The present invention applies a high voltage due to resonance to an inverter for converting a DC power supply to a high-frequency power supply and a discharge lamp connected to the inverter output and filled with low-pressure mercury vapor containing an inert gas. An LC series resonance circuit and a preheating element connected to each filament so that a different preheating current flows to each filament of the discharge lamp by shunting the resonance current by the LC series resonance circuit. The moving stripes and flicker can be prevented with a simple configuration in which the resonance current is divided and the different preheating currents are supplied to the respective filaments. In other words, by adopting this configuration, it is not necessary to use a device with a high withstand voltage, separately provide a power supply, or use a transformer. Bring it. Embodiment 1 FIG. 1 shows an embodiment of the present invention. In this embodiment, the load circuit 4 is characterized. That is, in this embodiment a capacitor in place of the capacitor C ₁ for resonance of Figure 12
C ₃ and C ₄ , and one of the capacitors C ₃ is connected between the input terminals a and b via the coil L ₁ and the filament F ₁ ,
The other capacitor C ₄ via the coil L ₁ and the filament F ₂ input terminal a, which are connected between the b. That is, in the present embodiment, the capacitors C ₃ and C ₄ obtained by dividing the resonance capacitor C ₁ in the conventional configuration are used as capacitors for resonance and used as capacitors for preheating the filaments F ₁ and F _2. is there. Assuming that the resistances of the filaments F ₁ and F ₂ are R ₁ and R ₂ , the above-described load circuit 4 can be equivalently represented as shown in FIG. At this time, the relationship between the lamp resistance R _L of the discharge lamp 1 and the resistances R ₁ and R ₂ of the filaments F ₁ and F ₂ is R _L > R ₁ and R ₂ , and the voltage _L applied to the discharge lamp 1 When is a high-frequency voltage applied to the load circuit 4 and _in, However, omega become angular frequency of _in, the coil L _1, a capacitor C _3, C _4, determined by the lamp resistance R _L. Now the current ₁ through the resistor R ₁ becomes a sum of the current through the lamp current _L and capacitor C _3, the lamp current _L is , And the current ₁ through the resistor R ₁ is ₁ = _L + _C3 ... current ₂ flowing through the same resistor R ₂ is ₂ = _L + _C4 ... become. Here, if the _{C 3 = C 4, 1 =} 2 , and the current flowing through the filament F _1, F ₂ is equal,
By setting C ₃ ≠ C ₄ , ₁ ≠ ₂ can be achieved, and the currents flowing through the filaments F ₁ and F ₂ can have different values. That is, in FIG. 1, C ₃ ≠ C ₄ and the desired tube voltage _L is obtained (C
₃ + C ₄ ), the filaments F ₁ , F _1
The discharge lamp 1 can be turned on by making the preheating current ₂ unbalanced. In other words, the resonance capacitor connected in parallel with the discharge lamp 1 is divided into capacitors C ₃ and C ₄ , and connected to the filaments F ₁ and F ₂ as described above and used as a capacitor for preheating. The discharge lamp 1 can be turned on with the preheating currents of the filaments F ₁ and F ₂ unbalanced, thereby preventing moving stripes and flickering.
With this structure, there is no resonance loop when there is no load due to the detachment of the discharge lamp 1, so that there is an advantage that no load countermeasures are required. FIG. 3 shows that the DC power source E is obtained by the voltage doubler rectifying and smoothing circuit 5,
1 is a specific circuit of the circuit in FIG. 1 in which an inverter 2 is a modified half-bridge circuit. FIG. 4 shows a case where the inverter 2 has a full bridge circuit configuration. Embodiment 2 FIG. 5 shows another embodiment of the present invention. In this embodiment, LC
Separately provided capacitor C _3, C ₄ for preheating the capacitor C ₁ for series resonance is obtained by a preheating current in the capacitor C _3, C ₄ to be unbalanced. Fig. 5 (a)
In connecting the capacitor C ₁ so that a resonance current flows through both filament F _1, F _2, the capacitor C ₃ for preheating, C ₄
Is connected to the discharge lamp 1 as in the first embodiment. Figure 5 (b) is provided on the power supply side of the filament F _1, F ₂ of the capacitor C ₁ for resonance discharge lamp 1. Fifth
FIG. 3C shows that the filament F ₁ and F ₂ are preheated by the resonance capacitor C ₁ in the normal state, and the filament F is turned on by the switch SW ₁ which is turned on at a low temperature when the frequency of moving stripes increases. ₂ by flowing a preheating current through the capacitor C _5, is obtained by unbalanced preheating current of the filaments F _1, F ₂ only at low temperatures, it can be prevented movement stripes or flickering in the substantially same manner as in the above . In this case, there is also an advantage that a decrease in luminous flux at a low temperature can be compensated. In other words, by connecting the capacitor C _5, the applied voltage of the discharge lamp 1 can be increased, because the lamp current increases. The preferably used temperature sensitive reed switch as the switch SW _1. The switch SW ₁ Figure 5 (a),
It goes without saying that the capacitor may be inserted in series with the capacitors C ₃ and C ₄ shown in FIG. (Embodiment 3) FIG. 6 shows still another embodiment of the present invention. In this embodiment, the capacitors C ₃ and C ₄ are composed of two capacitors C ₆ and C ₇ and capacitors C ₈ and C ₉ connected in series.
Diodes with opposite current directions at both ends of C ₇ and C ₉
D ₅ and D ₆ are connected. In this embodiment, when the potential of the input terminal a is high, the lamp current _L is determined by the coil L ₁ , the capacitors C _{6 to} C ₈ , and the lamp resistance _RL , and when the potential of the input terminal b is high, the coil L ₁ and the capacitor C _{6 to} C ₉ , lamp resistance R _L
Is determined by That is, by any of the capacitor C _7, C ₉ is bypassed by the diode D _5, D ₆ by the current direction, is obtained by a preheating current unbalance. In addition,
Capacitor C to adjust asymmetry of lamp current _L
0 may be provided. (Example 4) FIG. 7 is a further embodiment of the present invention, swapping a capacitor C ₁ and the coil L _1, a coil L ₁ 2 coils
Is obtained by a preheating current unbalance is divided into L _2, L _3. In this case, a similar effect can be expected. In the description of the above embodiment, the case where the inverter 2 has a modified half-bridge circuit or a full-bridge circuit configuration has been described. [Effect of the Invention] As described above, the present invention applies a high voltage due to resonance to an inverter that converts a DC power supply to a high-frequency power supply and a discharge lamp connected to the inverter output and filled with low-pressure mercury vapor containing an inert gas. The LC series resonance circuit and the preheating element connected to each filament so that different preheating currents flow to each filament of the discharge lamp by dividing the resonance current by the LC series resonance circuit. This has the advantage that moving stripes and flickering can be prevented with a simple configuration in which different preheating currents are supplied to each filament by splitting the resonance current by the element. That is,
By adopting this configuration, it is not necessary to use an element having a high withstand voltage, separately provide a power supply, or use a transformer, so that useful effects in a low-cost, light-weight, and small-sized product can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of the above, FIG. 3 is a specific circuit diagram of the above, and FIG. Circuit diagram when applied to
6 (a) to 6 (c) are main circuit diagrams showing another embodiment of the present invention, FIG. 6 is a main circuit diagram of still another embodiment of the present invention, and FIG. 8 and 9 are circuit diagrams of a conventional example, and FIGS. 10 and 11 are circuit diagrams of other conventional examples, respectively. FIG. 12 and FIG. FIG. 7 is a specific circuit diagram of still another conventional example. 1 the discharge lamp, 2 denotes an inverter, E is a direct current power source, L ₁ is a coil, C ₁ -C ₄ capacitors, F _1, F ₂ filament, SW ₁
Is a switch.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 41/24

Claims (1)

(57) [Claims] An inverter that converts a DC power supply to a high-frequency power supply, an LC series resonance circuit that connects to the inverter output, and applies a high voltage by resonance to a discharge lamp filled with low-pressure mercury vapor containing an inert gas, and a resonance by the LC series resonance circuit A discharge lamp lighting device comprising: a preheating element connected to each filament so that a different preheating current flows to each filament of the discharge lamp by dividing the current. 2. One of the coil and the capacitor of the LC series resonance circuit is divided and used as the preheating element, and a different resonance current or a preheating current is individually supplied to each filament of the discharge lamp through the divided coil or the capacitor. The discharge lamp lighting device according to claim 1, wherein: 3. 3. The discharge lamp lighting device according to claim 1, wherein a preheating current of the filament is made different at a low temperature.