JPH0782913B2 - Discharge lamp lighting device - Google Patents

Description

The present invention relates to a discharge lamp lighting device.

[Prior Art] To increase the output of the discharge lamp, the lamp current may be increased.
However, simply increasing the lamp current heats the bright spots of the filament of the discharge lamp and shortens the life of the discharge lamp. Therefore, in order to increase the output of the discharge lamp without impairing the life of the discharge lamp, two bright spots are formed on the filament. A so-called double spot type lighting device is known.

FIG. 6 shows a circuit diagram of a conventional discharge lamp lighting device, which uses a half-bridge inverter circuit as the discharge lamp lighting device. A series circuit of transistors Q ₁ and Q ₂ is connected in parallel to the DC power supply 1, and diodes D ₁ and D ₂ are connected in parallel to the respective transistors Q ₁ and Q ₂ . One transistor Q ₁
A series circuit of an inversion capacitor C ₀ for preventing direct current, a discharge lamp 2 and a choke transformer L ₁ is connected to, and one end of the filament of the discharge lamp 2 has a capacitor C ₁ and a preheating transformer T ₃ . A series circuit of primary windings is connected. Also,
The secondary winding side of the preheating transformer T ₃ constituting the preheating circuit is connected to the other end of the filament. Here, the resonance capacitor C ₁ and the choke transformer L ₁ form a series resonance circuit, and the inverting capacitor C ₀ has a larger capacity than the resonance capacitor C ₁ and is selected as a capacitance that does not contribute to resonance. There is. Incidentally, the transistors Q _1, Q _2, capacitors C _1, at a choke transformer L _1, etc., constitute an inverter circuit portion for generating the opposite first and second high-frequency output voltage of the increase or decrease of the high-frequency output voltage. The discharge lamp 2 is turned on by the high frequency output voltage from the inverter circuit section. Since the current flowing through the preheating transformer T ₃ has a phase difference of 90 ° from the lamp current, a double spot is formed on the filament of the discharge lamp 2. The transistors Q ₁ and Q ₂ are alternately switched by the control circuit 3 and the drive circuit 4.

Regarding the dimming method, a dimming signal from a dimming circuit (not shown) is received, converted into a DC voltage by the control circuit 3, and a transistor Q ₁ , via the base resistors R _B1 and R _B2 in the drive circuit 4. Q ₂
Discharge lamp 2 by unbalance the on / off ratio of
The light is turned on.

[Problems to be Solved by the Invention] In this dimming method, during dimming lighting, the tube voltage becomes high and the resonance current I _C1 becomes large, so that the preheating voltage Vf becomes high and the life of the discharge lamp 2 is adversely affected. Have the problem of giving. Here, the relationship between the dimming ratio and the filament voltage is as shown in FIG. 7, but this problem is particularly serious in the case of high output lighting (double spot lighting) because the dimming range becomes wide. The filament voltage during% dimming is 15
It is about twice the filament voltage at 0% lighting. By the way, considering the lamp life, it is desired that the bright spot temperature of the filament cathode be kept at an optimum value. However, when the output is increased to 100% or more of the rated value, there is a problem that the lamp current becomes excessive and the bright spot temperature rises too much. Moreover, when dimming operation is performed with a high-power inverter, the discharge tube voltage rises and the preheating voltage rises too much, and the bright spot temperature due to preheating rises, which adversely affects the life of the discharge tube during dimming operation. There is also the problem of exerting it.

The present invention is provided in view of the above point, and prevents the fixed price of the life of the discharge lamp during dimming lighting by suppressing the filament voltage of the discharge lamp during dimming lighting to a predetermined level or less. A discharge lamp lighting device is provided for the purpose.

[Means for Solving the Problems] The present invention provides an inverter circuit output for generating a first high frequency output voltage, which is composed of two transistors, one choke coil and one capacitor, and a first high frequency output thereof. A second high-frequency output voltage that outputs the output of the preheating transformer that is connected in series to one capacitor of the inverter circuit that generates the voltage is generated, and the first and second high-frequency output voltages are the DC voltage of the DC power supply. Accordingly, the increase and decrease of the high frequency output voltage are opposite to each other and the phases are different by 90 °.

And a dimming circuit that controls the circuit unit that generates the first and second high-frequency output voltages to increase and decrease the high-frequency output voltage,
A discharge lamp that lights up by receiving the first high-frequency output voltage;
A double-spot type discharge lamp lighting device, comprising: a preheating circuit for receiving a second high frequency output voltage to generate a preheat output for preheating a filament of a discharge lamp, and forming a cathode bright spot at two points of the filament of the discharge lamp. It is what constitutes.

In such a discharge lamp lighting device, the discharge lamp lighting device according to the present invention is a choke coil and switch connected in parallel with a preheating transformer for generating the second high frequency output voltage, or a saturable choke coil, or A bypass means including a magnetic switch is configured, and the bypass means reduces the preheat output to a predetermined level or less when the first high-frequency output voltage becomes a predetermined level or less by the dimming circuit. I am trying.

[Operation] The bypass means reduces the preheat output to a predetermined level or less when the first high-frequency output voltage becomes a predetermined level or less by the dimming circuit.

Further, two preheating transformers for applying a preheating voltage to each filament of the discharge lamp are provided, and a saturable choke is connected to a series circuit in which the primary sides of both preheating transformers are connected in series,
The double spot method is stabilized.

Example 1 An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of the present embodiment, which is characterized in that a choke coil L ₂ which is a bypass means for resonance current bypass is connected in parallel with the filament preheating transformer T _{3 as} compared with the conventional example. When the dimming switch S ₁ for dimming for lowering the high frequency output voltage from the inverter circuit section is turned on, the dimming signal is input to the control circuit 3 and the relay Ry ₁ is turned on. Contact S ₂ turns on. When the contact S ₂ is turned on, the choke coil L ₂ is connected in parallel with the preheating transformer T ₃ . Since the resonance current I _C1 during dimming is also bypassed to the choke coil L ₂ , the current flowing through the preheating transformer T ₃ becomes small and the filament voltage Vf is suppressed. At this time, the relationship between the filament voltage Vf and the dimming ratio is as shown in FIG. In FIG. 2, the A curve shows the case where the bypass means is provided, and the B curve shows the case where the bypass means is not provided.

The dimming unit reduces the high frequency output by the control circuit of the inverter and increases the voltage across the discharge tube 2 (discharge tube voltage). Therefore, if there is no bypass, B
It becomes a curve, and excessive preheating is performed in the 50% mode, which adversely affects the life of the discharge tube. Therefore, when performing a dimming operation deeper than a certain dimming ratio, a bypass means is provided so that the curve A is formed to reduce preheating. In particular, in the case of the double-spot method, the dimming range is wide and the increase in filament voltage during dimming lighting is also large.
The effect is great.

[Embodiment 2] FIG. 3 shows Embodiment 2 and is characterized in that a saturable choke L ₃ is connected in parallel with the preheating transformer T ₃ . When the tube voltage of the discharge lamp 2 increases and the resonance current I _C1 increases during dimming lighting, the saturable choke L ₃ begins to saturate, and the resonance current
Since I _C1 is bypassed, the current flowing through the preheating transformer T ₃ becomes small and the filament voltage Vf is suppressed.

Example 3 Example 3 is shown in FIG. It is characterized in that a choke L ₄ for bypassing a resonance current is provided in parallel with the preheating transformer T ₃ . Further, a DC voltage for dimming is applied to the primary side of the choke L ₄ , and as the dimming ratio decreases, the degree of saturation of the choke L ₄ increases and the impedance decreases. That is, when the dimming ratio decreases, the resonance current I _C1 also flows into the choke L ₄ , so that the current of the preheating transformer T ₃ is suppressed and the filament voltage is suppressed.

Example 4 Example 4 is shown in FIG. The preheating transformer is divided into T ₃ and
T ₃ ′ and the filament voltage Vf is applied to the filament of the discharge lamp 2 from the secondary side of each preheating transformer T ₃ , T ₃ ′. The saturable talk L ₃ is connected in parallel with both preheating transformers T ₃ and T ₃ ′. Also in this embodiment, at the time of dimming lighting, the tube voltage of the discharge lamp 2 becomes high, and the resonance current I _C1
Becomes larger, the saturable choke L ₃ begins to saturate and the resonance current I _C1 is bypassed, so that the current flowing through the preheating transformers T ₃ and T ₃ ′ becomes smaller and the filament voltage Vf is suppressed. Then, the double spots of the discharge lamp 2 are stabilized by the divided preheating transformers T ₃ , T ₃ ′.

[Effects of the Invention] The discharge lamp lighting device according to the present invention is configured as described above, and has the following effects.

That is, in the case of the double spot method, which has a wide dimming range and a large increase in filament voltage during dimming lighting, the bright spots can be dispersed, the bright spot temperature can be reduced, and the life of the discharge tube can be improved. When the light is turned on, the preheating voltage is switched and reduced, which has an advantage that it is possible to reduce the deterioration of the life of the discharge tube during the dimming.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a dimming ratio and a filament voltage in the same, FIG. 3 is a circuit diagram of a second embodiment in the same, and FIG. FIG. 5 is a circuit diagram of Example 4 of the above, FIG. 5 is a circuit diagram of Example 4 of the above, FIG. 6 is a circuit diagram of a conventional example, and FIG. 7 is a diagram showing the relationship between the dimming ratio and the filament voltage of the above. is there. 2 is a discharge lamp, L ₃ is a saturable choke, and T ₃ and T ₃ ′ are preheating transformers.

Front Page Continuation (72) Inventor Shigenosuke Ohara 3-6-1, Shintaka, Yodogawa-ku, Osaka City, Meiji National Industrial Co., Ltd. (56) Reference JP-A-47-18171 (JP, A) JP Sho 60-72198 (JP, A)

Claims (2)

[Claims] 1. An inverter circuit output for generating a first high-frequency output voltage, which comprises two transistors, one choke coil and one capacitor, and an inverter circuit section for generating the first high-frequency output voltage. A second high-frequency output voltage that outputs the output of the preheating transformer connected in series with one capacitor is generated, and the first and second high-frequency output voltages receive the DC voltage of the DC power supply and increase or decrease the high-frequency output voltage. And a dimming circuit for controlling the circuit unit for generating the first and second high frequency output voltages to increase and decrease the high frequency output voltage, and the first high frequency output voltage. And a preheating circuit for generating a preheating output for preheating the filament of the discharge lamp by receiving the second high-frequency output voltage. In a double-spot type discharge lamp lighting device formed at two locations, a choke coil and a switch, a saturable choke coil, or a magnetic switch connected in parallel with a preheating transformer for generating the second high-frequency output voltage. By-pass means is configured, and the by-pass means is the first dimming circuit.
The discharge lamp lighting device, wherein the preheat output is reduced to a predetermined level or lower when the high frequency output voltage of the power supply is lower than a predetermined level. 2. A double spot system in which cathode bright spots are provided at two locations on the filament of a discharge lamp is provided with two preheating transformers for applying a preheating voltage to each filament of the discharge lamp, and the primary side of both preheating transformers is provided. The discharge lamp lighting device according to claim 1, wherein a saturable choke coil is connected to a series circuit connected in series to form a bypass means.