JP2000348892A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device using a C preheating method to a discharge lamp having a relatively high lamp voltage, securing a preceding preheating current and capable of reducing normally preheating current when modulating light. SOLUTION: This device is provided with a discharge lamp 8 having a relatively high lamp voltage, a transformer T1 connected to the output end of a high frequency power source 4, a series circuit of the discharge lamp 8, an inductor L11 and a condenser C1 connected to the both ends of the transformer T1 and a preheating capacitor 13 connected between non-power source side terminals of the discharge lamp 8. The inductor L11 and the capacitor 13 form a resonant circuit to synchronize the oscillation frequency of a DC-DC converting circuit 3 with the oscillation frequency of a high frequency power source 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art Conventionally, as a means used for preheating a filament of a discharge lamp, as shown in FIG. 4, a C preheater such as a capacitor C14 connected between non-power-supply-side terminals of a discharge lamp 8 is used. The scheme is well known.

This circuit includes an AC power supply 1, a rectifier 2 for rectifying an AC voltage of the AC power supply 1, a DC-DC conversion circuit 3 for DC-DC converting the DC voltage of the rectifier 2,
A high-frequency power supply 4 (for example, a half-bridge inverter circuit) for converting the DC voltage output V1 of the DC conversion circuit 3 into an AC high-frequency voltage, and an inductor L12 and a discharge lamp 8 connected to the output terminal of the high-frequency power supply 4. It comprises a series circuit and a capacitor C14. Inductors L12 and C
14 form a resonance circuit.

When a current flows through C14 via both filaments of the discharge lamp 8, both filaments are preheated and a resonance voltage is generated at both ends of the discharge lamp 8. At the time of preheating, the oscillation frequency of the high-frequency power supply 4 is set higher than the natural resonance frequency to lower the voltage across C14,
At the time of starting, the discharge lamp 8 can be turned on after the filament of the discharge lamp 8 is sufficiently preheated by increasing the voltage across C14 by bringing the oscillation frequency of the high-frequency power supply 4 close to the natural resonance frequency.

[0005] However, the above-described conventional example has the following problems. In the circuit shown in FIG. 4, in order to obtain a sufficient starting voltage, it is necessary to reduce the inductance of the current limiting inductor L12 and increase the capacity of C14. However, if the capacity of C14 is increased, the discharge lamp 8 is turned on. After that, a large amount of current (constant preheating current during lighting of the discharge lamp 8) flowing through C14 via both filaments of the discharge lamp 8 remains, and the constant preheating current causes an increase in loss, a decrease in circuit efficiency, and a decrease in the discharge lamp. Will be deteriorated. The constant preheating current is expressed as follows: constant preheating current = capacity of capacitor C14 × 2π × oscillation frequency of high frequency power supply 4 × lamp voltage Vla.

[0006]

However, the above-described conventional example has the following problems.

In recent years, discharge lamps having a small lamp tube diameter and a long optical path length (for example, FHD70 and FH manufactured by Matsushita Electronics Corporation)
D100), this type of discharge lamp has a relatively high lamp voltage at the time of dimming as shown in FIG. 7, and therefore, the DC-DC conversion by the C preheating method as described above. Assuming that the output voltage V1 of the circuit 3 is substantially constant, a discharge lamp having a relatively low lamp voltage (for example, FC manufactured by Matsushita Electronics Co., Ltd.)
L40), a larger amount of current (a constant preheating current during the operation of the discharge lamp 8) flowing through the capacitor C14 through both filaments of the discharge lamp 8 remains, and the current further increases loss and circuit efficiency. Of the discharge lamp and further deterioration of the discharge lamp.

[0008] The capacitor C14 corresponds to the higher lamp voltage.
Although the value of the preheating current can always be reduced by reducing the capacity of the preheating, the preheating current also decreases, and sufficient preheating cannot be performed. If the capacitance of the capacitor C14 is reduced, the value of the inductor L12 must be increased in order to obtain a resonance voltage, which leads to an increase in choke size, an increase in size of the device, and an increase in cost. On the other hand, if an attempt is made to secure the preceding preheating current, the lower limit of the lamp output at the time of dimming becomes high, that is, it becomes difficult to perform a sufficiently low output control.

In order to reduce the constant preheating current (especially, the constant preheating current at the time of dimming) while sufficiently securing the preceding preheating current, as shown in FIG. A winding preheating method using a series circuit of a transformer T3 and a capacitor C3 is well known.

The difference from the circuit shown in FIG. 4 is that a series circuit of a transformer T3 and a capacitor C3 and an inductor L1
, A capacitor C4 connected to the output terminal of the high-frequency power supply 4, a step-up transformer (hereinafter referred to as a transformer) T2 connected to both ends of the capacitor C4, and a series connection to a secondary winding of the transformer T2. By providing a capacitor C5,
This is because the winding preheating method is used, and the same components as those of the other circuits shown in FIG.

A resonance circuit is formed by the inductor L1 and the capacitor C4. The capacitors C2 and C5 are coupling capacitors. DC-DC conversion circuit 3
Is driven by a drive signal from the control circuit 5, and is composed of, for example, a step-up chopper circuit. The high frequency power supply 4 includes a series circuit of field effect transistors (hereinafter, referred to as switching elements) Q <b> 1 and Q <b> 2 connected to the output terminal of the DC-DC conversion circuit 3. , Q2 are alternately turned on and off, thereby converting the DC voltage output V1 of the DC-DC conversion circuit 3 into an AC high-frequency voltage. The capacitor C3 and the transformer T3 constitute a resonance system of the preheating circuit of the discharge lamp 8, and two secondary windings of the transformer T3 are connected between both filaments of the discharge lamp 8.

As shown in FIG. 5, in the resonance system of the preheating circuit, the preheating frequency can be secured by setting the preheating frequency fpf near the preheating resonance current fo '.
In the resonance system of the main circuit, the preheating current can always be gradually reduced by increasing the oscillation frequency at the time of dimming or at the time of full lighting.

With the above-mentioned configuration, the resonance system of the main circuit and the resonance system of the preheating circuit can be made independent from each other, so that a sufficient preheating current can be ensured, and at the time of dimming or full lighting. , The constant preheating current can be reduced.

However, in the circuit shown in FIG. 6, the preheating circuit becomes complicated, resulting in an increase in size and cost of the apparatus.

The present invention has been made in view of all of the above problems, and has as its object to use the C preheating method for a discharge lamp having a relatively high lamp voltage and to reduce the preheating current. It is an object of the present invention to provide a discharge lamp lighting device capable of reducing a constant preheating current at the time of dimming while securing.

[0016]

According to the first aspect of the present invention, there is provided a discharge lamp having a relatively high lamp voltage, a variable output DC voltage source, and a DC voltage source. A high-frequency power supply for converting the DC voltage output of the discharge lamp into an AC high-frequency voltage and supplying the discharge lamp, and a preheating capacitor connected between the non-power supply terminals of the discharge lamp. Is characterized in that the oscillation frequency is increased.

According to the second aspect of the present invention, there is provided a discharge lamp having a relatively high lamp voltage, a variable output DC voltage source, and a series circuit of at least two switching elements. It has a high-frequency power supply that converts the output into an AC high-frequency voltage and supplies it to the discharge lamp, and a preheating capacitor connected between the non-power supply terminals of the discharge lamp. Is controlled so that the ON time and the OFF time do not match.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the first or second aspect, the output voltage of the DC voltage source is reduced during dimming of the discharge lamp. .

According to a fourth aspect of the present invention, in the discharge lamp lighting device according to the first or third aspect, the DC voltage source includes at least one switching element, and the switching element of the DC voltage source is provided. Is characterized in that the output voltage is reduced by increasing the oscillation frequency.

According to the fifth aspect of the present invention, in the discharge lamp lighting device according to the second aspect, when dimming the discharge lamp, the on-time and the off-time of the switching element of the high-frequency power supply are inverted at regular intervals. It is characterized by doing.

According to a sixth aspect of the present invention, in the discharge lamp lighting device according to any one of the first to fifth aspects, the DC voltage source and the high-frequency power source include at least one switching element, and The switching element of the power source and the switching element of the high frequency power supply operate synchronously.

According to a seventh aspect of the present invention, in the discharge lamp lighting device according to any one of the first to sixth aspects, the discharge lamp has an electrode at one end and a closed portion at the other end. A plurality of annular arc tubes are arranged on substantially concentric circles, and one end near the other end is joined by a bridge joint to form one discharge path inside, and a coldest point exists near the other end. Further, the present invention is characterized in that it is an annular fluorescent lamp provided with a base surrounding at least one of one end and the other end.

[0023]

(Embodiment 1) FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

6 differs from the circuit of the prior art shown in FIG. 6 in that the discharge lamp 8 has a relatively high lamp voltage, a transformer T1 connected to the output terminal of the high-frequency power supply 4, and a capacitor connected to both ends of the transformer T1. C12, an inductor L11, and a series circuit of the discharge lamp 8, and a preheating capacitor 13 connected between the non-power-supply-side terminals of the discharge lamp 8;
11 and a capacitor C13 to form a resonance circuit.
The configuration is such that the oscillation frequency of the DC conversion circuit 3 and the oscillation frequency of the high-frequency power supply 4 are synchronized. The capacitors C11 and C12 are coupling capacitors. Then, when a current flows through the capacitor C13 via both filaments of the discharge lamp 8, both filaments are preheated and a resonance voltage is generated at both ends of the discharge lamp 8. The discharge lamp 8 includes, for example,
You may use a twin-Parok fluorescent lamp manufactured by Matsushita Electronics Corporation. Here, the twin-Parok fluorescent lamp is configured such that a plurality of annular arc tubes having an electrode at one end and a closed portion at the other end are arranged substantially concentrically, and the vicinity of the other end is joined by a bridge joint. A discharge path is formed therein, a cold spot exists near the other end, and an annular fluorescent lamp provided with a base surrounding at least one of the one end and the other end. It is.

The output voltage of the high-frequency power supply 4 is reduced by setting the oscillation frequency of the high-frequency power supply 4 higher than the oscillation frequency at the time of full lighting during dimming. As the oscillation frequency of the high-frequency power supply 4 increases, the oscillation frequency of the drive signal of the DC-DC conversion circuit 3 synchronized with the drive signal of the high-frequency power supply 4 increases, and the oscillation frequency of the drive signal of the DC-DC conversion circuit 3 increases. As a result, the output voltage V1 of the high-frequency power supply 4 decreases. Then, the constant preheating current at the time of dimming is reduced due to a decrease in the output voltage of the DC-DC conversion circuit 3 and the high-frequency power supply 4.

With the above configuration, the C preheating method is used for a discharge lamp having a relatively high lamp voltage without changing the capacity of the preheating capacitor, and the preheating current is secured while maintaining the preheating current. The constant preheating current at the time of dimming can be reduced.

(Embodiment 2) FIG. 2 shows an operation waveform diagram according to the present invention.

The circuit diagram is the same as that of the first embodiment shown in FIG. 1, and only the operation is different.
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

At the time of full lighting, the on-time and the off-time of the drive signal of the high-frequency power supply 4 are made substantially equal. At the time of dimming, the output voltage of the high-frequency power supply 4 is reduced by making the on-time and off-time of the drive signal of the high-frequency power supply 4 mismatch (unbalanced). When the drive signal of the high-frequency power supply 4 becomes unbalanced, the drive signal of the DC-DC conversion circuit 3 synchronized with the drive signal of the high-frequency power supply 4 also becomes unbalanced, and the drive signal of the DC-DC conversion circuit 3 becomes unbalanced. The output voltage V1 of the DC-DC conversion circuit 3
Decrease. Then, the constant preheating current at the time of dimming is reduced due to a decrease in the output voltage of the DC-DC conversion circuit 3 and the high-frequency power supply 4.

With the above configuration, the C preheating method is used for a discharge lamp having a relatively high lamp voltage, and the preheating current at the time of dimming is reduced while securing the preheating current. be able to.

(Embodiment 3) FIG. 3 shows an operation waveform diagram of a third embodiment according to the present invention.

The second embodiment differs from the second embodiment only in the control of the DC-DC conversion circuit 3 and the high-frequency power supply 4. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals. Description is omitted.

That is, when the driving signal of the high-frequency power supply 4 is unbalanced at the time of dimming, as shown in FIGS. 3A and 3B, at regular intervals (for example, half of the AC lamp current). Inverts the unbalance condition between the switching elements Q1 and Q2 (per cycle).

With the above configuration, it is possible to improve the cataphoresis phenomenon caused by the difference in the positive and negative peak values of the lamp current waveform, etc., and to use the C preheating method for a discharge lamp having a relatively high lamp voltage. And the preheating current at the time of dimming can be reduced while the preheating current is secured.

Note that all the above embodiments may be appropriately combined as long as the functions and effects of the present invention are satisfied.

[0036]

According to the first, third, fourth, sixth, and seventh aspects of the present invention, a discharge lamp having a relatively high lamp voltage without changing the capacity of a preheating capacitor. In contrast, it is possible to provide a discharge lamp lighting device that uses the C preheating method and can always reduce the preheating current during dimming while securing the preheating current.

According to the second to seventh aspects of the present invention, it is possible to improve the cataphoresis phenomenon caused by the difference in the positive and negative peak values of the lamp current waveform without changing the capacity of the preheating capacitor. While using the C preheating method for discharge lamps with relatively high lamp voltage,
Further, it is possible to provide a discharge lamp lighting device capable of always reducing the preheating current at the time of dimming while securing the preceding preheating current.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

FIG. 2 shows an operation waveform diagram of a second embodiment according to the present invention.

FIG. 3 shows an operation waveform diagram of a third embodiment according to the present invention.

FIG. 4 shows a circuit diagram of a conventional example according to the present invention.

FIG. 5 is a diagram showing frequency characteristics of a filament current in a conventional example according to the present invention.

FIG. 6 is a circuit diagram of another conventional example according to the present invention.

FIG. 7 shows an example of a lamp voltage of the discharge lamp according to the present invention.

[Explanation of symbols]

 3 DC voltage source 4 High frequency power supply 8 Discharge lamp Q Switching element

Continued on the front page F term (reference) 3K072 AA02 BA03 BA05 BC01 BC03 DB03 DD04 GA02 GB04 GB12 GC04 HA06 HA10 HB03 3K098 CC56 CC62 DD22 DD37 EE13 EE14 EE31 EE32 5H007 AA06 BB03 CA02 CB04 CB17 CB22 CC12 CC32 DA03 DB01

Claims (7)

[Claims] A discharge lamp having a relatively high lamp voltage, a variable output DC voltage source, and a high frequency power supply for converting the DC voltage output of the DC voltage source into an AC high frequency voltage and supplying the AC high frequency voltage to the discharge lamp. And a preheating capacitor connected between the non-power-supply-side terminals of the discharge lamp, wherein the oscillation frequency of the high-frequency power supply is increased during dimming of the discharge lamp. 2. A discharge lamp having a relatively high lamp voltage, a variable output DC voltage source, and a series circuit of at least two switching elements. The DC voltage output of the DC voltage source is converted to an AC high frequency voltage. A high-frequency power supply that converts and supplies the high-frequency power to the discharge lamp; and a preheating capacitor connected between the non-power-supply-side terminals of the discharge lamp. A discharge lamp lighting device, wherein the discharge time and the off time do not match. 3. The discharge lamp lighting device according to claim 1, wherein the output voltage of the DC voltage source is reduced when dimming the discharge lamp. 4. The DC voltage source according to claim 1, wherein the DC voltage source includes at least one switching element, and an output voltage is reduced by increasing an oscillation frequency of the switching element of the DC voltage source. Claim 3
The discharge lamp lighting device according to any one of the above. 5. The discharge lamp lighting device according to claim 2, wherein, when dimming the discharge lamp, an on-time and an off-time of a switching element of the high-frequency power supply are inverted at regular intervals. 6. The DC voltage source and the high frequency power supply include at least one switching element, and the switching element of the DC voltage source and the switching element of the high frequency power supply operate synchronously. The discharge lamp lighting device according to any one of claims 1 to 5, characterized in that: 7. The discharge lamp has a plurality of annular arc tubes each having an electrode at one end and a closed portion at the other end arranged substantially concentrically, and joining the vicinity of the other end with a bridge joint. Accordingly, one discharge path is formed inside, and a cold spot exists near the other end, and a ring-shaped fluorescent light having a base surrounding at least one of the one end and the other end is provided. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a lamp.