JP2842489B2 - High pressure discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure discharge lamp lighting device, and more particularly to an improvement in light emission characteristics at the time of starting.

[0002]

2. Description of the Related Art Conventionally, for this type of device, for example, Japanese Patent Application Laid-Open No. 2-136342 discloses that a lighting operation is performed in a control mode shown in FIG. That is, A is a control mode when the metal halide lamp is turned on for the first time, that is, at the time of a cold start. After the initial current flows for a certain period of time immediately after lighting, the current exponentially attenuates and shifts to a steady current. B is a control mode in which relighting is performed within a certain time after the lamp is turned off, and the current increases exponentially from a large current immediately after lighting and shifts to a steady current. C is a control mode at the time of re-lighting during about 0 to 18 seconds after turning off the lamp, that is, a hot start control mode.

[0003]

However, the lighting operation in the above-described control mode has the following problems. a. For a very short period immediately after the discharge lamp is turned on, the luminous efficiency is high due to the action of xenon gas inside the discharge lamp. Particularly, at the time of hot start, the temperature inside the discharge lamp is high and the luminous efficiency immediately after lighting is extremely high. For this reason, a flash may be generated during this period. In particular, at the time of hot start, flashing occurs even if the lamp current value is set to the rated current value.

B. At the time of a hot start, sodium is strongly emitted in the discharge lamp, and the discharge lamp emits red light until the discharge is stabilized, resulting in poor visibility .

The present invention has been made to solve such a problem, and provides a high-pressure discharge lamp lighting device in which a flash is not likely to occur immediately after lighting, and the color of light is fast and stable at a hot start. The purpose is to do so.

[0006]

In order to achieve the above object, according to the present invention, the lamp current is made smaller than the steady-state current for a very short period of time when the luminous efficiency immediately after lighting is high to suppress the generation of flash light. The lamp current is made larger than the steady-state current to accelerate the excitation of metals other than sodium in the discharge lamp, thereby stabilizing the color of light quickly.

That is, according to the present invention, a high pressure discharge lamp lighting device is configured as in the following (1) and (2).

(1) Lamp voltage detecting means, lamp current detecting means, and a lamp current value at the time of rated power lighting or a value corresponding thereto is detected based on outputs of the lamp voltage detecting means and the lamp current detecting means. Based on the storing means and the value at the time of the previous rated output lighting stored in this means, for a short time immediately after lighting, the lamp current value is controlled to be smaller than the lamp current value at the time of the previous rated power lighting. ,
Thereafter, a control means for controlling the lamp current value to a steady current value from a value larger than the lamp current value at the time of lighting the rated power last time is provided.

(2) The control means controls the lamp current value from a value larger than the lamp current value at the time of the previous rated power lighting to a steady current value. The high-pressure discharge lamp lighting device according to the above (1), wherein the control is performed such that the hot start is larger than the cold start.

[0010]

According to the constitutions (1) and (2), the lamp current becomes smaller than the steady-state current for a very short period immediately after lighting, thereby suppressing the occurrence of flashing. After that, the lamp current becomes larger than the steady-state current for a predetermined period. , Accelerates the excitation of metals other than sodium.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. FIG. 1 is a block diagram of a "high pressure discharge lamp lighting device" according to an embodiment. As shown in FIG.
A booster circuit 3 composed of a DC converter, boosts the voltage to a predetermined voltage, converts the AC voltage to a desired frequency by an inverter circuit 4, and supplies a metal halide lamp (encloses an iodide-based metal halide ) 6 through an LC resonance circuit 5. Is applied. LC
The resonance circuit 5 generates a high voltage by LC resonance at the start of lighting and applies it to the metal halide lamp 6, and after lighting, operates as an inductive current limiting element.

The control circuit 7 detects the lamp voltage and the lamp current, and controls the inverter circuit 4 at the time of the previous rated power supply.
The operating frequency of the inverter circuit 4 is controlled such that the lamp current value becomes smaller than the lamp current value at the time of the previous rated power lighting for a very short period immediately after the lighting based on this storage. The operating frequency of the inverter circuit 4 is controlled so that the lamp current value becomes larger than the lamp current value when the rated power is turned on to the steady current value.

FIG. 2 is a flowchart showing the operation of the control circuit 7. Hereinafter, according to this flowchart, the control circuit 7
Will be described. In step 10 (hereinafter referred to as S10), it waits until the lighting switch 2 is turned on, and when it is turned on, it checks in S11 whether the operating frequency f _S of the inverter circuit 4 at the time of the previous lighting of the rated power is stored and stored. If not, normal metal halide lamps assuming stores the highest frequency in the operating frequency range of the inverter circuit 4 can be taken when the rated power lighting and f _S. In this embodiment, since the lamp frequency is changed by changing the operating frequency of the inverter circuit 4, the operating frequency of the inverter circuit 4 during the previous operation of the rated power corresponds one-to-one with the lamp current during the previous operation of the rated power. doing.

In S13, the operating frequency f of the inverter circuit 4
Is set to the LC resonance frequency f _O of the LC resonance circuit 5 and a high voltage is applied to the metal halide lamp 6.

At S14, the lamp voltage _VL is read, and at S1
5 In the lamp voltage V _L is checked or less than the predetermined voltage V _A, a metal halide lamp 6 equal to or less than V _A moves to step S16 to determine that the dielectric breakdown on.

In S16, an initial value _TINT is set in the timer T, and in S17 and S18, the operating frequency f of the inverter circuit 4 is set.
For a very short time f _S + f _d until the timer T reaches zero.
In other words, the inverter circuit 4 when the previous rated power was turned on
Operation by increasing only the frequency f _S than f _d, and controls so that the lamp current value is smaller than the lamp current value, i.e. steady-state current value at rated power lighting of the previous. Note that when assuming f _INT to f _S in S12 is controlled to a small lamp current value than the minimum of the lamp current value that can be taken at rated power lighting. The timer T is counted down by the processing of FIG. 3 executed by interrupting the processing of FIG. 2 at predetermined time intervals.

In S19, the correction coefficient K of the power supplied to the metal halide lamp 6 is set to 1.0. S20 reads the lamp voltage V _L, the lamp voltage V _L in S21 is equal to or greater than a predetermined value V _TH, sets the correction coefficient K in step S22 it is determined that the hot start in K _P 1.0 or more values , and to set the tailing time T _P in the timer T. At the time of cold start, the process bypasses S22. At S23, the lamp voltage V _L and the lamp current I _L are read, and at S24, the lamp power P _L is calculated.

[0018] S25 in lamp power P _L stores the operating frequency of the inverter circuit 4 at that time as f _S in S26 if Osame' to the P _SH no range P _SL of the rated power.

Check whether timer T is zero in S27
I do. If the timer T is zero, a new timer T is set in S28.
Set T _D in, s K _D supply power correction coefficient K in S29
S3 so that K does not become 1.0 or less.
Clip at 0, S31. Timer T
Since the countdown is performed by the process of 3, every time T _D
Then, the processing of S27 to S31 is performed.

In step S32, the current lamp voltage _{VL is used as} shown in FIG.
The V _L -P _OBJ table is searched to find P _OBJ , and S3
In step 3, K is multiplied by K to determine the supply power P _OBJ .

In step S34, a deviation ΔP between the supplied power P _OBJ and the current lamp power P _L is obtained. If ΔP is not zero in step S35, the ΔP-f _P table shown in FIG.
Obtaining a corresponding frequency correction value f _P a.

[0022] When the current lamp power P _L in S37 is less than the supply power P _OBJ determined in S33, the lamp power increases the lamp current I _L by lowering the operating frequency f of the inverter circuit 4 by the correction amount f _P at S38 If P _L is increased and, conversely, P _L is larger than P _OBJ , the operation frequency f of the inverter circuit 4 is increased by the correction amount f _P to decrease the lamp power P _L in S39, and the process proceeds to S23. S3
9 is repeated.

By the way, as shown in FIG. 6, the lamp voltage starts from a low place during a cold start,
In a hot start, it starts from a high place. According to this characteristic, as described above, during a cold start,
Although the correction coefficient K of the supply power remains initialized to 1.0 with S19, when the hot start, resetting the correction coefficient K to 1.0 or more K _P in S22, thereafter 1.0 Until the predetermined time T _D , it is reduced by K _D in S29 every time.

In this way, as shown in FIG. 7, the lamp current is set to a value smaller than the lamp current value at the time of the previous lighting of the rated power for a very short period immediately after the lighting, regardless of the cold start and the hot start. After that, it is controlled to a value larger than the lamp current value at the time of the previous lighting of the rated power. In addition, when the lamp voltage is the same, control is performed so that the lamp power is larger at the time of the hot start than at the time of the cold start, that is, the lamp current is increased. As the “short period”, 5 msee or more is provided within one second after lighting.

The tables shown in FIGS. 4 and 5 are actually digital data stored in a memory, but are represented by analog curves for easy understanding.

In the embodiment, the lamp current is controlled by changing the operating frequency of the inverter circuit. However, the present invention is not limited to this. For example, the lamp current is controlled by changing the output voltage of the booster circuit. Can also be implemented.

[0027]

As described above, according to the present invention, since the lamp current value is controlled to be smaller than the lamp current value at the time of the previous rated power lighting, that is, the steady-state current value, for a very short period immediately after lighting, the flash is generated. Since it does not occur, the lamp current value is controlled so that it becomes a steady current from a value larger than the lamp current value at the time of the previous rated power lighting. Excitation of the metal is fast, and the color of light is fast and stable. According to the second aspect of the present invention, the color of light at the time of a hot start is stabilized rapidly.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a flowchart showing an operation of a control circuit in the embodiment.

FIG. 3 is a flowchart showing the operation of a timer T of FIG. 2;

FIG. 4 V _L- P _OBJ table

FIG. 5: ΔP-f _P table

FIG. 6 is a time-lamp voltage characteristic diagram.

FIG. 7 is a time-lamp current characteristic diagram.

FIG. 8 is a control mode diagram of a conventional example.

[Explanation of symbols]

 4 Inverter circuit 6 Metal halide lamp 7 Control circuit

Continuation of the front page (56) References JP-A-2-174902 (JP, A) JP-A-3-138894 (JP, A) JP-A-4-190595 (JP, A) JP-A-7-39263 (JP) , B2) JP 6-103637 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 41/14-41/29

Claims (2)

(57) [Claims] 1. A lamp voltage detecting means, a lamp current detecting means, and a lamp current value at the time of rated power lighting or a value corresponding thereto is detected and stored based on outputs of the lamp voltage detecting means and the lamp current detecting means. Means for controlling the lamp current value to be smaller than the lamp current value at the time of the previous rated power lighting for a short time immediately after the lighting, based on the value at the time of the previous rated output lighting stored in the means, And a control means for controlling the lamp current value from a value larger than the lamp current value at the time of the previous rated power lighting to a steady current value. 2. The control means, when controlling the lamp current value from a value larger than the lamp current value at the time of lighting of the previous rated power to a steady current value, sets the lamp current value to a hot value in the case of the same lamp voltage. 2. The high pressure discharge lamp lighting device according to claim 1, wherein control is performed such that the start time is larger than the cold start time.