JPH04342988A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To attain the rated value quickly and without overshoot or undershoot of the light flux of a discharge lamp at the time of starting, without being influenced by dispersion in the characteristics from lamp to lamp and also secular change of the applicable lamp. irrespective of the mode of starting, i.e., cold or hot start. CONSTITUTION:Until the lamp voltage of a discharge lamp 6 attains the specified voltage value determined on the basis of the final lamp voltage at the time it was lighted up at the rating in previous run, a control unit 7 controls the power determined on the basis of this lamp voltage so that it becomes the control target power which has been corrected with the final lamp voltage and the lamp voltage immediately after being lighted up. After the lamp voltage has attained the specified voltage value, the lamp power is decreased gradually at certain intervals depending upon the lamp voltage immediately after being lighted up so that the rated power is obtained.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a lighting device for discharge lamps such as high-pressure mercury lamps and metal halide lamps.
In particular, it relates to control of lamp power during startup.

0002

[Prior Art] This type of lighting device, for example, is disclosed in Japanese Patent Application No. 2-215090, in which the current flowing through the discharge lamp is gradually reduced over time from the start of lighting to the transition to a stable discharge state. It has been proposed to change the width of the gradual decrease to different values from the start of lighting up to a predetermined time and after that time.

0003

However, the above-mentioned discharge lamp lighting device in which the lamp current gradually decreases over time after starting lighting has the following problems a and b.

[0004]a. When starting a discharge lamp when the temperature of the discharge lamp itself is high immediately after extinguishing it (hereinafter referred to as a hot start), unlike starting when the temperature of the discharge lamp itself is low (hereinafter referred to as a cold start), the temperature of the discharge lamp itself is higher than necessary. Electric power is supplied to the discharge lamp, significantly shortening the life of the discharge lamp. Furthermore, during a hot start, the luminous flux overshoots.

[0005]b. Variations in the characteristics of individual discharge lamps,
Due to differences in characteristics of discharge lamps due to aging, the rise of the luminous flux at the time of starting the discharge lamp varies with the same current change pattern. Furthermore, depending on the discharge lamp, more power may be supplied than necessary, significantly shortening the life of the discharge lamp.

[0006] This invention was made to solve such problems, and whether it is a cold start or a hot start, variations in the characteristics of individual discharge lamps, and changes over time of discharge lamps. It is an object of the present invention to provide a discharge lamp lighting device in which the luminous flux of a discharge lamp quickly reaches a rated value without overshooting or undershooting during startup.

[0007]

[Means for Solving the Problems] First, the characteristics of the discharge lamp and the means for solving the problems will be briefly explained. Figure 12 shows the ramp voltage rise characteristics of a discharge lamp during a cold start.
FIG. 13 shows the lamp voltage vs. lamp luminous efficiency characteristics. As shown in the figure, the lamp voltage gradually increases during startup, and as the lamp voltage increases, the lamp luminous efficiency also increases.

[0008] Therefore, by estimating the lamp luminous efficiency from the lamp voltage and supplying power greater than the rated power to the discharge lamp according to the lamp luminous efficiency at that time, the luminous flux of the discharge lamp can be quickly adjusted to the rated luminous flux at the time of startup. The value can be reached.

However, near the final value of the lamp voltage, while the lamp voltage rises slowly, the lamp luminous efficiency rises rapidly. Therefore, in order to determine the control target lamp power from the lamp voltage, It is necessary to improve the detection accuracy of the lamp voltage, which is costly. Therefore, when the lamp voltage exceeds a predetermined voltage, the control target lamp power is gradually decreased over time.

Furthermore, as shown in FIGS. 12 and 13, due to variations in the characteristics of individual discharge lamps and differences in characteristics due to aging of discharge lamps, the rise characteristics of the lamp voltage, the lamp voltage-lamp luminous efficiency characteristics, and the lamp voltage The final values of are different. Therefore, by memorizing the final lamp voltage from the last time the rated lamp was lit, determining the predetermined voltage based on the final lamp voltage, and correcting the control target lamp power, the characteristics of each discharge lamp can be adjusted. scattering,
Differences in characteristics due to aging of discharge lamps can be absorbed.

[0011] If the final lamp voltage the last time the lamp was lit at the rated value is not stored, a value near the lowest possible lamp voltage when a normal discharge lamp is lit at the rated value is used as the final lamp voltage when the lamp was last lit at the rated value. Control is performed assuming that the voltage is the same, and prevents excessive power from being supplied to the discharge lamp during startup.

Next, FIG. 14 shows the rise characteristics of the lamp voltage of the discharge lamp during cold start and hot start. As shown in the figure, the rise characteristics of the lamp voltage are different between a cold start and a hot start. Therefore, by correcting the control target lamp power according to the lamp voltage immediately after lighting, and by changing the ratio of lamp power reduction to time, appropriate power can be applied regardless of cold start or hot start.

[0013] The above solution means is shown in the following structure (
1). (1) A discharge lamp lighting device comprising the following components a, b, c, and d. a. Final lamp voltage storage means for storing the final lamp voltage when the discharge lamp was last lit at its rated value. b. Lamp voltage detection means for detecting a lamp voltage of the discharge lamp. c. When the final lamp voltage is stored in the final lamp voltage recording means, the final lamp voltage is stored, and when it is not stored, a value near the lowest lamp voltage that can be obtained when a normal discharge lamp is lit at its rated value is stored as the final lamp voltage. The electric power determined based on the lamp voltage detected by the lamp voltage detection means is determined based on the final lamp voltage determined previously and the lamp voltage immediately after lighting detected by the lamp voltage detection means. Control target power determining means that corrects and determines the control target power. d. The lamp voltage detected by the lamp voltage detection means is
Until the predetermined voltage determined based on the final lamp voltage determined previously is reached, the power supplied to the discharge lamp is
Control is performed so that the control target power is determined by the control target power determining means, and after the lamp voltage exceeds the predetermined voltage, the power supplied to the discharge lamp is adjusted according to the lamp voltage immediately after lighting. Lamp power control means that gradually decreases the power in proportion to time and controls the power to the rated power after reaching the rated power.

[0014]

[Operation] With the configuration (1) above, when starting a discharge lamp, the lamp power is controlled to the control target power until the lamp voltage reaches a predetermined voltage, and after exceeding the predetermined voltage, the lamp power is The power is gradually reduced at a rate corresponding to the lamp voltage immediately after lighting, and when the rated power is reached, the power is controlled to the rated power thereafter.

[0015]

[Examples] The present invention will be explained in detail below using examples. FIG. 1 is a circuit diagram of a "discharge lamp lighting device" which is an embodiment, and FIGS. 2 to 5 are flowcharts showing its operation.

In FIG. 1, 1 is a battery as a power source;
2 is a discharge lamp lighting switch, 3 is a DC-DC converter circuit that increases the battery voltage to the required voltage, and 4 is a DC
- It is an inverter that converts the DC output of the DC converter circuit 3 into AC of a required frequency.

Reference numeral 5 denotes an LC series circuit that operates as a high voltage generator at a resonant frequency f0 during startup, and then operates as a ballast at a frequency lower than the resonant frequency f0. 6
is a discharge lamp. A control unit 7 detects whether the discharge lamp lighting switch is on or off, detects the lamp voltage of the discharge lamp 6, controls the output frequency of the inverter circuit 4, and controls the lamp power.

Hereinafter, with reference to FIGS. 2 to 11,
Explain the operation. First, wait until the discharge lamp lighting switch 2 is turned on (see S10), and when it is turned on (S10, YES).
S), it is checked whether the final lamp voltage VOLD of the discharge lamp 6 when the discharge lamp was lit last time was memorized (S11). If it is stored, the value VOLD is used, and if it is not stored, the lowest lamp voltage value Vmin that can be taken when a normal discharge lamp is lit at its rated value is assumed to be the final lamp voltage VOLD (S12).
The D-VTH table (see FIG. 6) is searched to obtain the predetermined voltage VTH (S13), and the VOLD-KW1 table (FIG. 7) is searched to determine the coefficient K for correcting the control target power.
W1 is determined (S14).

In S15, the operating frequency of the inverter circuit 4 is set to the resonance frequency f0 of the LC series circuit 5, and a high voltage is applied to the discharge lamp 6 by utilizing the series resonance of the LC series circuit 5, so that the discharge lamp 6 is turned on. Read the lamp voltage VL (S16), wait until the value becomes less than a predetermined value VA (S17), and set the operating frequency of the inverter circuit 4 to the frequency f at which the current supplied to the discharge lamp 6 becomes the rated current.
1. (S18).

In S19, the lamp voltage VL1 immediately after lighting is read, and the VL1-TD table (FIG. 8) is searched to find the time TD for decreasing the lamp power by one step (S2
0), sets this time TD to timer T (S21),
Furthermore, the VL1-KW2 table (Fig. 9) is searched to find the coefficient KW2 for correcting the control target power (S22), the lamp voltage VL is read (S23), and the VL-WO1 table (Fig. 10) is searched to perform basic control. Find the target power WO1 (S24), and use the previously found coefficients KW1 and KW2 as WO1.
The true control target power WOBJ is determined by multiplying by (S2
5).

If in S26 the lamp voltage VL is smaller than the predetermined voltage VTH determined in S13 (S26, NO), the inverter operating frequency setting subroutine (FIG. 4) is called (S27).

In this subroutine, the control target power WO
Check whether BJ exceeds the maximum power WMAX of the discharge lamp 6, and if it does not exceed it (S40, NO), W
Let OBJ be the control target power as it is, and if it exceeds (
S40, YES), WMAX is controlled by target power WOBJ
(S41), this control target electric power WOBJ is divided by the lamp voltage VL to calculate the control target current IOBJ (S42), and this control target current IOBJ is the maximum current I
It is checked whether it exceeds MAX. If it is not exceeded (S43, NO), that IOBJ is used as the control target current IOBJ, and if it is exceeded (S43, YES).
S), IMAX is the control target current IOBJ (S
44), search the IOBJ-f table (Fig. 11) to find the required frequency, and calculate the output frequency f of the inverter circuit 4.
is controlled so that it becomes the desired frequency.

Read the lamp voltage VL again (S23
), the operations of S23 to S27 are repeated, and the lamp power becomes the control target power WOBJ according to the lamp voltage VL.
The output frequency f of the inverter circuit 4 is controlled so that

When the lamp voltage VL exceeds the predetermined voltage VTH (S26, YES), the lamp voltage VL is read in S28 (FIG. 3), and after waiting for the timer T to become zero (S28, YES), the lamp voltage VL is read in S28 (FIG. 3).
29), set the time TD obtained in S20 to the timer T (S30), and gradually decrease the control target power WOBJ by one step (
S31), checks whether WOBJ exceeds the rated power, and if it does (S32, YES), calls the inverter operating frequency setting subroutine (Fig. 4) (S35), and sets the output frequency f of the inverter circuit 5. The lamp power is controlled to the control target power WOBJ by controlling the frequency to be the frequency determined in the subroutine.

If WOBJ does not exceed the rated power WST in S32 (S32, NO), WST is set as the control target power WOBJ (S33), and the lamp voltage VL is read and stored as the final lamp voltage VOLD (S34). ), inverter operating frequency setting subroutine (
4) and sets the operating frequency f of the inverter circuit 5 to control the lamp power to the rated power WST. Thereafter, the operations from S28 to S35 are repeated. Note that the processing in Figures 2, 3, and 4 is interrupted every second, and the processing in Figure 5 is performed.
Count down timer T.

In the above embodiment, the time TD for decreasing the lamp voltage by one step is changed depending on the lamp voltage VL1 immediately after lighting, but the present invention is not limited to this. It may be implemented by changing the width of the power reduction per unit, and in short, the "ratio to time" of the power reduction may be changed in accordance with the lamp voltage VL1 immediately after lighting.

Further, in the embodiment, the lamp power is controlled by changing the operating frequency f of the inverter, but the present invention is not limited to this, and the operating frequency of the inverter is fixed and the lamp power is controlled by changing the operating frequency f of the inverter. The lamp power can be controlled by an appropriate method such as controlling the lamp power by changing the output voltage.

[0028]

[Effects of the Invention] As explained above, according to the present invention, the start-up can be performed regardless of cold start or hot start, and regardless of variations in the characteristics of individual discharge lamps or changes over time of discharge lamps. The luminous flux of the discharge lamp quickly reaches a steady value without overshooting or undershooting.

[Brief explanation of drawings]

[Figure 1] Circuit diagram of the embodiment

[Figure 2] Flowchart showing the operation of the embodiment

[Figure 3] Flowchart showing the operation of the embodiment

[Figure 4] Flowchart showing the operation of the embodiment

[Figure 5] Flowchart showing the operation of the embodiment

[Figure 6] Diagram showing the VOLD-VTH table

[Figure 7] Diagram showing the VOLD-KW1 table

[Figure 8
] Diagram showing the VL1-TD table

[Figure 9] VL1-K
Diagram showing W2 table

[Figure 10] Diagram showing the VL-WO1 table

[Figure 11] Diagram showing IOBJ-f table

[Figure 12] Rising characteristic diagram of lamp voltage

[Figure 13] Lamp voltage vs. lamp luminous efficiency characteristic diagram

[Figure 14] Lamp voltage rise characteristic diagram during cold start and hot start

[Explanation of symbols]

6 Discharge lamp 7 Control unit

Claims (1)

[Claims] 1. A discharge lamp lighting device characterized by comprising the following components a, b, c, and d. a. Final lamp voltage storage means for storing the final lamp voltage when the discharge lamp was last lit at its rated value. b. Lamp voltage detection means for detecting a lamp voltage of the discharge lamp. c. When the final lamp voltage is stored in the final lamp voltage recording means, the final lamp voltage is stored, and when it is not stored, a value near the lowest lamp voltage that can be obtained when a normal discharge lamp is lit at its rated value is stored as the final lamp voltage. The electric power determined based on the lamp voltage detected by the lamp voltage detection means is determined based on the final lamp voltage determined previously and the lamp voltage immediately after lighting detected by the lamp voltage detection means. Control target power determining means that corrects and determines the control target power. d. The lamp voltage detected by the lamp voltage detection means is
Until the predetermined voltage determined based on the final lamp voltage determined previously is reached, the power supplied to the discharge lamp is
Control is performed so that the control target power is determined by the control target power determining means, and after the lamp voltage exceeds the predetermined voltage, the power supplied to the discharge lamp is adjusted according to the lamp voltage immediately after lighting. Lamp power control means that gradually decreases the power in proportion to time and controls the power to the rated power after reaching the rated power.