JPH0521176A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Summary] [Objective] To obtain a discharge lamp lighting device capable of controlling a stable light quantity without being affected by variations in individual discharge lamps, aging, or lamp characteristics due to internal conditions. [Structure] The light amount of the discharge lamp 5 is detected by the photodetector 7,
Based on the value, the electric power supplied to the discharge lamp 5 is controlled to control the lighting of the discharge lamp 5. [Effect] Stable and always reliable lighting control of the discharge lamp is performed without depending on variations of the discharge lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to controlling the amount of light emitted from a discharge lamp.

[0002]

2. Description of the Related Art FIG.
It is a block diagram which shows the conventional discharge lamp lighting device described in the publication. In FIG. 7, 1 is a power supply serving as an energy supply source, 2 is a power converter such as a full-wave rectifier, 3 is an inverter circuit for converting the power from the power converter 2 into AC power having a predetermined frequency, and 4 is this inverter circuit. A series resonance circuit 5 including a choke coil L and capacitors C1 and C2 connected to 3 is a discharge lamp.

Reference numeral 6 is a control means, which outputs a signal S1 for controlling the inverter circuit 3. The series circuit of the capacitors C1 and C2 is for detecting the terminal voltage of the discharge lamp 5 as the voltage value Vc, and the resistor R connected in series to the discharge lamp 5 is the discharge flowing through the discharge lamp 5. It is for detecting the current as a voltage value VR.

FIG. 8 is a flow chart showing the operation process of the conventional discharge lamp lighting device shown in FIG. 7. The operation will be described below with reference to FIG. When a light switch (not shown) for operating blinking of the discharge lamp is turned on, the control means 6 first sets the frequency of the signal S1 to 100 kHz (step 801). As a result, the inverter circuit 3 has 100
It generates AC power of kHz and outputs it to LC series resonance circuit 4
By applying the voltage to the discharge lamp 5, a high voltage of about 10 kV is applied to both ends of the discharge lamp 5.

Next, the control means 6 controls the capacitors C1 and C2.
From the voltage value Vc at the connection point of or the voltage value VR of the resistor R, it is determined whether or not insulation breakdown has occurred in the discharge lamp 5 (step 802). The value of Vc shows a high value when the enclosed gas of the discharge lamp 5 is in an insulating state and a low value when the insulation is broken, and the value of VR is 0 during the insulation and after the insulation breakdown. Since it becomes large, it is possible to determine whether or not the dielectric breakdown has occurred by comparing the value of Vc or VR with the predetermined value Vs.

Next, when dielectric breakdown occurs, the signal S
The frequency of 1 is set to a low initial value, for example, 4 kHz (step 803). In the LC series resonance circuit 4 as shown in FIG. 7, even if the voltage applied to the LC series resonance circuit 4 is fixed, if the frequency is changed, the discharge current flowing through the discharge lamp changes. That is, when the frequency becomes higher, the current decreases due to L, and when the frequency becomes lower, the current increases. Therefore, the frequency of the signal S1 is lowered to 4
If it is set to kHz, the discharge current can be made a large value.

Next, it is determined whether 100 mS has elapsed (step 804). When 100 mS has elapsed, the signal S1 is output.
Frequency is increased by 50 Hz (step 80
5). Next, it is determined whether or not the frequency of the signal S1 reaches 6 kHz (step 806), and steps 804 and 805 are repeated until the frequency reaches 6 kHz, and the frequency is increased by 50 Hz every 100 mS. When it reaches 6 kHz, 10
The frequency to be added every 0 mS is set to 100 Hz (steps 807 and 808). And the frequency of the signal S1 is 10k
When Hz is reached, the value is fixed (step 80).
9).

[0008]

The conventional discharge lamp lighting device has the following problems because the power supply pattern to the discharge lamp is fixed to one. 1. Since characteristics such as light emission efficiency are different for each discharge lamp due to variations in the discharge lamp and aging, the rising characteristics of light are different for each discharge lamp. 2. Depending on the internal state of the discharge lamp, more power than necessary is supplied and the light output overshoots significantly. 3. Since the light emission phenomenon is indirectly captured by the voltage, there is a possibility of erroneous recognition, and a stable start of the discharge lamp cannot be realized. Such a problem makes it difficult to mount it on a portion where high stability and high reliability are required, such as a headlight of a vehicle.

The present invention has been made in order to solve the above-mentioned problems, and provides reliable detection of starting and quick control to a prescribed light amount regardless of variations in discharge lamps, aging, or lamp states. It is possible to obtain a discharge lamp lighting device capable of performing stable lighting control of the discharge lamp.

[0010]

DISCLOSURE OF THE INVENTION A discharge lamp lighting device according to the present invention supplies power to a power supply means for supplying power to a discharge lamp based on a detection amount of a light detection means for detecting the light emission amount of the discharge lamp. Is provided with control means for controlling.

Further, the light detecting means is constituted by one having a spectral sensitivity characteristic close to the relative luminous efficiency.

[0012]

In the discharge lamp lighting device according to the present invention, the light which is the direct output amount of the discharge lamp is detected by the light detecting means, and the electric power to the discharge lamp is controlled by the control means on the basis of the detected light. The reliable control of is performed.

Further, the electric power to the discharge lamp is controlled based on the value detected by the photo-detecting means having the spectral sensitivity characteristic which is close to the relative luminous efficiency, and the control close to human sense is performed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. In FIG. 1, 1 is a DC power source serving as an energy supply source, 2 is a power converter such as a DC-DC converter which boosts a DC voltage supplied from the DC power source 1 to a predetermined voltage, and 3 is this power converter. An inverter circuit for converting DC power obtained from 2 into AC power of a predetermined frequency,
Reference numeral 4 denotes a series resonance circuit composed of a choke coil L and a capacitor C, which constitute power supply means. A discharge lamp 5 is connected to both ends of the capacitor C of the series resonance circuit 4.

Reference numeral 6 is a control means, which is composed of a dedicated analog or digital circuit, a microcomputer, or the like, and outputs a signal for driving the inverter 3. 7
Is a photodetector 7 such as a photodiode for measuring the light output amount of the discharge lamp 5 and is connected to the control means 6. Reference numeral 8 is a target value setting means for setting the target light output amount of the discharge lamp 5, and 9 is a switch for instructing the control means 6 to start lighting and turn off the discharge lamp 5.

FIG. 2 is a flow chart showing the operation of the embodiment shown in FIG. The operation will be described below with reference to FIG. When the switch 9 connected to the control means 6 is closed and a command is given to turn on the discharge lamp 5 (step 201), the control means 6
Represents the frequency output S1 corresponding to the resonance frequency fo determined by the circuit constant LC of the series resonance circuit 4 and the inverter circuit 3
(Step 202).

The inverter circuit 3 converts the power supplied from the DC power supply 1 into a high frequency power of foHz and supplies it to the series resonance circuit 4. A high voltage is generated across the capacitor C of the series resonance circuit 4 due to the resonance phenomenon. When this high voltage is applied to the discharge lamp 5, the discharge lamp 5 causes insulation breakdown and starts discharge, and at the same time causes a light emission phenomenon. This light emission is detected by the photodetector 7.

As shown in FIG. 3, when the light output above a predetermined threshold value is detected (step 203), the control means 6 recognizes the start of discharge of the discharge lamp 5 and releases the lighting power. The frequency output S1 is lower than fo to be added to the electric lamp 5, for example, fs is determined from the maximum current of the discharge lamp 5, the inverter output voltage, and the inductance L of the series resonance circuit.
Is applied to the inverter 3 (step 204). In this way, the discharge lamp 5 is started.

FIG. 4 is a characteristic diagram showing a change in the light output when the discharge lamp is lit. The flow quantity of FIG. 4 and FIG. 2 quickly controls the light quantity output from the discharge lamp 5 which has started the discharge to a prescribed light quantity. I will explain how to do. First, the control means 6 reads the light output value X1 of the discharge lamp 5 by the photodetector 7 (step 205), and compares it with the target value Xt preset by the target value setting means 8 (step 206). The frequency to be output to the inverter 3 is determined (step 207) and output at that frequency (step 2).
08) The method of comparison calculation determines the control amount y from the difference between the target value Xt and the current measured value Xn of the optical output and the amount of change in the optical output value, as shown in, for example, equation (1).

[0020]   yn = a (Xt-Xn) + b (Xn-1-Xn) + yn-1 ... (1)

For example, at time 2, y2 = a (Xt-X2) + b (X1-X2) + y1 ... (2) and Xt> X2 and X1 <X2. Therefore, the right side of the equation (2) The first term has a positive value and the second
The term has a negative value. As shown in FIG. 4, time 1 to time 2
During this period, the amount of light output changes abruptly, and the change width (X
1-X2) is smaller than the difference (Xt-X2) between the measured value X2 and the target value Xt at time 2. In such a case, if the control amount is simply increased by the difference between Xt and X2, there is a high possibility that the target value will be greatly exceeded at the next time. Therefore, in such a case, on the contrary, it is necessary to reduce the control output to prevent overshoot.

The operation for this purpose is performed according to the magnitude relation between the first term and the second term. In other words, the first term has a role of simply bringing the controlled variable close to the target value, and the second term is the brake so as not to be over-controlled. Play the role of The light output of the discharge lamp 5 is controlled to be constant by performing a series of these operations at regular time intervals ts.

When the gas pressure inside the discharge lamp 5 is high as in the case of hot restart, the luminous efficiency is high, so a high light output can be obtained from the beginning of lighting, and the efficiency of the discharge lamp is Since it is difficult to estimate the light amount when a constant power is applied because it depends on the temperature and the like, it was difficult to always control the light amount to a constant light amount, but according to the present invention, the light output is directly detected. As a result, it is easy to quickly control the light amount to a constant amount regardless of the state of the discharge lamp. The above operation is repeated until the switch 9 is pressed again and an instruction to turn off is given (step 209). When the turning off is instructed, the frequency output S1 to the inverter is stopped (step 210) and turned off (step 211). .

Example 2. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a characteristic diagram showing the characteristics of human sensitivity and relative luminous efficiency with respect to the wavelength of light. In this embodiment, the spectral sensitivity characteristic of the photodetector 7 of the discharge lamp lighting device shown in FIG. 1 is close to that shown in FIG.
The operation in this case is shown below.

FIG. 6 shows the emission spectrum distribution of the light output from the discharge lamp 5 which has started discharge.
[A] shows an emission spectrum at cold start, and FIG. 6B shows an emission spectrum at hot restart. The discharge lamp is filled with a plurality of filling substances. This Figure 6
As shown in [A] and [B], since the luminescent substance differs depending on the internal state at the time of starting, light emission of a different spectrum occurs at the initial stage of starting. Due to this spectrum distribution, the emission color is bluish or reddish.

When the spectral sensitivity characteristic of the photodetector 7 is set to the relative luminous efficiency, this lighting device controls the light output of the discharge lamp to a specified light amount in the spectral range that is perceived by human eyes. First, the photodetector 7 detects the light in the spectral range that is perceived by human eyes among the lights emitted from the discharge lamp 5, and the control means 6 reads this as the light output value X1. Next, the target value Xt is compared and calculated, and the frequency output to the inverter 3 is determined.

In the present invention, since the sensitivity of the photodetector 7 is the relative visual sensitivity, light which is close to the sense of the human eye is input to the control means 6. Therefore, by performing the comparison calculation and determining the control amount, the characteristics such as the rising of light can be similar to the human sense. This rising characteristic is similar to that seen by human eyes even at the time of hot restart.

In the above embodiment, the drive frequency of the inverter circuit 3 was changed as a means for changing the electric power to the discharge lamp, but other means such as changing the primary side power supply voltage of the inverter circuit 3 may be used. Can also obtain the same effect.

[0029]

As described above, according to the present invention, the light which is the direct output amount of the discharge lamp is detected by the light detecting means,
As a result, the control means controls the electric power to the discharge lamp,
There is an effect that the light output can be surely controlled regardless of variations in characteristics of each discharge lamp.

Further, the electric power to the discharge lamp is controlled on the basis of the value detected by the photo-detecting means having the spectral sensitivity characteristic which is close to the relative luminous efficiency, and the light quantity corresponding to the human sense can be controlled. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the discharge lamp lighting device of the present invention.

FIG. 3 is an explanatory diagram showing discharge detection timing of the discharge lamp lighting device according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a change in light output when the discharge lamp in the embodiment of the present invention is turned on.

FIG. 5 is a characteristic diagram showing a relative luminous efficiency characteristic.

FIG. 6 is an emission spectrum distribution characteristic diagram of the discharge lamp in the example of the present invention.

FIG. 7 is a configuration diagram showing a configuration of a conventional discharge lamp lighting device.

FIG. 8 is a flowchart showing an operation of a conventional discharge lamp lighting device.

[Explanation of symbols]

1 DC power supply 2 power converter 3 inverter circuit 4 series resonance circuit 5 discharge lamp 6 Control means 7 Photodetector 8 Target value setting means 9 switch

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyasu             2-14-40 Ofuna, Kamakura-shi Mitsubishi Electric stock             Company Life Systems Research Center

Claims (2)

[Claims] 1. A discharge lamp, power supply means for supplying electric power to the discharge lamp, light detection means for detecting the amount of light emitted from the discharge lamp, and the power supply means based on the detected quantity of the light detection means. And a control means for controlling the supply power of the discharge lamp lighting device. 2. A discharge lamp lighting device, wherein the light detecting means is configured to have a spectral sensitivity characteristic close to a relative luminous efficiency.