JP2947303B2 - 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 control of the amount of light emitted from a discharge lamp.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram showing a conventional discharge lamp lighting device described in Japanese Patent Laid-Open No. H10-209,878. 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 of a predetermined frequency, and 4 is this inverter circuit. A series resonance circuit of a choke coil L connected to 3 and capacitors C1 and C2, and 5 is a discharge lamp.

Reference numeral 6 denotes control means for outputting 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 a voltage value Vc, and the resistor R connected in series to the discharge lamp 5 is connected to the discharge R flowing through the discharge lamp 5. This is for detecting a current as a voltage value VR.

FIG. 8 is a flowchart showing an operation process of the conventional discharge lamp lighting device shown in FIG. 7, and the operation will be described below with reference to FIG. When a light switch (not shown) for operating the 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). Thereby, the inverter circuit 3 becomes 100
kHz AC power, which is connected to the LC series resonance circuit 4
, A high voltage of about 10 kV is applied to both ends of the discharge lamp 5.

Next, the control means 6 comprises capacitors C1 and C2.
It is determined from the voltage value Vc at the connection point or the voltage value VR of the resistor R whether or not insulation breakdown has occurred in the discharge lamp 5 (step 802). The value of Vc indicates a high value when the filling gas of the discharge lamp 5 is in an insulated state, becomes 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 larger, it is possible to determine whether or not insulation breakdown has occurred by comparing the value of Vc or VR with a predetermined value Vs.

Next, when an insulation 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 kept constant, if the frequency is changed, the discharge current flowing through the discharge lamp changes. That is, when the frequency increases, the current decreases by the amount of L, and when the frequency decreases, the current increases. Therefore, the frequency of signal S1 is
If the frequency is set to kHz, the discharge current can be increased.

Next, it is determined whether 100 ms has elapsed (step 804). When 100 ms has elapsed, the signal S1 is output.
Is increased by 50 Hz (step 80).
5). Next, it is determined whether or not the frequency of the signal S1 has reached 6 kHz (step 806). Until the frequency reaches 6 kHz, steps 804 and 805 are repeated to increase the frequency by 50 Hz every 100 mS. When the frequency 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
Hz, it is fixed to that value (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 the characteristics such as the luminous efficiency differ for each discharge lamp due to the variation of discharge lamps and their aging, the rising characteristics of light vary for each discharge lamp. 2. Depending on the internal state of the discharge lamp, more power is supplied than necessary and the light output greatly overshoots. 3. Since the light-emitting phenomenon is indirectly detected by the voltage, there is a possibility that the light-emitting phenomenon is erroneously recognized, and stable starting of the discharge lamp cannot be realized. Such a problem has made it difficult to mount the device on a portion requiring high stability and high reliability, such as a headlight of a vehicle.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to reliably detect starting and to quickly control a specified amount of light irrespective of variations in discharge lamps, aging, or lamp states. It is an object of the present invention to obtain a discharge lamp lighting device capable of performing stable lighting control of a discharge lamp.

[0010]

A discharge lamp lighting device according to the present invention includes a discharge lamp, power supply means for supplying power to the discharge lamp, and light detection means for detecting the amount of light emitted from the discharge lamp. Reading means for reading the detected amount from the light detecting means at predetermined time intervals after the discharge lamp is turned on, a first difference between the previous detected amount and the present detected amount read by the reading means, and a light amount target value. And a control means including a calculating means for calculating a second difference between the detected amount and the current detection amount, and a power control means for controlling the power supplied to the discharge lamp based on the calculation result by the calculating means.

Further, the light detecting means is configured to have 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 detection means, and based on this, the power to the discharge lamp is controlled by the control means, and the light output Is reliably controlled.

Further, the power to the discharge lamp is controlled based on the value detected by the light detecting means having the spectral sensitivity characteristic close to the relative luminous efficiency, so that control close to human sense is performed.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Embodiment 1 FIG. In FIG. 1, reference numeral 1 denotes a DC power supply serving as an energy supply source, 2 denotes a power converter such as a DC-DC converter for boosting a DC voltage supplied from the DC power supply 1 to a predetermined voltage, and 3 denotes this power converter. An inverter circuit for converting the DC power obtained from 2 into AC power of a predetermined frequency;
Reference numeral 4 denotes a series resonance circuit including a choke coil L and a capacitor C, and these constitute a power supply unit. A discharge lamp 5 is connected to both ends of the capacitor C of the series resonance circuit 4.

Reference numeral 6 denotes a control means which is constituted by 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 denotes a target value setting unit for setting a target light output amount of the discharge lamp 5, and reference numeral 9 denotes a switch for instructing the control unit 6 to start and turn off the discharge lamp 5.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG. Hereinafter, the operation will be described with reference to FIG. When the switch 9 connected to the control means 6 is closed and the lighting of the discharge lamp 5 is commanded (step 201), the control means 6
Outputs the frequency output S1 corresponding to the resonance frequency fo determined by the circuit constant LC of the series resonance circuit 4 to 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 at both ends of the capacitor C of the series resonance circuit 4 by a resonance phenomenon. When this high voltage is applied to the discharge lamp 5, the discharge lamp 5 causes breakdown and starts discharging, 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 a light output exceeding 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 power for lighting. The frequency output S1 which is lower than fo to be applied to the lamp 5, for example, fs determined by 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 light output when the discharge lamp is turned on. According to the flowcharts of FIGS. 4 and 2, the amount of light output from the discharge lamp 5 which has started discharging is quickly controlled to a specified amount. How to do it. First, the control means 6 reads the light output value X1 of the discharge lamp 5 by the photodetector 7 (step 205), and compares this 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 the output is performed at that frequency (step 2).
08). As a method of the comparison operation, for example, as shown in Expression (1), the control amount y is determined from the difference between the target value Xt and the current measured value Xn of the light output and the amount of change in the light output value.

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) Since Xt> X2 and X1 <X2, the right side of equation (2) The first term is a positive value and the second
The term has a negative value. As shown in FIG. 4, from time 1 to time 2
During the period, the light output amount changes rapidly, and the change width (X
1−X2) is smaller than the difference (Xt−X2) between the measured value X2 at time 2 and the target value Xt. 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, it is necessary to reduce the control output to prevent overshoot.

The operation for this 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 approaching the control amount to the target value, and the second term is a brake so as not to over-control. Take the role of applying. By performing these series of operations every specified time ts, the light output of the discharge lamp 5 is controlled to be constant.

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

Embodiment 2 FIG. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a characteristic diagram showing 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 configured to be close to the sensitivity characteristic shown in FIG.
The operation in this case will be described below.

FIG. 6 shows an emission spectrum distribution of light output from the discharge lamp 5 which has started discharging.
FIG. 6A shows an emission spectrum at the time of a cold start, and FIG. 6B shows an emission spectrum at the time of a hot restart. Note that a plurality of sealing substances are sealed in this discharge lamp. This figure 6
As shown in [A] and [B], the luminescent material differs depending on the internal state at the time of starting, so that light emission having a different spectrum occurs at the initial stage of starting. The emission color becomes bluish or reddish due to this spectral distribution.

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

In the present invention, since the sensitivity of the photodetector 7 is relative luminous efficiency, light close to the sensation seen by human eyes is input to the control means 6. Therefore, by performing the comparison operation and determining the control amount, characteristics such as light emission can be obtained that are close to human senses. As for the rising characteristic, a characteristic similar to the sensation seen by human eyes can be obtained even at the time of hot restart.

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

[0029]

As described above, according to the present invention, a discharge lamp lighting device includes a discharge lamp, power supply means for supplying power to the discharge lamp, and light detection means for detecting the amount of light emitted from the discharge lamp. Reading means for reading the detected amount from the light detecting means at predetermined time intervals after the discharge lamp is turned on; a first difference and a light amount between the previous detected amount and the present detected amount read by the reading means. A control unit includes a calculating unit that calculates a second difference between the target value and the current detection amount, and a power control unit that controls power supplied to the discharge lamp based on a calculation result by the calculating unit. Therefore, the amount of light from the discharge lamp quickly reaches a predetermined light amount without largely overshooting after reaching the target value without being limited by the individual variation and aging of the discharge lamp and the internal state of the discharge lamp. With Obtain the effect of that.

Further, the light detecting means is constituted by one having a spectral sensitivity characteristic close to the relative luminous efficiency.
An effect is obtained that light start-up control corresponding to human senses can be realized.

[Brief description of the 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 a 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 is turned on in the embodiment of the present invention.

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

FIG. 6 is an emission spectrum distribution characteristic diagram of the discharge lamp in the embodiment 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 the operation of the conventional discharge lamp lighting device.

[Explanation of symbols]

 DESCRIPTION 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

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyasu Private Market 2--14-40 Ofuna, Kamakura City Mitsubishi Electric Corporation Living System Laboratory (56) References JP-A-3-43992 (JP, A) JP-A-57-208098 (JP, A) JP-A-3-257794 (JP, A) JP-A-4-190595 (JP, A) JP-A-62-141695 (JP, U) JP-A-3-118595 (JP JP, U) Japanese Utility Model 4-54199 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/14-41/29 H02M 7/537

Claims (2)

(57) [Claims] 1. A discharge lamp, power supply means for supplying electric power to the discharge lamp, and light detection means for detecting a light emission amount of the discharge lamp
And detecting the light after the start of lighting of the discharge lamp.
Reading for reading the detection amount from the means at predetermined time intervals
Detection means and the previous detection amount read by this reading means
Difference between the current and the detected amounts and the light amount target value and the current
Calculating means for calculating a second difference from the detected amount;
Power supplied to the discharge lamp based on the calculation result by the means
A discharge lamp lighting device , comprising: a control unit including a power control unit for controlling the discharge lamp. 2. The discharge lamp lighting device according to claim 1 , wherein said light detecting means has a spectral sensitivity characteristic close to relative luminous efficiency.