JP4794921B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp such as a metal halide lamp used as a headlight of a vehicle such as an automobile, and a discharge lamp used as an illumination lamp or a street lamp in an indoor or outdoor facility or factory. The present invention relates to a discharge lamp lighting device that controls lighting of a less (non-enclosed) discharge lamp.

In a discharge lamp lighting device for a vehicle such as an automobile, in order to control the lighting of the discharge lamp, the primary side current is controlled on the primary side of the transformer that boosts the vehicle battery voltage to a voltage suitable for the discharge lamp (bulb). A switching element is provided, and this switching element is controlled by a PWM (pulse width modulation) signal from the control unit to control the power supplied to the discharge lamp. This PWM signal varies the bulb voltage in accordance with predetermined control characteristics that predetermine the relationship between the supply power to the discharge lamp and the bulb voltage applied to the discharge lamp, and the supply power to the discharge lamp is determined by this variable bulb voltage. To do.
Mercury is enclosed in discharge lamps used in previous vehicle headlamps, and mercury-less discharge lamps have been desired due to environmental pollution problems when discarding discharge lamps.
In the case of a mercury-less discharge lamp, since there is no mercury, xenon emission is dominant until the temperature in the tube rises, and the rise of the luminous flux is delayed as compared with the previous discharge lamp in which mercury is enclosed. In order to shorten the rise time, it is necessary to supply higher power than the rated value at the start of lighting. However, since the luminous efficiency increases rapidly at a certain point in time, the same control as that for the conventional mercury-enclosed discharge lamp is stable. There was a problem that the luminous flux did not rise.
Further, the bulb voltage and bulb voltage-time characteristics vary due to individual differences in the discharge lamp, such as the composition of the metal halide in the discharge lamp tube and the electrode shape. Here, compared to conventional mercury-enclosed discharge lamps, mercury-less discharge lamps have the same minimum voltage between the discharge lamp electrodes, but the stable voltage is about half that of the supply voltage to the discharge lamp. In the control characteristics that define the relationship between the bulb voltage and the bulb voltage, the ratio of the change in the power supplied to the discharge lamp with respect to the change in the bulb voltage is large. There has also been a problem that the variation is larger than that of a conventional mercury-enclosed discharge lamp. Furthermore, since the changing point at which the luminous efficiency rapidly increases also varies depending on individual differences in the discharge lamp, means for detecting the luminous efficiency changing point is required.
As a conventional discharge lamp lighting device for the mercury-less discharge lamp, for example, there are the following.

  As a prior art example 1, this discharge lamp lighting device can absorb variations in lamp voltage due to individual differences in the discharge lamp in a mercury-less discharge lamp (lamp), suppress overshoot and undershoot of the light flux, and smooth the light flux. The initial lighting voltage storage circuit for storing the lamp voltage or the corresponding signal voltage immediately after starting the lamp lighting, and the lamp voltage immediately after starting the lamp lighting from the lamp voltage or the equivalent signal voltage, And a ΔVL detection circuit that subtracts the corresponding signal voltage to obtain a lamp voltage change value ΔVL, and controls the lamp applied power based on the lamp voltage change value ΔVL (see, for example, Patent Document 1).

  As a prior art example 2, this discharge lamp lighting device aims to output stable light even if the luminous efficiency increases after the start of a mercury-less high-intensity discharge lamp (lamp). A DC power source, a power converter connected to the DC power source, changing the DC power, converting the DC power back to AC power, or changing the DC power and then converting back to AC power; A mercury-less high-intensity discharge lamp connected via an igniter that generates a high-voltage pulse in the unit, and the power converter is driven so that appropriate power is supplied to the mercury-less high-intensity discharge lamp A control unit for the discharge lamp lighting device, the control unit has a luminous efficiency increase detection means for detecting an increase in the luminous efficiency of the mercury-less high-intensity discharge lamp, the luminous efficiency increase detection means Check for increased luminous efficiency When, in which to output a signal for reducing the power supplied to the high-intensity discharge lamp mercury-less to the power conversion unit (e.g., see Patent Document 2).

JP 2003-338390 A JP 2004-119164 A

  The conventional discharge lamp lighting device is configured as described above, and the conventional example 1 absorbs variations in lamp voltage due to individual differences in the discharge lamp in a mercury-less discharge lamp, and makes it possible to smoothly converge the luminous flux to 100%. In the second conventional example, even if the luminous efficiency increases after starting the mercury-less high-intensity discharge lamp, stable light can be output.

  On the other hand, in the bulb voltage-time characteristics of mercury-less discharge lamps, conventional lamps have a so-called bathtub curve, whereas mercury-less discharge lamps in recent years have a tendency to increase those that do not draw a bathtub curve. In the conventional examples 1 and 2 described above, the bulb characteristics are different, so that there is a problem that the light emission efficiency change point cannot be detected with high accuracy.

  The present invention has been made to solve the above-mentioned problems, and obtains a discharge lamp lighting device that detects a luminous efficiency change point and starts a discharge lamp, particularly a mercury-less discharge lamp, quickly and stably. For the purpose.

A discharge lamp lighting device according to the present invention is connected to a DC power supply , converts a power supply voltage of the DC power supply into a DC voltage of a predetermined value, converts DC power by the DC voltage into AC power, and based on the AC Stores the power converter that supplies power to the discharge lamp that is started by the high-pressure pulse generated at the time, the stable valve voltage at the time of stable lighting measured at the time of previous lighting, and the stable valve equivalent impedance calculated from the stable valve current And a value calculated by a preset formula based on the stored previous stable valve equivalent impedance stored as the luminous efficiency change point target value, and detects the current valve voltage and valve current, Based on the current bulb voltage and bulb current, it is judged whether the set luminous efficiency change point target value has been achieved, and this luminous efficiency change Until the achievement of the target value is established, the maximum power is supplied to the discharge lamp, and after the achievement of the luminous efficiency change point target value is established, the power conversion unit reduces the supply power to the discharge lamp. And a control unit that controls power supply .

According to the present invention, the high-voltage generated based on the alternating current is connected to the direct-current power source, and after the power source voltage of the direct-current power source is converted into a direct-current voltage of a predetermined value, the direct-current power by the direct-current voltage is converted into alternating-current power. A power converter for supplying power to a discharge lamp started by a pulse, a storage device for storing a stable valve voltage at the time of stable lighting measured at the time of previous lighting, and a stable valve equivalent impedance calculated from a stable valve current; The value calculated by a preset formula based on the stored previous stable valve equivalent impedance is set as the light emission efficiency change point target value, and the current valve voltage and valve current are detected, and the current valve is detected. Based on the voltage and bulb current, it is judged whether the set luminous efficiency change point target value has been achieved, and the luminous efficiency change point target value is achieved. The maximum power is supplied to the discharge lamp until it is established, and after the achievement of the luminous efficiency change point target value is established, the power supply by the power conversion unit is controlled so as to reduce the supply power to the discharge lamp. since it is configured to so that a control unit, the actual luminous efficiency change point target value in accordance with the discharge lamp to be mounted is set, thereby, the discharge lamp, in particular a valve voltage due to individual differences of the mercury-free discharge lamp - Can absorb variations in characteristics such as time and light emission efficiency change point, and appropriate power is supplied according to bulb voltage, etc., suppresses overshoot and undershoot of the light beam, and converges the light beam to 100% quickly and stably Can be activated.

An embodiment of the present invention will be described below.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing the overall configuration of a discharge lamp lighting device according to the present invention including the configuration of the discharge lamp lighting device according to the first embodiment.
In FIG. 1, this discharge lamp lighting device is roughly composed of a DC power source 1, a lighting switch 2, a power conversion unit 3 and a control unit 4.

In the above configuration, the DC power source 1 is, for example, a battery mounted on a vehicle.
The lighting switch 2 turns on / off the power supply by the DC power source 1.
The power conversion unit 3 is connected to a DC power source 1 such as a battery via the lighting switch 2, converts the power voltage of the DC power source 1 into a DC voltage of a predetermined value, and then converts the DC power by the DC voltage into AC power. Electric power is supplied to the discharge lamp 5 started with a high-pressure pulse generated based on this alternating current, and a direct current (DC) / direct current (DC) converter 31, a takeover circuit 32, a current detection resistor 33, an H bridge. The circuit 34, the H bridge driver circuit 35, and an igniter 36 are included.
In the configuration of the power converter 3, the DC / DC converter 31 rectifies and smoothes the flyback transformer 311 as a step-up transformer and the AC power generated on the secondary winding side of the flyback transformer 311 into a direct current. Power for controlling a current flowing in the primary winding of the flyback transformer 311 by performing a switching operation in accordance with a rectifier diode 312 and a smoothing capacitor 313 and a PWM (pulse width modulation) signal (control signal) from the control unit 4 described later. MOSFET (metal oxide film semiconductor field effect transistor) 314 is provided, and the DC power is supplied by boosting the voltage 12V of the DC power supply 1 (battery) to a required voltage (for example, 400V).

The takeover circuit 32 includes a series resistor 321 for charging / discharging and a capacitor 322, and supplies sufficient electric energy when the discharge lamp 5 shifts from glow discharge to arc discharge.
The current detection resistor (shunt resistor) 33 converts the current flowing through the resistor into a voltage.
The H bridge circuit 34 includes a first FET (field effect transistor) 341 and a second FET 342 disposed on the positive output side of the DC / DC converter 31, and a third FET 343 disposed on the negative output side of the converter 31. And the fourth FET 344, and in the AC drive, the first FET 341 and the fourth FET 344 are turned on and the second FET 342 and the third FET 343 are turned off, and the second FET 342 and the third FET 343 Is switched on, and the path 2 through which the first FET 341 and the fourth FET 344 are turned off is alternately switched, the DC output of the DC / DC converter 31 is converted into rectangular-wave AC driving, and AC power is supplied to the discharge lamp 5. Supply.

The H bridge driver circuit 35 performs control so that the path 1 and the path 2 in the H bridge circuit 34 are switched alternately. This switching control is performed under the control of the control unit 4 described later.
When the discharge lamp 5 is started, the igniter 36 generates a high voltage pulse based on the rectangular wave alternating current from the H bridge circuit 34 and applies the high voltage pulse between the electrodes of the discharge lamp 5 to cause breakdown. A glow discharge is generated between the electrodes.
The control unit 4 includes a valve current detection circuit 41, a valve voltage detection circuit 42, a PWM control circuit 43, a memory circuit 44, a timer circuit 45, and a control circuit 46, and controls the DC / DC converter 31 and the H bridge driver circuit 35. To do.
In the configuration of the control unit 4, the valve current detection circuit 41 detects a current converted into a voltage in the current detection resistor 33 of the power conversion unit 3 as a valve current.

The bulb voltage detection circuit 42 detects the voltage supplied to the discharge lamp 5.
The PWM control circuit 43 turns on / off the power MOSFET 314 of the power converter 3 by a PWM signal.
The memory circuit 44 stores a stable bulb voltage or a bulb equivalent impedance described later when the discharge lamp 5 is stably lit.
The timer circuit 45 detects the elapsed lighting time of the discharge lamp 5.
The control circuit 46 controls the H bridge driver circuit 35 and the PWM control circuit 43 based on signals from the valve current detection circuit 41, the valve voltage detection circuit 42 or the timer circuit 45. The control circuit 46 is constituted by a microcomputer (microcomputer), for example.

Next, the basic operation of FIG. 1 will be described.
When the lighting switch 2 is turned on, power is supplied to each part shown in FIG. 1, the PWM control circuit 43 is driven by a signal from the control circuit 46, the power MOSFET 314 is turned on / off by the PWM signal, and the flyback transformer 311 is driven, The output generated on the secondary winding side of the flyback transformer 311 is rectified by the rectifier diode 312, and the smoothing capacitor 313 boosts the voltage of the DC power source 1 (for example, 12V) and smooths it as the output voltage (for example, 400V). Generated.
The H bridge driver circuit 35 is driven by a signal from the control circuit 46, and the first FET 341 to the fourth FET 344 constituting the H bridge circuit 34 are alternately turned on and off in a diagonal relationship. As a result, the high voltage output from the DC / DC converter 31 is supplied to the igniter 36 via the H bridge circuit 34. When the igniter 36 generates a high voltage pulse, the electrodes of the discharge lamp 5 are broken down. ,Light.

When the discharge lamp 5 starts glow discharge, the discharge lamp 5 changes from glow discharge to arc discharge due to the discharge current from the smoothing capacitor 313 and the discharge current from the capacitor 322 via the charge / discharge series resistor 321 of the takeover circuit 32. Migrate to
By alternately switching the polarity of the output voltage to the discharge lamp 5 by the H bridge circuit 34, the discharge lamp 5 is turned on by alternating current.
The valve current detection circuit 41 and the valve voltage detection circuit 42 for detecting the voltage converted by the output current flowing through the current detection resistor 33 input a valve current or an equivalent signal of the valve voltage to the control circuit 46, and the control circuit 46 In order to determine the state of the discharge lamp 5 from the corresponding signal and supply appropriate power to the discharge lamp 5, the signal to the PWM control circuit 43 is changed to control the supplied power.
When the control circuit 46 determines stable lighting based on the corresponding signal or the elapsed lighting time of the discharge lamp 5 detected by the timer circuit 45, the control circuit 46 stores the valve voltage at that time in the memory circuit 44 as the stable valve voltage V2. To do.

Next, the operation at the beginning of lighting of the discharge lamp 5 will be described.
The valve voltage, which is one of the parameters for power control, uses a value calculated by the control circuit 46 based on the signal detected by the valve voltage detection circuit 42.
The control circuit 46 detects the current valve voltage by the valve voltage detection circuit 42 when the lighting elapsed time detected by the timer circuit 45 exceeds a predetermined time, and stores it in the memory circuit 44 at the time of stable lighting. Compared to the voltage V2, if the predetermined ratio β has not been reached, the extinction time from the previous time is long, and it is determined that the cold start from a state in which the tube temperature is low. It is determined as a hot start from a state where the turn-off time is short and the temperature inside the tube is high.

Next, the configuration according to the first embodiment will be described for specific power control until the cold start or the lighting elapsed time exceeds a predetermined time.
FIG. 2 is a diagram showing a bulb voltage-time characteristic and a light emission efficiency change point target value for explaining the light emission efficiency change point target value in the first embodiment of the present invention.
In the first embodiment, the control circuit 46 in FIG. 1 (entire configuration) will be described as the control circuit 46 (1), and the light emission efficiency change point target value will be described as the light emission efficiency change point target value (1).
In FIG. 2, paying attention to the fact that the luminous efficiency and the bulb voltage rapidly increase when the metal halide in the tube of the discharge lamp 5 starts to evaporate, the stable bulb voltage V2 when the discharge lamp 5 is stably lit and the minimum bulb voltage V1 immediately after lighting. Since the bulb voltage slope at the light emission efficiency change point changes in proportion to the difference between the difference (V2−V1), the ratio α1 of the difference (V2−V1) and the bulb voltage slope at the light emission efficiency change point is previously determined by an experimental statistical method or the like. As shown in FIG. 2, the control circuit 46 (1) performs calculation according to the calculation formula “α1 × (V2−V1)” obtained by multiplying the difference (V2−V1) by the ratio α1 as shown in FIG. The value obtained by this calculation is set as the luminous efficiency change point target value (1).

Here, the stable valve voltage V2 and the minimum valve voltage V1 are detected by the valve voltage detection circuit 42 and calculated by the control circuit 46 (1) as described above. The stable valve voltage V2 is a memory circuit. 44. Further, the minimum valve voltage V1 is the minimum value of the characteristic that continuously changes among the sequentially detected valve voltages. This prevents erroneous determination due to instantaneous fluctuation noise or the like.
Further, the control circuit 46 (1) detects a bulb voltage gradient that is a gradient of the current bulb voltage of the discharge lamp 5 with respect to time based on a detection signal from the bulb voltage detection circuit 42.
The control circuit 46 (1) supplies maximum power to the discharge lamp 5 when the detected current bulb voltage slope is lower than the luminous efficiency change point target value (1), and the current bulb voltage slope is the luminous efficiency. After the change point target value (1) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power converter 3 is controlled. .
Thereby, the variation in the luminous efficiency change point due to individual bulb differences can be absorbed, and the luminous flux can be quickly converged to 100%. Further, it is practical only with the bulb voltage detection circuit 42, and the luminous efficiency change point target value (1) is effectively set for a discharge lamp having a positive bulb voltage slope even before the luminous efficiency change point. It is possible to accurately detect the luminous efficiency change point.

Next, control of power supply reduction in the power supply control will be described with reference to FIG.
FIG. 3 is a control characteristic diagram defining the relationship between the bulb voltage and the power supplied to the bulb (discharge lamp 5).
As described above, when the bulb voltage slope exceeds the luminous efficiency change point target value (1) while the discharge lamp 5 is lit, the reduction of the supply power to the discharge lamp 5 is started. 3 is controlled according to the control characteristics of No. 3.
In FIG. 3, the control circuit 46 (1) performs PWM so as to supply the maximum power W1 to the discharge lamp 5 up to the bulb voltage Va (voltage at the light emission efficiency change point target value (1)) at the time of detecting the light emission efficiency change point. The power MOSFET 314 is controlled via the control circuit 43. The power supply to the discharge lamp 5 after the valve voltage Va is exceeded, that is, after the target value (1) is exceeded, is the approximate broken line illustrated in FIG. Reduce according to characteristics.

  As can be understood from this approximate broken line, control is performed so that the bulb voltage during lighting changes steeply when it is close to the target value (1), and gradually changes as it approaches the bulb voltage during stable lighting. Here, the valve voltage Vb makes a transition from “steep change” to “gradual change”, and between the valve voltage Va and the valve voltage Vb changes steeply from the maximum power W1 to the time control start power W2. Between voltage Vb and valve voltage Vc, it gradually changes from time control start power W2 to stable power W3. The valve voltage Vb in the above is a “time control shift target value (= β × V2)” obtained by adding a preset value (predetermined value) β to the stable valve voltage V2, and the valve voltage Vc is the stable valve voltage V2. A “stable power target value” obtained by integrating a preset value (predetermined value) γ, and the power W2 is the starting power when shifting to time control. The “time control shift target value (= β × V2)” and the time control start power W2 will be described later (FIGS. 5 and 6).

In FIG. 3 described above, the power reduction characteristic is an approximate polygonal line characteristic, but it may be a curved line that draws an arc downward.
As described above, after detecting the luminous efficiency change point, the relationship between the electric power supplied to the discharge lamp 5 and the bulb voltage is set to an approximate polygonal line as shown in FIG. In the section where the valve voltage is low but suddenly rises, the power drops sharply, and in the section where the valve voltage rises and the valve voltage changes slowly, the power gradually falls. The amount of light emission can be made constant even during attenuation control.

Next, the control of power supply reduction taking into account the characteristic variation due to the individual difference of the discharge lamp 5 with respect to the control of power supply reduction described with reference to FIG. 3 will be described with reference to FIG.
FIG. 4 is a control characteristic diagram defining the relationship between the bulb voltage and the power supplied to the bulb (discharge lamp 5) in consideration of the characteristic variation due to individual differences of the discharge lamp 5.
FIG. 3 is premised on the discharge lamp 5 having a fixed characteristic assumed in advance, and the valve voltage Va and the stable valve voltage V2 which is a calculation reference for the valve voltage Vb and the valve voltage Vc are fixed in advance. It is a value.
However, the discharge lamp 5 has characteristic variations due to individual differences, and the bulb voltage Va and the stable bulb voltage V2 are not necessarily constant values. For this reason, the control based on the uniform characteristics as shown in FIG.

Therefore, control in consideration of characteristic variations due to individual differences among the discharge lamps 5 is desired.
In view of this, the control characteristic of the curved line or the approximate broken line that draws a downward arc is changed in proportion to the difference between the stable bulb voltage V2 when the discharge lamp 5 is stably lit and the minimum bulb voltage V1 immediately after lighting.
FIG. 4 shows that the bulb voltage Va, Vb, Vc is detected or calculated by the control circuit 46 (1) for each discharge lamp 5 to be used, and the control characteristic of the approximate broken line is determined. The control characteristic Ca in the figure shows the characteristic of FIG. 3, and the control characteristic Cb shows a case where the bulb voltage Va and the stable bulb voltage V2 are each a discharge lamp having a larger value than the discharge lamp showing the control characteristic Ca.
Thereby, the characteristic variation by the individual difference of the discharge lamp 5 is absorbed, and the light emission amount can be made constant even during power attenuation control.

Next, a power supply control mode will be described.
FIG. 5 is a flowchart showing processing of power supply control by the control circuit 46 (1).
As shown in FIG. 3, the control of power supply to the discharge lamp 5 is basically performed based on the bulb voltage. For some reason, for example, the elapsed lighting time of the discharge lamp 5 is predetermined. If the bulb voltage does not increase even after a lapse of time and excessive power supply continues to the discharge lamp 5, the control mode based on the bulb voltage is changed to the control mode based on the time. Therefore, it is necessary to prevent the power from being excessively supplied as described above.
Hereinafter, the power supply control process by the control circuit 46 (1) will be described.
In FIG. 5, in step ST1, the control circuit 46 (1) acquires the data of the lighting elapsed time from the timer circuit 45, determines whether this lighting elapsed time has passed a preset (predetermined time) Ta, If the time Ta has elapsed (step ST1-YES), the process proceeds to step ST2, and if the predetermined time Ta has not elapsed (step ST1-NO), the process proceeds to step ST4.

In step ST2, the control circuit 46 (1) determines whether the valve voltage has reached a preset time control shift target value based on the detection signal from the valve voltage detection circuit 42, and reaches this time control shift target value. If not (step ST2-NO), the process proceeds to step ST3. If the time control shift target value is reached (step ST2-YES), the process proceeds to step ST5.
Here, the time control shift target value means “valve voltage Vb = stable valve voltage V2 × predetermined value β” described in FIG. Further, the time control shift target value Vb is set to a value equal to or higher than the bulb voltage Va when the luminous efficiency change point is detected, as shown in FIG.
In step ST3, the control circuit 46 (1) again obtains the lighting elapsed time data from the timer circuit 45, determines whether this lighting elapsed time has passed a preset (predetermined time) Tb, and the predetermined time Tb. If not (step ST3-NO), the process proceeds to step ST4. If the predetermined time Tb has elapsed (step ST3-YES), the process proceeds to step ST5.

In step ST4, the control circuit 46 (1) controls the power supply to the discharge lamp 5 in a control form based on the control characteristics based on the bulb voltage shown in FIG. 3 or FIG. Since the bulb voltage does not rise within the predetermined time Ta or within the predetermined time Tb, and thus the power is not continuously supplied to the discharge lamp 5 excessively, the control mode based on the valve voltage, which is a basic control mode. Is what you do.
In step ST5, when the valve voltage reaches the time control shift target value or when the predetermined time Tb has elapsed, the control circuit 46 (1) is based on the control characteristics based on the valve voltage shown in FIG. 3 or FIG. The control mode shifts to a control mode based on control characteristics based on the time (lighting elapsed time) shown in FIG.
FIG. 6 is a control characteristic diagram defining the relationship between the elapsed lighting time and the power supplied to the bulb (discharge lamp 5).
As shown in FIG. 6, the control based on the lighting elapsed time is controlled so that the power is reduced from the time control start power W2 to the stable power W3 with the lighting elapsed time (s).

  As described above, when the lighting elapsed time has passed the predetermined time (step ST3-YES), by switching from the control mode based on the valve voltage to the control mode based on the time, for example, the valve voltage or the like. Because, for example, when a discharge lamp having a completely different characteristic from that currently on the market is mounted, the power is forcibly reduced even if the bulb voltage does not rise to the target value. It is possible to prevent excessive supply of power to the discharge lamp 5.

Further, the supply power is determined according to the control characteristics of FIG. 3 or FIG. 4 until the valve voltage reaches the time control shift target value, and after the valve voltage reaches the time control shift target value (step ST2-YES), FIG. Since the supply power is determined according to the control characteristics, the supply power is controlled by the valve voltage in the section where the change in the valve voltage is large, and the control is performed by the lighting elapsed time in the section where the change in the valve voltage is small. In particular, the light emission amount can be made constant.
Further, since the time control shift target value (step ST2) is obtained by adding the predetermined value β to the stable bulb voltage V2, the variation in the bulb voltage-time characteristics between individual differences of the discharge lamp 5 is absorbed. Transition to time control is performed, and electric power suitable for the discharge lamp 5 can be supplied in accordance with the control characteristics of FIG.
Further, when the discharge lamp 5 is determined to be hot start, the control circuit 46 (1) reduces the power from the supply power at the time of determination among the control characteristics of FIG. 6 and supplies the power suitable for the state of the discharge lamp 5. As a result, the rise of the luminous flux quickly converges to 100%.

  As described above, according to the first embodiment, the difference (V2−V1) between the stable bulb voltage V2 when the discharge lamp 5 is steadily lit and the minimum bulb voltage V1 immediately after the lit is determined statistically by experiments. The value obtained by the multiplication by the bulb voltage slope ratio α1 is set as the luminous efficiency change point target value (1), and the control circuit 46 (1) sets the current bulb voltage slope to the luminous efficiency change point target value. When it is lower than (1), the maximum power is supplied to the discharge lamp 5, and when the current bulb voltage slope exceeds the target value (1), the power conversion unit 3 starts to reduce the power supplied to the discharge lamp 5. Therefore, the luminous efficiency change point target value (1) is set according to the discharge lamp 5 that is actually mounted, and thus, the bulb voltage due to the individual difference of the discharge lamp, particularly the mercury-less discharge lamp, is set. Characteristics such as time and luminous efficacy To absorb variations of the change point, it is supplied proper power according to the valve voltage is suppressed overshoot or undershoot of the luminous flux, and converges the light flux immediately 100% can be activated stably.

In addition, the above configuration provides an effect of appropriately controlling power for a mercury-less discharge lamp having recent characteristics.
Hereinafter, the above effect will be described with reference to FIG.
FIG. 7 is a graph showing bulb voltage-time characteristics for explaining a conventional mercury-less discharge lamp.
As shown in FIG. 7, the conventional mercury-less discharge lamp has a characteristic of drawing a so-called “bathtub curve” in which the bulb voltage is substantially constant until the luminous efficiency change point. For this reason, it is possible to detect a light emission efficiency change point at which the bulb voltage rises, for example, using a differentiation circuit, and to control power based on the detected light emission efficiency change point.
However, recent mercury-less discharge lamps, as shown in FIG. 2, have increased in characteristics that do not draw bathtub curves as shown in FIG. For mercury-less discharge lamps with such characteristics, when the emission efficiency change point is detected by the above-described differentiation circuit, the power is reduced before the true emission efficiency change point, and the supply power to the discharge lamp is insufficient. However, there arises a problem that the light flux is undershooted.
On the other hand, a luminous efficiency change point target value (1) serving as a reference point for power control is appropriately set by the configuration of the first embodiment, and the mercury-less discharge lamp having the characteristics shown in FIG. On the other hand, the power can be appropriately controlled.

Further, the setting of the luminous efficiency change point target value (1) in the first embodiment can be practically performed only by the bulb voltage detection circuit 42 without detecting the bulb current, and even before the luminous efficiency change point, the bulb voltage can be set. A target value can be effectively set for a discharge lamp having a positive slope, and the luminous efficiency change point can be detected more accurately.
Further, after exceeding the target value (1) of the luminous efficiency change point, the relationship between the electric power supplied to the discharge lamp 5 and the bulb voltage is set to an approximate polygonal line as shown in FIG. Because the power is sharply decreased for the section where the valve voltage of the valve rises sharply, and the power is gradually decreased for the section where the change in the valve voltage is slow, the light emission amount is made constant even during power attenuation control. be able to.
Further, by changing the control characteristic of the approximate polygonal line or the curve that draws a downward arc in proportion to the difference between the stable bulb voltage V2 and the minimum bulb voltage V1 of the discharge lamp 5, as shown in FIG. The characteristic variation due to the individual difference of 5 is absorbed, and the light emission amount can be made constant even during power attenuation control.

In addition, when the lighting elapsed time has passed a predetermined time, the mode shifts from the form of power control with the bulb voltage to the form of power control with time. For example, a discharge lamp 5 whose characteristics are completely different from those currently on the market is mounted. In such a case, the power is forcibly reduced even when the bulb voltage does not rise to the target value, so that it is possible to prevent excessive supply of power to the discharge lamp 5.
Further, the control characteristic of FIG. 3 or FIG. 4 is followed until the time control shift target value is reached, and after the valve voltage reaches the time control shift target value, the control characteristic of FIG. 6 is followed. By controlling the power with the bulb voltage and controlling the power with the elapsed lighting time in a section where the change in the bulb voltage is small, the light emission amount can be made constant even during the power decay. Further, since the target value for time control shift is obtained by adding the predetermined value β to the stable bulb voltage V2, the variation to the bulb voltage-time characteristics between individual differences of the discharge lamp 5 is absorbed. Transition is performed and electric power suitable for the discharge lamp 5 can be supplied.

Embodiment 2. FIG.
FIG. 8 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the second embodiment of the present invention.
In the second embodiment, the control circuit 46 in FIG. 1 (overall configuration) will be described as the control circuit 46 (2), and the light emission efficiency change point target value will be described as the light emission efficiency change point target value (2).
The light emission efficiency change point target value (2) in Embodiment 2 is the light emission efficiency change point due to the fact that the bulb equivalent impedance characteristic of FIG. 8 has a larger slope change at the light emission efficiency change point than the valve voltage characteristic of FIG. This is because it is easy to detect. This point of interest is not limited to the second embodiment, and the same applies to the valve equivalent impedance characteristics of the third and later embodiments described later.

  Further, the luminous efficiency change point target value (2) in the second embodiment pays attention to the fact that the luminous efficiency and the bulb equivalent impedance rapidly increase when the metal halide in the tube of the discharge lamp 5 starts to evaporate. Since the difference (Z2−Z1) between the stable valve equivalent impedance Z2 at the time of stable lighting 5 and the minimum valve equivalent impedance Z1 immediately after lighting is correlated with the increase in valve equivalent impedance due to evaporation of the metal halide, the metal halide starts to evaporate. The ratio α2 between the bulb equivalent impedance increase at the luminous efficiency change point and the difference (Z2−Z1) is set by measuring in advance by a statistical method or the like by an experiment, and the control circuit 46 (2) is as shown in FIG. Is calculated by adding the minimum valve equivalent impedance Z1 to the value obtained by multiplying the difference (Z2−Z1) by the ratio α2 Performs calculation by × (Z2-Z1) + Z1 ", sets the value obtained by this calculation as luminous efficiency change point target value (2).

Here, the valve equivalent impedances Z1 and Z2, which are parameters of power control, or the current valve equivalent impedance and the like are based on a signal detected by the valve current detection circuit 41 and a signal detected by the valve voltage detection circuit 42. The value calculated by 46 (2) is used. Further, the minimum valve equivalent impedance Z1 is the minimum value of the characteristic that has continuously changed in the sequentially detected valve equivalent impedance. This prevents erroneous determination due to instantaneous fluctuation noise or the like.
Similarly to the bulb voltage in the first embodiment, when the control circuit 46 (2) determines that the stable lighting is performed based on the elapsed lighting time of the discharge lamp 5 detected by the timer circuit 45, the control circuit 46 (2) Is stored in the memory circuit 44 as a stable valve equivalent impedance Z2.
Similarly to the first embodiment, when the elapsed lighting time detected by the timer circuit 45 has passed a predetermined time, the current valve equivalent impedance is detected and stored in the memory circuit 44 when the stable valve equivalent during stable lighting is obtained. Compared to the impedance Z2, if the predetermined ratio β has not been reached, the extinction time from the previous time is long, and it is determined that the cold start from a state in which the tube temperature is low. It is determined as a hot start from a state where the turn-off time is short and the temperature inside the tube is high.

The control circuit 46 (2) supplies the maximum electric power to the discharge lamp 5 when the current bulb equivalent impedance of the discharge lamp 5 is lower than the target value (2) of the luminous efficiency change point, and the current bulb equivalent impedance is the luminous efficiency. After the change point target value (2) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power converter 3 is controlled. .
As a result, it is possible to absorb the variation at the light emission efficiency change point due to the individual difference of the bulb and to quickly converge the luminous flux to 100%. In addition to the valve voltage detection circuit 42, a bulb current detection circuit 41 is also required to calculate the bulb equivalent impedance, but the luminous efficiency change point can be detected more accurately.

Next, control of power supply reduction in the power supply control will be described with reference to FIG.
FIG. 9 corresponds to FIG. 3 described in the first embodiment, and is a control characteristic diagram defining the relationship between the bulb equivalent impedance in place of the bulb voltage in FIG. 3 and the power supplied to the bulb (discharge lamp 5).
As described above, when the bulb equivalent impedance exceeds the luminous efficiency change point target value (2) while the discharge lamp 5 is lit, the reduction of the supply power to the discharge lamp 5 is started. Control is performed according to the control characteristics of No. 9.
In FIG. 9, the control circuit 46 (2) controls the power MOSFET 314 via the PWM control circuit 43 so as to supply the maximum power W1 to the discharge lamp 5 until the bulb equivalent impedance Za at the time of detecting the luminous efficiency change point. After the valve equivalent impedance Za is exceeded, that is, after the target value (2) is exceeded, power supply to the discharge lamp 5 is reduced according to the characteristics of the approximate broken line illustrated in FIG.

  As can be understood from this approximate broken line, control is performed so that the bulb equivalent impedance during lighting changes steeply when it is close to the target value (2), and gradually changes as it approaches the bulb equivalent impedance during stable lighting. Here, the valve equivalent impedance Zb makes a transition from “steep change” to “slow change”, and between the valve equivalent impedance Za and the valve voltage equivalent impedance Zb steeply increases from the maximum power W1 to the time control start power W2. The valve equivalent impedance Zb and the valve equivalent impedance Zc change gradually from the time control start power W2 to the stable power W3. The valve equivalent impedance Zb in the above is “time control shift target value (= β × Z2)” obtained by adding a preset value (predetermined value) β to the stable valve equivalent impedance Z2, and the valve equivalent impedance Zc is stable. A “stable power target value” obtained by integrating a preset value (predetermined value) γ in the valve equivalent impedance Z2, and the power W2 are starting power when shifting to time control.

The above “time control transition target value (= β × Z2)” corresponds to the “time control transition target value (= β × V2)” in FIG. 5 and step ST2 described in the first embodiment, and the valve equivalent impedance is used as a reference. This is a target value for shifting from the control mode to the control mode based on time.
Further, the time control start power W2 is the start power when the control mode is shifted to the above time, and has the same property as that described in FIG. 3 of the first embodiment.
Also, in FIG. 9 described above, the power reduction characteristic is an approximate polygonal line characteristic, but it may be a curved line that draws a downward arc as in the first embodiment.
As described above, after detecting the light emission efficiency change point, the relationship between the electric power supplied to the discharge lamp 5 and the bulb equivalent impedance is set to an approximate broken line as shown in FIG. Immediately after the valve equivalent impedance is low but sharply increases, the power decreases sharply, and when the valve equivalent impedance increases and the valve equivalent impedance changes slowly, the power decreases gradually. In other words, the light emission amount can be kept constant even during power attenuation control.

Next, with reference to FIG. 10, a description will be given of the control for reducing the power supply in consideration of the characteristic variation due to the individual difference of the discharge lamp 5 with respect to the control for reducing the power supply described with reference to FIG.
FIG. 10 corresponds to FIG. 4 described in the first embodiment, and the control characteristics defining the relationship between the bulb equivalent impedance and the supply power to the bulb (discharge lamp 5) in consideration of the characteristic variation due to individual differences of the discharge lamp 5. FIG.
FIG. 9 is based on the assumption that the discharge lamp 5 has a fixed characteristic assumed in advance. The valve equivalent impedance Za and the stable valve equivalent impedance Z2 that is a reference for calculating the valve equivalent impedance Zb and the valve equivalent impedance Zc are as follows. It is a fixed value set in advance.
However, the discharge lamp 5 has characteristic variations due to individual differences, and the bulb equivalent impedance Za and the stable bulb equivalent impedance Z2 are not necessarily constant values. For this reason, the control with the uniform characteristics as shown in FIG.

Therefore, control in consideration of characteristic variations due to individual differences among the discharge lamps 5 is desired.
In view of this, the control characteristic of the downwardly curved curve or the approximate broken line is changed in proportion to the difference between the stable valve equivalent impedance Z2 when the discharge lamp 5 is stably lit and the minimum valve equivalent impedance Z1 immediately after the discharge lamp 5 is lit. To do.
FIG. 10 shows that the valve equivalent impedances Za, Zb, and Zc are detected or calculated by the control circuit 46 (2) for each discharge lamp 5 to be used, and the control characteristic of the approximate broken line is determined. The control characteristic Cc in the figure shows the characteristic of FIG. 9, and the control characteristic Cd shows the case where the bulb equivalent impedance Za and the stable bulb equivalent impedance Z2 are each a discharge lamp having a larger value than the discharge lamp showing the control characteristic Cc.
Thereby, the characteristic variation by the individual difference of the discharge lamp 5 is absorbed, and the light emission amount can be made constant even during power attenuation control.

Next, a power supply control mode will be described.
Also in the control of power supply in the second embodiment, for the same reason as in the first embodiment, the control mode based on the valve equivalent impedance is shifted to the control mode based on time under a certain condition. This control flow follows the flowchart of FIG. 5 described in the first embodiment. However, the time control shift target value in step ST2 in the figure is “valve stable impedance Z2 × predetermined value β”, and the control circuit 46 (2) detects the detection signals from the valve current detection circuit 41 and the valve voltage detection circuit 42, respectively. It is determined whether the valve equivalent impedance calculated based on this value has reached this time control transition target value. If this time control transition target value has not been reached (step ST2-NO), the process proceeds to step ST3 and this time control is performed. If the transition target value has been reached (step ST2-YES), the process proceeds to step ST5.
In step ST4, the control circuit 46 (2) controls the power supply to the discharge lamp 5 in a control mode based on the control characteristics based on the bulb equivalent impedance shown in FIG. 9 or FIG.
Control based on the time of step ST5 follows the control characteristics of FIG. 6 as in the first embodiment.
The processing flow of the power supply control by the other control circuit 46 (2) is the same as that of the first embodiment, and the description thereof is omitted.

As described above, when the lighting elapsed time has passed the predetermined time (step ST3-YES), for example, by changing from the control mode based on the valve equivalent impedance to the control mode based on the time, for example, the valve equivalent Even if the bulb equivalent impedance does not rise to the target value due to the case where a discharge lamp with completely different characteristics of the discharge lamp 5 such as impedance is installed on the market, the power is forcibly reduced. Therefore, it is possible to prevent excessive supply of electric power to the discharge lamp 5.
Further, the supplied power is determined according to the control characteristics of FIG. 9 or FIG. 10 until the valve equivalent impedance reaches the time control shift target value, and after the valve equivalent impedance reaches the time control shift target value (step ST2-YES). Since the supply power is determined according to the control characteristics of FIG. 6, the supply power is controlled by the valve equivalent impedance in the section where the change in the valve equivalent impedance is large, and the section in which the change in the valve equivalent impedance is small is controlled by the elapsed lighting time. Thereby, the light emission amount can be made constant even during power attenuation. Furthermore, since the time control shift target value (step ST2) is obtained by adding the predetermined value β to the stable valve equivalent impedance Z2, the variation in the valve equivalent impedance-time characteristic between individual differences of the discharge lamp 5 is absorbed. Thus, a shift to time control is performed, and electric power suitable for the discharge lamp 5 can be supplied in accordance with the control characteristics of FIG.

As described above, according to the second embodiment, the difference (Z2−Z1) between the stable valve equivalent impedance Z2 when the discharge lamp 5 is stably lit and the minimum valve equivalent impedance Z1 immediately after lighting is statistically determined by experiments. The value obtained by adding the minimum valve equivalent impedance Z1 to the value obtained by multiplying the ratio α2 obtained by the above equation is set as the luminous efficiency change point target value (2), and the control circuit 46 (2) Is lower than the luminous efficiency change point target value (2), the maximum power is supplied to the discharge lamp 5, and when the current equivalent impedance exceeds the target value (2), the reduction of the power supplied to the discharge lamp 5 is started. As described above, the power conversion unit 3 is controlled so that the luminous efficiency change point target value (2) is set according to the discharge lamp 5 that is actually mounted, as in the first embodiment. Is constant, thereby absorbing the variation in luminous efficiency change point due to valve individual difference, quickly the light beam can be converged to 100%.
In addition to the bulb voltage detection circuit 42, the bulb current detection circuit 41 is also required for calculating the bulb equivalent impedance, but the luminous efficiency change point can be detected more accurately.

After the luminous efficiency change point target value (2) is exceeded, the relationship between the power supplied to the discharge lamp 5 and the bulb equivalent impedance is set to the characteristic of an approximate broken line as shown in FIG. The power is reduced sharply for the section where the valve equivalent impedance immediately rises sharply, and the power is gradually reduced for the section where the change in valve equivalent impedance is slow. Can be constant.
Furthermore, by changing the control characteristic of the approximate polygonal line or the curve that draws the downward arc in proportion to the difference between the stable bulb equivalent impedance Z2 and the minimum bulb equivalent impedance Z1 of the discharge lamp 5, as shown in FIG. Characteristic variations due to individual differences among the discharge lamps 5 are absorbed, and the light emission amount can be made constant even during power attenuation control.

In addition, when the lighting elapsed time has passed a predetermined time, the mode shifts from the form of power control with the bulb equivalent impedance to the form of power control with time. For example, the discharge lamp 5 whose characteristics are completely different from those currently on the market. Even if the bulb equivalent impedance does not rise to the target value due to the mounting, etc., the power is forcibly reduced, so that it is possible to prevent excessive supply of power to the discharge lamp 5.
Further, until the time control shift target value is reached, the control characteristic of FIG. 9 or FIG. 10 is followed. After the valve equivalent impedance reaches the time control shift target value, the control characteristic of FIG. By controlling the power with the bulb equivalent impedance in the section and controlling the power with the lighting elapsed time in the section where the change in the bulb equivalent impedance is small, the light emission amount can be made constant even during the power decay. Furthermore, since the target value for time control shift is obtained by integrating the predetermined value β with the stable valve equivalent impedance Z2, the time control is performed in a manner that absorbs the variation in the valve voltage-time characteristics between individual differences of the discharge lamp 5. Thus, the power suitable for the discharge lamp 5 can be supplied.

Embodiment 3 FIG.
FIG. 11 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the third embodiment of the present invention.
1 will be described as the control circuit 46 (3), and the luminous efficiency change point target value will be described as the luminous efficiency change point target value (3).
Focusing on the fact that the target value (3) of the luminous efficiency change point in the third embodiment has a correlation between the stable bulb equivalent impedance Z2 when the discharge lamp 5 is stably lit and the bulb equivalent impedance at the luminous efficiency change point, The ratio α3 of the bulb equivalent impedance at the time of stable lighting and at the light emission efficiency change point is set by measuring in advance by an experimental statistical method or the like, and the control circuit 46 (3), as shown in FIG. A calculation is performed according to a calculation formula “α3 × Z2” obtained by multiplying Z2 by a ratio α3, and a value obtained by this calculation is set as a luminous efficiency change point target value (3).
The method for obtaining the stable valve equivalent impedance Z2 and the storage of the stable valve equivalent impedance Z2 in the memory circuit 44 are as described in the second embodiment.

When the current bulb equivalent impedance of the discharge lamp 5 is lower than the luminous efficiency change point target value (3), the control circuit 46 (3) supplies the maximum electric power to the discharge lamp 5, and the current bulb equivalent impedance is the luminous efficiency. After the change point target value (3) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power converter 3 is controlled. .
As a result, it is possible to absorb the variation at the light emission efficiency change point due to the individual difference of the bulb and to quickly converge the luminous flux to 100%.
Further, although the accuracy of detecting the light emission efficiency change point is inferior because the minimum valve equivalent impedance Z1 is not detected, it is possible to determine whether or not the light emission efficiency change point has been reached immediately after lighting, and to cope with hot start.

  In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 Although the reduction control (FIG. 10), the power supply control mode (FIGS. 5 and 6), etc. are also applied to the third embodiment, they are as described in the second embodiment, and the description thereof is omitted. To do.

  As described above, according to the third embodiment, the value obtained by the calculation obtained by multiplying the stable bulb equivalent impedance Z2 when the discharge lamp 5 is stably lit by the ratio α3 statistically obtained by experiments is obtained. The change point target value (3) is set, and the control circuit 46 (3) supplies the maximum power to the discharge lamp 5 when the current bulb equivalent impedance is lower than the light emission efficiency change point target value (3). When the equivalent impedance exceeds the target value (3), the power converter 3 is controlled so as to start reducing the power supplied to the discharge lamp 5, so that it is actually mounted as in the second embodiment. The target value (3) of the luminous efficiency change point is set according to the discharge lamp 5 to be absorbed, thereby absorbing the variation at the luminous efficiency change point due to the individual difference of the bulb and quickly converging the luminous flux to 100%. It can be.

Further, although the accuracy of detecting the light emission efficiency change point is inferior because the minimum valve equivalent impedance Z1 is not detected, it is possible to determine whether or not the light emission efficiency change point has been reached immediately after lighting, and to cope with hot start.
In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 The reduction control (FIG. 10) and the power supply control mode (FIGS. 5 and 6) can be applied to the third embodiment, and the effects described in the second embodiment can be enjoyed.

Embodiment 4 FIG.
FIG. 12 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the fourth embodiment of the present invention.
1 will be described as the control circuit 46 (4), and the luminous efficiency change point target value will be described as the luminous efficiency change point target value (4).
The luminous efficiency change point target value (4) in the fourth embodiment pays attention to the fact that the bulb equivalent impedance characteristic of FIG. 12 is close to the bathtub curve shown in FIG. 7, and the control circuit 46 (4) The constant valve equivalent impedance Z3 immediately after lighting is stored in the memory circuit 44, and a calculation is performed by a calculation formula “Z3 + α4” obtained by adding a predetermined value α4 to the constant valve equivalent impedance Z3. Set as target value (4). The predetermined value α4 is measured and set in advance by an experimental statistical method or the like.
Here, if the change in the valve equivalent impedance within a predetermined time to immediately after lighting is within the predetermined value ΔZ1 and the difference from the stored constant valve equivalent impedance is within the predetermined value ΔZ2, the constant valve equivalent impedance Z3 immediately after lighting is set. It is possible to cope with aging deterioration of the valve by renewing.
In addition, what is necessary is just to follow the method of calculating | requiring the valve equivalent impedance Z1 etc. which were demonstrated in Embodiment 2 about the method of calculating | requiring the constant valve equivalent impedance Z3.

The control circuit 46 (4) supplies the maximum electric power to the discharge lamp 5 when the current bulb equivalent impedance of the discharge lamp 5 is lower than the luminous efficiency change point target value (4), and the current bulb equivalent impedance is the luminous efficiency. After the change point target value (4) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power converter 3 is controlled. .
As a result, it is possible to absorb the variation at the light emission efficiency change point due to the individual difference of the bulb and to quickly converge the luminous flux to 100%. In addition, it is effective for a bulb having a bulb equivalent impedance characteristic close to a bathtub curve, and it is possible to determine whether or not a light emission efficiency change point has been reached immediately after lighting, and to cope with hot start.

  In addition to the above, the supply power reduction control after exceeding the target value described in the second embodiment (FIG. 9), the supply power reduction control in consideration of the characteristic variation due to individual differences of the discharge lamp 5 (FIG. 10). The power supply control mode (FIGS. 5 and 6) and the like are also applied to the fourth embodiment, but are the same as those described in the second embodiment, and the description thereof is omitted.

As described above, according to the fourth embodiment, the value obtained by calculation by adding the predetermined value α4 to the constant bulb equivalent impedance Z3 immediately after the discharge lamp 5 is turned on is set as the luminous efficiency change point target value (4). The control circuit 46 (4) supplies the maximum power to the discharge lamp 5 when the current bulb equivalent impedance is lower than the luminous efficiency change point target value (4), and the current equivalent impedance is the target value (4). Since the power conversion unit 3 is controlled so as to start the reduction of the power supplied to the discharge lamp 5 when exceeding the value, light emission is performed according to the actually mounted discharge lamp 5 as in the second embodiment. An efficiency change point target value (4) is set, whereby the variation at the light emission efficiency change point due to individual valve differences can be absorbed, and the luminous flux can be quickly converged to 100%. In particular, according to the fourth embodiment, the bulb equivalent impedance characteristic is effective for a bulb having a characteristic close to a bathtub curve, and it is possible to determine whether or not the light emission efficiency change point has been reached immediately after lighting, and also supports hot start. be able to.
In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 The reduction control (FIG. 10) and the power supply control mode (FIGS. 5 and 6) can be applied to the fourth embodiment, and the effects described in the second embodiment can be enjoyed.

Embodiment 5 FIG.
FIG. 13 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the fifth embodiment of the present invention.
1 will be described as the control circuit 46 (5), and the luminous efficiency change point target value will be described as the luminous efficiency change point target value (5).
The light emission efficiency change point target value (5) in the fifth embodiment sequentially detects the bulb equivalent impedance during lighting, and as shown in FIG. 13, a predetermined value α5 is set to the minimum bulb equivalent impedance Z1 in the continuous characteristics. Is calculated in the control circuit 46 (5), and the value obtained by this calculation is set as the luminous efficiency change point target value (5). The predetermined value α5 is measured and set in advance by an experimental statistical method or the like.
The method for obtaining the minimum valve equivalent impedance Z1 is as described in the second embodiment.

The control circuit 46 (5) supplies maximum electric power to the discharge lamp 5 when the current bulb equivalent impedance of the discharge lamp 5 is lower than the target value (5) of the luminous efficiency change point, and the current bulb equivalent impedance is the luminous efficiency. After the change point target value (5) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power converter 3 is controlled. .
As a result, it is possible to absorb the variation at the light emission efficiency change point due to the individual difference of the bulb and to quickly converge the luminous flux to 100%. Since the added value is the predetermined value α5, the light emission efficiency change point detection accuracy is inferior, but the memory circuit 44 is not necessary, and the replacement of the discharge lamp 5 can be dealt with.

  In addition to the above, the supply power reduction control after exceeding the target value described in the second embodiment (FIG. 9), the supply power reduction control in consideration of the characteristic variation due to individual differences of the discharge lamp 5 (FIG. 10). The power supply control mode (FIGS. 5 and 6) and the like are also applied to the fifth embodiment, but are the same as those described in the second embodiment, and the description thereof is omitted.

As described above, according to the fifth embodiment, the bulb equivalent impedance during lighting is sequentially detected, and the value obtained by calculation by adding the predetermined value α5 to the minimum bulb equivalent impedance Z1 in the continuous characteristics is emitted. The efficiency change point target value (5) is set, and the control circuit 46 (5) supplies the maximum power to the discharge lamp 5 when the current bulb equivalent impedance is lower than the light emission efficiency change point target value (5). Since the power conversion unit 3 is controlled to start the reduction of the power supplied to the discharge lamp 5 when the equivalent impedance exceeds the target value (5), as in the second embodiment, actually The luminous efficiency change point target value (5) is set according to the discharge lamp 5 to be mounted, and this absorbs the variation at the luminous efficiency change point due to the individual difference of bulbs, and converges the luminous flux quickly to 100%. It can be.
Further, according to the fifth embodiment, the memory circuit 44 is not necessary, and the replacement of the discharge lamp 5 can be easily dealt with.
In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 The reduction control (FIG. 10) and the power supply control mode (FIGS. 5 and 6) can be applied to the fifth embodiment, and the effects described in the second embodiment can be enjoyed.

Embodiment 6 FIG.
FIG. 14 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the sixth embodiment of the present invention.
In the sixth embodiment, the control circuit 46 in FIG. 1 (overall configuration) will be described as the control circuit 46 (6), and the light emission efficiency change point target value will be described as the light emission efficiency change point target value (6).
The target value of the luminous efficiency change point in the sixth embodiment focuses on the fact that the luminous efficiency and the bulb equivalent impedance rapidly increase when the metal halide in the tube of the discharge lamp 5 starts to evaporate. Since the bulb equivalent impedance slope at the luminous efficiency change point changes in proportion to the difference (Z2−Z1) between the stable bulb equivalent impedance Z2 and the minimum bulb equivalent impedance Z1 immediately after lighting, the difference (Z2−Z1). ) And the ratio α6 of the bulb equivalent impedance slope at the luminous efficiency change point are previously measured and set by an experimental statistical method or the like, and the control circuit 46 (6), as shown in FIG. ) Is multiplied by the ratio α6, and a calculation formula “α6 × (Z2−Z1)” is performed. To set up as.

  Note that the valve equivalent impedances Z1 and Z2 or how to obtain the current valve equivalent impedance and the stable valve equivalent impedance Z2 are stored in the memory circuit 44 are as described in the second embodiment. The control circuit 46 (6) detects a valve equivalent impedance gradient that is a gradient of the current valve equivalent impedance with respect to time.

The control circuit 46 (6) supplies the maximum electric power to the discharge lamp 5 when the current bulb equivalent impedance slope of the discharge lamp 5 is lower than the luminous efficiency change point target value (6), and the current bulb equivalent impedance slope is After the luminous efficiency change point target value (6) is exceeded, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power conversion unit 3 supplies power to the discharge lamp 5. Control.
As a result, it is possible to absorb the variation at the light emission efficiency change point due to the individual difference of the bulb and to quickly converge the luminous flux to 100%. In addition, since the determination is made based on the bulb equivalent impedance gradient, the luminous efficiency change point can be detected more accurately.

  In addition to the above, the supply power reduction control after exceeding the target value described in the second embodiment (FIG. 9), the supply power reduction control in consideration of the characteristic variation due to individual differences of the discharge lamp 5 (FIG. 10). The power supply control mode (FIGS. 5 and 6) and the like are also applied to the sixth embodiment, but are the same as those described in the second embodiment, and the description thereof is omitted.

As described above, according to the sixth embodiment, the valve equivalent impedance statistically obtained by experiments is calculated as the difference (Z2-Z1) between the stable valve equivalent impedance Z2 and the minimum valve equivalent impedance Z1 of the discharge lamp 5. A value obtained by the multiplication by the inclination ratio α6 is set as the luminous efficiency change point target value (6), and the control circuit 46 (6) determines that the current bulb equivalent impedance inclination is the luminous efficiency change point target value (6). ), The power converter 3 is controlled so as to supply the maximum power to the discharge lamp 5 and to start reducing the power supplied to the discharge lamp 5 when the current equivalent impedance slope exceeds the target value (6). As in the second embodiment, the luminous efficiency change point target value (6) is set in accordance with the discharge lamp 5 that is actually mounted, and as a result, depending on the individual valve difference. To absorb variations in light efficiency change point, quickly the light beam can be converged to 100%.
In addition, since the determination is made based on the bulb equivalent impedance gradient, the luminous efficiency change point can be detected more accurately.
In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 The reduction control (FIG. 10) and the power supply control mode (FIGS. 5 and 6) can be applied to the third embodiment, and the effects described in the second embodiment can be enjoyed.

Embodiment 7 FIG.
FIG. 15 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the seventh embodiment of the present invention.
1 will be described as the control circuit 46 (7), and the light emission efficiency change point target value will be described as the light emission efficiency change point target value (7).
The luminous efficiency change point target value (7) in the seventh embodiment is a positive valve equivalent impedance slope value (predetermined value) α7 set in advance.
Further, the control circuit 46 (7) obtains the current valve equivalent impedance (second embodiment), and detects the valve equivalent impedance gradient that is the gradient of the valve equivalent impedance with respect to time.

The control circuit 46 (7) supplies the maximum electric power to the discharge lamp 5 when the current bulb equivalent impedance slope of the discharge lamp 5 is lower than the luminous efficiency change point target value (7), and the current bulb equivalent impedance slope is After exceeding the luminous efficiency change point target value (7), the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power conversion unit 3 supplies power to the discharge lamp 5. Control.
As a result, the accuracy of detecting the luminous efficiency change point is inferior, but the memory circuit 44 is not necessary, and the replacement of the discharge lamp 5 can be dealt with.

  In addition to the above, the supply power reduction control after exceeding the target value described in the second embodiment (FIG. 9), the supply power reduction control in consideration of the characteristic variation due to individual differences of the discharge lamp 5 (FIG. 10). The power supply control mode (FIGS. 5 and 6) and the like are also applied to the seventh embodiment, but are the same as those described in the second embodiment, and the description thereof is omitted.

As described above, according to the seventh embodiment, the preset positive valve equivalent impedance slope value α7 is set as the light emission efficiency change point target value (7), and the control circuit 46 (7) When the equivalent impedance slope is lower than the luminous efficiency change point target value (7), the maximum power is supplied to the discharge lamp 5, and when the current equivalent impedance slope exceeds the target value (7), the power supplied to the discharge lamp 5 is supplied. Since the power conversion unit 3 is controlled so as to start the reduction, the light flux can be rapidly converged to 100% with a simple configuration that does not require the memory circuit 44. Further, it is possible to easily cope with replacement of the discharge lamp 5.
In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value (3) is exceeded as described in the second embodiment (FIG. 9), and the power supply in consideration of characteristic variations due to individual differences of the discharge lamp 5 The reduction control (FIG. 10) and the power supply control mode (FIGS. 5 and 6) can be applied to the third embodiment, and the effects described in the second embodiment can be enjoyed.

Embodiment 8 FIG.
FIG. 16 is a diagram showing a bulb equivalent impedance-time characteristic and a luminous efficiency change point target value for explaining the luminous efficiency change point target value in the eighth embodiment of the present invention.
Note that the control circuit 46 in FIG. 1 (overall configuration) in the eighth embodiment will be described as a control circuit 46 (8).
The light emission efficiency change point target values in the eighth embodiment are a plurality of types of light emission efficiencies determined in advance from the light emission efficiency change point target values ((1) to (7)) of the first to seventh embodiments. A change point target value is provided.
FIG. 16 shows “α2 × (Z2−Z1) + Z1” that is the target value (2) of the luminous efficiency change point in the second embodiment and “α6 ×” that is the target value (6) of the luminous efficiency change point in the sixth embodiment. This is an example in which two types of target points for light emission efficiency change points (Z2-Z1) are provided.
Thus, the control circuit 46 (8) is provided with a function of setting the plurality of types of light emission efficiency change point target values with calculated values or predetermined values. The calculated values or predetermined values of the individual light emission efficiency change point target values forming the plurality of types are as described in the first to seventh embodiments.

The control circuit 46 (8) supplies the maximum power to the discharge lamp 5 until the achievement of any target value of the set plural types of luminous efficiency change point target values, and the achievement of any target value is achieved. After the establishment, the power MOSFET 314 is controlled via the PWM control circuit 43 so as to reduce the power supplied to the discharge lamp 5, and the power supply to the discharge lamp 5 by the power conversion unit 3 is controlled.
In the case of FIG. 16, the control circuit 46 (8) determines which of the two types of luminous efficiency change point target values “α2 × (Z2−Z1) + Z1” or “α6 × (Z2−Z1)”. The maximum power is supplied to the discharge lamp 5 until the target value is achieved, and the power supplied to the discharge lamp 5 is reduced when the target value is achieved.
As a result, the luminous flux can be quickly converged to 100%.
Further, by detecting the luminous efficiency change point under a plurality of conditions, it is possible to supply appropriate electric power to the discharge lamp 5 even when the discharge lamp 5 having any characteristics is mounted or in any lighting state. .

In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value is exceeded as described in the first and second embodiments (FIGS. 3 and 9), and the characteristic variation due to individual differences in the discharge lamp 5 In the eighth embodiment, the control characteristics shown in FIGS. 3, 4, or 9 and 10 are controlled according to the target value of the luminous efficiency change point established in the eighth embodiment. Applied. The specific contents are as described in the first embodiment or the second embodiment, and the description thereof is omitted.
The power supply control mode (FIGS. 5 and 6) is also applied to the eighth embodiment. In this eighth embodiment, the time control shift target value in step ST2 of FIG. 5 is established. Either “β × V2 (FIGS. 3 and 4)” or “β × Z2 (FIGS. 9 and 10)” is set in the control circuit 46 (8) in accordance with the target value of the luminous efficiency change point. The other processing flow of FIG. 5 is as described in the first and second embodiments, and the description thereof is omitted.
Further, the control based on the time of step ST5 in FIG. 5 follows the control characteristics of FIG. 6 as in the first embodiment.

  As described above, according to the eighth embodiment, a plurality of types determined in advance from the light emission efficiency change point target values ((1) to (7)) of the first to seventh embodiments. Since the light emission efficiency change point target value is provided, the light emission efficiency change point is detected under a plurality of conditions. Even when the discharge lamp 5 having any characteristic is mounted or in any lighting state. Appropriate power can be supplied to the discharge lamp 5, and the luminous flux can be quickly converged to 100%.

In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value is exceeded as described in the first and second embodiments (FIGS. 3 and 9), and the characteristic variation due to individual differences in the discharge lamp 5 In the eighth embodiment, the control characteristics shown in FIGS. 3, 4, or 9 and 10 are controlled according to the target value of the luminous efficiency change point established in the eighth embodiment. It is applied and the effects described in the respective embodiments can be enjoyed.
The power supply control mode (FIGS. 5 and 6) is also applied to the eighth embodiment, and the effects described in the first or second embodiment can be enjoyed.

Embodiment 9 FIG.
FIG. 17 is a diagram showing a bulb voltage-time characteristic and a light emission efficiency change point target value for explaining the light emission efficiency change point target value in the ninth embodiment of the present invention.
The control circuit 46 in FIG. 1 (entire configuration) in the ninth embodiment will be described as the control circuit 46 (9).
The luminous efficiency change point target values in the ninth embodiment are obtained by dividing each of the luminous efficiency change point target values ((1) to (7)) of the first to seventh embodiments into a plurality of stages. It is.
FIG. 17 shows a change in luminous efficiency obtained by multiplying the ratio α1 ′ of the valve voltage slope lower than α1 in addition to “α1 × (V2−V1)” which is the same luminous efficiency change point target value (1) as in the first embodiment. In this example, the target value (1 ′) is set to be divided into two-step luminous efficiency change point target values of “α1 ′ × (V2−V1)”. The valve voltage slope ratio α1 ′ is also measured and set in advance by an experimental statistical method or the like, similarly to α1.

The control circuit 46 (9) supplies the maximum power to the discharge lamp 5 until the first stage of the luminous efficiency change point target value divided into a plurality of stages is exceeded, and when the first stage of the plurality of stages is exceeded. The power MOSFET 314 is controlled via the PWM control circuit 43 so as to gradually reduce the supplied power from the maximum power, and to reduce the supplied power more steeply in the subsequent stages, and the power to the discharge lamp 5 by the power conversion unit 3 Control the supply.
In the case of FIG. 17, the control circuit 46 (9) causes the discharge lamp 5 until the bulb voltage exceeds “α1 ′ × (V2−V1)” among the luminous efficiency change point target values divided into the above two stages. Is supplied when the valve voltage exceeds “α1 × (V2−V1)”, and when the valve voltage exceeds “α1 × (V2−V1)”. The power supply is controlled so as to reduce the power more rapidly.
As a result, the feedback delay from the detection point of the luminous efficiency change to the power reduction is absorbed, and after the light emission amount suddenly increases at the light emission efficiency change point, the light emission amount due to the power reduction decreases and the light emission amount sharply increases or decreases. And the amount of light emission can be changed smoothly.

In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value is exceeded as described in the first and second embodiments (FIGS. 3 and 9), and the characteristic variation due to individual differences in the discharge lamp 5 In the ninth embodiment, the control characteristics shown in FIG. 3, FIG. 4, or FIG. 9 and FIG. 10 are controlled according to the set target value of the light emission efficiency change point. Applied. The specific contents are as described in the first embodiment or the second embodiment, and the description thereof is omitted.
The power supply control mode (FIGS. 5 and 6) is also applied to the ninth embodiment. In this ninth embodiment, the time control shift target value in step ST2 of FIG. 5 is set. Either “β × V2 (FIGS. 3 and 4)” or “β × Z2 (FIGS. 9 and 10)” is set in the control circuit 46 (9) in accordance with the target value of the luminous efficiency change point. The other processing flow of FIG. 5 is as described in the first and second embodiments, and the description thereof is omitted.
Further, the control based on the time of step ST5 in FIG. 5 follows the control characteristics of FIG. 6 as in the first embodiment.

  As described above, according to the ninth embodiment, each of the luminous efficiency change point target values ((1) to (7)) of the first to seventh embodiments is set in a plurality of stages. As a result, the feedback delay from detection of the light emission efficiency change point to power reduction is absorbed, and after the light emission amount suddenly increases at the light emission efficiency change point, the light emission amount due to power reduction decreases and the light emission amount becomes steep. Increase and decrease are prevented, and the amount of light emission can be changed smoothly.

In addition to the above, the control for reducing the power supply after the luminous efficiency change point target value is exceeded as described in the first and second embodiments (FIGS. 3 and 9), and the characteristic variation due to individual differences in the discharge lamp 5 In the ninth embodiment, the control characteristics shown in FIG. 3, FIG. 4, or FIG. 9 and FIG. 10 are controlled according to the set target value of the light emission efficiency change point. Applied, the effect described in the first embodiment or the second embodiment can be enjoyed.
Further, the power supply control mode (FIGS. 5 and 6) is also applied to the ninth embodiment, and the effects described in the first or second embodiment can be enjoyed.

It is a block diagram which shows the whole structure of the discharge lamp lighting device by this invention. It is a figure which shows the bulb voltage-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 1 of this invention. It is a control characteristic figure which prescribed | regulated the relationship between the valve voltage and the electric power supplied to a valve | bulb regarding Embodiment 1 of this invention. FIG. 5 is a control characteristic diagram that prescribes the relationship between the bulb voltage and the power supplied to the bulb in consideration of the characteristic variation due to individual differences among the discharge lamps, according to the first embodiment of the present invention. It is a flowchart which shows the process of the electric power supply control by a control circuit regarding Embodiment 1 of this invention. It is a control characteristic figure which prescribed | regulated the relationship between lighting elapsed time and the electric power supplied to a valve | bulb regarding Embodiment 1 of this invention. It is a figure which shows the bulb voltage-time characteristic for the conventional mercury-less discharge lamp description regarding Embodiment 1 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 2 of this invention. It is a control characteristic figure which prescribed | regulated the relationship between valve | bulb equivalent impedance and the electric power supplied to a valve | bulb regarding Embodiment 2 of this invention. It is a control characteristic figure which prescribed | regulated the relationship between the valve | bulb equivalent impedance which considered the characteristic variation by the individual difference of a discharge lamp, and the electric power supplied to a valve | bulb regarding Embodiment 2 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 3 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 4 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 5 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 6 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 7 of this invention. It is a figure which shows the valve | bulb equivalent impedance-time characteristic and luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 8 of this invention. It is a figure which shows the bulb voltage-time characteristic and the luminous efficiency change point target value for demonstrating the luminous efficiency change point target value in Embodiment 9 of this invention.

Explanation of symbols

1 DC power supply, 2 lighting switch, 3 power conversion unit, 4 control unit, 5 discharge lamp, 31 DC / DC converter, 32 takeover circuit, 33 current detection resistor, 34 H bridge circuit, 35 H bridge driver circuit, 36 Igniter, 41 valve current detection circuit, 42 valve voltage detection circuit, 43 PWM control circuit, 44 memory circuit, 45 timer circuit, 46 control circuit, 311 flyback transformer, 312 rectifier diode, 313 smoothing capacitor, 314 power MOSFET, 321 charge Series resistor for discharging, 322 capacitor, 341, 342, 343, 344 FET.

Claims (11)

Connected to a DC power supply, the power supply voltage of the DC power supply is converted into a DC voltage of a predetermined value, DC power generated by the DC voltage is converted into AC power, and the discharge is started by a high voltage pulse generated based on the AC. A power converter for supplying power to the lamp;
A storage device for storing the stable valve voltage at the time of stable lighting measured at the time of previous lighting and the stable valve equivalent impedance calculated from the stable valve current;
Sets the value calculated by the calculation formula which is preset based on cheap scheduled valve equivalent impedance of the last with the stored as luminous efficiency change point target value, detects the current valve voltage and valve current, the current valve voltage And determining whether the set luminous efficiency change point target value has been achieved based on the bulb current, and supplying the maximum power to the discharge lamp until the achievement of the luminous efficiency change point target value is achieved. A discharge lamp lighting device comprising: a control unit that controls power supply by the power conversion unit so as to reduce power supplied to the discharge lamp after the achievement of the luminous efficiency change point target value is achieved.   The control unit calculates a stable valve equivalent impedance when the discharge lamp is stably lit and a minimum valve equivalent impedance immediately after lighting based on the valve voltage and the valve current, and calculates the stable valve equivalent impedance and the minimum valve equivalent impedance. A value obtained by adding the minimum valve equivalent impedance to a value obtained by multiplying the difference by a preset ratio is set as the luminous efficiency change point target value, and the current valve equivalent impedance is set as the valve voltage and the valve current. When the current bulb equivalent impedance is lower than the light emission efficiency change point target value, the maximum power is supplied to the discharge lamp, and after the current bulb equivalent impedance exceeds the target value, the discharge lamp Control the power converter to reduce the power supplied to the The discharge lamp lighting device according to claim 1, wherein the door.   The control unit calculates the stable bulb equivalent impedance when the discharge lamp is steadily lit based on the bulb voltage and bulb current, and emits a value obtained by a formula obtained by multiplying the stable bulb equivalent impedance by a predetermined ratio. It is set as the efficiency change point target value, and the current bulb equivalent impedance is calculated based on the bulb voltage and bulb current. When this current bulb equivalent impedance is lower than the luminous efficiency change point target value, the maximum value is supplied to the discharge lamp. 2. The discharge lamp according to claim 1, wherein power is supplied and the power conversion unit is controlled to reduce power supplied to the discharge lamp after the current bulb equivalent impedance exceeds the target value. Lighting device.   The control unit calculates a stable valve equivalent impedance when the discharge lamp is stably lit and a minimum valve equivalent impedance immediately after lighting based on the valve voltage and the valve current, and calculates the stable valve equivalent impedance and the minimum valve equivalent impedance. A value obtained by a formula obtained by multiplying the difference by the ratio of the preset valve equivalent impedance slope is set as the target value of the luminous efficiency change point, and the bulb equivalent impedance slope, which is the slope of the current bulb equivalent impedance with respect to time, is set as the valve voltage. When the current bulb equivalent impedance slope is lower than the luminous efficiency change point target value, the maximum electric power is supplied to the discharge lamp, and the current bulb equivalent impedance slope has the target value. After exceeding, supply to the discharge lamp The discharge lamp lighting device according to claim 1, wherein the controlling the power conversion unit so as to reduce power. The control unit sets the light emission efficiency change point target value according to at least two of claims 2 to 4 , and detects a current valve voltage gradient, a valve equivalent impedance, or a valve equivalent impedance gradient, When the current bulb voltage gradient, bulb equivalent impedance, or bulb equivalent impedance gradient is lower than the luminous efficiency change point target value, the maximum electric power is supplied to the discharge lamp, and the current bulb voltage gradient, bulb equivalent impedance or bulb is supplied. 2. The discharge lamp lighting device according to claim 1, wherein after one of the equivalent impedance slopes exceeds the target value, the power conversion unit is controlled so as to reduce power supplied to the discharge lamp. The control unit sets the luminous efficiency change point target value in a plurality of stages, and when the luminous efficiency change point target value in the first stage is exceeded, the power supplied to the discharge lamp begins to be gradually reduced, and the final stage according to any one of the luminous efficiency change point claims 1 to 5 when it exceeds the target value, characterized in that to control the power conversion unit so as to sharply reduce the power supplied to the discharge lamp Discharge lamp lighting device. Minimum valve equivalent impedance immediately after lighting of the discharge lamp, bulb equivalent impedance continuously changed in successive calculated valve equivalent impedance - claim 2, characterized in that it has a minimum value in the time characteristics, claim 4 The discharge lamp lighting device according to any one of 6 . The control unit determines the power supply to the discharge lamp after the light emission efficiency change point target value is exceeded according to a control characteristic set in advance as a relationship between the bulb equivalent impedance and the discharge lamp supply power. It is a curve or approximate polygonal line that draws a downward arc so that it changes sharply when it is close to the target value of luminous efficiency change point, and gradually changes as it approaches the bulb equivalent impedance during stable lighting. The discharge lamp lighting device according to any one of claims 1 to 6 . 9. The discharge lamp lighting device according to claim 8 , wherein the slope of the control characteristic changes in proportion to a difference between a stable bulb equivalent impedance during stable lighting and a minimum bulb equivalent impedance immediately after lighting. A timer circuit for detecting the elapsed lighting time of the discharge lamp is provided, and the control unit reduces the power supplied to the discharge lamp according to the elapsed lighting time when the elapsed lighting time detected by the timer circuit reaches a preset time. The discharge lamp lighting device according to any one of claims 1 to 6 , wherein the power conversion unit is controlled to do so. A timer circuit for detecting the lighting elapsed time of the discharge lamp is provided, and the control unit has elapsed when the lighting elapsed time detected by the timer circuit has passed a preset time and the bulb equivalent impedance has reached the time control transition target value. The control shifts from the control according to the control characteristic preset as the relation between the bulb equivalent impedance and the discharge lamp supply power to the control according to the control characteristic preset as the relation between the lighting elapsed time and the discharge lamp supply power. control migration target value is a value obtained by integrating the stable time preset value the valve equivalent impedance during stable lighting, claim from claim 1, characterized in that the luminous efficiency change point target value or values The discharge lamp lighting device according to any one of 6 .

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