JPH09237691A - Discharge lamp lighting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform power control of a discharge lamp in such a way that light flux of the discharge lamp becomes a rated light flux without complicating a circuit constitution. SOLUTION: A circuit 1 is provided with a power control means 5 which first performs supply of power exceeding a rated power to a discharge lamp 6, decreases the supply power to the discharge lamp next, and then performs constant power control to the discharge lamp 6 for lighting the discharge lamp 6 from a cold condition. A transition control means 8 for transition to the constant power control to the discharge lamp 6 after performing supply of power exceeding the rated power of it is composed to have plural time constant circuits of different time constants, or have a time constant circuit of an order number of two or more, and power control is performed to change a reduction rate of supply power to the discharge lamp 6 as time passes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting circuit for performing power control such that when the discharge lamp is lit, power exceeding the rated power is supplied and then constant power control is performed.

[0002]

2. Description of the Related Art Recently, a small discharge lamp (for example, a metal halide lamp) has been attracting attention as a light source to replace an incandescent light bulb. For example, the lighting circuit has a DC power supply, a DC power supply circuit, and a DC-AC conversion. A device including a circuit, a starting circuit, etc. is known.

In order to shorten the starting time and the restarting time of the discharge lamp, the arc tube is warmed rapidly by supplying electric power exceeding the rated power at the initial lighting of the discharge lamp.
Methods of promoting light emission are known.

However, when the electric power supplied to the discharge lamp is suddenly changed, overshoot and undershoot become remarkable in the change of the luminous flux of the discharge lamp, and the fluctuation of the luminous flux becomes large, so that the luminous flux of the discharge lamp is stabilized. There is a problem that it is difficult to reduce the time required for the process.

Therefore, in shifting from the control for supplying electric power exceeding the rated power of the discharge lamp (hereinafter referred to as "light emission promotion control") to the constant power control at the rated power of the discharge lamp in the initial stage of lighting of the discharge lamp. A circuit configured to gradually reduce the power supplied to the discharge lamp over time and finally perform power control so that the power supplied reaches the rated power is conceivable.

[0006]

By the way, when the discharge lamp is not always in the same state when it is lit, when the discharge lamp is lit when the arc tube is cold (hereinafter, "cold start"). There is a case in which the discharge lamp is turned on while the arc tube after the discharge lamp is turned off is still at a high temperature (hereinafter referred to as “hot start”), or an intermediate case between the two.

Therefore, in the circuit in which the reduction rate of the power supplied to the discharge lamp is fixed to a certain constant value during the transition from the light emission promotion control to the constant power control, an undershoot or an overshoot with respect to a temporal change of the luminous flux of the discharge lamp is generated. There is a problem that it is difficult to reduce the shoot.

That is, even if the reduction rate of the supplied power is set to a certain value and the luminous flux change is obtained without any problem at the cold start, the set value of the reduction rate is not always valid in the control at the hot start. .

Therefore, the state when the discharge lamp is lit (that is,
A method of controlling the power supplied to the discharge lamp separately by determining whether it is cold start, hot start or an intermediate state between the two is conceivable. However, if a control circuit is provided for each state, the circuit configuration will be different. Has the disadvantage that it becomes complicated.

An object of the present invention is to control the electric power of a discharge lamp so that the luminous flux of the discharge lamp quickly reaches a rated luminous flux without complicating the circuit configuration.

[0011]

In order to solve the above-mentioned problems, the discharge lamp lighting circuit of the present invention shifts to the constant power control of the discharge lamp after supplying the discharge lamp with power exceeding its rated power. The transition control means of (1) has a plurality of time constant circuits having different time constants or a time constant circuit whose order is two or more, and the time constant changes with the passage of time,
The power control is performed so that the rate of decrease of the power supplied to the discharge lamp changes accordingly.

Therefore, according to the present invention, the reduction rate of the electric power supplied to the discharge lamp can be temporally changed by the combination of the plurality of time constants by the shift control means.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of a discharge lamp lighting circuit 1 according to the present invention, which comprises a power supply 2, a lighting control means 3, a lamp voltage / current detection means 4, and a power control means 5.

The lighting control means 3 is provided for controlling the lighting of the discharge lamp 6 based on the AC or DC power supply voltage supplied from the power supply 2, and its output is a control signal from the power control means 5. Controlled by. The lighting control unit 3 includes a starting circuit for starting the discharge lamp 6 by generating a starting pulse in the initial lighting of the discharge lamp 6.

The lamp voltage / current detection means 4 uses the lighting control means 3 as a lamp voltage or lamp current supplied from the lighting control means 3 to the discharge lamp 6 or a signal corresponding to these.
It is provided in order to obtain the voltage value and the current value detected inside, and the detection result is sent to the power control means 5.

The power control means 5 has a light emission promotion control means 7, a shift control means 8 and a constant power control means 9 as its control functions as shown in the figure. It should be noted that these control means are not necessarily provided as separate circuits, and that the functional control divisions of the power control means 5 are merely configured as shown when visualized by block elements. Be careful.

The light emission promotion control means 7 controls the discharge lamp 6 in the early stage of lighting by supplying electric power exceeding the rated power to the discharge lamp to promote light emission of the discharge lamp and to improve the temporal rise characteristic of the luminous flux. In addition, the constant power control means 9 guarantees stable lighting by performing constant power control at the rated power during steady lighting of the discharge lamp.

The transition control means 8 is in a transitional state from the state in which the discharge lamp 6 is placed under the control of the light emission promotion control means 7 to the state in which the discharge lamp 6 is placed under the control of the constant power control means 9. It is in charge of power control and gradually reduces the power supplied to the discharge lamp 6 with the passage of time, and therefore has a plurality of time constant circuits.

In FIG. 2, the horizontal axis represents time t, and the vertical axis represents a power control signal (hereinafter, "W") for controlling the power supplied to the discharge lamp 6.
P ". ) And the detection signal of the lamp voltage of the discharge lamp 6 (this is referred to as “VS”), and the signal change at the cold start of the discharge lamp is shown.

As shown in the figure, during the period t1 when the discharge lamp 6 is under the control of the light emission promotion control means 7, the power supplied to the discharge lamp is large, and during the period t2 when the transition control means 8 is under the control of the power supply. After gradually decreasing with the passage of
In the period t3 under the control of the constant power control means 9, the control value reaches the control value indicating the rated power (this is referred to as "WPc") and the control is stabilized. The detection signal VS shows a relatively low value at the beginning of the period t1 and gradually increases as time elapses and then gradually approaches a steady value. Also, the period t2
Since the electric power supplied to the discharge lamp in is larger than the electric power supplied to the discharge lamp in the period t3, the periods t1 and t2
It can be considered that it is a period for promoting light emission of the discharge lamp, including, and t2 can be considered to be the latter period of the period.

In FIG. 3, the horizontal axis represents time t, and the vertical axis represents the power control signal WP and the lamp voltage detection signal VS, showing the signal change at the hot start of the discharge lamp.

As shown in the drawing, in this case, the excessive power supply to the discharge lamp by the light emission promotion control means 7 is performed for a short time or is not performed for a short time, and the discharge lamp 6 is immediately operated by the transition control means 8. Under control, the power control signal WP gradually decreases from a value slightly larger than the control value WPc over time, and then reaches WPc to stabilize the control. The lamp voltage detection signal VS immediately increases from a relatively high value to a steady value.

By the way, it is conceivable to use one time constant circuit to define the time change rate of the power supply by the shift control means 8. In this case, the discharge lamp is controlled from the light emission promotion control means 7 by the shift control. From the time of shifting to the means 8, the power control signal WP gradually decreases with a certain time constant with the lapse of time, and finally reaches WPc.

However, it is difficult to set one time constant so as to obtain a good rising characteristic of the luminous flux during the cold start, the hot start, or the lighting start in an intermediate state between them. Is.

FIG. 4 shows an example of the change over time of the luminous flux of the discharge lamp (which will be referred to as "L"). When a set value with a time constant is adopted, the graph curve gc is exaggerated. In particular, a large undershoot may occur in the light flux L at the cold start, or a large overshoot may occur in the light flux L at the hot start as exaggeratedly shown in the graph curve gh.

Therefore, it is conceivable to adopt a circuit configuration in which the state when the discharge lamp is turned on is detected and the reduction rate of the supplied power by the transition control means 8 is changed according to the detection result. The inevitability of complexity.

In the present invention, the period t by the shift control means 8 is
By appropriately changing the reduction rate of the supplied power in No. 2 with time, appropriate power is supplied to the discharge lamp. That is, the shift control means 8 according to the present invention, for example, as shown in FIG. 5, includes a plurality of time constant circuits 10a having different time constants,
10b, ..., and configured such that during the transition period t2, the time constants corresponding to the reduction rate of the supplied power change by sequentially operating these time constant circuits as the supplied power decreases. To be done.

For example, assuming a case where the transition period t2 is divided into two periods, the time constant is defined to be a small value in the first period to reduce overshoot at the hot start, and the time constant is set to a large value in the latter period. It is possible to set a time constant such that the undershoot at the cold start is reduced by regulation, and more generally, the transition period t2 is set to a plurality of periods (the lengths of the periods are not necessarily equal). When the time constant value in each period can be set separately for each period, and the discharge lamp is lit from an intermediate state between cold start and hot start depending on the combination of such time constants. Also, it becomes possible to properly control the reduction rate of the supplied power during the transition period. Instead of providing a plurality of time constant circuits having different time constants, the transition control means 8 can be configured by a time constant circuit having an order of 2 or more.

However, when the design of the transfer control means 8 is changed, only the addition of a time constant circuit or the increase of the order (for example, the primary time constant circuit has a secondary structure) is sufficient. Therefore, this does not significantly complicate the circuit configuration.

In generating the power control signal WP as shown in FIGS. 2 and 3, the time constant circuit has the following configuration.
A configuration using only passive elements (resistors and capacitors),
A configuration of an integrating circuit using a passive element and an active element can be used, but the former is in line with the gist of the present invention in that the circuit configuration is simplified.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 6 to 9 show an example of implementation of the present invention.

In the lighting circuit 11 shown in FIG. 6, the battery 12 corresponding to the power source 2 has input terminals 13 and 13 '.
And a lighting switch 14 is provided on one side of the power supply line.

The battery voltage is supplied to the DC power supply circuit 15, where it is stepped up and / or stepped down.

The DC-AC conversion circuit 16 is a DC power supply circuit 1
The DC output voltage of 5 is converted into an AC voltage. For example, a bridge type circuit including a plurality of pairs of semiconductor switch elements arranged on a power supply path to a discharge lamp and a configuration including a drive control circuit thereof are provided. Although it can be used, any structure for converting a DC voltage into a sine wave voltage, a rectangular wave voltage or the like can be used for the DC-AC conversion circuit 16.

The igniter circuit 17 arranged at the subsequent stage of the DC-AC conversion circuit 16 generates a starting pulse for the discharge lamp 18 and superimposes this on the output of the DC-AC conversion circuit 16, and then the AC output terminal 19 And 19 'is a circuit for applying to the discharge lamp 18 connected between.

DC power supply circuit 15 and DC-AC conversion circuit 1
A detecting means for detecting the output voltage and the output current of the DC power supply circuit 15 is provided between the output terminal 6 and the DC power supply circuit 6, and the output voltage of the DC power supply circuit 15 (hereinafter referred to as “Vdc”) is the resistor 20. , 20 'are detected as partial pressure values. Also,
The current detection resistor 21 for detecting the output current of the DC power supply circuit 15 includes the DC power supply circuit 15 and the DC-AC conversion circuit 1.
It is arranged on one of the connection lines that connect with 6.

The detection signals from the resistors 20 and 20 'and the current detection resistor 21 are sent to the control circuit 22 and the control circuit 2
2 generates a power control signal corresponding to these detection signals and sends it to the DC power supply circuit 15 to control its output voltage. For example, at the cold start of the discharge lamp 18, after supplying electric power exceeding its rated power to promote light emission, the electric power supplied to the discharge lamp 18 is reduced at a reduction rate defined by a time constant circuit to perform constant power control. And a control for stably lighting the discharge lamp 18 by constant power control.

The control circuit 22 realizes the function of the power control means 5 and includes a light emission promotion control circuit, a constant power control circuit, and a shift control circuit. The shift control circuit uses a capacitor and a resistor. It is composed of a time constant circuit. The light emission promotion control circuit may be configured, for example, to detect the output current of the DC power supply circuit 15 and control the value of the power supplied to the discharge lamp 18 according to the level of the output current. By controlling the levels of the respective detection signals related to the output voltage and the output current of the DC power supply circuit 15 to be constant at a certain ratio, a control line obtained by linear approximation to the constant power curve can be obtained. A configuration for performing power control according to the above can be mentioned, but the description thereof will be omitted because the configuration does not matter.

FIG. 7 shows a configuration example 23 of the main part of the control circuit 22. The detection voltage relating to the output voltage Vdc of the DC power supply circuit 15 (that is, the voltage division by the resistors 20 and 20 ').
Is input to the inverting input terminal of the operational amplifier 25 through the resistor 24, and a predetermined reference voltage (referred to as “E1”) indicated by the constant voltage power supply 26 is supplied to the non-inverting input terminal. A resistor 27 is inserted between the inverting input terminal and the output terminal of the operational amplifier 25.

The operational amplifier 28 and the diode 29 form a buffer 30, and the non-inverting input terminal of the operational amplifier 28 is connected to the output terminal of the operational amplifier 25. The output terminal of the operational amplifier 28 is connected to the anode of the diode 29, and the cathode of the diode 29 is connected to the non-inverting input terminal of the operational amplifier 28 and the output terminal 31.

The shift control circuit 22a is provided in parallel with the buffer 30, one end of the capacitor 32 is connected to the output terminal 31, and the other end is a constant voltage source 33 (the voltage value of which is "E2"). )It is connected to the. A series circuit of a resistor 34 and a capacitor 35 is provided in parallel with the capacitor 32, and a resistor 36 is connected to them.
Are connected in parallel, and a resistor 3 is connected to the resistor 36.
7 and Zener diode 38 are connected in parallel. The capacitance of the capacitor 35 is set to a value smaller than that of the capacitor 32.

The signal obtained from the output terminal 31 corresponds to a part of the above-mentioned power control signal WP, and the signal is required to be processed directly or for control (for example, in the case of the control using the pulse width modulation, the duty is controlled). After being converted into a cycle, etc.), it is sent to the DC power supply circuit 15.

Therefore, in the above-mentioned circuit 23,
Since the power control signal can be easily obtained by adding the output of the transition control circuit 22a to the signal obtained by inverting and amplifying the detection signal of Vdc corresponding to the lamp voltage of the discharge lamp 18 by the operational amplifier 25, the circuit configuration is obtained. Will be easier.

FIG. 8 shows an example of the change in luminous flux at cold start, where the horizontal axis represents time t and the vertical axis represents the luminous flux L of the discharge lamp 18. Note that the period “ta” indicates the initial stage of the rising of the light flux L, the period “tb” indicates the first period of the transition period following the period ta, the period “tc” indicates the second period of the transition period following the period tb, and the period “td” is released. The steady lighting period of the electric lamp 18 is shown.

In the period ta, since the lamp voltage of the discharge lamp 18 is low, the capacitor 32 of the transition control circuit 22a is rapidly charged and the luminous flux L rises quickly. Then, in the period tb, the capacitor 32 is discharged through the resistor 36, and the capacitor 35 is charged through the resistor 34. Therefore, the resistance values of these resistors and the capacitors 32, 3
Discharge lamp 1 according to the time constant defined by the capacitance of 5
The rate of reduction of the power supplied to 8 is specified.

Then, in the period tc, the capacitor 35 is discharged through the resistors 34 and 36, and the power supplied to the discharge lamp 18 is changed by the time constant defined by the resistance value of these resistors and the electrostatic capacitance of the capacitor 35. The reduction rate of is defined. The undershoot of the light flux L in the period tc (this is exaggerated as “ud” in FIG. 8) is suppressed by delaying the decrease in the power supplied to the discharge lamp 18 by setting this time constant. be able to.

FIG. 9 shows an example of the change in the luminous flux at the time of hot start, with the horizontal axis representing time t and the vertical axis representing the luminous flux L of the discharge lamp 18. The periods ta to td are as described above.

In this case, the period ta is very short, and the luminous flux L rises while fluctuating slightly. Then, during the period tb, the capacitor 32 is discharged through the resistor 36 and the capacitor 35 is charged through the resistor 34, so that the time constants defined by the resistance values of these resistors and the electrostatic capacitances of the capacitors 32, 35. Defines the reduction rate of the power supplied to the discharge lamp 18. It should be noted that the overshoot of the light flux L in the period tb (this is exaggerated and shown as “ov” in FIG. 9) is suppressed by accelerating the decrease in the power supplied to the discharge lamp 18 by setting this time constant. be able to.

Then, during the period tc, the capacitor 35 is discharged through the resistors 34 and 36, and the power supplied to the discharge lamp 18 is changed by the time constant defined by the resistance value of these resistors and the capacitance of the capacitor 35. The reduction rate of is defined.

When the discharge lamp is lit in an intermediate state between cold start and hot start, the lengths of the periods ta, tb, tc and the rising condition of the luminous flux L are different.

In this embodiment, the output of the transition control circuit 22a is added to the circuits (20, 20 ', 24 to 27) related to the detection of the lamp voltage, but the present invention is not limited to this. It is possible to employ a configuration in which the output of the transition control circuit 22a is added to the circuit related to detection of. Further, in the configuration of the transition control circuit 22a, a time constant circuit is formed by connecting a plurality of capacitors (32, 35) in parallel (this makes it possible to use a capacitor having a small capacitance, thereby reducing cost and downsizing). However, various embodiments such as connecting a plurality of capacitors in series or replacing the Zener diode 38 with a diode are possible.

[0053]

As is apparent from the above description, according to the first aspect of the present invention, the decrease rate of the electric power supplied to the discharge lamp is temporally changed by the transition control means by combining a plurality of time constants. Since it can be changed, it is not necessary to separately control the power supplied to the discharge lamp by determining the lighting state of the discharge lamp, and it is possible to significantly change the luminous flux of the discharge lamp by adding a time constant circuit or changing the order. By performing electric power control so as not to cause overshoot or undershoot, it is possible to shorten the starting time or the restart time of the discharge lamp.

According to the second aspect of the invention, the discharge lamp is switched to the constant power control of the discharge lamp from the state in which the electric power exceeding the rated power is supplied to the discharge lamp in the first period and the second period. It is possible to easily control the rising characteristics of the luminous flux of the discharge lamp by changing the reduction rate of the supplied power.

According to the third aspect of the invention, the circuit configuration can be simplified by forming the time constant circuit by connecting a plurality of series circuits in parallel by capacitors and / or resistors.

According to the fourth aspect of the invention, the output of the transition control means is added to the output of the lamp voltage / current detection means for obtaining the lamp voltage and / or lamp current of the discharge lamp or a signal corresponding to them. By doing so, the power control signal of the discharge lamp can be easily obtained.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an outline of a configuration of a discharge lamp lighting circuit of the present invention.

FIG. 2 is a diagram for explaining a temporal change of a power control signal at a cold start.

FIG. 3 is a diagram for explaining a temporal change of a power control signal at the time of hot start.

FIG. 4 is a diagram for explaining a change in luminous flux of a discharge lamp and a rising characteristic thereof.

FIG. 5 is a diagram showing a configuration of a shift control unit.

FIG. 6 is a circuit block diagram showing an example of an embodiment of the present invention together with FIG. 7 to FIG. 9 and showing an outline of a lighting circuit.

FIG. 7 is a circuit diagram showing a configuration example of a main part of a control circuit.

FIG. 8 is a diagram showing an example of a change in luminous flux of a discharge lamp at a cold start.

FIG. 9 is a diagram showing an example of a change in luminous flux of a discharge lamp during hot start.

[Explanation of symbols]

1 ... Discharge lamp lighting circuit, 4 ... Lamp voltage / current detection means,
5 ... Power control means, 6 ... Discharge lamp, 8 ... Transition control means, 1
0a, 10b ... Time constant circuit

Claims (4)

[Claims] 1. When the discharge lamp is turned on from a cold state, the discharge lamp is supplied with electric power exceeding its rated power and then the electric power supplied to the discharge lamp is reduced.
In a discharge lamp lighting circuit having a power control means for controlling the discharge lamp to shift to the constant power control, in order to shift the discharge lamp to the constant power control after supplying the power exceeding the rated power to the discharge lamp. Of the plurality of time constant circuits having different time constants or their order is 2
A discharge lamp lighting circuit having a time constant circuit of the following or more, wherein the time constant changes with the passage of time, and the reduction rate of the power supplied to the discharge lamp changes accordingly. 2. The discharge lamp lighting circuit according to claim 1, wherein the transition control means has two time constant circuits having different time constants or two.
It has the following time constant circuit, and the reduction rate of the power supplied to the discharge lamp in the first half of the transition period of the discharge lamp to the steady state is regulated by the setting of the first time constant, and in the latter half of the transition period. A discharge lamp lighting circuit, wherein a reduction rate of power supplied to the discharge lamp is regulated by setting a second time constant. 3. The discharge lamp lighting circuit according to claim 1 or 2, wherein the time constant circuit has a configuration in which a plurality of series circuits using capacitors and / or resistors are connected in parallel with each other. Characteristic discharge lamp lighting circuit. 4. The discharge lamp lighting circuit according to claim 1, claim 2 or claim 3, wherein a lamp voltage / current detecting means for obtaining a lamp voltage and / or a lamp current of the discharge lamp or a signal corresponding thereto. And a power control signal for the discharge lamp is generated by adding the output of the transition control means to the output of the discharge lamp lighting circuit.