JPH0992474A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the end of the life of a discharge lamp and to announce it at the end of the life before the discharge lamp turns off. SOLUTION: For the lamp voltage of a discharge lamp La, an allowable range specified by an upper limit value Up and a lower limit value Lw is set, and when the voltage deviates from the allowable range, a display device 3 announces the possibility that the lamp may come to its end. When the state in which the voltage deviates from the allowable range has continued for a certain time or more that is set by a timer 27, the discharge lamp La is turned off and the end of its life is announced by means of the display device 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a discharge lamp lighting device for lighting a high pressure discharge lamp.

[0002]

2. Description of the Related Art In general, discharge lamps have higher efficiency than incandescent lamps, and therefore attempts have been made to replace conventional halogen lamps with discharge lamps for vehicle headlights powered by batteries. For this type of discharge lamp, the use of a high pressure discharge lamp such as a metal halide lamp is being considered.

By the way, in a general discharge lamp lighting device,
As shown in FIG. 6, the lamp voltage during steady lighting of the discharge lamp La is detected by the voltage detection unit 11 provided in the lighting circuit 1,
By controlling the lighting circuit 1 by the control circuit 2 so as to supply a lamp current having a magnitude corresponding to the lamp voltage, the emission brightness is kept substantially constant. Further, in this type of discharge lamp lighting device, when the lamp voltage decreases, the lamp current increases, so that the arc tube may explode due to overcurrent.
Therefore, an upper limit value is set for the lamp current, and the discharge lamp La is controlled to be turned off when the lamp current detected by the current detection unit 12 reaches the upper limit value. That is,
When the lamp current reaches the upper limit, the discharge lamp is turned off immediately.

[0004]

On the other hand, in a high pressure discharge lamp such as a metal halide lamp, the electrode material evaporates and scatters when the lamp is lit for a long time to increase the lamp voltage, and as a light emitting material, an alkali metal such as sodium is used. When using the halide of, the alkali metal diffuses in the quartz glass forming the arc tube and disappears outside the arc tube (so-called slow leak phenomenon) due to long-time lighting,
In this case, it is known that the lamp voltage drops.

In the above-described general discharge lamp lighting device, the discharge lamp La is operated when the lamp current rises as the lamp voltage drops.
Is only turned off immediately, and the present situation is that there is no function for detecting and notifying the end of life of the discharge lamp La and for turning off the discharge lamp La. In particular, when it is used for a vehicle headlight or the like, it is dangerous to suddenly turn off without notice, so it is required to detect the end of life of the discharge lamp La and give a notice before turning off.

The present invention has been made in view of the above circumstances, and an object thereof is to detect the end of life of a discharge lamp and to give advance notice at the end of the life before the discharge lamp is turned off. To provide a device.

[0007]

According to a first aspect of the invention, the lamp voltage detected by the voltage detecting section is compared with preset upper and lower limits of an allowable range to generate an output according to a magnitude relationship. If it is determined that the lamp voltage has deviated from the allowable range based on the output of the comparator and the comparator, the alarm device is driven to give advance notice of the life, and the lamp voltage deviates from the allowable range for a certain period of time. A determination unit that controls the lighting circuit is provided so that the discharge lamp is turned off when continued.

With this configuration, it is estimated whether the discharge lamp is at the end of its life based on the fluctuation of the lamp voltage, and if it is estimated that the end of the life is reached, a warning is given to the user to warn the user. If the state in which the lamp voltage deviates from the allowable range continues for a certain period of time, it is possible to determine that the end of life has been reached and turn off the discharge lamp. By giving advance notice in this way, it is possible to suggest to the user the possibility of turning off the discharge lamp at the end of its life, and the discharge lamp will not be turned off due to temporary fluctuations in the lamp voltage. Even when it is used for a headlamp for a vehicle, it is possible to avoid the danger caused by sudden turning off.

According to a second aspect of the invention, instead of the comparator in the configuration of the first aspect of the invention, a difference device for obtaining the absolute value of the difference between the lamp voltage and the upper limit value and the lower limit value of the preset allowable range. Is used. With this configuration, the end of life of the discharge lamp can be notified in advance as in the first aspect of the invention, and the difference value is used to determine the magnitude and rate of change of the difference value rather than the two-step control based on the magnitude relationship. Based on this, it becomes possible to finely control the power supplied to the discharge lamp.

According to the third aspect of the invention, the variation width is obtained by sampling the lamp voltage at regular time intervals immediately after the discharge lamp is started and sequentially obtaining the variation width obtained by subtracting the first sampling value detected immediately after the startup from the subsequent sampling values. Based on the output of the calculation unit, the change width calculated by the calculation unit, the comparator that generates the output according to the magnitude relation by comparing the upper limit value and the lower limit value of the preset allowable range When it is determined that the change width deviates from the permissible range, the notification device is driven to give advance notice of the life, and the discharge lamp is turned off when the change width deviates from the permissible range and continues for a certain period of time. And a determination unit that controls the lighting circuit.

With this configuration as well, the end of life of the discharge lamp can be notified in advance as in the first aspect of the invention, and the difference in lamp voltage is used not in the lamp voltage itself in the comparator and the judging section. Can reduce the value to be processed. That is, the number of bits of data can be reduced when performing digital calculation. In particular, when the history of changes in the lamp voltage is stored, the storage capacity can be reduced by reducing the number of data bits.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In this embodiment, as shown in FIG. 1, a lighting circuit 1 for supplying electric power to a discharge lamp La is provided, and this lighting circuit 1 is a start control for lighting the discharge lamp La by a control signal from the outside. The control of the lamp current during steady lighting and the control of turning off the discharge lamp La are possible. Here, the lighting circuit 1 is an inverter circuit, which converts a DC power supply DC such as a car battery into AC power and supplies the AC power to the discharge lamp La. Further, the lighting circuit 1 controls the energization period to the discharge lamp La by changing the on-duty of the switching element that constitutes the inverter circuit, or provides a resonance circuit in the power supply path to the discharge lamp La to provide the switching element. The lamp current of the discharge lamp La is controlled by changing the switching frequency of the lamp. The lighting circuit 1 is provided with a voltage detector 11 for detecting a lamp voltage, and the lamp voltage detected by the voltage detector 11 is input to the control circuit 2. The control circuit 2 is configured using a microcomputer, and the voltage detection unit 1
A control signal for controlling the lighting circuit 1 is generated based on the lamp voltage input from the control circuit 1. Here, similarly to the conventional discharge lamp lighting device, the control circuit 2 has a function of keeping the light emission luminance substantially constant by controlling the lamp current according to the lamp voltage, but this function is well known. Therefore, it is omitted in the configuration shown in FIG. Further, the microcomputer is a portion surrounded by a dashed line in FIG.

The control circuit 2 includes an A / D converter 21 for converting a ramp voltage input as an analog value into a digital value, and the A / D converter 21 samples the ramp voltage at regular time intervals. This sampling period is a counter 22 that counts clock signals inside the microcomputer.
Stipulated by The output value of the A / D converter 21 is
The comparators 23 and 24 respectively compare the upper limit value Up and the lower limit value Lw set in advance. That is, it is compared whether or not the lamp voltage is within the allowable range set by the upper limit value Up and the lower limit value Lw. This comparison is performed within the time between the sampling value being obtained and the next sampling value being obtained. here,
When the output value of the A / D converter 21 exceeds the upper limit value Up or falls below the lower limit value Lw, the determination unit 25 estimates that there is a possibility of the end of life, drives the notification device 3 through the output port 26, and releases it. The life of the electric lamp La is notified in advance. The notification device 3 may be either a visual notification device using a light emitting diode or a liquid crystal display device, or an acoustic notification device using a buzzer or a voice synthesizer, both of which are used at the same time. You may do it. In addition, the determination unit 25
When the possibility of the end of life is detected by the timer 27, the timer 27 starts a timed operation, and when the output value of the A / D converter 21 continues to exceed the above allowable range until the end of the timed operation of the timer 27, the output is output. Through the port 26, the lighting circuit 1 is instructed to turn off the discharge lamp La, and at the same time, the notification device 3 is driven so as to give a notification prompting replacement of the discharge lamp La.

The operation of the control circuit 2 described above will be described with reference to FIG. When the power is turned on, first the above timer 27
It is determined whether or not the timed operation has been completed (S1).
Next, the lamp voltage is sampled from the voltage detector 11 (S2) and converted into a digital value by the A / D converter 21 (S3). The output value of the A / D converter 21 is the comparator 23,
24 is compared with the upper limit value Up and the lower limit value Lw (S
4, S5), if the output value of the A / D converter 21 deviates from the allowable range defined by the upper limit value Up and the lower limit value Lw, the timer 27 starts the timed operation (S6), and the alarm device 3 is driven (S7). If the output value of the A / D converter 21 is between the upper limit value Up and the lower limit value Lw, the timer 27 is reset (S8) and the notification device 3 is stopped (S9). This process is performed every time the lamp voltage is taken in. When the end of the timed operation of the timer 27 is detected in step S1, the discharge lamp La is turned off (S10).

By the above processing, when the lamp voltage deviates from the allowable range between the upper limit value Up and the lower limit value Lw, only the notification device 3 is driven and the discharge lamp La is not extinguished and only the advance notification is given. When the lamp voltage deviates from the allowable range for a certain period of time set by the timer 27, the discharge lamp La is turned off. That is, the discharge lamp La does not immediately turn off in response to a temporary change in the lamp voltage, but it is possible to notify the user of the possibility of the end of life by giving a notice in advance. As a result, it is possible to predict that the discharge lamp La will be turned off when a warning is issued by the notification device 3, and it is possible to avoid the danger of suddenly turning off the lamp.

Since the control circuit 2 is configured by using the microcomputer as described above, the circuit configuration is simpler than that when the control circuit 2 is configured by using individual parts, and the control circuit is also provided. Since the operation of No. 2 can be defined by software, more complicated and finer control can be performed as compared with the case of using individual parts. (Embodiment 2) In this embodiment, as shown in FIG. 3, a difference unit 3 is used instead of the comparators 23 and 24 in the first embodiment.
1, 32 are provided.

That is, the lamp voltage is supplied to the A / D converter 21.
Is sampled at a constant time interval and converted into a digital value, and the absolute value of the difference between the upper limit value Up and the lower limit value Lw of the lamp voltage is obtained by the differentiators 31 and 32.
The absolute value of the difference obtained by the differentiators 31 and 32 is the determination unit 2
5, it is determined whether or not the lamp voltage is within the allowable range between the upper limit value Up and the lower limit value Lw based on the output values of the both differencers 31 and 32, and it is notified that the lamp voltage deviates from this range. The device 3 is driven. Specifically, if the output value of one of the differencers 31 and 32 is larger than the difference between the upper limit value Up and the lower limit value Lw, the notification device 3 is driven via the output port 26, and this state is maintained for a certain time. If it continues, the lighting circuit 1 is instructed to turn off the discharge lamp La. Other configurations and operations are the same as those of the first embodiment.

Since the difference is used in this embodiment, the input value to the determination unit 25 is not binary but reflects the temporal change of the lamp voltage with the accuracy of the resolution of the A / D converter 21. become. Therefore, by using this data, it is possible to control the lamp current of the lighting circuit 1, so that it is possible to share a part of the configuration with respect to the control of the lamp current during steady lighting and the control for the end of life. .

(Embodiment 3) In the present embodiment, as shown in FIG. 4, the output of the A / D converter 21 in the control circuit 2 is not directly compared by the comparators 23 and 24, but the A / D converter is compared.
With respect to the output of the converter 21, the sampling value of the lamp voltage immediately after the start of the discharge lamp La is used as a reference, and the sampling value obtained first is subtracted from the sampling value obtained thereafter to obtain the variation range of the lamp voltage. The change width is compared by the comparators 23 and 24 with the upper limit value ΔUp of the change width.
And the lower limit value ΔLw. For this reason, in the present embodiment, the change width calculation unit 28 that obtains the change width from the output of the A / D converter 21 is provided. In addition, the change width is stored in the storage unit 4 each time the change width is obtained, and the change width is stored in time series in the storage unit 4.

By the way, the control circuit 2 also includes a life estimation unit 29 for estimating the life of the discharge lamp La by using the data stored in the storage unit 4. In this way, since the life estimation unit 29 uses the data stored in the storage unit 4, the control circuit 2 can input / output not only data but also input / output port 2
6'is provided. Here, the storage unit 4 may be a RAM, but the EEP is used to leave data in preparation for the next lighting.
It is desirable to use a ROM that can hold data without power supply. Further, since the data from the lighting of the discharge lamp La to the extinction of the discharge lamp La is stored in the storage unit 4, the capacity of the storage unit 4 is set according to the life of the discharge lamp La and the sampling cycle of the lamp voltage.

The change width calculation unit 28 has a register for holding the output of the A / D converter 21 immediately after the start of lighting of the discharge lamp La, and the output value of the A / D converter 21 for each subsequent sampling is transferred to the register. It is realized by subtracting the held value. Whether or not the discharge lamp La has been turned on can be detected by monitoring the lamp voltage. Moreover, you may use what detects the optical output of the discharge lamp La with a photoelectric element.

The basic operation is similar to that of the first embodiment,
The output value of the change width calculation unit 28 is compared with the upper limit value ΔUp and the lower limit value ΔLw set in advance in the comparators 23 and 24, and the change width output from the change width calculation unit 28 exceeds the upper limit value ΔUp. If the lower limit value ΔLw is exceeded, the determination unit 25 estimates that the end of life is reached,
The notification device 3 is driven through the input / output port 26 '. Further, at this time, the timed operation by the timer 27 is started, and if the state in which the change width deviates from the range between the upper limit value ΔUp and the lower limit value ΔLw continues until the end of the timed operation of the timer 27, the discharge lamp La. The lighting circuit 1 is controlled to turn off.

The operation at the next lighting is also the above-mentioned operation repeated, but the input / output port 26 'is started before the discharge lamp La is started.
The value stored in the storage unit 4 is read by the determination unit 25 via the, and if the value stored in the storage unit 4 is the end-of-life value, the notification device 3 does not start the discharge lamp La. A notification is issued to prompt replacement of the electric light La. If the value stored in the storage unit 4 is not the value at the end of life, the above operation is repeated.

Next, the operation of the control circuit 2 will be described with reference to FIG. When the power is turned on, it is first determined whether or not the timed operation of the timer 27 has ended (S1). next,
The lamp voltage is sampled from the voltage detector 11 (S
2) The A / D converter 21 converts the digital value (S3). Here, when the discharge lamp La is started, the value immediately after that is stored in the change width calculation unit 28, and each time a subsequent sampling value is obtained, the difference from the value immediately after start is obtained as the change width of the lamp voltage ( S4) (in FIG. 5, the process immediately after the start is omitted and only the process during steady lighting is described). The obtained change width is compared with the upper limit value ΔUp and the lower limit value ΔLw by the comparators 23 and 24 (S5, S6), and if the change width deviates from the range between the upper limit value ΔUp and the lower limit value ΔLw,
After the change width is stored in the storage unit 4 (S7), the timer 27 starts the timed operation (S8) and drives the notification device 3 (S).
9). If the change width is in the range between the upper limit value ΔUp and the lower limit value ΔLw, the change width is stored in the storage unit 4 (S10), the timer 27 is reset (S11), and the notification device 3 is also stopped (S12). This process is performed every time the lamp voltage is taken in. When the end of the timed operation of the timer 27 is detected in step S1, the discharge lamp La is turned off (S1).
3).

By the way, since the difference between the lamp voltage immediately after the start of lighting and the lamp voltage sampled during the lighting is stored in the storage unit 4 in time series, the change with time of the discharge lamp La is known from this data. The life estimation unit 29 estimates the life of the discharge lamp La using the data stored in the storage unit 4. By additionally providing such an estimation function and displaying the relationship between the estimated life and the usage time on the notification device 3, it is possible to further facilitate the notification of the life of the discharge lamp La to the user. .

Further, since the storage unit 4 does not store the lamp voltage but the difference between the lamp voltage and the initial value of the lamp voltage, the value stored in the storage unit 4 stores the lamp voltage. Compared to, the value becomes smaller, and the number of bits decreases when treated as a digital value. That is, it is possible to use a storage unit 4 having a relatively small capacity as the storage unit 4 for storing the time series data.

[0027]

According to the first aspect of the present invention, there is provided a comparator for comparing the lamp voltage detected by the voltage detecting section with the upper limit value and the lower limit value of a preset allowable range and generating an output according to the magnitude relationship. When it is determined that the lamp voltage deviates from the above allowable range based on the output of the comparator, the alarm device is driven to give advance notification of the life, and if the lamp voltage deviates from the above allowable range for a certain period of time, the discharge lamp It is equipped with a judgment unit that controls the lighting circuit to turn off the lamp, and based on the fluctuation of the lamp voltage, it estimates whether the discharge lamp is at the end of its life. By alerting the user by issuing a notification, if the lamp voltage deviates from the allowable range for a certain period of time, it can be judged that the end of the life has been reached and the discharge lamp can be turned off. It is possible to notify the user of the possibility of extinguishing the discharge lamp at the end of the life of the discharge lamp by giving a notice, and because the discharge lamp is not extinguished due to temporary fluctuations in the lamp voltage, Even when used as a headlamp for a vehicle, there is an advantage that the danger due to sudden turning off can be avoided.

According to a second aspect of the present invention, instead of the comparator in the configuration of the first aspect of the present invention, a difference device for obtaining an absolute value of a difference between a lamp voltage and an upper limit value and a lower limit value of a preset allowable range is provided. Since it is used, it is possible to give advance notice of the end of life of the discharge lamp as in claim 1, and
By using the difference value, there is an advantage that it is possible to finely control the power supplied to the discharge lamp based on the magnitude and rate of change of the difference value, rather than the two-step control based on the magnitude relationship.

According to a third aspect of the present invention, the variation width is obtained by sampling the lamp voltage at regular time intervals immediately after starting the discharge lamp and sequentially obtaining the variation width obtained by subtracting the first sampling value detected immediately after the starting from the subsequent sampling values. Based on the output of the calculation unit, the change width calculated by the calculation unit, the comparator that generates the output according to the magnitude relation by comparing the upper limit value and the lower limit value of the preset allowable range When it is determined that the change width deviates from the permissible range, the notification device is driven to give advance notice of the life, and the discharge lamp is turned off when the change width deviates from the permissible range and continues for a certain period of time. A judgment section for controlling the lighting circuit is provided, so that the end of life of the discharge lamp can be notified in advance as in the case of the invention of claim 1, and the comparator and the judgment section can be used as a warning. Rather than flop voltage itself, by uses the difference between the ramp voltage, there is an advantage that it is possible to reduce the value to be processed. This leads to a reduction in the number of data bits when performing a digital operation, and particularly when a history of changes in the lamp voltage is stored, the number of data bits is reduced to reduce the storage capacity. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is a block diagram showing a second embodiment.

FIG. 4 is a block diagram showing a third embodiment.

FIG. 5 is an operation explanatory diagram of the third embodiment.

FIG. 6 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 Lighting Circuit 2 Control Circuit 3 Notification Device 4 Memory Section 11 Voltage Detection Section 21 A / D Converter 22 Counter 23 Comparator 24 Comparator 25 Judgment Section 26 Output Port 26 'Input / Output Port 27 Timer 28 Change Width Calculation Section 29 Life Estimator 31 Differencer 32 Differencer

Claims (3)

[Claims] 1. A lighting circuit comprising a power supply unit for supplying electric power necessary for lighting a discharge lamp and a voltage detection unit for detecting a lamp voltage, and a life of the discharge lamp based on the lamp voltage detected by the voltage detection unit. A control circuit for detecting and a notification device for notifying that the life of the discharge lamp has been detected by the control circuit, and the control circuit sets the lamp voltage detected by the voltage detection unit to the upper limit of the allowable range set in advance. And a comparator that generates an output according to the magnitude relationship with the lower limit value, and if it is determined that the lamp voltage has deviated from the above allowable range based on the output of the comparator, the warning device is driven to give a warning of the life. A discharge lamp lighting device, comprising: a determination unit that controls a lighting circuit to turn off the discharge lamp when the lamp voltage deviates from the allowable range and continues for a certain period of time. 2. A lighting circuit provided with a power supply unit for supplying electric power required for lighting the discharge lamp and a voltage detection unit for detecting the lamp voltage, and the life of the discharge lamp based on the lamp voltage detected by the voltage detection unit. A control circuit for detecting, and a notification device for notifying that the life of the discharge lamp has been detected by the control circuit, the control circuit, the lamp voltage detected by the voltage detection unit and the upper limit of the preset allowable range And a difference device that obtains the absolute value of the difference between the lower limit value and the lower limit value, and if it is determined that the lamp voltage has deviated from the above allowable range based on the output of the difference device, the notification device is driven to give advance notification of the life,
A discharge lamp lighting device, comprising: a determination unit that controls a lighting circuit to turn off the discharge lamp when the lamp voltage deviates from the allowable range and continues for a certain period of time. 3. A lighting circuit having a power supply unit for supplying electric power necessary for lighting the discharge lamp and a voltage detection unit for detecting the lamp voltage, and starting and starting the discharge lamp based on the lamp voltage detected by the voltage detection unit. A control circuit that detects the life of the discharge lamp and a notification device that notifies that the life of the discharge lamp has been detected by the control circuit are provided, and the control circuit detects the lamp voltage detected by the voltage detection unit immediately after the start of the discharge lamp. Is sampled at regular intervals, and the change width calculation unit that sequentially obtains the change width by subtracting the first sampling value detected immediately after the start from the subsequent sampling values and the change width calculated by the change width calculation unit are set in advance. A comparator that generates an output according to the magnitude relationship by comparing it with the upper limit value and lower limit value of a certain allowable range, and the change range deviates from the allowable range based on the output of the comparator. When it is determined that the warning device is driven, a warning of the service life is given, and a determination unit that controls the lighting circuit to turn off the discharge lamp when the change width deviates from the allowable range and continues for a certain period of time is provided. Discharge lamp lighting device characterized by.