JP2003338393A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To normally perform optimal starting control for a discharge lamp and appropriately perform start-up control even for a discharge lamp with a low lamp voltage without filling of mercury, in a discharge lamp lighting device for lighting headlamps of an automobile. <P>SOLUTION: Direct current input voltage from a direct current electric power source 1 is increased at a DC/DC converter section 2, and it is converted into alternating current at a DC/AC inverter section 3 and supplied to the discharge lamp 5. The discharge lamp 5 is started by high-voltage pulse from a starting transformer 4. Lamp voltage of the discharge lamp 5 is controlled by a lamp voltage control circuit 8 on the basis of lamp voltage and lamp current detected by a lamp voltage detecting circuit 6 and a lamp current detecting circuit 7. At that time, detected lamp voltage value is corrected and changed by a lamp voltage correction circuit 9 according to the detected lamp current value, and the lamp voltage is controlled on the basis of the corrected voltage value. <P>COPYRIGHT: (C)2004,JPO

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 device for controlling lamp power by detecting a lamp voltage and a lamp current of a discharge lamp, and more particularly to a discharge lamp lighting device for controlling a rapid rise of a lamp luminous flux. is there.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a circuit configuration of a general discharge lamp lighting device, in which a discharge lamp is a vehicle headlight, and the discharge lamp has several times the rated current when starting. The example of a circuit structure of the lighting device which enables the instantaneous lighting by making a manual current flow is shown.

This type of lighting device receives a direct current voltage (battery voltage) from a direct current power supply 1 as a input, and a DC / DC converter section 2 for boosting the direct current to direct current, and a direct current to alternating current of the boosted direct current. DC / AC inverter unit 3,
It comprises a starting circuit for generating a starting high voltage pulse for starting discharge when the discharge lamp 5 is turned on. Here, the starting circuit is constituted by the starting transformer 4.

The above circuit is for AC lighting, and the DC / AC inverter unit 3 is omitted when the discharge lamp 5 is for DC lighting. Further, in FIG. 5, 6 is a lamp voltage detection circuit, 7 is a lamp current detection circuit, and 8 is a lamp power control circuit.

In the above circuit configuration, the lighting control circuit in the DC / DC converter 2 constituting the DC boosting circuit controls the lamp power from the start of the discharge lamp (discharge lamp) 5 to the stable time, and usually the lamp voltage. The lamp current is controlled accordingly. Further, a protection function is provided for stopping the discharge lamp 5 when an abnormal situation of input voltage, output voltage and current occurs. In order to perform such control operation, a control circuit mainly composed of an analog circuit or a control circuit mainly composed of a microcomputer (microcomputer) is provided.

That is, the control value of the lamp power is obtained as an arithmetic output by these control circuits, and the power supply output control such as PWM is performed on the DC booster circuit based on this to perform the lamp power control. In this way, in the control circuit of the discharge lamp lighting device for automobile lighting, the PWM control unit that detects the lamp voltage and performs the feedback control according to the set value of the required lamp power, and when the input / output abnormality such as the output short-circuit current occurs, It is equipped with a protection circuit that stops the failure.

Further, as a function of the control circuit for instantaneously lighting the discharge lamp of the above discharge lamp lighting device, it is necessary to detect the lamp voltage and the lamp current to control the lamp power.
The lamp voltage of the discharge lamp immediately after starting is as low as about 20 V, and the luminous flux of the lamp is as low as about 10 to 20% as compared with the stable state.
Generally, in a discharge lamp, the lamp voltage and the luminous flux of the lamp rise as the temperature of the lamp arc tube rises. It is necessary to apply double the warm-up current.

The warm-up current causes the temperature of the arc tube to rise rapidly, and the lamp voltage and lamp luminous flux also rise accordingly. The relationship between the lamp voltage and the luminous flux of the lamp at the rise of the luminous flux shows a similar tendency although there is a slight time difference. That is, when the lamp voltage is low, the luminous flux is low, the warm-up current is maximized, and the luminous flux of the lamp also rises as the lamp voltage gradually rises. Therefore, the lamp current is stabilized from warm-up. Implement control to reduce the time.

[0009]

By the way, in the conventional discharge lamp lighting device as described above, when the discharge lamp is instantly lit, a warm-up current equivalent to several times the rated lamp current is applied, but the discharge lamp is discharged. In the instantaneous lighting control of the electric lamp, it is necessary to detect the lamp voltage in order to control the electric power from the starting electric power to the stable electric power.

As a place to detect the lamp voltage,
Rather than directly detecting both ends of the lamp to which a high voltage pulse of about 20 kV is applied at the time of start, the start transformer for generating the high voltage pulse connected in series with the discharge lamp is also detected in a sandwiched manner. Is common. This is because it is difficult to detect the voltage at the location where the starting pulse is directly applied. At that time, an error due to the inductance of the starting transformer may be considered. However, an instantaneous lighting type discharge lamp is generally lit by a low frequency rectangular wave of several hundred Hz, and an impedance error due to the inductance also depends on a DC superposition characteristic. Has a small effect.

However, the effect of the winding resistance due to the warm-up current at the time of starting is large, and if the FET on-resistance of the inverter of the preceding stage, for example, an H-bridge is added, it is 5Ω
When the maximum starting current of 2.6 A is applied, considering that the lamp voltage immediately after starting is 20 V, the error is increased by 13 V, which means that it cannot be accurately detected. This means that the discharge lamp having a lower lamp voltage has a larger current and has a greater influence, and it becomes difficult to optimize the proper starting control by the lamp voltage.

FIG. 6 shows the lamp power according to the lamp voltage and the lamp current from the starting time (lamp power 75 W) to the stable time (lamp power 35 W) of a conventional mercury-filled discharge lamp with a lamp voltage of about 85 V. A control curve is shown, but if the lamp voltage detection value that includes an error with respect to the target power is used for control, the lamp power will be relatively low with respect to the design target lamp power, and the startup will be delayed. Will be needed.

Of course, it is possible to increase the lamp current and the lamp power by adjusting the circuit settings, but since the control is not the same as the initially assumed lamp power control curve but has different characteristics, the rising light flux is stabilized. It takes a lot of time to get it done.

In a recently developed discharge lamp that does not contain harmful mercury, the stable lamp voltage is as low as 40 V, which is about half that of a mercury-encapsulated lamp. In addition, the detected value of the lamp voltage hardly changed between the starting time and the stable time, and the starting power control was very difficult.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a discharge lamp lighting device capable of always performing optimum start control of a discharge lamp.

It is also an object of the present invention to provide a discharge lamp lighting device capable of performing proper start-up control even in a discharge lamp that does not contain mercury, and further capable of preventing the occurrence of abnormalities due to incorrect assembly of the discharge lamp. There is.

[0017]

The discharge lamp lighting device according to the present invention is constructed as follows.

(1) A lamp voltage detection circuit for detecting a lamp voltage of a discharge lamp and a lamp current detection circuit for detecting a lamp current are provided, and a target lamp current or a lamp current based on a detected value of the lamp voltage of the lamp voltage detection circuit or In the process of setting the lamp power and setting the target value, the target value is corrected by the lamp current detection value of the lamp current detection circuit, and the lamp power of the discharge lamp is controlled by the corrected target value. .

(2) In the above (1), a lamp voltage correction circuit is provided for correcting and changing the lamp voltage detection value of the lamp voltage detection circuit according to the lamp current detection value of the lamp current detection circuit. The target lamp current or lamp power is set based on the detected lamp voltage value corrected by the circuit to control the lamp power of the discharge lamp.

(3) In the above (1) or (2),
The lamp voltage correction circuit reduces the correction amount of the lamp voltage detection value with respect to the lamp current detection value by maximizing the correction amount of the lamp voltage at the maximum lamp current at the time of starting the discharge lamp, and then decreasing it as the lamp current decreases. I chose

(4) In any one of (1) to (3) above, the H-bridge transistor inverter for supplying AC power to the discharge lamp and the starting transformer for applying a high voltage pulse to the discharge lamp are provided. The voltage detection circuit outputs a value obtained by adding both the ON voltage of the transistor of the transistor inverter and the winding voltage of the starting transformer to the lamp voltage.

(5) In any one of the above (1) to (3), there is a starting transformer for applying a high voltage pulse to the discharge lamp, and the lamp voltage detecting circuit uses the winding voltage of the starting transformer as the lamp voltage. The added value is output.

(6) In any one of the above (1) to (5), when an abnormal overpower state occurs due to combined lighting of lamp characteristics different from the setting of the lamp power control at the time of starting and stabilizing the discharge lamp, If the lamp voltage becomes higher than a certain set lamp voltage or becomes lower than a certain set lamp current after the elapse of time for the lamp voltage to stabilize immediately after lighting,
The lighting was stopped.

(7) In the above (6), in the lighting device for lighting a discharge lamp that does not contain mercury, when the discharge lamp containing mercury is turned on, it is determined to be abnormal and the lighting is stopped.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a circuit configuration of a discharge lamp lighting device according to the present invention. The same components as those of the circuit of FIG.

In FIG. 1, reference numeral 1 denotes a DC power supply, which is a battery of an automobile here. Reference numeral 2 is a DC / DC converter unit that boosts the DC input voltage, and 3 is a DC / AC inverter unit that converts the boosted DC power into an AC current.
It is configured by an H-bridge transistor inverter using T. 4 is a discharge lamp (vehicle headlight) 5
Is a starting transformer that applies a starting high-voltage pulse at the time of starting.

Further, 6 is a lamp voltage detection circuit for detecting the lamp voltage (tube voltage) of the discharge lamp 5, 7 is a lamp current detection circuit for detecting the lamp current (tube current) of the discharge lamp 5, and 9
Is a lamp voltage correction circuit that corrects and changes the lamp voltage detection value of the lamp voltage detection circuit 6 according to the lamp current detection value of the lamp current detection circuit 7. The lamp power control circuit 8 corrects the lamp voltage after correction by the lamp voltage correction circuit 9. The target lamp current or lamp power is set based on the detected lamp voltage value to control the lamp power of the discharge lamp 5.

The circuit configuration of the above embodiment is provided with the lamp voltage detection circuit 6 and the lamp current detection circuit 7 on the output side of the DC / DC converter which boosts the battery voltage, and sets and detects the target lamp current according to the lamp voltage. In addition to the conventional configuration for controlling the output of the DC / DC converter so that the lamp current value becomes a target value, the lamp voltage is detected for the purpose of eliminating the influence on the lamp voltage detection error due to the increase of the lamp current at the time of starting the discharge lamp 5. A circuit to correct the voltage detection is added. This is because the detected value of the lamp current in the lamp power control circuit 8 is used to cancel the error when the warm-up starting current at the time of starting the lamp increases so as to cancel the error according to the detected value of the lamp starting current. Is to correct.

That is, the lamp current increases and the output side H
When the voltage error due to the FET ON resistance of the bridge and the winding resistance of the starting transformer 4 is large, the actual lamp voltage is calculated by correcting the detected lamp voltage value with the detected lamp current value. . The correction amount is set so that the maximum lamp current at the time of start-up is the maximum, and the lamp current decreases thereafter as the lamp current decreases. Since the lamp current is zero before the start of the discharge lamp 5, the correction amount is also zero. As a result, even if the lamp voltage is detected by the output of the DC / DC converter that sandwiches the H-bridge FET inverter and the starting transformer 4, the lamp voltage at the time of starting can be accurately detected.

This is particularly effective in a discharge lamp that does not contain mercury. That is, if there is an impedance error of, for example, 5Ω between the FET on resistance of the H bridge and the winding resistance of the starting transformer 4 without correction as in the present embodiment, a discharge lamp that does not enclose mercury will have a luminous flux. Since the start-up is slow and requires a starting current of 3.5 A or more,
A lamp voltage error of 17.5V occurs. Moreover, the lamp voltage at the time of starting is about 20V and the lamp voltage at the time of stable is 40
Since it is around V, there is no difference if the variations in the lamp voltage during stabilization are taken into consideration. However, the starting lamp voltage is 3
When stable at 7.5V and 40V, it is impossible to perform appropriate warm-up control based on the lamp voltage change.

Therefore, as in the present embodiment, since the lamp voltage detection error is proportional to the lamp current, if the lamp voltage detection value at the DC / DC converter output is corrected by the lamp current detection value. The true lamp voltage can be easily calculated from the detected lamp voltage value including an error from the start to the stable time. Therefore, it is possible to detect the stable lamp voltage 40V from the start lamp voltage 20V even in a low lamp voltage discharge lamp that does not contain mercury, and it is possible to perform an appropriate warm-up control.

FIG. 2 is a diagram showing the lamp voltage in this embodiment, in which the broken line shows the detection value before correction and the solid line shows the detection value after correction. Further, FIG. 3 is a diagram showing an example of power control of the present embodiment, a solid line shows a target power curve, and a broken line shows correction at a detected value of the lamp voltage at the time of starting (85 W to 95 W).
Shows a power control curve based on the lamp voltage and current when stable (35 W).

Even in the mercury-filled discharge lamps that are already used for automobile headlights, the lamp voltage in the stable state is relatively high at around 85V, but it is the same when starting.
Since it is about 0 V, the error rate is large. This indicates that the start-up power control set in advance according to the lamp voltage causes a deviation and the startup control cannot be properly performed.

That is, the discharge lamp is actually turned on,
It is necessary to perform the work of optimizing the control while adjusting the power control curve so as to instantaneously turn on the lamp voltage detection value including an error. Although the final optimization is possible, the adjustment work is not easy when the overshoot and undershoot of the output light are taken into consideration because the detected value includes an error.

Further, in the D1 type discharge lamp in which the lamp and the starting circuit which are standardized by the European lamp manufacturer are integrated, the lamp voltage can be detected only by the value including the impedance of the starting transformer. Therefore, in a discharge lamp that does not contain mercury, instantaneous lighting becomes difficult unless the control as in this embodiment is performed. When the lamp voltage is directly detected without executing the control of this embodiment, it is necessary to detect the lamp voltage at the lamp end to which 20 kV is applied, which causes problems such as starting pulse voltage attenuation and high breakdown voltage of the detection element.

Although the control circuit configuration of the present embodiment is implemented by an analog circuit, it can be implemented similarly by a circuit using a microcomputer. The correction may be performed by the detection unit before the A / D converter is input, but after the data is loaded into the microcomputer after the A / D converter is input, the calculation for correcting the detection lamp voltage based on the detection lamp current value is performed. Is also good.

Here, in this embodiment, consideration is also given to a protection measure in the case of lighting a discharge lamp containing mercury in a lighting device for lighting a discharge lamp having a low lamp voltage which does not contain mercury.

That is, the lamp voltage of a discharge lamp that does not normally contain mercury is about 35 V to 45 V, and a 35 W lamp is generally used for a vehicle headlight, so the lamp current is 1 A to 0.78 A. The control circuit is 3
Since the vicinity of 5V to 45V is set as the constant power region, when the discharge lamp containing mercury is erroneously turned on, the lamp voltage is about 85V, and there is a risk of overpowering beyond the 35W constant power region. is there.

In this case, the stable lamp voltage is 4
Since it becomes 85 V higher than 0 V, after a certain period of time when the lamp voltage after lighting has stabilized, if it exceeds a certain set lamp voltage, the lamp is stopped to prevent abnormal overpower lighting due to incorrect assembly of the discharge lamp. It becomes possible to prevent it. In addition, the lamp current of a discharge lamp containing mercury is 8
Seeing as low as 0.41A at 5V, if the lamp current falls below a certain set current of about 0.5A to 0.7A, it is considered as abnormal non-lighting and even if it is stopped It is possible to prevent overpower lighting.

FIG. 4 is a diagram showing the above-mentioned stop protection operation according to the present embodiment, and shows an example of the stop protection operation by judging the lamp voltage and the lamp current with respect to the wrong assembly of the discharge lamp. The points A to B are the 35 W constant power region (35 V to 45 V) of the discharge lamp not containing mercury, and the point C is the operating point (85 V) of the discharge lamp containing mercury. Further, X indicates a stop region due to the lamp voltage, and Y indicates a stop region due to the lamp current.

As described above, in this embodiment, the optimum starting control of the discharge lamp can be always performed, and the appropriate starting control can be performed even in the discharge lamp not containing mercury. It is also possible to prevent the occurrence of abnormalities due to incorrect assembly.

That is, in the lamp voltage detection in the starting control circuit of the conventional discharge lamp lighting device, there is a problem of 20 kV withstand voltage of the detection element and a problem of high voltage pulse attenuation in order to directly detect the lamp voltage. It has been general to detect with a DC / DC converter output in the shape of an ellipse. Therefore, when the lamp current increases at the time of starting, the error increases between the detected lamp voltage and the actual lamp voltage due to the resistance of the starting transformer winding and the FET ON resistance of the H bridge of the DC / AC inverter, and the rising control of the luminous flux. Was difficult to optimize. In the case of a discharge lamp that does not contain mercury, the lamp voltage is originally low, so even if the lamp voltage is detected, there will be no difference in the lamp voltage between the time of starting and the time of stabilization, and starting control by the lamp voltage will be impossible. It was.

However, in the starting control according to the present embodiment, the influence of the error in the winding resistance and the FET on resistance at the time of starting in the detected lamp voltage is corrected according to the detected lamp current, so that the output from the DC / DC converter output unit is actually used. It is possible to obtain a detection value corresponding to the lamp voltage of. Therefore, it is possible to carry out the lamp starting control set in advance according to the lamp voltage.

Further, even in a discharge lamp having a low lamp voltage which does not contain mercury, the lamp voltage at the time of starting and at the time of stable can be accurately detected, so that the starting control by the detected lamp voltage is also possible.

Further, as in the case where a mercury-encapsulated discharge lamp is erroneously attached to a mercury-free discharge lamp lighting device, the discharge lamps of different types have different power control settings at startup and during stabilization. There is a risk of abnormal overpowering due to
According to the present embodiment, after a certain period of time after which the lamp voltage after lighting has stabilized, when the voltage exceeds a certain set lamp voltage, it is stopped to prevent abnormal overpower lighting due to incorrect assembly of the discharge lamp. It will be possible. Also, by stopping the lamp when it becomes lower than a certain set lamp current, the erroneous assembly lighting can be stopped in the same manner.

[0047]

As described above, according to the present invention,
Since the lamp voltage detection value is corrected and changed according to the lamp current detection value, optimum starting control of the discharge lamp can be performed at all times, and even when a discharge lamp with a low lamp voltage that does not contain mercury is used at startup and when stable. Since the lamp voltage can be detected accurately, there is an effect that appropriate starting control can be performed.

Further, there is an effect that it is possible to prevent the occurrence of abnormal overpower lighting due to erroneous assembly of a discharge lamp having different power control settings at the time of starting and at the time of stable.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a lamp voltage of an example.

FIG. 3 is a diagram showing an example of power control according to the embodiment.

FIG. 4 is an explanatory diagram showing a stop protection operation according to the embodiment.

FIG. 5 is a block diagram showing a circuit configuration of a conventional discharge lamp lighting device.

FIG. 6 is a diagram showing an example of conventional power control.

[Explanation of symbols]

1 DC power supply 2 DC / DC converter 3 DC / AC inverter 4 startup transformer 5 discharge lamp 6 Lamp voltage detection circuit 7 Lamp current detection circuit 8 Lamp power control circuit 9 Lamp voltage correction circuit

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K072 AA11 AB09 AC01 AC11 BA05                       BC01 CB02 DD08 DE02 DE04                       EA02 EB05 EB07 GA02 GB18                       HA10                 3K083 AA01 AA03 AA06 AA30 AA94                       BA12 BA25 BA26 BA33 BB06                       BB10 BC33 BC47 BD03 BD04                       BD15 BD16 BD22 BD28 BD29                       CA28

Claims (7)

[Claims] 1. A lamp voltage detection circuit for detecting a lamp voltage of a discharge lamp and a lamp current detection circuit for detecting a lamp current, and a target lamp current or lamp based on a lamp voltage detection value of the lamp voltage detection circuit. In the process of setting the power and setting the target value, the target value is corrected by the lamp current detection value of the lamp current detection circuit, and the lamp power of the discharge lamp is controlled by the corrected target value. Discharge lamp lighting device. 2. The discharge lamp lighting device includes a lamp voltage correction circuit that corrects and changes the lamp voltage detection value of the lamp voltage detection circuit according to the lamp current detection value of the lamp current detection circuit. 2. The discharge lamp lighting device according to claim 1, wherein a target lamp current or lamp power is set based on the detected lamp voltage value corrected by the circuit to control the lamp power of the discharge lamp. 3. The lamp voltage correction circuit sets the correction amount of the detected lamp voltage value to the detected lamp current value to the maximum correction amount of the lamp voltage at the maximum lamp current at the time of starting the discharge lamp, and then the lamp current 3. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is lowered as the amount thereof decreases. 4. An H-bridge type transistor inverter for supplying AC power to a discharge lamp and a starting transformer for applying a high voltage pulse to the discharge lamp, wherein the lamp voltage detection circuit has an ON voltage of a transistor of the transistor inverter. The discharge lamp lighting device according to claim 1, wherein a value obtained by adding both the winding voltage of the starting transformer and the winding voltage to the lamp voltage is output. 5. A starting transformer for applying a high-voltage pulse to the discharge lamp, wherein the lamp voltage detection circuit outputs a value obtained by adding the winding voltage of the starting transformer to the lamp voltage. The discharge lamp lighting device according to any one of 1 to 3. 6. When an abnormal overpower condition occurs due to a combination of lamp characteristics different from the setting of the lamp power control at the time of starting and stabilizing the discharge lamp, after a lapse of the time for the lamp voltage to stabilize immediately after lighting, The discharge lamp lighting device according to any one of claims 1 to 5, wherein the lighting is stopped when the voltage exceeds a certain set lamp voltage or becomes less than a certain set lamp current. 7. A lighting device for lighting a discharge lamp that does not contain mercury, wherein a discharge lamp containing mercury is lit.
7. The discharge lamp lighting device according to claim 6, wherein the lighting is stopped when it is determined to be abnormal.