JP2946384B2 - Lighting circuit for vehicle discharge lamps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lighting circuit for a discharge lamp for a vehicle. More specifically, an object of the present invention is to provide a novel lighting circuit for a discharge lamp for a vehicle in which power control according to individual differences of the discharge lamps is performed to reduce variations in the start time of the discharge lamps. .

[0002]

2. Description of the Related Art In recent years, small metal halide lamps have attracted attention as light sources for vehicle lamps, but their startability has become a problem. 2. Description of the Related Art There is known a method in which an excessively large lamp current is applied to rapidly heat an arc tube to promote light emission.

[0005] However, simply flowing an excessive lamp current in the initial stage of lighting causes remarkable overshoot or the like until the luminous flux of the discharge lamp is stabilized, and the luminous flux fluctuates greatly. As a method, the applicant of the present invention has proposed a lighting circuit in which the luminous flux is quickly shifted to a stable value, as disclosed in Japanese Patent Application No. 2-263300 (Japanese Unexamined Patent Application Publication No. Hei.
No. 41988).

In this example, the lighting circuit of the vehicle discharge lamp is
A lamp voltage detector for converting a DC voltage into an AC voltage to supply the discharge lamp with a DC-AC converter, and a lamp voltage detector for obtaining a detection signal relating to the lamp voltage of the discharge lamp; Receiving a detection signal from the lamp current detector for obtaining a signal, and a lamp current control command signal for the lamp voltage in response to the detection signal from the lamp voltage detector, and calculating a difference between the command signal and the detection signal from the lamp current detector. And a voltage-current characteristic control unit for controlling the output voltage by transmitting a control signal to the DC-AC conversion means so as to prevent the occurrence of the control signal.

[0005] Then, as a control area on the lamp voltage-lamp current characteristic, a constant power at the rated power is changed from a light emission promotion area for generating a lamp current control command signal so that power supply exceeding the rated power of the discharge lamp is performed. When shifting to the constant power control region where the control is performed, a power change rate reducing unit is provided for controlling the change rate of the power supplied to the discharge lamp with respect to the lamp voltage to be gentle.

In FIG. 14, the horizontal axis represents the lamp voltage (denoted by "VL"), and the vertical axis represents the lamp current (denoted by "IL").
5 shows an example a of the control line.

In the figure, a section of IL = ILmax is defined as a light emission promotion area Aa, and a section obtained as a linear approximation of a constant power curve is defined as a constant power control area B. The section is represented by an inclined straight line provided between the two areas. The section to be performed is defined as a transition area Ab.

In the control line in the transition region Ab, the lamp current IL decreases with a certain slope with respect to the increase in the lamp voltage VL, and the change in the power supplied to the discharge lamp is alleviated. Overshoot and undershoot are suppressed, and the time required for the luminous flux to stabilize is reduced.

[0009]

By the way, the discharge lamp has a difference in performance due to a manufacturing error, and the individual difference of the discharge lamp is reflected in the rising characteristic of the luminous flux. Since the lighting circuit does not perform power control corresponding to the individual differences of the discharge lamps, there is a problem that the starting time varies.

FIG. 15 schematically shows a temporal change of the lamp voltage VL when two discharge lamps having individual differences are turned on from a cold state (at the time of a so-called cold start). is there.

Assuming that the discharge lamp having the characteristics shown in FIG. 15A is “discharge lamp A” and the discharge lamp having the characteristics shown in FIG. While the lamp voltage VL rises relatively smoothly with the passage of time, in the discharge lamp B, the ramp-up rate of the lamp voltage VL increases after a certain time t = tc.

FIG. 16 schematically shows a temporal change of a light beam (denoted by "L") corresponding to FIG.
(A) shows the rising characteristics of the luminous flux relating to the discharge lamp A,
(B) shows the rising characteristics of the luminous flux of the discharge lamp B.

As shown in the figure, when a certain time has elapsed from the start of lighting, the discharge lamp B rapidly approaches the control state in the constant power control region as compared with the discharge lamp A (this is the case). Corresponds to the rise of the lamp voltage VL shown in FIG. Then, the excess power supplied when the control of the discharge lamp approaches the constant power control region causes an overshoot in the change in the luminous flux, and as a result, the time until the rated luminous flux is stabilized becomes long.

In this example, it is assumed that an appropriate power control is performed on the discharge lamp A. However, when a setting for appropriately controlling the discharge lamp B is performed, the start-up of the discharge lamp A is performed. The characteristics will be degraded.

In other words, suppressing the overshoot in the change of the luminous flux of the discharge lamp B results in delaying the rise of the luminous flux of the discharge lamp A, resulting in a disadvantage that the time required to reach the rated luminous flux becomes longer. .

[0016]

In order to solve the above-mentioned problems, a lighting circuit for a vehicle discharge lamp according to the present invention converts a DC voltage into a DC voltage and / or converts it into an AC voltage and supplies the voltage to the discharge lamp. Power supply means for detecting a lamp voltage of a discharge lamp or a lamp voltage detector for obtaining a signal corresponding thereto, and a lamp current detector for obtaining a detection signal regarding a lamp current of the discharge lamp or a corresponding signal. Receives a detection signal from the lamp voltage detector, generates a lamp current control command signal for the lamp voltage, and supplies a control signal so that the difference between the command signal and the detection signal from the lamp current detector does not occur. Means for controlling the output voltage of the discharge lamp as a control area on the lamp voltage-lamp current characteristic. A discharge lamp for vehicles having a light emission promoting region for generating a lamp current control command signal so that power supply exceeding the rated power is performed, and a constant power control region for performing constant power control at rated power with respect to the discharge lamp. In the lighting circuit, the time variation of the lamp voltage or its equivalent signal
Detection rate, and according to the detection result of the change rate
In the transition region from the emission promotion region to the constant power control region.
Control the rate of change of supply power to lamp voltage
The above-mentioned temporal change
Power supply to the discharge lamp to be suppressed as the rate increases
It was made.

[0017]

According to the present invention, the temporal change rate of the lamp voltage or its equivalent signal is detected, and the temporal change is detected in the transition area.
Since the rate of change of the supplied power with respect to the lamp voltage is controlled according to the conversion rate , for example, if the lamp voltage suddenly rises at some point after starting, the luminous flux is reduced by suppressing the supplied power to the discharge lamp. Overshoot in the temporal change of the discharge lamp can be prevented, and the starting time can be made constant by performing power control corresponding to the individual difference of the discharge lamp.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the lighting circuit for a vehicle discharge lamp according to the present invention will be described below with reference to the illustrated embodiments.

Prior to the description of the circuit configuration of the lighting circuit 1 for a vehicle discharge lamp, the lamp voltage (VL) -the lamp current (I
L) Control lines relating to characteristics will be described.

FIG. 1 shows VL-IL characteristics.

As shown by the constant straight line ga, the point M from VL = 0
Is a light emission promotion region, and a constant maximum current IL = ILmax flows in this region.

In the transition region Ab from the point M to the point Q1, the control line gb smoothly changes exponentially and is connected to the operating point Q1 on the approximate straight line in the constant power control region B.

That is, in the transition region Ab, the lamp voltage VL
Is controlled so that the rate of change of the lamp current with respect to the lamp voltage VL decreases with the increase of the lamp voltage VL, and the process shifts to the constant power control region B.

In forming the control line gb, FIG.
, A method of adding a time constant circuit to a circuit forming a linear control line indicated by a broken line, and a method of providing a circuit for interpolating between the point M and the point Q1 with a curve that changes exponentially. .

An area B from the point Q1 to the point Q2 is a constant power control area, and a straight line gc passing through the points Q1 and Q2 is obtained by performing a linear approximation to the constant power curve PQ. The power value indicated by the constant power curve PQ is the rated power of the lamp.

In a region C starting from the point Q2, a constant straight line gd
As shown in the graph, IL is constant (I
L = IC).

As can be seen from the above, the control characteristic in the transition region Ab is independent of the individual difference of the lamp, and the change of the supplied power is uniformly defined.

Accordingly, if the circuit constants are set so as to perform the control convenient for the discharge lamp A as it is, the start control of the discharge lamp B cannot be appropriately performed.

That is, since excessive power is supplied regardless of the characteristics of the discharge lamp B, the lamp voltage VL rapidly increases at a certain point in time as shown in FIG. As a result of rapidly approaching the control state, an overshoot occurs in the rising of the light beam.

Therefore, a change in the lamp voltage VL is detected, and the detection result is reflected in the power control.
If the control is performed so that the supplied power decreases (increases) with respect to the increase (decrease) of the lamp voltage VL, it is possible to realize the appropriate start control with respect to the individual difference of the discharge lamp.

FIGS. 2 to 4 show an example of the configuration of a lighting circuit for a discharge lamp for a vehicle according to the present invention. In the illustrated embodiment, the present invention is applied to a lighting circuit 1 for a metal halide lamp for a vehicle using a rectangular wave lighting method. It was done.

FIG. 2 shows an outline of the configuration of the lighting circuit 1, in which a battery 2 is connected between DC voltage input terminals 3, 3 '.

Reference numerals 4 and 4 'denote DC power supply lines, and a lighting switch 5 is provided on one of the plus lines 4.

Reference numeral 6 denotes a DC booster circuit.
For example, a configuration of a chopper type DC-DC converter is used, and the boosting control is performed by a control circuit described later.

Reference numeral 7 denotes a DC-AC conversion circuit, which is provided at the subsequent stage of the DC boosting circuit 6 and converts a DC voltage sent from the DC boosting circuit 6 into a rectangular-wave AC voltage. As the DC-AC conversion circuit 7, for example, a bridge-type drive circuit including two pairs of FETs is used.

Reference numeral 8 denotes an igniter circuit, which is arranged at a stage subsequent to the DC-AC conversion circuit 7 and has AC output terminals 9 and 9 '.
A metal halide lamp 10 having a rated power of 35 W is connected between them.

Numeral 11 denotes a control circuit for controlling the output voltage of the DC booster circuit 6. The control circuit 11 controls the output voltage of the DC booster circuit 6 detected by the voltage detector 12 provided between the output terminals of the DC booster circuit 6. A corresponding voltage detection signal is input.

Further, a current detection signal corresponding to the output current of the DC booster circuit 6 is voltage-converted by the current detector 13 provided on the ground line connecting the DC booster circuit 6 and the DC-AC converter circuit 7. The data is input to the control circuit 11 in the form. In the present embodiment, a signal corresponding to the lamp voltage or lamp current of the metal halide lamp 10 is obtained from the output stage of the DC booster circuit 6. However, a configuration in which these signals are directly detected may be employed. Of course.

The control circuit 11 generates a control signal corresponding to the above-mentioned detection signal, sends it to the DC booster circuit 6, and controls the output voltage to perform power control in accordance with the starting state of the metal halide lamp 10. , The start time and the restart time of the lamp are shortened, and the control is promptly shifted to the constant power control. The V (voltage) -I (current) characteristic control unit 1
4 and a PWM (pulse width modulation) control unit 15.

The VI characteristic control section 14 is configured to control the lighting of the metal halide lamp 10 based on the control line described in FIG. 1, and a detection signal relating to the output voltage of the DC booster circuit 6 is output from the voltage detection section. When it is sent from the control unit 12, a current command value corresponding to the detection signal is obtained by calculation, and this is compared with an actual current value to send a command signal to the PWM control unit 15.

The PWM control unit 15 includes the VI characteristic control unit 1
A signal having a variable pulse width is generated in response to a command signal from the control unit 4 and is used as a control signal to a semiconductor switch element (not shown) of the DC booster circuit 6 (this signal is referred to as “PS”).
Is transmitted. In this embodiment, control is performed so that the output voltage of the DC booster circuit 6 increases by increasing the duty cycle of the control pulse PS.

FIG. 3 shows an example of the configuration of the main part of the VI characteristic control unit 14, and the circuit unit 14 related to the formation of the control line g.
A, and a lamp voltage change detection / power control correction unit 14B related to detection of lamp voltage change and lamp power correction control.

The circuit section 14A has amplifiers 16, 17, and 18 involved in forming control lines, and an amplifier 19 that relays the output of these amplifiers and sends a signal to the error amplifier of the PWM control section 15.

The amplifier 16 is involved in forming the control line ga in the light emission promotion area Aa, and the amplifier 17 is involved in forming the control line gc in the constant power control area B. Then, the amplifier 18 is involved in forming the control line gb in the transition area Ab.

The detection signals of the voltage detection unit 12 are converted into voltage detection signals (hereinafter referred to as “VS”) by an amplifier (not shown) with a certain amplification factor, and the amplifiers 17 and 18.
Respectively.

The detection signal of the current detection unit 13 is converted into a current detection signal (hereinafter, referred to as “IS”) by an amplifier (not shown) with a certain amplification factor.
6 and 17 are sent.

The amplifier 16 is configured as an inverting amplifier circuit using an operational amplifier 20, and a current detection signal IS is input to an inverting input terminal of the operational amplifier 20 via a voltage dividing resistor, and a non-inverting input terminal is connected to a non-inverting input terminal. Reference voltage (referred to as “E1”)
Is supplied.

The output of the amplifier 16 is sent to the inverting input terminal of the operational amplifier 23 constituting the amplifier 19 via the diode 21 and the resistor 22.

The amplifier 17 has the configuration of an inverting amplifier circuit using an operational amplifier 24. The voltage detection signal VS and the current detection signal IS are input to the inverting input terminal of the operational amplifier 24 via resistors 25 and 26, respectively. , A non-inverting input terminal is supplied with a reference voltage (referred to as “E2”).

The output of the amplifier 17 is sent to the inverting input terminal of the operational amplifier 23 via the resistor 27.

The amplifier 18 is configured as an inverting amplifier circuit using an operational amplifier 28. The voltage detection signal VS is input to an inverting input terminal of the operational amplifier 28 via a resistor, and a reference voltage is applied to a non-inverting input terminal. (Referred to as “E3”).

The output terminal of the operational amplifier 28 is connected to a buffer 29.
Is sent to the buffer 30 at the subsequent stage.

The output stage of the buffer 29 has a time constant circuit 31
The time constant circuit 31 includes a capacitor 32, a resistor 33, a resistor 34, and a diode 35 connected in parallel. That is, the capacitor 32 and the resistor 33 provided in parallel with each other have one end thereof connected to the buffer 29 via the resistor 36.
Of the capacitor 32 and the resistor 3
A reference voltage (referred to as “E4”) is supplied to the other end of the reference numeral 3.

The resistor 34 and the diode 35 are provided in parallel with the resistor 33. The anode of the diode 35 is connected to one end of the resistor 34, and the reference voltage E4 is applied to the cathode of the diode 35.

The output of the buffer 30 is sent to the amplifier 19 via the resistors 37 and 38. That is, the resistance 37 and the resistance 3
8 is sent to the inverting input terminal of the operational amplifier 23 of the amplifier 19.

The outputs of the amplifiers 16, 17, and 18 are input to the inverting input terminal of the operational amplifier 23, and the reference voltage (referred to as "E5") is supplied to the non-inverting input terminal.

The output of the operational amplifier 23 is sent to the error amplifier 39 of the PWM control unit 15 via a resistor.

A general-purpose IC for a switching regulator is used for the PWM control unit 15, and an error amplifier, an oscillator, a comparator, a reference voltage source, and the like are packaged therein.

The output signal of the operational amplifier 23 is connected to a negative input terminal of the error amplifier 39 in the IC.
, And a predetermined reference voltage is supplied to the plus input terminal of the error amplifier 39.
When the input voltage to the error amplifier 39 increases, the output signal P
Control is performed such that the duty cycle of S decreases, and as a result, the output voltage of DC booster circuit 6 decreases.

Reference numeral 41 denotes an error amplifier 3 externally connected to the IC.
9 is a feedback resistor.

In this circuit, the amplifier 16 defines the upper limit value of the current in the light emission promotion area Aa. When the current detection signal IS becomes higher than the reference value corresponding to the reference voltage E1, the operation of the operational amplifier 23 is stopped. To lower the potential of the inverting input terminal.

As a result, the output of the amplifier 19 increases, so that the duty cycle of the control signal PS is suppressed, and control is performed so that the lamp current does not excessively flow.

Amplifier 17 for Forming Constant Power Control Region B
Is an addition circuit for the current detection signal IS and the voltage detection signal VS, and forms a control line gc by linear approximation to a constant power curve.

That is, the constant power control is performed so that the value of the approximate expression obtained by linearly combining the value of the current detection signal IS and the value of the voltage detection signal VS at a predetermined ratio becomes a constant value (corresponding to the reference voltage E2). Done.

The amplifier 18 related to the formation of the transition region Ab
The control line gb is formed by the time constant circuit 31 as a curve that decays exponentially as the lamp voltage VL increases.

That is, when the time constant circuit 31 is not considered, the output voltage of the amplifier 18 decreases linearly with the increase of the voltage detection signal VS, and as shown by the broken line in FIG. Although the connection of the control lines near the boundary between Ab and the constant power control region B becomes a broken line, the connection of the control lines is smoothed by the time constant circuit 31 as shown by the solid line in FIG.

The operation of the time constant circuit 31 will be described. When the metal halide lamp 10 is cold-started, the lamp voltage VL immediately after the start of lighting is small, so that the output of the amplifier 18 becomes large. Charges instantly.

FIG. 5 shows that the discharge lamp A is connected to the lighting circuit 1.
Of the lamp voltage VL at the cold start
FIG. 6 is a diagram showing a temporal change, and FIG.
The output voltage (this is o (18) ". ) And con
The terminal voltage of the capacitor 32 (referred to as “V (32)”)
You. FIG.

When the lamp control enters the transition region Ab, the output voltage Vo (18) of the amplifier 18 falls contrary to the rise of the lamp voltage VL.

The terminal voltage V (32) also decreases in accordance with Vo (18), but the degree of the decrease is determined by resistors 33 and 34.
, And a time constant determined by the capacitance of the capacitor 32, and gradually approaches a certain reference voltage (this is referred to as “Vc”) over time.
The time constant is set to have two values in accordance with the conduction or non-conduction of the diode 35.

The state of “V (32) = Vc” corresponds to the steady state of the lamp, and the state of “V (32)> Vc” indicates that the power supplied to the lamp is large. That is, V (3
Since the increasing direction of 2) coincides with the decreasing direction of the input voltage of the error amplifier 39, when V (32) is large, the duty cycle of the control pulse PS is controlled to increase, and the power supplied to the lamp increases. become.

Lamp voltage change detection / power control correction unit 14
B detects a change in the voltage detection signal VS and corrects the supplied power based on the result. In this example, instead of directly detecting a time change of VS, which is a signal corresponding to the lamp voltage VL, a time change is performed. , The output voltage Vo of the amplifier 18 (1
8) and the output voltage of the buffer 30 (this is referred to as “Vo (30)”) is compared and amplified, and the result is returned to the input of the buffer 30.

FIG. 4 shows an example of the configuration of the lamp voltage change detection / power control correction section 14B.

The output voltage Vo (18) of the amplifier 18 is input to the buffer 42, and the output of the buffer 42 is sent to the subsequent buffer 44 after passing through the comparison circuit 43.

The buffer 42 has a configuration of a non-inverting ideal diode circuit using an operational amplifier 45. That is, Vo (18) is supplied to the non-inverting input terminal of the operational amplifier 45, the output terminal of which is connected to the anode of the diode 46, and the cathode of the diode 46 is connected to the operational amplifier 4
5 inverting input terminals.

The cathode of the diode 46 is connected to one input terminal of the comparison circuit 43 via the resistor 47, and is connected between the resistor 48 and the resistor 49. A predetermined voltage (Vref) is supplied to one end of the resistor 48, and the other end is grounded via a resistor 49.

The comparator 43 is configured as an inverting amplifier using an operational amplifier 50, and the non-inverting input terminal of the operational amplifier 50 is connected between the resistors 48 and 49 via the resistor 47. The inverting input terminal of the operational amplifier 50 is connected to the output terminal of the buffer 30 via the resistor 51.

Reference numeral 52 denotes a feedback resistor inserted between the inverting input terminal and the output terminal of the operational amplifier 50.

The output terminal of the operational amplifier 50 is connected via a resistor 53 to the input terminal of the buffer 44 at the subsequent stage.

The buffer 44 has a configuration of a non-inverting type ideal diode circuit using an operational amplifier 54. That is, the output voltage of the operational amplifier 50 is supplied to the non-inverting input terminal of the operational amplifier 54, and the output terminal is connected to the cathode of the diode 55. The anode of the diode 55 is connected to the inverting input terminal of the operational amplifier 54 and to the input terminal of the buffer 30 via the resistor 56.

FIGS. 5 to 12 show the temporal change of the voltage value of each unit in the lamp voltage change detection / power control correction unit 14B when the two types of discharge lamps A and B are used. FIGS. 5 to 8 are graphs relating to the discharge lamp A, and FIGS. 9 to 12 are graphs relating to the discharge lamp B.

Referring to the discharge lamp A, as shown in FIGS. 5 and 6, Vo (18) increases as the lamp voltage VL increases.
Decreases, but Vo (30) approaches reference voltage Vc with a gentler slope than Vo (18).

The voltage supplied to the inverting input terminal of the operational amplifier 50 (this is referred to as “VI ₊ (50)”) is shown in FIG.
As shown in FIG. 5, the same change as Vo (18) is observed until a certain point (denoted as “tp”). However, after tp, the resistance changes to a fixed value (slightly larger than Vc, and
8 and 47 are set as values obtained by dividing the voltage Vref. ).

The output voltage of the operational amplifier 50 (this is referred to as “Vo
(50) ". ) Is V, as shown in FIG.
It becomes a voltage proportional to the voltage difference between _{I +} (50) and Vo (30), and this voltage is applied to the voltage V (3
2) will be affected. That is, when Vo (50) is a negative voltage (the maximum width is described as “ΔV”), the terminal voltage of the capacitor 32 decreases and Vo (30) decreases, so that the power supplied to the lamp decreases. Is controlled.

In the discharge lamp B, as shown in FIGS. 9 and 10, as the lamp voltage VL sharply rises, Vo increases.
Although (18) greatly decreases, V (32) and Vo (3
0) approaches the reference voltage Vc with a relatively gentle slope.

Therefore, since the voltage V _{I +} (50) shows the same change as Vo (18) until a certain point (denoted by “tp ′”), V _{I +} (50) and Vo (30) )
The maximum width ΔV of Vo (50), which is proportional to the difference voltage from the discharge lamp A, is larger than that of the discharge lamp A. This allows V
The reduction width of (32) is larger than in the case of FIG. 8, and the effect of suppressing the supplied power is increased. That is, by suppressing the increase in the lamp voltage VL due to the characteristics of the discharge lamp B, the change in the luminous flux (in this case, overshoot) that would occur according to the conventional lighting control is suppressed by stopping the supply power. be able to.

As described above, until a certain point, the lamp voltage VL
(V _{I +} (50)) which faithfully reflects the change of the lamp voltage VL, and the signal Vo (3) which is based on the change of the lamp voltage VL but whose rate of decrease is alleviated by the time constant circuit 31.
0) by indirectly determining the lamp voltage VL
By detecting the rate of change of the power and correcting the power control according to the detection result, it is possible to appropriately perform the starting control according to the characteristics of the lamp. As a matter of course, a circuit 14C configured to purely detect the temporal change rate of the lamp voltage VL as shown in FIG. 13 can be used.

The circuit 14C comprises a buffer 57, a delay circuit 5
8, a comparison circuit 59, and a buffer 60, and the output voltage Vo (18) is a two-system signal.
Is input to

That is, Vo (18) is sent to the minus input terminal of the comparison circuit 59 via the path of the buffer 57 and the delay circuit 58, and Vo (18) is sent directly to the plus input terminal of the comparison circuit 59. Can be Then, the output of the comparison circuit 59 is sent to the input terminal of the buffer 30 via the buffer 60.

In this case, the time difference signal of Vo (18) is detected and the power control is corrected.

[0091]

As is apparent from the above description, according to the lighting circuit for a vehicle discharge lamp of the present invention, the temporal change rate of the lamp voltage or its corresponding signal is detected and the transition area is determined.
In the range, the rate of change of the supplied power with respect to the lamp voltage is controlled in accordance with the temporal change rate , for example, when the lamp voltage sharply rises at some point after starting from a difference in characteristics due to individual differences of the discharge lamp. By suppressing the power supplied to the discharge lamp, overshoot in the temporal change of the luminous flux can be prevented, thereby reducing the variation in the starting time.

The specific circuit configurations shown in the above embodiments are merely examples for embodying the present invention, and the technical scope of the present invention is interpreted in a limited manner. Not something. For example, the present invention can be widely applied not only to a rectangular wave lighting method but also to a lighting circuit of a sine wave lighting method and the like.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a control line according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a lighting circuit of the vehicular discharge lamp according to the present invention.

FIG. 3 is a circuit diagram showing a main part of a VI characteristic control unit.

FIG. 4 is a circuit diagram illustrating a configuration example of a lamp voltage change detection / power control correction unit.

FIG. 5 is a graph showing a temporal change of a lamp voltage when a discharge lamp A is connected to a lighting circuit.

FIG. 6 illustrates an output voltage Vo (18) of the amplifier 18 and an output voltage Vo (30) of the buffer 30 in order to explain the operation of the lamp voltage change detection / power control correction unit when the discharge lamp A is connected to the lighting circuit. FIG. 7 is a graph showing a temporal change of FIG.

FIG. 7 is a graph showing a temporal change of an input voltage V _{I +} (50) of an operational amplifier 50 in order to explain an operation of a lamp voltage change detection / power control correction unit when a discharge lamp A is connected to a lighting circuit. FIG.

FIG. 8 is a graph showing a temporal change of an output voltage Vo (50) of an operational amplifier 50 for explaining an operation of a lamp voltage change detection / power control correction unit when a discharge lamp A is connected to a lighting circuit. is there.

FIG. 9 is a graph showing a temporal change in lamp voltage when a discharge lamp B is connected to a lighting circuit.

FIG. 10 illustrates an output voltage Vo (18) of the amplifier 18 and an output voltage Vo (30) of the buffer 30 in order to describe the operation of the lamp voltage change detection / power control correction unit when the discharge lamp B is connected to the lighting circuit. FIG. 7 is a graph showing a temporal change of FIG.

FIG. 11 is a graph showing a temporal change of an input voltage V _{I +} (50) of an operational amplifier 50 for explaining an operation of a lamp voltage change detection / power control correction unit when a discharge lamp B is connected to a lighting circuit. FIG.

FIG. 12 is a graph showing a temporal change in the output voltage Vo (50) of the operational amplifier 50 for explaining the operation of the lamp voltage change detection / power control correction unit when the discharge lamp B is connected to the lighting circuit. It is.

FIG. 13 is a circuit diagram showing a modification of the lamp voltage change detection / power control correction unit.

FIG. 14 is a graph showing an example of a conventional control line.

FIG. 15 is a diagram for explaining a conventional problem;
(A) is a graph showing a temporal change of a lamp voltage of a discharge lamp A, and (b) is a graph showing a temporal change of a lamp voltage of a discharge lamp B.

FIG. 16 is a diagram for explaining a conventional problem;
(A) is a graph showing a temporal change of a luminous flux relating to the discharge lamp A, and (b) is a graph showing a temporal change of a luminous flux relating to the discharge lamp B.

[Explanation of symbols]

Reference Signs List 1 lighting circuit for vehicle discharge lamp 6, 7 power supply means 10 metal halide lamp (discharge lamp) 12 voltage detector (lamp voltage detector) 13 current detector (lamp current detector) 14 voltage-current characteristic controller 14B lamp Voltage change detection / power control correction section (power control means) 14C Lamp voltage change detection / power control correction section (power control means) Aa Light emission promotion area Ab transition area B Constant power control area

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 41/14-41/29

Claims (2)

(57) [Claims] Power supply means for converting a DC voltage into a DC voltage and / or an AC voltage and supplying the converted voltage to a discharge lamp;
A lamp voltage detecting unit for obtaining a detection signal or a signal corresponding to the lamp voltage of the discharge lamp; a lamp current detecting unit for obtaining a detection signal or a signal corresponding to the lamp current of the discharge lamp; and a lamp voltage detecting unit. In response to the detection signal, a lamp current control command signal for the lamp voltage is generated, and a control signal is sent to the power supply means so that the difference between the command signal and the detection signal from the lamp current detection unit does not occur. A voltage-current characteristic control unit for controlling the voltage, wherein the voltage-current characteristic control unit controls the lamp current so that the power supply exceeding the rated power of the discharge lamp is performed as a control region on the lamp voltage-lamp current characteristic. A discharge lamp for a vehicle having a light emission promoting region for generating a control command signal for the discharge lamp and a constant power control region for performing constant power control at a rated power with respect to the discharge lamp. In the circuit, detects the temporal variation rate of the ramp voltage or equivalent signal thereof
At the same time, according to the detection result of the change rate,
Ramp in the transition region from the lead region to the constant power control region
Power control to control the rate of change of supply power to voltage
By providing means, it is possible to
A lighting circuit for a vehicular discharge lamp, characterized in that power supplied to the discharge lamp is suppressed . 2. The lighting circuit for a discharge lamp for a vehicle according to claim 1, wherein the power control means controls a supply voltage according to a predetermined control line in the transition area with respect to a lamp voltage or a signal corresponding thereto. A lighting circuit for a discharge lamp for a vehicle, wherein a rate of change of supply power with respect to a lamp voltage is controlled by adding an increase or decrease of power according to a temporal change rate .