JPH10125489A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device in which an initial rising speed of a beam is increased in the case of a cold start. SOLUTION: A primary DC/DC converter circuit 11 controls an electric power supply to a high voltage discharge lamp La1 for a low beam by rising a direct current voltage of a direct current power source E. An auxiliary DC/DC converter circuit 4 is connected with the primary DC/DC converter circuit 11 in parallel, and its output end is connected with that of the primary DC/DC converter circuit 11 through a switching element Q4 and a diode D4 . In such a case that a voltage of a high voltage discharge lamp La1 is lower than a prescribed threshold value in an initial start period of the high voltage discharge lamp La1 just after a starting of the discharge lamp La1 , a control circuit 6 turns on the switching element Q4 and makes an electric power supply to the primary DC/DC converter circuit 11 as well as a primary inverter circuit 21 from the auxiliary DC/DC converter circuit 4, and an initial rising of a beam is speeded up in the high voltage discharge lamp La1 .

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 using a DC power source such as a battery as a power source.

[0002]

2. Description of the Related Art Conventionally, a high-pressure discharge lamp such as a metal halide lamp has been used as a new light source for a vehicle-mounted headlamp. As a discharge lamp lighting device using this high pressure discharge lamp, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-212473, a DC power supply of 12 V DC or 24 V DC composed of a battery, and a DC power supply for boosting the DC voltage of this DC power supply Some have a flyback converter circuit as a / DC converter circuit and a polarity inversion circuit as an inverter circuit that alternately converts the output voltage of the flyback converter circuit into an AC voltage.

[0003]

In the above-described discharge lamp lighting device, sufficient light emission cannot be obtained unless the metal vapor pressure inside the high-pressure discharge lamp becomes higher than a predetermined pressure. In particular, at the time of a cold start, since the vapor pressure of metal such as mercury, which greatly affects the lamp voltage, is low, the lamp voltage tends to decrease. In such a state, in order to quickly start the luminous flux of the high-pressure discharge lamp, it was necessary to increase the lamp current and supply power larger than the rated power of the high-pressure discharge lamp during stable lighting.

[0004] For example, the rated power W_La2(= 35W) D2
S-type HID lamp for vehicle (High Intensity Discharge)
 Lamp) from the time immediately after startup to the time of stable lighting
Lamp voltage V_LaAnd lamp power W_LaFigure 7 shows the relationship
You. Cold start the HID lamp at point A,
During the period immediately after startup, the metal vapor pressure inside the HID lamp is low.
The lamp voltage V_LaIs as low as about 20V,
The rise of the luminous flux was slow. However, the car
When used for both headlights, etc., the luminous flux
It is necessary to make the climb faster.
Force W_La2Above lamp power W_LaIs applied to the HID lamp
However, at point B, the lamp power W is about 75 W at maximum. _La1Apply
Then, the rise of the luminous flux was hastened. And section B
In -C, when the metal vapor pressure inside the HID lamp increases,
In both cases, the lamp voltage V_LaGradually rises to about 85V,
Lamp power W_LaGradually decreases to the rated power W_La2Approaching
Good. At point C, the lamp power W of the HID lamp_LaIs the rated power
W_La2And the HID lamp is stably lit.

By the way, the flyback converter described above
The DC / DC converter circuit composed of
The primary winding and switch of the step-up transformer connected to the output terminal of the power supply
A series circuit consisting of switching elements and a step-up transformer
A diode connected between both ends of the secondary winding and a smoothing capacitor
And a series circuit consisting of a capacitor.
Using a power converter, from the start to the time of stable lighting.
Lamp power W_LaWhen controlling the primary winding of the step-up transformer
Current I flowing through the switching element connected to the line_QWaves
The shape is shown in FIG. 8B during stable lighting (point C in FIG. 7).
The rise of the luminous flux is like a sawtooth wave
In the period when the voltage is late (section AB in FIG. 7), the step-up transformer
Voltage on the secondary side, ie, the lamp voltage V_LaIs low and run
Power W _LaIs large, the straight line as shown in FIG.
It becomes a trapezoidal wave containing many flow components.

For this reason, in the section AB in FIG.
Since the peak value of the lamp current of the lamp rises, the switching loss increases, and the circuit efficiency greatly decreases.In order to reduce the switching loss in this section as much as possible,
It is possible to reduce the resistance of a winding such as a flyback transformer or to use a switching element having a small on-resistance (for example, MO
SFET).

[0007] When used as a vehicle, a traveling beam (high beam) mainly used for forward visibility used during traveling and a low beam (low beam) mainly used for glare control used when there is an oncoming vehicle or on a road with good lighting conditions. ) Requires two light sources, but when both HID lamps are used, the mounting space for the DC / DC converter circuit increases due to the increase in the number of components and the size of the transformer, and the mounting space increases. However, there has been a problem in using it for vehicle mounting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a small and inexpensive discharge lamp lighting device that hastens the rise of a light beam at the time of a cold start.

[0009]

According to the first aspect of the present invention, there is provided a DC / DC converter circuit for boosting a DC voltage of a DC power supply, a discharge lamp, and a DC / DC converter.
A DC power supply has a plurality of discharge lamp lighting sections including an inverter circuit for converting a DC voltage of a converter circuit into an AC voltage and applying the voltage to the discharge lamp, and a discharge lamp starting circuit for applying a pulse voltage to the discharge lamp and starting discharge. Connected in parallel, multiple DC
An auxiliary DC / DC converter circuit is connected in parallel with the DC / DC converter circuit, and the DC / DC converter circuit performs power control of the discharge lamp for starting and stable lighting of the discharge lamp,
When the lamp voltage of the discharge lamp is lower than a predetermined threshold value during the starting process of the discharge lamp, the auxiliary DC / DC converter circuit controls the power of the discharge lamp, and the lamp voltage is not controlled during the starting process. Since the power higher than the rated power can be applied to the discharge lamp while it is lower than the threshold value, the rise of the luminous flux of the discharge lamp can be accelerated. Further, the DC / DC converter circuit and the auxiliary DC / DC converter circuit can be designed in accordance with the lamp voltage mainly operating, so that the circuit efficiency can be improved and the circuit can be downsized.

According to a second aspect of the present invention, in the first aspect of the invention, the ratio of the primary winding to the secondary winding of the step-up transformer provided in the DC / DC converter circuit is determined by the auxiliary DC / D converter.
Since the turn ratio of the primary winding and the secondary winding of the step-up transformer provided in the C converter circuit is made larger,
The turn ratio of the step-up transformer can be set according to the magnitude of the lamp voltage at which the DC converter circuit and the auxiliary DC / DC converter circuit mainly operate.

According to a third aspect of the present invention, in the second aspect, an intermediate tap is provided in a secondary winding of the step-up transformer provided in the DC / DC converter circuit, and an output of the intermediate tap is used as an auxiliary DC / DC converter. As the secondary side output of the step-up transformer of the circuit, the step-up transformer of the DC / DC converter circuit also serves as the step-up transformer of the auxiliary DC / DC converter circuit, so that the number of components can be reduced and the mounting space can be reduced. it can.

According to a fourth aspect of the present invention, in the second or third aspect, the output terminal of the DC / DC converter circuit and the output terminal of the auxiliary DC / DC converter circuit are connected via a diode and a semiconductor switch. When the DC / DC converter circuit and the auxiliary DC / DC converter circuit output a positive potential, the semiconductor switch is a P-channel type MOS.
When the DC / DC converter circuit and the auxiliary DC / DC converter circuit have negative potential outputs, the semiconductor switches are composed of N-channel MOSFETs. Can be realized.

[0013]

Embodiments of the present invention will be described with reference to the drawings. Embodiment 1 FIG. 1 shows a circuit diagram of a discharge lamp lighting device according to this embodiment. The discharge lamp lighting device includes a DC power supply E, a high pressure discharge lamp La ₁ for low beam to be used as a low beam of the light source, a high pressure discharge lamp La ₂ for high beam to be used as the main beam of the light source, the DC power source E First and second DC / DC converter circuits 1 ₁ , 1 ₂ for boosting and controlling lamp power for stable lighting of the high-pressure discharge lamps La ₁ , La ₂ , and first and second DC / DC converters converts the converter circuit 1 _1, 1 ₂ of the DC voltage into an AC voltage the high-pressure discharge lamp L
First and second inverter circuits 2 ₁ and 2 ₂ respectively applied to a ₁ and La ₂ , and a high-voltage pulse voltage is applied to the electrodes of the high-pressure discharge lamps La ₁ and La _{2 when} the discharge lamp is started to start discharging. The first and second igniter circuits 3 ₁ , which are discharge lamp starting circuits to be activated,
3 is equipped with a ₂ and.

[0014] Here, the first DC / DC converter circuit 1 ₁ and the first inverter circuit 2 ₁ and the first igniter circuit 3 ₁ and the first from the high-pressure discharge lamp La ₁ of the discharge lamp lighting unit 5 ₁
There is constructed, configured second DC / DC converter circuit 1 ₂ and the second inverter circuit 2 ₂ and the second igniter circuit 3 ₂ from the high pressure discharge lamp La ₂ of the second and the discharge lamp lighting unit 5 ₂ cage, first and second discharge lamp lighting unit 5 _1, 5 ₂ are connected in parallel to the output terminal of the DC power source E.

The DC power source E is composed of a vehicle-mounted battery, and its voltage value is, for example, about DC12V or about DC24V. Here, the configuration of the _first discharge lamp lighting section 51 will be described. The second discharge lamp lighting unit 5 ₂ configuration is the same as the first discharge lamp lighting unit 5 ₁ configuration, a description thereof will be omitted.

The first DC / DC converter circuit 1 ₁ is made of a flyback converter with a step-up transformer T ₁ and the FETs Q ₁ and diode D ₁ and capacitor C _1,
The primary winding of the step-up transformer T ₁ between both ends of a DC power source E and F
ETQ ₁ is connected in series, and a diode D ₁ and a smoothing capacitor C are connected between both ends of a secondary winding of the step-up transformer T _{1.
And 1} are connected in series. The gate electrodes of FETs Q ₁ inputted ON / OFF signals a from the control circuit 6, the FETs Q ₁ is turned on by the on / off signal a, the DC voltage of the DC power source E is applied to the primary winding of the step-up transformer T ₁ You. At this time, since the diode D ₁ connected to the secondary winding of the step-up transformer T ₁ has the opposite polarity, no current flows through the diode D ₁ , and the energy supplied to the primary winding is reduced by the step-up transformer T 1. Stored in _one . When the FETs Q ₁ by an on / off signal a is turned off, the supply of energy to the primary winding of the step-up transformer T ₁ stops,
Back electromotive voltage is generated in the winding. Therefore, the diode D ₁ on the secondary side conducts, and the energy stored in the step-up transformer T ₁ is released to the secondary side, and charges the smoothing capacitor C ₁ via the diode D ₁ . Thus, the first
The DC / DC converter unit 1 ₁ boosts the DC voltage of the DC power source E, into a high DC voltage for stable lighting of the high pressure discharge lamp La _1.

[0017] The first inverter circuit 2 _1, the first DC
/ DC converter circuit 1 is converted into an AC voltage a DC voltage input from the _1, is applied to the high-pressure discharge lamp La _1, to stable lighting of the high pressure discharge lamp La _1. First igniter circuit 3
_1, when starting the high pressure discharge lamp La _1, a high-voltage pulse voltage is applied to the electrodes of the high pressure discharge lamp La _1, by generating a breakdown in the tube, thereby starting the discharge.

The auxiliary DC / DC converter circuit 4 is also
First and second DC / DC converter circuits 1₁, 1_Twothe same as
And a step-up transformer T_ThreeAnd FETQ_ThreeAnd diode D_ThreeWhen
Capacitor C_ThreeFrom a flyback converter with
And a step-up transformer T between the outputs of the DC power supply E._ThreePrimary volume
Wire and FETQ_ThreeIs connected to the step-up transformer T_ThreeSecondary volume
Diode D between both ends of the wire_ThreeThrough the capacitor for smoothing
C_ThreeIs connected. This auxiliary DC / DC converter
The converter circuit 4 includes the first and second DC / DC converter circuits 1
₁, 1_TwoConnected in parallel with the
Ching element Q_FourAnd diode D for backflow prevention_FourThrough
And the first DC / DC converter circuit 1 ₁Connected to the output end of
And the switching element Q_FiveAnd backflow prevention
Diode D for_FiveThrough the second DC / DC converter
Data circuit 1_TwoOutput terminal.

The control circuit 6 outputs on / off signals a to c to the gate electrodes of the FETs Q _{1 to} Q ₃ in response to the low beam and high beam switching signals S ₁ and S ₂ , and switches the switching elements Q ₄ and Q ₄ . ₅ and outputs on / off signals d and e to the first and second DC / DC converter circuits 1 ₁ and 1 _2.
And the output voltage of the auxiliary DC / DC converter circuit 4 and on / off of the switching elements Q ₄ and Q ₅ .

[0020] Here, the high pressure discharge lamp La ₁ or La ₂ when respectively igniting high-pressure discharge lamp La ₁ in the starting period after activation, of La ₂ lamp voltage V _La1, V _La2 a predetermined threshold value The control circuit 6 controls the switching element Q ₄
Or to turn on the Q _5. During this time, auxiliary DC / DC converter circuit 4 boosts the DC voltage of the DC power source E, through the switching element Q ₄ or Q _5, the first or second DC
/ Supplies power to DC converter circuit 1 _1, 1 ₂ of the output terminals, by advancing the starting time of the high pressure discharge lamp La _1, La _2, have faster rise of the luminous flux.

Incidentally, the step-up transformers T ₁ and T ₁ provided in the first and second DC / DC converter circuits 1 ₁ and 1 ₂ , respectively.
The winding ratios k ₁ (= N _S1 / N _P1 ) and k ₂ (= N _S2 / N _P2 ) of the primary windings N _P1 , N _P2 and the secondary windings N _S1 , N _{S2 of} T ₂ are:
No-load secondary voltage at the time of starting the discharge lamp (for example, 300 to 40
0V) and the high frequency switching elements Q ₁ , Q
₂ , and the winding ratios k ₁ and k ₂ are set to relatively high values. For example, when the DC voltage of the DC power supply E is about 12 V DC and the withstand voltage of the FETs Q ₁ and Q ₂ is about 100 V, the winding ratios k ₁ and k ₂ are set to about 5 to 7. By setting the winding ratios k ₁ and k ₂ to such values, the lamp voltage of the high-pressure discharge lamps La ₁ and La ₂ can be set to 85 V to ₁ during stable lighting.
In a state stable to about 10 V, the first and second DC / D
C converter circuit 1 _1, 1 ₂ of the circuit efficiency can be enhanced most.

On the other hand, the auxiliary DC / DC converter circuit 4
Is a starting process of the high pressure discharge lamp La ₁ The La _2, because their lamp voltage only operate at a relatively low period, the winding ratio of the step-up transformer T ₃ is lower well, the step-up transformer T _1, T
Is set to a value lower than ₂ turns ratio k _1, k _2. That is, the winding ratio k ₃ (= N _S3 / N _P3 ) between the primary winding N _P3 and the secondary winding N _S3 of the step-up transformer T ₃ is expressed by the following equation, where A is a positive constant less than 1. Is done.

K ₃ = Ak ₁ For example, by setting A to about 0.5, the high-pressure discharge lamp L
to a _1, the La ₂ lamp voltage is relatively low period, even when supplying large current to the high pressure discharge lamp La _1, La _2, since the smaller the turns ratio k ₃ of the step-up transformer T _3, boost it is possible to reduce the DC component of the current flowing through the FETs Q ₃ connected to the primary winding of the transformer T _3. This DC component is shown in FIG.
Since the component is an ineffective component as shown in (a), the switching loss can be significantly reduced by reducing the DC component. Therefore, even when the lamp voltages of the high-pressure discharge lamps La ₁ and La ₂ are relatively low, the circuit efficiency of the entire apparatus can be greatly improved.

The operation of this circuit will be described with reference to the time chart of FIG. First, light the high pressure discharge lamp La ₁ for low beam, it will be described for turning off the high-pressure discharge lamp La ₂ for high beam. At time t _1, the control circuit 6 actuates the first DC / DC converter circuit 1 _1, the first inverter circuit 2 ₁ applies an AC voltage to the high pressure discharge lamp La _1, the first igniter circuit 3 ₁
Applies a high-voltage pulse to the electrodes of the high-pressure discharge lamp La ₁ ,
To start discharge of the high-pressure discharge lamp La _1.

In the starting process after the start-up, the lamp voltage V _La1 becomes low because the metal vapor pressure in the tube of the high pressure discharge lamp La ₁ is low, and the lamp voltage V _La1 becomes a predetermined threshold value (for example, a 35 W metal halide lamp). When the period shifts to a period lower than about 50 V (period t ₂ -t _{3 in} FIG. 2),
The control circuit 6 with activates the auxiliary DC / DC converter circuit 4, by turning on the switching element Q _4, the auxiliary DC / DC converter circuit 4 first inverter circuit 2 ₁ and the first igniter circuit 3 ₁ It is allowed to supply power to the high-pressure discharge lamp La ₁ through. At this time, the high-pressure discharge lamp La ₁
Is supplied to the first DC / DC converter circuit 11 ₁
And the auxiliary DC / DC converter circuit 4.
As shown in FIG. 2, the lamp voltage V _La1 of the high-pressure discharge lamp La ₁
Decreases once after startup and then increases gradually. The control circuit 6 controls the auxiliary DC voltage as the lamp voltage V _La1 increases.
/ Voltage of the DC converter circuit 4 is lowered gradually, the lamp voltage V _La1 at time t ₃ is greater than a predetermined threshold value, the operation of the auxiliary DC / DC converter circuit 4 is stopped, the switching element Q ₄ Off.

Therefore, the lamp voltage V _La1 of the high-pressure discharge lamp La ₁ becomes larger than a predetermined threshold value, for example, about 8
When a stable lighting state of 5 V is attained, the first D including the step-up transformer T ₁ whose turn ratio is optimized at the output voltage is provided.
Only C / DC converter circuit 1 ₁ is supplying power to the high-pressure discharge lamp La _1, since the light the high pressure discharge lamp La _1, during stable lighting, it is possible to improve the overall circuit efficiency.

Next, the turn off the high-pressure discharge lamp La ₁ for low beam from the lighting will describe a case where switching to light the high pressure discharge lamp La ₂ for high beam from off. At time t _4, the control circuit 6 operates the second DC / DC converter circuit 1 _2, together with the second inverter circuit 2 ₂ applies an AC voltage to the high-pressure discharge lamp La _2, the second igniter circuit 3 ₂ by applying a high-voltage pulse across the high-pressure discharge lamp La _2, to start the discharge of the high-pressure discharge lamp La _2.

High pressure discharge lamp La_TwoIn the starting process after startup
And the lamp voltage V_La2Is a predetermined threshold (for example,
(About 50V for 35W metal halide lamp)
Low period (period t in FIG. 2)_Five -T₇ ), The time
t_FiveIn the control circuit 6, the auxiliary DC / DC converter
Operating the switching circuit 4 and the switching element Q _Five
Turn on. At this time, the auxiliary DC / DC converter circuit
4 to the second inverter circuit 2_TwoAnd the second igniter
Circuit 3_TwoThrough the high-pressure discharge lamp La_TwoPower is supplied to the
2 DC / DC converter circuit 1_TwoAnd auxiliary DC / DC
The converter circuit 4 is a high-pressure discharge lamp La_TwoSharing power supply to
Do it.

At time t ₆ , the high-pressure discharge lamp L for high beam
When the light flux of a ₂ is sufficiently bright, the control circuit 6 stops the operation of the DC / DC converter circuit 1 ₁ by the first ON / OFF signals a, turns off the high-pressure discharge lamp La ₁ for low beam. Further, the control circuit 6, together with the lamp voltage V _La2 of the high pressure discharge lamp La ₂ rises, lowering the voltage of the auxiliary DC / DC converter circuit 4 gradually, the threshold ramp voltage V _La2 is given at time t ₇ becomes larger than the value, the operation of the auxiliary DC / DC converter circuit 4 is stopped to turn off the switching element Q _5.

The lamp voltage V of the high-pressure discharge lamp La _2
La2 exceeds a predetermined threshold value, for example, about 8
When a stable lighting state of 5V, a second D comprising a step-up transformer T ₂ which turns ratio is optimized at its output voltage
Only C / DC converter circuit 1 ₂ turns on to supply power to the high-pressure discharge lamp La _2. As described above, when it is not necessary to simultaneously start and start a plurality of high-pressure discharge lamps and a starting process after startup, the DC / DC converter circuit that supplies power to each of the high-pressure discharge lamps at startup and during stable lighting is connected to each high-pressure discharge lamp. An auxiliary DC / DC converter circuit, which is provided for each lamp and supplies power to accelerate the rise of the luminous flux when the lamp voltage is lower than a predetermined threshold value in the process of starting the high pressure discharge lamp, is provided for each D.
At least one is provided in parallel with the C / DC converter circuit. And a DC / DC converter circuit and an auxiliary DC
By setting the winding ratio of the step-up transformer as described above in accordance with the lamp voltage of the high-pressure discharge lamp in which the / DC converter circuit mainly operates, the circuit efficiency of both converter circuits can be improved. Further, the design of each converter circuit can be optimized according to each lamp voltage, and the size of the switching element and the step-up transformer can be reduced.

In this embodiment, the first and second DCs
Although the flyback converter is used for the DC / DC converter circuits 1 ₁ and 1 ₂ and the auxiliary DC / DC converter circuit 4, the present invention is not limited to the flyback converter, but includes a step-up chopper circuit or a step-up / down converter other than the flyback converter. A pressure chopper circuit may be used. Although a battery is used as the DC power supply E, the invention is not limited to the battery, and the DC power supply E may be configured by rectifying and smoothing an AC power supply. (Embodiment 2) FIG. 3 is a circuit diagram of a discharge lamp lighting device according to this embodiment.

In the present embodiment, in the discharge lamp lighting device of the first embodiment, the boosting transformers of the first and second DC / DC converters also serve as the boosting transformers of the auxiliary DC / DC converter circuit. The first DC / DC converter circuit 1 ₁ is provided with a step-up transformer PT ₁ in which the intermediate tap pt ₁ is provided on the secondary side, the FETs Q ₁ connected in series with the primary winding of the step-up transformer PT _1, the step-up transformer It comprises a diode D ₁ and a smoothing capacitor C ₁ connected in series between the secondary windings of PT ₁ .

Further, the first auxiliary DC / DC converter circuit 4 ₁ series between a ground side end of the intermediate tap pt ₁ provided on the secondary side of the step-up transformer PT ₁ and the secondary winding consists diode connected D ₆ and a smoothing capacitor C _5, a first DC / DC converter circuit 1 ₁ of the step-up transformer PT _1, also serves as a first auxiliary DC / DC converter circuit 4 ₁ of the step-up transformer I have. Its output via a diode D ₉ and the switching element Q ₇ for backflow prevention is connected to a connection point between the diode D ₂ and capacitor C _2. And the high-pressure discharge lamp L for high beam
the startup process after activation of a _2, while the lamp voltage V _La2 is lower than a predetermined threshold, in order to shorten the rise of the light flux, the control circuit 6 turns on the switching element Q _7, the auxiliary DC / DC converter circuit 4 ₁ 1 to the auxiliary power supply to the high pressure discharge lamp La ₂ in.

[0034] Similarly, the second DC / DC converter circuit 1 ₂ includes a step-up transformer PT ₂ to the intermediate tap pt ₂ is provided on the secondary side, which is connected in series with the primary winding of the booster transformer PT ₂ and FETs Q _2, comprised of series connected diodes D ₂ and capacitor C ₂ Metropolitan for smoothing between the output terminal of the secondary side of the step-up transformer PT _2. On the other hand, the second auxiliary D
C / DC converter circuit 4 _2, diodes connected in series D ₇ and a smoothing capacitor between the ground side end of the intermediate tap pt ₂ provided on the secondary winding of the step-up transformer PT ₂ and the secondary winding C ₆ and the second DC /
DC converter circuit 1 in the _second step-up transformer PT ₂ also serves as a second step-up transformer auxiliary DC / DC converter circuit 4 _2. Its output terminal is connected to a diode D ₁ via a switching element Q ₆ and a diode D ₈ for backflow prevention.
And it is connected to a connection point between the capacitor C _1. Then, the startup process after activation of the low-beam high-pressure discharge lamp La _1, while the lamp voltage V _La1 is lower than a predetermined threshold, in order to shorten the rise time of the light flux, the control circuit 6 switching element the Q ₆ is turned on, thereby assisting the power supply to the high pressure discharge lamp La ₁ to the second auxiliary DC / DC converter circuit 4 _2.

[0035] In addition, the first inverter circuit 3 _1, FE
Constructed from the full-bridge inverter circuit composed of _{TQ 8 ~Q 11, FETQ 8 ~Q} 11 is turned on / off at a high frequency by an on / off signal h ₁ to h ₄ of the control circuit 6, first
A DC / DC converter 1 ₁ DC voltage is converted into high-frequency AC voltage is applied to the high-pressure discharge lamp La ₁ for low beam. Similarly, the second inverter circuit 3 _2, FETs Q
₁₂ is constructed from the full-bridge inverter circuit composed of to Q _15, FETs Q ₁₂ to Q ₁₅ is turned on / off at a high frequency by an on / off signal i ₁ through i ₄ of the control circuit 6, the second D
Converts the DC voltage of the C / DC converter circuit 1 ₂ in the high-frequency AC voltage is applied to the high-pressure discharge lamp La ₂ for high beam.

Here, when the high-pressure discharge lamp La ₁ or La ₂ is stably lit, the first and second DC / DC converter circuits 1 ₁ and 1 ₂ are connected to the _secondary of the step-up transformers PT ₁ and PT ₂ . The power is supplied to the smoothing capacitors C ₁ and C ₂ via the flywheel diodes D ₁ and D ₂ connected to the side. On the other hand, in the starting process after starting the high-pressure discharge lamps La ₁ and La ₂ , while the lamp voltage is lower than the predetermined threshold value, the control circuit 6 turns on the switching element Q ₇ or Q ₆ to turn on the second element. or the first from the auxiliary DC / DC converter circuit 4 _2, 4 _1, the first or second inverter circuit 2 _1, 2 ₂ respectively to the voltage supply to the.

Assuming that the number of turns of the primary windings of the step-up transformers PT ₁ and PT ₂ is Np ₄ and the number of turns of the secondary windings is Ns ₄ and Ns ₅ , the turn ratio k ₄ is k ₄ = (Ns ₄ + Ns ₅ ) / Np ₄ , which is determined by the no-load secondary voltage at start-up and the withstand voltage of the primary-side high-frequency switching elements Q ₁ and Q _2.
4 needs to be relatively large. In addition, the first and second
In the auxiliary DC / DC converter circuits 4 ₁ and 4 ₂ , the intermediate taps pt ₁ and pt ₁ provided on the secondary side of the step-up transformers PT ₁ and PT ₂
The winding ratio k ₅ (= Ns ₅ / Np ₄ ) between pt ₂ and ground is represented by k
₅ = Bk ₄ (where B is a positive constant less than 1)
Is smaller than the first and second DC / DC converter circuit 1 _1, 1 ₂ of the step-up transformer PT _1, the turns ratio k ₄ of PT _2. By setting B = 0.5, for example, the FETs Q ₁ , Q ₂ connected to the primary windings of the step-up transformers T ₁ , T ₂
The DC component of the current flowing through ₂ can be reduced. Since this DC component is an ineffective component as shown in FIG. 8A, the switching loss can be greatly reduced by reducing this DC component. Therefore, even when the lamp voltages of the high-pressure discharge lamps La ₁ and La ₂ are relatively low, the circuit efficiency of the entire apparatus can be greatly improved.

The operation of the discharge lamp lighting device will be described with reference to the time chart of FIG. First, the lighting high pressure discharge lamp La ₁ for low beam, a case will be described in which the high-pressure discharge lamp La ₂ for high beam is turned off. At time t _11, the control circuit 6 actuates the first DC / DC converter circuit 1 _1, the first inverter circuit 2 ₁ a first DC / DC converter circuit 1 ₁ DC voltage a high frequency alternating voltage conversion to the well as applied to the high-pressure discharge lamp La _1, the first igniter circuit 3 ₁ by applying a high-voltage pulse voltage to the electrodes of the high pressure discharge lamp La _1, to start the discharge.

[0039] In the starting process after startup of the high pressure discharge lamp La _1, the lamp voltage V _La1 is lowered, a predetermined threshold (e.g., in the case of 35W metal halide lamp of about 50
After shifting to lower period than (period t ₁₂ ~t ₁₃ in FIG. 4) V), the control circuit 6 actuates the second DC / DC converter circuit 1 _2, turns on the switching element Q _6. The second is auxiliary DC / DC converter circuit 4 _2, through the switching element Q ₆ and the diode D _8, supplies power to the first inverter circuit 2 _1.
At this time, we perform a first DC / DC converter circuit 1 ₁ and the second auxiliary DC / DC converter circuit 4 ₂ by sharing the power supply of the first to the inverter circuit 2 _1.

In the starting process after starting the high-pressure discharge lamp La ₁ ,
As shown in FIG. 4, the lamp voltage V _{La 1} once decreases and then gradually increases, so that the control circuit 6
_La1 with the boosting of, reducing the second voltage of the auxiliary DC / DC converter circuit 4 ₂ gradually. And time t
When the lamp voltage V _La1 is greater than a predetermined threshold value at _13, the control circuit 6 turns off the switching element Q _6,
Stopping the power supply from the second auxiliary DC / DC converter circuit 4 ₂ to the first inverter circuit 2 _1. At this time, the high pressure discharge lamp La ₁ is turned stabilized only by the first DC / DC converter circuit 1 ₁ of the output voltage.

Next, the off the high pressure discharge lamp La ₁ for low-beam from the lighting, the case where the high-pressure discharge lamp La ₂ for high beam is switched from off to the lighting. Time t
_{At 14} , the control circuit 6 sets the second DC / DC converter circuit 1
Actuation _2, as well as applied to the high-pressure discharge lamp La ₂ and the second inverter circuit 2 ₂ converts the second DC voltage of the DC / DC converter circuit 1 ₂ in the high-frequency AC voltage,
The second igniter circuit 3 ₂ to start discharge by applying a high-voltage pulse voltage to the electrodes of the high pressure discharge lamp La _2.

In the starting process after the start of the high-pressure discharge lamp La ₂ , when the lamp voltage V _La2 shifts to a period during which the lamp voltage V _La2 is lower than a predetermined threshold (period t _{15 to} t _{17 in} FIG. 4), the control circuit 6 by turning on the switching element Q _7, the first auxiliary DC /
To supply power to the second inverter circuit 2 ₂ DC converter circuit 4 ₁ via a diode D ₉ and the switching element Q _7, it is made to shorten the rise time of the luminous flux of the high-pressure discharge lamp La _2.

[0043] In the starting process of the high-pressure discharge lamp La _2, when at time t ₁₆ is lighted state of the high-pressure discharge lamp La ₂ substantially stable, the control circuit 6 stops the operation of the first inverter circuit 2 _1, high pressure the discharge lamp La ₁ turns off. Further, at time t ₁₇
In the lamp voltage V _La2 is greater than a predetermined threshold value, the control circuit 6 turns off the switching element Q _7, stops the operation of the first DC / DC converter circuit 1 _1, the second DC / DC converter circuit 1 ₂ only a high pressure discharge lamp La ₂ stabilize illuminated.

As described above, in a discharge lamp lighting device for lighting multiple high-pressure discharge lamps that do not need to be started simultaneously from start-up, a DC for supplying power at start-up and stable lighting is provided.
A DC / DC converter circuit for each high-pressure discharge lamp, and at least one auxiliary DC / DC converter circuit for supplying power to accelerate the rise of the luminous flux while the lamp voltage is lower than a predetermined threshold value during the starting process. To each D
It is provided in parallel with the C / DC converter circuit. And
By setting the winding ratio of the step-up transformer as described above in accordance with the lamp voltage of the high-pressure discharge lamp in which the DC / DC converter circuit and the auxiliary DC / DC converter circuit mainly operate, the circuit efficiency of both converter circuits is obtained. And the design of the DC / DC converter circuit and the auxiliary DC / DC converter circuit can be optimized according to each lamp voltage, and the size of the switching element and the step-up transformer can be reduced.

In this embodiment, the first and second D
C / DC converter circuit 1 _1, 1 ₂ of the step-up transformer PT _1, PT
₂ , the step-up transformers of the first and second auxiliary DC / DC converter circuits 4 ₁ and 4 ₂ are also used, so that the number of components can be reduced and the circuit can be downsized, and the circuit can be mounted. Space can be reduced. In this embodiment,
The switching time the high-pressure discharge lamp La ₂ of the high pressure discharge lamp La ₁ and a high beam low beam, although either is performing control to always lit, in the absence of the need, first
Can the DC / DC converter circuit 1 ₁ and the first inverter circuit 2 _1, the second DC / DC converter circuit 1 ₂ and the second timing of the operation of the inverter circuit 2 ₂ synchronization,
Also, power control can be simplified.

The first and second inverter circuits 3₁, 3
_TwoAnd first and second auxiliary DC / DC converter circuits 4
₁, 4_TwoThe other configuration is the same as that of the first embodiment.
Description is omitted. (Embodiment 3) In this embodiment, the discharge lamp point of Embodiment 2 is used.
In the lighting device, as shown in FIG.
C / DC converter circuit 1₁, 1_TwoOutput is positive potential,
First auxiliary DC / DC converter circuit 4₁Output end of
Is replaced with a P-channel MOSFET Q₇
And diode D for backflow prevention₉Through the diode
D _TwoAnd capacitor C_TwoConnected to the connection point with the second auxiliary
DC / DC converter circuit 4_TwoSwitch the output end of
P-channel MOSFET Q₆And backflow prevention
Diode D for₈Through the diode D₁And conde
Sensor C₁Is connected to the connection point.

[0047] between the gate and source of FETQ ₇ resistance R
₁ is connected, between the gate and ground of FETs Q _7, a resistor R ₂ and the transistor Q ₁₆ and the resistor R ₃ are connected in series. In addition, the base of the transistor Q ₁₆ is,
It is connected to a ground line via a Zener diode ZD ₁ and to a control circuit 6 via a resistor R ₄ . A resistor R ₅ is connected between the gate and source of the FET Q _6.
There are connected, between the gate and ground of FETs Q _6, and the resistor R ₆ and the transistor Q ₁₇ and the resistor R ₇ is connected in series. In addition, the base of the transistor Q ₁₇ is,
Is connected to the ground line via a Zener diode ZD _2, it is connected to the control circuit 6 through the resistor R _8.

The operation of this circuit is shown in the time chart of FIG.
This will be described below. High-pressure discharge lamp La for low beam₁Is off
And high-pressure discharge lamp La for high beam_TwoIs lit
Will be explained. High-pressure discharge in the same manner as in the first or second embodiment.
Light La_TwoLamp voltage V during the starting process after starting_La2Place
Faster rise of luminous flux while below a certain threshold
Therefore, the control circuit 6 switches the switching element Q₇Turn on
And the second DC / DC converter circuit 1_TwoAnd the first aid
DC / DC converter circuit 4 ₁And the second inverter
Circuit 2_TwoTo supply power.

Time t_{twenty one}Then, the control circuit 6 sets the resistance R_FourTo ha
Drive signal DR of level (H)_TwoOutput
Jista Q₁₆Is the Zener diode ZD₁
Zener voltage V_ZD1Is clamped to. At this time,
Transistor Q₁₆Emitter current I_EIs given by
It will be fixed. I_E= (V_ZD1-V_BE) / R_Three Where V_BEIs the transistor Q₁₆Base-emitter current
Pressure, R_ThreeIs the resistance R_ThreeIs the resistance value. Where the transi
Star Q₁₆Collector current I_CIs the emitter current I _EAnd abbreviation
(I_C≒ I_E), FETQ₇Gate source
Between the gate-source voltage V expressed by the following equation_GSIs applied
And FET Q₇Turns on.

V _GS = −I _C × R ₁ ≒ −I _E × R ₁ = −
When _{(V ZD1 -V BE) × R} 1 / R 3 FETQ 7 is turned on, the first output terminal of the auxiliary DC / DC converter 4 _1, FETs Q ₇ and a diode D ₉
Through, is connected to a connection point between the diode D ₂ and the capacitor C _2, it is possible to supply electric power from the first auxiliary DC / DC converter 4 ₁ to the second inverter circuit 2 _2.

Then, at time t_{twenty two}Then, the control circuit 6
Bell (L) drive signal DR_TwoIs the resistance R_FourOutput to
FETQ₇Turns off and the first auxiliary DC / DC converter
TA4 ₁To the second inverter circuit 2_TwoPower supply to
Is stopped. Note that the second auxiliary DC / DC converter 4
_TwoThe operation of the first auxiliary DC / DC converter 4₁of
Since the operation is the same as that of the first embodiment, the description is omitted.

As described above, using the P-channel MOSFETs Q ₆ and Q ₇ as the switching elements, the FETs Q ₆ and Q ₇
Is driven at a constant current, so that a switching circuit for switching elements Q ₆ and Q ₇ can be realized with a relatively simple circuit configuration. In the present embodiment, the first and second DC
Although the outputs of the DC / DC converter circuits 1 ₁ and 1 ₂ and the first and second auxiliary DC / DC converter circuits 4 ₁ and 4 ₂ have a positive potential, the first and second DC / DC converter circuits 11 ₁ , 1
₂ and first and second auxiliary DC / DC converter circuits 4
_1, 4 ₂ If the output is a negative potential, the switching element Q _6,
Using N-channel MOSFET as Q _7, it is sufficient to connect the diode D _8, D ₉ in the opposite direction, in the same simple circuit configuration, it is possible to realize a switching circuit of the switching element Q _6, Q _7.

The configuration and operation of the switching elements Q ₆ and Q ₇ other than the operation circuit are the same as those in the first or second embodiment, and a description thereof will be omitted.

[0054]

According to the first aspect of the present invention, as described above, the DC / DC converter circuit for boosting the DC voltage of the DC power supply, the discharge lamp, and the DC / DC converter circuit for converting the DC voltage to an AC voltage. A plurality of sets of discharge lamp lighting sections, each of which comprises an inverter circuit for applying a pulse voltage to the discharge lamp and a discharge lamp starting circuit for starting discharge by applying a pulse voltage to the discharge lamp, are connected in parallel to a DC power supply, and a plurality of DC / DC An auxiliary DC / DC converter circuit is connected in parallel with the converter circuit,
A DC converter circuit controls the power of the discharge lamp for starting and stable lighting of the discharge lamp, and when the lamp voltage of the discharge lamp is lower than a predetermined threshold value in the process of starting the discharge lamp, the auxiliary DC / DC The converter circuit controls the power of the discharge lamp, and during the starting process, while the lamp voltage is lower than the predetermined threshold value, it is possible to apply power equal to or higher than the rated power to the discharge lamp. There is an effect that the rise can be hastened. Further, each circuit can be designed in accordance with the lamp voltage at which the DC / DC converter circuit and the auxiliary DC / DC converter circuit mainly operate,
There is also an effect that the circuit efficiency can be improved and the circuit can be downsized.

According to a second aspect of the present invention, the ratio of the primary winding to the secondary winding of the step-up transformer provided in the DC / DC converter circuit is determined by changing the turn ratio of the step-up transformer provided in the auxiliary DC / DC converter circuit. Since the turn ratio of the primary winding and the secondary winding is larger than that of the step-up transformer, the DC / DC converter circuit and the auxiliary DC / DC converter circuit mainly operate according to the magnitude of the lamp voltage. There is an effect that the winding ratio can be set and the circuit efficiency can be further improved.

According to a third aspect of the present invention, an intermediate tap is provided in a secondary winding of a step-up transformer provided in the DC / DC converter circuit, and the output of the intermediate tap is used as a secondary of the boost transformer in the auxiliary DC / DC converter circuit. DC / DC as side output
Since the boosting transformer of the converter circuit also serves as the boosting transformer of the auxiliary DC / DC converter circuit, the number of components can be reduced and the mounting space can be reduced.

According to a fourth aspect of the present invention, the output terminal of the DC / DC converter circuit and the output terminal of the auxiliary DC / DC converter circuit are connected via a diode and a semiconductor switch, and the DC / DC converter circuit and the auxiliary DC / DC
When the converter circuit has a positive potential output, the semiconductor switch is composed of a P-channel MOSFET, and when the DC / DC converter circuit and the auxiliary DC / DC converter circuit have a negative potential output, the semiconductor switch is an N-channel MOS.
Since it is composed of FETs, there is an effect that a switching circuit of a semiconductor switch can be realized with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a discharge lamp lighting device according to a first embodiment.

FIG. 2 is a time chart showing the operation of the above.

FIG. 3 is a circuit diagram showing a discharge lamp lighting device according to a second embodiment.

FIG. 4 is a time chart showing the operation of the above.

FIG. 5 is a circuit diagram illustrating a discharge lamp lighting device according to a third embodiment.

FIG. 6 is a time chart showing the operation of the above.

FIG. 7 is a diagram showing a relationship between a lamp voltage and a lamp power at the time of starting according to the first embodiment;

FIG. 8 is a waveform diagram showing a lamp current according to the first embodiment;

[Explanation of symbols]

Reference Signs List 1 ₁ first DC / DC converter circuit 2 ₁ first inverter circuit 4 auxiliary DC / DC converter circuit 6 control circuit D ₄ diode E DC power supply La _al high-pressure discharge lamp Q ₄ switching element

Claims (4)

[Claims] A DC / DC boosting a DC voltage of a DC power supply.
A converter circuit, a discharge lamp, an inverter circuit for converting a DC voltage of the DC / DC converter circuit into an AC voltage and applying the AC voltage to the discharge lamp, and a discharge lamp for applying a pulse voltage to the discharge lamp to start discharge A plurality of sets of discharge lamp lighting sections each including a starting circuit are connected to the DC power supply in parallel, and an auxiliary DC / D is connected in parallel with the plurality of DC / DC converter circuits.
A C / C converter circuit is connected, and the DC / DC converter circuit controls the power of the discharge lamp for starting and stable lighting of the discharge lamp, and the lamp voltage of the discharge lamp is set to a predetermined value during the process of starting the discharge lamp. The discharge lamp lighting device, wherein the auxiliary DC / DC converter circuit controls the power of the discharge lamp when the voltage is lower than a threshold value. 2. A primary winding of a step-up transformer provided in the auxiliary DC / DC converter circuit, wherein a winding ratio between a primary winding and a secondary winding of the step-up transformer provided in the DC / DC converter circuit is determined. The discharge lamp lighting device according to claim 1, wherein the turn ratio is larger than the turn ratio of the secondary winding. 3. A booster transformer provided in said DC / DC converter circuit is provided with an intermediate tap in a secondary winding thereof, and an output of said intermediate tap is output to a secondary side output of said booster transformer of said auxiliary DC / DC converter circuit. 3. The discharge lamp lighting device according to claim 2, wherein the step-up transformer of the DC / DC converter circuit also serves as the step-up transformer of the auxiliary DC / DC converter circuit. 4. An output terminal of the DC / DC converter circuit and an output terminal of the auxiliary DC / DC converter circuit are connected via a diode and a semiconductor switch.
The DC / DC converter circuit and the auxiliary DC / D
When the C converter circuit outputs a positive potential, the semiconductor switch is constituted by a P-channel type MOSFET,
4. The discharge lamp lighting device according to claim 2, wherein when the C / DC converter circuit and the auxiliary DC / DC converter circuit output a negative potential, the semiconductor switch is configured by an N-channel MOSFET.