JPH07192878A - Lighting circuit device of high-luminance discharge lamp for automobile - Google Patents

Abstract

PURPOSE:To restrict the influence of the temperature to the peak voltage of high-tension pulse voltage required for the time of starting the lighting of a discharge lamp at minimum by using resonance circuits in a lighting circuit device of a high-luminance discharge lamp for automobile. CONSTITUTION:In a lighting device, a resonance frequency f1 of a parallel resonance circuit to be decided by a high-tension pulse transformer 24 and a capacitor 25 and a resonance frequency f2 of a series resonance circuit to be decided by an inductor 23 and a capacitor 28 are set so as to satisfy 'f1=f2'. A lighting circuit, which can restrict a change of the peak voltage of the high- tension pulse voltage in relation to the all temperature range at minimum, can be thereby obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-intensity discharge lamp lighting circuit device for automobiles.

[0002]

2. Description of the Related Art In recent years, automobile designs tend to be more streamlined, and accordingly, compact headlights are required. However, when the headlight is made compact, the light collection efficiency of the lamp decreases, so a light source with higher efficiency and higher brightness than the conventional halogen bulb is required,
A system using a high-intensity discharge lamp has been developed as a next-generation headlight that satisfies these conditions. This high-intensity discharge lamp system is composed of an ultra-compact metal halide lamp in which a rare gas, mercury, and a metal halide as a luminescent substance are enclosed in an arc tube made of quartz glass, and a lighting circuit.

FIG. 5 shows a circuit block diagram of a conventional example, and its operation will be described. Reference numeral 1 is a DC power supply provided in an automobile and normally supplies a DC voltage of 9 to 16V. A high-intensity discharge lamp lighting circuit device for automobiles (hereinafter referred to as a lighting circuit device) 2 is connected to the DC power source 1 via a lamp lighting switch 3 and controls the lighting of the discharge lamp 4. The lighting circuit device 2 includes a DC / DC converter 21 that outputs a boosted DC voltage to the power source voltage of the DC power source 1, and a polarity changeover switch circuit 22 that converts the boosted DC voltage boosted by the DC / DC converter 21 into AC. A polarity changeover switch circuit 22 is provided on the secondary side that initially generates a high voltage for lighting the discharge lamp 4, and the boosted DC voltage end of the DC / DC converter 21 and the inductor 23 having an air-core structure are provided on the primary side. High-voltage pulse transformer 24 connected
When a switching signal is applied to the capacitor 25 connected to both ends of the primary winding of the high voltage pulse transformer 24 and the FET 26 connected to the other end of the inductor 23, the starting circuit 27
, A capacitor 28 connected between the drain and source of the FET 26, the DC / DC converter 21, and the starting circuit 2
It comprises a control circuit 29 which controls 7 and provides appropriate lighting for the vehicle headlights.

Next, the operation of the above-mentioned conventional high-intensity discharge lamp lighting circuit device for an automobile will be described. The direct current power supply 1 for an automobile usually has an output voltage of 9 to 16 V and is used as a power supply for an electronic circuit device of an automobile. The lighting circuit device 2 also uses the DC power source 1 as a power source, and turns on / off the lighting switch 3 to turn on / off the discharge lamp 4.

First, when the lighting switch 3 is turned on, a DC voltage is supplied to the control circuit 29 of the lighting circuit device 2, and a standby state of a series of control operations from a state where the discharge lamp 4 is turned off to a stable lighting. Is secured. In order for the discharge lamp 4 to light up, it is first necessary to apply a high voltage between the discharge terminals inside the discharge lamp 4 to shift to arc discharge. In order to boost the input DC voltage 9 to 16V to a high voltage, the DC / DC converter 21 is controlled by the start control circuit 26, and the output terminal of the DC / DC converter 21 is boosted to obtain about DC220V.

Next, in order to obtain a high-voltage pulse voltage of about 15 kV between the discharge terminals of the discharge lamp 4, the voltage supply line connected from the boost DC voltage side of the output end of the DC / DC converter 21 is connected to the primary of the high-voltage pulse transformer 24. Connect to the side, FET
When 26 is turned on, energy is stored in the inductance of the primary winding of the high-voltage pulse transformer 24, and when sufficient energy is stored, the FET 26 is turned off to release the energy stored in the primary side inductance to the secondary side. . With this, the high voltage pulse transformer 24
Discharge lamp 4 connected in series between the two secondary windings of
A high-voltage pulse voltage having a peak voltage of 15 kVP-P is generated between the discharge terminals of. At this time, ON / O of FET 26
The FF is controlled by the starting circuit 27. The control circuit 29 performs control up to the generation of a series of high-voltage pulse voltages, and controls the boosted DC voltage of the DC / DC converter 21 and the operation start / stop of the start circuit 27. The start-up circuit 27 receives the operation start signal from the control circuit 29, so that
An ON signal with a pulse width of about 1.5 μs at a frequency of 0 kHz is F
Give to the gate of ET26. This signal causes FET2
6 performs a switching operation, and energy is transmitted by the high-voltage pulse transformer 24 based on the principle described above.

Next, when a signal for stopping the operation is given from the control circuit 29, the starting circuit 27 stops the operation and the FET2
6 also stops operating. Therefore, the high voltage pulse transformer 2
There is no energy transfer at 4. O of starting circuit 27
A voltage exceeding 1000 V is applied as a peak voltage between the drain and source of the FET 26 by the N / OFF control, but there is no FET that guarantees a voltage exceeding 1000 V.
We are implementing ET protection measures. Next, when the discharge phenomenon of the discharge lamp 4 starts due to the high-voltage pulse voltage and a path for electrons to flow is created inside the discharge lamp 4, the impedance of the discharge lamp 4 sharply decreases and a current easily flows.

In this process, the polarity changeover switch circuit 2 connected to the output terminal of the DC / DC converter 21.
An alternating current is supplied to the discharge lamp 4 via 2. However, the alternating voltage is applied to the discharge lamp 4 as a bias from the polarity changeover switch circuit 22 before the high voltage pulse voltage is applied.

Next, in a state where the discharge lamp 4 has reached an arc discharge, the temperature of the discharge tube of the discharge lamp 4 gradually rises with time, and the impedance of the discharge lamp 4 is increased by the emission of the gas enclosed in the discharge lamp 4. Although rising, the electric power of the discharge lamp 4 is controlled in order to control the stable luminous flux in the control circuit 29.

In the headlight system for automobiles, it is required to shorten the time to reach a stable luminous flux as much as possible. Therefore, at the time of starting the lighting, about twice as much electric power as that at the time of stable lighting is supplied until the discharge lamp 4 becomes stable. A large amount of current will flow through the discharge lamp 4. When the discharge lamp 4 is stable in temperature, the discharge lamp is controlled with a constant power of about 35 W as power control. When the discharge lamp 4 that has been turned on is turned off and turned on again for a short time (about 1 to 30 seconds), a means for changing the control at the time of lighting start depending on the time when the discharge lamp 4 is turned off is used.

Next, a part of a specific circuit of the lighting circuit device 2, the high-voltage pulse transformer 24, the discharge lamp 4, the capacitor 25, the capacitor 28, the FET 26, the inductor 23, and the voltage waveforms and currents of the respective parts. Figure 7 showing the waveform
~ With reference to FIG. 13, the lighting mechanism of the discharge lamp 4 will be described in more detail. FIG. 6 shows a part of the polarity changeover switch circuit 22 and a high voltage pulse transformer 24.
, Discharge lamp 4, condenser 25, condenser 2
8 is a specific circuit diagram of 8, FET 26, and inductor 23. FIG. Reference numeral 211 is a flyback transformer, 212 is a diode, and 213 is a capacitor, which is a circuit on the secondary side of the DC / DC converter 21 in the flyback system. The AC voltage switched on the primary side of the flyback transformer 211 and boosted to the secondary side is rectified by the diode 212 and the capacitor 213, and V _DC1 is output to the cathode side of the diode 212 as the boosted DC voltage. Two
_{Reference numeral} 21 is a diode, which applies a voltage V _DC2 to the cathode side. 222 to 225 are FETs and are configured as a full bridge circuit, and the drains of the FETs 222 and 224 are V
The source of the FET 222 is connected to the drain of the FET 223 and the secondary winding terminal 241 of the high-voltage pulse transformer 24 to _DC2 , and the source of the FET 224 is similarly the FET 225.
And the secondary winding terminal 244 of the high voltage pulse transformer 24. The sources of FETs 223 and 225 are both connected to GND. FET 222 to 22
An ON / OFF signal as shown in FIG. 7 is input to the gate of the FET 5, and the FET 222, the FET 225, and the FET 2 are input.
23 and FET 224 perform the same ON / OFF operation, and FE
T222, 225 and FETs 223, 224 turn on each other
/ OFF operation works in reverse. As a result, an AC voltage is applied to the discharge lamp 4 connected to the secondary terminals 242 and 243 of the high voltage pulse transformer 24.

FIG. 8 shows the relationship between the voltage applied to the gate of the FET 26 and the high voltage pulse voltage applied between the discharge terminals of the discharge lamp 4. A high-voltage pulse voltage is repeatedly applied between the discharge terminals of the discharge lamp 4 at a frequency of about 40 kHz from the time the discharge lamp 4 goes out to the time of arc discharge. The energy stored in the primary-side inductance of the high voltage pulse transformer 24 when the drain and source of the FET 26 are in a conductive state is used as a high voltage pulse voltage after the drain and source of the FET 26 are in an open state, and the discharge terminal of the discharge lamp 4. This voltage waveform is applied between the high voltage pulse transformer 24 and the capacitor 2.
It appears as the resonance waveform of the parallel resonance circuit determined by 5.
As described above, the headlight system for automobiles is required to shorten the time required to reach a stable luminous flux as much as possible. For that purpose, it is desirable that the time from the extinguished state of the discharge lamp 4 to the arc discharge is as short as possible, and it is necessary to transfer more energy to the discharge lamp 4 in a short time. Here, the capacitor 25 plays a role of lowering the resonance frequency seen from the primary side of the high-voltage pulse transformer 24, whereby 15 k
The half-wave time for which the peak voltage of the high-voltage pulse voltage of VP-P is applied becomes longer, and more energy can be given to the discharge terminals of the discharge lamp 4, and the discharge lamp 4
This contributes to the reduction of the time from the turning off to the arc discharge. Furthermore, the whole temperature range (-40 ℃ -85 ℃)
It is desirable that the time from the extinguished state of the discharge lamp 4 to the arc discharge is as short as possible even over the period, and for that purpose, it is necessary to apply a stable peak voltage of the high-voltage pulse voltage over the entire temperature range.

In the discharge lamp 4, the range of the optimum peak voltage of the high-voltage pulse voltage applied for discharging is determined from the electrical and structural characteristics. If the peak voltage does not reach a certain voltage, the discharge lamp 4 cannot discharge. This value is said to be 13 kV. Further, when the peak voltage exceeds a certain voltage, a voltage exceeding the withstand voltage is applied between the discharge terminals of the discharge lamp 4, which is a problem. This value is 1
It is said to be 8kV.

By the way, the starting circuit 2 at the time of starting lighting
Since the control of the operation stop of 7 is performed by detecting the value of V _DC1 , even if the discharge lamp 4 starts the discharge and the current starts to flow to the secondary side of the high voltage pulse transformer 24, the starting circuit 27 operates immediately. Then, the high voltage pulse transformer 24 is saturated and a large current flows between the drain and the source of the FET 26, causing thermal destruction due to excessive heat. Therefore, the inductor 23 having an air-core structure for suppressing the saturation of the high voltage pulse transformer 24 is required.

FIG. 9 shows the primary side of the high voltage pulse transformer 24, the capacitor 25, the inductor 23, and the capacitor 28.
2 is an equivalent model of the circuit diagram of FIG. The waveform of the high-voltage pulse voltage appears as a resonance waveform of the parallel resonance circuit determined by the high-voltage pulse transformer 24 and the capacitor 25, as described above. However, in reality, distributed capacitance exists between the windings of the inductor of the high-voltage pulse transformer 24, which affects the resonance frequency. The inductance of the primary side of the high voltage pulse transformer 24 is L ₂₄ , the capacity of the capacitor 25 is C ₂₅ ,
The distributed capacitance seen from the primary side of the high voltage pulse transformer 24 is C
_{Let PT be} the inductance of the inductor 23, L ₂₃ , and the capacitance of the capacitor 28 be C ₂₈ . The characteristics of L ₂₃ and L ₂₄ are hardly changed in the temperature range required for the product (-40 ° C to 85 ° C). On the other hand, a capacitor generally has a large characteristic change with temperature. Since the capacitors 25 and 28 are required to have a high capacity, film capacitors are used. Further, the capacitor 28 is a polypropylene capacitor suitable for high-frequency / high-voltage circuits, and the capacitor 25 is a small polyester capacitor due to restrictions on the mounting place of the product. FIG. 10 shows the relationship between the temperature and the capacitance change of the above two types of capacitors with reference to 25 ° C.

Assuming that the impedance of the parallel resonant circuit formed by L ₂₄ · C ₂₅ · C _PT is Z ₁ and the impedance of the series resonant circuit formed by L ₂₃ · C ₂₈ is Z ₂ , the high-voltage pulse transformer 2
The voltage V applied between the four primary windings is

[0017]

[Equation 1]

[0018] Therefore, in order to add more energy to the discharge lamp 4,

[0019]

[Equation 2]

The condition is that In addition, in order to apply the peak voltage of the high-voltage pulse voltage that is safe in the entire temperature range (-40 ° C to 85 ° C),

[0021]

[Equation 3]

The condition is to minimize the change of the value of with temperature. Conventionally, the resonance frequency f ₁ of the parallel resonance circuit determined by the high-voltage pulse transformer 24 and the capacitor 25 is
It was “f ₁ = 500 (kHz)”. At this time, the inductance L _{24 of the} primary side of the high voltage pulse transformer 24, the distributed capacitance C _PT seen from the primary side of the high voltage pulse transformer 24, and the capacitance C ₂₅ of the capacitor ₂₅ are as follows: “L ₂₄ = 4.0 (μH), C
_PT = 7000 (pF), C ₂₅ = 18000 (pF) ". FIG. 12 shows the relationship between the frequency and the impedance of the LC parallel resonance circuit. f ₁ is room temperature (25
The resonance frequency at ° C.), f _1-is a resonance frequency at a low temperature (-40 ℃), f ₁₊ represents respectively the resonance frequency at a high temperature (85 ° C.). Z ₁₋ , Z ₁ and Z ₁₊ represent the impedance of the LC parallel resonance circuit at −40 ° C., 25 ° C. and 85 ° C., respectively. From this figure, "f _1- > f ₁ > f
_It can be seen that it is " ₁₊ ", but it can be said that this is due to the influence of the temperature characteristics of the capacitor shown in FIG.

On the other hand, the resonance frequency f ₂ of the series resonance circuit determined by the inductor 23 and the capacitor 28 is "f ₂ =
It was used at "540 (kHz)". At this time, the inductance L ₂₃ of the inductor 23 and the capacitance C ₂₈ of the capacitor ₂₈
Means “L ₂₃ = 4.0 (μH), C ₂₃ = 22000 (p
F) ". FIG. 13 shows the relationship between the frequency and the impedance of the LC series resonance circuit. f ₂ is the resonance frequency at room temperature (25 ° C.) and f _{2 −} is the low temperature (−40
C), and f ₂₊ represents the resonance frequency at high temperature (85 ° C). In addition, Z _2- , Z ₂ , Z ₂₊
Represents the impedance of the LC series resonance circuit at −40 ° C., 25 ° C., and 85 ° C., respectively. From this figure, "f _2-
<F ₂ <f ₂₊ ”, which can be said to be due to the influence of the temperature characteristics of the capacitor shown in FIG.

With this constant, the temperature characteristic of the peak voltage V _p of the high voltage pulse voltage varies as shown in FIG.

[0025]

[Equation 4]

It has become.

[0027]

According to the conventional configuration,
Since this lighting circuit device is placed in a place where the ambient temperature changes significantly, the change in the characteristics of parts due to the temperature change has a great effect on the product characteristics, and the change in the peak voltage of the high-voltage pulse voltage is as large as 3.3 kV over the entire temperature range. , The voltage range to be applied between the discharge terminals of the discharge lamp 4 (13 kVP-P to 18
1k, which is a range that can be sufficiently guaranteed for kVP-P)
It had a problem of exceeding the change within V.

The present invention solves the above-mentioned problems of the prior art by providing more energy between the discharge terminals of the discharge lamp 4 and in the entire temperature range (-40 ° C to 85 ° C).
(EN) A lighting circuit device capable of applying a stable peak voltage of a high-voltage pulse voltage over (C).

[0029]

In order to solve this problem, a high-intensity discharge lamp lighting circuit device for an automobile of the present invention comprises:
A power supply circuit having a power supply terminal for boosting a voltage input from a DC power supply to obtain a boosted voltage and a power supply terminal for supplying power to a discharge lamp, a primary winding and a secondary winding, and one end of the primary winding Is connected to the power supply terminal of the power supply circuit and the other end is connected to one end of an inductor having an air-core structure, and both ends are connected to a capacitor, a switching element and a capacitor connected to the other end of the inductor, A resonance circuit having a starting circuit for starting the discharge lamp and a control circuit for controlling the electric power of the discharge lamp, wherein the peak voltage of the high-voltage pulse voltage necessary for starting the lighting of the discharge lamp is affected by the temperature. It was suppressed by using.

[0030]

[Function] With this configuration, the impedance of the parallel resonance circuit determined by the high-voltage pulse transformer and the capacitor is maximized,
Also, the impedance of the series resonant circuit determined by the inductor and the capacitor can be minimized, and maximum energy can be efficiently given to the high voltage pulse transformer,
It is possible to minimize the influence of the temperature on the peak voltage of the high-voltage pulse voltage required for starting the lighting of the discharge lamp.

[0031]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a circuit around a discharge lamp 4 of a high-intensity discharge lamp lighting circuit device for an automobile of the present invention. Since the circuit configuration is the same as that of the conventional example shown in FIG. 6, the same reference numerals are given and the description thereof is omitted.

In FIG. 1, the flyback transformer 21
Energy is transferred to the discharge lamp 4 through the high voltage pulse transformer 24 by the DC voltage V _DC1 obtained by being boosted by 1 and rectified by the diode 212 and the capacitor 213 and the switching operation of the FET 26, and output as a high voltage pulse voltage. FIG. 3 shows an LC according to an embodiment of the present invention.
FIG. 4 is a relationship diagram of frequency and impedance of the parallel resonant circuit, and FIG. 4 is a relationship diagram of frequency and impedance of the LC series resonant circuit according to the embodiment of the present invention.

As described with reference to FIG. 9 of the conventional example,
40 ° C., 25 ° C., the voltage V _-40 applied between the primary winding of the high-voltage pulse transformer 24 immediately after FET26 is turned OFF at ₈₅ ℃, V _25, V 85, respectively,

[0034]

[Equation 5]

[0035] Where the impedance subscript is
− Indicates impedance at −40 ° C., + indicates impedance at 85 ° C., and no suffix indicates impedance at 25 ° C.

It is generally known that in an LC resonance circuit, the impedance at the resonance frequency is maximum in the parallel resonance circuit and minimum in the series resonance circuit.
Therefore, the conditions for applying more energy to the discharge lamp 4.

[0037]

[Equation 6]

In order to sufficiently apply the above, it is understood that it is sufficient if the resonance frequency of the parallel resonance circuit and the resonance frequency of the series resonance circuit can be matched.

Further, the impedance of the series resonance circuit

[0040]

[Equation 7]

When the loss resistance component of the inductor 23 is r,

[0042]

[Equation 8]

It becomes Where r · L ₂₃ is constant, and
C _{28 is} also constant at the used frequency. From this,
It can be seen that

From the above, the conditions for applying the stable peak voltage of the high-voltage pulse voltage over the entire temperature range.

[0045]

[Equation 9]

It is understood that "f ₁ = f ₂ " can be set in order to minimize the change in the value of due to temperature.

Actually, as a circuit constant, "L ₂₄ = 4.0 (μ
H), C ₂₅ = 10,000 (pF), L ₂₃ = 4.5 (μ
H), C ₂₈ = 15000 (pF) "," f ₁
= F ₂ = 610 (kHz) ”, and the temperature characteristic of V _p at this time is“ ΔV _p = 0.6 (kV) ”as shown in FIG. 2, which is within the guaranteed range of 1 kV. There is.

[0048]

As described above, the lighting circuit device for a high-intensity discharge lamp for an automobile according to the present invention has a resonance frequency f ₁ of a parallel resonance circuit determined by a high-voltage pulse transformer and a capacitor,
At the resonance frequency f ₂ of the series resonance circuit determined by the inductor and the capacitor,

[0049]

[Equation 10]

By so doing, the impedance of the parallel resonant circuit determined by the high voltage pulse transformer and the capacitor can be maximized, and the impedance of the series resonant circuit determined by the inductor and the capacitor can be minimized. Can be efficiently provided, and the influence of the temperature on the peak voltage of the high-voltage pulse voltage required at the start of lighting of the discharge lamp can be minimized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a lighting circuit device for an automobile high-intensity discharge lamp according to an embodiment of the present invention.

FIG. 2 is a temperature characteristic diagram of a peak voltage V _p of a high voltage pulse voltage according to an embodiment of the present invention.

FIG. 3 is a relationship diagram of frequency and impedance of an LC parallel resonance circuit according to an embodiment of the present invention.

FIG. 4 is a relationship diagram of frequency and impedance of an LC series resonance circuit according to an embodiment of the present invention.

FIG. 5 is a block diagram of a conventional lighting circuit device for an automobile high-intensity discharge lamp.

FIG. 6 is a specific circuit diagram of a conventional lighting circuit device for an automobile high-intensity discharge lamp.

FIG. 7 is a gate signal waveform diagram of the FET in FIG.

FIG. 8 is a waveform diagram of the voltage applied to the gate of the FET 26 and the high-voltage pulse voltage applied between the discharge terminals of the discharge lamp 4 at the time of starting lighting.

FIG. 9 is an equivalent model diagram of an LC parallel resonance circuit and an LC series resonance circuit.

FIG. 10 is a relationship diagram of a capacitance value change with temperature of a capacitor.

FIG. 11 is a temperature characteristic diagram of a peak voltage V _p of a conventional high voltage pulse voltage.

FIG. 12 is a diagram showing the relationship between frequency and impedance of a conventional LC parallel resonant circuit.

FIG. 13 is a relationship diagram of frequency and impedance of a conventional LC series resonance circuit.

[Explanation of symbols]

 1 DC power supply 2 Lighting circuit device 3 Lighting switch 4 Discharge lamp 21 DC / DC converter 22 Polarity changeover switch circuit 23 Inductor 24 High voltage pulse transformer 25 Capacitor 26 FET 27 Start circuit 28 Capacitor 29 Control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Makoto Inoue 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masanori Hatanaka 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Junichi Yukawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A power supply circuit having a power supply terminal for boosting a voltage input from a DC power supply to obtain a boosted voltage and a power terminal for supplying power to a discharge lamp, and a primary winding and a secondary winding. A high-voltage pulse transformer having one end of the primary winding connected to the power supply terminal of the power supply circuit, the other end connected to one end of an inductor having an air-core structure, and both ends connected to a capacitor; a switching element connected to the other end of the inductor; It has a capacitor, a starting circuit for starting the discharge lamp, and a control circuit for controlling the electric power of the discharge lamp, and the peak voltage of the high-voltage pulse voltage required at the time of starting the lighting of the discharge lamp is affected by the temperature. High-intensity discharge lamp lighting circuit device for automobiles, whose effects are suppressed by using a resonance circuit.