JPH08203687A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE: To quickly start up the luminous flux at starting, and suppress the secondary current at earthing to enhance the safety. CONSTITUTION: A DC power source V1 , the primary winding N1 of a transformer T, and a switching element Q1 are connected in series, a diode D1 and a capacitor C1 are connected in series to the secondary winding N2 of the transformer T, and a load circuit having a discharge lamp 1 as the final load is connected in parallel to the capacitor C1 . This device has a control means for stopping the operation of the switching element Q1 when the detected value of the primary current of the transformer T reaches a prescribed value, the prescribed value is formed of a first prescribed value E1 selected in a starting period until the discharge lamp 1 reaches a substantially stable lighting state from the starting, and a second prescribed value E2 selected when the discharge lamp 1 is substantially stably lighted, and the first prescribed value E1 is set larger than the second prescribed value E2 .

Description

Detailed Description of the Invention

[0001]

The present invention relates to a high intensity discharge lamp (HID
The present invention relates to a lighting device for a lamp, and particularly to a discharge lamp lighting device used for a vehicle headlamp.

[0002]

22 is a circuit diagram of a conventional example. The switching element Q ₁ connected to the primary side of the transformer T turns ON / OFF at a high speed. Switching element Q ₁ is ON
Then, since a current flows from the DC power supply V ₁ to the primary winding N ₁ of the transformer T, energy is accumulated in the transformer T. When the switching element Q ₁ is turned off, the transformer T
Has the polarity shown in the figure, the energy stored in the transformer T is discharged from the secondary winding N ₂ to the capacitor C ₁ via the diode D ₁ . In this way,
Energy can be transferred from the DC power supply V ₁ to the capacitor C ₁ by turning ON / OFF the switching element Q ₁ .

An inverter circuit 21 having a full bridge structure of switching elements Q ₂ , Q ₃ , Q ₄ and Q ₅ is connected to both ends of the capacitor C ₁ . The inverter circuit 21 includes a switching element Q _2, Q ₅ is ON, and the switching element Q _3, period Q ₄ is OFF, the switching element Q _2, Q ₅ is OFF, the switching element Q _3, Q
There is a period in which ₄ is ON, and the drive circuit 22 composed of a low frequency oscillator and a frequency dividing circuit alternately switches both periods at a low frequency. The starting means 23 is an igniter circuit for starting the discharge lamp 1 which is the final load. When the discharge lamp 1 is a high pressure discharge lamp such as a metal halide lamp, the starting means 23 applies a high voltage (for example, a pulse voltage of 10 to 30 kV) for starting the discharge from the extinguished state of the discharge lamp 1. is there.

The inverter circuit 21 outputs the DC output of the capacitor C ₁ to several tens to prevent catalysis when a DC voltage is applied to the discharge lamp 1 and acoustic resonance when a high frequency is applied.
Convert to low frequency AC of several hundred Hz. Switching element Q
Discharge lamp 1 by switching _{2 to} Q ₅ at low frequency
Is to start discharging by the pulse voltage of the starting means 23, and then convert the voltage across the capacitor C ₁ into a low-frequency rectangular wave voltage to give energy to the discharge lamp 1 to light it. Load current is detected by the resistor R _1, resistor R
_The load voltage is detected by ₂ and R ₃ . These detected values are sent to the control unit 3 and used to light the discharge lamp 1 with desired characteristics.

The control unit 3 will be briefly described below.
The detected load voltage V and load current I are sent to the detection means 31 and 32 having a filter and an amplification function in the control unit 3, respectively, and the outputs of the detection means 31 and 32 are input to the multiplier 34 to turn on the light. The electric power W of the inside discharge lamp 1 is calculated. on the other hand,
The detected value Vd of the detecting means 31 is sent to the electric power target value setting means 33, and the required electric power value Vm required according to the current voltage V of the discharge lamp 1 is output. FIG. 23 shows the detection value V of the detection means 31.
The relationship between d and the target power value Vm is shown. This target power value Vm and the calculated power value are sent to the calculation means 35, and the error signal thereof causes the pulse width modulator 36 to switch the switching element Q.
Determine the ON / OFF duty required for ₁ . This controls the electric power of the discharge lamp 1 to have desired characteristics.

By the way, when an accident occurs such that one end of the discharge lamp 1 is connected to one end of the DC power supply V ₁ (ground fault) for some reason, the secondary current of the transformer T becomes larger than a desired value. . As shown in FIG. 24, the lamp current I is large in the starting process, but in the case of a ground fault, the lamp current I is large even during stable lighting. This is unsafe.

FIG. 25 is a circuit diagram of another conventional example. In this conventional example, the primary side current flowing through the switching element Q ₁ is detected by the resistor R ₄ , and the detected value is detected by the comparator C
By comparing P ₂ with a predetermined value E, the electric power supplied from the primary side to the secondary side is regulated to limit the lamp current. Also in this conventional example, in order to reduce the lamp current I ₂ at the time of stable lighting in the case of a ground fault, the predetermined value E is originally set to a small value. Then, there is a problem that electric power for raising the luminous flux at the time of starting the discharge lamp 1 cannot be obtained. In particular, when it is used in a vehicle, it is desirable to keep the light on as much as possible for safe driving. Therefore, it is desirable that the device is not turned off even if a problem occurs and the device is not destroyed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to make it possible to quickly start up a luminous flux at the time of starting, and Another object of the present invention is to provide a discharge lamp lighting device capable of suppressing the secondary current at the time of a short circuit and improving safety.

[0009]

According to the discharge lamp lighting device of the present invention, in order to solve the above problems, as shown in FIG. 1, a DC power source V ₁ and a primary winding N _{1 of a} transformer T are provided. And a switching element Q ₁ connected in series, and a diode D _{1 on the} secondary winding N ₂ of the transformer T.
And a capacitor C ₁ connected in series to form a second series closed circuit, and a load circuit connected in parallel with the capacitor C ₁ and having a final load of the discharge lamp 1. Insert the current detection means in the series closed circuit of 1,
When the detection value of the current detection means reaches a predetermined value, the control means for stopping the operation of the switching element Q ₁ is provided, and the predetermined value reaches a substantially stable lighting state when the discharge lamp 1 is activated. Of the first predetermined value E ₁ selected during the starting period up to and a second predetermined value E ₂ selected when the discharge lamp 1 is substantially stably lit.
₁ is larger than the second predetermined value E ₂ . Here, the first predetermined value E ₁ and the second predetermined value E ₂
May be selected according to the detected value of the lamp voltage, may be selected according to the time after the discharge lamp 1 is started, or may be selected according to the detected value of the light detection means provided in the vicinity of the discharge lamp 1. May be.

[0010]

According to the present invention, the peak value of the current flowing through the primary side of the transformer T is increased during the starting period until the discharge lamp 1 is started and reaches a substantially stable lighting state.
It is possible to quickly start up the luminous flux at the time of starting, and since the peak value of the current flowing through the primary side of the transformer T is made small when the discharge lamp 1 is in a substantially stable lighting state, In the event of a short circuit, the secondary current can be suppressed and safety can be improved.

[0011]

1 is a circuit diagram of a first embodiment of the present invention.
The circuit configuration will be described below. The positive electrode of the DC power supply V ₁ is connected to one end of the primary winding N ₁ of the transformer T. The other end of the primary winding N ₁ of the transformer T is a MOSFET
Connected to the drain of the switching element Q ₁ . The source of the switching element Q ₁ is connected to the negative electrode of the DC power supply V ₁ via the resistor R ₄ . DC power supply V ₁
Is, for example, a vehicle battery, and in the embodiment, the negative electrode side is grounded to the vehicle body. Secondary winding N of transformer T
One end of ₂ is connected to one end of the capacitor C ₁ via the anode and cathode of the diode D ₁ . The other end of the secondary winding N ₂ of the transformer T is connected to the other end of the capacitor C ₁ and also connected to the negative electrode of the DC power supply V ₁ and grounded. Both ends of the capacitor C ₁ are connected to the inputs of the balancer 2. The discharge lamp 1 is connected to the output of the balancer 2 as a load. The balancer 2 is composed of an electronic lighting circuit composed of the above-mentioned inverter circuit having a full bridge structure and an igniter circuit. The switching elements Q _{2 to} Q ₅ of the inverter circuit are controlled by the control unit 3. The drive signal of the switching element Q ₁ for DC-DC conversion is supplied from the control unit 3 via the gate G1. The comparator C is connected to one input of the gate G _1.
The output of P ₂ is connected. The reference voltage E ₁ or E ₂ is applied to the switching means S at the negative input terminal of the comparator CP _2.
Selected by W and input. Comparator CP
_The voltage across the resistor R ₄ is input to the positive input terminal of ₂ .

FIG. 2 is a diagram for explaining the operation of this embodiment. In the figure, V is the lamp voltage, I is the lamp current, and W is the lamp power. In the starting region, the lamp voltage V is low and a large amount of the lamp current I flows, but in the stable lighting region, the lamp voltage V is low.
Rises and the lamp current I decreases. Therefore, in this embodiment, as the reference voltage E which determines the peak value of the primary current flowing through the switching element Q _1, a reference voltage E ₁ of the starting process and have set the reference voltage E ₂ of the stable lighting region,
E ₁ > E ₂ . In the starting process of the discharge lamp 1, the reference voltage E ₁ in the starting process is set to a value that does not hinder the supply of electric power for quickly raising the luminous flux. Further, the reference voltage E ₂ in the stable lighting region is set to a value that cannot normally occur during steady lighting of the discharge lamp 1.
The control unit 3 selects the first reference voltage E ₁ during the starting process and selects the second reference voltage E ₂ when shifting to the steady lighting state. As a result, it is possible to quickly start up the light flux at the time of starting, and it is possible to suppress the secondary current at the time of a ground fault and improve safety.

FIG. 3 is a circuit diagram of the second embodiment of the present invention, and FIG. 4 is an operation explanatory diagram of the present embodiment. In the present embodiment, the voltage across the smoothing capacitor C ₁ on the secondary side is divided by the resistors R ₂ and R ₃ , the lamp voltage is detected instead, and the detected value is set to V ₃ . The comparator CP ₃ compares the detected value V ₃ with the reference value E ₃ , and when V ₃ > E _3, it becomes 1
The peak determination value of the next current is switched from the reference voltage E ₁ during the starting process to the reference voltage E ₂ during stable lighting.

FIG. 5 is a circuit diagram of a third embodiment of the present invention.
6 is an operation explanatory diagram of this embodiment. In this example
Is the battery V₂And switch SS is ON / O when the user lights up
It is a means for determining the FF. Switch SS is ON
Then, the control unit 3 operates the main circuit to turn on the discharge lamp 1.
When the switch SS is turned off, the discharge lamp 1 is turned off.
Work to get them to work. In the timer means 5, the switch SS is O
N, the predetermined timer time T₁Output until
Low level and predetermined timer time T₁To become and,
After that, the output is set to the high level. Timer means
When the output of 5 is low level, switching element Q₆
Is turned off, and the reference voltage E is the resistance R_Five, R ₆And Vs
Reference voltage E in the starting process₁And Timer means
When the output of 5 is high level, the transistor Q₆But
When turned on, the reference voltage E is the resistance R_Five, R₆, R₇Constant at
The voltage Ve is divided and the reference voltage E during stable lighting₂Becomes
Resistance R _Five, R₆, R₇The same as the first embodiment described above.
Reference voltage E₁, E₂To be configured. Also,
Timer time T₁From the cold start of discharge lamp 1
Set a sufficient time before switching to constant lighting. Since
Due to the above, when the discharge lamp 1 is started, E = E₁And then enough
Power can be supplied and E = E when stable lighting₂When
Therefore, an excessive current can be suppressed. This solves the problem
Will be decided. The battery V₂And SS are essential
Instead of transmitting ON / OFF to the timer means 5,
The means of is also good.

FIG. 7 is a circuit diagram of the fourth embodiment of the present invention.
8 and 9 are explanatory diagrams of the operation. In this example
Is the timer means 5 of the third embodiment, as shown in the figure.
And the comparator CP_FourAnd reference voltage Vt, resistance R₈, R
₉And capacitor C₂Consisting of a charge / discharge circuit consisting of
Is. Switch SS is turned on and capacitor C₂of
Voltage V₉Gradually rises to V₉When> Vt is reached, Thailand
Since the output of the marker means 5 becomes High level, E = E
₁From the state of E = E₂To the state of
The same effect as the embodiment can be obtained. Here, switch SS
When turned off, capacitor C₂Is resistance R₉Discharge by
V will be done₉Gradually descends. Capacitor C
₂Switch on again before is fully discharged
Then, the capacitor C₂Voltage V₉Is from the initial value (> 0)
Since it is charged, it is usually V₉When it is charged from = 0
Rimo timer time T₁Becomes shorter. Ie timer
Time T ₁Is determined by the OFF period of the switch SS
It If the OFF period of the switch SS is short, the timer time
T₁Becomes shorter. Moreover, the OFF period of the switch SS is long.
Cousin, timer time T₁Becomes longer. Discharge lamp 1 of the present invention
Is sometimes used for vehicle headlights, and
Need to be made. In that case, switch SS is OFF,
That is, if the lamp is restarted after being turned off for a short time, it will be discharged.
Since the lamp 1 is lit from a substantially stable state,
Because it is less necessary to give excessive power for
E = E₁The period will be short and good. Therefore,
It is safer and is the preferred embodiment.

FIG. 10 is a circuit diagram of the fifth embodiment of the present invention. In this embodiment, the light emission amount of the discharge lamp 1 is detected by using a photodetector such as a photodiode PD, and if it is equal to or more than a predetermined light amount, it is regarded as a stable lighting state, and the reference voltage E is set to the reference voltage in the starting process. The E ₁ is switched to the reference voltage E ₂ for stable lighting.

As described above, the peak value of the primary side current of the transformer T can be limited by directly or indirectly detecting the stable lighting state of the discharge lamp 1. As the reference voltage E, the first reference voltage E ₁ and the second reference voltage E ₂
However, the number of steps may be three or more. further,
It may be changed linearly depending on the lighting state.

FIG. 11 is a circuit diagram of a sixth embodiment of the present invention. In the present embodiment, the safety is further improved by using direct current lighting using only the non-ground fault side polarity of the rectangular wave inverter circuit unit in the case of the ground fault in each of the previous embodiments. That is, when the output line to the discharge lamp 1 is grounded due to an accident or the like, depending on the output polarity, the state is equivalent to a load short circuit and the voltage is not normally applied. Therefore, the discharge lamp 1
The ground fault detecting means 24 detects the ground fault at either one end a or b, and changes the operation of the bridge type inverter circuit. When the terminal a side is grounded, the switching elements Q ₃ and Q ₄ are always turned on and the switching elements Q ₂ and Q ₅ are always turned off. Also, when the terminal b side is grounded, the switching elements Q ₂ and Q ₅ are always turned on.
The switching elements Q ₃ and Q ₄ are always turned off. When neither of the terminals a and b has a ground fault, the switching elements Q ₂ and Q ₅ and Q ₃ and Q ₄ are alternately turned on / off at a low frequency.

FIG. 12 shows a seventh embodiment of the present invention. This embodiment is a type in which the body of the vehicle is connected to the positive potential of the battery (DC power supply V ₁ ) in the above circuit, and the point A (or point B) contacts the body during the installation work (load). Is shorted to the positive side of the power supply). Assuming that the point A contacts the body of the vehicle at that time, the path through which the current flows assumes the positive end of the DC power source V ₁ , the point Y, the body of the vehicle, the point A, the switching element Q ₄ , the resistor R ₁ , and the point. X, a current flows through the path of the negative end of the DC power supply V ₁ . At this time, the current flowing through the resistor R ₁ is usually higher than that during stable lighting of the discharge lamp 1. Further, the value of the current flowing through the resistor R ₁ is constantly monitored for lamp power control. Therefore, when the current value is set to a predetermined value or more (that is, one end of the load is a positive voltage of the power supply). (If short-circuited to the side), stop the circuit. When the circuit is stopped, the predetermined value of the current flowing through the resistor R ₁ is preferably changed according to the state of the discharge lamp 1 as in the above-described first to sixth embodiments.

FIG. 13 shows an eighth embodiment of the present invention. In this embodiment, in the DC-DC conversion circuit 6, the transformer T
Instead of connecting one end of the secondary side of the above to the ground line, it is connected between the switching element Q ₁ and the resistor R ₄ for detecting the primary current of the transformer T. In the normal operation, the current detection output as shown in FIG. 14A is obtained. For example, at the moment when the ground fault occurs at the point a (or when the switching element Q ₁ is _first turned on after the ground fault), The detection output swings to the negative side like Tc in (b). By detecting this negative voltage by the comparator CP ₄ and holding the output of the comparator CP _{4 in} the flip-flop FF, the stop signal Sx of the switching element Q ₁ can be obtained. This promptly detects the ground fault and stops the discharge lamp lighting device. The resistance value of the current detecting resistor R ₄ is set to be small, and the detected value is also small, so that it has almost no influence on the detection of the lamp voltage and the like. Also, to detect the ground fault current,
It is not necessary to separately provide a resistance for detecting a large amount of current, which is advantageous in terms of cost and downsizing.

FIG. 15 shows a ninth embodiment of the present invention. This lighting device is supposed to be used for a vehicle headlight. At this time, the crossover between the starting means and the discharge lamp 1 may be short-circuited with the vehicle body for some reason. Normally, the vehicle body is connected to one end of the DC power supply V ₁ ,
The energy stored in the capacitor C ₁ causes a current to flow through the vehicle body, not through the discharge lamp 1. Such a state is called a ground fault, and the ground fault current is called a ground fault current. When this ground fault occurs, there is a possibility that an excessive ground fault current may destroy the element or cause a serious accident such as heat generation at the ground fault point. Therefore, in the present embodiment, when a ground fault occurs, the impedance element (Z ₁ , Z ₂ , Z ₃ ) is inserted at least at one place in the path through which the ground fault current flows, which is substantially the same. The ground fault current is reduced. The impedance element may be a resistor R, a capacitor, an inductor, or the like. Optimum point is impedance Z
_The resistor R is used as ₁ , and the value of the resistor R may be any value that can be reduced to a level at which the ground fault current does not destroy the element. By doing this, the switching element does not generate heat or is damaged even if there is a ground fault, and while preventing problems such as heat generation at the ground fault point, it keeps lighting and contributes to vehicle safety. It becomes possible.

FIG. 16 shows a tenth embodiment of the present invention. This embodiment is a specific circuit example of the ninth embodiment. The lamp voltage, which is the state of the discharge lamp 1, is simulated by a capacitor C ₁
Of the lamp current detected by the resistors R ₂ and R ₃ from both ends of the lamp, and the result of the lamp current detected by the resistor R ₁ is processed by the controller 3a, and the potential level is converted and transmitted to the level converter 3b and the controller 3c for switching. Control element Q ₁ . That is, since the resistor R ₄ is inserted, a potential difference is generated between the points Ga and Gb due to the current flowing through the resistor R ₄ , and the control unit 3
Since the reference potentials of a and 3c are different, the level converter 3b that eliminates the potential difference between the points Ga and Gb is inserted in order to perform accurate control. The control units 3a and 3c may cut off any part of the signal flow of the control unit 3 in FIG.

In the example of FIG. 17, the control unit 3c has only the pulse width modulator 36, and the control unit 3a has the detection unit 31 to the error amplifier 35. Since the output of the error amplifier 35 is an analog voltage value, the level converter 3b uses the photocoupler PC to convert the voltage into light, light, and voltage to convert the potential. In the example of FIG.
The current mirror circuit is used for the level converter 3b by dividing the same at the same position. In the example of FIG. 19, the control unit 3
a is the entire control unit 3 in FIG. 22, and the pulse width modulator 36
Level of the output of the pulse transformer PT,
It drives the switching element Q ₁ . In this way, the control unit 3 may be divided anywhere to be the control units 3a and 3c, and the level converter 3b may be anything according to the control units 3a and 3c.

FIG. 20 shows an eleventh embodiment of the present invention. The voltage divided by the resistors R ₂ and R ₃ and the voltage divided by the resistors R ₅ and R ₆ are differentially amplified by the differential amplifier A ₁ to serve as voltage detecting means. Further, the voltage divided by the resistors R ₇ and R ₈ and the voltage divided by the resistors R ₅ and R ₆ are differentially amplified by the differential amplifier A ₂ to serve as a current detecting means. Normally, resistors R ₃ and R
The values of ₆ , R ₅ , R ₇ , and R ₈ are several K to several 100 KΩ and are large enough to reduce the ground fault current, so the ground fault current becomes small. As a result, it functions substantially the same as the ninth embodiment.

FIG. 21 shows a twelfth embodiment of the present invention. In this embodiment, the capacitor Cx is used as the current limiting impedance, and since the ground fault current flowing from the capacitor C ₁ is direct current, the route of the ground fault current can be stopped by the capacitor Cx. Thereby, the ground fault current can be reduced. However, since it is necessary to detect the secondary side voltage of the transformer T for control, the transformer T has a secondary winding N ₂
A winding N ₃ for outputting a voltage proportional to is provided as the detected value of the lamp voltage. On the other hand, the detection of the lamp current can be approximately known from the detected value of the lamp voltage by calculating the electric power fed into the primary side. Since the capacitor Cx connects between the primary and secondary in terms of high frequency, stable operation can be realized.

[0026]

According to the invention of claim 1, a first series closed circuit formed by connecting a DC power supply, a primary winding of a transformer and a switching element in series, and a diode in the secondary winding of the transformer. And a capacitor connected in series to form a second series closed circuit, and a load circuit connected in parallel with the capacitor and having a final load as a discharge lamp. The current detection means is inserted into, and when the detection value of the current detection means reaches a predetermined value, it has a control means for stopping the operation of the switching element, the predetermined value, the discharge lamp is started, A first predetermined value selected during a starting period until reaching a stable lighting state and a second predetermined value selected when the discharge lamp is substantially stable lighting, and the first predetermined value is a first predetermined value. Is set larger than the predetermined value of 2 So rapidly can be performed the launch of the light beam at the time of startup, and the ground fault suppresses the secondary current, thereby preventing the breakdown of the device can be as much as possible to maintain the lighting, increase safety.

According to the invention of claim 2, the lamp voltage is detected, and when the lamp voltage is low, the operation in the starting period is selected, and when the lamp voltage is high, the operation in the substantially stable lighting state is performed. Since the selection is made, the operation can be appropriately selected according to the state of the discharge lamp. According to the third aspect of the present invention, the lamp voltage is alternatively detected by the voltage across the capacitor, so that the lamp voltage can be detected with a simple configuration. According to the invention of claim 4, the first predetermined value is selected until a predetermined time after the discharge lamp is activated, and the second predetermined value is selected after the predetermined time is exceeded. The operation can be selected according to the state of the discharge lamp. According to the invention of claim 5, when the extinguishing time from the last extinguishing of the discharge lamp to the restart is short, the starting period is shortened, and when the extinguishing time is long, the starting period is extended. Therefore, when the extinguishing time is short, it is possible to prevent excessive energy from being injected into the discharge lamp. According to the invention of claim 6, the light detecting means is provided in the vicinity of the discharge lamp, the first predetermined value is selected when the detected value is lower than the predetermined light detected value, and the second predetermined value is selected when the detected value is higher. Since the predetermined value is selected, the operation according to the state of the discharge lamp can be selected with a simple configuration.

According to the invention of claims 7 and 8, when the load circuit is a full-bridge type inverter circuit,
When a ground fault is detected, the circuit can be protected by enabling lighting only with the non-ground fault side polarity. Further, according to the invention of claim 9, when one end of the load is short-circuited to one end of the power supply, the current flowing through the second series closed circuit is detected, and if the current is equal to or more than a predetermined value, the circuit operation is performed. It protects the circuit by eliminating the risk of electric shock because it stops the electric shock.
According to the invention of claim 10, depending on the lighting state,
By changing the predetermined value for stopping the circuit, the circuit can be surely protected in the stable lighting state.

According to the invention of claim 11, the transformer 1
By combining the current detection resistor for detecting the current flowing to the secondary side with the ground fault detection resistor, it is possible to detect the ground fault without increasing the ground current detection resistor that withstands a large amount of current, which simplifies the circuit configuration. And cost reduction. According to the twelfth aspect of the present invention, since the impedance element is inserted in the path through which the ground fault current flows, even if a ground fault occurs, an excessively large ground fault current does not flow, resulting in problems such as device breakdown and heat generation. It is possible to maintain the same lighting as during normal lighting without causing the occurrence, and it is possible to enhance the safety when used as a vehicle headlight. According to the inventions of claims 13 to 16, even when the impedance element is inserted in the path through which the ground fault current flows, the load voltage and the like can be appropriately detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

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

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of the third embodiment of the present invention.

FIG. 7 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 8 is a first operation explanatory diagram of the fourth embodiment of the present invention.

FIG. 9 is a second operation explanatory diagram of the fourth embodiment of the present invention.

FIG. 10 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 11 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 12 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 13 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 14 is an operation waveform diagram of the eighth embodiment of the present invention.

FIG. 15 is a circuit diagram of a ninth embodiment of the present invention.

FIG. 16 is a circuit diagram of a tenth embodiment of the present invention.

FIG. 17 is a circuit diagram showing an example of a level conversion unit according to a tenth embodiment of the present invention.

FIG. 18 is a circuit diagram showing another example of the level conversion unit according to the tenth embodiment of the present invention.

FIG. 19 is a circuit diagram showing still another example of the level conversion unit according to the tenth embodiment of the present invention.

FIG. 20 is a circuit diagram of an eleventh embodiment of the present invention.

FIG. 21 is a circuit diagram of a twelfth embodiment of the present invention.

FIG. 22 is a circuit diagram of a first conventional example.

FIG. 23 is a first explanatory diagram showing the control characteristics of the first conventional example.

FIG. 24 is a second explanatory diagram showing the control characteristics of the first conventional example.

FIG. 25 is a circuit diagram of a second conventional example.

FIG. 26 is an operation explanatory diagram of the second conventional example.

[Explanation of symbols]

 1 discharge lamp 2 lighting circuit 3 control unit 4 control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihisa Hirata, 1048 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Hideki Hamada, 1048, Kadoma, Kadoma City, Osaka, Matsushita Electric Works, Ltd. (72) Inventor Takashi Kambara 1048, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (16)

[Claims] 1. A first series closed circuit formed by connecting a direct current power source, a primary winding of a transformer and a switching element in series, and a second closed winding formed by connecting a diode and a capacitor in series to a secondary winding of the transformer. In a discharge lamp lighting device comprising a series closed circuit of 2 and a load circuit whose final load is a discharge lamp, which is connected in parallel with the capacitor, current detection means is inserted in the first series closed circuit. When the detection value of the current detection means reaches a predetermined value, it has a control means for stopping the operation of the switching element, and the predetermined value is a starting period until the discharge lamp is started and a substantially stable lighting state is reached. And a second predetermined value selected when the discharge lamp is lit in a substantially stable manner.
The discharge lamp lighting device is characterized in that the predetermined value is larger than the second predetermined value. 2. A lamp voltage detecting means is provided, and when the detected value is lower than a predetermined lamp voltage detected value, the first
2. The discharge lamp lighting device according to claim 1, wherein the predetermined value is selected, and when it is higher, the second predetermined value is selected. 3. The discharge lamp lighting device according to claim 2, wherein the lamp voltage is alternatively detected by the voltage across the capacitor. 4. The discharge lamp according to claim 1, wherein the first predetermined value is selected until a predetermined time after the discharge lamp is activated, and the second predetermined value is selected after the predetermined time is exceeded. Lighting device. 5. The predetermined time is shortened when the extinguishing time from the last extinguishing of the discharge lamp to the restart thereof is short, and the predetermined time is lengthened when the extinguishing time is long. The discharge lamp lighting device according to claim 4. 6. A light detection means is provided in the vicinity of the discharge lamp, and when the detection value is lower than a predetermined light detection value, the first predetermined value is selected, and when it is higher, the second predetermined value is selected. The discharge lamp lighting device according to claim 1, which is selected. 7. The load circuit includes at least a full-bridge type inverter circuit composed of four switching elements, and a discharge lamp starting means connected between the output of the inverter circuit and the discharge lamp. Claim 1
The discharge lamp lighting device described. 8. A means for detecting that one end of the load has a ground fault, and a means for lighting the full-bridge type inverter circuit only with a non-ground fault side polarity when detecting that one end of the load has a ground fault. The discharge lamp lighting device according to claim 7, wherein: 9. A means for detecting a current flowing through the second series closed circuit when one end of the load is short-circuited to one end of the power supply and stopping the circuit operation when the current is equal to or more than a predetermined value. The discharge lamp lighting device according to claim 7, further comprising: 10. The discharge lamp lighting device according to claim 9, further comprising means for changing the predetermined value between when the discharge lamp is started and when the discharge lamp is stably lit. 11. A first series closed circuit formed by connecting a DC power supply, a primary winding of a transformer and a switching element in series, and a second closed winding formed by connecting a diode and a capacitor in series to a secondary winding of the transformer. In a discharge lamp lighting device comprising a series closed circuit of 2 and a load circuit whose final load is a discharge lamp, which is connected in parallel with the capacitor,
A means for detecting a current flowing to the next side is provided, one end of the resistance is grounded, a non-ground side terminal is connected to one end of the capacitor, and means for detecting a ground fault current by the resistance is provided. Characteristic discharge lamp lighting device. 12. A first series closed circuit formed by connecting a direct current power supply, a primary winding of a transformer and a switching element in series, and a second closed winding formed by connecting a diode and a capacitor in series. In a discharge lamp lighting device configured by two series closed circuits and a load circuit in which the final load is a discharge lamp, which is connected in parallel with the capacitor, one end of the DC power source is grounded, and A discharge lamp lighting device, wherein an impedance element is inserted into at least a part of one end of a capacitor. 13. The discharge lamp lighting device according to claim 12, wherein at least one of the voltage and the current of the discharge lamp is detected from the ground terminal of the first series closed circuit by the differential detection means. 14. The discharge device according to claim 12, further comprising detection means for detecting the voltage across the capacitor of the second series closed circuit from the ground terminal of the first series closed circuit by differential amplification means. Electric lighting device. 15. A differential amplifying means is provided between a ground terminal of the first series closed circuit and a voltage generated across both ends of a current detecting resistor interposed between a capacitor of the second series closed circuit and a load circuit. The discharge lamp lighting device according to claim 12, further comprising detection means for detecting the discharge lamp. 16. The transformer comprises a third winding,
13. The discharge lamp lighting device according to claim 12, further comprising means for detecting a voltage corresponding to a load voltage from the third winding.