JPH097782A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE: To obtain a discharge lamp lighting device which can detect rapidly even though an abnormal connection is made at the output side of an inverter circuit, and can prevent the application of an excessive stress to discharge lamps. CONSTITUTION: In a preheating loop detecting circuit 10, the primary winding of a current transformer T3 for detecting the current flowing to a preheating loop is inserted in the preheating loop composed of the filaments f2 and f3 of discharge lamps La1 and La2 , and the secondary winding of a current transformer T3 . The secondary output of the current transformer T3 is connected to a preheating controller 9 as a detecting output. Consequently, when the current does not flow to the preheating loop, it is detected rapidly, and the output of the inverter circuit is controlled to prevent an excessive stress from being applied to the discharge lamps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp using an inverter circuit.

[0002]

2. Description of the Related Art In a discharge lamp lighting device for lighting a plurality of discharge lamps in series by an inverter circuit, a detection means for detecting connection of filaments of the discharge lamp is provided, and when there is no detection output, that is, when filaments are not connected. , A discharge lamp lighting device that puts the output of the inverter circuit in a low power state,
It is proposed as Japanese Patent Application No. 5-295029.

In this conventional example, in a discharge lamp lighting device having a preheating function, the output of an inverter circuit is prevented from increasing when there is no load with a simple circuit configuration. Next, this conventional example will be further described with reference to FIG. In this prior art apparatus, the inverter circuit 1 is connected to a DC power source E, the inverter circuit 1 includes a switching element Q _1, Q ₂ consisting of transistors, the input DC to the series circuit of the switching element Q _1, Q ₂ A voltage is applied. A resistor R ₁₄ is connected to the emitter of the switching element Q ₂ . In parallel with _one switching element Q ₁ , a series circuit of a direct current cut capacitor C ₁ , discharge lamps La ₁ and La ₂ , an inductance element L ₁ , and a primary winding n ₁ of a current transformer T ₁ for current feedback is provided. It is connected. First discharge lamp La ₁ filament f ₁ and the power supply side terminal d of the second discharge lamp La ₂ filaments f _4, e
A capacitor C ₂ for resonance is connected in parallel between the _two . This capacitor C ₂ may be a stray capacitance.
Non-power side terminal of the discharge lamp La ₂ filaments f ₄ through the primary winding of the current transformer T ₂ of the second parallel circuit and the preheating of the capacitor C ₄ and a resistor R ₈ of the discharge lamp La ₁ filament f ₁ It is connected to the non-power supply side terminal. The filaments f ₂ and f ₃ on the common connection side of both discharge lamps La ₁ and La ₂ form a series circuit, and the secondary winding of the current transformer T ₂ is connected to this series circuit via a capacitor C _5. is there. By the current transformer T ₂ , the resistor R ₈ and the capacitor C ₄ , the filaments f ₁ , f ₂ , f ₃ ,
A preheating circuit 7 for f ₄ is constructed.

Next, the configuration of the voltage detection circuit 2 will be described.
I do. DC cut capacitor C ₁One end of the invar
Is connected to the positive input terminal of
Capacitor C for cutting₁And the other end of the inverter circuit 1
Between the negative input terminal c of the discharge lamp La₁, La₂Yo
Very high impedance resistance R_Four, R_FiveSeries circuit
Has been continued. This resistance R_Four, R_FiveObtained at the connection point of
The voltage is the detection output of the voltage detection circuit 2.

Next, the configuration of the filament detection circuit 3 will be described. In this conventional example circuit, as described above, one end of the secondary winding of the current transformer T ₂ in the preheating circuit 7 is connected to the first discharge lamp La ₁ via the capacitor C _5.
Is connected to one end of the filament f ₂ in the second discharge lamp La ₂ and the other end of the secondary winding is connected to one end of the filament f _2.
3 is connected to one end, and the other ends of the filaments f ₂ and f ₃ are connected to each other. Connection point of the capacitor C ₅ and the filament f ₂ is connected to the positive input terminal b of the inverter circuit 1 through the resistor R _11. The capacitor C ₅ , the resistors R ₁₀ , R ₂₂ , the capacitor C _7, and the resistor R ₁₁ constitute the filament detection circuit 3, and the voltage at one end (point a) of the resistor R ₁₀ is detected by the filament detection circuit 3. It is output. The current transformer T ₁ for current feedback has two secondary windings n ₂ and n ₃ , and one secondary winding n ₂
Is connected between the base and emitter of the switching element Q ₁ via a bias resistor R ₁ , and the other secondary winding n
₃ is connected between the base and emitter of the switching element Q ₂ via a bias resistor R ₂ .

The drive circuit 5 is thus constructed.
You. Furthermore, between the input terminals b and c of the inverter circuit 1
Is the resistance R_ThreeAnd capacitor C _ThreeSeries circuit of is connected,
Resistance R_ThreeAnd capacitor C_ThreeDiac Q is the connection point of_ThreeTo
Through the switching element Q₂When connected to the base of
Both are switching elements Q₂Diode D on the collector of
_ThreeConnected via the anode and cathode of the. this
Resistance R_Three, Capacitor C_Three, Diac Q_ThreeAnd da
Iod D_ThreeConstitutes the starting circuit 6 of the inverter circuit 1.
doing. Switching element Q₁, Q ₂To Daio
Do D₁, D₂Are connected in anti-parallel, but these die
Aether D ₁, D₂Is not necessary.

On the other hand, in order to maintain the life of the discharge lamp for a long time, the pre-heating control is generally performed in which the output is kept low for a predetermined period after the operation of the inverter circuit and the pre-heating current is supplied to the filament when the discharge lamp is not lit. Is done in a regular manner. In this conventional example, the preheating control unit 9 performs the control. The inverter circuit control circuit 8 controls the output of the inverter circuit 1 so that the filament preheating mode (the mode in which the preheating current is supplied to the filament when the discharge lamp is not lit) is switched to the lighting mode.

Next, the operation of this conventional example will be described. The control power supply Vcc applied to the inverter circuit control circuit 8 and the preheating control unit 9 may be configured to be generated after the DC power supply E is applied to the inverter circuit 1. For example, a resistance to the DC power supply E, Zener diode is connected in series, and control power supply Vcc is supplied from the cathode of the Zener diode.
And a method of obtaining a control power supply Vcc from the feedback power from the secondary winding by providing a secondary winding on the resonance inductance element L ₁ of the inverter circuit 1. In the latter case, the control power supply Vcc can be obtained by connecting the inverter circuit 1. However, the description will be continued here in the former case.

When a DC voltage is applied to the inverter circuit 7 by the DC power supply E and a control power supply Vcc voltage is generated, the inverter circuit 1 is composed of a resistor R ₃ , a capacitor C ₃ , a diac Q ₃ and a diode D _3. The switching element Q ₂ is turned on by the starting circuit 6 and the current transformer T ₁ alternately turns on and off the switching elements Q ₁ and Q ₂ to start oscillation. To flow the emitter current I _E of the switching element Q ₂ is in this case the resistor R _14, the emitter voltage V _E of the switching element Q ₂ is, V _E
= (Resistance value of resistor R ₁₄ ) × (emitter current I _E ), and this emitter voltage V _E is the inverter circuit control circuit 8
Is input to the + terminal of the comparator CP ₁ . The reference voltage Vref determined by the resistors R ₁₆ , R ₁₇ , and R ₁₈ is input to the negative terminal of the comparator CP ₁ . Resistance R ₁₈
Is connected to the output of the preheat control unit 9, and when the output of the preheat control unit 9, that is, the output of the comparator CP ₂ is at “H” level, the reference voltage Vref is determined by the voltage division of the resistors R ₁₆ and R _17. , Vref ₁ . Comparator CP
When the output of ₂ is at the "L" level, the reference voltage Vref becomes Vref ₂ determined by the partial pressure of the combined resistance R of the resistor R ₁₆ resistors R _17, R _18, a Vref _1> Vref _2.

The input of the comparator CP ₂ of the preheating control unit 9 is − when the reference voltage V _R determined by the voltage division of the resistors R ₁₉ and R ₂₀ is −.
The charging voltage V _C of the capacitor C ₆ which is input to the terminal and which is determined by the time constant of the resistor R ₂₁ and the capacitor C ₆ is input to the + terminal. Charging of the capacitor C ₆ is started when the voltage of the control power supply Vcc is applied to the inverter circuit control circuit 8 and the preheating control section 9.

When V _C <V _R , the output of the comparator CP ₂ is at the “L” level, so the output of the comparator CP ₁ is a comparison of the input signals V _E and Vref ₂ , and V _E
<In Vref ₂ , since the output of the comparator CP ₁ is at “L” level, the base of the switching element Q ₇ is also “L”.
When V _E > Vref ₂ , the output of the comparator CP ₁ becomes “H” level, so that the current from the control power supply Vcc voltage to the base of the switching element Q ₇ via the resistor R _15. is supplied, the switching element Q ₇ at this time is turned on. the switching element Q ₇ of the inverter circuit 1 by turns on the switching element Q ₂
Of the switching element Q ₂
Turn off.

Here, the signal level of the input signal V _E and Vr
By properly setting the value of ef _2, the discharge lamp L
a ₁ and La ₂ are not lit, and filaments f ₁ to
Preheating of f ₄ is performed. When V _C > V _R , the output of the comparator CP ₂ is at “H” level, so that the input signals V _E and Vref ₁ are input to the comparator CP ₁ . The value of Vref ₁ is larger than the value of Vref ₂ , and by setting Vref ₁ > V _E , the output of the comparator CP ₁ is always at “L” level and the switching element Q ₇ is always off. In this case, the discharge lamps La ₁ and La ₂ are turned on.

Now, when power is supplied from the DC power supply E, the DC cut capacitor C ₁ is charged with a voltage E / 2 which is about half that of the DC power supply E. Therefore, the resistance R ₄ ,
The voltage divided by R ₅ becomes “H” level, and the detection output of the voltage detection circuit 2 becomes “H” level. Here, when at least one of the filaments f ₁ and f ₂ of the discharge lamps La ₁ and La ₂ is removed and put into a no-load state, the DC cut capacitor C ₁ is charged only in one direction via the resistors R ₄ and R _5. Then, the voltage is charged to the same voltage level as that of the DC power source E, so that the input voltage to the voltage detection circuit 2 becomes low and the detection output of the voltage detection circuit 2 becomes "L" level.

Next, when at least one of the filaments f ₂ and f ₃ of the discharge lamps La ₁ and La ₂ is disconnected, the detection output of the filament detection circuit 3 becomes "L" level.
Now, for example, if only the filament f ₃ is in a disengaged state, the filament f ₃ is disengaged, so that no current path is formed through the filaments f ₂ and f ₃ .
Further, in the current path that passes through the secondary winding of the current transformer T ₂ , since the direct current from the DC power source E is blocked by the capacitor C ₅ , this current path is not formed either. Thus eliminating current in resistor R ₁₀ flows, the potential of one end (a point) of the resistor R ₁₀ becomes "L" level.

That is, in this conventional example, the voltage detection circuit 2
In the filament detection circuit 3, all discharge lamps L
It is detected whether or not the filaments a ₁ and La ₂ are not connected, and when at least one filament is not connected, the electric charge of the capacitor C ₆ is extracted by the diode D ₇ or D ₈ and the filament preheating mode is set. This prevents an increase in the output of the inverter circuit 1 when the filament is not connected.

[0016]

By the way, it is often the case that the discharge lamp slightly discharges in the above-mentioned filament preheating mode. This is also affected by the ambient temperature and the like, and is likely to occur in a discharge lamp having a higher potential with respect to the ground, and in some cases, two discharge lamps connected in series may also occur.
In the above-mentioned conventional example, the discharge lamp La ₂ is in a state in which slight discharge is more likely to occur.

Here, considering the state where the connection points of the filaments f ₃ and f ₂ are disconnected, that is, in the actual lighting equipment, the socket and the lamp, the internal connection line connecting the sockets and the connection part of the socket, etc. are disconnected. Assuming that the discharge lamp La ₂ slightly discharges, the discharge lamp La ₂ itself has several kΩ.
Since it has an impedance of a certain degree, a current flows through the resistors R ₂₂ and R ₁₀ via this impedance, and the point a in the filament detection circuit 3 is in the “H” state. That is, even when the connection point between the filaments f ₃ and f ₂ is disconnected, the inverter circuit 1 switches the operation mode from the filament preheating mode to the lighting mode, so that the discharge lamp can be operated in a state where the preheating of the filaments f ₂ and f ₃ is not performed. L
There is a problem that a ₁ and La ₂ are turned on, the lamp life is extremely shortened, and at the same time, the preceding preheating function for originally maintaining the lamp life is not functioning at all.

The present invention has been made in view of the above problems, and an object of the present invention is to detect the connection abnormality of the output side of the inverter circuit promptly in the preheating mode. Disclosed is a highly safe discharge lamp lighting device capable of preventing an extra stress from being applied to the discharge lamp. An object of the invention of claim 2 is, in addition to the object of the invention of claim 1, is to provide a discharge lamp lighting device in which a current detecting means can be simply configured.

The object of the invention of claim 3 and the object of claim 4 is, in addition to the object of the invention of claim 1, in any of the connection parts of the common side filament of the discharge lamp during the lighting mode. An object of the present invention is to provide a discharge lamp lighting device capable of promptly detecting the occurrence of the occurrence of the above and preventing an extra stress from being applied to the discharge lamp. The object of the invention of claim 5 is, in addition to the object of the invention of claim 3, that a DC power supply boosted from a low-voltage power supply can be easily obtained, and the loss due to the resistance of the voltage detecting means is reduced. In order to provide an electric lighting device.

[0020]

In order to achieve the above object, in the invention of claim 1, a direct current power source, a plurality of preheating type discharge lamps connected in series, and a discharge source connected to the direct current power source are provided. An inverter circuit for supplying electric power to the electric lamp, and a preheat control unit for controlling the output of the inverter circuit so as to change from a filament preheating mode for supplying low electric power to the discharge lamp to a lighting mode for supplying high electric power. And a control circuit, wherein a filament on the common connection side of a pair of discharge lamps that are phase-connected among the discharge lamps has a preheating loop with the filament and a voltage source for preheating insulated from the inverter circuit. The preheating loop is provided with a current detecting means for detecting a current flowing in the preheating loop, and the preheating control section detects the current of the current detecting means during the filament preheating mode. It is characterized in that for controlling the output of the inverter circuit below the filament preheat mode if Kere.

According to a second aspect of the present invention, in the first aspect of the present invention, the current detecting means is constituted by a current transformer for inserting a primary winding in the preheating loop. According to a third aspect of the present invention, in the first aspect of the present invention, the inverter circuit includes a conversion means for converting a DC power source into a high frequency by switching a switching element, and an output between the conversion means and one end of the discharge lamp series circuit. First connected to
A direct current cut capacitor exists, the second direct current cut capacitor is inserted and connected in the preheating loop, and the other end of the filament on the common connection side of the discharge lamp on the first direct current cut capacitor side is A voltage detecting means for detecting a voltage between one end of the discharge lamp that is not directly connected to the filament on the common connection side and one end of the second DC cut capacitor, and the other of the second DC cut capacitor side. A connection point between the end and one end of the common connection side filament of the other discharge lamp that is not directly connected to the common connection side filament of the discharge lamp on the side of the first DC cutting capacitor, and a positive electrode of the DC power source. And a resistor is inserted between the side and the preheating control section, during the lighting mode there is no current detection of the current detection means or the detection voltage of the voltage detection means is below a predetermined value. It is characterized in that for controlling the output of the inverter circuit below the filament preheating mode when.

According to a fourth aspect of the present invention, in the first aspect of the present invention, one end of the filament on the common connection side of one of the pair of discharge lamps connected in phase and the filament on the common connection side of the other discharge lamp. And a second current detecting means between the other end of the common connection side filament of the one discharge lamp and the other end of the common connection side filament of the other discharge lamp. A detection means is provided, and the preheat control unit sets the output of the inverter circuit to a filament or less if no current is detected by any of the current detection means during the lighting mode.

According to a fifth aspect of the present invention, in the third aspect of the present invention, the DC power supply is configured by a step-up chopper circuit, and one end of the resistor is connected to an input side of a switching element that constitutes the step-up chopper circuit. It is what

[0024]

According to the invention of claim 1, a direct current power source, a plurality of preheating type discharge lamps connected in series, an inverter circuit connected to the direct current power source and supplying electric power to the discharge lamp, And a control circuit having a preheating control unit for controlling the output of the inverter circuit so that the filament preheating mode for supplying low power to the discharge lamp is changed to the lighting mode for supplying high power. The filament on the common connection side of the pair of discharge lamps that are phase-connected to each other forms a preheating loop with the filament and a voltage source for preheating insulated from the inverter circuit, and the preheating loop includes a preheating loop. Current detecting means for detecting a current flowing through the preheating control section is provided, and the preheating control section outputs the output of the inverter circuit to the filament preheating mode if no current is detected by the current detecting means. Since it is controlled below the preheat mode, even if there is a connection abnormality on the output side of the inverter circuit in the preheat mode, it is detected promptly and the output of the inverter circuit is controlled so that extra stress is not applied to the discharge lamp. Therefore, the life of the discharge lamp is not impaired, and the pre-heating function is not impaired, the life of the discharge lamp is extended, and since the discharge lamp does not light, the user can be notified of a connection abnormality. it can.

According to the invention of claim 2, in the invention of claim 1, the current detecting means is constituted by a current transformer for inserting a primary winding in the preheating loop.
The configuration of the current detection means becomes simple. According to a third aspect of the present invention, in the first aspect of the present invention, the inverter circuit includes a conversion unit that converts a DC power supply into a high frequency by switching a switching element, an output of the conversion unit, and one end of a discharge lamp series circuit. There is a first DC cut capacitor connected between the two, and a second DC cut capacitor is inserted and connected in the preheating loop, and a common connection of the discharge lamps on the first DC cut capacitor side is made. A second voltage cut-off means for detecting the voltage between one end of the second DC cut capacitor, which is not directly connected to the common-connection side filament of the other discharge lamp, and the second DC cut-off capacitor; Of the first end of the other end of the DC cut capacitor side and the common connection side filament of the other discharge lamp.
A resistor is inserted between the connection point between the common side of the discharge lamp of the DC cut capacitor side and the one end that is not directly connected, and the positive side of the DC power supply, and the preheat control unit is operated during the lighting mode. It is characterized in that the output of the inverter circuit is controlled to a filament preheating mode or less when there is no current detection of the current detection means or when the detection voltage of the voltage detection means becomes less than or equal to a predetermined value. In addition, in the lighting mode, the output of the inverter circuit can be controlled so that extra stress is not applied to the discharge lamp even if a connection abnormality occurs in any connection portion of the filaments on the common connection side of the discharge lamp.

According to the invention of claim 4, in the invention of claim 1, one end of the filament on the common connection side of one discharge lamp of the pair of discharge lamps connected in phase and the common connection of the other discharge lamp. A first current detection means is provided between the one end of the side filament and the second end between the other end of the common connection side filament of the one discharge lamp and the other end of the common connection side filament of the other discharge lamp. In the same manner as the invention of claim 3, since the output of the inverter circuit is equal to or less than the filament if the current detection means is provided and the current detection means does not detect the current in any of the current detection means during the lighting mode. In addition to the preheat mode, the output of the inverter circuit is controlled so that no extra stress is applied to the discharge lamp when a connection abnormality occurs in any connection part of the filament on the common connection side of the discharge lamp during the lighting mode. It is possible.

According to the invention of claim 5, in the invention of claim 3, a DC power supply of a predetermined voltage can be easily obtained even if a low voltage power supply is used, and one end of the resistor is boosted. Since it is connected to the input side of the switching element that constitutes the chopper circuit, the loss of resistance can be reduced.

[0028]

Embodiments of the present invention will now be described with reference to the drawings.
I do. (Embodiment 1) FIG. 1 shows a circuit configuration of this embodiment.
This embodiment is an alternative to the conventional filament detection circuit 3.
In addition, the preheating loop detection circuit 10 is used. this
The preheating loop detection circuit 10 is a discharge lamp La.₁, La₂Common
Filament f on the connection side₂, F _ThreeAnd current transformer T
₂The preheating loop consists of the secondary winding of the
Current transformer T for detecting current flowing in_ThreePrimary winding
Insert this current transformer T_ThreeDie on the secondary winding of
Audebridge DB₁Connect to rectify the secondary output,
The rectified output of the resistor R_{twenty two}And resistance R_TenDivide with and then connect
The point a is connected to the diode D as in the conventional example of FIG.₈Through
It is configured to be connected to the heat control unit 9.

Since the other structure is the same as that of the conventional example shown in FIG. 7, the same symbols and numbers are given to the same constituent elements as those of the conventional example, and the description thereof is omitted. Therefore, in the circuit of this embodiment, when the discharge lamps La ₁ and La ₂ are normally connected, the discharge lamp L ₁ is connected to the discharge lamp L from the secondary winding of the current transformer T _2.
A preheating loop in which a preheating current flows is formed in the filaments f ₂ and f ₃ of a ₁ and La ₂ , and therefore, the two of the current transformer T ₃ in which the primary winding is inserted in the preheating loop.
An output voltage is generated in the next winding, and the potential at the connection point a becomes "H" level.

Therefore, as in the conventional example, if the output of the voltage detection circuit 2 is at "H" level, it is possible to shift from the filament preheating mode to the lighting mode. On the other hand, when no current flows in the primary winding of the current transformer T _3, an output voltage is not generated in the secondary winding, so that the potential at the connection point a becomes “L” level. Even if a minute current flows in the preheating loop, the voltage generated in the secondary winding is very small, so the potential at the connection point a is very small and can be regarded as the “L” level.

When the operation mode of the inverter circuit 1 is in the filament preheating mode with the connection points of the filaments f ₂ and f ₃ disconnected, even if the discharge lamp La ₂ is slightly discharged, a small amount of current flows through the current transformer T _3. , The potential at the connection point a becomes "L" level. That is, it is possible to detect that the preheating loop is not formed normally.

Thus, the filament f₂, F_ThreeIn
No matter which connection point is disconnected, the connection point a is at "L" level.
Therefore, the diode D of the preheating control unit 9₈By Conde
Sensor C₆The electric charge of the filament from the preheating mode
Prevent transition to lighting mode. Therefore the filament
Increase the output of the inverter circuit 1 when not connected
Can be prevented and adversely affect lamp life
There is no. Of course, the operation of the voltage detection circuit 2 is similar to that of the conventional example.
Discharge lamp La₁, La₂Filament f ₁, F₂
If at least one of the
Flow cut capacitor C₁Is the resistance R_Four, R_FiveThrough
It is charged only in one direction and has the same voltage level as DC power supply E.
Input voltage to the voltage detection circuit 2 is low
Therefore, the detection output of the voltage detection circuit 2 becomes "L" level.
You. Therefore, the diode D of the preheat control unit 9₇By con
Densa C₆The electric charge of the filament to preheat mode
From flashing to lighting mode
Output can be prevented if the switch is not connected.
it can.

Since the other circuit operations are the same as those of the conventional example, the description thereof will be omitted. (Embodiment 2) FIG. 2 shows a circuit of the present embodiment, and the voltage detection circuit 2 and the capacitor C ₂ in the embodiment 1 are removed as shown in the drawing. Then, the filaments f ₂ , f on the common connection side of the discharge lamps La ₁ , La _2
A secondary winding is provided on the inductance element L ₁ of the inverter circuit 1 as a power source for preheating ₃ , and the secondary winding, the capacitor C ₅ , the filaments f ₂ and f _3, and the secondary winding of the current transformer T ₃ are provided. A preheating loop is formed by the wire and the preheating current is passed through the filaments f ₂ and f ₃ by the output voltage of the secondary winding of the inductance element L ₁ . In addition to the preheating loop detection circuit 10, a DC cut capacitor C
A preheating loop detection circuit 11 for detecting the voltage of ₁ is provided. The present embodiment is different from the first embodiment in the above points. Since other configurations are the same as those of the first embodiment (conventional example of FIG. 7), the same symbols and numbers are given to the same components as those of the first embodiment, and the description thereof will be omitted.

Here, the preheating loop detection circuit 11 includes a connection point between the DC cut capacitor C ₁ and the positive electrode of the DC power source E, the second DC cut capacitor C ₅ and the secondary winding of the inductance element L _1. A resistor R ₁₁ is connected between the two ends, and the other end of the capacitor C ₅ is connected to the resistor R ₂₃ , the resistor R ₂₄ and the capacitor C 5.
₈ is connected to the negative electrode of the DC power supply E via a parallel circuit, and the connection point of the resistors R ₂₃ and R ₂₄ is connected to the preheat control unit 9 via the diode D ₇ as a detection output point. Thus, in this embodiment, even if _one of the filaments f ₁ and f ₄ of the discharge lamps La ₁ and La ₂ is disconnected, the filament f _{1
Since 1} and f ₄ are included in the series resonance loop of the inverter circuit 1, the series resonance loop is not formed and the inverter circuit 1 does not operate. Therefore, a problem such as an increase in the output of the inverter circuit 1 does not occur.

On the other hand, the filaments f ₂ and f ₃ on the common connection side
When the connection point of is disconnected, the operation of the inverter circuit 1 is controlled by the following operation so as not to shift to the lighting mode, which does not adversely affect the lamp life and does not light to the user. By doing so, it is possible to immediately notify the connection abnormality. In other words, points A, B, and C in FIG. 3 can be considered as locations where connection abnormality occurs in the connection portion of the filaments f ₂ and f ₃ .

Then, after the discharge lamps La ₁ and La ₂ are lit in the lighting mode and the point C or the point B is deviated,
Since the lamp current flows through point A, preheat loop detection circuit 1
No current flows in the secondary winding of the current transformer T ₃ of 0, and the connection point a becomes “L” as in the first embodiment. Therefore, the operation mode of the inverter circuit 1 is changed by the operation of the preheating control unit 9. The filament preheating mode is set to prevent the output of the inverter circuit 1 from increasing.

On the other hand, when the point A is deviated, the lamp current is
Current transformer T_ThreeSince it flows to the secondary winding of
The loop detection circuit 10 does not operate, but the preheat loop detection circuit
11 operates as follows. First the preheating loop is formed
Capacitor C when_FiveVoltage V across₁Is a philame
Input f₂, F_Three, Inductance element L₁Secondary winding,
Current transformer T _ThreeVoltage drop of the secondary winding of
It is almost 0V. If point A deviates here, the potential at point B
Is a capacitor C to maintain a fixed state._FiveNo
Anti-R₁₁The side remains at this potential. On the other hand, resistance R₁₁, Con
Densa C_Five, Resistance R_{twenty three}, R_{twenty four}Because a direct current flows through
Capacitor C_FiveThe electric charge is being charged. At the same time
DC cut capacitor C₁The voltage across both ends of the
Good. Thus the capacitor C₁, C_FiveVoltage rises
The resistance R_{twenty three}, R_{twenty four}Potential at the connection point of
To "L", and as a result, the diode of the preheat control unit 9
D₇Capacitor C₆Extract the electric charge of
Prevent the transition from preheat mode to lighting mode. Follow
Inverter when the filament is not connected
It is possible to prevent an increase in the output of the path 1.

Since the other circuit operations are the same as those of the conventional example,
Description is omitted. (Embodiment 3) FIG. 4 shows a circuit of this embodiment.
In the embodiment, the replacement of the preheating loop detection circuit 11 in the second embodiment is performed.
Instead, the filament f₂, F_ThreeConnect the non-power supply side ends of
Current transformer T to the circuit that continues₃₀Insert the secondary winding of
Turn on, current transformer T ₃₀The secondary output of
Ridge DB₂Full-wave rectified by the full-wave rectified voltage
Is the resistance R₃₀And the resistance R₃₁And capacitor C₃₀Parallel circuit of
The voltage is divided by and the divided output is diode D₃₁In through
Second preheat loop detection connected to burner circuit control circuit 8
Circuit 12 and configuration of inverter circuit control circuit 8
Is different from Embodiments 1 and 2 in that
2 and is different from the preheating loop detection circuit 12
It detects the disconnection at point A.
Since the other configurations are the same as those of the second embodiment, the second embodiment
The same numbers and symbols are attached to the same components as
The description is omitted.

Next, the operation of the inverter circuit 1 by the inverter circuit control circuit 8 in this embodiment will be described. In the inverter circuit control circuit 8, immediately after the DC power source E is turned on, the potential of the capacitor C ₈ becomes approximately 0 V due to the time constant with the resistor R ₂₃ . Therefore, switching element Q
₈ less than the gate voltage breakover voltage of the switching element Q ₈ is turned off, so that the DC power source E and the inverter circuit 1 is connected via a resistor R _24. Due to this voltage drop across the resistor R ₂₄ , the inverter circuit 1
Since a voltage lower than the voltage of the DC power source E is applied to, the resonance of the inverter circuit 1 is weakened. The output voltage when the resonance is weakened is determined by the discharge lamp La ₁ ,
If the level at which La ₂ does not light up is set, the discharge lamps La ₁ ,
Only the preheating of the filaments f _{1 to} f ₄ of La ₂ will be performed.

Eventually the capacitor C₈Is charged and
Holding element Q₈If the breakover voltage of
Switching element Q₈Is turned on, the inverter circuit 1
Is the voltage of the DC power supply E is the switching element Q₈Through the sign
Be added. Either point A, point B or point C is not connected
If not, the detection points of the preheating loop detection circuits 10 and 12
The anode is the capacitor of the inverter circuit control circuit 8
C ₈Diode D connected to₈, D₃₀The cathode of
It is connected. And resistance R_{twenty three}, R_Ten, R₃₁Resistance value
R_{twenty three}≫R_Ten, R₃₁And the switching element
Child Q₈The current flowing through the gate of can be maintained in the ON state
Switching element Q smaller than current₈Off,
The output of the inverter circuit 1 is reduced.

In the present embodiment as well, regardless of the filament preheating mode or the lighting mode, any abnormal connection can be detected. (Embodiment 4) FIG. 5 shows this embodiment, which is different from Embodiment 2 in that a step-up chopper circuit is used as a DC power source E as shown in the drawing. The other configuration is the second embodiment.
Therefore, the same components as those of the second embodiment are designated by the same reference numerals and symbols, and the description thereof will be omitted.

The step-up chopper circuit constituting the DC power source E controls ON / OFF of the switching element Q ₁₀₀ by the chopper control circuit 13, and when it is on, the AC power source AC causes the inductance element via the filter choke L ₁₀₁ and the diode bridge DB _100. to accumulate energy in the L _{10 0,}
When off, the energy stored in the inductance element L ₁₀₀ is discharged to the capacitor C ₁₀₁ via the diode D ₁₀₀ and charged, and a DC voltage is obtained by the charging voltage. The voltage across the switching element Q ₁₀₀ is a high frequency rectangular wave voltage whose peak is the chopper output voltage.

[0043] Then connected to the drain of the switching element Q ₁₀₀ a connection point of the resistor R ₁₁ in the preheating loop detection circuit 11 via the diode D _101, is aimed to reduce the loss in the resistor R _11. Since the other configurations and operations are the same as those in the second embodiment, the description thereof is omitted here.

(Embodiment 5) FIG. 6 shows a circuit of this embodiment. In this embodiment, the series resonant circuit is connected to both ends of the switching element Q ₁ of the inverter circuit 1 in the embodiment 3. On the other hand, it is different in that a series resonance circuit is connected to both ends of the switching element Q ₂ . Since the other configurations and operations are the same as those in the second embodiment, they are omitted here.

[0045]

According to the invention of claim 1, a direct current power source, a plurality of preheating type discharge lamps connected in series, an inverter circuit connected to the direct current power source and supplying electric power to the discharge lamp, And a control circuit having a preheating control unit for controlling the output of the inverter circuit so that the filament preheating mode for supplying low power to the discharge lamp is changed to the lighting mode for supplying high power. The filament on the common connection side of the pair of discharge lamps that are phase-connected to each other forms a preheating loop with the filament and a voltage source for preheating insulated from the inverter circuit, and the preheating loop includes a preheating loop. Current detecting means for detecting a current flowing through the preheating control section is provided, and the preheating control section outputs the output of the inverter circuit to the filament preheating mode if no current is detected by the current detecting means. Since it is controlled below the preheat mode, even if there is a connection abnormality on the output side of the inverter circuit in the preheat mode, it is detected promptly and the output of the inverter circuit is controlled so that extra stress is not applied to the discharge lamp. Therefore, the life of the discharge lamp is not impaired, and the pre-heating function is not impaired, the life of the discharge lamp is extended, and since the discharge lamp does not light, the user can be notified of a connection abnormality. The effect is that you can do it.

According to a second aspect of the present invention, in the first aspect of the present invention, the current detecting means is constituted by a current transformer for inserting a primary winding in the preheating loop, so that the structure of the current detecting means is simplified. There is an effect. Claim 3
In the invention of claim 1, in the inverter circuit, the inverter circuit is connected between a conversion means for converting a DC power supply into a high frequency by switching a switching element, and the conversion means output and one end of a discharge lamp series circuit. There is a first direct current cut capacitor, and a second direct current cut capacitor is inserted and connected in the preheating loop, and both ends of the filament on the common connection side of the discharge lamp on the side of the first direct current cut capacitor are connected. A second DC cut capacitor, which comprises voltage detection means for detecting a voltage between one end of the other discharge lamp that is not directly connected to the common connection side filament and one end of the second DC cut capacitor, And the other end of the common connection side filament of the other discharge lamp and the common connection side filament of the discharge lamp on the side of the first DC cutting capacitor. A resistor is inserted between the connection point with one end that is not connected and the positive electrode side of the DC power supply, and the preheating control unit does not detect the current of the current detection unit during the lighting mode or the voltage detection unit. Since the output of the inverter circuit is controlled to a filament preheating mode or lower when the detected voltage becomes a predetermined value or less, any filament on the common connection side of the discharge lamps in the lighting mode is used in addition to the preheating mode. There is an effect that the output of the inverter circuit can be controlled so that extra stress is not applied to the discharge lamp even if a connection abnormality occurs at the connection part of the above.

According to a fourth aspect of the present invention, in the first aspect of the present invention, one end of the filament on the common connection side of one of the pair of discharge lamps connected in phase and the filament on the common connection side of the other discharge lamp. And a second current detecting means between the other end of the common connection side filament of the one discharge lamp and the other end of the common connection side filament of the other discharge lamp. A detection means is provided, and the preheat control section sets the output of the inverter circuit to a filament or less if there is no current detection by any current detection means during the lighting mode. In addition to the above, the output of the inverter circuit should be controlled so that no extra stress is applied to the discharge lamp in the lighting mode even if a connection abnormality occurs at any connection part of the filament on the common connection side of the discharge lamp. There is an effect that can be.

According to the invention of claim 5, in the invention of claim 3, a DC power supply of a predetermined voltage can be easily obtained even if a low voltage power supply is used, and one end of the resistor is a boost chopper circuit. Since it is connected to the input side of the switching element constituting the above, there is an effect that the loss of resistance can be reduced.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

FIG. 3 is a circuit diagram for explaining the above operation.

FIG. 4 is a circuit diagram of Embodiment 3 of the present invention.

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

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional example.

[Explanation of symbols]

1 Inverter circuit 2 Voltage detection circuit 5 Driving circuit 6 Start circuit 7 Preheating circuit 8 Inverter circuit control circuit 9 Preheating control unit 10 Preheating loop detection circuit La ₁ discharge lamp La ₂ discharge lamp f _{1 to} f ₄ filament Q ₁ and Q ₂ switching Element Q ₇ Switching element T ₂ Current transformer T ₃ Current transformer

Claims (5)

[Claims] 1. A direct current power source, a plurality of preheating type discharge lamps connected in series, an inverter circuit connected to the direct current power source and supplying power to the discharge lamp, and low power consumption for the discharge lamp. And a control circuit having a preheating control unit for controlling the output of the inverter circuit so as to be in a lighting mode for supplying high electric power from a filament preheating mode for supplying electric power. The filament on the common connection side of the discharge lamp constitutes a preheating loop with the filament and a voltage source for preheating insulated from the inverter circuit, and the preheating loop has a current for detecting a current flowing in the preheating loop. A detecting means is provided, and the preheating control section outputs the output of the inverter circuit to the filament preheating mode or less if there is no current detection of the current detecting means during the filament preheating mode. The discharge lamp lighting device and controls. 2. The current detecting means is provided in the preheating loop.
The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device comprises a current transformer into which a secondary winding is inserted. 3. The inverter circuit includes a conversion means for converting a DC power supply into a high frequency by switching a switching element, and a first DC cutoff connected between the conversion means output and one end of a discharge lamp series circuit. And a second DC-cutting capacitor is inserted and connected in the preheating loop, and another discharge lamp is provided at both ends of the filament on the common connection side of the discharge lamps on the first DC-cutting capacitor side. A voltage detection means for detecting a voltage between one end of the common connection side not directly connected to the filament and one end of the second DC cut capacitor, and the other end of the second DC cut capacitor side, One end of both ends of the common connection side filament of the other discharge lamp that is not directly connected to the filament on the common connection side of the discharge lamp on the side of the first DC cutting capacitor and A resistor is inserted between the connection point and the positive electrode side of the DC power supply, and the preheat control unit detects that no current is detected by the current detection unit during the lighting mode or the detected voltage of the voltage detection unit is equal to or less than a predetermined value. The discharge lamp lighting device according to claim 1, wherein the output of the inverter circuit is controlled to be equal to or lower than the filament preheating mode when the temperature becomes low. 4. A first current detecting means between one end of a common connection side filament of one discharge lamp and one end of a common connection side filament of the other discharge lamp of a pair of discharge lamps connected in phase. And a second current detecting means is provided between the other end of the common connection side filament of the one discharge lamp and the other end of the common connection side filament of the other discharge lamp, and the preheating control unit is configured to perform the lighting. 2. The discharge lamp lighting device according to claim 1, wherein the output of the inverter circuit is set to a filament or less if no current is detected by any of the current detecting means during the mode. 5. The discharge lamp lighting device according to claim 3, wherein the DC power supply is composed of a step-up chopper circuit, and one end of the resistor is connected to an input side of a switching element forming the step-up chopper circuit.