JPH07249496A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent light emission at the end of a discharge lamp while a sufficient preheating current is supplied, by furnishing means capable of controlling the outputs of an inverter circuit and an AC-DC converter circuit and also the impedance of a load circuit. CONSTITUTION:A control circuit X makes output control of an inverter circuit B to turn off a discharge lamp La. At the time, the output voltage VDC of an AC-DC converter circuit A is dropped to lessen the current in a closed loop following a grounding circuit Y, filter circuit F, AC-DC converter circuit A, inverter circuit B, load circuit Z, discharge lamp La, discharge lamp tube wall, floating capacitance CX, and the grounding circuit Y, which is conducted to a degree at which fine discharging likely generated at the tube end of the lamp La does not occur. The inverter circuit B supplies a power as a preheating current, to a degree at which the discharge lamp La does not light up. According to this constitution, a sufficient preheating current can be supplied as provision for the next restart, and light emission at the tube end of the lamp La can be prevented.

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 at a high frequency.

[0002]

2. Description of the Related Art FIG. 14 is a block diagram showing a conventional example according to the present invention.

In this conventional example, an _earth circuit Y is connected to both ends of an AC power supply V _ac for ensuring safety and reducing noise.
A filter circuit F for reducing noise is connected to the output end of the earth circuit Y, an AC-DC converter A is connected to the output end of the filter circuit F, and an output end of the AC-DC converter A is connected. Connect the inverter circuit B that outputs high-frequency power to the inverter
The parallel circuit of the load circuit Z and the discharge lamp La is connected to the output end of the output circuit B. Also, A - scan circuit Y includes a series circuit of a capacitor C _1, C _2, from the connection point of the capacitor C _1, C ₂ instrument A - is connected to the scan. Further, the switching element in the inverter circuit B is driven by the control circuit X, and the signal of the control circuit X is changed by receiving the dimming signal S ₁ .

Next, the operation will be briefly described with reference to FIG. First, the dimming signal S ₁ shown in FIG.
When a predetermined level is reached at time t ₀ , the preheating current I _f of the filament of the discharge lamp La shown in FIG. 15 (c) is reduced so that the lamp current I of the discharge lamp La shown in FIG. 15 (d) is obtained. _la decreases to zero, and the discharge lamp La is turned off. Also,
AC As shown in FIG. 15 (b) - the output voltage V _DC of the DC transformer A is always constant, t ₀ ~t between ₁ AC - Output voltage V _DC of the DC transformer A is inverter - capacitor circuit B Is input to the inverter circuit B and the control circuit X is driven, the inverter circuit B
Supplies electric power to the discharge lamp La and the filament of the discharge lamp La such that the discharge lamp La does not light. And time t
_In order to prepare for the next restart after ₁ onward, as shown in FIG. 15C, the preheating current _If having a value slightly larger than that between the times t _{0 and} t ₁ is supplied.

With this operation, even after the discharge lamp La is surely turned off, a sufficient preheating current I _f is prepared for the next restart.
Can be supplied.

[0006]

By the way, when the above-described discharge lamp lighting device is constructed as a lighting fixture, as shown in FIG. 16, the output light of the discharge lamp La provided on a part of the surface of the fixture K is used. When the reflecting plate J has a reflecting and conductive property, the reflecting plate J is at the same potential as the instrument ground, and the reflecting plate J is close to the discharge lamp La, the instrument is as shown in FIG. There is a stray capacitance C _X between K, especially the reflector J and the tube wall of the discharge lamp La. That is, the stray capacitance C _X exists between the instrument ground and the tube wall of the discharge lamp La.

In this case, in this device, as shown in the block diagram of FIG. 17, an earth circuit Y → filter circuit F → AC-DC converter A → inverter circuit B → load circuit Z → discharge lamp. There is an electrically closed loop of La → the wall of the discharge lamp La → floating capacitance C _X → earth circuit Y. Therefore, when a current flows through the closed loop, the discharge lamp La causes a slight discharge even though the discharge lamp La is surely turned off, and the tube end of the discharge lamp La emits light. There is a problem, and when the discharge lamp lighting device shown in the above-mentioned conventional example is used for performance, it is very unsightly.

To solve this problem, for example, by stopping the operation of the inverter circuit B and cutting the closed loop, it is possible to prevent light emission from the tube end of the discharge lamp La. However, at the same time, the preheating current _If to the filament of the discharge lamp La is cut off, which causes a problem that the next restart cannot be instantaneously performed.

The present invention has been made in view of the above problems, and an object thereof is to sufficiently preheat the filament of the discharge lamp in preparation for the next restart after the discharge lamp is reliably turned off. It is an object of the present invention to provide a discharge lamp lighting device capable of preventing light emission from the tube end of a discharge lamp while supplying a current.

[0010]

In order to solve the above-mentioned problems, the present invention according to claim 1 provides an earth circuit connected to both ends of an alternating current power source and both ends of the alternating current power source via the earth circuit. An AC-DC conversion circuit connected to, and an inverter circuit that converts the output power of the AC-DC conversion circuit into high-frequency power,
It has a parallel circuit of a load circuit and a discharge lamp connected to the output end of the inverter circuit, a control circuit for controlling the inverter circuit, and preheating power supply means for supplying preheating power to the filament of the discharge lamp. However, in a discharge lamp lighting device in which stray capacitance exists between the tube wall of the discharge lamp and the ground circuit, the power supplied to the discharge lamp from the inverter circuit and the preheating power supply means is substantially In addition, an inverter circuit, an AC / DC conversion circuit, and a means for controlling the impedance of the load circuit are provided so that the discharge lamp can be controlled to a level at which it is turned off.

According to a second aspect of the invention, the means capable of controlling the electric power supplied from the inverter circuit to the discharge lamp to a level at which the discharge lamp is substantially turned off is a means for short-circuiting both ends of the discharge lamp. It is characterized by having done.

According to a third aspect of the present invention, the means capable of controlling the power supplied from the inverter circuit and the preheating power supply means to the discharge lamp to a level at which the discharge lamp is substantially turned off is provided at both ends of the discharge lamp. It is characterized in that it is a means for reducing the voltage.

According to a fourth aspect of the present invention, the means for supplying electric power from the inverter circuit and the preheating power supply means to the discharge lamp is a means for insulating the preheating power supply means from the filament of the discharge lamp, or an inverter. It is characterized in that at least one of the means for insulating the battery circuit and the discharge lamp is used.

[0014]

According to the first aspect of the present invention, the power supplied from the inverter circuit and the preheating power supply means to the discharge lamp is
The discharge lamp is turned off by providing a means capable of controlling the inverter circuit, the AC-DC conversion circuit, and the impedance of the load circuit so that the discharge lamp can be controlled to a level at which the discharge lamp is substantially turned off. Therefore, the output of the inverter circuit can be lowered, and at the same time, a preheating current sufficient to preheat the filament of the discharge lamp can be supplied.

According to the second aspect of the present invention, the means capable of controlling the electric power supplied from the inverter circuit to the discharge lamp to a level at which the discharge lamp is substantially turned off short-circuits both ends of the discharge lamp. By means of the means, the voltage across the discharge lamp can be set to zero in order to turn off the discharge lamp, and at the same time, a sufficient preheating current for preheating the filament of the discharge lamp can be supplied.

According to the third aspect of the invention, the means capable of controlling the power supplied from the inverter circuit and the preheating power supply means to the discharge lamp to a level at which the discharge lamp is substantially turned off is the discharge lamp. Is a means for lowering the voltage across the discharge lamp, it is possible to reduce the voltage across the discharge lamp in order to turn off the discharge lamp, and at the same time supply a preheating current sufficient to preheat the filament of the discharge lamp.

According to the fourth aspect of the present invention, the means for supplying electric power from the inverter circuit and the preheating power supply means to the discharge lamp is means for insulating the preheating power supply means and the filament of the discharge lamp, or By being at least one of the means for insulating the inverter circuit and the discharge lamp,
It is possible to prevent a current from flowing between the preheating power supply means and the filament of the discharge lamp, or between the inverter circuit and the discharge lamp, and to adjust the voltage across the discharge lamp to turn off the discharge lamp. At the same time, it is possible to supply a sufficient preheating current to preheat the filament of the discharge lamp.

[0018]

【Example】

(Embodiment 1) FIG. 1 is a block diagram showing a first embodiment according to the present invention, and is different from the conventional example shown in FIG.
In addition to controlling the output of the inverter circuit B so that the discharge lamp La is turned off, the output control of the AC-DC converter A,
Alternatively, the impedance value of the load circuit Z is controlled, and other configurations are the same as those of the conventional example.
Description is omitted by attaching the same reference numerals to the same components.

Next, referring to FIG. 2, the operation of this circuit will be simplified.
explain. First, as shown in FIG. 2A, the dimming signal S₁
Rises at time t₀When a certain level is reached at
As shown in (c), preheating electricity of the filament of the discharge lamp La
Flow I _fBy squeezing the lamp, as shown in Fig. 2 (d), the lamp
Current I_laAnd the discharge lamp La is turned off. At that time,
As shown in FIG. 2B, the output voltage of the AC-DC transformer A
V_DCLower. Output voltage V of AC-DC transformer A_DC
Of the ground circuit Y → fill shown in the conventional example.
Circuit F → AC-DC converter A → inverter circuit B → negative
Packing circuit Z → discharge lamp La → tube wall of discharge lamp La → stray capacitance C
_X→ The current that flows in the electrically closed loop called the ground circuit Y
The amount of light is reduced and a slight discharge does not occur at the tube end of the discharge lamp La.
Repeat up to.

Even after the time t ₁ , the inverter circuit B supplies the electric power to the extent that the discharge lamp La does not light up, and the preheating current I _f having a value slightly larger than that between the times t ₀ and t _1. Supply.

With this operation, after the discharge lamp La is reliably turned off, the preheating current _If can be supplied in preparation for the next restart, and the emission of light from the tube end of the discharge lamp La can be prevented. A specific circuit diagram of this embodiment is shown in FIG. 3, and will be briefly described below.

The filter circuit F in the diagram shown in FIG.
The inductor L _F is connected to the power supply line, and the capacitor C _F is connected to both ends of the AC power supply V _ac via the inductor L _F. The AC-DC converter A has a rectifier DB that rectifies the AC power _Vac via the filter circuit F, and
It comprises a boost chopper circuit that boosts and smoothes the rectified voltage, and a control IC (G) that controls the switching element Q ₁ of the boost chopper circuit. Boost chopper circuit includes an inductor L ₁ connected in series to the positive side of the output end of the rectifier DB, a switching element Q ₁ which is connected in parallel to the rectifier DB through the inductor L _1, the inductor L ₁ and the switching element Q A diode connected in series to the contact with _1.
Consists de D ₁ Prefecture, the rectified input voltage by a rectifier DB, and boosted by on-off switching element Q _1. The voltage smoothed by the capacitor C ₄ connected in parallel to the output terminal of the step-up chopper circuit is input to the inverter circuit B.

Control of ON / OFF of switching element Q ₁ I
C (G) is, for example, IC manufactured by Motorola (MC3426).
1) can be used, and the output signal of the control IC (G) is controlled by inputting the input voltage rectified by the rectifier DB to the 3rd pin of the control IC (G), or to the 5th pin. The current flowing in the secondary winding of the inductor L ₁ is input, the current flowing in the switching element Q ₁ is input to the 4th pin, and the output voltage V _DC of the AC-DC converter A is fed back to the 1st pin. By doing. here,
Resistors R ₄ , R ₅ , R connected across the capacitor C ₄
By short-circuiting both ends of the resistor R _{6 in} the series circuit of ₆ with the switching element Q ₄₁ , the voltage to the control IC (G) is fed.
The feedback voltage can be changed easily.

The inverter circuit B includes a capacitor C_FourBoth
Switching element Q connected in parallel at one end₂, Q₃Directly
Half bridge circuit consisting of column circuits and switching element
Child Q ₂, Q₃Switchon connected to each base of
Element Q₂, Q₃Driver circuit H₁, H₂Tokara
It Driver circuit H₁, H₂Signal from the control circuit X
Sent. The output of the inverter circuit B is an inductor
L₂, Capacitor C₆, C₇And a load circuit Z composed of
The discharge lamp La is connected. Inductor L₂Is a switch
Holding element Q₂Connected between the emitter of and the circuit ground
The switching element Q₃Of the emitter and discharge lamp La
Cut the DC component between the other end of the power supply side terminal.
Capacitor C₆Is connected, and the discharge lamp La is electrically
Preheating capacitor C between source terminals₇Is connected,
Switching element Q₂, Q₃By turning on and off alternately
The applied high-frequency voltage is supplied to the discharge lamp La via the load circuit Z.
Applied to.

Next, the operation will be briefly described with reference to FIG. By gradually increasing the switching frequency of the switching element Q ₃ as shown in FIG.
As shown in (d), the lamp current I _la of the discharge lamp La is reduced and the discharge lamp La is turned off at time t ₀ . At that time, the switching element Q ₄₁ is turned off, the feedback voltage to the control IC (G) is changed, and as shown in FIG. 4 (b),
The output voltage V _DC of the AC-DC converter A is reduced.

With this operation, when the discharge lamp La is turned off, a sufficient preheating current _If can be supplied to the filament of the discharge lamp La and the output voltage V _DC of the AC-DC converter A can be lowered. Therefore, the discharge lamp L after the discharge lamp La is turned off
It is possible to prevent light emission at the tube end of a.

In this circuit, the step-up chopper circuit is used for the AC-DC converter A, but any circuit that can control the output voltage such as a step-down chopper circuit or a step-up / step-down chopper circuit can be used. Well, for controlling the switching element Q ₁ of the boost chopper circuit, a motorola IC (MC
34261) was used, other control methods may be used, and the method of supplying the electric power to the discharge lamp La is the Harf Bridge method, but any method can be used as long as the electric power to the discharge lamp La can be controlled. However, the preheating method of the filament of the discharge lamp La was performed by the current flowing through the capacitor C ₇ ,
As long as the preheating current _If is supplied from the AC / DC converter A via the inverter circuit B, any kind of device may be used.

(Embodiment 2) FIG. 5 shows a second embodiment according to the present invention.
FIG. 4 is a circuit diagram showing an example, which is different from the first embodiment shown in FIG. 3.
The point is the space between pin 7 of the control IC (G) and the circuit ground.
Itching element Q ₄₂Is provided, and the other is the first
Since it is similar to the embodiment, the same reference numerals are given to the same configurations.
The description will be omitted.

In this circuit, in order to turn off the discharge lamp La,
By turning on the switching element Q ₄₂ , the gate and the ground of the switching element Q ₁ are short-circuited, and by turning off the switching element Q ₁ , the operation of the step-up chopper circuit is stopped, and the AC-DC converter A Output voltage V
Lower _DC . At this time, the preheating current _If is continuously supplied to the filament of the discharge lamp La. Therefore, similarly to the first embodiment, it is possible to prevent light emission from the tube end of the discharge lamp La after being turned off.

In this circuit, the step-up chopper circuit is used for the AC-DC converter A, but any circuit that can control the output voltage, such as a step-down chopper circuit or a step-up / step-down chopper circuit, can be used. Well, for controlling the switching element Q ₁ of the boost chopper circuit, a motorola IC (MC
34261) was used, other control methods may be used, and the method of supplying the electric power to the discharge lamp La is the Harf Bridge method, but any method can be used as long as the electric power to the discharge lamp La can be controlled. However, the preheating method of the filament of the discharge lamp La was performed by the current flowing through the capacitor C ₇ ,
Any means may be used as long as it supplies the preheating current _If from the AC-DC converter A via the inverter circuit B, and the means for stopping the operation of the boost chopper circuit is not limited to the above. For example, a direct current component may be biased between the inductor L ₁ and the fifth pin of the control IC (G).

(Embodiment 3) FIG. 6 is a circuit diagram showing a third embodiment of the present invention. The difference from the first embodiment shown in FIG. 3 is that the circuit of the AC-DC converter A is doubled. A rectifier circuit that can switch between a voltage rectifier circuit and a full-wave rectifier circuit is used, and the inverter circuit B is a switching element Q.
By feeding back the currents flowing in the secondary windings n ₁₁ and n ₁₂ of the current transformer CT ₁ provided between the emitter of ₂ and the discharge lamp La to the bases of the switching elements Q ₂ and Q ₃ ,
This is because the self-exciting method for driving the switching elements Q ₂ and Q ₃ is used, and the other structure is the same as that of the first embodiment. Therefore, the description is omitted by giving the same reference numerals to the same structures.

The above rectifier circuit includes diodes D _{1 to} D ₄
The diode bridge circuit constituted by the above is connected to both ends of the AC power supply V _ac via the ground circuit Y and the filter circuit F, and capacitors C ₈ and C are provided at both ends of the series circuit of the diodes D ₃ and D _4. Connect a series circuit of ₉ and connect capacitors C ₈ and C
Switching for switching between conduction between the connection point of ₉ and one end of the AC power supply V _ac and conduction between the connection point of the diodes D ₃ and D ₄ and one end of the AC power supply V _ac Element Q ₅
Is provided.

The operation inside the control circuit X is such that the dimming signal S ₁ is amplified by the amplifier OP ₁ and the output thereof is output from the comparator CON.
₂ compares the external voltage V _CC with ON / OFF of the switching element Q ₆ by the output of the comparator CON ₂ . By switching element Q ₆ is turned on, the switching element Q ₃ is turned off, inverter - the operation of the capacitor circuit B stops. Further, the switching element Q ₅ is switched by comparing and outputting the dimming signal S ₁ by the comparator CON ₁ .

When the discharge lamp La is lit, the capacitor C ₈ ,
By switching the switching element Q _{5 so} as to establish conduction between the connection point of C ₉ and one end of the AC power source V _ac , the above rectifier circuit is used as a voltage doubler rectifier circuit, and when the discharge lamp La is turned off. is diode - by switching the switching element Q ₅ so as to conduct between the connection point of the de D _3, D ₄ and one end of the AC power source V _ac, the rectifier circuit is used as a full-wave rectifier circuit.

[0035] By operating as described above, always provide sufficient preheating current I _f to the filament of the discharge lamp La, and as compared with the time of the discharge lamp La lit, unlit AC - output voltage of the DC converter unit A V _DC can be cut in half, so
It is possible to prevent light emission from the tube end of the discharge lamp La after being turned off.

In this embodiment, the AC / DC converter A is used.
Although the rectifier circuit capable of switching between the voltage doubler rectifier circuit and the full-wave rectifier circuit is used, the AC-DC converter A may be any circuit as long as it can control the output voltage. Although the circuit as described above is used to control the circuit and the switching element of the inverter circuit B, other control methods may be used, and the power supply method to the discharge lamp La is the half-bridge method. Any method can be used as long as it can control the power to the electric lamp La, and the filament of the discharge lamp La was preheated by the current flowing through the capacitor C _7. Any source may be used as long as it supplies the preheating current _If from the DC converter A.

(Fourth Embodiment) FIG. 7 is a block diagram showing a fourth embodiment according to the present invention. The difference from the first embodiment shown in FIG. 1 is that switching elements Q are provided at both ends of the discharge lamp La.
₇ is provided and the other structure is the same as that of the first embodiment, and therefore the description thereof will be omitted by giving the same reference numerals to the same structures.

In this embodiment, both ends of the discharge lamp La are
Switch element Q₇By short-circuiting at_f
Eliminate the potential difference between both ends of the discharge lamp La when supplying
Then, the discharge lamp La is turned off. Therefore, the preheating current I_fIs
Tube wall of discharge lamp La, stray capacitance C _XCircuit Grand without going through
Flow into the discharge lamp, and the high-frequency voltage is applied to the discharge lamp La
Since it does not occur between the
The potential between the tube wall of La and the filament of the discharge lamp La is
Does not occur. Therefore, if operated in this way, the discharge lamp La
After surely turning off the light, prepare for the next restart and then preheat current I_f
Can be supplied and can prevent light emission from the tube end of the discharge lamp La.
it can.

FIG. 8 is a circuit diagram showing a specific example of the present embodiment. The difference from the circuit shown in FIG. 3 is that the discharge lamp L is as described above.
Since the switch element Q ₇ is provided at both ends of a and other configurations are the same as those in the first embodiment, the description thereof will be omitted by giving the same reference numerals to the same configurations.

(Fifth Embodiment) FIG. 9 is a block diagram showing a fifth embodiment according to the present invention. The difference from the first embodiment shown in FIG. 1 lies in that an inverter circuit B and a load circuit Z are provided. A switching element Q ₈ is provided in the AC-DC converter A
Therefore, the preheating current supply means W for supplying the preheating current _If to the filament of the discharge lamp La without passing through the inverter circuit B
Since the other configurations are similar to those of the first embodiment, the description thereof will be omitted by giving the same reference numerals to the same configurations.

Next, the operation will be briefly described. This circuit is
The switching element Q ₈ is turned off by the dimming signal S ₁ ,
By shutting off the power supply from the inverter circuit B to the discharge lamp La and making the lamp current I _la zero, the discharge lamp La is discharged.
Turn off. Further, regardless of the extinction of the discharge lamp La, the AC through the preheating current supplying means W - supplying a preheating current I _f to the filament of the DC converter unit A from the discharge lamp La. Therefore, with such an operation, after the discharge lamp La is reliably turned off, the preheating current _If can be supplied in preparation for the next restart, and light emission from the tube end of the discharge lamp La can be prevented.

FIG. 10 is a circuit diagram showing a specific example of this embodiment. The difference from the circuit diagram shown in FIG. 3 is that a capacitor is provided via a resistor R ₆ which is the preheating current supply means W in FIG. The high voltage side of C ₄ is connected to the power supply terminal side of one filament of the discharge lamp La, and the resistor R ₁₆ is connected between the power supply terminal side of the other filament of the discharge lamp La and the circuit ground. A resistor R is connected in parallel with the capacitor C ₇ between the power supply terminals.
₁₅ is connected, and the switching elements Q ₉ and Q ₁₀ are provided between the bases and the emitters of the switching elements Q ₂ and Q ₃ , respectively, and other configurations are similar to those of the first embodiment. Description is omitted by attaching the same reference numerals to the same components.

Next, the operation will be briefly described. Is in the present embodiment, the dimming signals S ₁ by the switching element Q _9,
Turn on Q ₁₀ , turn on the bases of switching elements Q ₂ and Q ₃ ,
By short-circuiting the emitters, the operation of the inverter circuit B is stopped and the discharge lamp La is turned off. After that, by the output of the AC-DC converter A, the preheating current I _{f is} applied to both filaments of the discharge lamp La through the resistors R ₆ , R ₁₅ , and R _16.
Prepares for restart. At this time, the resistors R ₆ , R ₁₅ , R
_{16. Since} the output voltage V _DC of the AC-DC converter A can be divided by the series circuit of filaments, the high-potential side of the discharge lamp La can be set low, and therefore the filament of the discharge lamp La and the instrument ground. The potential difference between them can be reduced.

Therefore, if it operates in this way, the discharge lamp La
After surely extinguishing, turn off the preheating current I _f in preparation for the next restart.
Can be supplied, and light emission at the tube end of the discharge lamp La can be prevented.

In this embodiment, the AC / DC converter A
Was used boost chopper circuit, as long as a circuit capable of controlling the output voltage as the step-down chopper circuit and step-up and step-down chopper circuit may be of any type, the control of the switching elements to Q ₁ step-up chopper circuit Motoro -IC manufactured by LA (M
C34261) is used, other control methods may be used, and the method of supplying electric power to the discharge lamp La is the Harf Bridge method, but any method can be used as long as the electric power to the discharge lamp La can be controlled. Alternatively, the preheating current supply means W does not have to be the method of passing the resistance R ₆ from the output of the AC-DC conversion unit A as described above, but the preheating current _{If is} supplied between the discharge lamp La and the appliance ground. Any component may be used as long as it lowers the potential difference of No. 2, and the preheating current _If may be supplied from the AC power supply V _ac .

(Sixth Embodiment) FIG. 11 is a block diagram showing the sixth embodiment of the present invention. The difference from the first embodiment shown in FIG. 1 lies in that a load circuit Z and a discharge lamp La are provided. Since the insulating transformer T ₁ is provided and the other structure is the same as that of the first embodiment, the description thereof will be omitted by giving the same numeral to the same structure.

In this embodiment, since the insulating transformer T ₁ is provided, the ground circuit Y → the filter circuit A → the inverter circuit B → the load circuit → the discharge lamp La as shown in the conventional example. → tube wall of discharge lamp La → stray capacitance C _X → ground circuit Y
Since there is no such closed loop, it is possible to prevent light emission at the tube end of the discharge lamp La. Further, the discharge lamp La is turned off,
In addition, the inverter circuit B is provided to the extent that a sufficient preheating current _If is supplied to the filament of the discharge lamp La in preparation for restarting.
Reduce the output of.

In this way, after the discharge lamp La is reliably turned off, the preheating current _If can be supplied in preparation for the next restart,
Moreover, it is possible to prevent light emission from the tube end of the discharge lamp La.

FIG. 12 is a circuit diagram showing a specific example of this embodiment, and is different from the first embodiment shown in FIG. 3 between the load circuit composed of the inductor L ₂ and the capacitor C ₆ and the discharge lamp La. Since the insulating transformer T ₁ is provided in the first embodiment and the other structure is the same as that of the first embodiment, the description thereof will be omitted by giving the same numeral to the same structure.

In this embodiment, the AC / DC converter A
Was used boost chopper circuit, as long as a circuit capable of controlling the output voltage as the step-down chopper circuit and step-up and step-down chopper circuit may be of any type, the control of the switching elements to Q ₁ step-up chopper circuit Motoro -IC manufactured by LA (M
C34261) is used, other control methods may be used, and the method of supplying electric power to the discharge lamp La is the Harf Bridge method, but any method can be used as long as the electric power to the discharge lamp La can be controlled. However, the preheating method of the filament of the discharge lamp La was performed by the current flowing through the capacitor C ₇ ,
As long as the preheating current _If is supplied from the AC / DC converter A via the inverter circuit B, any kind of device may be used.

(Embodiment 7) FIG. 13 is a circuit diagram showing a seventh embodiment of the present invention, which is different from the circuit of the sixth embodiment shown in FIG. - the output of the DC converter unit B is connected to the primary winding of the isolation transformer T _2, to connect the two secondary windings of the isolation transformer T ₂ across the filaments of each discharge lamp La, in the circuit of FIG. 10 the switching element Q ₂ in the same manner as shown, Q ₃ of the base - scan is providing the switching element Q _4, Q ₅ between the emitters. The other structure is similar to that of the sixth embodiment, and therefore, the same structures are designated by the same reference numerals and the description thereof is omitted.

The operation will be briefly described below. This circuit, by turning on the switching element Q _4, Q _5, base of the switching element Q _2, Q ₃ - scan, short emitter, respectively, inverters - to stop the operation of the capacitor circuit B, the discharge lamp L
Turn off a. The preheating current _If is supplied from the output of the AC / DC converter A to the filaments at both ends of the discharge lamp La through the preheating current supply means W and the insulating transformer T ₂ .

By operating in this way, the discharge lamp La
After surely extinguishing, turn off the preheating current I _f in preparation for the next restart.
Can be supplied, and light emission at the tube end of the discharge lamp La can be prevented.

In this embodiment, the step-up chopper circuit is used in the AC-DC converter A, but any circuit can be used as long as it can control the output voltage, such as a step-down chopper circuit or a step-up / step-down chopper circuit. However, for controlling the switching element of the boost chopper circuit, an IC manufactured by Motorola (MC34
261) was used, but other control methods may be used, and the discharge lamp La
The method of supplying electric power to the discharge lamp La is a harbfridge method, but any method can be used as long as the electric power to the discharge lamp La can be controlled, and the preheating current _If of the filament of the discharge lamp La is AC- Although it is supplied from the output of the DC converter A, it may be supplied from the AC power supply V _ac .

[0055]

As described above, according to the present invention, after the discharge lamp is surely turned off, a sufficient preheating current is supplied for filament preheating of the discharge lamp in preparation for the next restart, while the discharge lamp is being supplied. It is possible to provide a discharge lamp lighting device capable of preventing the emission of light from the tube end.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment according to the present invention.

FIG. 2 is an operation waveform diagram of each part of the first embodiment.

FIG. 3 is a circuit diagram showing a specific example of the first embodiment.

FIG. 4 is an operation waveform diagram of each unit of the above specific example.

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

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

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

FIG. 8 is a circuit diagram showing a specific example of the fourth embodiment.

FIG. 9 is a block diagram showing a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a specific example of the fifth embodiment.

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

FIG. 12 is a circuit diagram showing a specific example of the sixth embodiment.

FIG. 13 is a circuit diagram showing a specific example of the seventh embodiment of the present invention.

FIG. 14 is a block diagram showing a conventional example of the present invention.

FIG. 15 is an operation waveform diagram of each part of the above-mentioned conventional example.

FIG. 16 is a schematic diagram showing a partial structure of the conventional example.

FIG. 17 is another block diagram showing a conventional example of the present invention.

[Explanation of symbols]

A AC-DC converter B Inverter circuit C _X Stray capacitance La Discharge lamp S ₁ Dimming signal T Insulation transformer X Control circuit Y Earth circuit Z Load circuit

Claims (4)

[Claims] 1. An earth circuit connected to both ends of an alternating current power supply, an alternating current-direct current conversion circuit connected to both ends of an alternating current power supply through the earth circuit, and an output of the alternating current to direct current conversion circuit. An inverter circuit for converting electric power into high frequency power, a parallel circuit of a load circuit and a discharge lamp connected to the output end of the inverter circuit, a control circuit for controlling the inverter circuit, and the discharge circuit. A discharge lamp lighting device having a preheating power supply means for supplying preheating power to a filament of an electric lamp, and a stray capacitance exists between the tube wall of the discharge lamp and the ground circuit; Power supplied to the discharge lamp from the inverter circuit and the preheating power supply means so that it can be controlled to a level at which the discharge lamp is substantially turned off, the inverter circuit and the AC-DC conversion circuit, And the impedance of the load circuit A discharge lamp lighting device comprising controllable means. 2. The means capable of controlling the electric power supplied from the inverter circuit to the discharge lamp to a level at which the discharge lamp is substantially turned off is a means for short-circuiting both ends of the discharge lamp. The discharge lamp lighting device according to claim 1. 3. The means for controlling the electric power supplied from the inverter circuit and the preheating power supply means to the discharge lamp to a level at which the discharge lamp is substantially turned off is a voltage across the discharge lamp. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a unit that lowers 4. The means for supplying power to the discharge lamp from the inverter circuit and the preheating power supply means is means for insulating the preheating power supply means from the filament of the discharge lamp, or the invertor. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is at least one of a means for insulating a discharge circuit and the discharge lamp.