JP3304596B2 - Discharge lamp lighting device - Google Patents

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 for securing safety and reducing noise is connected to both ends of an AC power supply _Vac .
A filter circuit F for noise reduction or the like is connected to an output terminal of the earth circuit Y, an AC-DC converter A is connected to an output terminal of the filter circuit F, and an output terminal of the AC-DC converter A An inverter circuit B for outputting high-frequency power is connected to the inverter circuit B.
A parallel circuit of the load circuit Z and the discharge lamp La is connected to the output terminal of the data 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. Furthermore, inverter - the drive of the motor circuit B inside the Suitchiggu element performed by the control circuit X, the change in the control circuit X of the signal is performed by receiving a dimming signal S _1.

Next, the operation will be briefly described with reference to FIG. First, Figure 15 dimming signals S ₁ shown in (a) is increased,
When the predetermined level is reached at the time t ₀ , the preheating current _If of the filament of the discharge lamp La shown in FIG. 15C is reduced, so that the lamp current I of the discharge lamp La is reduced as shown in FIG. _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 And the drive of the control circuit X, the inverter circuit B
Supplies electric power to the extent that the discharge lamp La is not turned on to the discharge lamp La and the filament of the discharge lamp La. And time t
_In order to prepare for the next restart after ₁ , as shown in FIG. 15C, a preheating current _If having a value slightly larger than that between times t _{0 and} t ₁ is supplied.

[0005] With this operation, even after the discharge lamp La is reliably turned off, a sufficient preheating current _If is prepared for the next restart.
Can be supplied.

[0006]

When the above-described discharge lamp lighting device is configured as a lighting fixture, the output light of the discharge lamp La provided on a partial surface of the fixture K is used as shown in FIG. In the case where there is a reflecting plate J that reflects and has conductivity, and the reflecting plate J is at the same potential as the appliance ground and the reflecting plate J is close to the discharge lamp La, as shown in FIG. K, in particular, a stray capacitance _CX exists between the reflector J and the tube wall of the discharge lamp La. That is, there is a stray capacitance _CX between the appliance earth and the tube wall of the discharge lamp La.

In this case, in this apparatus, as shown in the block diagram of FIG. 17, the earth circuit Y → the filter circuit F → the AC / DC converter A → the inverter circuit B → the load circuit Z → the discharge lamp. There is an electrically closed loop of La → the tube wall of the discharge lamp La → the stray capacitance C _X → the 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. A problem arises, and for example, when the discharge lamp lighting device shown in the above-mentioned conventional example is used for production, there arises a problem that 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 at 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, and the next restart cannot be instantaneously performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to ensure that the discharge lamp is turned off, and that sufficient preheating is performed for filament preheating of the discharge lamp in preparation for the next restart. An object of the present invention is to provide a discharge lamp lighting device capable of preventing light emission at a tube end of a discharge lamp while supplying current.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises an earth circuit connected to both ends of an AC power supply, and an AC power supply connected to the AC power supply via the earth circuit. AC-connected to both ends and including a circuit that controls output power
A DC conversion circuit, an inverter circuit for converting the output power of the AC-DC conversion circuit to high-frequency power, and the inverter
A parallel circuit of a load circuit and a discharge lamp connected to an output terminal of the inverter circuit, a control circuit for controlling the inverter circuit, and a preheating power supply means for supplying preheating power to a filament of the discharge lamp. In a discharge lamp lighting device in which a stray capacitance exists between a tube wall of the discharge lamp and the earth circuit,
The inverter - the power supplied from the capacitor circuit and the preheating electric power supply means to the discharge lamp, as controllable to a level to turn off substantially the discharge lamp, A - scan circuit, output current
AC-DC conversion circuit including a circuit for controlling force,
-Discharge circuit, load circuit, discharge lamp, discharge lamp tube wall, stray capacitance
Of an electrically closed loop consisting of a ground and an earth circuit
By providing a means for controlling the
It is characterized by controlling the current flowing through the loop .

According to a second aspect of the present invention, the means for controlling the electric power supplied from the inverter circuit to the discharge lamp to a level at which the discharge lamp is turned off substantially includes 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 for controlling the power supplied to the discharge lamp from the inverter circuit and the preheating power supply means to a level at which the discharge lamp is substantially turned off is provided at both ends of the discharge lamp. It is characterized by a means for lowering the voltage.

According to a fourth aspect of the present invention, the means for supplying power to the discharge lamp from the inverter circuit and the preheating power supply means includes means for insulating the preheating power supply means from the filament of the discharge lamp, or an inverter. And at least one of means for insulating the discharge lamp and the discharge lamp.

[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
AC including an earth circuit and a circuit for controlling output power so that control can be performed to a level at which the discharge lamp is turned off substantially.
-DC conversion circuits, inverter circuits, load circuits, discharge lamps,
Electrical system consisting of discharge lamp tube wall, stray capacitance and earth circuit
Provide means capable of controlling the impedance of the closed loop.
Thus, the current flowing through the electric closed loop can be controlled , the output of the inverter circuit can be reduced to turn off the discharge lamp, and at the same time, a sufficient preheating current can be supplied to preheat the filament of the discharge lamp. .

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

According to the third aspect of the present invention, the means for controlling the power supplied to the discharge lamp from the inverter circuit and the preheating power supply means to a level at which the discharge lamp is turned off substantially is a discharge lamp. Means for lowering the voltage between both ends can 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 present invention, the means for supplying power to the discharge lamp from the inverter circuit and the preheating power supply means includes means for insulating the preheating power supply means from the filament of the discharge lamp, or By being at least one of the means for insulating the inverter circuit and the discharge lamp,
Current can be prevented 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 the voltage across the discharge lamp must be reduced in order to turn off the discharge lamp. And at the same time provide 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. The difference from the conventional example shown in FIG.
In addition to performing the output control of the inverter circuit B so that the discharge lamp La is turned off, the output control of the AC-DC converter A is performed.
Alternatively, the value of the impedance of the load circuit Z is controlled, and the other configuration is the same as that of the conventional example.
The description of the same components will be omitted by retaining the same reference numerals.

Next, referring to FIG. 2, the operation of this circuit will be briefly described.
explain. First, as shown in FIG.₁
Rises at time t₀Fig. 2
As shown in (c), the preheating power of the filament of the discharge lamp La
Style I _fBy squeezing the lamp, as shown in FIG.
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
Is reduced by the earth circuit Y → fill shown in the conventional example.
Inverter circuit F → AC-DC converter A → Inverter circuit B → Negative
Load circuit Z → discharge lamp La → tube wall of discharge lamp La → stray capacitance C
_X→ The current flowing through the electrically closed loop called the earth circuit Y
So that a small discharge at the tube end of the discharge lamp La does not occur.
Do it up to the degree.

Even after time t ₁ , the inverter circuit B supplies electric power to the extent that the discharge lamp La is not lit, and supplies the preheating current _If 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 light emission at the tube end of the discharge lamp La can be prevented. FIG. 3 shows a specific circuit diagram of this embodiment, which will be briefly described below.

The filter circuit F in the diagram shown in FIG.
Consists of an inductor L _F connected on the power supply line, a capacitor C _F connected to both ends of the AC power supply V _ac through the inductor L _F. The AC-DC converter A includes a rectifier DB that rectifies the AC power supply _Vac via the filter circuit F,
To boost the rectified voltage, consisting a boost chopper circuit for smoothing, a control IC for controlling the switching element to Q ₁ boost chopper circuit (G). 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. Voltage which is smoothed by the capacitor C ₄ connected in parallel to the output terminal of the step-up chopper circuit is inverted - is input to the capacitor circuit B.

On / off control I of the switching element Q ₁
C (G) is, for example, an IC (MC3426) manufactured by Motorola.
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 third pin of the control IC (G), or to the fifth pin. inputting a current flowing through the secondary winding of the inductor L _1, and inputs a current flowing through the switching element Q ₁ to 4 pin, AC pin 1 - the output voltage V _DC of the DC converter unit a Fi - to Dobakku It is done by doing. here,
Resistors R ₄ , R ₅ , R ₅ connected across capacitor C ₄
By short-circuiting both ends of the resistor R ₆ in the switching element Q ₄₁ of the series circuit of _6, Fi to the control IC (G) -
The feedback voltage can be easily changed.

The inverter circuit B includes a capacitor C_FourBoth
The switching element Q connected in parallel to the ends_Two, Q_ThreeDirectly
A half bridge circuit composed of a column circuit and a switching element
Child Q _Two, Q_ThreeConnected to each of the bases
Element Q_Two, Q_ThreeDriver circuit H₁, H_TwoAnd from
You. Driver circuit H₁, H_TwoSignal from the control circuit X
Sent. The output of the inverter circuit B has an inductor
L_Two, Capacitor C₆, C₇And a load circuit Z composed of
The discharge lamp La is connected. Inductor L_TwoIs a switch
Ching element Q_TwoConnected between the emitter and circuit ground
And the switching element Q_ThreeEmitter and discharge lamp La
Cut the DC component between the other end of the power supply terminal.
Capacitor C₆Is connected, and the discharge lamp La
Preheat capacitor C between source terminals₇Is connected,
Switching element Q_Two, Q_ThreeOutput by alternate on / off of
The applied high-frequency voltage is supplied to the discharge lamp La via the load circuit Z.
Is applied to

Next, the operation will be briefly described with reference to FIG. As shown in FIG. 4 (e), by gradually increasing the switching frequency of the switching element Q _3, FIG. 4
As (d), the reducing the lamp current I _la of the discharge lamp La, the discharge lamp La is turned off at time t _0. At that time, turns off the switching element Q _41, Fi to the control IC (G) - by changing to feedback voltage, as shown in FIG. 4 (b),
The output voltage _VDC of the AC-DC converter A is reduced.

With this operation, when the discharge lamp La is turned off, a sufficient preheating current _If is supplied to the filament of the discharge lamp La, and the output voltage _VDC of the AC-DC converter A can be reduced. Therefore, the discharge lamp L after the discharge lamp La is turned off
Light emission at the end of the tube a can be prevented.

In this circuit, a step-up chopper circuit is used for the AC-DC converter A. However, any circuit capable of controlling the output voltage such as a step-down chopper circuit or a step-up / step-down chopper circuit can be used. well, the control of the switching elements to Q ₁ boost chopper circuit Motoro - La Corp. IC (MC
34261) was used, but other control methods may be used. The method of supplying power to the discharge lamp La uses the half bridge method, but any method that can control the power to the discharge lamp La is used. but often, although preheating process of the filaments of the discharge lamp La was performed by a current flowing through the capacitor C _7,
Any device may be used as long as it supplies the preheating current _If from the AC-DC converter A via the inverter circuit B.

(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.
The point is a gap between pin 7 of the control IC (G) and circuit ground.
Switching element Q ₄₂The other is the first
Since the configuration is the same as that of the embodiment, the same components are denoted by the same reference numerals.
Thus, the description is omitted.

In this circuit, in order to turn off the discharge lamp La,
By turning on the switching elements Q _42, the gate switching element Q ₁ - DOO causes short-circuit the ground by turning off the switching element Q _1, it stops the operation of the boost chopper circuit, the AC - DC converter unit A Output voltage V
Lower _DC . At this time, the preheating current _If continues to be supplied to the filament of the discharge lamp La. Therefore, similarly to the first embodiment, light emission at the tube end of the discharge lamp La after extinguishing can be prevented.

In this circuit, a step-up chopper circuit is used for the AC-DC converter A. However, any circuit capable of controlling the output voltage such as a step-down chopper circuit or a step-up / step-down chopper circuit can be used. well, the control of the switching elements to Q ₁ boost chopper circuit Motoro - La Corp. IC (MC
34261) was used, but other control methods may be used. The method of supplying power to the discharge lamp La uses the half bridge method, but any method that can control the power to the discharge lamp La is used. but often, although preheating process of the filaments of the discharge lamp La was performed by a 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, it is a method of biasing the DC component between the fifth pin of the inductor L ₁ and the control IC (G).

(Embodiment 3) FIG. 6 is a circuit diagram showing a third embodiment according to 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 capable of switching between a voltage rectifier circuit and a full-wave rectifier circuit is used, and the inverter circuit B includes a switching element Q
By returning to the scan, - the current flowing through the secondary winding n _11, n ₁₂ of the current provided transformer CT ₁ between the _second emitter and the discharge lamp La in the base switching element Q _2, Q ₃
The self-excited type driving the switching elements Q ₂ and Q ₃ is used, and the other configuration is the same as that of the first embodiment.

The rectifier circuit includes diodes D _{1 to} D ₄
Is connected to both ends of an AC power supply _Vac via an earth circuit Y and a filter circuit F, and capacitors C ₈ and C are connected to both ends of a series circuit of diodes D ₃ and D _{4. 9} series circuits, and capacitors C ₈ and C
Switching for switching between conduction between the connection point ₉ and one end of the AC power supply _Vac and conduction between the connection point of the diodes D ₃ and D ₄ and one end of the AC power supply _Vac. Element Q ₅
Is provided.

The internal operation of the control circuit X is such that the dimming signal S ₁ is amplified by the amplifier OP ₁ and the output thereof is compared with the output of the comparator CON.
₂ as compared to the external voltage V _CC, the controls on and 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. Furthermore, comparing the dimming signals S ₁ by the comparator CON _1, by outputting, to switch the switching element Q _5.

When the discharge lamp La is lit, the condenser C ₈ ,
By switching the switching element Q ₅ so as to conduct between the one end of the connecting point between the AC power source V _ac of C _9, the rectifier circuit is used as a voltage doubler rectifier circuit, also when turning off the discharge lamp La 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 _VDC can be reduced by half, so
Light emission from the tube end of the discharge lamp La after the light is turned off can be prevented.

In this embodiment, the AC-DC converter A
Although a rectifier circuit that can switch between a voltage doubler rectifier circuit and a 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 above-described circuit was used for controlling the switching elements of the circuit and the inverter circuit B, other control methods may be used, and the half bridge method was used for supplying power to the discharge lamp La. if a system which can control the power to the lamp La, may be of any type, although preheating process of the filaments of the discharge lamp La was performed by a current flowing through the capacitor C _7, inverter - the AC through the capacitor circuit B - Any device may be used as long as it supplies the preheating current _If from the DC converter A.

(Embodiment 4) 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 and the other configuration is the same as that of the first embodiment. Therefore, the description of the same configuration will be omitted by retaining the same reference numeral.

In this embodiment, both ends of the discharge lamp La are
Switch element Q₇The short circuit at the preheating current I_f
Eliminates 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
Discharge lamp La tube wall, stray capacitance C _XWithout the circuit gran
High-frequency voltage is applied to the filament of the discharge lamp La.
Discharge lamp, 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, by operating in this manner, the discharge lamp La
Is turned off, and the preheating current I_f
And discharge of light from the tube end of the discharge lamp La can be prevented.
it can.

FIG. 8 is a circuit diagram showing a specific example of this embodiment. The difference from the circuit shown in FIG.
a is at both ends by providing the switching element Q ₇ to the, since other configurations are the same as the first embodiment, a description thereof will be omitted by giving the same reference numerals to the same configuration.

(Embodiment 5) FIG. 9 is a block diagram showing a fifth embodiment according to the present invention. The difference from the first embodiment shown in FIG. the switching element Q ₈ provided, also alternating current - direct current conversion unit a
Thus, 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 other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted.

Next, the operation will be briefly described. This circuit is
Off the switching element Q ₈ by the dimming signal S _1,
By interrupting the power supply from the inverter circuit B to the discharge lamp La and setting the lamp current _Ila to zero, the discharge lamp La
Turn off the light. 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 the light emission at the tube end of the discharge lamp La can be prevented.

[0042] Figure 10 is a circuit diagram showing a specific example of this embodiment, differs from the circuit diagram shown in FIG. 3, via a resistor R ₆ is in the preheating current supplying means W in FIG. 9, the capacitor The high-voltage side of C ₄ is connected to the power terminal side of one filament of the discharge lamp La, the resistor R ₁₆ is connected between the power terminal side of the other filament of the discharge lamp La and the circuit ground, in parallel with the capacitor C ₇ between the power supply terminal resistor R
₁₅ and the switching elements Q ₉ and Q ₁₀ are provided between the base and the emitter of each of the switching elements Q ₂ and Q _3. Other configurations are the same as those of the first embodiment. The description of the same components will be omitted by retaining the same reference numerals.

Next, the operation will be briefly described. Is in the present embodiment, the dimming signals S ₁ by the switching element Q _9,
The Q ₁₀ is turned on, the switching element Q _2, Q ₃ base - scan,
By short-circuiting the emitters, the operation of the inverter circuit B is stopped, and the discharge lamp La is turned off. Thereafter, the AC - the output of the DC converter unit A, resistor R _6, R _15, preheated through R ₁₆ to both filaments of the discharge lamp La current I _f
Flows to prepare for restart. At this time, the resistors R ₆ , R ₁₅ , R
_{16. Since} the output voltage _VDC of the AC-DC converter A can be divided by the series circuit of the filament, the potential on the high voltage side of the discharge lamp La can be set low. The potential difference between them can be reduced.

Therefore, if this operation is performed, the discharge lamp La
Is turned off, and the preheating current I _f is prepared for the next restart.
And discharge of light from 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 -La's IC (M
C34261) was used, but other control methods may be used. The method of supplying power to the discharge lamp La uses the half bridge method, but any method that can control the power to the discharge lamp La is used. but often, the preheating current supplying means W are such as described above, the AC - without a method via a resistor R ₆ from the output of the DC converter unit a, when the preheating current I _f supply, the discharge lamp La and the instrument a - rce The preheating current _If may be supplied from the AC power supply _Vac as long as the preheating current If is reduced as long as it reduces the potential difference.

(Embodiment 6) FIG. 11 is a block diagram showing a sixth embodiment of the present invention. The difference from the first embodiment shown in FIG. insulation and in that provided transformer T _1, since the other configurations are the same as in the first embodiment, a description thereof will be omitted by giving the same reference numerals to the same configuration.

[0047] This embodiment, by providing the insulating transformer T _1, the like shown in the conventional example, A - scan circuit Y → filter - circuit A → inverter - capacitor circuit B → load circuit → discharge lamp La → tube wall of discharge lamp La → stray capacitance C _X → earth circuit Y
Since the closed loop does not exist, it is possible to prevent light emission from the tube end of the discharge lamp La. Also, the discharge lamp La is turned off,
And until the sufficient preheating current _If is supplied to the filament of the discharge lamp La in preparation for restart, the inverter circuit B
Lower the output.

In this manner, after the discharge lamp La is reliably turned off, the preheating current _If can be supplied in preparation for the next restart.
In addition, light emission at the tube end of the discharge lamp La can be prevented.

[0049] Figure 12 is a circuit diagram showing a specific example of this embodiment, the first embodiment differs from the embodiment shown in Figure 3, between the load circuit including the inductor L ₂ and capacitor C ₆ and the discharge lamp La in and by providing the insulating transformer T _1, since the other configurations are the same as in the first embodiment, a description thereof will be omitted by giving the same reference numerals to the same configuration.

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 -La's IC (M
C34261) was used, but other control methods may be used. The method of supplying power to the discharge lamp La uses the half bridge method, but any method that can control the power to the discharge lamp La is used. but often, although preheating process of the filaments of the discharge lamp La was performed by a current flowing through the capacitor C _7,
Any device may be used as long as it supplies the preheating current _If from the AC-DC converter A via the inverter circuit B.

(Embodiment 7) FIG. 13 is a circuit diagram showing a seventh embodiment of the present invention. The difference 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 Switching elements Q ₄ and Q ₅ are provided between the bases and emitters of switching elements Q ₂ and Q _{3 in} the same manner as shown. The other configuration is the same as that of the sixth embodiment, and the description thereof will be omitted by retaining the same reference numerals.

The operation will be briefly described below. In this circuit, when the switching elements Q ₄ and Q ₅ are turned on, the bases and the emitters of the switching elements Q ₂ and Q ₃ are short-circuited, respectively, and the operation of the inverter circuit B is stopped.
Turn off a. The preheating current I _f AC - from the output of the DC converter unit A, the preheating current supplying means W, is supplied to both ends of the filament of the discharge lamp La via the isolation transformer T _2.

By operating in this manner, the discharge lamp La
Is turned off, and the preheating current I _f is prepared for the next restart.
And discharge of light from the tube end of the discharge lamp La can be prevented.

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

[0055]

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

[Brief description of the 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 section 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 section of the 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 a 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 section of the 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

────────────────────────────────────────────────── (5) References JP-A-5-326174 (JP, A) JP-A-3-112093 (JP, A) JP-A-55-19725 (JP, A) (58) Search Field (Int.Cl. ⁷ , DB name) H05B 41/282 H05B 41/24

Claims (4)

(57) [Claims] An AC-DC converter circuit connected to both ends of an AC power supply, and an AC-DC converter circuit connected to both ends of the AC power supply through the earth circuit and controlling output power. An inverter circuit for converting the output power of the AC-DC conversion circuit into high-frequency power, a parallel circuit of a load circuit and a discharge lamp connected to an output terminal of the inverter circuit, and the inverter circuit And a preheating power supply means for supplying preheating power to the filament of the discharge lamp, wherein a stray capacitance exists between the tube wall of the discharge lamp and the grounding circuit. In the lighting device, an earth circuit is provided so that the power supplied to the discharge lamp from the inverter circuit and the preheating power supply means can be controlled to a level at which the discharge lamp is substantially turned off . Output power control
AC-DC conversion circuit, inverter circuit,
Load circuit, discharge lamp, discharge lamp tube wall, stray capacitance and earth
Controlling the impedance of an electrically closed loop consisting of a circuit
Flow through an electrically closed loop
A discharge lamp lighting device characterized by controlling a current . 2. The means for controlling the power supplied from the inverter circuit to the discharge lamp to a level at which the discharge lamp is turned off is a means for short-circuiting both ends of the discharge lamp. The discharge lamp lighting device according to claim 1, wherein: Means for controlling the power supplied to said discharge lamp from said inverter circuit and said preheating power supply means to a level at which said discharge lamp is substantially extinguished; The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a means for reducing the discharge. 4. A means for supplying power to said discharge lamp from said inverter circuit and said preheating power supply means, said means for insulating said preheating power supply means from a filament of said discharge lamp, or said inverter. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is at least one of a means for insulating the discharge lamp and the discharge lamp.