JPH09308255A - Discharge lamp lighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abnormal rise of an output voltage of a chopper circuit under the condition that a discharge lamp is not lit. SOLUTION: A boosting chopper circuit 1 switches a rectified voltage of a diode bridge DB using a MOS-FETQ1 to convert this voltage to a DC voltage VDC. An inverter circuit 2 converts a DC voltage VDC into a high frequency voltage using transistors Q2 , Q3 to supply it to a load circuit 3. Here, a current feedback transformer T2 feeds back a current I1 flowing into a resonance capacitor C5 of the load circuit 3 to MOS-FETQ1 to turn on it. Meanwhile, a current feedback transformer T1 feeds back a current I2 flowing into the load circuit 3 to a transistor Q5 to turn on it and to turn off MOS-FETQ.

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 provided with a chopper circuit for converting an AC voltage into a DC voltage and an inverter circuit for converting the DC voltage of the chopper circuit into a high frequency voltage to light a discharge lamp. It is about.

[0002]

2. Description of the Related Art Conventionally, as a discharge lamp lighting device with reduced input current distortion, there has been a circuit as shown in FIG. This discharge lamp lighting device includes a diode bridge DB that rectifies a commercial AC power supply AC input via a switch SW, a step-up chopper circuit 1 that converts a rectified voltage of the diode bridge DB into a DC voltage V _DC , and a resonance inductance. A load circuit 3 including an LC series resonance circuit in which L ₂ and a resonance capacitor C ₅ are connected in series and a discharge lamp La connected in parallel with the resonance capacitor C ₅ , and a DC voltage V _DC of the step-up chopper circuit 1 An inverter circuit 2 that switches and supplies a high-frequency voltage to a load circuit 3, a first control circuit 6 that controls ON / OFF of a transistor Q ₇ of the boost chopper circuit 1, and a transistor Q of the inverter circuit 2.
_{A second} control circuit 7 for controlling ON / OFF of ₂ and Q ₃ ,
The power supply circuit 4 generates a control voltage V _CC from the rectified voltage of the diode bridge DB and supplies it to the first and second control circuits 6 and 7.

The boost chopper circuit 1 has an inductance L.
₁ and a diode D ₁ , a transistor Q ₇ and a capacitor C ₁ . Here, during the ON period of the transistor Q ₇ , the inductance L ₁ and the transistor Q 7
_A current flows through ₇ and energy is stored in the inductance L ₁ . On the other hand, during the off period of the transistor Q _7, the energy accumulated during the on-period to the inductance L ₁ is to charge the capacitor C ₁ through the diode D ₁ with the rectified voltage of the diode bridge DB, both ends of the capacitor C ₁ A DC voltage V _DC generated by boosting the rectified voltage is generated.

In the inverter circuit 2, the transistors Q ₂ and Q ₃ connected in series are connected between the outputs of the boost chopper circuit 1.
And a flywheel diode D ₂ and D ₃ connected in antiparallel to the transistors Q ₂ and Q ₃ , respectively, and connected to both ends of the transistor Q ₂ via a DC cut capacitor C ₃ to form a load circuit. It has a so-called half bridge configuration in which 3 are connected.

The load circuit 3 has a resonance inductance L ₂
And a resonance capacitor C ₅ are connected in series through one end of a filament electrode of the discharge lamp La, and the other end of the resonance capacitor C ₅ is connected through the other end of the filament electrode of the discharge lamp La and is a DC cutting capacitor. It is connected to C ₃ . The resonance capacitor C ₅ connected between the ends of the filament electrodes at both ends of the discharge lamp La also has a function of preheating the filament electrodes at both ends of the discharge lamp La.

Here, the first control circuit 6 is, for example, TDA4814A manufactured by Siemens or M manufactured by Motorola.
A power factor improving IC such as C34261 is used, and the transistor Q ₇ is on / off controlled so that the output voltage V _DC of the boost chopper circuit 1 becomes a predetermined voltage value. The second control circuit 7 alternately turns on / off the transistors Q ₂ and Q ₃ at a high frequency, supplies a high frequency voltage to the load circuit 3, and turns on the discharge lamp La at a high frequency.

On the other hand, the power supply circuit 4 has a resistor R₄₁And Zener
Diode ZD₄₁And capacitor C ₄₁Consists of
From the rectified voltage of the diode bridge DB to the control voltage V
_CCIs generated and supplied to the first and second control circuits 6 and 7.
ing. As mentioned above, the boost chopper circuit 1 is a diode.
DC voltage V by boosting the rectified voltage of the bridge DB_DCI
Output to the inverter circuit 2 and the inverter circuit 2
Star Q_Two, Q_ThreeDC voltage V_DCSwitch
Supply a high-frequency voltage to the load circuit 3 to discharge the load circuit 3.
The electric light La is lit at high frequency.

Here, when the power is turned on, the boost chopper circuit 1
In addition, when the inverter circuit 2 starts operating, the inverter circuit 2 smoothly starts the discharge lamp La.
A high starting voltage is applied after the filament electrodes on both ends of the discharge lamp La are preheated for a certain period of time in advance. That is, the switching frequency of the inverter circuit 2 is set to the resonance of the LC series resonance circuit including the resonance capacitor C ₅ and the resonance inductance L ₂ for a certain period of time after the power is turned on until the preheating of the filament electrode of the discharge lamp La is completed. The discharge lamp La was started by setting the frequency higher than the frequency and then bringing the switching frequency of the inverter circuit 2 closer to the resonance frequency of the LC series resonance circuit. (See JP-A-6-163166) However, in this discharge lamp lighting device, compared to when the discharge lamp La is lit, such as when the discharge lamp La is preheated before starting or when the discharge lamp La is difficult to light at the end of its life. And a very light load occurs. At this time, the output voltage V _DC of the step-up chopper circuit 1 may be suddenly and abnormally boosted because the load is suddenly reduced. For example, when two 40 W discharge lamps are used, power consumption of about 80 W is required at the time of lighting, but power consumption during preheating is about 5 W, and the load fluctuates greatly. The power factor improving IC of the first control circuit 6 detects the output voltage V _DC of the chopper circuit 1 and outputs the output voltage V _DC.
However, if the load fluctuation is large as described above, the gain of the error amplifier inside the power factor correction IC cannot be fully supported, so an external switching circuit or a circuit to stop the chopper operation is added. Therefore, a discharge lamp lighting device as shown in FIG. 5 has been conventionally proposed.

This discharge lamp lighting device includes a diode bridge DB for rectifying a commercial AC power supply AC input via a switch SW, and a step-up chopper circuit for smoothing a rectified voltage of the diode bridge DB by using a MOS-FET Q _1. 1, an inverter circuit 2 for converting the output voltage V _DC of the step-up chopper circuit 1 into a high frequency voltage by using the transistors Q ₂ and Q ₃ , a discharge lamp La that is turned on at a high frequency by the high frequency voltage of the inverter circuit 2, and a resonance inductance. L ₂
And a load circuit 3 including an LC series resonance circuit including a resonance capacitor C _5, a first control circuit 6 including a power factor improving IC 61 for controlling ON / OFF of the MOS-FET Q ₁ , and a transistor. A second control circuit 7 for controlling ON / OFF of Q ₃ , and a power supply circuit 4 for generating a control voltage V _CC from the rectified voltage of the diode bridge DB and supplying it to the first and second control circuits 6 and 7. Is equipped with.

The second control circuit 7 has a discharge lamp L.
A timer is provided to measure the preheating time when the lamp is turned on.
And timer capacitor C₇₁And resistance R₇₁CR
During the preceding preheating time set by the time constant, the discharge lamp L
When the filament electrode of a is preheated,
Transistor Q in control circuit 6₈Is turned on and the boost
MOS-FET Q of top circuit 1₁Control on / off
The operation of the power factor improving IC 61 is stopped. Accordingly
During the pre-heating time of the discharge lamp La, the boost chopper circuit
1 output voltage V_DCIs small and then gradually rises
Is controlled so that the load is light during the preceding preheating time.
Output voltage V of boost chopper circuit 1 _DCRises abnormally
There is no pressure.

[0011]

In the discharge lamp lighting device having the above-described structure, the input distortion is reduced, and the boosting is performed while the discharge lamp La is not lit at the time of preheating before starting the discharge lamp La or at the end of its life. In order to prevent abnormal boosting of the chopper circuit 1, it is necessary to add a circuit such as a timer to the second control circuit 7, which causes a problem that the circuit configuration of the discharge lamp lighting device becomes complicated.

Further, in order to simplify the circuit configuration of the discharge lamp lighting device, the MOS of the boost chopper circuit 1 is synchronized with the ON / OFF signal of the transistor Q ₃ of the inverter circuit 2.
Until performing the switching operation of -FETQ ₁ is easily conceivable, even in this case, the discharge lamp La is lighted,
It is necessary to add a circuit for stopping the operation of the boost chopper circuit 1, which causes a problem that the circuit configuration becomes complicated.

The present invention has been made in view of the above problems, and has a simple circuit configuration, which improves input distortion and prevents an abnormal increase in the output voltage of the chopper circuit. It is intended to provide.

[0014]

In order to achieve the above object, the present invention comprises a rectifying circuit for full-wave rectifying an AC power source, a first switching element, an inductance, a diode and a capacitor. An LC in which a chopper circuit for converting the rectified voltage of the rectifier circuit into a DC voltage, a resonance inductance and a resonance capacitor are connected in series.
A load circuit including a series resonance circuit and a discharge lamp connected in parallel with a resonance capacitor; and an inverter circuit that converts the DC voltage of the chopper circuit into a high frequency voltage by using a second switching element and supplies the high frequency voltage to the load circuit. And turning on / off the first switching element based on the phase difference between the current flowing through the load circuit and the current flowing through one component forming the load circuit, and when the discharge lamp is not lit, the load is Since the phase of the current flowing in the circuit and the current flowing in one component of the load circuit are equal, the operation of the chopper circuit can be stopped by turning off the first switching element.

According to a second aspect of the present invention, in the first aspect of the invention, an inverter circuit is connected between one ends of the filament electrodes at both ends of the discharge lamp via a resonance inductance, and a resonance capacitor is provided between the other ends of the filament electrodes. And the current flowing through the load circuit is fed back for controlling the off period of the first switching element, and the current flowing through the resonance capacitor is fed back for controlling the on period of the first switching element. When not lit, the phase of the current flowing in the load circuit and the phase of the current flowing in the resonance capacitor become equal, so the operation of the chopper circuit can be stopped by turning off the first switching element.

According to a third aspect of the invention, in the first aspect of the invention, a resonance capacitor is connected between one ends of the filament electrodes at both ends of the discharge lamp to which the inverter circuit is connected, and the other ends of the filament electrodes are preheated. Connect the switch element that is turned on to prevent the current flowing through the load circuit from
The current flowing through the discharge lamp is fed back for the control of the ON period of the switching element of 1 to the control of the OFF period of the first switching element, and the current flowing in the load circuit is controlled by turning on the switch element during preheating. Since the phases of the currents flowing through the discharge lamps are equal, it is possible to stop the operation of the chopper circuit by turning off the first switching element.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) As shown in FIG. 1, a discharge lamp lighting device of the present embodiment is a diode bridge D which is a rectifying circuit for full-wave rectifying the AC power supply AC input through a switch SW.
B and the diode bridge DB rectified voltage to the DC voltage V
Step-up chopper circuit 1 which is a chopper circuit for converting to _DC ,
The booster chopper circuit 1 is provided with an inverter circuit 2 for converting the output voltage _VDC into a high frequency voltage, and a load circuit 3 including a discharge lamp La and an LC series resonance circuit which are turned on at a high frequency by the high frequency voltage of the inverter circuit 2.

The boost chopper circuit 1 has an inductance L
₁ , a diode D ₁ , a MOS-FET Q ₁ as a first switching element, and a capacitor C _1, and the energy accumulated in the inductance L ₁ during the ON period of the MOS-FET Q ₁ is the MOS-FET Q _1. by charging the capacitor C ₁ through the diode D ₁ in conjunction with the rectified voltage of the diode bridge DB ₁ off period, which boosts the output voltage V _DC.

In the inverter circuit 2, between the both ends of the capacitor C ₁ of the boost chopper circuit 1, the transistors Q ₂ and Q ₃ and the transistors Q ₂ and Q ₃ which are the second switching elements connected in series are connected in antiparallel. The connected diodes D ₂ and D ₃ are connected, and the transistor Q ₂
A load circuit 3 is connected between both ends of the capacitor via a DC cut capacitor C ₃ . A current feedback transformer T ₁ is inserted in series with the load circuit 3 in the inverter circuit 2, and the current feedback transformer T ₁ feeds back the current I ₂ flowing in the load circuit 3 to form the transistors Q ₂ , Q ₂ . ₃ is turned on / off alternately.

The load circuit 3 has a resonance inductance L ₂
And the LC series resonance circuit composed of the resonance capacitor C _5, connecting the resonant capacitor C ₅ between the other end of the filament electrode together with the inverter circuit 2 are connected via a resonant inductance L ₂ between the one end of the filament electrode Discharge lamp La, resonance capacitor C ₅ and discharge lamp L
It is composed of one component that is inserted between the filament electrode of a and the load circuit 3 to constitute the load circuit 3, that is, a current feedback transformer T ₂ that feeds back the current I ₁ flowing through the resonance capacitor C ₅ .

Since the capacitance of the DC cut capacitor C ₃ is much larger than the capacitance of the resonance capacitor C ₅ , the resonance inductance L ₂ and the resonance capacitor C It is hardly involved in the resonance condition of the LC series resonance circuit composed of ₅ . In addition, the inverter circuit 2 includes a starting circuit 2a for starting the inverter circuit 2.
The starting circuit 2a includes a resistor R ₅ , a capacitor C _2, and a bidirectional trigger element Q ₄ such as a diac.
It is composed of Here, the voltage across the capacitor C ₂ charged through the resistor R ₅ is the bidirectional trigger element Q.
At which point ₄ of breakover voltage, bidirectional trigger element Q ₄ is turned on, to supply the base current to the base electrode of the transistor Q _3, and turns on the transistor Q _3.

In this discharge lamp lighting device, the load circuit 3
Swing capacitor C_FiveCurrent I flowing through ₁And load circuit 3
Current I_TwoAnd is fed back, and the MO of the boost chopper circuit 1 is returned.
S-FETQ₁Is on / off controlled. That is, MO
S-FETQ₁Signal to turn on is for resonance of load circuit 3
Capacitor C_FiveCurrent I flowing through₁Synchronized with the phase of
You. On the other hand, MOS-FETQ₁Signal to turn off is negative
Current I flowing in the load circuit 3 _TwoWith transistor Q_Two, Q_ThreeTo
Current feedback transformer T for feedback₁Obtained from the third winding of
Therefore, the current I flowing through the load circuit 3_TwoSynchronized with the phase of
You.

Here, at the time of preheating or at the end of life of the discharge lamp La.
When the discharge lamp La is difficult to light up in
Is not lit, the resonance capacitor C_FiveFlow
Current I₁And the current I flowing through the load circuit 3_TwoThe phases are equal
However, when the discharge lamp La lights up, the current I₁
Is the current I_TwoIt is in phase with respect to. Accordingly
Until the discharge lamp La lights up, the current I₁In sync with
Current return transformer T_TwoTo MOS-FET Q₁ON signal
At the same time that_TwoCurrent feedback
Lance T₁From resistance R₆Through transistor Q_FiveBe
Source current is supplied to the transistor Q_FiveIs turned on
Therefore, MOS-FETQ ₁Is turned off, so M
OS-FETQ₁Is practically turned off, and the boost
The top circuit 1 does not operate.

On the other hand, when the discharge lamp La lights up, the current I ₁
Becomes a leading phase with respect to the current I ₂ , so that the MOS-FE
After the ON signal is input to TQ ₁ , the OFF signal comes to be input after a lapse of time corresponding to the phase difference, and the boost chopper circuit 1 starts operating. That is, the current I ₁
In synchronization with the current feedback transformer T ₂ to the MOS-FET Q
_When the ON signal is input to ₁ , the MOS-FET Q ₁ is turned on and energy is stored in the inductance L ₁ . After that, the current feedback transformer T ₁ is synchronized with the current I _2.
Base current to the transistor Q ₅ through a resistor R ₆ from the tertiary winding is supplied, the transistor Q ₅ is turned on, MO
S-FETQ ₁ is turned off. And MOS-FETQ
_In the off period of ₁ , the energy stored in the inductance L ₁ charges the capacitor C ₁ via the diode D ₁ , the boost chopper circuit 1 starts operating, and a predetermined output voltage V _DC can be obtained. .

Further, this discharge lamp lighting device is not provided with a circuit for keeping the output voltage V _DC of the step-up chopper circuit 1 constant, but the phase difference between the currents I ₁ and I ₂ is obtained by the step-up chopper circuit 1. Since the current is fed back to the on / off control of the MOS-FET Q ₁ , the equivalent resistance of the discharge lamp La increases as the current I ₁ decreases, and the degree of phase advance of the current I ₁ flowing through the resonance capacitor C ₅ is increased. MOS becomes smaller
-The ON period of the FET Q ₁ becomes short. Therefore, when the load becomes light, the output voltage V _DC of the boost chopper circuit 1
Can be prevented from being boosted.

As described above, with a simple circuit configuration, the input power is
Until the discharge lamp La lights up while reducing the flow distortion.
Output voltage V of boost chopper circuit 1 under light load_DC
Can be prevented from rising abnormally. (Embodiment 2) The discharge lamp lighting device of the present embodiment is
Although the basic circuit configuration is the same as that of the state 1 circuit,
As shown, the transistor Q of the inverter circuit 2_ThreeNo
ON / OFF control circuit 5 and diode bridge
Control voltage V from DB rectified voltage _CCGenerate control circuit 5
And a power supply circuit 4 for supplying

The control circuit 5 is a comparator IC₁, IC
_TwoAnd resistance R₁₇~ R_{twenty three}And capacitor C₁₂, C₁₃Etc.
And the power supply circuit 4 has a resistor R₄₁And capacitor C₄₁
And Zener diode ZD₄₁It is composed of This
Here, transistor Q_ThreeON / OFF of the current feedback
Once T₁Is controlled by the control circuit 5. Sand
The current feedback transformer T₁Is the transistor Q _ThreeBase of
The current flowing in the load circuit 3 is applied to the electrode by I_TwoHave returned,
Transistor Q_ThreeON signal is current I_TwoCurrent in sync with
Feedback transformer T₁Is given by Meanwhile, control
In the circuit 5, the comparator IC₁Is the capacitor C₁₂Charge of
Electric voltage and resistance R₁₈, R₁₉And R₂₀Voltage divided by
Compared with the pressure, the capacitor C₁₂And resistance R₁₇CR
After a fixed time determined by the time constant, the comparator IC
₁When the output of becomes high, the transistor Q₆Turns on
And transistor Q_ThreeIs supplied with an off signal.

Further, the control circuit 5 is provided with a timer for setting the preheating time of the discharge lamp La, and the comparator IC ₂ divides the voltage by the resistors R ₂₁ and R ₂₃ and the charging voltage of the capacitor C ₁₃ . And the pre-heating time of the discharge lamp La is set by the CR time constant determined by the capacitor C ₁₃ and the resistor R ₂₂ . Therefore, in this discharge lamp lighting device, the filament electrode of the discharge lamp La is preliminarily preheated by shortening the ON period of the transistor Q _{3 for} a fixed time determined by the capacitor C ₁₃ and the resistor R ₂₂ after the power is turned on. After that, the discharge lamp La is turned on.

By the way, also in the discharge lamp lighting device of the present embodiment, the step-up chopper circuit 1 is carried out similarly to the first embodiment.
The ON / OFF of the MOS-FET Q ₁ is controlled, and the ON signal is given to the MOS-FET Q ₁ by feeding back the current flowing in the resonance capacitor C ₅ by the current feedback transformer T ₂ . On the other hand, the off signal of the MOS-FETs Q ₁ is given by the signal of the tertiary winding of the current feedback transformer T ₁ for feeding back the current I ₂ flowing in the load circuit 3 for controlling the on / off transistors Q _2, Q ₃ ing. At this time, in the inverter circuit 2, in order to control the on period of the transistor Q ₃ , the MOS-FET Q 1 of the boost chopper circuit ₁ is turned off in synchronization with the on signal of the transistor Q ₂ .

Even in the circuit to which the preceding preheating function is added as in this embodiment, since the discharge lamp La is not turned on during the preceding preheating, the current I flowing through the resonance capacitor C ₅ is set as described above. The phases of ₁ and the current I ₂ flowing through the load circuit 3 are completely the same. Accordingly, MOS-FETs Q ₁ of the boost chopper circuit 1 is turned off, the step-up chopper circuit 1 does not operate in a state where the discharge lamp La is not lit, the output voltage V _DC of the boost chopper circuit 1 is abnormally boost There is no such thing. On the other hand, when the discharge lamp La is lit, the phase of the current I ₁ leads the phase of the current I ₂ , so that the MOS
-The ON period of the FET Q ₁ occurs, and the operation of the boost chopper circuit 1 starts.

Since the configuration other than the power supply circuit 4 and the control circuit 5 is the same as that of the first embodiment, the description thereof is omitted. (Third Embodiment) In the discharge lamp lighting device according to the present embodiment, the switch element is provided in parallel with the resonance capacitor C ₅ of the load circuit 3 in the first embodiment.

As shown in FIG. 3, the load circuit 3 includes an LC series resonance circuit including a resonance inductance L ₂ and a resonance capacitor C _5, and a resonance capacitor between one ends of filament electrodes to which the inverter circuit 2 is connected. The discharge lamp La is connected to C _5, and the switch element SW ₁ is connected between the other ends of the filament electrodes of the discharge lamp La. The switch element SW ₁ is turned on when the discharge lamp La is preheated. There is.

In this embodiment, M of the boost chopper circuit 1 is used.
The current feedback transformer T ₁ is used to control the ON period of the OS-FET Q ₁ , and the current I ₂ flowing in the load circuit 3 is fed back, and the current feedback transformer T ₂ is controlled to control the OFF period of the MOS-FET Q _1. The current I ₃ flowing through the discharge lamp La is fed back by using this. Here, when the switch element SW ₁ is turned on during the preheating of the discharge lamp La, the resonance capacitor C ₅
There therefore is short-circuited, the phase of the current I ₃ in which the current I ₂ flowing in the load circuit 3 flows to the discharge lamp La is equal, as described above, the boost chopper circuit 1 stops operating. On the other hand, when the discharge lamp La is turned on, the current I ₃ has a delay phase with respect to the current I ₂ , and the ON period of the MOS-FET Q ₁ occurs, so that the boost chopper circuit 1 starts operating.

Thus, in this circuit, the boost chopper circuit 1
As an ON / OFF signal for controlling the MOS-FET Q ₁ of, the current I ₂ flowing in the load circuit is fed back to give an ON signal, and the current I ₃ flowing in the discharge lamp La is fed back to give an OFF signal. Similar to the discharge lamp lighting device of the first or second embodiment, it is possible to prevent the output voltage V _DC of the boost chopper circuit 1 from abnormally boosting when the discharge lamp La is not lit.

Since the circuit configuration other than the load circuit 3 is the same as that of the first embodiment, its explanation is omitted. Further, although the present embodiment uses a semiconductor switch or a mechanical switch such as the switch element SW _1, the switch element SW ₁
It goes without saying that other switch elements having the same on / off function, for example, a switch element such as a large capacity positive temperature coefficient thermistor may be used instead of the above.

In the discharge lamp lighting devices of the first to third embodiments, the boost chopper circuit 1 is used for all the chopper circuits for converting the AC power supply into the DC power supply, but so-called step-down chopper circuits and step-up / step-down chopper circuits are used. Needless to say, it may be used. In the inverter circuit 2,
Transistors Q ₂ and Q ₃ as the second switching element
However, it goes without saying that a switching element such as a MOS-FET may be used.

[0037]

According to the invention of claim 1, as described above, a rectifier circuit for full-wave rectifying an AC power supply, a first switching element, an inductance, a diode, and a capacitor are used to convert the rectified voltage of the rectifier circuit into a direct current. A chopper circuit for converting into a voltage, a load circuit including an LC series resonance circuit in which a resonance inductance and a resonance capacitor are connected in series and a discharge lamp connected in parallel with the resonance capacitor, and a DC voltage of the chopper circuit An inverter circuit that converts the high-frequency voltage into a high-frequency voltage by using the second switching element and supplies the high-frequency voltage to the load circuit;
When the switching element is turned on / off and the discharge lamp is not lit, the phase of the current flowing through the load circuit and the current flowing through one component forming the load circuit become equal. In the OFF state, the operation of the chopper circuit can be stopped, the input current distortion can be reduced with a simple circuit configuration, and the output voltage of the chopper circuit can be prevented from being abnormally boosted. Further, there is an effect that the output voltage of the chopper circuit can be kept constant even when the load changes due to the power supply change or the like.

According to a second aspect of the present invention, an inverter circuit is connected between one ends of the filament electrodes at both ends of the discharge lamp via a resonance inductance, and a resonance capacitor is connected between the other ends of the filament electrodes to connect to the load circuit. The flowing current is fed back for controlling the off period of the first switching element, and the current flowing to the resonance capacitor is fed back for controlling the on period of the first switching element. Since the current flowing through the circuit and the current flowing through the resonance capacitor have the same phase, the operation of the chopper circuit can be stopped by turning off the first switching element, and the input current distortion can be reduced with a simple circuit configuration. At the same time, it is possible to prevent the output voltage of the chopper circuit from being boosted abnormally. Further, there is an effect that the output voltage of the chopper circuit can be kept constant even when the load changes due to the power supply change or the like.

According to a third aspect of the invention, a resonance capacitor is connected between one ends of the filament electrodes at both ends of the discharge lamp to which the inverter circuit is connected, and a switching element which is turned on at the time of preheating is connected between the other ends of the filament electrodes. The current flowing in the load circuit is fed back for controlling the ON period of the first switching element, and the current flowing in the discharge lamp is fed back for controlling the OFF period of the first switching element. By turning on the switch element, the phases of the current flowing through the load circuit and the current flowing through the discharge lamp become equal, so that the operation of the chopper circuit can be stopped by turning off the first switching element, and a simple circuit With the configuration, it is possible to reduce the input current distortion and prevent the output voltage of the chopper circuit from being abnormally boosted.

[Brief description of drawings]

FIG. 1 is a circuit diagram illustrating a discharge lamp lighting device according to a first embodiment.

FIG. 2 is a circuit diagram showing a discharge lamp lighting device according to a second embodiment.

FIG. 3 is a circuit diagram showing a discharge lamp lighting device according to a third embodiment.

FIG. 4 is a circuit diagram showing a conventional discharge lamp lighting device.

FIG. 5 is a circuit diagram showing another discharge lamp lighting device of the above.

[Explanation of symbols]

1 Boost Chopper Circuit 2 Inverter Circuit 3 Load Circuit I _1, I ₂ Current V _DC DC Voltage C ₅ Resonance Capacitor DB Diode Bridge T _1, T ₂ Current Feedback Transformer Q ₁ MOS-FET Q _2, Q _3, Q ₅ Transistor

Claims (3)

[Claims] 1. A rectifier circuit for full-wave rectifying an AC power supply;
Chopper circuit which is composed of a switching element, an inductance, a diode and a capacitor for converting the rectified voltage of the rectifier circuit into a DC voltage, an LC series resonance circuit in which a resonance inductance and a resonance capacitor are connected in series, and the resonance capacitor. And a load circuit including a discharge lamp connected in parallel with the load circuit, and an inverter circuit that converts the DC voltage of the chopper circuit into a high frequency voltage using a second switching element and supplies the high frequency voltage to the load circuit. A discharge lamp lighting device, wherein the first switching element is turned on / off based on a phase difference between a current flowing in a circuit and a current flowing in one component forming the load circuit. 2. The load circuit, wherein the inverter circuit is connected between one ends of filament electrodes at both ends of the discharge lamp via the resonance inductance, and the resonance capacitor is connected between the other ends of the filament electrodes. The current flowing through the first switching element for controlling the off period of the first switching element, and the current flowing through the resonance capacitor through the first switching element.
2. The discharge lamp lighting device according to claim 1, wherein the switching lamp is fed back for controlling the ON period of the switching element. 3. The resonance capacitor is connected between one ends of filament electrodes at both ends of the discharge lamp to which the inverter circuit is connected, and a switching element which is turned on at the time of preheating is connected between the other ends of the filament electrodes. The current flowing through the load circuit is fed back for controlling the ON period of the first switching element, and the current flowing through the discharge lamp is fed back for controlling the OFF period of the first switching element. The discharge lamp lighting device according to claim 1.