JP2004193075A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To alleviate voltage stress in a normal operation and transition on a switch element constituting a preheating control circuit to suppress a filament preheating current in lighting, in a discharge lamp lighting device to light a discharge lamp with a high frequency. <P>SOLUTION: In the discharge lamp lighting device which has the preheating control circuit constituted by including at least a series circuit of a primary winding wire of a converter element T1 for preheating and a switch element Q3 for preheating, and in which the switch element Q3 is controlled to be off in a normal operating state of an inverter, a clamping circuit constituted of at least a diode D1 is connected to a prescribed direct current power supply E1 from a high voltage side of the switch element Q3, an anode side of the diode D1 constituting the clamping circuit is connected to the high voltage side of the switch element Q3, and a cathode side is connected to the prescribed direct current power supply E1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a discharge lamp lighting device for lighting a hot cathode type discharge lamp at a high frequency by an output of an inverter circuit.
[0002]
[Prior art]
[Patent Document 1]
JP-A-2001-351790
Conventionally, in a discharge lamp lighting device for converting a DC power supply to a high frequency and lighting a hot cathode discharge lamp load, a preheating control circuit as disclosed in JP-A-2001-351790 has been devised for the purpose of improving the circuit efficiency of the device. I have.
[0004]
(Conventional example 1)
FIG. 14 shows a circuit diagram of the first conventional example. Hereinafter, the circuit configuration will be described. The DC power supply E is connected to a series circuit of switching elements Q1 and Q2. The switching elements Q1 and Q2 are alternately turned on and off by the control circuit unit 1. To both ends of the switching element Q2, a series circuit of a capacitor C4, a preheating transformer T1, and a preheating switch Q3 is connected in parallel, and a series resonance circuit of an inductor L1 and a capacitor C1 is connected via a DC cut capacitor C0. I have. Discharge lamps la are connected in parallel to both ends of the capacitor C1. The filament terminals A and B of the discharge lamp la are connected to the terminals a and b of the first secondary winding of the preheating transformer T1 via the capacitor C2, and the filament terminals C and D are connected via the capacitor C3 to the preheating transformer. It is connected to terminals c and d of the second secondary winding of T1. The switching elements Q1 and Q2, the DC cut capacitor C0, the resonance (current limiting) inductor L1, the resonance capacitor C1, and the discharge lamp la constitute an inverter circuit. The DC cut capacitor C4, the preheating transformer T1, the preheating switch Q3, and the capacitors C2 and C3 constitute a preheating current control circuit.
[0005]
Hereinafter, the circuit operation of FIG. 14 will be described. In the inverter circuit, the switching elements Q1 and Q2 are alternately turned on and off by a drive signal from the control circuit unit 1 to the switching elements Q1 and Q2, and the inverter circuit has a rectangular shape in a resonance load circuit including an inductor L1, a capacitor C1, and a discharge lamp la. The discharge lamp la is turned on at a sinusoidal high frequency by applying a wave-like high frequency voltage. FIG. 15 is a characteristic diagram showing the relationship between the operating frequency of the inverter and the resonance voltage. The vertical axis represents the resonance voltage of the capacitor C1 applied to the discharge lamp la, and the horizontal axis represents the operating frequency of the switching elements Q1 and Q2 (the inverter operating frequency). ).
[0006]
When the power is turned on, the inverter circuit starts oscillating at a frequency fph that is higher than the no-load resonance frequency fo determined by the inductor L1 and the capacitor C1 so that the discharge lamp la is not lit, and the discharge lamp la can be lit. Inappropriate resonance voltage is applied. At this time, the preheating switch Q3 is on, and a high frequency voltage in the form of a rectangular wave is applied to the preheating transformer T1, which is applied to the filament of the discharge lamp la from the secondary winding of the preheating transformer T1 via the capacitors C2 and C3. Applied to heat the filament (preceding preheating). After performing the pre-heating for a predetermined time, the operating frequency of the inverter changes to fst (starting voltage application frequency) so that the discharge lamp la can be turned on, and a resonance voltage is applied so that the discharge lamp la can be turned on. , The discharge lamp la is turned on (start mode). After that, the frequency changes to ft (lighting frequency) and shifts to a normal lighting state. Further, at this time, the preheating switch Q3 is turned off, and the application of the high frequency voltage on the primary side of the preheating transformer T1 is cut off, so that the filament current flowing on the secondary side becomes almost 0 (lighting mode). Thus, loss due to the filament current at the time of lighting can be almost eliminated, so that the circuit efficiency can be greatly improved.
[0007]
The conventional example has a function of detecting that the discharge lamp la has come off and stopping the oscillation of the inverter circuit (no-load detection circuit), but is not shown in the circuit diagram of the conventional example.
[0008]
[Problems to be solved by the invention]
When the inverter circuit is turned on and the preheating switch Q3 is turned off, the current flowing to the primary side of the preheating transformer T1 in the preceding preheating mode / starting mode is cut off. There is a problem that an electromotive force is generated, applied to both ends of the preheating switch Q3, and an excessive voltage stress higher than the DC power supply voltage E of the inverter circuit is applied. FIG. 16 shows the voltage VQ3 across the preheating switch Q3 when the preheating switch Q3 changes from on to off in the conventional example. In the figure, E is a DC power supply voltage (410 V here), and the peak voltage of the preheating switch Q3 has reached 570V.
[0009]
In the normal lighting mode, even if the preheating switch Q3 is off, a parasitic diode exists in the reverse direction between the drain and the source of the preheating switch (MOSFET) Q3. In addition, there is a slight capacitance component between the drain and the source. As a result, when the switching Q2 is turned on, a current flows from the capacitor C4 through the path of the switching element Q2 → the parasitic diode of the preheating switch Q3 → the preheating transformer T1, so that almost no voltage is applied to the preheating switch Q3, but the switching element Q2 is turned off. Since the capacitance between the drain and source of the preheating switch Q3 is sometimes much smaller than the capacitance of the capacitor C4, the DC power supply voltage E is almost applied to the preheating switch Q3. Current flows for a short time, and then the current path of the preheating transformer T1 is interrupted. When the voltage of the preheating switch Q3 rises, an overshoot voltage is generated in the preheating transformer T1 by the back electromotive force, It is applied to the preheating switch Q3, and excessive voltage stress is applied. There is a problem in that. FIG. 17 shows a voltage waveform applied to both ends of the preheating switch Q3 during normal lighting in the conventional example. In the figure, E is the DC power supply voltage (410 V here), and the peak voltage of the preheating switch Q3 has reached 530V.
[0010]
When the load is removed, a lamp current flows between the preheating windings a and b or cd between the moment when the filament is removed and the time when the no-load detection circuit operates, and this current is converted into a voltage on the primary side. An overshoot voltage is generated in the same manner as the back electromotive force on the primary side of the preheating transformer T1, and is applied to the preheating switch Q3, resulting in excessive voltage stress. FIG. 18 (a) shows a voltage waveform applied to the preheating switch Q3 when the load is removed in the conventional example, and FIG. 18 (b) is a partially enlarged view thereof.
[0011]
As a countermeasure against the voltage stress applied to the preheating switch Q3 as described above, conventionally, when the preheating switch Q3 changes from on to off, the control circuit unit 1 responds to the voltage stress when the preheating switch Q3 turns off. The speed of extracting the gate charge of the preheating switch Q3 is slowed down, and a countermeasure for suppressing the overshoot voltage is taken by using the unsaturated region of the preheating switch Q3. However, it has been impossible to take measures against overvoltage during normal lighting and when removing the load. Further, measures have been taken to suppress the voltage stress by inserting a capacitor between the drain and source of the preheating switch Q3 to slow down the voltage rise of the preheating switch Q3. However, the overshoot voltage is sufficiently suppressed. That was impossible.
[0012]
The present invention has been made in view of such a point, and an object thereof is a discharge lamp lighting device for lighting a discharge lamp load at a high frequency, and a preheating control circuit for suppressing a filament preheating current at the time of lighting. It is an object of the present invention to provide a means capable of accurately and relatively inexpensively realizing a stress protection circuit for reducing voltage stress during normal operation and transient state of a switching element to be constituted by a circuit configuration with a small number of components.
[0013]
[Means for Solving the Problems]
According to the discharge lamp lighting device of the first aspect, a hot cathode type discharge lamp having a filament, an inverter circuit for converting a DC power supply to a high frequency and supplying high frequency power to the discharge lamp, A preheating control circuit for supplying a filament current to a filament of the discharge lamp during a starting operation state to preheat the filament, and for suppressing a filament current flowing to the filament of the discharge lamp during a lighting operation state; The circuit includes at least a series circuit of a primary winding of a preheating transformer element and a preheating switch element, wherein the switch element is controlled to be turned off in a normal operation state of the inverter. In the lamp lighting device, a clamp circuit including at least a diode from a high voltage side of the switch element is connected to a predetermined DC power supply. Ri, the anode side of the diode constituting the clamp circuit is connected to the high voltage side of the switch element, the cathode is characterized in that it is connected to a predetermined DC power source.
[0014]
According to the invention of claim 2, in claim 1, the predetermined DC power supply connected to the cathode side of the diode constituting the clamp circuit has a voltage lower than the rated voltage of the switch element, and The voltage is equal to or higher than the DC power supply voltage.
According to a third aspect of the present invention, in the first or second aspect, the switch element is constituted by a MOSFET.
According to the invention of claim 4, the discharge lamp lighting device according to any one of claims 1 to 3, wherein the predetermined DC power supply is a DC power supply voltage of an inverter.
According to a fifth aspect of the present invention, there is provided a discharge lamp lighting device according to any one of the first to fourth aspects, wherein an impedance element is inserted in series with the diode of the clamp circuit.
According to a sixth aspect of the present invention, in the discharge lamp lighting device according to the fifth aspect, the impedance element inserted in series with the diode is a resistor.
According to a seventh aspect of the present invention, in the discharge lamp lighting device according to the fifth aspect, the impedance element inserted in series with the diode is a ferrite bead.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
FIG. 1 shows a circuit diagram of Embodiment 1 of the present invention. Hereinafter, the circuit configuration will be described. The DC power supply E is connected to a series circuit of switching elements Q1 and Q2. The switching elements Q1 and Q2 are alternately turned on and off by the control circuit unit 1. A series circuit of a capacitor C4, a preheating transformer T1, and a preheating switch Q3 is connected in parallel to both ends of the switching element Q2. The anode of the diode D1 is connected to the connection point between the preheating transformer T1 and the preheating switch Q3. The cathode of the diode D1 is connected to the positive electrode of the DC power supply E1. The negative electrode of the DC power supply E1 is grounded. A series resonance circuit of the inductor L1 and the capacitor C1 is connected to both ends of the switching element Q2 via a DC cut capacitor C0. Discharge lamps la are connected in parallel to both ends of the capacitor C1. The filament terminals A and B of the discharge lamp la are connected to the terminals a and b of the first secondary winding of the preheating transformer T1 via the capacitor C2, and the filament terminals C and D are connected via the capacitor C3 to the preheating transformer. It is connected to terminals c and d of the second secondary winding of T1. The switching elements Q1 and Q2, the DC cut capacitor C0, the resonance (current limiting) inductor L1, the resonance capacitor C1, and the discharge lamp la constitute an inverter circuit. The DC cut capacitor C4, the preheating transformer T1, the preheating switch Q3, and the capacitors C2 and C3 constitute a preheating current control circuit. The diode D1 and the DC power supply E1 constitute a clamp circuit for suppressing voltage stress on the preheating switch Q3.
[0016]
Hereinafter, the circuit operation of FIG. 1 will be described. In the inverter circuit, the switching elements Q1 and Q2 are alternately turned on and off by a drive signal from the control circuit unit 1 to the switching elements Q1 and Q2, and the inverter circuit has a rectangular shape in a resonance load circuit including an inductor L1, a capacitor C1, and a discharge lamp la. The discharge lamp la is turned on at a sinusoidal high frequency by applying a wave-like high frequency voltage. FIG. 2 is a characteristic diagram showing the relationship between the operating frequency of the inverter and the resonance voltage. In the figure, the vertical axis represents the resonance voltage of the capacitor C1 applied to the discharge lamp la, and the horizontal axis represents the operating frequency of the switching elements Q1 and Q2 ( (Inverter operating frequency).
[0017]
When the power is turned on, the inverter circuit starts oscillating at a frequency fph that is higher than the no-load resonance frequency fo determined by the inductor L1 and the capacitor C1 so that the discharge lamp la is not lit, and the discharge lamp la can be lit. Inappropriate resonance voltage is applied. At this time, the preheating switch Q3 is turned on, and a rectangular wave high frequency voltage is applied to the preheating transformer T1 by using the capacitor C4 as a DC cut capacitor, and the capacitor C2 and C3 are supplied from the secondary winding of the preheating transformer T1. This is applied to the filament of the discharge lamp la via the heater to heat the filament (preceding preheating). After performing the pre-heating for a predetermined time, the operating frequency of the inverter changes to fst (starting voltage application frequency) so that the discharge lamp la can be turned on, and a resonance voltage is applied so that the discharge lamp la can be turned on. , The discharge lamp la is turned on (start mode). After that, the frequency changes to ft (lighting frequency) and shifts to a normal lighting state. Further, at this time, the preheating switch Q3 is turned off, and the application of the high frequency voltage on the primary side of the preheating transformer T1 is cut off, so that the filament current flowing on the secondary side becomes almost 0 (lighting mode). Thus, loss due to the filament current at the time of lighting can be almost eliminated, so that the circuit efficiency can be greatly improved.
[0018]
Although the present embodiment has a function (no-load detection circuit) for detecting that the discharge lamp la has come off and stopping the oscillation of the inverter circuit, it is not shown in the circuit diagram of the conventional example. .
[0019]
The DC power supply E1 to which the clamp circuit is connected is equal to or lower than the rated voltage of the preheating switch Q3, equal to or higher than the DC power supply voltage E of the inverter, and has a sufficient capacitance component. With this clamp circuit, even if a voltage higher than the DC power supply voltage E of the inverter is applied to both ends of the preheating switch Q3, when the potential of the DC power supply E1 is reached, the voltage is clamped at the potential of the DC power supply E1. Not applied.
[0020]
For example, as described in the conventional example, when the preheating switch Q3 is turned off from on, the current on the primary side of the preheating transformer T1 is cut off, so a back electromotive force is generated on the primary side of the preheating transformer T1. Since the voltage is superimposed on the DC power supply voltage E of the inverter and applied to both ends of the preheating switch Q3, an excessive voltage is applied. However, the voltage VQ3 across the preheating switch Q3 is equal to the potential of the DC power supply E1 as shown in FIG. , Voltage stress can be reduced.
[0021]
The operation when the preheating switch Q3 is off at the time of normal lighting will be described. At this time, although a very small but capacitive component exists at both ends of the preheating switch Q3, the capacitance is stored in the capacitor C4. Since the voltage is much smaller than that, the voltage across the switching element Q2 is almost applied to the preheating switch Q3, and a waveform synchronized with the voltage across the switching element Q2 appears. When the voltage rises, a small amount of current for charging the capacitance component of the preheating switch Q3 flows, and is immediately shut off, and a back electromotive force is generated on the primary side of the preheating transformer T1, which is the preheating switch. A voltage superimposed on both ends of Q3 and higher than the DC power supply voltage E of the inverter is continuously applied each time the switching element Q2 is turned off. However, since this voltage is clamped by the potential of the DC power supply E1 as shown in FIG. 4, voltage stress can be reduced.
[0022]
In addition, when the load is removed during lighting, although it has a function of detecting that the load has been removed and stopping the oscillation of the inverter, during the response delay time until the inverter stops oscillation, Transient sneak current of resonance current into the secondary winding (between a-b and cd) of the preheating transformer T1 generates a voltage on the primary side, and generates an excessive voltage across the preheating switch Q3. . However, since this voltage is clamped by the potential of the DC power supply E1 as shown in FIG. 4, voltage stress can be reduced.
[0023]
In any operation, by setting the potential of the DC power supply E1 to be equal to or lower than the rated voltage of the preheating switch Q3 and equal to or higher than the power supply voltage E of the inverter, the voltage stress of the preheating switch Q3 can be suppressed to the rated voltage or less. In addition, it is possible to prevent the current from flowing from the power supply voltage E of the inverter to the DC power supply E1 in an operation other than the time when the voltage stress occurs.
[0024]
Although the present embodiment is an example of an inverter circuit connected to a DC power supply, a similar effect can be obtained even when a circuit (for example, a step-up chopper circuit) for rectifying and smoothing an AC power supply is connected to this DC power supply. Needless to say.
[0025]
According to the present embodiment, the voltage stress generated in the preheating switch Q3 can be reduced with a simple and inexpensive configuration, and can be reliably suppressed within the voltage rating of the preheating switch Q3. Therefore, a switch having a lower rated voltage can be used as the preheating switch Q3 than when there is no clamp circuit.
[0026]
(Embodiment 2)
FIG. 5 shows a second embodiment of the present invention. This embodiment is an example in which the preheating switch Q3 is a MOSFET and the DC power supply E1 is a power supply voltage E of an inverter in the first embodiment. The power supply voltage E of the inverter is about 410V.
[0027]
The detailed operation is the same as that of the first embodiment, and a duplicate description is omitted. However, since the voltage VQ3 across the preheating switch Q3 with and without the diode D1 was actually measured, the results are shown in FIGS. 9 and will be described.
[0028]
As for the voltage stress during the normal operation, when the diode D1 is provided as shown in FIG. 6A, the voltage of the preheating switch Q3 is clamped by the power supply voltage E (about 410 V) of the inverter. When there is no diode D1, a voltage (about 530 V) higher than the power supply voltage E of the inverter is applied to the preheating switch Q3 as shown in FIG. 6B.
[0029]
When the preheating switch Q3 is turned off from on, if the diode D1 is present as shown in FIG. 7A, the voltage of the preheating switch Q3 is clamped by the power supply voltage E of the inverter. When there is no diode D1, a voltage (about 570V) higher than the power supply voltage E of the inverter is applied to the preheating switch Q3.
[0030]
When the load comes off during lighting, and when there is a diode D1 as shown in FIG. 8, the voltage of the preheating switch Q3 is clamped by the power supply voltage E of the inverter. When there is no diode D1, a high voltage (about 770 V) is applied to the preheating switch Q3 as shown in FIG. 8 and 9, (a) shows the voltage across the preheating switch Q3 when the load is removed, and (b) is a partially enlarged view thereof.
[0031]
In the present embodiment, the voltage applied to the preheating switch Q3 is clamped by the power supply voltage E of the inverter in any operation. It can be suppressed to the following.
[0032]
Although the present embodiment is an example of an inverter circuit connected to a DC power supply, a similar effect can be obtained even when a circuit (for example, a step-up chopper circuit) for rectifying and smoothing an AC power supply is connected to this DC power supply. Needless to say.
[0033]
According to the present embodiment, the voltage stress generated in the preheating switch Q3 can be reduced with a simple and inexpensive configuration, and can be reliably suppressed within the voltage rating of the preheating switch Q3. Therefore, a switch having a lower rated voltage can be used as the preheating switch Q3 than when there is no clamp circuit. Specifically, in the present embodiment, it is possible to use an element having a voltage rating of about 500 V as preheating switch Q3. When the diode D1 is not provided, an element having a voltage rating of 800 V or more is required as the preheating switch Q3.
[0034]
(Embodiment 3)
Third Embodiment FIG. 10 shows a third embodiment of the present invention. This embodiment is an example in which the impedance element Z is inserted in series with the diode D1 in the second embodiment. The basic operation is the same as that of the second embodiment, and a duplicate description will be omitted. The difference from the second embodiment is that when an overshoot voltage is generated in the preheating switch Q3 and a clamp current flows in the diode D1, the current flows through the impedance element Z, so that a peak waveform current flowing through the diode D1 is generated. Can be suppressed by the impedance element Z, and noise caused by the clamp current of the diode D1 can be suppressed.
[0035]
Although the present embodiment is an example of an inverter circuit connected to a DC power supply, a similar effect can be obtained even when a circuit (for example, a step-up chopper circuit) for rectifying and smoothing an AC power supply is connected to this DC power supply. Needless to say.
[0036]
According to the present embodiment, the voltage stress generated in the preheating switch Q3 can be reduced with a simple and inexpensive configuration, and can be reliably suppressed within the voltage rating of the preheating switch Q3. Therefore, a switch having a lower rated voltage can be used as the preheating switch Q3 than when there is no clamp circuit. Further, generation of noise due to the clamp current of the diode D1 can be suppressed.
[0037]
(Embodiment 4)
Embodiment 4 of the present invention is shown in FIG. This embodiment is an example in which a resistor R is used as the impedance element Z inserted in series with the diode D1 in the third embodiment. The operation and effects of this embodiment are the same as those of the third embodiment.
[0038]
(Embodiment 5)
FIG. 12 shows a fifth embodiment of the present invention. This embodiment is an example in which the ferrite bead FB1 is used as the impedance element Z inserted in series with the diode D1 in the third embodiment. The operation and effects of this embodiment are the same as those of the third embodiment.
[0039]
In the present embodiment, the same effects as those of the second embodiment can be obtained, and by inserting ferrite beads FB1 having impedance characteristics corresponding to the noise frequency caused by the clamp current of diode D1, diode D1 can be effectively formed. Noise caused by the clamp current can be suppressed.
[0040]
Note that the lighting device described in Embodiments 1 to 5 may be used as a lighting device of a lighting fixture as illustrated in FIG.
[0041]
【The invention's effect】
According to the first to seventh aspects of the present invention, the voltage stress generated in the preheating switch can be reduced with a simple and inexpensive configuration, and can be reliably suppressed within the voltage rating of the preheating switch. Therefore, a switch having a lower rated voltage can be used as the preheating switch than when there is no clamp circuit. In particular, according to the fifth to seventh aspects of the present invention, when an overshoot voltage is generated in the preheating switch and a clamp current flows in the diode, the current flows through the impedance element. Current can be suppressed by the impedance element, and noise caused by the diode clamp current can be suppressed.
[Brief description of the drawings]
FIG. 1 is a circuit diagram according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a change in an operating frequency during preheating, starting, and lighting according to the first embodiment of the present invention.
FIG. 3 is a waveform diagram showing a waveform of a voltage applied to the preheating switch when the preheating switch of the first embodiment of the present invention changes from on to off.
FIG. 4 is a waveform diagram showing a waveform of a voltage applied to a preheating switch during normal lighting and when a load is removed according to the first embodiment of the present invention.
FIG. 5 is a circuit diagram according to a second embodiment of the present invention.
6A and 6B are diagrams showing a voltage waveform applied to a preheating switch at the time of normal lighting according to the second embodiment of the present invention, wherein FIG. 6A shows a case where a clamping diode is provided, and FIG. 6B shows a case where no clamping diode is provided. FIG.
FIG. 7 is a diagram showing a waveform of a voltage applied to the preheating switch when the preheating switch according to the second embodiment of the present invention changes from on to off; FIG. 4 is a waveform diagram when there is no clamping diode.
8A and 8B are diagrams showing a voltage waveform applied to a preheating switch when a load is removed when a clamping diode according to a second embodiment of the present invention is present, wherein FIG. 8A shows a waveform when the time axis is reduced, and FIG. Is a waveform diagram when the time axis is enlarged.
FIG. 9 is a diagram showing a waveform of a voltage applied to a preheating switch when a load is removed when no clamping diode is provided according to the second embodiment of the present invention. Is a waveform diagram when the time axis is enlarged.
FIG. 10 is a circuit diagram according to a third embodiment of the present invention.
FIG. 11 is a circuit diagram according to a fourth embodiment of the present invention.
FIG. 12 is a circuit diagram according to a fifth embodiment of the present invention.
FIG. 13 is a perspective view showing an external appearance of a lighting fixture using the discharge lamp lighting device of the present invention.
FIG. 14 is a circuit diagram of a conventional example.
FIG. 15 is an explanatory diagram showing a change in operating frequency at the time of preheating, starting, and lighting in the conventional example.
FIG. 16 is a waveform diagram showing a waveform of a voltage applied to the preheating switch when the preheating switch of the conventional example changes from on to off.
FIG. 17 is a waveform diagram showing a voltage waveform applied to a preheating switch during normal lighting in a conventional example.
18A and 18B are diagrams showing a waveform of a voltage applied to a preheating switch when a load is removed in a conventional example, where FIG. 18A is a waveform diagram when the time axis is reduced and FIG. 18B is a waveform diagram when the time axis is expanded. .
[Explanation of symbols]
C4 DC cut capacitor T1 Preheating transformer Q3 Preheating switch D1 Diode E1 DC power supply

Claims (7)

A hot-cathode discharge lamp having a filament, an inverter circuit for converting a DC power supply to a high frequency and supplying high-frequency power to the discharge lamp, and a filament of the discharge lamp when the inverter circuit is in a preheating / starting operation state And a preheating control circuit for preheating by supplying a filament current to the filament of the discharge lamp when in a lighting operation state, wherein the preheating control circuit includes at least a primary element of the preheating transformer element. In the discharge lamp lighting device, which is controlled to be turned off in a normal operation state of the inverter, the switch element is configured to include a series circuit of a winding and a switch element for preheating. A clamp circuit comprising at least a diode is connected to a predetermined DC power supply, and a clamp circuit constituting the clamp circuit is provided. Aether anode side is connected to the high voltage side of the switch element, the cathode side discharge lamp lighting apparatus characterized by being connected to a predetermined DC power source. 2. The DC power supply according to claim 1, wherein the predetermined DC power supply connected to the cathode side of the diode constituting the clamp circuit has a voltage lower than the rated voltage of the switch element and is equal to or higher than the DC power supply voltage of the inverter circuit. A discharge lamp lighting device, which is a voltage. 3. The discharge lamp lighting device according to claim 1, wherein the switch element is formed of a MOSFET. The discharge lamp lighting device according to any one of claims 1 to 3, wherein the predetermined DC power supply is a DC power supply voltage of an inverter. 5. The discharge lamp lighting device according to claim 1, wherein an impedance element is inserted in series with the diode of the clamp circuit. The discharge lamp lighting device according to claim 5, wherein the impedance element inserted in series with the diode is a resistor. 6. The discharge lamp lighting device according to claim 5, wherein the impedance element inserted in series with the diode is a ferrite bead.

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