JPH11135280A - Lighting device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably light a discharge lamp even at a low temperature without raising an oscillating voltage, by securing a pre-heating current at a certain level or higher even if parts used in a pre-heating circuit have some variations. SOLUTION: An inverter circuit 1 outputs a high frequency voltage V0 with an operating frequency (f) controlled by a control circuit 4, and it is applied to a resonance load circuit 2 including a discharge lamp La and a pre-heating resonance circuit 3. A level of a pre-heating current flowing from the pre-heating resonance circuit 3 to the discharge lamp La is detected by a pre-heating current detecting circuit 7, and is feedbacked to a frequency control circuit 5. While a level of a pre-heating current is detected by the pre-heating current detecting circuit 7, the operating frequency (f) of the inverter circuit 1 is controlled so that a pre-heating current at a sufficient level is supplied to the discharge lamp La by the frequency control circuit 5. Thereby, a pre-heating current at a designated level or higher can be secured (can flow), and an oscillating voltage can be suppressed low when the discharge lamp La starts even if parts used have some variations or when starting at a low temperature.

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 using an inverter circuit for converting DC power into high-frequency power and supplying it to a discharge lamp.

[0002]

2. Description of the Related Art FIG. 15 shows an example of a conventional discharge lamp lighting device using an inverter circuit 1. As shown in FIG. AC to the power supply Vs is connected to AC input terminals of the full-wave rectifier DB consisting of a diode bridge, the series circuit of the full-wave rectifier smoothing capacitor C ₀ and the switching element in the DC output terminal of the DB Q _1, Q ₂ parallel It is connected to the. Diodes D ₁ and D ₂ are connected in anti-parallel to the switching elements Q ₁ and Q ₂ , respectively.

[0003] At both ends of the switching element Q ₂ on the low potential side through the capacitor C ₃ of DC blocking, the resonance load circuit 2 and the preheating resonant circuit 3 are parallelly connected. Resonant load circuit 2 is composed of a serial resonance circuit of an inductor L ₁ and capacitor C _2, connected in parallel to the discharge lamp La across the capacitor C ₂ for resonance. The preheating resonant circuit 3 is made of a series resonant circuit of inductor L ₂ and capacitor C _4, and to supply a preheating current to the filament of the discharge lamp La from the secondary-side auxiliary winding of the inductor L _2.

In this conventional device, the switching circuit Q ₁ and Q ₂ are alternately turned on and off by the control circuit 10 to operate as a half-bridge type inverter.
High-frequency voltage is generated at the output terminal of the capacitor C ₃ of DC blocking, it is applied to the resonant load circuit 2 and the preheating resonant circuit 3. The control circuit 10 controls the operating frequency (the frequency at which the switching elements Q ₁ and Q ₂ are turned on and off) f, and drives the switching elements Q ₁ and Q ₂ under the control of the frequency control circuit 11. And a drive circuit 12.

Here, the resonance load circuit 2 and the preheat resonance circuit 3
Are independent of the high-frequency voltage, and the phases of the currents flowing through the respective resonance circuits 2 and 3 are set separately. In this conventional example, the high-frequency current flowing through the resonant load circuit 2 to which the high-frequency voltage is applied has a lag phase as compared with the high-frequency voltage, and the high-frequency current flowing through the preheating resonance circuit 3 advances with respect to the high-frequency voltage. The inductors L ₁ and L ₂ and the capacitors C ₂ and C ₄ are designed to be in phase. By doing so, the frequency of the high-frequency voltage is high at the time of preliminary preheating that requires a large amount of preheating current, so that the preheating current supplied from the preheating resonance circuit 3 is supplied more than at the steady state, and conversely, at the time of steady lighting, the sub-heat is generated. The circuit configuration enables efficient preheating such that the loss in the filament of the discharge lamp La can be reduced by suppressing the current.

The high frequency current flowing through the resonance load circuit 2 has a lagging phase, whereas the high frequency current flowing through the preheating resonance circuit 3 has a leading phase. Become. Further, the effective value of the current flowing through the switching elements Q ₁ and Q ₂ is lower than the lag phase current when only the resonance load circuit 2 is used, the switching loss is reduced, and an element having a low withstand current can be used. The size and cost of the device can be reduced.

[0007]

Meanwhile [0007], because the resonant load circuit 2 and the preheating resonant circuit 3 are each independently in the above prior art, the inductor L ₂ and capacitor C
_In the resonance characteristic of the preheat resonance circuit 3 due to the component variation of ₄ , the variation occurs regardless of the resonance load circuit 2. For example,
As shown in FIG. 16, with respect to the resonance curve of the resonance load circuit 2,
The resonance curves of the preheating current Iph with respect to the operating frequency f have variations as shown by curves A, B, and C. Where f ₂ ,
f ₁ and f ₃ are the resonance frequencies of the curves A, B and C, respectively, and are determined by f = ππ (L ₂ · C ₄ ) ^1/2 , so that the variation of the inductor L ₂ and the capacitor C ₄ causes f _Two
<F ₁ <f ₃ .

Here, _{assuming that the} inverter circuit 1 is operated at a constant operating frequency (preheating frequency) _fph determined by the control circuit 10 at the time of preheating, as shown in FIG. 16, _Iph (a) and _Iph (a), Iph _ph (b), _Iph (c) ( _Iph (b)> I
_ph (a)> _Iph (c)) and the preheating current is large or small. The magnitude of the preheating current affects the startability of the discharge lamp La, and there is a problem that the discharge lamp La is hardly lit at a low temperature under the worst condition of the variation in which the preheating current is minimized (curve C in FIG. 16). . In order to reliably turn on the discharge lamp La even under such conditions, it is conceivable to increase the starting voltage. However, if the starting voltage is set high, it is necessary to use a circuit element having a high withstand voltage, This was a factor of cost increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to always secure a preheating current of a certain level or more even if the components of a preheating circuit vary.
It is an object of the present invention to provide a discharge lamp lighting device capable of reliably lighting a discharge lamp even at a low temperature without increasing the oscillation voltage.

[0010]

According to a first aspect of the present invention, there is provided a DC power supply obtained by rectifying and smoothing an AC power supply, and one or more switching elements which are turned on / off at a high frequency. An inverter circuit that converts a DC voltage of the DC power supply into a high-frequency voltage, a resonance load circuit that has a discharge lamp, and in which a current having a delay phase with respect to the high-frequency voltage applied from the inverter circuit flows, A preheating resonance circuit in which a current having a leading phase with respect to a high frequency voltage applied from the inverter circuit flows and supplies a preheating current to a filament of the discharge lamp, and a preheating current detection circuit for detecting a preheating current level flowing in the filament of the discharge lamp And a control circuit for turning on and off the switching element to control the operating frequency of the inverter circuit. The operation frequency of the inverter circuit is controlled such that preheating is performed for a predetermined time at an operation frequency at which a preheating current level detected by the preheating current detection circuit is equal to or higher than a predetermined level during a preceding preheating period. Even if the resonance characteristics vary due to variations in components such as inductors and capacitors that make up the preheating resonance circuit, the control circuit detects the level of the preheating current with the preheating current detection circuit while controlling the discharge lamp. Since the operating frequency of the inverter circuit is controlled so that a preheating current of a level sufficient to preheat the filament is always supplied, a preheating current of a predetermined level or more can always be secured (flowed), and component variation and Oscillation voltage at the time of starting the discharge lamp can be suppressed to a low level even at a low temperature. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

According to a second aspect of the present invention, in the first aspect of the present invention, the control circuit sets an operating frequency to a first preheating frequency higher than a frequency at which the resonance frequency of the preheating resonance circuit becomes highest due to variation. To start the operation of the inverter circuit, and change the operating frequency of the inverter circuit to a second preheating frequency at which the preheating current level detected by the preheating current detection circuit exceeds the predetermined level. The operation frequency is fixed at the second preheating frequency, and the preheating is controlled so as to perform the preheating for the predetermined time. A preheating current of a predetermined level or more can always be secured (flowed). The oscillating voltage at the time of starting the discharge lamp can be suppressed to be low even at the time of starting. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

According to a third aspect of the present invention, in the first aspect of the present invention, the control circuit sets an operating frequency to a first preheating frequency lower than a frequency at which a resonance frequency of the preheating resonance circuit becomes lowest due to variation. To start the operation of the inverter circuit, and change the operating frequency of the inverter circuit to a second preheating frequency at which the preheating current level detected by the preheating current detection circuit exceeds the predetermined level. The operation frequency is fixed at the second preheating frequency, and the preheating is controlled so as to perform the preheating for the predetermined time. A preheating current equal to or higher than a predetermined level can always be secured (flowed), and component variations and low-temperature starting can be ensured. Therefore, the oscillation voltage at the time of starting the discharge lamp can be suppressed low. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the control circuit sets the operating frequency to a first preheating frequency substantially equal to a median of the variation of the resonance frequency of the preheating resonance circuit, and Start the operation of the circuit, the first
The operating frequency of the inverter circuit is set to a second preheating frequency higher or lower than the preheating frequency of the preheating current, and the preheating current level detected by the preheating current detection circuit is set to the first preheating frequency.
If the preheating current level is higher than the preheating current level during operation at the preheating frequency, the operation frequency of the inverter circuit is changed in the same direction as the change direction from the first preheating frequency to the second preheating frequency, and the preheating current detection is performed. If the preheating current level detected by the circuit is lower than the preheating current level during operation at the first preheating frequency, the inverter is reversed in the direction opposite to the direction of change from the first preheating frequency to the second preheating frequency. The operating frequency of the circuit is controlled to be changed, and the operating frequency is changed until the detected preheating current level exceeds the predetermined level. At the time when the preheating current level exceeds the predetermined level, the operating frequency of the inverter circuit is fixed and the preheating is performed for the predetermined time. It is characterized by controlling so that a preheating current of a predetermined level or more can always be secured (flowed), and the starting of the discharge lamp can be performed even in the event of component variations and low temperature starting. It is possible to suppress the oscillation voltage of the time low. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the inverter circuit includes a pair of switching elements connected between output terminals of the DC power supply and turned on and off alternately. The resonance load circuit and the preheating resonance circuit are connected in parallel to one of the switching elements, so that the switching loss in the switching element can be reduced, and the use of an element with a low current capability becomes possible, thereby reducing the size of the device. In addition, cost reduction can be realized.

According to a sixth aspect of the present invention, in the first aspect of the invention, the inverter circuit includes a series circuit of a smoothing capacitor and a series of a pair of switching elements which are connected in anti-parallel with diodes and are alternately turned on and off. A circuit and a circuit are connected in parallel between the output terminals of the DC power supply, so that a preheating current at the time of steady lighting can be suppressed and power loss in a filament of the discharge lamp can be reduced.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the inverter circuit connects a pair of switching elements in series between output terminals of the DC power supply, and the switching element on the low potential side and the DC power supply are connected. Between the output end of
And a series circuit of a second diode is inserted, and the preheat resonance circuit and the resonance load circuit are connected between a connection point of the series circuit of the first and second diodes and a connection point of the switching element. A capacitor is connected to both ends of a second diode connected to the element side, and a capacitor connected to both ends of the second diode boosts a DC input voltage from a DC power supply, thereby providing an input. Current harmonics can be kept low.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a circuit block diagram showing a first embodiment of the present invention. An AC power supply Vs is connected to an AC input terminal of a full-wave rectifier DB including a diode bridge,
The inverter circuit 1 through the capacitor C ₀ for smoothing is connected in parallel to the DC output terminals of the full-wave rectifier DB.

The inverter circuit 1 has a conventionally well-known configuration such as a half-bridge type or a full-bridge type as in the conventional example. The output terminal of the inverter circuit 1, the resonant load circuit 2 and the preheating resonant circuit 3 are connected in parallel, the high frequency voltage V ₀ which is output from the inverter circuit 1 is applied to both. The oscillation frequency (operating frequency) of the inverter circuit is controlled by the control circuit 4. The control circuit 4 controls the operating frequency by setting ON / OFF timing of one or more switching elements (not shown) included in the inverter circuit 1; A drive circuit 6 for driving the switching element of the inverter circuit 1 in response to a signal from the inverter circuit 1; and a preheating current detection circuit 7 for detecting a preheating current level flowing through the filament of the discharge lamp La. The preheating current level is detected from the current flowing through the load circuit 2 or the preheating resonance circuit 3 and is fed back to the frequency control circuit 5.

The resonance load circuit 2 has a series resonance circuit of an inductor L ₁ and a capacitor C _2. One end f ₂ and f ₄ of a filament of the discharge lamp La are connected to both ends of the capacitor C _2. 1 and the inductance value and the capacitance of the capacitor C ₂ of the inductor L ₁ so that the current I ₁ flows in the phase delayed relative to the high-frequency voltage V ₀ supplied is set from.

Meanwhile, the preheating resonant circuit 3 comprises a series resonant circuit with the inductor L ₂ and capacitor C _4, the auxiliary winding n ₁ provided in the inductor L _2, n ₂ is across f filaments each discharge lamp La ₁ is connected to ~f _4, setting the capacity of the inductance and the capacitor C ₄ of the inductor L ₂ so that the current I ₂ flows in the advanced phase relative to the high-frequency voltage V ₀ supplied from the inverter circuit 1 Have been.

[0021] In Thus, by controlling the inverter circuit 1 by applying a high frequency voltage V ₀ to the resonant load circuit 2, and the preheating resonant circuit 3 by the control circuit 4, a discharge lamp starting and sustaining the preheating of La (rated operation) Is performed. However, the preheating current I _ph supplied from the preheating resonant circuit 3 to the filament of the discharge lamp La, the part variation in the inductor L ₂ and capacitor C ₄ constituting the preheating resonant circuit 3, shown in curve A~C of FIG As described above, the resonance characteristics also vary.

Thus, in the present invention, a preheating current of a certain level or more can always be ensured for such a variation in the resonance characteristics. Next, in the present embodiment, an operation for securing (flowing) a preheating current equal to or higher than a certain value will be described.
This will be described with reference to FIGS. FIG. 2 shows a time chart of the control operation of the control circuit 4 in the present embodiment. First, when the AC power supply Vs is turned on at time t = t ₀ and the control circuit 4 starts operating, the frequency control circuit 5 determines that the resonance frequency of the preheating resonance circuit 3 is the highest due to the variation in the inductor L ₂ and the capacitor C _4. comprising a frequency (f ₃ in FIG. 3) to start the operation of the inverter circuit 1 in the first preheat frequency f _ph1 higher than.

Then, the frequency control circuit 5 calculates the time t = t
₀~ T₁The preheating current is detected by the preheating current detection circuit 7 during the period
While the preheating current is at a predetermined level as shown in FIG.
Le I _ph0The second preheating frequency f_ph2Up to invar
Gradually change the operating frequency f of the
). Here, the preheating current is at a predetermined level I_ph0The first
Preheating frequency f of 2_ph2Is an inductor as shown in FIG.
L_TwoAnd capacitor C_FourAnd represented by curve A
F_ph2(a), resonance represented by curve B
If the characteristic is f_ph2(b) The field of the resonance characteristic represented by the curve C
F_ph2(c).

The frequency control circuit 5 includes a preheating current detection circuit 7
Is detected at the predetermined level I_ph0When crossed
The operating frequency f of the inverter circuit 1 at the second preheating frequency.
Number f _ph2(a) or f_ph2(b) or f_ph2(c)
Preheating period (time t = t in FIG. 2)₁~ T_Two) Just discharge
The filament of the lamp La is preheated. And frequency control
The circuit 5 adjusts the operating frequency f to a second preheating frequency f_ph2(a)…
Starting frequency f from which the high voltage required for starting can be obtained_stNima
At time t = t_Two~ T_ThreeOnly during (startup period)
Starting frequency f_st(This operation mode is set to the start mode.
Called C. ). As a result, after the discharge lamp La is started (time
Time t = t_ThreeAfter that, the frequency control circuit 5 controls the discharge lamp La
Starting frequency f for steady lighting_stEven lower than
Frequency f_CTTo operate the inverter circuit 1 (this operation
The mode is called a steady lighting mode. ).

According to the present embodiment as described above, even when variation occurs in the resonance characteristics by the part variation in the inductor L ₂ and capacitor C ₄ constituting the preheating resonant circuit 3, the preheating current detection circuit 7 While detecting the level of the preheating current, the operating frequency f of the inverter circuit 1 is set such that the frequency control circuit 5 always supplies a preheating current of a level sufficient to preheat the filament of the discharge lamp La.
, It is possible to always secure (flow) a preheating current equal to or higher than a predetermined level, and it is possible to keep the oscillation voltage at the time of starting the discharge lamp La low even with component variations and low-temperature starting. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

(Embodiment 2) FIG. 5 is a circuit block diagram showing a second embodiment of the present invention. In this embodiment, since the basic configuration is common to the conventional example shown in FIG. 15, the common parts are denoted by the same reference numerals, and the description thereof will be omitted. Only the parts will be described.

In this embodiment, an auxiliary winding n ₃ is provided on the secondary side of the inductor L ₂ of the preheating resonance circuit 3, and a preheating current level supplied to the filament of the discharge lamp La through the auxiliary winding n ₃ is detected. A preheating current detection circuit 7 is provided in the control circuit 4. In this embodiment, the control circuit 4 including the frequency control circuit 5, the drive circuit 6, and the preheating current detection circuit 7 performs the same control operation as that of the first embodiment. The preheating current can be secured (flowed), and the oscillation voltage at the time of starting the discharge lamp La can be suppressed to a low value even when the components are scattered or the temperature is low.

The inverter circuit 1 includes diodes D ₁ , D
_2, a pair of switching elements Q ₁ ,
Series circuit Q ₂ 'are those comprising connected between the DC output ends of the full-wave rectifier DB in parallel with the smoothing capacitor C _0. Between the switching element Q _1, the connection point Q ₂ 'and full wave rectifier low potential side of the DC output ends of the DB through the capacitor C ₃ of DC blocking, the inductor L ₁ and constituting a resonant load circuit 2 A capacitor C ₂ is connected in series, and one end f ₁ , f of the filament of the discharge lamp La is connected to both ends of the capacitor C _2.
3 is connected. The inductor L ₂ and the capacitor C ₂ are connected in parallel with the switching element Q ₂ and the capacitor C _3.
Preheating resonant circuit 3 of _four series circuits are connected, an auxiliary winding n ₁ provided in the inductor L _2, n ₂ is connected to the filament ends f ₁ ~f ₄ of the discharge lamp La. Note that the inductor L ₂ auxiliary winding n ₃ for preheating current detected is provided.

Further, in the present embodiment, the high-frequency current flowing through the resonance load circuit 2 has a lagging phase as described in the conventional example, whereas the high-frequency current flowing through the preheating resonance circuit 3 has a leading phase. Since the combined current becomes a current having substantially the same phase and a high power factor, and the effective value of the current flowing through the switching elements Q ₁ and Q ₂ of the inverter circuit 1 is lower than the lagged phase current when only the resonance load circuit 2 is used. Switching loss is also reduced, and the use of an element having a low withstand current becomes possible, so that downsizing and cost reduction of the device can be realized.

(Embodiment 3) FIG. 6 is a circuit block diagram showing a third embodiment of the present invention. Note that the basic configuration of the present embodiment is the same as that of the first embodiment. As shown in FIG. 6, a series circuit of smoothing capacitors C ₁₁ and C _{12 and} a series connection of switching elements Q ₁ and Q ₂ in which diodes D ₁ and D ₂ are connected in anti-parallel to the DC output terminal of the full-wave rectifier DB. The switching elements Q ₁ and Q ₂ , diodes D ₁ and D _{2 and} smoothing capacitors C ₁₁ and C ₁₂ constitute a so-called half-bridge type inverter circuit 1 ′. .

Switching element Q₁, Q_TwoConnection point and flat
Smoothing capacitor C₁₁, C₁₂DC cut between connecting points
Capacitor C_ThreeThrough the inductor L₁, Conden
Sa C _TwoAnd a resonance constituted by a discharge lamp La such as a fluorescent lamp.
A load circuit 2 and an inductor connected in parallel with the resonance load circuit 2
Kuta L_TwoAnd capacitor C_FourPreheat resonance consisting of series circuits
The circuit 3 is connected. The preheating resonance circuit 3
Nacta L_TwoPreheat electricity to the filament of the discharge lamp La
Auxiliary winding n for supplying current₁, N_TwoAnd the control circuit 4
The preheating current level is detected by the preheating current detection circuit 7 of FIG.
Auxiliary winding n _ThreeAre provided.

The control circuit 4 controls the operating frequency f of the inverter circuit 1 by setting the ON / OFF timing of the switching elements Q ₁ and Q ₂ of the inverter circuit 1, and the frequency control circuit 5 5, the switching elements Q ₁ and Q _{2 of the} inverter circuit 1
A drive circuit 6 for driving the discharge lamp and a preheating current detecting circuit 7 for detecting a preheat current level flowing through the La filament preheating resonant circuit through the auxiliary winding n ₃ of the inductor L ₂ at the preheating current detection circuit 7 The preheating current level is detected from the current flowing through the circuit 3 and fed back to the frequency control circuit 5.

In the present embodiment, when the AC power supply Vs is turned on, the control circuit 4 causes the switching elements Q ₁ ,
Q ₂ is turned on and off alternately, and a rectangular wave high-frequency voltage is generated between the output terminals of the inverter circuit 1. This high-frequency voltage is boosted by the resonance action of the series circuit of the inductor L ₁ and the capacitor C ₂ of the resonance load circuit 2 and applied between both electrodes of the discharge lamp La, so that the discharge lamp La is turned on.

Next, a control operation from preheating to starting and lighting in this embodiment will be described with reference to FIGS. FIG. 7 shows a time chart of the control operation of the control circuit 4 in the present embodiment. First, time t =
When the AC power supply Vs is turned on at t ₀ and the control circuit 4 starts operating, the frequency control circuit 5 determines that the frequency at which the resonance frequency of the preheating resonance circuit 3 becomes the lowest due to variations in the inductor L ₂ and the capacitor C ₄ (FIG. 8). The operation of the inverter circuit 1 is started at the first preheating frequency f _ph1 lower than f ₂ ).

Then, the frequency control circuit 5 calculates the time t = t
₀~ T₁The preheating current is detected by the preheating current detection circuit 7 during the period
While the preheating current is at a predetermined level as shown in FIG.
Le I _ph0The second preheating frequency f_ph2Up to invar
Gradually change the operating frequency f of the
). Here, the preheating current is at a predetermined level I_ph0The first
Preheating frequency f of 2_ph2Is an inductor as shown in FIG.
L_TwoAnd capacitor C_FourAnd represented by curve A
F_ph2(a), resonance represented by curve B
If the characteristic is f_ph2(b) The field of the resonance characteristic represented by the curve C
F_ph2(c).

The frequency control circuit 5 includes a preheating current detection circuit 7
Is detected at the predetermined level I_ph0When crossed
The operating frequency f of the inverter circuit 1 at the second preheating frequency.
Number f _ph2(a) or f_ph2(b) or f_ph2(c)
Preheating period (time t = t in FIG. 7)₁~ T_Two) Just discharge
The filament of the lamp La is preheated. And frequency control
The circuit 5 adjusts the operating frequency f to a second preheating frequency f_ph2(a)…
Starting frequency f from which the high voltage required for starting can be obtained_stNima
At time t = t_Two~ T_ThreeOnly during (startup period)
Starting frequency f_stFixed to. As a result, the discharge lamp La starts.
(Time t = t_ThreeAfter that, the frequency control circuit 5
The starting frequency f is used to steadily light the discharge lamp La._stThan
Even lower frequency f_CTTo operate the inverter circuit 1
You.

[0037] According to this embodiment as described above, even when variation occurs in the resonance characteristics by the part variation in the inductor L ₂ and capacitor C ₄ constituting the preheating resonant circuit 3, the preheating current detection circuit 7 While detecting the level of the preheating current, the operating frequency f of the inverter circuit 1 is set such that the frequency control circuit 5 always supplies a preheating current of a level sufficient to preheat the filament of the discharge lamp La.
, It is possible to always secure (flow) a preheating current equal to or higher than a predetermined level, and it is possible to keep the oscillation voltage at the time of starting the discharge lamp La low even with component variations and low-temperature starting. As a result, it is possible to use an element having a lower tolerance compared to the conventional example, and it is possible to reduce the cost.

(Embodiment 4) FIG. 10 is a circuit block diagram showing a fourth embodiment of the present invention. In the present embodiment, the input current harmonics can be suppressed low by the inverter circuit 1 ″, and the preheating current supplied to the filament of the discharge lamp La during steady lighting (hereinafter, referred to as “always preheating current”). Although it is possible to reduce the loss in the filament by keeping it low, the basic configuration is common to the first to third embodiments. Omitted.

In this embodiment, the DC voltage obtained by full-wave rectification of the AC power supply Vs by the full-wave rectifier DB is supplied to the inverter circuit 1 ″. The inverter circuit 1 ″ is connected to the DC output terminal of the full-wave rectifier DB. capacitor C _10, the series circuit of the switching elements Q _1, Q _2, the series circuit of the full-wave rectifier negative output terminal and a diode D ₃ which is connected between the source of the switching element Q ₂ of DB, D _4, the diode D ₄ It is constituted by the capacitor C ₈ connected to both ends. Further, at both ends of the inverter circuit 1 "capacitor C ₉ is connected.

Each of the switching elements Q ₁ and Q ₂ is formed of a field effect transistor and has a parasitic diode connected in antiparallel. The switching elements Q ₁ and Q ₂ are alternately turned on by the drive circuit 6 of the control circuit 4.
It is driven off. Between the connection point of the switching elements Q ₁ and Q _{2 and} the connection point of the diodes D ₃ and D ₄ , the preheating resonance circuit 3 ″ and the resonance load circuit 2 ″ are low via a DC cut capacitor C _3. It is connected in parallel with the switching element Q ₂ potential side.

The resonance load circuit 2 ″ includes a series circuit of an inductor L ₁ and a primary winding n ₁ of a transformer T ₁ connected between a connection point of a capacitor C ₃ and diodes D ₃ and D ₄ , and a transformer T constituted by the parallel connected discharge lamp La and a parallel circuit of a capacitor C ₂ through the capacitor C ₅ of the DC cut 2 at both ends of the winding n ₂ of _1. the preheating resonant circuit 3 ", capacitor through C ₃ formed of a series circuit of switching elements Q inductor L ₂ connected to both ends of ₂ and the capacitor C _4, the inductor L ₂ for supplying the preheating current to the filament of the discharge lamp La on the secondary side Auxiliary windings n ₁ and n ₂ are provided. In the loop where the preheating current flows (one end f ₄ of the filament of the discharge lamp La).
The current transformer T to detect the preheating current level.
₂ is inserted.

On the other hand, the inductor L ₃ and the smoothing capacitor C ₀ diode D ₇ is at both ends of the switching elements to Q ₁ high potential side is connected in series, as polar through the diode D ₇ is backward diode D ₅ is connected in parallel. The diode D ₆ to the polarity across the switching element Q ₂ on the low potential side through the diode D ₇ is in the reverse direction are connected in parallel, a capacitor C ₀
Step-down chopper circuit is constituted by an inductor L ₃ and the diode D _5, D _7.

As in the _{first to} third embodiments, the control circuit 4 for controlling the switching elements Q ₁ and Q ₂ to turn on and off includes a frequency control circuit 5 for controlling the operating frequency f and the switching elements Q ₁ and Q ₂ . Drive circuit 6 for direct drive,
By detecting the preheating current level than the current transformer T ₂ composed of the preheating current detecting circuit 7 is fed back to the frequency control circuit 5.

Next, an operation for suppressing the input current harmonic in this embodiment will be described. First, when the switching element Q ₁ is turned on, the switching element Q ₂ is turned off,
Inductor from the smoothing capacitor C ₀ L ₃ → the switching element Q ₁ → capacitor C ₃ → inductor L ₁ → primary winding of the transformer T ₁ n ₁ → capacitor C ₈ → the diode D ₆
→ A resonance current flows through the path of the smoothing capacitor C _{0, and} the capacitor C ₈ is charged by the resonance current, so that the voltage Vc ₈ across the capacitor C ₈ increases.
Then, when the sum of the output voltage (DC voltage) of the full-wave rectifier DB and the voltage Vc ₈ across the capacitor C ₈ exceeds the voltage supplied to the inverter circuit 1 ″ from the smoothing capacitor C ₀ , From the power supply Vs, the full-wave rectifier DB → the switching element Q ₁ → the capacitor C ₃ → the inductor L ₁ →
Primary winding n of the transformer T _{1 1} → diode D ₃ → resonance current flows in a path of the full-wave rectifier DB → AC power source Vs, which is the input current from the full-wave rectifier DB. Since the period during which the input current flows changes substantially in proportion to the magnitude of the power supply voltage Vs, the input current becomes a sine wave in proportion to the power supply voltage Vs, and the input harmonics are suppressed low (this is referred to as the first operation mode). .).

[0045] Then, the switching element Q ₁ is off, the switching element Q ₂ is turned on, first, the inductor L
By releasing the energy stored in ₁ ,
A current flows through a path of the inductor L ₁ → the primary winding n _{1 of the} transformer T ₁ → the capacitor C ₈ → the parasitic diode of the switching element Q ₂ → the capacitor C ₃ → the inductor L ₁ , and the stored energy of the inductor L ₁ is released. Then, the DC cut capacitor C charged by the regenerative current
₃ as power supply, capacitor C ₃ → switching element Q
₂ → current flows through a path of the capacitor C ₈ → transformer T ₁ of the primary winding n ₁ → inductor L ₁ → capacitor C _3, the voltage across Vc ₈ of the capacitor C ₈ is lowered (which by the current 2 operation mode).

Subsequently, the switching element Q_TwoBut
F, switching element Q₁Turns on, the inductor L
₁By releasing the energy stored in the
Inductor L₁→ Capacitor C_Three→ Switching element Q
₁Parasitic diode → capacitor C₉→ Capacitor C₈
→ Transformer T₁Primary winding n₁→ Inductor L₁Path
Current flows through the capacitor C₈Voltage Vc₈Decreases
Keep doing. Capacitor C₈Is completely discharged,
Capacitor C₈Diode D without going through_FourCurrent through
Flows, and eventually the inductor L₁The stored energy is released
Then, the operation returns to the first operation mode (this is changed to the third operation mode).
This is called operation mode. ). In this manner, the first to third operation modes are set.
Inverter circuit 1 "receives the input current
Harmonic suppression operation and high-frequency oscillation operation.
Yes, transformer T ₁Secondary winding n_TwoRF voltage from both ends of
To turn on the discharge lamp La. Also, the preheating resonance circuit
3 "inductor L_TwoAnd capacitor C_FourDue to the resonance operation of
The inductor L_TwoAuxiliary winding n₁, N_TwoHigh on both ends of
Frequency voltage is generated, and the discharge lamp La flows through a capacitor.
The filament is supplied with a preheating current.

Next, the operation of the step-down chopper circuit will be described. First, when the switching element Q ₂ is turned on, the AC power source Vs → the full-wave rectifier DB → inductor L ₃ → smoothing capacitor C ₀ → switching element Q ₂ → diode D ₄ →
The smoothing capacitor C ₀ is charged along the path of the diode D ₃ → the full-wave rectifier DB → the AC power supply Vs, and energy is accumulated in the inductor L ₃ . Note that the capacitor C ₉
At the time of discharging, the capacitor C ₉ → the inductor L ₃ → the smoothing capacitor C ₀ → the diode D ₇ → the switching element Q
₂ → smoothing capacitor C ₀ in the path of the capacitor C ₉ is charged.

Subsequently, the switching element Q_TwoTurns off
And the inductor L_Three→ Smoothing capacitor C₀→ Diode
D₇→ Switching element Q_TwoParasitic diode →
Kuta L _ThreePath of inductor L_ThreeEnergy stored in
Lugi is released and smoothing capacitor C₀Is charged. Up
By repeating the above operation, the output of the step-down chopper circuit
Voltage is smoothing capacitor C₀Occur at both ends.

[0049] Here, in the present embodiment, the inverter circuit 1 "(switching element to Q ₁ and natural frequency f ₂ of the natural oscillation frequency f ₁ and the preheating resonant circuit 3 of the resonant load circuit 2,
The relationship of Q ₂ ) to the operating frequency f is f ₁ <f <f ₂ . That is, the resonance current of the resonance load circuit 2 has a lagging phase with respect to the high-frequency output voltage of the inverter circuit 1 ", and the resonance current of the preheating resonance circuit 3 has a leading phase with respect to the high-frequency output voltage of the inverter circuit 1". In addition, the power loss is reduced by the constant preheating current flowing through the filament of the discharge lamp La in the steady state, and the current flowing through the switching elements Q ₁ and Q ₂ is reduced by combining the leading current and the lagging current.

Next, the control operation from preheating to starting and lighting in this embodiment will be described with reference to the flowcharts of FIGS. 11 to 13 and FIG. FIG.
4 shows a time chart of the control operation of the control circuit 4 in the present embodiment. First, at time t = t ₀ , the AC power supply V
If s is the control circuit 4 is turned on to start the operation, the frequency control circuit 5, the resonance frequency of the preheating resonant circuit 3 is substantially equal to the natural vibration frequency when the substantially median variations of the inductor L ₂ and capacitor C ₄ First preheating frequency f _ph1
Starts the operation of the inverter circuit 1 ".

Then, the frequency control circuit 5 calculates the time t = t
₀ ~t performs comparison between a predetermined level I _ph0 detects the preheating current I _ph1 to preheating current detection circuit ₇₁ of the period, the preheating current I _ph1 detected exceeds a predetermined level I _ph0 (I _ph1 > I _ph0 ), preheating is performed for a predetermined time (for example, about 1 second) while the operating frequency f is fixed at the first preheating frequency f _ph1 .

On the other hand, when the detected preheating current I _ph1 is lower than the predetermined level I _ph0 (I _ph1 <I _ph0 ),
The frequency control circuit 5 determines the operating frequency f of the inverter circuit 1 ″.
A first preheat frequency from f _ph1 second preheat frequency f _ph2
To change the resonance conditions down to (f _ph1> f _ph2). Then, while operating the inverter circuit 1 ″ at the second preheating frequency f _ph2 , the preheating current I _ph2
Detects performs repeat comparison between preheating current I _ph1 when operated at the first preheat frequency f _ph1, preheating current I _ph2 is higher than the preheating current I _ph1 (I _ph2> I
_ph1 ), the operating frequency f is further _increased as shown in FIG.
The performed by repeating the comparison between a predetermined level I _ph0 while reducing, preheating current I _ph2 predetermined level I _ph0 detected
The excess (I _ph2> I _ph0) third preheat frequency f when
The operating frequency f of the inverter circuit 1 ″ is set to _ph3 , and preheating is performed for a predetermined time (for example, about 1 second).

Meanwhile, when the preheating current I _ph2 is lower than the preheating current _{I ph1 (I ph2 <I ph1} ) is comparison between a predetermined level I _ph0 while raising the inverse of the operating frequency f as shown in FIG. 13 Is repeated, and the detected preheating current I
_ph2 performs preheating of a predetermined level I exceeds _ph0 (I _ph2> I _ph0) third preheat frequency f _ph3 the inverter circuit 1 "of the operating frequency f to set a predetermined time when (e.g., about 1 second) .

Thus, the frequency control circuit 5 operates at time t = t ₀
Period ~t ₁ (preheating period) in the preheating current predetermined level I
The operating frequency f of the inverter circuit 1 ″ is set to a third preheating frequency f _ph3 exceeding _ph0, and the discharge lamp La is set for a predetermined preheating period (time t = t _{1 to} t ₂ in FIG. 11).
Preheat the filament. And the frequency control circuit 5
_Reduces the operating frequency f from the third preheating frequency f _ph3 to a starting frequency f _{st at} which a high voltage required for starting can be obtained, and the starting frequency f during the time t = t _{2 to} t ₃ (starting period). Fix to _st . As a result, after the discharge lamp La starts (after time t = t ₃ ), the frequency control circuit 5 sets the discharge lamp L
The inverter circuit 1 ″ is operated at a frequency f _CT that is lower than the starting frequency f _{st in} order to steadily light a.

[0055] According to this embodiment as described above, even when variation occurs in the resonance characteristics by the part variation in the inductor L ₂ and capacitor C ₄ constituting the preheating resonant circuit 3, the preheating current detection circuit 7 , The operating frequency f of the inverter circuit 1 ″ is controlled by the frequency control circuit 5 so that a preheating current of a level sufficient to preheat the filament of the discharge lamp La is always supplied by the frequency control circuit 5. Therefore, it is possible to always secure (flow) a preheating current equal to or higher than a predetermined level, and to suppress the oscillation voltage at the time of starting the discharge lamp La even with component variations and low-temperature starting. Therefore, an element having a lower withstand capability can be used, and the cost can be reduced.

In this embodiment, the AC power supply V
s is full-wave rectified by a full-wave rectifier DB, and there is a capacitor C ₈ inserted between the DC output voltage and the smoothing capacitor C ₀ to obtain an input current harmonic reduction effect. DC output voltage is increased. The oscillating voltage at the start of the discharge lamp La and the boost ratio of the DC output voltage are in a proportional relationship, and the DC output voltage increases as the oscillating voltage increases (the operating frequency f of the inverter circuit 1 ″ at the start decreases). However, in the present embodiment, the oscillation voltage at the time of starting the discharge lamp La can be suppressed low, and the boost of the DC output voltage of the full-wave rectifier DB can be suppressed lower than before, so that a device with a low withstand voltage can be used. Therefore, there is an advantage that cost can be reduced.

[0057]

According to the first aspect of the present invention, a DC power supply obtained by rectifying and smoothing an AC power supply is provided.
An inverter circuit including a plurality of switching elements for converting the DC voltage of the DC power supply into a high-frequency voltage; and a resonance having a discharge lamp and a current having a phase delayed with respect to the high-frequency voltage applied from the inverter circuit. A load circuit, a preheating resonance circuit in which a current having a leading phase with respect to a high frequency voltage applied from the inverter circuit flows to supply a preheating current to a filament of the discharge lamp, and a preheating current level flowing in the filament of the discharge lamp is detected. A preheating current detection circuit, and a control circuit that controls the operating frequency of the inverter circuit by turning on and off the switching element, wherein the control circuit uses the preheating current detection circuit during a preheating period when the discharge lamp is started. In order to perform preheating for a predetermined time at an operating frequency at which the detected preheating current level is equal to or higher than a predetermined level, The preheating current level is controlled by the preheating current detection circuit even if the resonance characteristics vary due to variations in the components of the preheating resonance circuit, such as inductors and capacitors. While detecting, the operating frequency of the inverter circuit is controlled so that the preheating current of a level sufficient to preheat the filament of the discharge lamp is always supplied by the control circuit, so the preheating current always exceeds a predetermined level. And the oscillation voltage at the start of the discharge lamp can be kept low even for parts variation and low temperature start.
As a result, there is an effect that an element having a lower withstand voltage can be used as compared with the conventional example, and the cost can be reduced.

According to a second aspect of the present invention, the control circuit sets an operating frequency to a first preheating frequency higher than a frequency at which the resonance frequency of the preheating resonance circuit becomes highest due to variation, and starts the operation of the inverter circuit. Changing the operating frequency of the inverter circuit to a second preheating frequency at which the preheating current level detected by the preheating current detection circuit exceeds the predetermined level, and when the preheating current level exceeds the predetermined level, the operating frequency of the inverter circuit is changed to the second preheating frequency. Since the control is performed so that the preheating is performed for the predetermined time while fixing the frequency, it is possible to always secure (flow) a preheating current of a predetermined level or more. Oscillation voltage can be kept low, and as a result, a device with lower withstand capability can be used as compared with the conventional example, and cost can be reduced. There is an effect.

According to a third aspect of the present invention, the control circuit sets an operating frequency to a first preheating frequency lower than a frequency at which the resonance frequency of the preheating resonance circuit becomes lowest due to variation, and starts the operation of the inverter circuit. Changing the operating frequency of the inverter circuit to a second preheating frequency at which the preheating current level detected by the preheating current detection circuit exceeds the predetermined level, and when the preheating current level exceeds the predetermined level, the operating frequency of the inverter circuit is changed to the second preheating frequency. Since the control is performed so that the preheating is performed for the predetermined time while fixing the frequency, it is possible to always secure (flow) a preheating current equal to or higher than a predetermined level. Oscillation voltage can be kept low, and as a result, it is possible to use an element having a lower withstand voltage as compared with the conventional example, thereby enabling cost reduction. There is a result.

According to a fourth aspect of the present invention, the control circuit sets an operating frequency to a first preheating frequency substantially equal to a median of the variation of the resonance frequency of the preheating resonance circuit to start the operation of the inverter circuit, An operating frequency of the inverter circuit is set to a second preheating frequency higher or lower than the first preheating frequency, and a preheating current level detected by the preheating current detection circuit is set to a value at the time of operation at the first preheating frequency. When the preheating current level is higher than the preheating current level, the operating frequency of the inverter circuit is changed in the same direction as the change direction from the first preheating frequency to the second preheating frequency, and the preheating current detected by the preheating current detection circuit is changed. When the level is lower than the preheating current level at the time of operation at the first preheating frequency, the inverter operates in a direction opposite to the direction of change from the first preheating frequency to the second preheating frequency. The operating frequency of the road is controlled to be changed, and the operating frequency is changed until the detected preheating current level exceeds the predetermined level. At the time when the detected preheating current level exceeds the predetermined level, the operating frequency of the inverter circuit is fixed and the preheating is performed for the predetermined time. Control, a preheating current of a predetermined level or more can always be ensured (flowed), and the oscillation voltage at the time of starting the discharge lamp can be suppressed even with respect to component variations and low temperature starting. As a result, there is an effect that an element having a lower withstand voltage can be used as compared with the conventional example, and the cost can be reduced.

According to a fifth aspect of the present invention, the inverter circuit includes a pair of switching elements connected between the output terminals of the DC power supply and alternately turned on and off, and one of the switching elements has the resonance element. Since the load circuit and the preheat resonance circuit are connected in parallel, the switching loss in the switching element can be reduced, and the use of an element having a low withstand current becomes possible, so that there is an effect that the size and cost of the device can be reduced. .

According to a sixth aspect of the present invention, the inverter circuit includes a series circuit of a smoothing capacitor and a series circuit of a pair of switching elements which are connected in reverse parallel with a diode and are alternately turned on and off. Since it is connected between the output terminals of the DC power supply, there is an effect that the preheating current at the time of steady lighting can be suppressed and the power loss in the filament of the discharge lamp can be reduced.

According to a seventh aspect of the present invention, the inverter circuit connects a pair of switching elements in series between the output terminals of the DC power supply, and connects the switching element on the low potential side and the output terminal of the DC power supply. A series circuit of first and second diodes is inserted, and the preheating resonance circuit and the resonance load circuit are connected between a connection point of the series circuit of the first and second diodes and a connection point of the switching element. And a capacitor connected between both ends of a second diode connected to the switching element side, so that a DC input voltage from a DC power supply is boosted by a capacitor connected between both ends of the second diode. There is an effect that harmonics can be suppressed low.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a first embodiment.

FIG. 2 is a time chart for explaining the above operation.

FIG. 3 is a diagram showing the resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above.

FIG. 4 is a diagram showing resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above power supply system.

FIG. 5 is a circuit block diagram showing a second embodiment.

FIG. 6 is a circuit block diagram showing a third embodiment.

FIG. 7 is a time chart for explaining the above operation.

FIG. 8 is a diagram showing resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above power supply system.

FIG. 9 is a diagram showing resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above power supply system.

FIG. 10 is a circuit block diagram showing a fourth embodiment.

FIG. 11 is a time chart for explaining the above operation.

FIG. 12 is a diagram showing the resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above.

FIG. 13 is a diagram showing resonance characteristics of the resonance load circuit and the preheating resonance circuit in the same as above.

FIG. 14 is a flowchart for explaining the above operation.

FIG. 15 is a circuit block diagram showing a conventional example.

FIG. 16 is a diagram showing the resonance characteristics of the resonance load circuit and the preheating resonance circuit in the above.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inverter circuit 2 resonance load circuit 3 preheating resonance circuit 4 control circuit 5 frequency control circuit 6 drive circuit 7 preheating current detection circuit Vs AC power supply DB full-wave rectifier

Claims (7)

[Claims] 1. A DC power supply obtained by rectifying and smoothing an AC power supply, and an inverter circuit including one or more switching elements that are turned on and off at a high frequency and converting a DC voltage of the DC power supply to a high-frequency voltage. A resonant load circuit having a discharge lamp and having a current having a phase delayed with respect to the high frequency voltage applied from the inverter circuit, and a current having a phase leading with respect to the high frequency voltage applied from the inverter circuit flowing and discharging A preheating resonance circuit for supplying a preheating current to a filament of an electric lamp, a preheating current detection circuit for detecting a level of a preheating current flowing through a filament of the discharge lamp, and an operating frequency of an inverter circuit controlled by turning on / off the switching element. A control circuit, wherein the control circuit detects a preheating current level detected by the preheating current detection circuit during a preceding preheating period when the discharge lamp is started. A discharge lamp lighting device characterized in that the operation frequency of the inverter circuit is controlled so that preheating is performed for a predetermined time at an operation frequency at which the level is equal to or higher than a predetermined level. 2. The control circuit sets an operating frequency to a first preheating frequency higher than a frequency at which a resonance frequency of the preheating resonance circuit becomes highest due to a variation, and starts an operation of the inverter circuit. The second preheating current level detected by the detection circuit exceeds the predetermined level.
The operating frequency of the inverter circuit is changed up to a preheating frequency, and when the operating frequency is exceeded, the operating frequency of the inverter circuit is fixed at a second preheating frequency, and control is performed so as to perform preheating for the predetermined time. Item 10. The discharge lamp lighting device according to Item 1. 3. The control circuit sets an operating frequency to a first preheating frequency lower than a frequency at which a resonance frequency of the preheating resonance circuit becomes lowest due to a variation, starts the operation of the inverter circuit, and starts the preheating current. The second preheating current level detected by the detection circuit exceeds the predetermined level.
The operating frequency of the inverter circuit is changed up to the preheating frequency, and when the operating frequency is exceeded, the operating frequency of the inverter circuit is fixed at the second preheating frequency, and the preheating is controlled for the predetermined time. 2. The discharge lamp lighting device according to 1. 4. The control circuit sets an operating frequency to a first preheating frequency substantially equal to a median of the variation of the resonance frequency of the preheating resonance circuit, starts the operation of the inverter circuit, and starts the first preheating frequency. The operating frequency of the inverter circuit is set to a higher or lower second preheating frequency, and the preheating current level detected by the preheating current detection circuit is higher than the preheating current level at the time of operation at the first preheating frequency. If it is higher, the operating frequency of the inverter circuit is changed in the same direction as the change direction from the first preheating frequency to the second preheating frequency, and the preheating current level detected by the preheating current detection circuit is equal to the first preheating current level. If the preheating current level is lower than the preheating current level at the time of operation at the preheating frequency, the operating frequency of the inverter circuit is changed in the direction opposite to the direction of change from the first preheating frequency to the second preheating frequency. The operating frequency is changed until the detected preheating current level exceeds the predetermined level. At the time when the preheating current level exceeds the predetermined level, the operating frequency of the inverter circuit is fixed and the preheating is performed for the predetermined time. The discharge lamp lighting device according to claim 1, wherein: 5. The inverter circuit includes a pair of switching elements connected between output terminals of the DC power supply and alternately turned on and off, and one of the switching elements includes the resonance load circuit and the preheat resonance circuit. 2. The discharge lamp lighting device according to claim 1, wherein the circuit is connected in parallel. 6. The output terminal of the DC power supply, wherein the inverter circuit includes a series circuit of a smoothing capacitor, and a series circuit of a pair of switching elements which are connected in an anti-parallel manner and are turned on and off alternately in parallel. 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is connected between them. 7. The inverter circuit, wherein a pair of switching elements are connected in series between output terminals of the DC power supply, and first and second switching elements are provided between the switching element on a low potential side and the output terminal of the DC power supply. Insert a diode series circuit of
The preheating resonance circuit and the resonance load circuit are connected between the connection point of the series circuit of the first and second diodes and the connection point of the switching element, and both ends of the second diode connected to the switching element side The discharge lamp lighting device according to claim 1, wherein a capacitor is connected to the discharge lamp.