JPH09289093A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device at low cost, which enables miniaturization of a control circuit for an inverter circuit and makes a discharge lamp easy to start at low temperatures. SOLUTION: This device comprises a dc power supply 11; a so-called separately excited type half-bridge inverter circuit INVo consisting of filter capacitors C11, C12, switching elements Q11, Q12, and diodes D11, D12; a lighting resonance circuit 15 consisting of an inductor L11, a discharge lamp La, and a capacitor C14 and connected between the output ends (a), (b) of the inverter circuit INVo via a dc cutting capacitor C13; and a preheating resonance circuit 16 consisting of a series circuit of a capacitor C15 and the primary winding n1 of a transformer T11, and the secondary windings n21, n22 of the transformer T11. The resonance frequency of the preheating resonance circuit 16 is held within the range of operating frequencies of the inverter circuit INVo.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art A first conventional example of the present invention is disclosed in Japanese Patent Laid-Open No. 296697/1986, which will be described with reference to FIGS.

This device, as shown in FIG. 1, has a voltage Vac
AC power supply Vac that outputs a DC power supply Vac and a DC power supply 11 that is a rectifier DB that full-wave rectifies the power supply voltage Vac, smoothing capacitors C11 and C12 connected in series,
It is called a switching element. ) A so-called separately-excited half-bridge inverter circuit (hereinafter, referred to as an inverter circuit) INVo that includes diodes D11 and D12 that are connected in antiparallel to Q11 and Q12 and switching elements Q11 and Q12, respectively, and an output terminal of the inverter circuit INVo. A series connection of a parallel circuit including an inductor L11, a discharge lamp La such as a fluorescent lamp, and a capacitor C14, which is connected between (a) and (b) via a DC cut capacitor (hereinafter referred to as a capacitor) C13. A resonance circuit 15 for lighting, a capacitor C15 connected in parallel to the resonance circuit 15 for lighting, a series circuit of a primary winding n1 of a transformer T11, and a secondary winding of a transformer T11 connected to a filament of a discharge lamp La. and a resonance circuit 16 for preheating composed of n21 and n22. Here, the DC power supply 11,
Inverter circuit INVo, switching elements Q11, Q
Variable resistor V for adjusting the operating frequencies of the drive circuit 12, the oscillator circuit 13, and the switching elements Q11 and Q12.
A high frequency power supply 14 is formed from R.

FIG. 4 is an operating frequency-voltage characteristic diagram showing the voltage change in each part of the circuit diagram shown in FIG. 1 with the operating frequency f of the inverter circuit INVo as the horizontal axis. here,
The frequency fo1 shown in FIG. 4 is the resonance frequency of the lighting resonance circuit 15 determined by the inductor L11 and the capacitor C14, and the frequency fo2 shown in FIG.
And the inductance L1 of the primary winding n1 of the transformer T11
It is the resonance frequency of the preheating resonance circuit 16 determined by 2 and
Each is

[0005]

[Equation 1]

[0006] The frequency f1 is the lowest operating frequency of the inverter circuit INVo, the frequency f2 is the highest operating frequency of the inverter circuit INVo,

[0007]

[Equation 2]

Is set to. Furthermore, the solid line X1 in FIG.
Indicates the change in the voltage Vc14 across the capacitor C14 when the discharge lamp La is not lit, the broken line X2 indicates the change in the voltage Vc14 across the capacitor C14 when the discharge lamp La is lit, and the alternate long and short dash line X3 indicates the transformer T11. Shows the change in the voltage V1 across the primary winding n1 of the primary winding n1.

The operation of the circuit shown in FIG. 1 will be briefly described below with reference to FIG. In this device, when the power is turned on, the drive circuit 12 and the oscillating circuit 13 alternately turn on / off the switching elements Q11 and Q12 to generate a high-frequency voltage of rectangular wave between the output terminals (a) and (b) of the inverter circuit INVo. This high-frequency voltage is boosted by the resonance action of the series circuit of the inductor L11 and the capacitor C14 of the lighting resonance circuit 15 and applied between both electrodes of the discharge lamp La, and the discharge lamp La is lit. The voltage applied between both electrodes of the discharge lamp La (hereinafter referred to as the lamp voltage) before lighting the discharge lamp La is a value on the solid line X1 shown in FIG. 4, which is determined according to the operating frequency f of the inverter circuit INVo. Will be either. When the discharge lamp La lights up, the resonance condition of the inductor L11 and the capacitor C14 is broken, and the voltage determined by the inductor L11, that is, the inverter circuit I.
The broken line X shown in FIG. 4 which is determined according to the operating frequency f of NVo
Any one of the values above 2 is applied to the discharge lamp La, and the current determined by the inductor L11 flows in the discharge lamp La. At this time, the operating frequency f of the inverter circuit INVo at the time of starting the discharge lamp La is equal to the resonance frequency fo1.
Values near are selected.

After the discharge lamp La is turned on, the variable resistor VR is adjusted to change the operating frequency f of the inverter circuit INVo from f1 to f.
When it is changed within the range of 2, the impedance of the inductor L11 changes, which changes the voltage Vc14 across the capacitor C14, that is, the lamp voltage, and the dimming control of the discharge lamp La becomes possible.

On the other hand, the voltage between the input terminals (b) and (c) of the lighting resonance circuit 15 is a constant rectangular wave voltage regardless of whether the discharge lamp La is turned on or off, and the discharge lamp La is turned on. However, the resonance condition of the capacitor C15 and the inductance L12 of the primary winding n1 of the transformer T11 is maintained, and the voltage Vn1 across the primary winding n1 of the transformer T11 is maintained.
Changes with respect to changes in the operating frequency f of the inverter circuit INVo as indicated by the alternate long and short dash line X3 in FIG. 4 regardless of whether the discharge lamp La is on or off. Also, the transformer T1
Discharge lamp La which is always preheated by n21 and n22 of 1
The preheating voltage of the filament of the inverter circuit INVo
Within the range of the operating frequency f of f1 to f2, the operating frequency f increases as the operating frequency f of the inverter circuit INVo increases. Therefore, when the operating frequency f of the inverter circuit INVo is within the range of f1 to f2, the inverter circuit INVo
As the operating frequency f of o increases, the lamp voltage decreases, and conversely, the preheating voltage of the filament of the discharge lamp La increases and the preheating current increases.

Since the preheating resonance circuit 16 preheats the discharge lamp La, and the resonance frequency fo2 is set to be higher than the maximum operating frequency f2 as shown in the above-mentioned equation 2, the discharge lamp La is set. During the rated lighting of La, the preheating current can be reduced by changing the operating frequency f of the inverter circuit INVo away from the resonance frequency fo2, and the power loss during the rated lighting of the discharge lamp La can be reduced. You can

As a second conventional example according to the present invention, there is one shown in Japanese Patent Application No. 7-190848 filed by the applicant of the present invention. Its circuit diagram is shown in FIG. 5 and its operation waveform diagram is shown in FIG.

This circuit performs full-wave rectification on an AC power supply Vac via a rectifier DB and a diode D3, converts a DC voltage smoothed by a smoothing capacitor C1 into an AC high-frequency voltage by an inverter circuit INV1, and supplies it to a discharge lamp La. Then, the discharge lamp La is turned on at a high frequency, and the rectifier DB, the impedance element Z1, the inverter circuit INV1, and the bipolar transistor (hereinafter referred to as a switching element) Q2.
A triple path resonant circuit Z3 connected in parallel to both ends of a switching element Q2 via a coupling capacitor C5 and a current path for passing an input current from an AC power supply Vac via
And a capacitor C9 and a discharge lamp La which are connected to both ends of the switching element Q2 via a coupling capacitor C5 and an inductor L2, and a preheating voltage of the discharge lamp La is supplied from the triple resonance circuit Z3. .

Here, the impedance element Z1 is composed of a capacitor C4, and the triple resonance circuit Z3 is composed of a series circuit of a primary winding n1 of a transformer T1 having secondary windings n2 and n3 and a capacitor C6. , Inductor L2
And the capacitor C9 constitute a main resonance circuit Z4, and the resonance frequency of the main resonance circuit Z4 is fo and the resonance frequency of the triple resonance circuit Z3 is 3fo. Further, the secondary winding n2 and the secondary winding n3 of the transformer T1 are respectively connected to the capacitor C7.
And the primary winding n1 of the transformer T1 which is connected to the filaments X1 and X2 of the discharge lamp La through the capacitor C8.
By supplying current to the secondary winding n of the transformer T1
The secondary voltage generated in the secondary winding n3 and the secondary winding n3 is supplied to the discharge lamp La.
As the preheating voltage of the filaments X1 and X of the discharge lamp La
Feed to 2. Further, the switching elements Q1 and Q2 are
The inverter circuit INV1 is driven by the drive circuit 1b which receives the drive signal Vd from the oscillation circuit 4, and the inverter circuit INV1 has the switching elements Q1 and Q2 connected in series and the switching element Q1.
Diodes D1 and D2, a triple resonance circuit Z3, and a main resonance circuit Z, which are connected in parallel at opposite ends of Q2 in opposite polarities.
4, a condenser C5, C7, C8, and a discharge lamp La. Furthermore, during the pre-heating of the discharge lamp La, the pre-heating signal S1 is supplied from the pre-heating circuit 5 to the oscillation circuit 4.
The drive circuit 1b, the oscillation circuit 4, and the preceding preheating circuit 5 constitute a control circuit 6 of the inverter circuit INV1. The oscillator circuit 4 and the preheating circuit 5 may have any configurations, and the drive circuit 1b may be any drive circuit that drives the switching elements Q1 and Q2. Instead of the triple resonance circuit Z3, an n-fold resonance circuit (n is Integer greater than 1).

Next, the operation of this circuit will be briefly described with reference to FIG. As shown in FIG. 6A, during the pre-heating of the discharge lamp La between times 0 and t1, the drive circuit 1b causes the inverter circuit INV1 to operate at an operating frequency f near 3fo and higher than 3fo, When the discharge lamp La is lit after the time t1, the drive circuit 1b operates the inverter circuit INV1 at an operating frequency f in the vicinity of fo and higher than fo. By operating in this way, as shown in FIG. 6C, the voltage Vc1 across the smoothing capacitor C1 is low during the pre-heating of the discharge lamp La between time 0 and t1, and the discharge lamp after time t1. It can be increased when La is lit.

That is, the inverter circuit IN with f≈3fo
When V1 is operated, most of the resonance current is triple the resonance circuit Z
3 to the main resonance circuit Z4, and as a result, as shown in FIG. 6B, the voltage VL across the discharge lamp La is increased.
The amplitude of a is greatly reduced, and the current flowing through the capacitor C4, that is, the impedance element Z1 is also significantly reduced. Therefore, the voltage Vc1 across the smoothing capacitor C1 becomes low as shown in FIG. 6C, and the amplitude of the preheating current becomes large as shown in FIG. 6D. Further, when the inverter circuit INV1 is operated with f≈fo, most of the resonance current flows to the main resonance circuit Z4 and hardly flows to the triple resonance circuit Z3.
Therefore, as shown in FIG. 6B, the amplitude of the voltage VLa across the discharge lamp La becomes large, and the current flowing through the capacitor C4, that is, the impedance element Z1 also becomes large. Therefore, the voltage Vc1 across the smoothing capacitor C1 becomes high as shown in FIG. 4C, and the amplitude of the preheating current becomes small as shown in FIG. 6D.

With this configuration, the input power factor can be improved, the input current harmonic distortion can be reduced, a large stress can be prevented from being applied, the power conversion process can be reduced, and the discharge lamp can be lit. The circuit efficiency can be improved by reducing the preheating current at the time of discharge, and the life of the discharge lamp is improved by increasing the preheating current and maintaining the undischarged state of the discharge lamp during the preheating of the discharge lamp. it can.

[0019]

However, in the first conventional example, as shown in FIG.

[0020]

(Equation 3)

Since it is set to, the preheating resonance circuit must be designed so as to supply the preheating current to the discharge lamp La in the phase advance region of the alternate long and short dash line X3. The first problem is that the shortage occurs and it becomes difficult to light the discharge lamp La.

In the second conventional example, the following second problem will occur. The resonance frequency of the triple resonance circuit Z3 is n times the resonance frequency of the main resonance circuit Z4 (n
Is an integer greater than 1), and therefore triple resonance circuit Z3
In order to set the resonance frequency of the inverter circuit INV1 and the resonance frequency of the main resonance circuit Z4 within the range of the operating frequency of the inverter circuit INV1, the maximum operating frequency of the inverter circuit INV1 must be set high. However, the control circuit 6 becomes complicated in order to prevent this, which leads to an increase in the size of the device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a discharge lamp lighting device capable of downsizing a control circuit of an inverter circuit and easily starting a discharge lamp at a low temperature. It is to provide at low cost.

[0024]

In order to solve the above problems, according to the invention of claim 1, at least one switching element, a main resonance circuit having a predetermined resonance frequency, and a main resonance circuit n times (n is an integer greater than 1)
, And an inverter circuit that converts a DC voltage into an AC high-frequency voltage and supplies it to the discharge lamp. The operating frequency of the inverter circuit is that when the discharge lamp is preheated. The resonance frequency of the n-times resonance circuit is smaller than the maximum operating frequency of the inverter circuit.

According to the second aspect of the present invention, at least one switching element, a main resonance circuit having a predetermined resonance frequency, and a resonance frequency n times (n is an integer greater than 1) the resonance frequency of the main resonance circuit. An inverter having an n-fold resonance circuit having the same, an inverter circuit for converting a DC voltage into an AC high-frequency voltage and supplying the same to a discharge lamp, and a current path for passing an input current from an AC power supply through an impedance element and a switching element. The operating frequency of the circuit is smaller when the discharge lamp is started than when it is preheated, and the resonance frequency of the n-fold resonance circuit is smaller than the maximum operation frequency of the inverter circuit.

According to the third aspect of the present invention, when the discharge lamp is preheated, the inverter circuit is oscillated at an operating frequency close to the resonance frequency of the n-fold resonance circuit, and when the discharge lamp is lit, the resonance frequency of the main resonance circuit. It is characterized in that the inverter circuit is oscillated in the vicinity.

According to the invention described in claim 4, when the discharge lamp is preheated, the inverter circuit is oscillated at an operating frequency in the vicinity of the resonance frequency of the n-fold resonance circuit and higher than the resonance frequency of the n-fold resonance circuit to discharge the discharge lamp. During lighting, the inverter circuit is oscillated at an operating frequency near the resonance frequency of the main resonance circuit and higher than the resonance frequency of the main resonance circuit.

According to the invention described in claim 5, n is a positive integer of 2 or less.

According to a sixth aspect of the invention, the AC power supply is rectified and smoothed through the rectifier and the smoothing capacitor to obtain a DC voltage.

[0030]

[Embodiment]

(Embodiment 1) The circuit diagram according to the first embodiment of the present invention is the same as that shown in FIG. 1 of the first conventional example, and is different only in its operation and operating frequency-voltage characteristic diagram. That is, the maximum operating frequency of the inverter circuit INVo is increased from the frequency f2 to the frequency f4, and the range of the operating frequency of the inverter circuit INVo is widened, which is the same as the other first conventional examples. The description is omitted by giving the same reference numerals to the configurations. An operating frequency-voltage characteristic diagram according to the present embodiment is shown in FIG.

A brief description will be given below. In the operating frequency-voltage characteristic diagram shown in FIG. 2, when the point a on the alternate long and short dash line X4 is the operating point of the resonance circuit 16 for preheating, the operating frequency f of the inverter circuit INVo in that case is the frequency as shown in FIG. It becomes f3 (however, fo2 <f3 <f4). Then, in the transition process of the discharge lamp La from the preheating mode to the starting mode, the operating point of the preheating resonance circuit 16 is the one-dot chain line X4.
It changes from the point a to the direction in which the operating frequency f of the inverter circuit INVo decreases, via the peak value on the alternate long and short dash line X4. That is, the preheating current flowing through the filament of the discharge lamp La becomes large near the peak value of the alternate long and short dash line X4,
As a result, the startability of the discharge lamp La is improved, and the low temperature startability is also improved. Here, as shown by the alternate long and short dash line X4, the resonance system of the preheating resonance circuit 16 has a finite peak value, that is, it is not a no-load resonance system, that is, the filament of the discharge lamp La has a finite impedance value. Because.

Further, in particular, by setting the resonance frequency fo2 to 1 to 2 times the resonance frequency fo1, the frequency f4
Can be made small, that is, the inverter circuit INV
The range of change of the operating frequency f of o can be narrowed,
Therefore, the range of change in the value of the variable resistor VR shown in the circuit diagram of FIG. 1 can be reduced, and thus the inverter circuit I
The rate of change in the value of the variable resistor VR with respect to the change in the operating frequency f of NVo can be set arbitrarily, and thus the operating frequency f of the arbitrary inverter circuit INVo can be easily set.

(Second Embodiment) FIG. 3 shows a circuit diagram of a second embodiment according to the present invention.

This circuit can suppress the input current harmonics to a low level by the inverter circuit INV2, and can supply a sufficient preheating current to the filament of the discharge lamp La, especially at low temperature starting.

First, the circuit configuration will be described below with reference to FIG. The DC voltage VDB obtained by full-wave rectifying the AC power supply Vac by the rectifier DB is supplied to the inverter circuit INV2.

The inverter circuit INV2 has bipolar transistors (hereinafter referred to as switching elements) Q21 and Q22 connected in parallel to the output terminal of the rectifier DB in series, and the polarities of the switching elements Q21 and Q22 are opposite to each other. Connected in parallel to each other in a direction, series connection of diodes D21 and D22 connected between the negative output terminal of the rectifier DB and the anode side terminal of the diode D24, and parallel connection to both ends of the diode D22. Capacitor C24 and diode D
23, D24 and the contacts of diodes D21, D22, and a series connection composed of a DC-cutting capacitor C25 and a primary winding n1 of a transformer T21. A capacitor C28 is connected to both ends of the inverter circuit INV2. Then, the drive circuit 21 alternately turns on and off the switching elements Q21 and Q22.

A series connection consisting of an inductor L22, a smoothing capacitor C27, and a diode D25 connected in parallel to both ends of the switching element Q21, and a diode D25 connected in parallel to both ends of the switching element Q22 so that their polarities are opposite to each other. The diode D26, the switching element Q22, and the diode D24 form a step-down chopper circuit. In this way, switching element Q22
Is used as both the inverter circuit INV2 and the step-down chopper circuit. A series connection including an inductor L21 and a discharge lamp La connected in parallel to both ends of the secondary winding n2 of the transformer T21, and a parallel connection between both ends of the discharge lamp La and a terminal of the transformer T21 on the secondary winding n2 side. Capacitor C2
1 forms a load circuit, the primary winding n1 of the transformer T21 and the capacitor C24 form a resonance circuit, and the inductor L21, the capacitor C21, and the discharge lamp La form a main resonance circuit. Further, a series connection composed of a primary winding n1 of a transformer T22 and a capacitor C26 connected to both ends of a diode D24 via a DC cutting capacitor C25 and a transformer connected in parallel to both ends of both filaments of the discharge lamp La. Secondary winding n21 of T22,
Series connection of capacitor C22 and transformer T22 2
The secondary winding n22 and the capacitor C23 are connected in series to form a preheating circuit for the discharge lamp La. Here, the primary winding n1 of the transformer T22 and the capacitor C26 constitute a preheating resonance circuit.

Next, the operation of suppressing the input current harmonics in this circuit will be described. (1) First, when the switching element Q21 is turned on, the smoothing capacitor C27 → inductor L22 → switching element Q21 → DC cutting capacitor C25 → transformer T
21 primary winding n1 → capacitor C24 → diode D
A current flows through the resonance circuit through the route of 26 → smoothing capacitor C27, and this current charges the capacitor C24, and the voltage Vc24 across the capacitor C24 rises. Then, the output voltage VDB of the rectifier DB and the capacitor C24
The voltage that is the sum of the voltage Vc24 across
From the moment when the voltage supplied from 27 to the inverter circuit INV2 is exceeded, AC power supply Vac → rectifier DB → switching element Q21 → DC cutting capacitor C25 → primary winding n1 of transformer T21 → diode D21 → rectifier DB → AC power supply A current also flows through the resonance circuit in the Vac path, and this becomes the input current from the rectifier DB. Since the period during which the input current flows changes substantially in proportion to the magnitude of the power supply voltage Vac, the input current has a sine wave shape proportional to the power supply voltage Vac, and the input current harmonics can be suppressed low.

(2) Next, when the switching element Q21 is turned off and the switching element Q22 is turned on, the transformer T2 is initially driven by the regeneration mode of the inverter circuit INV2.
1 primary winding n1 → capacitor C24 → diode D2
4 → DC cutting capacitor C25 → Current flows in the path of the primary winding n1 of the transformer T21, and then reverses, and the DC cutting capacitor C25 is used as a power source, and the DC cutting capacitor C25 → Switching element Q22 → Capacitor C24 → Transformer A current flows through the path from the primary winding n1 of T21 to the DC-cutting capacitor C25, and this current causes the voltage Vc24 across the capacitor C24 to decrease.

(3) Next, when the switching element Q22 is turned off, the regeneration mode of the inverter circuit INV2 is set for a while, and the primary winding n1 of the transformer T21 → DC cut capacitor C25 → diode D23 → capacitor C.
28 → capacitor C24 → primary winding n of transformer T21
The current flows through the route of 1, and the voltage V across the capacitor C24
c24 continues to decline. When the electric charge of the capacitor C24 is completely discharged, a current flows through the diode D22 instead of passing through the capacitor C24. Eventually, the current is reversed and the operation shown in the drive circuit 1 is restored.

By repeating such an operation, the inverter circuit INVo performs the harmonic suppression operation of the input current, and
Performs high frequency oscillating operation and turns the secondary winding n2 of the transformer T21.
A high-frequency voltage is generated across both ends of the discharge lamp La, and the discharge lamp La is lit via the main resonance circuit including the inductor L21, the capacitor C21, and the discharge lamp La. Further, the primary winding n1 of the transformer T22 and the capacitor C26 allow the transformer T2 to
A high frequency voltage is generated across both ends of the secondary windings n21 and n22 of the second winding 2, and a preheating current can be supplied to the filament of the discharge lamp La through the capacitors C22 and C23.

The operation of the step-down chopper circuit will be described. (1) First, when the switching element Q22 is turned on, the AC power supply Vac → rectifier DB → inductor L22 → smoothing capacitor C27 → switching element Q22 → diode D.
The smoothing capacitor C27 is charged along the path of 22 → diode D1 → rectifier DB → AC power supply Vac, and energy is stored in the inductor L22. In the discharging mode of the capacitor C24, the capacitor C28 → inductor L22 → smoothing capacitor C27 → diode D
The smoothing capacitor C27 is charged along the path of 25 → switching element Q22 → capacitor C28.

(2) When the switching element Q22 is turned off, the energy accumulated in the inductor L22 moves to the smoothing capacitor C27 along the path of the inductor L22 → the smoothing capacitor C27 → the diode D25 → the diode D23 → the inductor L22.

By repeating such operation, the output voltage of the step-down chopper circuit is generated across the smoothing capacitor C27. Here, the range of the operating frequency f of the inverter circuit INV2, the resonance frequency of the main resonance circuit, and the resonance circuit for preheating. By setting the relationship with the resonance frequency as shown in the operating frequency-voltage characteristic diagram shown in FIG. 2, as in the first embodiment,
The preheating current flowing through the filament of the discharge lamp La increases near the peak value of the alternate long and short dash line X4 shown in FIG. 2, and as a result, the startability of the discharge lamp La is improved and the low temperature startability is also improved. Furthermore, the maximum operating frequency of the inverter circuit INV2 can be reduced by setting the resonant frequency of the preheating resonant circuit to be 1 to 2 times the resonant frequency of the main resonant circuit, that is, the operating frequency of any inverter circuit INV2. f can be easily set.

In the above embodiment, instead of the step-down chopper circuit, a partial smoothing circuit, a complete smoothing circuit, another chopper circuit, or a power supply circuit having another configuration may be used, and a transformer T21 is provided. Instead, the load circuit may be provided. Further, in all the above-described embodiments, for example, a self-excited half-bridge inverter circuit or another type of inverter circuit may be used instead of the separately-excited half-bridge inverter circuit.

[0046]

According to the first aspect of the present invention, it is possible to provide a discharge lamp lighting device in which the control circuit of the inverter circuit can be downsized and the discharge lamp can be easily started at a low temperature at low cost.

According to the second or sixth aspect of the present invention, the control circuit of the inverter circuit can be downsized, the discharge lamp can be easily started at low temperature, the input power factor can be improved, and the input current can be improved. A discharge lamp lighting device capable of reducing harmonic distortion can be provided at low cost.

According to the third and fourth aspects of the present invention, the control circuit of the inverter circuit can be miniaturized, the discharge lamp can be easily started at a low temperature, and a large stress is prevented from being applied. It is possible, the circuit efficiency can be improved by reducing the power conversion process and reducing the preheating current when the discharge lamp is lit, and at the time of preheating the discharge lamp,
A discharge lamp lighting device capable of improving the life of the discharge lamp by increasing the preheating current and maintaining the undischarged state of the discharge lamp can be provided at low cost.

According to the fifth aspect of the present invention, the control circuit of the inverter circuit can be downsized, the discharge lamp can be easily started at a low temperature, and the range of change in the operating frequency of the inverter circuit can be narrowed. Therefore, the discharge lamp lighting device capable of easily setting the operating frequency of any inverter circuit can be provided at low cost.

[Brief description of drawings]

FIG. 1 shows circuit diagrams of a first embodiment and a first conventional example according to the present invention.

FIG. 2 shows an operating frequency-voltage characteristic diagram according to the first embodiment.

FIG. 3 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 4 shows an operating frequency-voltage characteristic diagram according to the first conventional example.

FIG. 5 shows a circuit diagram of a second conventional example according to the present invention.

FIG. 6 shows an operation waveform diagram according to the second conventional example.

[Explanation of symbols]

 C capacitor DB rectifier f frequency INV inverter circuit La discharge lamp Q switching element Vac AC power supply

Claims (6)

[Claims] 1. At least one switching element,
A main resonance circuit having a predetermined resonance frequency, an n times resonance circuit having a resonance frequency n times that of the main resonance circuit (n is an integer greater than 1), and a discharge lamp that converts a DC voltage into an AC high frequency voltage. In the discharge lamp lighting device, the operating frequency at the time of starting the discharge lamp is smaller than the operating frequency at the time of preheating of the discharge lamp. A discharge lamp lighting device, wherein a resonance frequency is lower than a maximum operating frequency of the inverter circuit. 2. At least one switching element,
A main resonance circuit having a predetermined resonance frequency, an n times resonance circuit having a resonance frequency n times that of the main resonance circuit (n is an integer greater than 1), and a discharge lamp that converts a DC voltage into an AC high frequency voltage. An inverter circuit for supplying an input current from an AC power source via an impedance element and the switching element, and the inverter circuit is configured so that the operating frequency at the time of starting the discharge lamp is the discharge lamp. In the discharge lamp lighting device having an operating frequency lower than that during preheating, the resonance frequency of the n-fold resonance circuit is lower than the maximum operating frequency of the inverter circuit. 3. The inverter circuit oscillates at an operating frequency near the resonance frequency of the n-fold resonance circuit when the discharge lamp is preheated, and near the resonance frequency of the main resonance circuit when the discharge lamp is lit. 3. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is oscillated. 4. The inverter circuit oscillates at an operating frequency near the resonance frequency of the n-fold resonance circuit and higher than the resonance frequency of the n-fold resonance circuit when the discharge lamp is preheated. 3. The discharge lamp lighting device according to claim 1 or 2, wherein at the time of lighting, an oscillating operation is performed near the resonance frequency of the main resonance circuit and at an operating frequency higher than the resonance frequency of the main resonance circuit. 5. The discharge lamp lighting device according to claim 1, wherein the n is a positive integer of 2 or less. 6. The discharge lamp lighting device according to claim 1, wherein the DC voltage is obtained by rectifying and smoothing an AC power source through a rectifier and a smoothing capacitor.