JP2008287979A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of uniformly controlling currents flowing in a plurality of discharge lamps in spite of a simple and inexpensive circuit structure. <P>SOLUTION: The discharge lamp lighting device 10 is provided with a coupled inductor 20 consisting of inductors L1a, L1b magnetically coupled with each other. The inductor L1a is connected in series between one end at a secondary side of a step-up transformer T1 and one end of the discharge lamp Lp1a, the inductor L1b is connected in series between the other end at a secondary side of the step-up transformer T1 and one end of the discharge lamp (a straight tube) Lp1b, and the other end each of the discharge lamp Lp1a and the discharge lamp Lp1b are connected with each other to structure quasi U-shaped tubes (Lp1a, Lp1b) in a floating state. Further, a constant-current power source is structured by serial resonance of inductances possessed by each inductor L1a, Lib and parasitic capacitances Cp1a, Cp1b possessed by the discharge lamps Lp1a, Lp1b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device that drives a plurality of discharge lamps.

  Conventionally, a discharge lamp lighting device has mainly used a method of lighting one discharge lamp with one inverter. However, with the increase in the number of discharge lamps and the price of discharge lamp lighting devices, it has become desirable to simplify and reduce the price of inverters, and there are various methods for driving a plurality of discharge lamps with a single inverter. Proposed.

  As an example of this type of discharge lamp lighting device, FIG. 9 shows a discharge lamp lighting device that drives a discharge lamp in a floating state by applying a differential voltage to both ends of the discharge lamp. In the discharge lamp lighting device 100 shown in FIG. 9, an AC voltage source Vac and output transformers Ta1 to Tan form an inverter, and primary sides of the inverter output transformers Ta1 to Tan are connected in series. In addition, one end of a plurality of discharge lamps Lp101 to Lp10n is connected to one end on the secondary side of the output transformers Ta1 to Tan, and the other end on the secondary side of the output transformers Ta1 to Tan is grounded. The other ends of the plurality of discharge lamps Lp101 to Lp10n are connected and connected to the power transformer To. In general, parasitic capacitances Cp101 to Cp10n exist between the discharge lamps Lp101 to Lp10n and the housing.

  Since the discharge lamp lighting device 100 configured in this way is connected to the other ends of the plurality of discharge lamps Lp101 to Lp10n and driven by a common power transformer To, the other ends of the plurality of discharge lamps Lp101 to Lp10n are connected. Compared to the system driven by individual output transformers, the number of output transformers can be reduced. At the same time, the primary side of the output transformers Ta1 to Tan is connected in series, so it depends on the impedance variation of each discharge lamp. Driving is possible, and the uniformity of the current flowing through each discharge lamp is maintained.

  However, in the discharge lamp lighting device 100, only the other ends of the plurality of discharge lamps Lp101 to Lp10n are driven by a common power transformer To, and at least the same number of output transformers Ta1 to Tan as one discharge lamp and one The power transformer To is necessary, and there is room for improvement for simplification and lowering the price.

  As a method of driving a plurality of discharge lamps with one output transformer, one end of a plurality of discharge lamps is connected to one end on the secondary side of the output transformer, and a current transformer (current detection transformer) is connected to the other end of each discharge lamp. ) Secondary windings, a series circuit of multiple discharge lamps and current transformers is connected in parallel to the secondary winding of the output transformer, and the primary windings of each current transformer are connected in series. Thus, a discharge lamp lighting circuit in which a closed loop is formed has been proposed (see, for example, Patent Document 1). In the discharge lamp lighting device described in Patent Document 1, the current flowing through each discharge lamp is balanced by the mutual induction action of the current transformers.

JP 2006-12659 A

  However, in the discharge lamp lighting device disclosed in Patent Document 1, it is necessary to use a large number of current transformers in proportion to the number of discharge lamps. As a result, in addition to not leading to a reduction in price, There is a problem in that the reliability decreases due to the large number of parts.

  The present invention has been made in view of the above problems, and provides a discharge lamp lighting device capable of uniformly controlling the current flowing through a plurality of discharge lamps while having a simple and inexpensive circuit configuration. Objective.

In the following, some aspects of the invention that can be claimed in the present application (hereinafter referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections.
In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiment, etc., and as long as the interpretation is followed, another aspect is added to the aspect of each section. Moreover, the aspect which deleted the component from the aspect of each term can also be one aspect of the claimable invention. In each of the following items, (1) is in claim 1, (3) is in claim 2, (6) is in claim 3, (7) is in claim 4, (8) ) Corresponds to claim 5, (9) corresponds to claim 6, (10) corresponds to claim 7, and (11) corresponds to claim 8.

(1) In a discharge lamp lighting device that includes an inverter that converts a DC voltage into an AC voltage and a transformer that forms part of the inverter, and that drives at least one discharge lamp, a plurality of magnetically coupled devices A coupled inductor comprising an inductor, wherein one of the plurality of inductors is connected in series between one end connected to the output end of the transformer of the discharge lamp and the output end; A discharge lamp lighting device comprising a constant current source by series resonance of an inductance of the inductor and a parasitic capacitance of the discharge lamp to which the inductor is connected.

  The discharge lamp lighting device of this section has a coupled inductor composed of a plurality of inductors magnetically coupled to each other, and the inductance of each inductor is connected in series with the parasitic capacitance of the discharge lamp to which the inductor is connected. Due to the resonance, a constant current source is configured in which the current value does not depend on the impedance at the stage after each inductor, so that it is possible to effectively eliminate the variation in current caused by the variation in impedance of each discharge lamp. It becomes possible to uniformly control the current flowing through the lamp.

(2) In the discharge lamp lighting device according to (1), preferably, the coupled inductor is formed by winding a plurality of windings respectively constituting the plurality of inductors around one common core. It is.
According to the discharge lamp lighting device of this section, it is possible to realize a simpler and cheaper circuit configuration than the circuit configuration using a plurality of independent inductors, and to uniformly control the current flowing through the discharge lamp.

(3) In the discharge lamp lighting device according to (1) to (2), at least one of the discharge lamps has one of the plurality of inductors connected to both ends of the discharge lamp, and one end of the discharge lamp. And the inductor connected to the other end of the discharge lamp is connected to the other output end of the transformer and connected in a floating state. A discharge lamp lighting device characterized by that.

(4) In the discharge lamp lighting device according to item (3), preferably, each of the plurality of discharge lamps has one of the plurality of inductors connected to both ends of the respective discharge lamp, The inductor connected to one end of the discharge lamp is connected to one output end of the transformer, and the inductor connected to the other end of each discharge lamp is connected to the other output end of the transformer It is.

(5) In the discharge lamp lighting device according to (1) to (2), each of the plurality of discharge lamps has one of the plurality of inductors connected to one end of each of the discharge lamps. The inductor connected to one end of the discharge lamp is connected to one output end of the transformer, and the other end of each discharge lamp and the other output end of the transformer are grounded. Discharge lamp lighting device.

(6) In the discharge lamp lighting device according to (1) to (5), a ballast element is connected in series between the output end of the transformer and the inductor connected to the output end. Discharge lamp lighting device.

(7) The discharge lamp lighting device according to any one of (1) to (5), wherein a ballast element is provided on the input side of the transformer.

(8) The discharge lamp lighting device according to any one of (6) to (7), wherein the ballast element includes at least one of a choke coil, a capacitor, and a leakage inductance of the transformer. .

(9) The discharge lamp lighting device according to any one of (1) to (8), characterized in that a parallel resonant circuit is configured by the self-inductance of the transformer and at least one parasitic capacitance or auxiliary capacitance of the discharge lamp. Discharge lamp lighting device.

(10) The discharge lamp lighting device according to any one of (1) to (9), wherein the discharge lamp lighting device is incorporated in a backlight device for a liquid crystal display device.

(11) The discharge lamp lighting device according to any one of (1) to (10), wherein at least one of the discharge lamps is a straight tube, a U-shaped tube, a pseudo U-shaped tube, or a U-shaped tube. Discharge lamp lighting device.

  Since the present invention is configured as described above, it is possible to provide a discharge lamp lighting device capable of uniformly controlling the current flowing through a plurality of discharge lamps while having a simple and inexpensive circuit configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a diagram showing a circuit configuration of a discharge lamp lighting device 10 according to the first embodiment of the present invention. The discharge lamp lighting device 10 includes an inverter 15 that converts a DC voltage into an AC voltage and boosts the voltage using a bridge circuit (not shown). The inverter 15 shown in FIG. The output is schematically shown as an AC voltage source Vac. The inverter 15 includes a step-up transformer T1, and the AC voltage source Vac is connected to both ends on the primary side of the step-up transformer T1. The discharge lamp lighting device 10 further includes two inductors L1a and L1b that are magnetically coupled to each other, and one end (one output end) on the secondary side of the step-up transformer T1 and a discharge lamp (directly connected). The inductor L1a is connected in series between one end of the tube Lp1a and the inductor is connected between the other end (the other output end) on the secondary side of the step-up transformer T1 and one end of the discharge lamp (straight tube) Lp1b. L1b is connected in series. The other ends of the discharge lamp Lp1a and the discharge lamp Lp1b are connected to form one pseudo U-tube (Lp1a, Lp1b). The discharge lamp lighting device 10 has both ends connected via inductors L1a and L1b. It is configured to drive one pseudo U-shaped tube (Lp1a, Lp1b) connected to both ends of the step-up transformer T1 and connected in a floating state. The midpoint of the secondary side of the step-up transformer T1 is grounded, and each of the discharge lamps Lp1a and Lp1b has parasitic capacitances Cp1a and Cp1b between other components of the discharge lamp lighting device 10 such as a housing. have.

  Here, the coupled inductor 20 is formed by winding the windings constituting the inductors L1a and L1b around one common core, and the inductance of the inductor L1a and the parasitic capacitance Cp1a of the discharge lamp Lp1a. Each circuit constant is set so as to satisfy the series resonance condition of the above and the series resonance condition of the inductance of the inductor L1b and the parasitic capacitance Cp1b of the discharge lamp Lp1b. Here, since the capacitance values of the parasitic capacitances Cp1a and Cp1b are approximate, the number of windings constituting each inductor may generally be the same, but the number of windings constituting each inductor is individually set. By setting, the series resonance point can be finely adjusted and optimized.

Next, the operation of the discharge lamp lighting device 10 will be described with reference to FIG.
FIG. 2 is a principle circuit diagram in which the circuit configuration diagram of FIG. 1 is equivalently replaced. However, the two voltage sources Vac2 shown on the left and right are the same high-frequency schematically showing the voltage appearing at both ends on the secondary side of the step-up transformer T1 after the step-up conversion of the voltage of the AC voltage source Vac by the step-up transformer T1. It is a voltage source. Further, the positive and negative symbols of the voltage source Vac2 indicate that the two voltage sources Vac2 are in opposite phases to each other, and the pseudo U-shaped tube including the two discharge lamps Lp1a and Lp1b is a high-voltage differential drive (hereinafter also referred to as a floating drive). Represents that

  In the discharge lamp lighting device 10, when the voltage source Vac2 is in a positive half cycle (that is, the phase of the left and right voltage sources Vac2 in FIG. 2 is represented by the positive and negative symbols in FIG. 2), the current is L1a In the order of Lp1a → Lp1b → L1b → Vac2, and in the negative half cycle (that is, the state where the left and right voltage sources Vac2 shown in FIG. 2 are in the opposite phase to the positive and negative symbols shown in FIG. 2) It follows the reverse path and flows in the order L1b → Lp1b → Lp1a → L1a → Vac2.

  Here, in the discharge lamp lighting device 10, the circuit constant is set so that the inductance of the inductor L1a constituting the coupled inductor 20 and the parasitic capacitance Cp1a of the discharge lamp Lp1a satisfy the series resonance condition. A constant current source whose current value does not depend on the impedance of the latter stage of the inductor L1a is configured. Similarly, since the capacitance values of the parasitic capacitances Cp1a and Cp1b are approximate, another inductor L1b that constitutes the coupled inductor 20 also constitutes the inductor L1a with the number of windings constituting the inductor L1b. Since the circuit constant is set so that the number of turns of the winding is equal and the inductance of the inductor L1b and the parasitic capacitance Cp1b of the discharge lamp Lp1b satisfy the series resonance condition, the current value is set to the impedance of the latter stage of the inductor L1b. A constant current source that does not depend on is configured.

This principle will be described with reference to FIG.
FIG. 3A is a circuit diagram for explaining a series resonance condition between an arbitrary inductor (L1a or L1b) of the coupled inductor 20 and a parasitic capacitance (Cp1a or Cp1b) of a discharge lamp connected thereto. b) shows a vector diagram thereof. 3A, assuming that the impedance of an arbitrary inductor of the coupled inductor 20 is jωL and the parasitic capacitance is Cp, the series resonance condition is satisfied under the condition of ωL = 1 / ωCp, and the load impedance Z ^* (FIG. 3 corresponds to the symbol Z with “•” in 3. The same applies to the other symbols below), and the current I ^* flowing is I ^* = Vac ^* / jωL. That is, the current flowing through the load impedance Z ^* is independent of the load impedance Z ^* and the parasitic capacitance Cp, so that the constant current source is configured. Further, in the vector diagram of FIG. 3B, when the voltage source Vac ^* is taken as a reference, the current I ^* flowing through the load impedance Z ^* is delayed by 90 ° from the voltage source Vac ^* , and the current Icp flowing through the parasitic capacitance is obtained. ^* Is a phase advance of 90 ° from the current I ^* flowing through the impedance Z ^* .

  As described above, in the discharge lamp lighting device 10, the inductances of the inductors L1a and L1b constituting the coupled inductor 20 and the parasitic capacitances Cp1a and Cp1b of the discharge lamps Lp1a and Lp1b connected in series to the inductors L1a and L1b are ω = By setting circuit constants so as to satisfy the series resonance condition at 2πf (f is the AC frequency of the AC voltage source Vac), a constant current source whose current value does not depend on the impedance of the subsequent stage of each inductor L1a and L1b is configured. This makes it possible to eliminate variations in current caused by variations in the impedance of each discharge lamp while maintaining a simple and inexpensive circuit configuration, and to uniformly control the current flowing through the discharge lamp. It becomes possible to do.

  In the present embodiment, the discharge lamp driven by the discharge lamp lighting device 10 is composed of a pseudo U-tube that connects one end of the discharge lamp Lp1a and one end of the discharge lamp Lp1b. Instead of the U-shaped tube, it may be configured by a discharge lamp having another shape such as a single straight tube, a U-shaped tube, or a U-shaped tube.

(Second Embodiment)
FIG. 4 is a diagram showing a circuit configuration of a discharge lamp lighting device 10a according to the second embodiment of the present invention. In FIG. 4, the same reference numerals are given to components common to FIG. 1.

  The discharge lamp lighting device 10a includes an inverter 15 similar to the discharge lamp lighting device 10 and a step-up transformer T1 that is a component thereof. The discharge lamp lighting device 10b further includes n (n> 2) inductors L1a to Lnb magnetically coupled to each other, and one end (one output end) on the secondary side of the step-up transformer T1. Inductors L1a to Lna are connected in series between one end of each of the discharge lamps (straight pipes) Lp1a to Lpna, respectively, and the other end (the other output end) on the secondary side of the step-up transformer T1 and the discharge lamp (straight pipe). Tube) Inductors L1b to Lnb are connected in series between one ends of Lp1b to Lpnb, respectively. The other ends of the discharge lamp Lp1a and the discharge lamp Lp1b are connected to each other, and similarly, the other ends of the discharge lamps Lp2a,..., Lpna are connected to the other ends of Lp2b,. n pseudo U-shaped tubes (Lp1a, Lp1b) to (Lpna, Lpnb) are configured.

  In this way, the discharge lamp lighting device 10a has both ends of the pseudo U-shaped tube (Lpia, Lpib) (i = 1 to n) connected to both ends of the step-up transformer T1 via the inductors Lia and Lib (i = 1 to n). A plurality of discharge lamps (pseudo U-shaped tubes) connected to each other and connected in parallel to the output side on the secondary side of the step-up transformer T1 are driven by one step-up transformer T1. It has a configuration. Also in the present lamp lighting device 10a, the midpoint of the secondary side of the step-up transformer T1 is grounded, and the discharge lamps Lp1a to Lpna and Lp1b to Lpnb are, for example, of the discharge lamp lighting device 10 such as a housing. Parasitic capacitances Cp1a to Cpna and Cp1b to Cpnb are respectively provided between other components.

  In the discharge lamp lighting device 10a, the coupled inductor 20a is formed by winding windings constituting the inductors L1a to Lna and L1b to Lnb around one common core, and the inductors L1a to Lna and L1b to Since the Lnbs are magnetically coupled to each other, the currents flowing through the windings constituting the inductors L1a to Lna and L1b to Lnb are balanced. Further, in the present embodiment, the inductances of the inductors L1a to Lna and L1b to Lnb and the parasitic capacitances of the discharge lamps Lp1a to Lpna and Lp1b to Lpnb in which the inductors L1a to Lna and L1b to Lnb are connected in series. The circuit constants are set so that Cp1a to Cpna and Cp1b to Cpnb satisfy the series resonance conditions, respectively. Similarly to the discharge lamp lighting device 10, the impedances of the subsequent stages of the inductors L1a to Lna and L1b to Lnb A constant current source whose current value does not depend on the current value is configured.

  FIG. 5 is a principle circuit diagram in which the circuit configuration diagram of FIG. 4 is equivalently replaced. Each symbol corresponds to FIG. 4, and the same components as those in FIG. In the discharge lamp lighting device 10a, when the voltage source Vac2 is in a positive half cycle (that is, the phase of the left and right voltage sources Vac2 in FIG. 5 is represented by the positive and negative symbols in FIG. 5), the current is Lia → Lpia → Lpib → Lib → Vac2 (i = 1 to n) in this order, and the negative half cycle (that is, the left and right voltage sources Vac2 shown in FIG. 5 have phases opposite to the positive and negative symbols shown in FIG. In this state, the reverse path is followed, and flows in the order of Lib → Lpib → Lpia → Lia → Vac2 (i = 1 to n).

  Although the discharge lamp lighting device 10a configured as described above has a simple and inexpensive circuit configuration, it can eliminate the current variation caused by the impedance variation of each discharge lamp, and the step-up transformer T1. The current flowing through the plurality of discharge lamps connected in parallel to the output terminal can be uniformly controlled.

  Also in this embodiment, each discharge lamp driven by the discharge lamp lighting device 10a has another shape such as a single straight tube, a U-shaped tube, or a U-shaped tube instead of a pseudo U-shaped tube. You may comprise with a discharge lamp.

(Third embodiment)
FIG. 6 is a diagram showing a circuit configuration of a discharge lamp lighting device 10b according to the third embodiment of the present invention. In FIG. 6, the same reference numerals are given to the components common to FIG.

  The discharge lamp lighting device 10b includes an inverter 15 similar to the discharge lamp lighting device 10 and a step-up transformer T1 that is a component thereof. The discharge lamp lighting device 10b further includes two inductors L1a and L1b that are magnetically coupled to each other, and one end (one output end) on the secondary side of the step-up transformer T1 and a discharge lamp (directly connected). The inductor L1a is connected in series between one end of the tube Lp1a and the inductor L1b is connected in series between the same one end on the secondary side of the step-up transformer T1 and one end of the discharge lamp (straight tube) LP1a. It is connected to the. The other ends of the discharge lamp Lp1a and the discharge lamp Lp1b and the other end (the other output end) on the secondary side of the step-up transformer T1 are grounded. Further, the discharge lamps Lp1a and Lp1b have parasitic capacitances Cp1a and Cp1b between other components of the discharge lamp lighting device 10 such as a housing.

  In the discharge lamp lighting device 10b, the coupled inductor 20 is formed by winding the windings constituting the inductors L1a and L1b around one common core, and the inductance of the inductor L1a and the discharge lamp Lp1a have. Each circuit constant is set so as to satisfy the series resonance condition with the parasitic capacitance Cp1a and the series resonance condition with the inductance of the inductor L1b and the parasitic capacitance Cp1b of the discharge lamp Lp1b. A constant current source whose current value does not depend on the impedance of the latter stage of each inductor L1a, L1b is configured.

  Although the discharge lamp lighting device 10b configured as described above has a simple and inexpensive circuit configuration, it can eliminate the variation in current caused by the variation in impedance of each discharge lamp. The flowing current can be controlled uniformly. Note that the number of discharge lamps driven by the discharge lamp lighting device 10b is not limited to two, and any number of two or more discharge lamps can be driven with the same configuration.

  FIG. 7 is a diagram showing a circuit configuration of a discharge lamp lighting device 10c according to the fourth embodiment of the present invention. The discharge lamp lighting device 10c has the same configuration as that of the discharge lamp lighting device 10a shown in FIG. 4, and in the following, the same components as those in FIG. The difference between these will be described.

  In the discharge lamp lighting device 10c shown in FIG. 7, a ballast element Ba1 is connected in series between one end on the secondary side of the step-up transformer T1 and the inductors L1a to Lna, and the other side on the secondary side of the step-up transformer T1. A ballast element Ba2 is connected in series between the end and the inductors L1b to Lnb. The ballast elements Ba1 and Ba2 include at least one of a choke coil, a capacitor, and a leakage inductance of the step-up transformer T1.

  The discharge lamp lighting device 10c configured as described above exhibits the same effects as the discharge lamp lighting device 10a, and in addition, discharge of a cold cathode tube having a negative resistance characteristic by the action of the ballast elements Ba1 and Ba2. The lamp can be lit stably.

  In the present embodiment, the ballast elements Ba1 and Ba2 are respectively connected between one end on the secondary side of the step-up transformer T1 and the inductors L1a to Lna, and on the other end on the secondary side of the step-up transformer T1 and the inductors L1b to L1b. Although connected to Lnb, the ballast element may be provided on the input side of the step-up transformer T1, for example, by connecting in series with a primary winding constituting the primary side of the step-up transformer T1. .

(Fifth embodiment)
FIG. 8 is a diagram showing a circuit configuration of a discharge lamp lighting device 10d according to the fifth embodiment of the present invention. The discharge lamp lighting device 10d has the same configuration as that of the discharge lamp lighting device 10a shown in FIG. 4, and hereinafter, the same reference numerals are given to the same components as those in FIG. The difference between these will be described.

  In the discharge lamp lighting device 10d shown in FIG. 8, the step-up transformer T1 is designed so that the parallel resonance condition is satisfied by the secondary-side self-inductance Lss of the step-up transformer T1 and the parasitic capacitance Cpc of the discharge lamp between the casings. It is characterized by being. Here, the parasitic capacitance Cpc represents the combined capacitance of the parasitic capacitances Cp1a to Cpna and Cp1b to Cpnb that each discharge lamp has between the casings. The discharge lamp lighting device 10d thus configured has the same effects as the discharge lamp lighting device 10a, and in addition to the inductors L1a to Lna and L1b to Lnb, the discharge lamps Lp1a to Lpna and Lp1b to Lpnb. Since the leakage current flowing to the parasitic capacitances Cp1a to Cpna and Cp1b to Cpnb can be reduced, the lighting efficiency can be increased.

  In the present embodiment, the parallel resonance circuit is a parallel resonance circuit using the secondary side self-inductance Lss of the step-up transformer T1 and the parasitic capacitance Cpc of the discharge lamp between the casings. Alternatively, an auxiliary capacitor may be connected to the position of the parasitic capacitor Cpc, and a configuration including a secondary side self-inductance Lss of the step-up transformer T1 and a combined capacitance of the parasitic capacitor Cpc and the auxiliary capacitor may be employed.

  As described above, the discharge lamp lighting device according to the present invention is a discharge lamp lighting device capable of uniformly controlling the current flowing through a plurality of discharge lamps with a simple and inexpensive circuit configuration, and a liquid crystal It can be suitably applied as a backlight device for a display device.

  The configuration of the discharge lamp lighting device according to the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the invention. For example, when driving a large number of discharge lamps as in the second (and fourth, fifth) embodiment, a plurality of units including a set of step-up transformers T1 and coupled inductors 20a are used. Can do. Also in the fourth and fifth embodiments, the discharge lamps driven by the respective discharge lamp lighting devices 10c and 10d are discharge lamps of other shapes such as straight tubes, U-tubes, and U-tubes. May be.

It is a circuit block diagram of the discharge lamp lighting device 10 in the 1st Embodiment of this invention. FIG. 2 is a principle circuit diagram equivalently replacing the circuit configuration diagram of FIG. 1. (A) is a circuit diagram for explaining a series resonance condition between an arbitrary inductor of a coupled inductor and a parasitic capacitance of a discharge lamp connected thereto, and (b) is a vector diagram thereof. It is a circuit block diagram of the discharge lamp lighting device in the 2nd Embodiment of this invention. FIG. 5 is a principle circuit diagram equivalently replacing the circuit configuration diagram of FIG. 4. It is a circuit block diagram of the discharge lamp lighting device in the 3rd Embodiment of this invention. It is a circuit block diagram of the discharge lamp lighting device in the 4th Embodiment of this invention. It is a circuit block diagram of the discharge lamp lighting device in the 5th Embodiment of this invention. It is a circuit block diagram which shows an example of the conventional discharge lamp lighting device of the system which drives a some discharge lamp with one inverter.

Explanation of symbols

10, 10a, 10b, 10c, 10d: discharge lamp lighting device, 15: inverter, 20, 20a: coupled inductor, Cp1a to Cpna, Cp1b to Cpnb, Cp: parasitic capacitance, L1a to Lna, L1b to Lnb: inductor, Lp1a to Lpna, Lp1b to Lpnb: discharge lamp (straight tube), (Lp1a, Lp1b) to (Lpna, Lpnb): discharge lamp (pseudo U-tube), T1: step-up transformer (transformer), Vac: AC voltage source, Vac2: Voltage source, Ba1, Ba2: Ballast element, Lss: Self-inductance

Claims (8)

  A discharge lamp lighting device that includes an inverter that converts a DC voltage into an AC voltage and a transformer that forms part of the inverter, and that drives at least one discharge lamp, and includes a plurality of inductors that are magnetically coupled to each other A coupled inductor is provided, and one of the plurality of inductors is connected in series between one end connected to the output end of the transformer of the discharge lamp and the output end, and each of the inductors A discharge lamp lighting device comprising a constant current source by series resonance of an inductance and a parasitic capacitance of the discharge lamp to which the inductor is connected.   At least one of the discharge lamps has one of the plurality of inductors connected to both ends of the discharge lamp, the inductor connected to one end of the discharge lamp connected to one output end of the transformer, and the discharge lamp. The discharge lamp lighting device according to claim 1, wherein the inductor connected to the other end of the electric lamp is connected to the other output end of the transformer and connected in a floating state.   The discharge lamp lighting device according to claim 1 or 2, wherein a ballast element is connected in series between an output end of the transformer and the inductor connected to the output end.   The discharge lamp lighting device according to claim 1, wherein a ballast element is provided on an input side of the transformer.   The discharge lamp lighting device according to claim 3 or 4, wherein the ballast element includes at least one of a choke coil, a capacitor, and a leakage inductance of the transformer.   The discharge lamp lighting device according to claim 1 or 2, wherein a parallel resonant circuit is configured by a self-inductance of the transformer and at least one parasitic capacitance or auxiliary capacitance of the discharge lamp.   The discharge lamp lighting device according to any one of claims 1 to 6, wherein the discharge lamp lighting device is incorporated in a backlight device for a liquid crystal display device. The discharge lamp lighting device according to any one of claims 1 to 7, wherein at least one of the discharge lamps is a straight tube, a U-shaped tube, a pseudo U-shaped tube, or a U-shaped tube.

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