JP2006228676A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a discharge lamp lighting device in which a high voltage necessary for lighting is secured using a simple structure, and losses due to constituent components is small at steady lighting. <P>SOLUTION: The discharge lamp lighting device comprises switching elements 3, 4 in which primary windings P1, P2 of two transformers T1, T2 are connected to a power supply 1 and which are connected in series to the primary windings P1, P2, a discharge lamp 15 which is impressed with output voltage of the secondary windings S1, S2 of the two transformers T1, T2 connected in series so that the generating voltage becomes symmetric, and a control part 5 which switching-controls the switching elements 3, 4 so as to impress the voltage of the power supply 1 alternately on the first windings P1, P2 of two transformers T1, T2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device that lights a discharge lamp with voltages output from two transformers.

In a conventional discharge lamp lighting device, a high voltage is generated by a boosting DC / DC converter such as a boosting chopper type switching regulator, and this voltage is input to a DC / AC inverter to generate a high frequency voltage to light the discharge lamp. (For example, refer to Patent Document 1).
In addition, there is a push-pull connection converter circuit that lights a cold cathode discharge fluorescent tube having a discharge start voltage of about 1200V. This is because a diode is connected to the primary side input terminal of the transformer constituting the push-pull converter circuit, and the regenerative current does not flow from the transformer to the power supply immediately after the semiconductor switch connected to the primary side of the transformer is opened. Thus, the flyback voltage generated on the secondary side of the transformer is applied to the cold cathode discharge fluorescent tube with a sufficient magnitude (see, for example, Patent Document 2).

Further, as a conventional discharge lamp lighting device, a DC booster circuit is arranged on both sides of a discharge lamp electrode, and the two DC booster circuits are operated alternately to supply AC power to the discharge lamp to light it. (For example, refer to Patent Document 3).
Also, there are two DC boosting circuits that perform switching control so that DC voltages having different polarities are applied to the discharge lamp from the respective DC boosting circuits (see, for example, Patent Document 4).

JP 2001-273996 A (page 4, FIG. 1) JP 2000-133484 A (3rd and 4th pages, FIGS. 1 and 2) Japanese Patent Laid-Open No. 6-76964 (page 3, FIGS. 1 and 2) JP-A-6-124790 (pages 6 and 7, FIGS. 5 to 14)

  Since the conventional discharge lamp lighting device is configured as described above, a DC / DC converter for boosting disclosed in Patent Document 1 and a DC / AC inverter that converts high voltage to high frequency are connected in series. A DC / DC converter that generates a high voltage necessary for lighting a high-intensity discharge lamp such as an HID lamp, and a DC / AC inverter having a capacity equivalent to that of the DC / DC converter are used. It is difficult to reduce the size and the cost is increased.

Further, when a discharge lamp such as a high-power HID lamp is lit using a push-pull type converter circuit having a diode for blocking a regenerative current shown in Patent Document 2, it is connected in series to a transformer. A large current flows through the diode, causing a large loss. For example, when a 35 W discharge lamp is lit with a 12V power supply, the efficiency is 80% and the input current is 3.6A. When the forward voltage drop of the diode is 1 V, a large loss of 3.6 W occurs. In the operation of the push-pull type converter, the energizing time of the switching element is ½ period of the output voltage at the maximum, and the direction of the current flowing to the primary side of the transformer is reversed in this period. Since energy cannot be stored and a flyback voltage cannot be generated, a high voltage must be generated using a large size transformer, which makes it difficult to reduce the size of the apparatus and increases the cost.
Further, when the discharge lamp is lit with the two DC boosting circuits disclosed in Patent Documents 3 and 4, the circuit configuration becomes complicated, the number of parts increases, the size is difficult to reduce, and the cost is high. Become.
In order to light a discharge lamp, a certain amount of high voltage is required as shown in Patent Documents 1 and 2, and particularly a high-intensity discharge lamp such as an HID lamp has a rated voltage of 5 to 5 before starting discharge. A voltage of about 10 times must be applied. When a DC high voltage is generated and then converted to an AC voltage and applied to a discharge lamp as described above, the parts constituting the circuit cause enormous size and cost increase, and the loss due to each circuit part is large. As a result, there was a problem that the operating efficiency deteriorated.

  The present invention has been made to solve the above-described problems, and has an object to obtain a discharge lamp lighting device that secures a high voltage necessary for lighting with a simple configuration and has little loss due to components during steady lighting. And

  The discharge lamp lighting device according to the present invention is connected in series so that two transformers having a primary winding connected to a power source, a switching element connected in series with the primary winding, and the generated voltage are symmetrical. A discharge lamp for applying the output voltage of the secondary windings of the two transformers, and a control means for controlling opening and closing of the switching elements so as to alternately apply a power supply voltage to the primary windings of the two transformers Is.

  According to the present invention, the output voltage of the secondary windings of two transformers connected in series so that the generated voltages are symmetrical is applied to the discharge lamp, and the control means controls the switching element to control the two transformers. Since the power supply voltage is alternately applied to the primary winding, the flyback voltage generated by the secondary winding of the transformer can be effectively used to reliably light the discharge lamp with a simple configuration. There is an effect that can be done.

An embodiment of the present invention will be described below.
Embodiment 1 FIG.
1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention. The positive electrode of the power source 1 that supplies the DC voltage is connected to the winding start side terminal of the primary winding P1 of the transformer T1 and the winding start side terminal of the primary winding P2 of the transformer T2. The negative electrode of the power supply 1 is grounded. In addition, "." Is added to the winding start side of the winding of each transformer described in each circuit diagram of FIG. The two transformers T1 and T2 have the same rating in which the primary winding and the secondary winding are insulated. The switching element 3 is connected to the terminal of the primary winding P1 of the transformer T1. The switching element 4 is connected to the terminal of the primary winding P2 of the transformer T2. For example, when an n-channel FET is used as the switching elements 3 and 4, the terminal of the primary winding P 1 is connected to the drain of the switching element 3, and the terminal of the primary winding P 2 is connected to the drain of the switching element 4. Terminal is connected. Each source of the switching elements 3 and 4 is grounded, and each gate is connected to a control unit (control means) 5.

  The terminal of the secondary winding S1 of the transformer T1 is connected to the terminal of the secondary winding S2 of the transformer T2, and the secondary winding S1 of the transformer T1 and the secondary winding S2 of the transformer T2 are respectively Are connected in series so that the winding start side terminals are both ends. One end of the capacitor 6 and one end of the capacitor 14 are connected to the winding start side terminal of the secondary winding S1. The other end of the capacitor 14 is connected to one electrode of a discharge lamp 15 such as an HID bulb. The other end of the capacitor 6 is connected to the cathode of the diode 7 and the anode of the diode 8. The anode of the diode 7 is connected to the winding start side terminal of the secondary winding S2 of the transformer T2, one end of the capacitor 9, one end of the capacitor 11, and the primary winding terminal of the igniter transformer T3. The diodes 7 and 8, the capacitors 6 and 9, and the resistor 10 connected in this way constitute a multiplied voltage rectifier circuit.

  The igniter transformer T3 is an autotransformer in which a part of the primary winding and the secondary winding are configured in common. The other end of the capacitor 9 is connected to the cathode of the diode 8 and one end of the resistor 10. The other end of the resistor 10 is connected to the other end of the capacitor 11 and one end of the GAP switch 12. The other end of the GAP switch 12 is connected to a common terminal of the primary winding and the secondary winding of the igniter transformer T3. The GAP switch 12 is in a conductive state due to dielectric breakdown when a high voltage of several hundred volts or more is applied between the electrodes due to its own breakdown characteristics. The secondary winding terminal of the igniter transformer T3 is connected to the other electrode of the discharge lamp 15. An igniter circuit is constituted by the capacitor 11 for discharging (high voltage pulse generation), the GAP switch 12, and the igniter transformer T3.

Next, the operation will be described.
As described above, the igniter transformer T3 that generates a high voltage pulse is connected in series between the secondary winding S2 of the transformer T2 and the discharge lamp 15, and the secondary windings S1 and S2 are connected in series. A high voltage pulse is superimposed on the output voltages of the transformers T1 and T2 to break down between the electrodes of the discharge lamp 15, and the discharge lamp 15 is started.
In the transformers T1 and T2, the primary windings P1 and P2 are connected in parallel to the power source 1, and the secondary windings S1 and S2 are connected in series to the discharge lamp 15 serving as a load. . By connecting in this way, the transformers T1 and T2 operate independently of each other without being magnetically coupled, and each can generate a flyback voltage. Accordingly, a high voltage can be generated in a state near the no load before the breakdown between the electrodes of the discharge lamp 15, and when the discharge lamp 15 starts discharging and current flows, the output voltage naturally decreases. Supply an appropriate current. The control unit 5 controls the switching frequency of the switching elements 3 and 4 so that a flyback voltage having a sufficiently high voltage value is generated in the secondary windings S1 and S2 of the transformers T1 and T2.

  The control unit 5 controls the switching operation so that the switching elements 3 and 4 are alternately turned on. When the switching element 3 is in the ON state, the terminal on the termination side of the primary winding P1 of the transformer T1 is grounded, and the voltage of the power source 1 is applied to the primary winding P1. When the switching element 3 is turned off by the control of the control unit 5, the ground connection of the primary winding P1 is cut off. At the moment when the switching element 3 changes from the ON state to the OFF state, a flyback voltage is generated at both ends of the secondary winding S1 due to the energy accumulated during the ON state of the transformer T1. Similarly, in the tonulus T2 to which the switching element 4 is connected, when the switching element 4 is in the ON state, the voltage of the power source 1 is applied to the primary winding P2 of the transformer T2, and the switching element 4 is caused by the energy accumulated during that time. At the moment of transition from the ON state to the OFF state, a flyback voltage is generated at both ends of the secondary winding S2.

  A multiplied voltage rectifier circuit comprising a capacitor 6, diodes 7 and 8, a capacitor 9 and a resistor 10 inputs a high voltage generated at both ends of the secondary windings S1 and S2 connected in series of the transformers T1 and T2, and the multiplied rectifier. And applied to the capacitor 11 for discharge. By providing the multiplied voltage rectifier circuit, the igniter circuit can generate a high pulse voltage even when the output voltages of the transformers T1 and T2 are low. That is, it is possible to use a small transformer with a low output voltage as the transformers T1 and T2. When the high voltage pulse is output from the igniter transformer T3, the multiplied voltage rectifier circuit absorbs a surge voltage that vibrates in both positive and negative polarities, and is connected to the primary coils P1 and P2 of the transformers T1 and T2. The switching elements 3 and 4 are protected by preventing an excessive voltage from being applied to the elements 3 and 4. When the output voltages of the secondary windings S1 and S2 of the transformers T1 and T2 are sufficiently high and the discharging capacitor 11 can be charged to a predetermined high voltage, the output voltage of the transformers T1 and T2 is set by the rectifier circuit. The DC voltage may be applied to the capacitor 11 by rectification.

The voltage generated at both ends of the secondary windings S1 and S2 of the transformers T1 and T2 is converted into a DC high voltage by the above-described multiplying voltage rectifier circuit, and this DC high voltage is applied to the capacitor 11 for charging. When the voltage across the capacitor 11 reaches a predetermined high voltage due to this charging, the insulation between the electrodes of the GAP switch 12 to which the voltage across the capacitor 11 is applied is broken and turned on, and the discharge voltage of the capacitor 11 is changed to an igniter. Applied to the primary winding of the transformer T3. Then, a high voltage pulse is generated in the secondary winding of the igniter transformer T 3, and this high voltage pulse is applied to the discharge lamp 15. The high voltage pulse generated by the igniter transformer T3 breaks down between the electrodes of the discharge lamp 15 and starts discharging.
When the GAP switch 12 having a high turn-on voltage is used, the voltage applied from the capacitor 11 to the igniter transformer T3 increases. Therefore, a high voltage pulse for starting the discharge lamp 15 can be generated by the igniter transformer T3 having a small number of turns. It becomes possible.

The activated discharge lamp 15 applies a voltage output from the secondary winding S1 of the transformer T1 to one electrode via the capacitor 14, and outputs from the secondary winding S2 of the transformer T2 via the igniter transformer T3. Is applied to the other electrode to perform steady lighting.
Since no current flows between the electrodes before the discharge lamp 15 is started, the transformers T1 and T2 are almost unloaded. The output voltage of the transformers T1 and T2 is applied to the capacitor 6 via the diode 7. Since one end of the capacitor 6 is connected to the winding start side terminal of the secondary winding S1 of the transformer T1, and the other end is connected to the cathode of the diode 7, the capacitor 6 is connected to the secondary winding S1 of the transformer T1. The generated flyback voltage is applied, and a voltage across 400 V, for example, is generated. This voltage is applied to the other end of the capacitor 9 via the diode 8. Since one end of the capacitor 9 is connected to the winding start side terminal of the secondary winding S2 of the transformer T2, the flyback voltage generated in the secondary winding S2 is applied to one end of the capacitor 9, and the capacitor 9 The voltage between both ends is 800V. The voltage generated in the capacitor 9 is applied to the capacitor 11 via the resistor 10 to charge the capacitor 11. When the voltage across the capacitor 11 reaches, for example, 800V, the GAP switch 12 is turned on, voltage is applied across the primary winding of the igniter transformer T3, and the voltage generated in the secondary winding of the igniter transformer T3, for example, A high voltage pulse of 25 kV is applied to the discharge lamp 15.

The discharge lamp 15 to which a high voltage pulse of 25 kV is applied by the igniter transformer T3 starts discharge between the electrodes due to its breakdown characteristics. After the discharge lamp 15 starts lighting, a current flows between the electrodes of the discharge lamp 15 as the discharge phenomenon stabilizes, and a transformer that applies a flyback voltage to the discharge lamp 15 due to the current flowing. The voltage across the secondary windings S1 and S2 of T1 and T2 drops to, for example, about 85V and becomes constant. The voltage necessary to maintain the discharge state from immediately after the discharge lamp 15 is started by the high voltage pulse output from the igniter transformer T3 until it enters the steady lighting state, that is, from the start of discharge until the discharge state becomes stable, is At this time, the flyback voltage output from the transformers T1 and T2 changes according to the load variation, and the discharge lamp 15 is kept on.
The discharge lamp 15 that has started the discharge is turned on by the AC voltage output from the transformers T1 and T2. This AC voltage has the switching frequency of the switching elements 3 and 4.

When the discharge lamp 15 is turned on, a current flows between the electrodes of the discharge lamp 15, and an igniter transformer T3 connected in series between the secondary winding S2 of the transformer T2 and the discharge lamp 15 acts on this current as a resistance. To do. In order to cancel the resistance component (inductance) of the igniter transformer T3, the capacitor 14 is connected in series between the secondary winding S1 of the transformer T1 and the discharge lamp 15, that is, the igniter transformer T3 and the capacitor 14 are connected in series. A resonance circuit is configured to resonate the capacitance of the capacitor 14 and the inductance of the igniter transformer T3.
The control unit 5 controls the switching frequency of the switching elements 3 and 4, and the frequency of the voltage output from the secondary windings S1 and S2 of the transformers T1 and T2, that is, the frequency of the voltage for lighting the discharge lamp 15, Adjustment is made so that the resonance frequency between the capacitance of the capacitor 14 and the inductance of the igniter transformer T3 or a frequency near the resonance frequency is obtained. The capacitor 14 has a capacitance that cancels the impedance due to the inductance of the igniter transformer T3 at a frequency at which the discharge lamp 15 performs steady lighting. Thus, the reactive power can be eliminated by canceling the impedance of the igniter transformer T3 and the like, and the power can be efficiently transmitted to the discharge lamp 15.

When the capacitor 14 is connected in series to the circuit for lighting the discharge lamp 15 as described above to cancel the influence of the inductance existing in the circuit, the transformers T1 and T2 are also connected in series when viewed from the discharge lamp 15. Therefore, the inductance of the secondary windings S1 and S2 of the transformers T1 and T2 also affects the resonance element.
The secondary windings S1 and S2 of the transformers T1 and T2 have large inductances when the switching elements 3 and 4 are in the OFF state. In order to reduce the influence of the inductance that varies depending on the ON / OFF state of the switching elements 3 and 4 and to make the resonance frequency constant, the inductances of the transformers T1 and T2 are preferably small values, and the inductances smaller than the inductance of the igniter transformer T3. The transformers T1 and T2 are used. For example, the transformers T1 and T2 and the igniter transformer T3 having an inductance ratio of 1:10 are used.
Note that the inductances of the transformers T1 and T2 vary depending on the gaps and shapes of the core members of the transformers T1 and T2, and those having small inductances obtained by appropriately adjusting these elements are used.

  2 and 3 are explanatory diagrams showing the operation of the discharge lamp lighting device according to the first embodiment. This figure shows the voltage across the primary winding P1 of the transformer T1 shown as “P1 voltage”, the voltage across the secondary winding S1 shown as “S1 voltage”, and “P2 voltage”. Each waveform of the voltage across the primary winding P2 of the transformer T2 and the voltage across the secondary winding S2 shown as “voltage of S2” is shown. The waveform of the potential difference generated between the winding start side terminal of the secondary winding S1 of the transformer T1 and the secondary winding S2 winding start side terminal of the transformer T2 is shown. 2 shows voltage waveforms when the switching elements 3 and 4 for applying the power supply voltage to the transformers T1 and T2 are operated with an ON duty of 50% or more, and FIG. 3 shows voltage waveforms when the ON duty is made less than 50%. It is.

  The flyback voltages are generated in the secondary windings S1 and S2 of the transformers T1 and T2 by the ON / OFF operation of the switching elements 3 and 4, respectively, which is OFF more than when the switching elements 3 and 4 are in the ON state. In the state, the maximum high voltage is output particularly at the moment of transition from the ON state to the OFF state. The transformers T1 and T2 generate a high voltage of about 400 V, for example, as a flyback voltage. As shown in FIG. 1, the secondary winding S1 of the transformer T1 and the secondary winding S2 of the transformer T2 are connected to the respective terminal terminals, and the polarity of the voltage generated in each secondary winding is positive or negative. The discharge lamp 15 is lit using the voltage across the secondary winding S1 and the secondary winding S2 connected in series so as to be symmetrical. When the two secondary windings are connected in this way and the switching elements 3 and 4 are turned ON alternately, the flyback voltages output from the transformers T1 and T2 are symmetrical between the high side voltage and the low side voltage. It can be applied to the discharge lamp 15 as an alternating voltage.

When the secondary windings S1 and S2 are connected in series in this way, for example, the output voltage of the transformer T1 is canceled by the output voltage of the transformer T2.
As shown in FIG. 2, when the switching elements 3 and 4 are operated with an ON duty of 50% or more, for example, when “P1 voltage” in the figure is OFF, “S1 voltage” is output from the transformer T1. The flyback voltage is a voltage waveform shown as “S1-S2 voltage” because the “S2 voltage” of the transformer T2 maintains a constant low-side voltage while the flyback voltage is generated. Thus, the high voltage is applied to the discharge lamp 15. This is the same when the flyback voltage is output from the transformer T2, that is, when the “P2 voltage” in FIG.

  When the switching elements 3 and 4 are operated with the ON duty of less than 50% as shown in FIG. 3, when the “P1 voltage” in FIG. 3 is OFF, the output from the transformer T1 expressed as “S1 voltage”. A state occurs in which the flyback voltage being overlapped with the flyback voltage output from the transformer T2 expressed as “voltage of S2”. In this state, when the output voltage of the transformer T1 becomes the maximum high voltage at the moment when the “P1 voltage” transitions from the ON state to the OFF state, the “P2 voltage” is still in the OFF state, and thus is output from the transformer T2. The high voltage “S2 voltage” is overlapped, and the high voltage output from the transformer T1 is canceled and reduced as shown as “S1-S2 voltage”. This is because the flyback voltage of the transformer T2 generated at the moment when the “voltage of P2” transits from the ON state to the OFF state is similarly reduced by the high voltage being canceled by the output voltage of the transformer T1.

When the switching element 3 or the switching element 4 is in the OFF state, the inductance of each winding of the transformers T1 and T2 increases. When the secondary winding S1 and the secondary winding S2 are connected in series, the steep flyback voltage generated in the other transformer is absorbed by the inductance when the one transformer is in the OFF state. It becomes difficult to output a high voltage such as “S1-S2 voltage”.
Therefore, when the discharge lamp 15 is lit, when the switching element of one transformer is turned off and the one transformer generates a flyback voltage, the switching element connected to the other transformer is turned on. As is maintained, the switching elements 3 and 4 are operated with an ON duty of 50% or more. When controlling the switching operation of the switching elements 3 and 4 in this way, the control unit 5 operates so that the phase of the ON state of the switching element 3 and the ON state of the switching element 4 is shifted by 180 degrees. , 4 is operated with an ON duty of 50% or more. When operated in this way, at the instant when one switching element transitions from the ON state to the OFF state, the other switching element always maintains the ON state, and the flyback voltage is output without being canceled. .

  As described above, according to the first embodiment, one end of the primary windings P1 and P2 of the two transformers T1 and T2 is connected to the power source 1, and the other end of the primary windings P1 and P2 is grounded. The switching elements 3 and 4 are connected to each other, and the secondary windings S1 and S2 of the two transformers T1 and T2 are connected in series so that the generated voltages are symmetric. Is connected to the discharge lamp 15 so that the voltage of the power source 1 is alternately applied to the primary windings P1 and P2 of the two transformers T1 and T2. Since the control is performed, there is an effect that the discharge lamp 15 can be efficiently turned on with a simple configuration.

Embodiment 2. FIG.
FIG. 4 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention. The same reference numerals are used for the same or corresponding parts as shown in FIG. Also, the description of the parts configured in the same manner as the circuit shown in FIG. 1 is omitted, and the parts that are characteristic of the discharge lamp lighting device according to Embodiment 2 will be described. The circuit shown in FIG. 4 is connected and configured in the same manner as that shown in FIG. 1 except that the terminal terminals of the secondary winding S1 of the transformer T1 and the secondary winding S2 of the transformer T2 are grounded. .

Next, the operation will be described.
In the discharge lamp lighting device shown in FIG. 4, the flyback voltage generated by grounding each terminal of the secondary windings S1 and S2 of the transformers T1 and T2 becomes a high voltage increased from the ground level, The voltage output from the transformer T1 and the voltage output from the transformer T2 are superimposed on the basis of the ground level, and an alternating voltage having a positive / negative symmetrical value about the ground level is applied to the discharge lamp 15 to light it. By grounding one end of the secondary windings S1 and S2 in this way, the AC voltage output from the secondary windings S1 and S2 changes with the ground level as a reference potential, and the secondary winding S1. , S2 can be kept low, and a transformer having a low breakdown voltage between the primary winding and the secondary winding can be used as the transformers T1 and T2.
Other operations are similar to those of the discharge lamp lighting device according to the first embodiment described with reference to FIGS. Here, the description of the same operation as that of the discharge lamp lighting device according to Embodiment 1 is omitted. The reference potential is not limited to the ground level, and may be operated by applying an appropriate potential to the connection point between the secondary winding S1 and the secondary winding S2.

  As described above, according to the second embodiment, the terminal of the secondary winding S1 of the transformer T1 is grounded, the terminal of the secondary winding S2 of the transformer T2 is grounded, and the voltage is supplied to the discharge lamp 15. Since the voltage is applied, the transformers T1 and T2 having a low dielectric breakdown voltage between the primary winding and the secondary winding can be used, and the cost can be suppressed.

Embodiment 3 FIG.
FIG. 5 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 3 of the present invention. The same reference numerals are used for parts that are the same as or correspond to those shown in FIGS. The discharge lamp lighting device shown in FIG. 5 replaces the transformers T1 and T2 between the primary winding and the secondary winding shown in FIG. A single-winding transformer, that is, a transformer T11, T12 of an autotransformer that is configured by sharing a part of the transformer is used.
The transformer T11 has a primary winding terminal connected to the positive electrode of the power source 1 and a secondary winding terminal connected to one end of the capacitor 14 and one end of the capacitor 6. The common terminal of the primary winding and the secondary winding is connected to the drain of the switching element 3. The transformer T12 has a primary winding terminal connected to the positive electrode of the power supply 1, a secondary winding terminal connected to the anode of the diode 7, one end of the capacitor 9, one end of the capacitor 11, and the primary winding terminal of the igniter transformer T3. Connect to. The common terminal of the primary winding and the secondary winding is connected to the drain of the switching element 4.
Portions other than those described above are connected in the same manner as that shown in FIG. 4 and further shown in FIG. 1, and description thereof is omitted here. The discharge lamp lighting device shown in FIG. 5 operates in the same manner as that shown in FIG. The inductances of the transformers T11 and T12 are preferably small as described in the first embodiment.

  As described above, according to the third embodiment, since the lighting voltage of the discharge lamp 15 is generated using the transformers T11 and T12 of the autotransformer, the discharge lamp lighting device can be downsized. There is.

It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 1 of this invention. FIG. 6 is an explanatory diagram showing the operation of the discharge lamp lighting device according to Embodiment 1. FIG. 6 is an explanatory diagram showing the operation of the discharge lamp lighting device according to Embodiment 1. It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 3 of this invention.

Explanation of symbols

  1 power supply, 3, 4 switching element, 5 control unit (control means), 6 capacitor, 7, 8 diode, 9 capacitor, 10 resistor, 11 capacitor, 12 GAP switch, 14 capacitor, 15 discharge lamp, T1, T2, T11 , T12 transformer, T3 igniter transformer.

Claims (7)

Two transformers with primary windings connected to the power supply;
A switching element connected in series with the primary winding;
A discharge lamp for applying the output voltage of the secondary windings of the two transformers connected in series so that the generated voltage is symmetrical;
A discharge lamp lighting device comprising: control means for controlling opening and closing of the switching element so that a power supply voltage is alternately applied to primary windings of the two transformers.   2. The discharge lamp lighting device according to claim 1, wherein a connection point of secondary windings connected in series of two transformers is grounded as a reference potential.   3. The discharge lamp lighting device according to claim 1, wherein an igniter transformer for generating a high voltage pulse is connected in series between the secondary winding of the two transformers connected in series and the discharge lamp. A capacitor is connected in series between the secondary winding of the two transformers connected in series and the igniter transformer,
4. The discharge lamp lighting device according to claim 3, wherein the control means operates the switching element so as to light the discharge lamp at a frequency close to a resonance frequency due to the inductance of the igniter transformer and the capacitance of the capacitor.   5. The discharge lamp according to claim 3, wherein the output voltage of the secondary winding connected in series of the two transformers is rectified or multiplied rectified to charge the igniter high voltage pulse generating capacitor. Lighting device.   The discharge lamp lighting device according to any one of claims 1 to 5, wherein the control means operates the ON duty of the switching element at 50% or more.   The discharge lamp lighting device according to any one of claims 1 to 6, wherein the inductance of the secondary winding connected in series of the two transformers is smaller than the inductance of the igniter transformer.

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