JP2006221994A - Lamp driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformalize a current flowing through a lamp like a discharge tube while stabilizing a voltage at a secondary winding side of a transformer. <P>SOLUTION: A closed loop is formed by serially connecting secondary windings of a plurality of transformers T1, T2 and two or more lamps LP1, LP2. Primary windings of the plurality of transformers are connected to an alternating current power source V1, and at least one point of the closed loop is grounded in terms of a direct current, for example, through resistors R1, R2 having resistance values larger than a prescribed one. By adopting such a structure, a state that is grounded in terms of direct current, and floated in terms of alternating current is formed at the closed loop, namely, at the secondary winding side of the transformer. The current is balanced since the lamp is serially connected in terms of alternating current, and it is possible to keep the voltage at the secondary winding side of the transformer in a stable state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lamp driving circuit.

  For example, a discharge tube such as a cold cathode fluorescent tube has been conventionally used for a backlight of a liquid crystal display device. In recent years, the number of discharge tubes used for backlights has increased due to the increase in the size of liquid crystal display devices. However, it is required to make the current flowing through them uniform and to make the luminance uniform.

FIG. 1 shows a lighting circuit disclosed in Japanese Utility Model Laid-Open No. 59-187097. The lighting circuit shown in FIG. 1 includes an inverter V101, transformers T101 and T102, discharge tubes LP101 and LP102, and capacitors C101, C102, and C103. The inverter V101 is connected to terminals P1 and P2 of the primary winding of the transformer T101 and terminals P1 and P2 of the primary winding of the transformer T102. Note that the primary winding terminal P1 and the secondary winding terminal S1 of the transformer T101 are connected via a capacitor C102, and the primary winding terminal P1 and the secondary winding terminal S1 of the transformer T102 are both connected to the capacitor C103. Connected through. Further, the first terminal of the discharge tube LP101 is connected to the terminal S1 of the secondary winding of the transformer T101, and the second terminal of the discharge tube LP101 is connected to the terminal S1 of the secondary winding of the transformer T102. Has been. The first terminal of the discharge tube LP102 is connected to the terminal S2 of the secondary winding of the transformer T101, and the second terminal of the discharge tube LP102 is the terminal of the secondary winding of the transformer T102 via the capacitor C101. Connected to S2. Thus, the discharge tubes LP101 and LP102 are floating differential drive in which the left and right poles are opposite in polarity. However, a capacitor is connected to the secondary windings of the transformers T101 and T102, and there is a problem that the current balance of both the discharge tubes LP101 and LP102 is shifted by the capacity of the capacitor, resulting in a difference in the luminance of the discharge tubes. . Further, no consideration has been given as to what configuration is preferable when the number of discharge tubes is three or more.
Japanese Utility Model Publication No.59-187097

  Accordingly, an object of the present invention is to provide a lamp driving circuit capable of equalizing the current flowing through a lamp such as a discharge tube while stabilizing the potential on the secondary winding side of the transformer.

  A lamp driving circuit according to a first aspect of the present invention includes a plurality of transformers, and a secondary winding in the plurality of transformers and two or more lamps are connected in series to form a closed loop. The primary winding is connected to an AC power source, and at least one point of the closed loop is DC grounded. By adopting such a configuration, a closed loop, that is, a secondary winding side of the transformer, a DC grounded state and an AC float state are formed, and the lamps are connected in series AC. Therefore, the current balance is achieved and the potential on the secondary winding side of the transformer can be kept stable. The DC grounding at least one point in the closed loop may be performed via a resistor having a resistance value equal to or higher than a predetermined value, or may be performed via a predetermined coil or the like.

  Note that the closed loop described above can include at least two or more parts where a lamp is connected to the subsequent stage of the secondary winding when the closed loop circuit direction is defined as one direction. is there. In the closed loop described above, at least one of the lamps may be disposed between the secondary windings. A configuration in which a potential of opposite polarity is generated at both ends of the lamp is preferable in terms of safety and noise. When the potentials of opposite polarity are generated in this way, it is desirable to ground both lines where the potentials of each polarity are generated in a DC manner.

  Further, at least one transformer may have an intermediate tap on the secondary winding side, and at least one DC grounding of the closed loop described above may be performed via the intermediate tap. In a state where the current is balanced, a potential difference does not occur at both ends of the resistor, and loss is reduced.

  Each of the plurality of transformers may have an intermediate tap on the secondary winding side, and the above-described closed loop DC grounding may be performed via the intermediate tap. In this way, the potential can be stabilized even when the lamp is opened.

  Further, at least one transformer may have an intermediate tap on the secondary winding side, and at least one DC grounding of the closed loop may be performed via the intermediate tap. Further, it may further include a circuit for automatically adjusting the driving voltage of the AC power source or stopping the output by detecting the unbalanced voltage by dividing the ground of the intermediate tap and feeding it back. In this way, the lamp driving circuit can be operated safely and stably.

  Further, at least one transformer may have an intermediate tap on the secondary winding side, and at least one DC grounding of the closed loop may be performed via the intermediate tap. Further, the AC power supply is provided by performing feedback by using the voltage of the transformer primary winding or the voltage of the transformer voltage detection tertiary winding and the unbalance voltage detected by dividing the ground of the intermediate tap in combination. A circuit for automatically adjusting the output voltage or stopping the output may be further included. In this way, the lamp driving circuit can be operated safely and stably.

  The at least one transformer may have an intermediate tap on the secondary winding side, and at least one DC grounding of the closed loop may be performed via the intermediate tap. Furthermore, a weighted sum voltage of the maximum absolute value of the voltage of the primary winding of the transformer or the voltage of the voltage detecting tertiary winding and the maximum absolute value of the unbalance voltage detected by dividing the ground of the intermediate tap is obtained. A circuit for automatically adjusting or stopping output of the drive voltage of the AC power supply by feedback may be further included.

  Further, at least one transformer may have an intermediate tap on the secondary winding side, and at least one DC grounding of the closed loop may be performed via the intermediate tap. Furthermore, the weighted sum voltage and the weighted difference voltage of the transformer primary winding voltage or the transformer voltage detection tertiary winding voltage and the unbalance voltage detected by dividing the ground of the intermediate tap are used in combination. Further, a circuit for automatically adjusting the drive voltage of the AC power supply or stopping the output may be further included by performing feedback. In this way, the lamp driving circuit can be operated safely and stably.

  The lamp driving circuit according to the second aspect of the present invention includes first and second transformers whose primary windings are connected to an AC power source, and between the secondary windings of the first and second transformers. A closed loop in which lamps are arranged in series is configured, and the first and second transformers apply first and second voltages having different polarities to both ends of the lamp, and the closed loop includes a line on which the first voltage is generated; It is grounded in a direct current manner in each of the lines where the second voltage is generated.

  A lamp driving circuit according to a third aspect of the present invention includes first and second transformers whose primary windings are connected to an AC power supply, and between the secondary windings of the first and second transformers. A closed loop in which the lamps are arranged in series is configured, and the first and second transformers apply first and second voltages having different polarities to both ends of the lamp, and are applied to the secondary windings of the first and second transformers. Is provided with an intermediate tap, and the closed loop is galvanically grounded via the intermediate tap.

  There are a plurality of circuits for realizing the above configuration, and specific examples are shown below, but the present invention is not limited to these.

  According to the present invention, the current flowing through the lamp such as the discharge tube can be made uniform while stabilizing the potential on the secondary winding side of the transformer.

1. Embodiment 1
FIG. 2A shows a discharge tube driving circuit 10 according to the first embodiment of the present invention. The discharge tube drive circuit 10 in FIG. 2A includes AC power supplies V1 and V2, discharge tubes LP1 and LP2 such as cold cathode fluorescent tubes, resistors R1 and R2, and transformers T1 and T2. The resistance values of the resistors R1 and R2 are preferably 10 MΩ to 100 MΩ, for example, from the viewpoint of grounding and current balance. In all embodiments of the present application, the AC power supply includes a switching inverter power supply, and examples of the switching circuit include a full bridge and a half bridge.

  The AC power supply V1 is connected to the primary winding of the transformer T1, and the AC power supply V2 is connected to the primary winding of the transformer T2. Although not shown in the figure, the AC power supplies V1 and V2 are controlled so that voltages having opposite polarities are generated at both ends of the discharge tubes LP1 and LP2. That is, the discharge tube is differentially driven. In addition, one AC power source may be connected to the primary windings of the transformers T1 and T2 without dividing the AC power source in this way. One end of the secondary winding of the transformer T1 is connected to one end of the discharge tube LP1, and the other end of the secondary winding of the transformer T1 is connected to one end of the resistor R1 and one end of the discharge tube LP2. The other end of the resistor R1 is grounded. The other end of the discharge tube LP1 is connected to one end of the secondary winding of the transformer T2 and one end of the resistor R2. The other end of the resistor R2 is grounded. The other end of the discharge tube LP2 is connected to the other end of the secondary winding of the transformer T2.

  Thus, the secondary winding of the transformer T1, the discharge tube LP1, the secondary winding of the transformer T2, and the discharge tube LP2 constitute a closed loop. In addition, since the direct current is grounded at two places via the high resistances R1 and R2, the potential on the secondary winding side of the transformers T1 and T2 is stabilized. On the other hand, the secondary windings of the transformers T1 and T2 are in a floating state in terms of alternating current. Therefore, since the discharge tubes LP1 and LP2 are connected in a loop in series in an alternating current manner, the current is made uniform, and there is no variation in luminance of the discharge tubes.

  In addition, since the floating differential drive system is adopted, since current does not flow in earnest unless two places where high voltage is applied are touched, it is difficult to get an electric shock and is highly safe. In addition, reverse polarity voltage is applied to both ends of the discharge tube, and the polarity of the discharge tubes arranged adjacent to each other is also reversed, so that there is an effect that noise is hardly generated.

  FIG. 2B shows a modification of the first embodiment. In FIG. 2A, the resistor R1 is connected to the discharge tube LP2, and the resistor R2 is connected to the discharge tube LP1, but in the example of FIG. 2B, the resistor R1 is connected to one end of the discharge tube LP2. R2 is connected to the other end of the discharge tube LP2. The resistors R1 and R2 may be connected to the discharge tube LP1. Even if the resistors R1 and R2 are connected in this manner, the same effect as in FIG.

  Since the grounding resistors R1 and R2 are only required to be grounded in a DC manner, for example, a coil or the like can be used.

2. Embodiment 2
FIG. 3 shows a discharge tube driving circuit 20 according to the second embodiment of the present invention. The discharge tube drive circuit 20 of FIG. 3 includes AC power supplies V3 and V4, discharge tubes LP3 and LP4, resistors R3 and R4, and transformers T3 and T4 provided with an intermediate tap on the secondary winding side.

  The AC power supply V3 is connected to the primary winding of the transformer T3, and the AC power supply V4 is connected to the primary winding of the transformer T4. Although not shown in the figure, the AC power supplies V3 and V4 are controlled so that voltages of opposite polarities are generated at both ends of the discharge tubes LP3 and LP4. That is, the discharge tube is differentially driven. In addition, one AC power source may be connected to the primary windings of the transformers T3 and T4 without dividing the AC power source in this way. One end of the secondary winding of the transformer T3 is connected to one end of the discharge tube LP3, and the other end of the discharge tube LP3 is connected to one end of the secondary winding of the transformer T4. The other end of the secondary winding of the transformer T4 is connected to one end of the discharge tube LP4, and the other end of the discharge tube LP4 is connected to the other end of the secondary winding of the transformer T3. The intermediate tap of the secondary winding of the transformer T3 is grounded via a high-resistance resistor R3, and the intermediate tap of the secondary winding of the transformer T4 is also grounded via a high-resistance resistor R4. .

  Thus, also in the second embodiment, the secondary winding of the transformer T3, the discharge tube LP3, the secondary winding of the transformer T4, and the discharge tube LP4 constitute a closed loop. In addition, since the direct current is grounded at two places via the high resistances R3 and R4, the potential on the secondary winding side of the transformers T3 and T4 is stabilized. On the other hand, the secondary windings of the transformers T3 and T4 are floated in terms of alternating current. Accordingly, since the discharge tubes LP3 and LP4 are connected in a loop in series in an alternating current manner, the current is made uniform and there is no variation in luminance.

  As in the first embodiment, the floating differential drive system is adopted, but the difference is that the intermediate taps of the secondary windings of the transformers T3 and T4 are grounded via a resistor. For this reason, in the second embodiment, a potential difference does not occur at both ends of the resistors R3 and R4 in a state where the current is balanced, and no current flows, so that there is less loss compared to the first embodiment. Become.

3. Embodiment 3
FIG. 4 shows a discharge tube driving circuit 30 according to a third embodiment of the present invention. The discharge tube driving circuit 30 in FIG. 4 includes an AC power supply V5, transformers T5 to T8, discharge tubes LP5 to LP8, and resistors R5 and R6. The AC power supply V5 includes terminals P1 and P2 of the primary winding of the transformer T5, terminals P1 and P2 of the primary winding of the transformer T6, a terminal P2 of the primary winding of the transformer T7, and a terminal of the primary winding of the transformer T8. Connected to P1. A terminal P1 of the primary winding of the transformer T7 and a terminal P2 of the primary winding of the transformer T8 are connected. That is, the primary winding of the transformer T5 and the primary winding of the transformer T6 are in parallel. The primary winding of the transformer T7 and the primary winding of the transformer T8 are connected in series. The transformer T5 and the transformer T7, and the transformer T6 and the transformer T8 are connected to the AC power supply V5 so as to be in reverse phase. That is, the discharge tube is differentially driven. The transformers T5 and T6 are of the type having an intermediate tap S2 on the secondary winding side, and the intermediate tap S2 of the secondary winding of the transformer T5 is grounded via a high-resistance resistor R5. . Further, the intermediate tap S2 of the secondary winding of the transformer T6 is grounded via a high-resistance resistor R6.

  The first terminal of the discharge tube LP5 is connected to the terminal S1 of the secondary winding of the transformer T5, and the second terminal of the discharge tube LP5 is connected to the terminal S2 of the secondary winding of the transformer T7. . The first terminal of the discharge tube LP6 is connected to the terminal S3 of the secondary winding of the transformer T5, and the second terminal of the discharge tube LP6 is connected to the terminal S1 of the secondary winding of the transformer T7. . Similarly, the first terminal of the discharge tube LP7 is connected to the terminal S1 of the secondary winding of the transformer T6, and the second terminal of the discharge tube LP7 is connected to the terminal S2 of the secondary winding of the transformer T8. The The first terminal of the discharge tube LP8 is connected to the terminal S3 of the secondary winding of the transformer T6, and the second terminal of the discharge tube LP8 is connected to the terminal S1 of the secondary winding of the transformer T8. . Thus, a loop is formed by the discharge tubes LP5 and LP6 and the secondary windings of the transformers T5 and T7, and a loop is formed by the discharge tubes LP7 and LP8 and the secondary windings of the transformers T6 and T8. ing.

  According to such a configuration, the current flowing in each loop is made uniform, and the primary windings of the transformers T7 and T8 are connected in series, so that the current flowing in each discharge tube belonging to both loops is also It is made uniform. That is, the brightness of the discharge tube becomes uniform. Further, since the secondary winding of the transformer and the discharge tube are alternately connected in series, the voltage does not accumulate during lighting. Further, the number of transformers is the same as the number of discharge tubes.

  Furthermore, the potential of the secondary winding of the transformer is stabilized by grounding the intermediate tap S2 of the secondary winding of the transformers T5 and T6 via a resistor. On the other hand, since it is in a floating state in terms of alternating current, floating differential drive is performed. In a balanced state, no current flows across the resistor, so there is little loss.

  Note that the transformers T7 and T8 may be those having an intermediate tap on the secondary winding side, and the intermediate tap may be grounded through a resistor. This stabilizes the potential on the secondary winding side of the transformer.

4). Embodiment 4
FIG. 5 shows a discharge tube driving circuit 40 according to a fourth embodiment of the present invention. The discharge tube driving circuit 40 in FIG. 5 includes an AC power supply V6, transformers T9 to T12, discharge tubes LP9 to LP12, and resistors R7 and R8. The AC power supply V6 includes terminals P1 and P2 of the primary winding of the transformer T9, terminals P1 and P2 of the primary winding of the transformer T10, a terminal P1 of the primary winding of the transformer T11, and a terminal of the primary winding of the transformer T12. Connected to P2. Further, a terminal P2 of the primary winding of the transformer T11 and a terminal P1 of the primary winding of the transformer T12 are connected. That is, the primary winding of the transformer T9 and the primary winding of the transformer T10 are in parallel. The primary winding of the transformer T11 and the primary winding of the transformer T12 are connected in series. Note that the transformer T9 and the transformer T10, and the transformer T11 and the transformer T12 are connected to the AC power supply V6 so as to be in reverse phase. That is, the discharge tube is differentially driven. The transformers T11 and T12 are of the type having an intermediate tap S2 on the secondary winding side. The intermediate tap S2 of the secondary winding of the transformer T11 is grounded via a high-resistance resistor R7, and the transformer T12 The intermediate tap S2 of the secondary winding is grounded through a high-resistance resistor R8. The difference from FIG. 4 is that the position of the transformer having the intermediate tap S2 is not the left side but the right side.

  The first terminal of the discharge tube LP9 is connected to the terminal S2 of the secondary winding of the transformer T9, and the second terminal of the discharge tube LP9 is connected to the terminal S1 of the secondary winding of the transformer T11. . Further, the first terminal of the discharge tube LP10 is connected to the terminal S1 of the secondary winding of the transformer T9, and the second terminal of the discharge tube LP10 is connected to the terminal S3 of the secondary winding of the transformer T11. . Similarly, the first terminal of the discharge tube LP11 is connected to the terminal S2 of the secondary winding of the transformer T10, and the second terminal of the discharge tube LP11 is connected to the terminal S1 of the secondary winding of the transformer T12. The The first terminal of the discharge tube LP12 is connected to the terminal S1 of the secondary winding of the transformer T10, and the second terminal of the discharge tube LP12 is connected to the terminal S3 of the secondary winding of the transformer T12. . Thus, a loop is formed by the discharge tubes LP9 and LP10 and the secondary windings of the transformers T9 and T11, and a loop is formed by the discharge tubes LP11 and LP12 and the secondary windings of the transformers T10 and T12. ing.

  According to such a configuration, the current flowing in each loop is made uniform, and the primary windings of the transformers T11 and T12 are connected in series, so that the current flowing in each discharge tube belonging to both loops is also It is made uniform. That is, the brightness of the discharge tube becomes uniform. Further, since the transformer and the discharge tube are alternately connected in series, the voltage does not accumulate during lighting. Further, the number of transformers is the same as the number of discharge tubes.

  Further, the potential of the secondary winding of the transformer is stabilized by grounding the intermediate tap S2 of the secondary winding of the transformers T11 and T12 via a resistor. On the other hand, since it is in a floating state in terms of alternating current, floating differential drive is performed. In a balanced state, no current flows across the resistor, so there is little loss.

5. Embodiment 5
FIG. 6 shows a discharge tube driving circuit 50 according to a fifth embodiment of the present invention. The discharge tube driving circuit 50 of FIG. 6 includes an AC power source V7, a transformer T13 having an intermediate tap S2 on the secondary winding side, ordinary transformers T14 and T15, discharge tubes LP13 to LP16, and a resistor R9. . The AC power supply V7 is connected to the terminals P1 and P2 of the primary winding of the transformer T13, the terminal P2 of the primary winding of the transformer T14, and the terminal P1 of the primary winding of the transformer T15. Further, the primary winding terminal P1 of the transformer T14 and the primary winding terminal P2 of the transformer T15 are also connected. That is, the primary winding of the transformer T14 and the primary winding of the transformer T15 are connected in series. In addition, the transformer T13, the transformer T14, and the transformer T15 are connected to the AC power supply V7 so as to be in reverse phase. That is, the discharge tube is differentially driven.

  The first terminal of the discharge tube LP13 is connected to the terminal S1 of the secondary winding of the transformer T13, and the second terminal of the discharge tube LP13 is connected to the terminal S2 of the secondary winding of the transformer T14. . The first terminal of the discharge tube LP14 is connected to the terminal S3 of the secondary winding of the transformer T13, and the second terminal of the discharge tube LP14 is connected to the terminal S1 of the secondary winding of the transformer T14. . Similarly, the first terminal of the discharge tube LP15 is connected to the terminal S1 of the secondary winding of the transformer T13, and the second terminal of the discharge tube LP15 is connected to the terminal S2 of the secondary winding of the transformer T15. The The first terminal of the discharge tube LP16 is connected to the terminal S3 of the secondary winding of the transformer T13, and the second terminal of the discharge tube LP16 is connected to the terminal S1 of the secondary winding of the transformer T15. . Thus, a loop is formed by the discharge tubes LP13 and LP14 and the secondary windings of the transformers T13 and T14, and a loop is formed by the discharge tubes LP15 and LP16 and the secondary windings of the transformers T13 and T15. ing. Further, the intermediate tap S2 of the secondary winding of the transformer T13 is grounded via a high-resistance resistor R9.

  The discharge tube driving circuit 50 shown in FIG. 6 is a circuit in which the transformer on the left side of FIG. 4 is shared, and the number of transformers is (discharge tube number / 2 + 1), which is reduced. However, a transformer larger than the transformer T5 is required for the transformer T13. The other parts have almost the same characteristics as in the third embodiment. That is, the current flowing in each loop belonging to both loops is made uniform, and further, the primary windings of the transformers T14 and T15 are connected in series, so that the current flowing in each discharge tube is also made uniform. That is, the brightness of the discharge tube becomes uniform. Further, since the transformer and the discharge tube are alternately connected in series, the voltage does not accumulate during lighting.

  Furthermore, the potential of the secondary winding of the transformer is stabilized by grounding the intermediate tap S2 of the secondary winding of the transformer T13 via the high-resistance resistor R9. On the other hand, since it is in a floating state in terms of alternating current, floating differential drive is performed. In a balanced state, no current flows across the resistor, so there is little loss.

  Note that the transformers T14 and T15 may be those having an intermediate tap on the secondary winding side, and the intermediate tap may be grounded via a resistor. This stabilizes the potential on the secondary winding side of the transformer.

6). Embodiment 6
FIG. 7 shows a discharge tube driving circuit 60 according to a sixth embodiment of the present invention. The discharge tube driving circuit 60 in FIG. 7 includes an AC power supply V8, transformers T16 to T19, discharge tubes LP17 to LP20, and a resistor R10. The AC power supply V8 includes terminals P1 and P2 of the primary winding of the transformer T16, terminals P1 and P2 of the primary winding of the transformer T17, terminals P1 and P2 of the primary winding of the transformer T18, and a primary winding of the transformer T19. Are connected to the terminals P1 and P2. That is, the primary windings of all the transformers T16 to T19 are in parallel with the AC power supply V8.

  The first terminal of the discharge tube LP17 is connected to the terminal S2 of the secondary winding of the transformer T16, and the second terminal of the discharge tube LP17 is connected to the terminal S3 of the secondary winding of the transformer T19. . Thus, when the discharge tubes LP17 to LP20 are arranged in parallel and the transformers are arranged on the left and right sides of the discharge tube, the secondary windings of the diagonal transformers T16 and T19 are connected to each other through the discharge tube. . The first terminal of the discharge tube LP18 is connected to the terminal S1 of the secondary winding of the transformer T16, and the second terminal of the discharge tube LP18 is connected to the terminal S2 of the secondary winding of the transformer T18. . Similarly, the first terminal of the discharge tube LP19 is connected to the terminal S1 of the secondary winding of the transformer T18, and the second terminal of the discharge tube LP19 is connected to the terminal S2 of the secondary winding of the transformer T17. The Further, the first terminal of the discharge tube LP20 is connected to the terminal S1 of the secondary winding of the transformer T17, and the second terminal of the discharge tube LP20 is connected to the terminal S1 of the secondary winding of the transformer T19. . In this way, the discharge tube LP17, the secondary winding of the transformer T16, the discharge tube LP18, the secondary winding of the transformer T18, the discharge tube LP19, the secondary winding of the transformer T17, and the discharge tube LP20 Since the secondary winding of the transformer T19 is connected in series and the secondary winding of the transformer T19 and the discharge tube LP17 are connected, these circuit elements form a loop. Further, the discharge tube and the secondary winding of the transformer are connected alternately. The intermediate tap S2 of the secondary winding of the transformer T19 is grounded via a high resistance resistor R10.

  In addition, the primary windings of the transformers T16 to T19 and the AC power supply V8 and the secondary windings of the transformers T16 to T19 are applied so that a reverse polarity voltage is applied to both ends of the discharge tubes LP17 to LP20. The discharge tubes LP17 to LP20 are connected. Further, voltages having different polarities are alternately applied to the right terminals of the discharge tubes LP17 to LP20, and similarly, voltages having different polarities are alternately applied to the left terminals of the discharge tubes LP17 to LP20.

  In the present embodiment, the number of transformers is four with respect to the number of transformers, and the number of transformers is not increased compared to the number of discharge tubes. In addition, the discharge tube is connected in series on the secondary side of the transformer, but since the transformer secondary winding and discharge tube are alternately connected in series, the accumulation of voltage is minimal during lighting. Is suppressed. Since opposite polarity voltages are applied to both ends of the discharge tube, and the polarity of the discharge tubes arranged adjacent to each other is also reversed, there is an effect that noise is hardly generated. Further, the brightness of each discharge tube is not varied.

  Furthermore, since the intermediate tap S2 of the secondary winding of the transformer T19 is DC-grounded via a resistor, the potential on the secondary winding side of the transformer is stabilized. On the other hand, since it is in a floating state in terms of alternating current, floating differential drive is performed. That is, since current does not flow in earnest unless the two places where the high voltage is applied are touched, it is difficult to get an electric shock and safety is high. In a balanced state, almost no current flows through both ends of the resistor, so there is little loss.

  In the example of FIG. 7, an example in which only one place is grounded via the high-resistance resistor R10 in the closed loop formed by the secondary winding of the transformer and the discharge tube is shown, but as shown in FIG. In addition, a transformer T20 having an intermediate tap on the secondary winding side is used in place of the transformer T17, and the intermediate tap S2 of the secondary winding of the transformer T20 is grounded via a high-resistance resistor R11. The circuit 65 may be adopted. In this way, the potential in the closed loop becomes more stable. More preferably, all the transformers are changed to a type having an intermediate tap, and the intermediate tap is grounded through a resistor.

7). Embodiment 7
FIG. 9 shows a discharge tube driving circuit 70 (only the left half excluding the discharge tube) according to the seventh embodiment of the present invention. A discharge tube driving circuit 70 in FIG. 9 includes transformers T21 and T22, resistors R12 to R15, diodes D10 to D14, an inverter circuit 71 including an inverter power supply and a control circuit for the inverter power supply, transformers T21 and T22, and the like. Detection circuit 72 for detecting the maximum voltage on the primary winding side of the transformer and outputting a detection signal to the inverter circuit 71, and detecting the imbalance of the current flowing in the secondary winding side of the transformer such as transformers T21 and T22 And an unbalance detection circuit 73 that outputs an unbalance detection signal to the inverter circuit 71. The transformer T21 has a primary winding having terminals P1 and P2, and a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown) and terminals S2 and S3 as intermediate taps. Similarly, the transformer T22 has a primary winding having terminals P1 and P2, and a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown) and terminals S2 and S3 as intermediate taps. .

  A terminal P1 of the primary winding of the transformer T21 is connected to one end of the inverter circuit 71, and a terminal P2 of the primary winding of the transformer T22 is connected to the other end of the inverter circuit 71. The terminal P2 of the primary winding of the transformer T21 is connected to the anode of the diode D1 and the terminal P1 of the primary winding of the transformer T22. The terminal P1 of the primary winding of the transformer T22 is connected to the anode of the diode D10 and the terminal P2 of the primary winding of the transformer T21. The cathode of the diode D10 is connected to the voltage detection circuit 72 together with the cathode (not shown) of the diode connected to the primary winding of the transformer on the right side of the discharge tube. The cathode of the diode connected to the primary winding of the transformer on the right side of the discharge tube is connected to the voltage detection circuit 72 via the terminal 1. In this way, the maximum voltage of the voltage on the primary winding side of the transformer included in the discharge tube driving circuit 70 is detected by the voltage detection circuit 72. The voltage detection circuit 72 is connected to the inverter circuit 71 and outputs a detection signal corresponding to the detected maximum voltage to the inverter circuit 71. The inverter circuit 71 may adjust the output of the inverter circuit 71 according to the detection signal, or may stop the output of the inverter circuit 71 in order to protect the discharge tube driving circuit 70. If the output of the inverter circuit 71 is stopped, the discharge tube driving circuit 70 stops operating.

  On the other hand, the terminal S1 of the first secondary winding of the transformer T21 is connected to one end of a first discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T21 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R12. The other end of the resistor R12 is connected to one end of the resistor R13, and the other end of the resistor R13 is grounded. A terminal S4 of the second secondary winding of the transformer T21 is connected to one end of a second discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T21 is grounded via the resistors R12 and R13. In addition, a closed loop is formed by the secondary winding of the transformer T21, the first and second discharge tubes, and the secondary winding of the right transformer (not shown). The connection point between the resistor R12 and the resistor R13 is connected to the cathode of the diode D11 and the anode of the diode D12. The anode of the diode D11 is connected to the same configuration on the right side of the discharge tube via the terminal 2. Has been. The cathode of the diode D12 is connected to the same configuration on the right side of the discharge tube via the terminal 3.

  Further, the terminal S1 of the first secondary winding of the transformer T22 is connected to one end of a third discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T22 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R14. The other end of the resistor R14 is connected to one end of the resistor R15, and the other end of the resistor R15 is grounded. A terminal S4 of the second secondary winding of the transformer T22 is connected to one end of a fourth discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T22 is grounded via the resistors R14 and R15. In addition, a closed loop is formed by the secondary winding of the transformer T22, the third and fourth discharge tubes, and the secondary winding of the right transformer (not shown). The cathode of the diode D13 and the anode of the diode D14 are connected to the connection point between the resistor R14 and the resistor R15.

  The anode of the diode D13 is connected to the same configuration on the right side of the discharge tube via the terminal 4, and is connected to the anode of the diode D11 and the terminal 2. The cathode of the diode D14 is connected to the same configuration on the right side of the discharge tube via the terminal 5, and is connected to the cathode of the diode D12 and the terminal 3. As described above, the unbalance detection circuit 73 has a current flowing through the resistors R12 and R13, the resistors R14 and R15, etc., that is, the currents, via the diodes D11 to D14 and the diode on the right side of the discharge tube having the same configuration. Is detected. When the balance is achieved, almost no current flows. Therefore, if an unbalance voltage is detected by the unbalance detection circuit 73, an abnormality has occurred in one of the discharge tubes. The unbalance detection circuit 73 is connected to the inverter circuit 71, and outputs an unbalance detection signal corresponding to the detected unbalance voltage to the inverter circuit 71. When the inverter circuit 71 detects an unbalance detection signal indicating an abnormality during normal operation, the inverter circuit 71 stops the output of the inverter circuit 71 in order to protect the discharge tube driving circuit 70. If the output of the inverter circuit 71 is stopped, the discharge tube driving circuit 70 stops operating.

  Further, when one of the discharge tubes is not lit at the time of start-up, an unbalanced voltage is generated although it is not abnormal. Also at this time, since the voltage concentrates on the unlit side, an overvoltage occurs on one side of the transformer, which may cause a spark and damage the transformer and surrounding circuits. Therefore, as described above, an unbalance detection signal is fed back from the unbalance detection circuit 73 to the inverter circuit 71, and the inverter circuit 71 automatically adjusts the output voltage of the inverter circuit 71 so as not to become an overvoltage.

  Various control methods in the inverter circuit 71 are possible. For example, a higher voltage signal is selected from the unbalance detection signal from the unbalance detection circuit 73 and the detection signal from the voltage detection circuit 72, and the output voltage of the inverter circuit 71 is adjusted based on the selected signal. Or the output may be stopped. In the unbalance detection circuit 73, the voltage detection circuit 72, or the inverter circuit 71, at least one of the unbalance detection signal from the unbalance detection circuit 73 and the detection signal from the voltage detection circuit 72 is appropriate for comparison. Weighting is performed using various coefficients.

  Further, in the inverter circuit 71, the unbalance detection signal of the unbalance detection circuit 73 and the detection signal of the voltage detection circuit 72 are combined to generate a new control signal, whereby each extreme on the secondary winding side of the transformer is generated. The potential of the child may be estimated and used for protection control of withstand voltage against ground potential.

8). Embodiment 8
FIG. 10 shows a discharge tube driving circuit 80 (only the left half excluding the discharge tube) according to the eighth embodiment of the present invention. A discharge tube driving circuit 80 of FIG. 10 includes transformers T23 and T24, resistors R16 to R19, diodes D15 to D20, an inverter circuit 81 including an inverter power supply and a control circuit for the inverter power supply, transformers T23 and T24, and the like. Detects the maximum voltage on the tertiary winding side of the transformer and outputs a detection signal to the inverter circuit 81, and detects the imbalance of the current flowing on the secondary winding side of the transformer such as transformers T23 and T24 And an unbalance detection circuit 83 that outputs an unbalance detection signal to the inverter circuit 81. The transformer T23 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and terminals P3 and P4. Having a tertiary winding. Similarly, the transformer T24 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and a terminal. And a tertiary winding having P3 and P4. The tertiary winding is provided to estimate the voltage generated on the secondary winding side.

  A terminal P1 of the primary winding of the transformer T23 is connected to one end of the inverter circuit 81, and a terminal P2 of the primary winding of the transformer T24 is connected to the other end of the inverter circuit 81. A terminal P2 of the primary winding of the transformer T23 is connected to a terminal P1 of the primary winding of the transformer T24. The terminal P3 of the tertiary winding of the transformer T23 is grounded, and the terminal P4 is connected to the anode of the diode D15. Similarly, the terminal P3 of the tertiary winding of the transformer T24 is grounded, and the terminal P4 is connected to the anode of the diode D16. The cathodes of the diodes D15 and D16 are connected to the voltage detection circuit 82 together with the cathode (not shown) of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube. The cathode of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube is connected to the voltage detection circuit 82 via the terminal 6. As described above, the voltage detection circuit 82 detects the maximum voltage among the voltages on the tertiary winding side of the transformer included in the discharge tube driving circuit 80. The voltage detection circuit 82 is connected to the inverter circuit 81, and outputs a detection signal corresponding to the detected maximum voltage to the inverter circuit 81. The inverter circuit 81 may adjust the output of the inverter circuit 81 according to the detection signal, or may stop the output of the inverter circuit 81 in order to protect the discharge tube driving circuit 80. If the output of the inverter circuit 81 is stopped, the discharge tube driving circuit 80 stops operating.

  On the other hand, the terminal S1 of the first secondary winding of the transformer T23 is connected to one end of a first discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T23 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R16. The other end of the resistor R16 is connected to one end of the resistor R17, and the other end of the resistor R17 is grounded. A terminal S4 of the second secondary winding of the transformer T23 is connected to one end of a second discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T23 is grounded via the resistors R16 and R17. Further, a closed loop is configured by the secondary winding of the transformer T23, the first and second discharge tubes, and the secondary winding of the right transformer (not shown). The connection point of the resistor R16 and the resistor R17 is connected to the cathode of the diode D17 and the anode of the diode D18. The anode of the diode D17 is connected to the same configuration on the right side of the discharge tube via the terminal 7. Has been. The cathode of the diode D18 is connected to the same configuration on the right side of the discharge tube via the terminal 8.

  Further, the terminal S1 of the first secondary winding of the transformer T24 is connected to one end of a third discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T24 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R18. The other end of the resistor R18 is connected to one end of the resistor R19, and the other end of the resistor R19 is grounded. A terminal S4 of the second secondary winding of the transformer T24 is connected to one end of a fourth discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T24 is grounded via the resistors R18 and R19. In addition, a closed loop is formed by the secondary winding of the transformer T24, the third and fourth discharge tubes, and the secondary winding of the right transformer (not shown). The cathode of the diode D19 and the anode of the diode D20 are connected to the connection point between the resistor R18 and the resistor R19.

  The anode of the diode D19 is connected to the same configuration on the right side of the discharge tube via the terminal 9, and is connected to the anode of the diode D17 and the terminal 7. The cathode of the diode D20 is connected to the same configuration on the right side of the discharge tube via the terminal 10, and is connected to the cathode of the diode D18 and the terminal 8. As described above, the unbalance detection circuit 83 has the currents flowing through the resistors R16 and R17, the resistors R18 and R19, etc., that is, the currents via the diodes D17 to D20 and the diode on the right side of the discharge tube having the same configuration. Is detected. When the balance is established, almost no current flows. Therefore, if an unbalance voltage is detected by the unbalance detection circuit 83, an abnormality has occurred in one of the discharge tubes. The unbalance detection circuit 83 is connected to the inverter circuit 81, and outputs an unbalance detection signal corresponding to the detected unbalance voltage to the inverter circuit 81. When the inverter circuit 81 detects an unbalance detection signal indicating an abnormality during normal operation, the inverter circuit 81 stops the output of the inverter circuit 81 in order to protect the discharge tube driving circuit 80. If the output of the inverter circuit 81 is stopped, the discharge tube driving circuit 80 stops operating.

  As a control method of the inverter circuit 81, a method similar to that of the inverter circuit 71 can be employed.

9. Embodiment 9
FIG. 11 shows a discharge tube driving circuit 90 (only the left half excluding the discharge tube) according to the ninth embodiment of the present invention. A discharge tube driving circuit 90 in FIG. 11 includes transformers T25 and T26, resistors R20 to R27, diodes D21 to D24, an inverter circuit 91 including an inverter power supply and a control circuit for the inverter power supply, transformers T25 and T26, and the like. And a voltage detection circuit 92 for detecting a maximum voltage on the tertiary winding side of the transformer and outputting a detection signal to the inverter circuit 91. The transformer T25 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and terminals P3 and P4. A tertiary winding. Similarly, the transformer T26 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and a terminal And a tertiary winding having P3 and P4.

  A terminal P1 of the primary winding of the transformer T25 is connected to one end of the inverter circuit 91, and a terminal P2 of the primary winding of the transformer T26 is connected to the other end of the inverter circuit 91. A terminal P2 of the primary winding of the transformer T25 is connected to a terminal P1 of the primary winding of the transformer T26. The terminal P3 of the tertiary winding of the transformer T25 is connected to the anode of the diode D21 and one end of the resistor R24. A terminal P4 of the tertiary winding of the transformer T25 is connected to the anode of the diode D22 and one end of the resistor R25. For example, the resistance value of the resistor R24 and the resistance value of the resistor R25 are the same. The other end of the resistor R24 and the other end of the resistor R25 are connected to a connection point between the resistor R20 and the resistor R21. Similarly, the terminal P3 of the tertiary winding of the transformer T26 is connected to the anode of the diode D23 and one end of the resistor R26. The terminal P4 of the tertiary winding of the transformer T26 is connected to the anode of the diode D24 and one end of the resistor R27. For example, the resistance value of the resistor R26 and the resistance value of the resistor R27 are the same. The other end of the resistor R26 and the other end of the resistor R27 are connected to a connection point between the resistors R22 and R23.

  The cathodes of the diodes D21 to D24 are connected to the voltage detection circuit 92 together with the cathode (not shown) of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube. The cathode of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube is connected to the voltage detection circuit 92 via the terminal 11. As described above, the voltage detection circuit 92 detects the maximum voltage among the voltages on the tertiary winding side of the transformer included in the discharge tube driving circuit 90. The voltage detection circuit 92 is connected to the inverter circuit 91, and outputs a detection signal corresponding to the detected maximum voltage to the inverter circuit 91. The inverter circuit 91 may adjust the output of the inverter circuit 91 according to the detection signal, or may stop the output of the inverter circuit 91 in order to protect the discharge tube driving circuit 90. If the output of the inverter circuit 91 is stopped, the discharge tube driving circuit 90 is stopped.

  On the other hand, the terminal S1 of the first secondary winding of the transformer T25 is connected to one end of a first discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T25 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R20. The other end of the resistor R20 is connected to one end of the resistor R21, and the other end of the resistor R21 is grounded. A terminal S4 of the second secondary winding of the transformer T25 is connected to one end of a second discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T25 is grounded via the resistors R20 and R21. The secondary winding of the transformer T25, the first and second discharge tubes, and the secondary winding of the right transformer (not shown) form a closed loop.

  Further, the terminal S1 of the first secondary winding of the transformer T26 is connected to one end of a third discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T26 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R22. The other end of the resistor R22 is connected to one end of the resistor R23, and the other end of the resistor R23 is grounded. A terminal S4 of the second secondary winding of the transformer T26 is connected to one end of a fourth discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T26 is grounded via the resistors R22 and R23. The secondary winding of the transformer T26, the third and fourth discharge tubes, and the secondary winding of the right transformer (not shown) form a closed loop.

  The potential at the terminal S1 of the secondary winding of the transformer T26 is Va, and the potential at the terminal S4 is Vb. On the other hand, it is assumed that a voltage of (Va′−Vb ′) is generated between the terminals P3 and P4 of the tertiary winding from the winding ratio of the secondary winding and the tertiary winding. Further, by adjusting the ratio of the resistance value of the resistor R22 and the resistance value of the resistor R23 to the winding ratio of the secondary winding and the tertiary winding, the connection point between the resistor R22 and the resistor R23 is ( A voltage of Va′−Vb ′) / 2 is generated. If the resistance value of the resistor R26 is equal to the resistance value of the resistor R27, the calculation of (Va '+ Vb') / 2+ (Va'-Vb ') / 2 is performed, and the anode of the diode D23 The potential Va ′ is generated, and the calculation of (Va ′ + Vb ′) / 2− (Va′−Vb ′) / 2 is performed, and the potential Vb ′ is generated at the anode of the diode D24. However, Va ′ and Vb ′ are half-wave rectified by the diodes D23 and D24. Thus, the voltage detection circuit 92 detects the maximum value of the potential corresponding to the terminal of the secondary winding of the transformer. The voltage detection circuit 92 outputs a detection signal corresponding to the detected voltage to the inverter circuit 91. The inverter circuit 91 adjusts the output voltage according to the detection signal, and stops the output as necessary. If the output of the inverter circuit 91 is stopped, the discharge tube driving circuit 90 is stopped.

10. Embodiment 10
FIG. 12 shows a discharge tube driving circuit 100 (only the left half excluding the discharge tube) according to the tenth embodiment of the present invention. A discharge tube driving circuit 100 in FIG. 12 includes transformers T27 and T28, resistors R28 to R31, diodes D25 to D28, an inverter circuit 101 including an inverter power supply and a control circuit for the inverter power supply, transformers T27 and T28, and the like. And a voltage detection circuit 102 that detects a maximum voltage on the tertiary winding side of the transformer and outputs a detection signal to the inverter circuit 101. The transformer T27 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and terminals P3 and P5. And a tertiary winding having an intermediate tap P4. Similarly, the transformer T28 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and a terminal It has a tertiary winding with P3 and P5 and an intermediate tap P4.

  A terminal P1 of the primary winding of the transformer T27 is connected to one end of the inverter circuit 101, and a terminal P2 of the primary winding of the transformer T28 is connected to the other end of the inverter circuit 101. A terminal P2 of the primary winding of the transformer T27 is connected to a terminal P1 of the primary winding of the transformer T28. The terminal P3 of the tertiary winding of the transformer T27 is connected to the anode of the diode D25. A terminal P5 of the tertiary winding of the transformer T27 is connected to the anode of the diode D26. The intermediate tap P4 of the tertiary winding of the transformer T27 is connected to the connection point between the resistor R28 and the resistor R29. Similarly, the terminal P3 of the tertiary winding of the transformer T28 is connected to the anode of the diode D27. The terminal P5 of the tertiary winding of the transformer T28 is connected to the anode of the diode D28. An intermediate tap P4 of the tertiary winding of the transformer T28 is connected to a connection point between the resistors R30 and R31.

  The cathodes of the diodes D25 to D28 are connected to the voltage detection circuit 102 together with the cathode (not shown) of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube. The cathode of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube is connected to the voltage detection circuit 102 via the terminal 12. Thus, the voltage detection circuit 102 detects the maximum voltage among the voltages on the tertiary winding side of the transformer included in the discharge tube driving circuit 100. The voltage detection circuit 102 is connected to the inverter circuit 101, and outputs a detection signal corresponding to the detected maximum voltage to the inverter circuit 101. The inverter circuit 101 may adjust the output of the inverter circuit 101 according to the detection signal, or may stop the output of the inverter circuit 101 in order to protect the discharge tube driving circuit 100. If the output of the inverter circuit 101 is stopped, the discharge tube driving circuit 100 stops operating.

  On the other hand, the terminal S1 of the first secondary winding of the transformer T27 is connected to one end of a first discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T27 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R28. The other end of the resistor R28 is connected to one end of the resistor R29, and the other end of the resistor R29 is grounded. A terminal S4 of the second secondary winding of the transformer T27 is connected to one end of a second discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T27 is grounded via the resistors R28 and R29. The secondary winding of the transformer T27, the first and second discharge tubes, and the secondary winding of the right transformer (not shown) form a closed loop.

  Further, the terminal S1 of the first secondary winding of the transformer T28 is connected to one end of a third discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T28 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R30. The other end of the resistor R30 is connected to one end of the resistor R31, and the other end of the resistor R31 is grounded. A terminal S4 of the second secondary winding of the transformer T28 is connected to one end of a fourth discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T28 is grounded via the resistors R30 and R31. The secondary winding of the transformer T28, the third and fourth discharge tubes, and the secondary winding of the right transformer (not shown) form a closed loop.

  The potential at the terminal S1 of the secondary winding of the transformer T28 is Va, and the potential at the terminal S4 is Vb. On the other hand, it is assumed that a voltage of (Va′−Vb ′) is generated between the terminals P3 and P5 of the tertiary winding from the winding ratio of the tertiary winding to the secondary winding. Furthermore, by matching the ratio of the resistance value of the resistor R30 and the resistance value of the resistor R31 to the winding ratio of the tertiary winding and the secondary winding, the connection point between the resistors R30 and R31 is ( A potential of Va ′ + Vb ′) / 2 is generated. Since the connection point between the resistor R30 and the resistor R31 is connected to the intermediate tap P4 of the tertiary winding of the transformer T28, the potential of the intermediate tap P4 becomes (Va ′ + Vb ′) / 2, and the terminal of the tertiary winding Since the voltage between P3 and P5 is (Va′−Vb ′), the potential of the terminal P3 of the tertiary winding is Va ′, and the potential of the terminal P5 of the tertiary winding is Vb ′. Specifically, the calculation of (Va ′ + Vb ′) / 2+ (Va′−Vb ′) / 2 is performed, and a potential Va ′ is generated at the anode of the diode D27, and similarly (Va ′ + Vb ′). The calculation of / 2− (Va′−Vb ′) / 2 is performed, and a potential Vb ′ is generated at the anode of the diode D28. However, Va ′ and Vb ′ are half-wave rectified by the diodes D27 and D28. In this way, the voltage detection circuit 102 detects the maximum value of the potential corresponding to the terminal of the secondary winding of the transformer. The voltage detection circuit 102 outputs a detection signal corresponding to the detected voltage to the inverter circuit 101. The inverter circuit 101 adjusts the output voltage according to the detection signal, and stops the output as necessary. If the output of the inverter circuit 101 is stopped, the discharge tube driving circuit 100 stops operating.

11. Embodiment 11
FIG. 13 shows a discharge tube driving circuit 110 (only the left half excluding the discharge tube) according to the eleventh embodiment of the present invention. The discharge tube driving circuit 110 in FIG. 13 includes transformers T29 and T30, resistors R32 to R35, diodes D29 to D36, an inverter circuit 111 including an inverter power supply and a control circuit for the inverter power supply, transformers T29 and T30, and the like. The third differential voltage common frequency correction and absolute value detection circuit 112 that detects the maximum voltage on the tertiary winding side of the transformer and outputs a detection signal, and the current that flows on the secondary winding side of the transformer such as the transformers T29 and T30 An unbalance voltage absolute value detection circuit 113 that detects an unbalance of the output and outputs an unbalance detection signal, an output of the third-order differential voltage common frequency correction and absolute value detection circuit 112, and an output of the unbalance voltage absolute value detection circuit 113 And an adder circuit 114 for adding. The transformer T29 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and terminals P3 and P4. A tertiary winding. Similarly, the transformer T30 includes a primary winding having terminals P1 and P2, a secondary winding having terminals S1 and S4 connected to a discharge tube (not shown), and terminals S2 and S3 as intermediate taps, and a terminal And a tertiary winding having P3 and P4. The tertiary winding is provided to estimate the voltage generated on the secondary winding side.

  A terminal P1 of the primary winding of the transformer T29 is connected to one end of the inverter circuit 111, and a terminal P2 of the primary winding of the transformer T30 is connected to the other end of the inverter circuit 111. A terminal P2 of the primary winding of the transformer T29 is connected to a terminal P1 of the primary winding of the transformer T30. The terminal P3 of the tertiary winding of the transformer T29 is connected to the terminal P3 of the tertiary winding of the transformer T30, and the terminal P3 (not shown) of the tertiary winding of the transformer on the right side of the discharge tube is also connected via the terminal 17. And connected to the first terminal of the third-order differential voltage common frequency correction and absolute value detection circuit 112.

  Further, the terminal P4 of the tertiary winding of the transformer T29 is connected to the anode of the diode D34 and the cathode of the diode D33. Similarly, the terminal P4 of the tertiary winding of the transformer T30 is connected to the anode of the diode D36 and the cathode of the diode D35. The cathodes of the diodes D34 and D36 are connected to a tertiary differential voltage common frequency correction and absolute value detection circuit 112 together with a diode cathode (not shown) connected to the tertiary winding of the transformer on the right side of the discharge tube. . The cathode of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube is connected to the second terminal of the tertiary differential voltage common frequency correction and absolute value detection circuit 112 via the terminal 19. The anodes of the diodes D33 and D35 are connected to the tertiary differential voltage common frequency correction and absolute value detection circuit 112 together with the anode (not shown) of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube. . The anode of the diode connected to the tertiary winding of the transformer on the right side of the discharge tube is connected to the third terminal of the tertiary differential voltage common frequency correction and absolute value detection circuit 112 via the terminal 18.

  As described above, the maximum voltage of the positive voltage on the tertiary winding side of the transformer included in the discharge tube driving circuit 110 and the maximum voltage among the negative voltages and the intermediate REF voltage generated at the terminal P3 of the tertiary winding are the tertiary difference. The dynamic voltage common frequency correction and absolute value detection circuit 112 detects the frequency. The tertiary differential voltage common frequency correction and absolute value detection circuit 112 performs frequency correction on the differential voltage of the tertiary winding based on the input voltage, and adds the maximum absolute value signal of the tertiary winding voltage. To 114.

  On the other hand, the terminal S1 of the first secondary winding of the transformer T29 is connected to one end of a first discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T29 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R32. The other end of the resistor R32 is connected to one end of the resistor R33, and the other end of the resistor R33 is grounded. A terminal S4 of the second secondary winding of the transformer T29 is connected to one end of a second discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T29 is grounded via the resistors R32 and R33. In addition, a closed loop is formed by the secondary winding of the transformer T29, the first and second discharge tubes, and the secondary winding of the right transformer (not shown). The connection point between the resistor R32 and the resistor R33 is connected to the cathode of the diode D29 and the anode of the diode D30. The anode of the diode D29 is connected to the same configuration on the right side of the discharge tube via the terminal 13. Has been. The cathode of the diode D30 is connected to the same configuration on the right side of the discharge tube via the terminal 14.

  Further, the terminal S1 of the first secondary winding of the transformer T30 is connected to one end of a third discharge tube (not shown). The terminal S2 of the first secondary winding of the transformer T30 is connected to the terminal S3 of the second secondary winding, and is further connected to one end of the resistor R34. The other end of the resistor R34 is connected to one end of the resistor R35, and the other end of the resistor R35 is grounded. A terminal S4 of the second secondary winding of the transformer T30 is connected to one end of a fourth discharge tube (not shown). Thus, the intermediate terminal of the secondary winding of the transformer T30 is grounded via the resistors R34 and R35. In addition, a closed loop is formed by the secondary winding of the transformer T30, the third and fourth discharge tubes, and the secondary winding of the right transformer (not shown). The connection point between the resistor R34 and the resistor R35 is connected to the cathode of the diode D31 and the anode of the diode D32.

  The anode of the diode D31 is connected to the same configuration on the right side of the discharge tube via the terminal 15, and is connected to the anode of the diode D29 and the terminal 13. The cathode of the diode D32 is connected to the same configuration on the right side of the discharge tube via the terminal 16, and is connected to the cathode of the diode D30 and the terminal 14. As described above, the unbalance voltage absolute value detection circuit 113 includes the diodes D29 to D32, and the current flowing in the resistors R32 and R33, the resistors R34 and R35, etc. through the diode on the right side of the discharge tube having the same configuration, That is, the unbalance voltage generated by the current is detected. When the balance is achieved, almost no current flows. Therefore, if an unbalance voltage is detected by the unbalance voltage absolute value detection circuit 113, an abnormality has occurred in one of the discharge tubes. The unbalance voltage absolute value detection circuit 113 detects the positive and negative maximum voltages, generates a maximum absolute value signal of the unbalance voltage, and outputs it to the adder circuit 114.

  The addition circuit 114 adds a control signal obtained by adding the maximum absolute value signal from the third-order differential voltage common frequency correction and absolute value detection circuit 112 and the maximum absolute value signal from the unbalance voltage absolute value detection circuit 113. Output to the inverter circuit 111. In this way, the control signal becomes a value close to the output voltage of the secondary winding, and the inverter circuit 111 automatically adjusts the output of the inverter circuit 111 to protect the discharge tube driving circuit 110 based on the control signal. Or stop. If the output of the inverter circuit 111 is stopped, the discharge tube driving circuit 110 stops operating.

  In the seventh to eleventh embodiments, the detection voltage in the primary winding or tertiary winding of the transformer and the unbalance voltage obtained by dividing the ground of the intermediate tap of the secondary winding are considered together. By performing feedback control of the inverter circuit, the discharge tube drive circuit as a whole can be operated stably.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, it is possible to use a circuit that combines a plurality of the above-described embodiments. For example, the grounding methods in the first and second embodiments can be mixed. It is also possible to use a circuit in which a circuit other than the circuit according to the present invention is combined with the circuit according to the present invention.

It is a figure which shows the example of a conventional circuit. (A) is a circuit diagram concerning a 1st embodiment of the present invention, and (b) is another circuit diagram concerning a 1st embodiment of the present invention. It is a circuit diagram concerning a 2nd embodiment of the present invention. It is a circuit diagram concerning a 3rd embodiment of the present invention. It is a circuit diagram concerning a 4th embodiment of the present invention. It is a circuit diagram concerning a 5th embodiment of the present invention. It is a circuit diagram concerning a 6th embodiment of the present invention. It is another circuit diagram concerning a 6th embodiment of the present invention. It is a circuit diagram concerning a 7th embodiment of the present invention. It is a circuit diagram concerning an 8th embodiment of the present invention. It is a circuit diagram concerning a 9th embodiment of the present invention. It is a circuit diagram concerning a 10th embodiment of the present invention. It is a circuit diagram concerning an 11th embodiment of the present invention.

Explanation of symbols

V AC power supply (or inverter)
LP discharge tube T transformer

Claims (12)

Have multiple transformers,
A secondary loop and two or more lamps in the plurality of transformers are connected in series to form a closed loop,
The primary windings of the plurality of transformers are connected to an AC power source,
A lamp driving circuit in which at least one point of the closed loop is grounded in a direct current manner. The lamp driving circuit according to claim 1, wherein the direct-current grounding of at least one point of the closed loop is performed via a resistor having a resistance value equal to or greater than a predetermined value.   2. The closed loop includes at least two or more portions to which the lamp is connected at a subsequent stage of the secondary winding when the circulation direction of the closed loop is defined in one direction. Lamp drive circuit.   The lamp driving circuit according to claim 1, wherein at least one of the lamps is disposed between each of the secondary windings in the closed loop. At least one of the transformers has an intermediate tap on the secondary winding side;
The lamp driving circuit according to claim 1, wherein at least one DC grounding of the closed loop is performed via the intermediate tap. Each of the plurality of transformers has an intermediate tap on the secondary winding side,
The lamp driving circuit according to claim 1, wherein the closed-loop DC grounding is performed via the intermediate tap. At least one of the transformers has an intermediate tap on the secondary winding side;
DC grounding of at least one point of the closed loop is performed via the intermediate tap,
The lamp driving circuit according to claim 1, further comprising a circuit that automatically adjusts or stops output of the driving voltage of the AC power supply by detecting an unbalanced voltage by dividing the ground of the intermediate tap and feeding it back. At least one of the transformers has an intermediate tap on the secondary winding side;
DC grounding of at least one point of the closed loop is performed via the intermediate tap,
Driving the AC power supply by performing feedback using the voltage of the primary winding of the transformer or the voltage of the voltage detecting tertiary winding and the unbalance voltage detected by dividing the ground of the intermediate tap together The lamp driving circuit according to claim 1, further comprising a circuit for automatically adjusting the voltage or stopping the output. At least one of the transformers has an intermediate tap on the secondary winding side;
DC grounding of at least one point of the closed loop is performed via the intermediate tap,
The weighted sum voltage of the maximum absolute value of the voltage of the primary winding of the transformer or the voltage of the tertiary winding for voltage detection and the maximum absolute value of the unbalance voltage detected by dividing the ground of the intermediate tap is fed back. The lamp drive circuit according to claim 1, further comprising: a circuit that automatically adjusts or stops output of the drive voltage of the AC power supply. At least one of the transformers has an intermediate tap on the secondary winding side;
DC grounding of at least one point of the closed loop is performed via the intermediate tap,
Feedback using both the weighted sum voltage and weighted difference voltage of the voltage of the primary winding of the transformer or the voltage of the voltage detecting tertiary winding and the unbalance voltage detected by dividing the ground of the intermediate tap. The lamp drive circuit according to claim 1, further comprising: a circuit that automatically adjusts or stops output of the drive voltage of the AC power supply by performing the above. A primary winding having first and second transformers connected to an AC power source;
A closed loop in which lamps are arranged in series between the secondary windings of the first and second transformers is configured,
The first and second transformers apply first and second voltages having different polarities to both ends of the lamp,
The lamp driving circuit according to claim 1, wherein the closed loop is grounded in a direct current manner in each of a line where the first voltage is generated and a line where the second voltage is generated. A primary winding having first and second transformers connected to an AC power source;
A closed loop in which lamps are arranged in series between the secondary windings of the first and second transformers is configured,
The first and second transformers apply first and second voltages having different polarities to both ends of the lamp,
An intermediate tap is provided in the secondary winding of the first and second transformers,
The lamp driving circuit according to claim 1, wherein the closed loop is grounded in a DC manner through the intermediate tap.

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