JP4752610B2 - Discharge tube lighting circuit and light source system - Google Patents

Description

  The present invention relates to a discharge tube lighting circuit for a discharge tube used as a light source for a liquid crystal display or the like and a light source system provided with the discharge tube lighting circuit.

  Liquid crystal displays (LCDs) such as liquid crystal televisions and liquid crystal monitors require a light source (backlight) that emits light from the back toward the liquid crystal. For such a backlight, a discharge tube such as a cold cathode fluorescent lamp (CCFL) is often used. Specifically, a plurality of discharge tubes are arranged along the horizontal direction of the display, and high frequency power is supplied to each discharge tube by a lighting circuit.

  For example, Japanese Patent Application Laid-Open No. 2004-335443 (Patent Document 1) significantly reduces the number of step-up transformers and control circuits by simultaneously lighting two or more discharge tubes with one step-up transformer. An inverter circuit for a multi-lamp lighting discharge tube for realizing low cost is disclosed.

  Furthermore, in recent years, it has been required to control light and darkness on a liquid crystal display in order to realize a more advanced display. That is, it is necessary to perform lighting control such as lighting only a specific discharge tube among a plurality of discharge tubes, or sequentially switching the discharge tubes to be lit.

Therefore, for example, Japanese Patent Laying-Open No. 2005-5059 (Patent Document 2) discloses a discharge tube lighting or the like for controlling the current flowing through the discharge tube to be almost constant in the case of a connection configuration without a discharge tube return line. An excited inverter circuit is disclosed.
JP 2004-335443 A JP 2005-5059 A

  In the backlight as described above, current control may be performed so that the current flowing through each discharge tube becomes a target value in order to make the light emission intensity of the entire light source uniform. In order to realize such current control, it is necessary to detect the current flowing through each discharge tube. For example, in the multi-lamp lighting discharge tube inverter circuit disclosed in Patent Document 1, the low voltage side of each discharge tube is grounded via a resistor, and a control signal is generated according to the amount of voltage drop generated in the resistor. The inverter circuit is controlled.

  By the way, with the recent increase in the size of liquid crystal displays, the discharge tubes themselves have become longer. For this reason, in the multi-lamp lighting discharge tube inverter circuit disclosed in Patent Document 1, the cable for transmitting the control signal must be long, and the control becomes unstable due to the influence of noise or the like. There was a problem.

  Further, in the separately excited inverter circuit for lighting a discharge tube disclosed in Patent Document 2, since the control is performed based on the voltage detected on the high voltage side of the discharge tube, there is a problem that the control signal is affected by noise or the like. Although it can be avoided, there is a problem in that the lighting control is limited to two discharge tube units that are close to each other.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a discharge tube lighting circuit and a light source system that can perform lighting control with a relatively high degree of freedom while avoiding the influence of noise. Is to provide.

  According to this invention, it is a discharge tube lighting circuit for lighting a plurality of discharge tubes. A discharge tube lighting circuit according to the present invention includes a power source unit that generates AC power for lighting a discharge tube, and a plurality of AC power sources that are boosted and supplied to one end of a corresponding discharge tube. A transformer and a short-circuit portion for short-circuiting the other ends of the plurality of discharge tubes are provided. Then, the power supply unit includes the first and second discharge tube groups each including at least one discharge tube among the plurality of discharge tubes, through the first transformer group corresponding to the first discharge tube group. An AC voltage is supplied to the discharge tube group, and an AC voltage having a polarity opposite to that of the AC voltage is supplied to the second discharge tube group via a second transformer group corresponding to the second discharge tube group. Composed.

  According to the present invention, an alternating voltage is supplied to the discharge tubes of the first discharge tube group, and an alternating voltage of the opposite polarity is supplied to the discharge tubes of the second discharge tube group. The ends are shorted together. Thereby, a current path from the discharge tube of the first discharge tube group to the discharge tube of the second discharge tube group is formed via the short-circuit portion. Therefore, when viewed from the power supply unit, the first and second discharge tube groups can be regarded as a single discharge tube, and a control signal can be generated at a position close to the power supply unit. At the same time, there are no restrictions on the discharge tubes selected as the first and second discharge tube groups, except for restrictions on the device configuration of the power supply unit.

  Therefore, it is possible to select the discharge tube to be lit with a relatively high degree of freedom while avoiding the influence of noise on the control signal.

  Preferably, the power supply unit includes a first AC voltage generation unit that generates a first AC voltage, a second AC voltage generation unit that generates a second AC voltage having a polarity opposite to that of the first AC voltage, And a selector configured to selectively connect the first AC voltage generator to the first transformer group and selectively connect the second AC voltage generator to the second transformer group.

  Preferably, the power supply unit includes an AC voltage generation unit that generates an AC voltage, and a selection unit configured to selectively connect the AC voltage generation unit to the first and second transformer groups. The transformer group boosts the AC voltage received from the AC voltage generator so as to have a polarity opposite to the boosted AC voltage supplied to the second discharge tube group by the second transformer group.

Preferably, the first and second discharge tube groups include the same number of discharge tubes.
Preferably, the power supply unit is configured to be capable of intermittently supplying an AC voltage supplied to the first and second discharge tube groups.

  Preferably, the power supply unit is configured to be able to change the voltage value of the AC voltage supplied to the first and second discharge tube groups.

  Moreover, according to this invention, it is a light source system provided with the above-mentioned discharge tube lighting circuit and a some discharge tube.

  According to the present invention, it is possible to realize a discharge tube lighting circuit and a light source system that can perform lighting control with a relatively high degree of freedom while avoiding the influence of noise.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a light source system 100 including a discharge tube lighting circuit 2 according to the first embodiment of the present invention.

  Referring to FIG. 1, light source system 100 according to the first embodiment of the present invention is mainly used as a backlight of a liquid crystal display (LCD), but is not limited to this application. The light source system 100 includes a discharge tube lighting circuit 2 and a discharge tube portion 4 that is connected to the discharge tube lighting circuit 2 and emits light. In the following description, the discharge tube portion 4 including eight discharge tubes is illustrated as an example. Moreover, as the discharge tube, a cold cathode tube (CCFL), an external electrode cold cathode tube (EEFL), a rare gas discharge tube, or the like can be used. In Embodiment 1, the case where a cold cathode tube is used as a discharge tube is illustrated.

  The discharge tube lighting circuit 2 includes a power supply unit 10, transformers TR1 to TR8, capacitors C1 to C8, current detection units AD1 to AD8, voltage detection units VD1 to VD8, and a short circuit unit 6. Further, the discharge tube portion 4 includes discharge tubes CCFL1 to CCFL8.

  In the following description, when the transformers TR1 to TR8, the capacitors C1 to C8, the current detection units AD1 to AD8, the voltage detection units VD1 to VD8, and the discharge tubes CCFL1 to CCFL8 are collectively shown, Also referred to as “transformer TR”, “capacitor C”, “current detection unit AD”, “voltage detection unit VD”, and “discharge tube CCFL”.

  Transformers TR1 to TR8 are arranged in association with discharge tubes CCFL1 to CCFL8, respectively, boost the AC power received from power supply unit 10 and supply it to one end of discharge tubes CCFL1 to CCFL8. Specifically, each of the transformers TR1 to TR8 has its primary side coil connected to the power supply unit 10, while one end of the secondary side coil is connected to the discharge tubes CCFL1 to CCFL8, and other secondary side coils. The end is connected (grounded) to the ground potential via the current detection units AD1 to AD8.

  Current detection units AD1 to AD8 detect currents (discharge tube currents) flowing between the transformers TR1 to TR8 and the ground potential, respectively, and output the detection results to the power supply unit 10.

  The other ends of the discharge tubes CCFL <b> 1 to CCFL <b> 8 are all electrically connected to the short-circuit portion 6 to be short-circuited with each other. In addition, the short circuit part 6 is maintained at a floating potential (floating) without being connected to the ground potential.

  Capacitors C1 to C8 are respectively connected between a path from the secondary side of transformers TR1 to TR8 to discharge tubes CCFL1 to CCFL8 and the ground potential. The capacitors C1 to C8 resonate with the inductance components of the transformers TR1 to TR8, respectively, thereby supplying a high-voltage AC voltage to the discharge tubes CCFL1 to CCFL8.

  Voltage detection units VD1 to VD8 detect voltages generated at both ends of capacitors C1 to C8, that is, voltages supplied to discharge tubes CCFL1 to CCFL8, respectively, and output the detection results to power supply unit 10.

  The power supply unit 10 generates AC power for lighting the discharge tube, and transformers TR1 to TR8 corresponding to the discharge tubes to be turned on according to a lighting command and a dimming command from an external control device (not shown) or the like. To the AC power. The power supply unit 10 generates AC power having a relatively high frequency (for example, several tens of kHz) in order to light the discharge tubes CCFL1 to CCFL8.

  Specifically, the power supply unit 10 generates a positive-phase AC voltage AC (+) and a negative-phase AC voltage AC (−) that are opposite in polarity, that is, in an opposite phase relationship to each other.

  FIG. 2 is a diagram illustrating an example of time waveforms of the positive-phase AC voltage AC (+) and the negative-phase AC voltage AC (−). Referring to FIG. 2, power supply unit 10 generates a positive-phase AC voltage AC (+) and a negative-phase AC voltage AC (−) that are in opposite phases to each other.

  In addition, the power supply unit 10 receives a first discharge tube group (normal phase supply) including at least one discharge tube CCFL among the plurality of discharge tubes CCFL constituting the discharge tube unit 4 in response to an external lighting command. And the second discharge tube group (reverse phase supply) are selected. The power supply unit 10 supplies a positive phase AC voltage AC (+) to a transformer TR (positive phase power supply) (hereinafter also referred to as a “first transformer group”) corresponding to the first discharge tube group, and the second A negative phase AC voltage AC (−) is supplied to a transformer TR (negative phase power feeding) (hereinafter also referred to as “second transformer group”) corresponding to the discharge tube group.

  In this way, by supplying the positive-phase AC voltage AC (+) and the negative-phase AC voltage AC (−), the positive-phase AC voltage AC ( A voltage twice as large as the positive phase AC voltage AC (+) (or the negative phase AC voltage AC (−)) corresponding to the voltage difference vector between the positive phase AC voltage AC (−) and the negative phase AC voltage AC (−). Become. Therefore, a voltage matching the positive phase AC voltage AC (+) is applied to the first discharge tube group with respect to the short-circuit portion 6, and at the same time, the second discharge tube group is reverse to the short-circuit portion 6. A voltage corresponding to the phase alternating voltage AC (−) is applied. Further, the discharge tube current generated on the secondary side of the first transformer group flows in the order of the first discharge tube group, the short-circuit portion 6 and the second discharge tube group, and from the secondary side of the second transformer group via the ground potential. Then, the current flows again on the route returning to the first transformer group or the reverse route.

  As is clear from the above description, the discharge tubes CCFL selected as the first discharge tube group and the second discharge tube group can be selected relatively freely. That is, by selecting the first discharge tube group and the second discharge tube group so as to include at least one discharge tube CCFL, a discharge tube current path is formed. Any combination can be realized as a lighting target. Furthermore, since both the current detection unit AD and the voltage detection unit VD that generate the control signal exist on the power supply unit 10 side, the detection result is obtained while avoiding the influence of noise regardless of the length of the discharge tube CCFL. Can be transmitted to the power supply unit 10.

  Since the total discharge tube current of the first discharge tube group matches the total discharge tube current of the second discharge tube group, in order to make the emission intensity of the entire light source uniform, the first discharge tube group and The second discharge tube group is preferably selected so as to include the same number of discharge tubes CCFL.

Hereinafter, the configuration of the power supply unit 10 will be described in more detail.
FIG. 3 shows a main portion of light source system 100 according to the first embodiment of the present invention.

  Referring to FIG. 3, power supply unit 10 includes, for example, two half-bridge circuits that generate positive-phase AC voltage AC (+) and negative-phase AC voltage AC (−), respectively. That is, the power supply unit 10 includes a positive phase driving unit 12, transistors Q1 and Q2, and a positive phase AC voltage generation unit including the capacitors C20 and C22, a negative phase driving unit 14, transistors Q3 and Q4, and a capacitor C20. , C22 and a negative AC voltage generator. Capacitors C20 and C22 are used in common for the positive-phase AC voltage generator and the negative-phase AC voltage generator.

  Looking at the positive-phase AC voltage generator, the transistors Q1 and Q2 are connected in series between the power supply voltage Vcc and the ground potential, and the positive-phase driver 12 receives the reference oscillation signal OSC from the oscillator (not shown). In response, the transistors Q1 and Q2 are turned on and off at predetermined intervals, respectively.

  Further, the capacitors C20 and C22 connected in series between the power supply voltage Vcc and the ground potential have the same electrostatic capacitance, and a voltage half that of the power supply voltage Vcc is present at the connection point thereof. Maintained.

  Here, at the connection point between the transistors Q1 and Q2, the power supply voltage Vcc is generated when the transistor Q1 is turned on, and the ground potential is generated when the transistor Q2 is turned on. Therefore, when viewed from the connection point (Vcc / 2) between the capacitor C20 and the capacitor C22, the voltages + Vcc / 2 and -Vcc / 2 are alternately generated as the transistors Q1 and Q2 are turned on and off. Therefore, an arbitrary AC voltage can be generated by controlling on / off of the transistors Q1 and Q2 at a predetermined timing by the positive phase driving unit 12.

  On the other hand, the operation of the negative-phase AC voltage generator is the same as that of the positive-phase AC voltage generator described above. However, the negative-phase driver 14 receives the reference oscillation signal OSC common to the positive-phase driver 12 and The transistors Q3 and Q4 are on / off controlled so as to have a reverse polarity with respect to the phase AC voltage AC (+), that is, a reverse phase. Therefore, the negative-phase AC voltage generator generates a negative-phase AC voltage AC (−) having a reverse phase with respect to the positive-phase AC voltage AC (+).

  The power supply unit 10 further includes switch units SW1 to SW8. The switch units SW1 to SW8 are configured to selectively connect the positive phase AC voltage generation unit or the negative phase AC voltage generation unit to the transformers TR1 to TR8 in response to the selection commands SEL1 to SEL8 based on the lighting command (FIG. 1). Is done.

  For example, the switch unit SW1 has a port A1 to which the positive phase AC voltage AC (+) is applied, a port B1 to which the negative phase AC voltage AC (−) is applied, and a port to which neither voltage is applied (floating voltage). C1 and one end of the primary side of the transformer TR1 is electrically connected to one of the ports in response to the selection command SEL1. On the other hand, since the other end of the primary side of the transformer TR1 is electrically connected to the connection point between the capacitor C20 and the capacitor C22, the primary side of the transformer TR1 is connected to the positive phase AC voltage AC according to the selection command SEL1. Any one of (+), negative-phase AC voltage AC (-), and floating voltage is applied.

  Hereinafter, each of the switch units SW2 to SW8 is the same as the switch unit SW1. In the following description, the switch units SW1 to SW8, the ports A1 to A8, the ports B1 to B8, the ports C1 to C8, and the selection commands SEL1 to SEL8 are simply indicated as “switch unit SW”. "," Port A "," Port B "," Port C ", and" Selection command SEL ".

  As described above, the power supply unit 10 selects the port A for at least one switch unit SW connected to the transformer TR included in the first transformer group in response to the lighting command (FIG. 1). The selection command SEL is given so as to apply the positive phase AC voltage AC (+), while the port B is selected for at least one switch unit SW connected to the transformer TR included in the second transformer group, A selection command SEL is given so as to apply the negative-phase AC voltage AC (−). For the discharge tube CCFL that is not lit (in the extinguished state), the port C is selected and maintained at a floating voltage.

  The power supply unit 10 is configured to be able to intermittently connect the positive phase AC voltage AC (+) or the negative phase AC voltage AC (−) supplied to the discharge tube CCFL. That is, by changing the selection command SEL periodically and causing the switch unit SW to switch between the port A and the port C or the port B and the port C at a predetermined cycle, the positive-phase AC voltage AC ( +) Or reverse-phase AC voltage AC (-) is intermittent. Thus, dimming can be realized by adjusting the intermittent cycle of the AC voltage supplied to the discharge tube CCFL.

  Further, the positive-phase AC voltage generator and the negative-phase AC voltage generator can be configured to change the voltage values of the positive-phase AC voltage AC (+) and the negative-phase AC voltage AC (−) according to the voltage limit command REG. Is done. That is, the positive phase drive unit 12 and the negative phase drive unit 14 change the duty ratio of the switching in accordance with the voltage limit command REG, so that the positive phase AC voltage AC (+) and the negative phase AC voltage AC (−) are changed. Change the effective voltage value. In this way, dimming can also be realized by adjusting the voltage value of the AC voltage supplied to the discharge tube CCFL.

Hereinafter, the lighting control of the discharge tube CCFL will be exemplified.
FIG. 4 is a diagram illustrating an example of lighting all the discharge tubes CCFL (eight).

  Referring to FIG. 4A, for example, four discharge tubes CCFL1 to CCFL4 are selected as the first discharge tube group (normal phase supply), and discharge tubes CCFL5 to CCFL5 are selected as the second discharge tube group (reverse phase supply). Select four CCFL8. And all of discharge tube CCFL1-CCFL8 can be lighted by applying normal phase alternating voltage AC (+) or negative phase alternating voltage AC (-) to each corresponding | compatible transformer TR.

  Referring to FIG. 4B, for example, four discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 are selected as the first discharge tube group (positive phase supply), and the second discharge tube group ( The even-numbered CCFL2, CCFL4, CCFL6, CCFL8 can be selected as the reverse-phase supply.

  Thus, when all the lamps (8) are turned on, the first discharge tube group and the second discharge tube group may be arbitrarily selected so as to include the same number (four) of discharge tubes.

FIG. 5 is a diagram illustrating an example of lighting arbitrary four of the discharge tubes CCFL.
Referring to FIG. 5A, for example, two discharge tubes CCFL1 and CCFL3 are selected as the first discharge tube group (normal phase supply), and discharge tubes CCFL5 are selected as the second discharge tube group (reverse phase supply). Select two CCFL7. Then, the odd-numbered four discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 can be lit by applying the normal phase AC voltage AC (+) or the negative phase AC voltage AC (−) to the corresponding transformer TR.

  5B, for example, two discharge tubes CCFL2 and CCFL4 are selected as the first discharge tube group (normal phase supply), and the discharge tube is used as the second discharge tube group (reverse phase supply). Two of CCFL6 and CCFL8 are selected. Then, the even-numbered four discharge tubes CCFL2, CCFL4, CCFL6, and CCFL8 can be turned on by applying the positive-phase AC voltage AC (+) or the negative-phase AC voltage AC (−) to the corresponding transformer TR.

  Furthermore, by alternately switching the lighting states of FIG. 5A and FIG. 5B, the light emission amount of the light source system 100 as a whole can be adjusted to half of the maximum light emission amount.

FIG. 6 is a diagram illustrating an example of lighting any two of the discharge tubes CCFL.
As the discharge tube CCFL to be lit, any two can be selected. As shown in FIG. 6A, for example, the discharge tube CCFL1 is selected as the first discharge tube group (positive phase supply), The discharge tube CCFL8 is selected as the second discharge tube group (reverse phase supply). Then, by applying the positive phase AC voltage AC (+) or the negative phase AC voltage AC (−) to the corresponding transformer TR, the discharge tubes CCFL1 and CCFL8 on the outermost side can be lit.

  Referring to FIG. 6B, for example, discharge tube CCFL4 is selected as the first discharge tube group (normal phase supply), and discharge tube CCFL5 is selected as the second discharge tube group (reverse phase supply). Then, by applying the positive phase AC voltage AC (+) or the negative phase AC voltage AC (−) to the corresponding transformer TR, the discharge tubes CCFL4 and CCFL5 adjacent in the center can be lit.

  FIG. 7 is a diagram for explaining dimming by intermittently supplying an AC voltage supplied to the discharge tube CCFL.

FIG. 7A shows an AC voltage connection period.
FIG. 7B shows an AC voltage cutoff period.

  Referring to FIG. 7A, in the AC voltage connection period, the positive-phase AC voltage AC (+) is supplied to the discharge tubes CCFL1 and CCFL3 as well as the above-described FIG. The phase alternating voltage AC (−) is supplied to the discharge tubes CCFL5 and CCFL7. Therefore, the odd-numbered four discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 are turned on.

  Referring to FIG. 7B, in the AC voltage cutoff period, the supply of the positive phase AC voltage AC (+) or the negative phase AC voltage AC (−) is cut off for any discharge tube CCFL. . Therefore, none of the discharge tubes CCFL is lit.

  The power supply unit 10 (FIG. 3) can adjust the light emission amount of the light source system 100 as a whole by repeating the lighting states shown in FIGS. 7A and 7B in a predetermined intermittent cycle. That is, the light source system 100 as a whole generates a light emission amount proportional to the time ratio of the period shown in FIG.

  FIG. 8 is a diagram for explaining dimming by changing the voltage value of the AC voltage supplied to the discharge tube CCFL.

FIG. 8A shows a case where an AC voltage having a maximum voltage value (100%) is supplied.
FIG. 8B shows a case where an AC voltage that is half (50%) of the maximum voltage value is supplied.

  Referring to FIG. 8 (a), in the same manner as in FIG. 5 (a) described above, the positive phase AC voltage AC (+) is supplied to the discharge tubes CCFL1 and CCFL3, and the negative phase AC voltage AC (−) is supplied. It is supplied to the discharge tubes CCFL5 and CCFL7. And the power supply part 10 sets the voltage value of positive phase alternating voltage AC (+) and negative phase alternating voltage AC (-) to the maximum voltage value (100%). In the first embodiment of the present invention, the maximum voltage value is when the peak value (peak value) of the AC voltage is ½ of the power supply voltage Vcc (FIG. 3).

  In this case, each of the discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 generates the maximum light emission amount on the system.

  Referring to FIG. 8B, when the power supply unit 10 sets the voltage values of the positive-phase AC voltage AC (+) and the negative-phase AC voltage AC (−) to half of the maximum voltage value (50%), each discharge The tubes CCFL1, CCFL3, CCFL5 and CCFL7 generate a light emission amount reduced to ½ compared to FIG. The positive phase driving unit 12 and the negative phase driving unit 14 adjust the duty ratios for the transistors Q1, Q2, and Q3, Q4, respectively, so that the positive phase AC voltage AC (+) and the negative phase AC voltage AC (−) The voltage value is reduced.

  According to the first embodiment of the present invention, the positive phase AC voltage is supplied to the discharge tube selected as the first discharge tube group, and the negative phase AC voltage is supplied to the discharge tube selected as the second discharge tube group. On the other hand, the other ends of the respective discharge tubes are short-circuited to each other. Thereby, a current path from the discharge tube of the first discharge tube group to the discharge tube of the second discharge tube group is formed via the short-circuit portion. Therefore, when viewed from the power supply unit, the discharge tube of the first discharge tube group and the discharge tube of the second discharge tube group can be regarded as a single discharge tube, and current detection arranged at a position close to the power supply unit. The control signal can be generated by the unit and the voltage detection unit. At the same time, any discharge tube can be selected as the first discharge tube group and the second discharge tube group.

  Therefore, it is possible to realize a discharge tube lighting circuit and a photoelectric system capable of performing lighting control with a relatively high degree of freedom by arbitrarily selecting a discharge tube to be lit while avoiding the influence of noise on the control signal.

[Embodiment 2]
In the first embodiment described above, the configuration in which the power supply unit includes two AC voltage generation units (a normal phase AC voltage generation unit and a negative phase AC voltage generation unit) has been described. On the other hand, in the second embodiment, a configuration using a power supply unit including one AC voltage generation unit will be described.

  The schematic configuration diagram of the light source system according to the second embodiment of the present invention is the same as that of FIG. 1, and therefore detailed description will not be repeated.

FIG. 9 shows a main portion of the light source system according to the second embodiment of the present invention.
Referring to FIG. 9, power supply unit 10 # according to the second embodiment of the present invention includes, as an example, one half bridge circuit that generates AC voltage AC. That is, power supply unit 10 # includes an AC voltage generation unit including drive unit 16, transistors Q5 and Q6, and capacitors C20 and C22.

  Transistors Q5 and Q6 are connected in series between power supply voltage Vcc and ground potential, and drive unit 16 causes transistors Q5 and Q6 to be transmitted at a predetermined cycle based on a reference oscillation signal received from an oscillation unit (not shown). Turn on and off.

  Further, the capacitors C20 and C22 connected in series between the power supply voltage Vcc and the ground potential have the same electrostatic capacitance, and a voltage half that of the power supply voltage Vcc is present at the connection point thereof. Maintained.

  Here, at the connection point between the transistors Q5 and Q6, the power supply voltage Vcc is generated when the transistor Q5 is turned on, and the ground potential is generated when the transistor Q6 is turned on. Therefore, when viewed from the connection point (Vcc / 2) between capacitor C20 and capacitor C22, voltages of + Vcc / 2 and -Vcc / 2 are alternately generated as transistors Q5 and Q6 are turned on / off. Therefore, an arbitrary AC voltage can be generated by controlling on / off of the transistors Q5 and Q6 at a predetermined timing.

  Power supply unit 10 # further includes switch units SW1 # to SW8 #. Switch units SW1 # to SW8 # are configured to be capable of selectively connecting an AC voltage generating unit to transformers TR1 to TR8 in response to selection commands SEL1 # to SEL8 # based on the lighting command (FIG. 1).

  For example, switch unit SW1 # electrically connects or disconnects a port to which AC voltage AC is applied and one end on the primary side of transformer TR1. On the other hand, the other end of the primary side of the transformer TR1 is electrically connected to a connection point between the capacitor C20 and the capacitor C22. Therefore, the primary side of the transformer TR1 is connected to the AC voltage AC or the AC according to the selection command SEL1 #. A floating voltage will be applied.

  Hereinafter, each of the switch units SW2 # to SW8 # is the same as the switch unit SW1 #. In the following description, when the switch units SW1 # to SW8 # and the selection commands SEL1 # to SEL8 # are collectively indicated, they are also simply referred to as “switch unit SW #” and “selection command SEL #”. .

  Furthermore, in the power supply system according to the second embodiment of the present invention, the polarity of the winding in odd-numbered transformers TR1, TR3, TR5, TR7 is the same as the polarity of the winding in even-numbered transformers TR2, TR4, TR6, TR8. It is configured to have a reverse polarity. That is, the odd-numbered transformers TR1, TR3, TR5, TR7 respectively boost the AC voltage AC received from the AC voltage generator with the same polarity and supply it to the corresponding discharge tube CCFL, while the even-numbered transformer TR2, TR4, TR6, TR8 respectively boost the AC voltage AC received from the AC voltage generator by inverting the polarity, and supply the boosted voltage to the corresponding discharge tube CCFL.

  Therefore, the AC voltage supplied to the odd-numbered discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 is opposite in polarity to the AC voltage supplied to the even-numbered discharge tubes CCFL2, CCFL4, CCFL6, CCFL8, that is, opposite in phase to each other. It becomes the relationship.

  Therefore, in the second embodiment of the present invention, at least one discharge tube is selected from the odd-numbered discharge tubes CCFL1, CCFL3, CCFL5, CCFL7 as the first discharge tube group (positive phase supply), and the second discharge tube At least one discharge tube is selected from the even-numbered discharge tubes CCFL2, CCFL4, CCFL6, CCFL8 as a group (reverse phase supply).

  As described above, the first discharge tube group is supplied with an AC voltage having the same phase as the AC voltage AC, and the second discharge tube group is supplied with an AC voltage having a phase opposite to that of the AC voltage AC. A voltage twice as high as the AC voltage AC is applied between the discharge tube group and the second discharge tube group. Therefore, a voltage that matches the AC voltage AC is applied to the short-circuit portion 6 in each of the first discharge tube group and the second discharge tube group. Since the discharge tube current generated between the first discharge tube group and the second discharge tube group is the same as that of the first embodiment of the present invention described above, detailed description will not be repeated.

  Furthermore, power supply unit 10 # is configured to be capable of intermittently supplying AC voltage AC supplied to discharge tube CCFL, similarly to power supply unit 10 according to Embodiment 1 of the present invention described above. And power supply part 10 # implement | achieves light control of discharge tube CCFL by adjusting the intermittent cycle of the alternating voltage supplied, ie, the lighting cycle of discharge tube CCFL.

  Further, power supply unit 10 # is configured to be able to change the voltage value of AC voltage AC. And power supply part 10 # implement | achieves light control also by adjusting the voltage value of the alternating voltage supplied to discharge tube CCFL.

  Since it is the same as power supply unit 10 according to Embodiment 1 of the present invention described above, detailed description will not be repeated.

  Further, the same lighting control as that of light source system 100 according to the first embodiment of the present invention described above can be realized except that discharge tubes that can be selected as the first discharge tube group and the second discharge tube group are limited. It is. That is, it is possible to realize the lighting control as shown in FIGS. The details are the same as in the first embodiment of the present invention, and are not repeated.

  According to Embodiment 2 of the present invention, the positive phase AC voltage is supplied to the discharge tubes selected as the first discharge tube group, and the negative phase AC voltage is supplied to the discharge tubes selected as the second discharge tube group. On the other hand, the other ends of the respective discharge tubes are short-circuited to each other. Thereby, a current path from the discharge tube of the first discharge tube group to the discharge tube of the second discharge tube group is formed via the short-circuit portion. Therefore, when viewed from the power supply unit, the discharge tube of the first discharge tube group and the discharge tube of the second discharge tube group can be regarded as a single discharge tube, and current detection arranged at a position close to the power supply unit. The control signal can be generated by the unit and the voltage detection unit. At the same time, arbitrary discharge tubes can be selected as the first discharge tube group and the second discharge tube group from candidates determined in advance according to the connection direction of the transformer.

  Therefore, it is possible to realize a discharge tube lighting circuit and a photoelectric system capable of performing lighting control with a relatively high degree of freedom by arbitrarily selecting a discharge tube to be lit while avoiding the influence of noise on the control signal. In addition, since the power supply unit can be configured by one AC voltage generator, a more simplified discharge tube lighting circuit and photoelectric system can be realized.

  In the first and second embodiments of the present invention described above, the light source system including eight discharge tubes CCFL is exemplified, but it goes without saying that the number of discharge tubes CCFL is not limited to eight. The present invention can be applied to any light source system including at least a plurality (two or more) of discharge tubes CCFLs regardless of the number. Furthermore, the light source device can be configured to include a plurality of sets of the above-described light source systems.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of the light source system 100 provided with the discharge tube lighting circuit according to Embodiment 1 of the present invention. It is a figure which shows an example of the time waveform of a normal phase alternating voltage and a negative phase alternating voltage. It is a figure which shows the principal part of the light source system according to Embodiment 1 of this invention. It is a figure which shows an example in the case of lighting all the discharge tubes CCFL (eight). It is a figure which shows an example in the case of lighting arbitrary four among discharge tubes CCFL. It is a figure which shows an example in the case of lighting arbitrary two of the discharge tubes CCFL. It is a figure for demonstrating the light control by interrupting the alternating voltage supplied to the discharge tube CCFL. It is a figure for demonstrating the light control by changing the voltage value of the alternating voltage supplied to the discharge tube CCFL. It is a figure which shows the principal part of the light source system according to Embodiment 2 of this invention.

Explanation of symbols

  2 discharge tube lighting circuit, 4 discharge tube section, 6 short circuit section, 10, 10 # power supply section, 12 normal phase drive section, 14 reverse phase drive section, 16 drive section, 100 light source system, AD1 to AD8 current detection section, C1 ˜C8, C20, C22 capacitors, CCFL1 to CCFL8 discharge tubes, OSC reference oscillation signal, Q1, Q2, Q3, Q4, Q5, Q6 transistors, REG voltage limit command, SEL1 to SEL8, SEL1 # to SEL8 # selection command, SW1 ~ SW8, SW1 # ~ SW8 # switch part, TR1 ~ TR8 transformer, Vcc power supply voltage, VD1 ~ VD8 voltage detection part.

Claims (6)

A discharge tube lighting circuit for lighting a plurality of discharge tubes,
A power supply unit for generating AC power for lighting the discharge tube;
A plurality of transformers for boosting the AC power received from the power supply unit and supplying the AC power to one end of the corresponding discharge tube;
A short-circuit portion for short-circuiting the other ends of the plurality of discharge tubes,
The power supply unit includes the first and second discharge tube groups each including at least one discharge tube among the plurality of discharge tubes, through the first transformer group corresponding to the first discharge tube group. While supplying an AC voltage to the first discharge tube group, an AC voltage having a polarity opposite to that of the AC voltage is applied to the second discharge tube group via a second transformer group corresponding to the second discharge tube group. is configured to supply,
The power supply unit is
A first AC voltage generator for generating a first AC voltage;
A second AC voltage generator for generating a second AC voltage having a polarity opposite to that of the first AC voltage;
A selector configured to selectively connect the first AC voltage generator to the first transformer group, and to selectively connect the second AC voltage generator to the second transformer group. And a discharge tube lighting circuit. A discharge tube lighting circuit for lighting a plurality of discharge tubes,
A power supply unit for generating AC power for lighting the discharge tube;
A plurality of transformers for boosting the AC power received from the power supply unit and supplying the AC power to one end of the corresponding discharge tube;
A short-circuit portion for short-circuiting the other ends of the plurality of discharge tubes,
The power supply unit includes the first and second discharge tube groups each including at least one discharge tube among the plurality of discharge tubes, through the first transformer group corresponding to the first discharge tube group. While supplying an AC voltage to the first discharge tube group, an AC voltage having a polarity opposite to that of the AC voltage is applied to the second discharge tube group via a second transformer group corresponding to the second discharge tube group. Configured to supply
The power supply unit is
An AC voltage generator for generating AC voltage;
A selection unit configured to be selectively connectable to the first and second transformer groups, the AC voltage generation unit,
The first transformer group received from the AC voltage generation unit so as to have a reverse polarity with respect to the boosted AC voltage supplied to the second discharge tube group by the second transformer group. A discharge tube lighting circuit that boosts AC voltage . The discharge tube lighting circuit according to claim 1 or 2 , wherein the first and second discharge tube groups include the same number of the discharge tubes. The power supply unit, said first and intermittently configured to allow AC voltage supplied to the second discharge tube group, a discharge tube lighting circuit according to any one of claims 1-3. The power supply unit, said first and changeable configured the voltage value of the AC voltage supplied to the second discharge tube group, a discharge tube lighting circuit according to any one of claims 1-4. The discharge tube lighting circuit according to any one of claims 1 to 5 ,
A light source system comprising the plurality of discharge tubes.

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