JP5195020B2 - Light source element lighting device - Google Patents

Description

  The present invention relates to a lighting device for a light source element used as a transmission or reflection light source of a non-self-luminous display device. For example, a backlight / front employing a cold cathode tube in a liquid crystal display device such as a liquid crystal television or an LCD monitor. It can be suitably used in a light.

  A backlight incorporating a cold cathode tube (hereinafter referred to as a lamp) is generally used as a light source element of a liquid crystal display device having no self-light emitting function. In order to drive the lamp, an alternating high voltage is required. Therefore, a cold cathode tube lighting device (hereinafter referred to as an inverter) is used to generate an alternating high voltage to drive the lamp.

  On the other hand, since the lamp at the start of lighting is close to a no-load state, a high voltage approximately 2 to 3 times the normal lighting voltage is required at the start of lighting. Therefore, the voltage at the time of no load of the inverter, that is, the so-called open circuit voltage, needs to be higher than the required voltage. In this way, since the inverter outputs the highest voltage when there is no load, the high voltage will continue to be output in an abnormal state where the lamp is damaged or disconnected, i.e., when there is no load. An abnormal discharge occurs between adjacent metals. In order to prevent this, a protection circuit is usually provided inside the inverter. When the lamp is abnormal, a protective operation such as a temporary stop (hereinafter referred to as “Shutdown”) is performed to prevent problems caused by high voltage output. ing.

  When a failure such as a crack or cable break occurs in the lamp, the feedback current from the lamp decreases. This current drop is detected by the abnormality detection circuit, and the inverter shuts down to prevent abnormal operation such as high voltage output. As another method, a method of detecting the high voltage due to a crack in the lamp or a cable disconnection and shutting down to prevent abnormal operation such as high voltage output is also well known (Patent Document 3).

Recently, since a higher luminance is required, a plurality of lamps are often provided.
In an inverter that drives a plurality of lamps, a protection circuit that shuts down all lamps when a load abnormality (hereinafter referred to as NG) occurs even with a single lamp so as not to continue to output a high voltage when a load abnormality such as lamp breakage occurs. Is common (patent documents 2 to 5).

  However, in the case of a non-self-luminous display device, if all lamps are shut down with one lamp NG, the display is not reflected, so there are some cases where all lamps are not preferred for some applications. For example, Patent Document 1 describes an example of a protection circuit that shuts down when abnormality occurs in both lamps (paragraph 0042).

  In this way, there are several possible options for the shutdown function of the multiple lamp protection circuit, and when deciding on the function, the specifications of the protection circuit required by the safety standard, usage conditions, application, etc. of the destination are required. Different. For this reason, eventually, it is necessary to prepare a plurality of inverters corresponding to each destination, which causes an increase in cost.

JP 2005-340023 A JP-A-6-207979 Japanese Patent Laid-Open No. 10-161083 JP 2007-329098 A JP 2006-302628 A

The present invention has been made to solve the above-described problems. In a lighting device for a light source element having a protection circuit that operates when a load is abnormal, the operation of the protection circuit is performed by an external signal according to the conditions of the destination. An object of the present invention is to provide a lighting device for a light source element that can meet the demands of a plurality of destinations with a single type of light source element lighting device by switching the contents.

A lighting device for a light source element according to the present invention is a lighting device for a light source element having a plurality of light source elements, a light source driving circuit for lighting the source elements, and an abnormality detection circuit for detecting a lighting abnormality of the light source elements. The first protection function switching signal input from outside the lighting device is provided, and the first light source element of the plurality of light source elements continues to be lit even if a lighting abnormality occurs . A protection mode and a second protection mode in which lighting of all the light source elements is temporarily suspended when a lighting abnormality occurs in one of the plurality of light source elements. The first protection mode and the second protection mode are switched based on the function switching signal .

By inputting an arbitrary signal from the outside, a protection circuit function can be selected according to the destination application and the like, and a plurality of different requirements can be met with a single type of light source device lighting device .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in order to avoid redundant description, elements having the same or corresponding functions in each drawing are denoted by the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a block diagram of an inverter 1 according to the first embodiment. The inverter 1 receives a power supply voltage, a lighting ON / OFF (ENABLE) signal, a dimming signal, and the like from the outside.
The inverter is a lighting ON / OFF block 2 that controls the operation of the inverter by turning on and off the power supply voltage by an external lighting ON / OFF signal, and a dimming circuit unit for changing the brightness of the lamp 10 by an external dimming signal 5 and a high AC voltage required for a DC / DC converter circuit section (hereinafter referred to as a DC / DC circuit) 3 and a cold cathode tube (hereinafter referred to as a lamp) 10 for making the output constant regardless of the external power supply voltage. DC / AC inverter circuit unit (hereinafter referred to as a DC / AC circuit) 4 for generating a voltage, and AC / DC inverter circuit unit (hereinafter referred to as an AC / DC circuit) for converting a feedback current from the lamp 10 into a DC voltage 6 The abnormality detection circuit unit 7 detects abnormality of the lamp 10 by the output (nodes A and B) signals of the AC / DC circuit.
The lamp is driven through a DC / AC circuit 4 by a DC voltage generated by the DC / DC circuit 3 (light source driving circuit).

  Further, in the first embodiment, an OR circuit 8 and an AND circuit 9 are further provided between the AC / DC circuit 6 and the abnormality detection circuit 7, and abnormality detection is performed from the AND circuit 9 by a protection function switching signal from the outside. It is characterized in that the function of the protection circuit 13 (portion surrounded by the alternate long and short dash line) can be selected by intermittently controlling the signal to the circuit 7 with the switch 11.

  Next, a specific operation of the inverter 1 shown in FIG. 1 will be described. As a basic input of the inverter 1, a power supply voltage, a lighting ON / OFF signal, and a dimming signal are input from the outside of the inverter. A power supply voltage is input to the DC / DC circuit 3 by driving the lighting ON / OFF circuit 2 with a lighting ON signal from the outside. In the DC / DC circuit 3, it is possible to adjust the feedback current from the lamp 10 so that the feedback current is constant regardless of the input voltage. In addition, by changing the output voltage of the DC / DC circuit 3 or the energy applied from the light source driving circuit to the lamp 10 by the intermittent operation (PWM operation) by repeated lighting ON / OFF by the dimming signal, the lamp 10 The brightness can be changed.

  The DC voltage output from the DC / DC circuit 3 of the light source driving circuit is input to the DC / AC circuit 4 and an alternating high voltage for lighting the lamp 10 is output. In particular, when the lamp 10 is turned on, it is close to a no-load state, and therefore, a high voltage of about 2 to 3 times that of normal lighting is applied. Therefore, the high voltage at the time of no load, that is, the open voltage of the inverter 1 is higher than that.

Next, the protection operation will be described. When the lamp 10 is lit, the feedback current from the lamp 10 is input to the AC / DC circuit 6, and a DC voltage signal obtained by DC / voltage conversion is generated. This DC voltage signal is fed back to the DC / DC circuit 3, and the feedback current is controlled to be a constant value commanded by the dimming signal.
Next, when the DC voltage signal is higher than a predetermined reference voltage value by a comparator (not shown), that is, when the feedback current is normally fed back, the output of the comparator, that is, the output of the AC / DC circuit 6 becomes the “High” signal. Become.
In addition, when a light emission failure occurs due to an abnormal situation such as cable breakage or lamp breakage, and the feedback current does not return, the DC voltage signal becomes lower than a predetermined reference voltage value, and the output of the comparator, that is, AC / DC The output of the circuit 6 becomes a “Low” signal.

The abnormality detection circuit 7 performs a shutdown operation when a “Low” signal is input from one or both of the OR circuit 8 and the AND circuit 9, and the inverter 1 is turned on by the lighting ON / OFF circuit 2 or the DC / DC circuit 3. It shall be shut down. On the other hand, when the “High” signal is input from both the OR circuit 8 and the AND circuit 9, the inverter 1 is normally operated by the lighting ON / OFF circuit 2 or the DC / DC circuit 3, and the two lamps 10 are turned on. It shall be lit (node E).
The output of the OR circuit 8 is input to the abnormality detection circuit 7 as it is, but the output signal of the AND circuit 9 is intermittently controlled by the switch 11 controlled by a protection function switching signal from the outside and is output to the abnormality detection circuit 7. Input (node D).

  Here, first, a description will be given of a specification in which all lamps are shut down when the lamp 10 becomes all lamps NG as the “first protection mode”. A protection function switching signal “Low” for turning off the switch 11 is inputted as a specification selection for shutting down all lamps when all lamps are NG in advance.

  As shown in Table 1, the output of the OR circuit 8 (node C) when both the lamps 10 are operating normally is a “High” signal. Since the output (node D) of the AND side circuit 9 is disconnected (OFF), the “High” signal is always input to the abnormality detection circuit 7 by the internal pull-up resistor 12, and the inverter 1 operates normally. to continue. When one of the lamps 10 becomes NG, the OR circuit 8 outputs a “High” signal (node C), and the remaining (the other) lamp continues to operate normally. However, when both the lamps 10 are NG, the output of the OR circuit 8 (node C) becomes a “Low” signal, so that the abnormality detection circuit 7 determines that an abnormality has occurred, and the lighting ON / OFF circuit 2 or DC The / DC circuit 3 is controlled (when the DC / DC circuit 3 is controlled, the connection line shown by the broken line in FIG. 1 is used), and the operation of the inverter 1 is stopped.

  Next, a description will be given of a specification in which the lamp 10 shuts down all lamps even when one of the lamps is NG as the “second protection mode”. As a specification selection, “High” is input to the protection function switching signal for connecting (ON) the switch 11. When operating normally, both the OR circuit 8 and the AND circuit 9 output a “High” signal, and the inverter 1 continues to operate normally. However, when the lamp 10 becomes NG, the output signal of the AND circuit 9 becomes a “Low” signal, so that the “Low” signal is input to the abnormality detection circuit 7 via the switch 11 to detect the abnormality. The inverter 1 is shut down when the circuit 7 determines that an abnormality has occurred. Even when the lamp 10 becomes all lamps NG, both the OR circuit 8 and the AND circuit 9 output the “Low” signal, so that the inverter 1 is similarly shut down.

  In the first embodiment, an example in which two lamps are used and a ballast capacitor is used has been described. However, a plurality of two or more lamps may be used, such as a ballast capacitor-less type. Similarly, the configuration shown in the above-described embodiment can be adopted in the configuration of a similar light source driving circuit.

Embodiment 2. FIG.
FIG. 2 is a block diagram of an inverter 1 having four lamps and having a plurality of output circuits (DC / DC circuit and DC / AC circuit). In the second embodiment, two sets of light source driving circuits composed of the DC / DC circuit (3, 20) and the DC / AC circuit 4 shown in the first embodiment are employed, and each of these driving circuits is used. Two lamps 10 are driven. The protection circuit includes a protection circuit 13 corresponding to the upper two lamps 10 and a protection circuit 23 corresponding to the lower two lamps 10, each of which has the same configuration as the protection circuit described in the first embodiment. Since they are the same, detailed description of the configuration is omitted here.

The protection circuit 13 and the protection circuit 23 described above are controlled by the protection function switching signal 1 in which the switch 11 and the switch 21 are the same intermittent control signal. Consider a case where 1 and the protection function switching signal 2 are “Low”.
In this case, the outputs of the AND circuit 24 in the protection circuit 13, the protection circuit 23, and the protection circuit 28 become invalid, and a protection function is realized based on the output of the OR circuit 8 in the protection circuit 13 and the protection circuit 23. In this mode, even if one of the four lamps 10 is turned off, the shutdown does not occur and the remaining three lamps are continuously turned on.
Further, when either one of the upper and lower lamps 10 is turned off, one of the upper and lower corresponding light source driving circuits is shut down. The other light source driving circuit does not shut down.

Next, in the “second protection mode”, the protection function switching signal 2 becomes “High”, and the output of the AND circuit 24 in the protection circuit 28 is input to the abnormality detection circuit 2 (26) through the switch 25. .
In this case, due to the operation of the two AND circuits 9 and the AND circuit 24, the function of the abnormality detection circuit 2 (26) in the protection circuit 28 is activated when even one of the four lamps 10 is turned on. Since the operation of the lighting ON / OFF circuit 2 is stopped and the power supply to the DC / DC circuits (3, 20) is stopped, the four lamps 10 are all shut down. In this case, “High / Low” of the protection function switching signal 1 does not affect the logic of the shutdown operation.

  As a “third protection mode” different from the above-described two modes, there is a mode in which the protection function switching signal 1 is “High” and the protection function switching signal 2 is “Low”. In this case, if one of the lamps 10 driven by the one light source driving circuit is turned on, the other lamp 10 is shut down. However, this does not affect the shutdown operation of the two lamps (the other set) connected to the other set of light source drive circuits.

  The logical function of these external signals (protection function switching signals 1 and 2) can switch the specifications of the protection function according to the request of the destination of the same inverter.

In the second embodiment described above, four lamps are driven by two light source driving circuits and two types of protection function switching signals are used to meet the destination specifications. However, a larger number of lamps are driven. In this case, it is easy to increase the number of lamps connected to the light source driving circuit.
As another method for dealing with a large number of lamps, a method of increasing the number of protection function switching signals by adding a light source driving circuit and a protection circuit for driving two lamps can be easily realized. .

In the first and second embodiments described above, a cold cathode tube is typically exemplified as the light source element and is shown as “the best mode for carrying out the invention”. However, the present invention is a linear light source. The light source is not limited to a cold cathode tube, and may be a point light source such as an LED or a laser diode.
In addition, as a technique for switching the logic output from the OR circuit / AND circuit to the abnormality detection circuit using the protection function switching signal, a circuit employing a switch and a pull-up resistor as an output of the AND circuit has been exemplified. Many logic switching methods such as a method of switching signals using a switch controlled by a protection function switching signal for the output of the AND circuit are conceivable, and the present invention is not limited to the methods shown in the first and second embodiments. .
Further, in the first and second embodiments described above, the backlight lighting device is exemplified as the transmission light source of the display device. However, the present invention may be used for the front light lighting device as the reflection light source of the display device. Good. In this case, the light source element may employ a point light source such as the LED.

It is an inverter block diagram which concerns on Embodiment 1 of this invention. It is an inverter block diagram which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter 2 Lighting ON / OFF block 3, 20 DC / DC circuit 4 DC / AC circuit 5 Dimming circuit part 6 AC / DC circuit 7, 22, 26 Abnormality detection circuit part 8 OR circuit 9, 24 AND circuit 10 Lamp 11 , 21, 25 Switch 12, 27 Internal pull-up resistor 13, 23, 28 Protection circuit A, B, C, D, E Node

Claims (2)

A plurality of light source elements, and a light source driving circuit for lighting the light source elements;
A lighting device for a light source element having an abnormality detection circuit for detecting a lighting abnormality of the light source element,
A first protection function switching signal input to the device from outside the lighting device;
Of the plurality of light source elements, a first protection mode that continues lighting of the remaining light source elements even if a lighting abnormality occurs in one light source element,
A second protection mode in which lighting of all the light source elements is temporarily suspended when a lighting abnormality occurs in one of the light source elements.
Lighting device of a light source element characterized by switching the first the first protection mode based on the protection switching signal and the second protection mode. The lighting device according to claim 1 ,
A second protection function switching signal to be input to the device from outside the lighting device;
The light source driving circuit is composed of a plurality of lamp driving circuits for driving a plurality of sets of light source elements, respectively.
When lighting abnormality occurs in one light source element of the plurality of sets of light source elements, the lighting of the other light source elements belonging to the set is temporarily stopped, and the light source elements belonging to the other set continue to be turned on. A protection mode,
A light source element that switches between the first protection mode, the second protection mode, and the third protection mode according to the first protection function switching signal and the second protection function switching signal. Lighting device.

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