JP2010086921A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent burnout of a connection part even if an arc discharge occurs between a cold-cathode tube lamp and the connection part in a light source device of a constitution that a pair of the cold-cathode tube lamps are electrically connected by the connection part. <P>SOLUTION: The light source device 1 includes the pair of cold-cathode tube lamps 2a, 2b, the connection part 3 to electrically connect the pair of cold-cathode tube lamps 2a, 2b, an inverter 31 to supply a high-frequency voltage to the pair of cold-cathode tube lamps 2a, 2b, and a microcomputer 36. Moreover, the light source device 1 includes a voltage detection circuit 34 to detect the voltage of the connection part 3, and an elevation detection circuit 35 to detect whether the voltage of the connection part 3 is raised to have a prescribed value or more based on the voltage detected by the voltage detection circuit 34. When it is detected that the voltage of the connection part 3 is raised to the prescribed value or more by the elevation detection circuit 35, the microcomputer 36 stops formation of the high-frequency voltage by the inverter 31, and prevents the high-frequency voltage from being supplied to the cold-cathode tube lamps 2a, 2b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light source device using a cold cathode tube lamp (CCFL).

  2. Description of the Related Art Conventionally, a light source device using a cold cathode tube lamp has a configuration shown in FIG. A light source device 70 shown in FIG. 4 includes a plurality of cold cathode tube lamps 71, a plurality of connection portions 72 that electrically connect the cold cathode tube lamps 71, and an inverter board that supplies a high frequency voltage to the cold cathode tube lamps 71. 73. Each cold cathode tube lamp 71 has one end connected to the inverter board 73 via the connector 74 and the conductive wire 75, and the other end connected to the connecting portion 72. Each connecting portion 72 is made of a metal plate, and electrically connects a pair of cold cathode tube lamps 71a and 71b in series.

  That is, the light source device 70 has a configuration in which a pair of cold-cathode tube lamps 71 a and 71 b are electrically connected in series by a single connection portion 72. A pair of cold-cathode tube lamps 71a and 71b and a pair of cold-cathode tube lamps 71a and 71b are electrically connected in series to form a pseudo U-shaped cold-cathode tube lamp. . The light source device 70 includes a plurality of pairs of the pair of cold cathode tube lamps 71a and 71b and one connection portion 72 (pseudo U-shaped cold cathode tube lamps) connected in this way.

  The light source device 70 having such a configuration supplies a high-frequency voltage to each cold-cathode tube lamp 71 from the inverter board 73 via the conductive wire 75 and the connector 74 (reverse phase to the cold-cathode tube lamp 71a and the cold-cathode tube lamp 71b). Each cold cathode tube lamp 71 is driven to light by supplying a high frequency voltage.

Further, in a light source device that sequentially drives a plurality of cold cathode tube lamps in a time-sharing manner, an abnormality of each cold cathode tube lamp is detected when each cold cathode tube lamp is driven (for example, a patent) Reference 1). Further, in a light source device that drives a plurality of cold-cathode tube lamps at the same time, a total current of currents flowing through the plurality of cold-cathode tube lamps and a differential current of currents flowing through the plurality of cold-cathode tube lamps are detected, and the detection results thereof Based on the above, there is known one that detects an abnormality of a cold cathode tube lamp (see, for example, Patent Document 2). Further, in a light source device that drives a plurality of lamps simultaneously, a power source voltage is cut off when a current flowing through at least one lamp is equal to or less than a certain reference value (see, for example, Patent Document 3). ). Further, in a light source device that drives a plurality of lamps at the same time, when the current flowing through each lamp exceeds a set value, the current flowing through the corresponding lamp is suppressed (for example, see Patent Document 4). . In addition, a light source device including a plurality of cold cathode tube lamps is known in which a pseudo U-shaped cold cathode tube lamp is configured by connecting two cold cathode tube lamps with conductive wires (for example, (See Patent Document 5).
JP 2005-197177 A JP 2007-280876 A JP 2004-311396 A JP 2004-265868 A JP 2007-214043 A

  By the way, in the conventional light source device 70 described above, since the pair of cold cathode tube lamps 71a and 71b are electrically connected by the connection portion 72, the connection between the cold cathode tube lamp 71a and the connection portion 72, or If there is a connection failure between the cold cathode tube lamp 71b and the connection portion 72, arc discharge (spark) occurs between them. When such arc discharge occurs, a voltage several times that of normal times is generated, and the connecting portion 72 may be burned out. Even if the contents disclosed in Patent Document 1 to Patent Document 5 described above are applied, the above problem cannot be solved.

  The present invention has been made to solve the above problems, and in a light source device having a configuration in which a pair of cold-cathode tube lamps are electrically connected by a connecting portion, the cold-cathode tube lamp and the connecting portion are provided. It is an object of the present invention to provide a light source device that can prevent a connection portion from burning even when arc discharge occurs.

  In order to achieve the above object, the invention of claim 1 includes a pair of cold-cathode tube lamps, a connection part for electrically connecting a pair of cold-cathode tube lamps in series, and a pair of cold-cathode tube lamps. In a light source device comprising: an inverter that generates a high-frequency voltage for lighting; and a pair of cold-cathode tube lamps that are driven to drive when a high-frequency voltage is supplied from the inverter to the pair of cold-cathode tube lamps. A voltage rise detecting means for detecting whether or not the voltage at the connection section has risen above a predetermined value, and when the voltage rise detection means detects that the voltage at the connection section has risen above a predetermined value, And a protection means for performing a protection operation for stopping the supply of the high-frequency voltage to the tube lamp.

  According to a second aspect of the present invention, in the light source device according to the first aspect of the present invention, the light source device further includes a lamp connection board provided with a connection portion and an inverter board provided with an inverter, and the voltage rise detection means includes: Based on the feedback signal voltage output from the voltage detection unit that detects the voltage and outputs the detected voltage as a feedback signal voltage, it is determined whether or not the voltage at the connection unit has increased to a predetermined value or more. A rise detection unit for detecting, the voltage detection unit is provided on the lamp connection board, the rise detection unit is provided on the inverter board, and the voltage detection unit and the rise detection unit are connected via an electric cable. It is what.

  According to a third aspect of the present invention, in the light source device according to the second aspect, the electric cable is a flexible flat cable, and a connector for connecting the flexible flat cable is provided on each of the lamp connecting substrate and the inverter substrate. It is what.

  According to a fourth aspect of the present invention, in the light source device according to the third aspect, a plurality of pairs of cold cathode tube lamps and connection portions are provided, and the voltage rise detecting means is a plurality of pairs of cold cathode tube lamps and connections. The plurality of voltage detection units are connected to one feedback signal line in parallel, and the feedback signal voltage is supplied to the rise detection unit via the feedback signal line. Is output.

  According to a fifth aspect of the present invention, in the light source device according to the fourth aspect, the plurality of voltage detection units are connected in parallel to one ground line, and are connected to the ground via the ground line and the inverter board. It is what has been.

  According to the first to fifth aspects of the present invention, when arc discharge occurs between the cold-cathode tube lamp and the connection portion, and the voltage of the connection portion rises to a predetermined value or more, the connection is detected by the voltage rise detection means. It is detected that the voltage of the section has risen to a predetermined value or more, and the supply of the high frequency voltage to the cold cathode tube lamp is stopped by the protection means. As a result, even if arc discharge occurs between the cold cathode tube lamp and the connecting portion, the supply of the high frequency voltage to the cold cathode tube lamp can be stopped before the connecting portion is burned out. Burnout can be prevented.

  Hereinafter, a light source device according to an embodiment of the present invention will be described with reference to the drawings. 1A, 1B, and 1C show the configuration of the light source device according to the present embodiment. The light source device 1 is a device used as a backlight light source of a liquid crystal display such as a liquid crystal television.

  The light source device 1 includes a plurality of cold-cathode tube lamps (CCFL) 2 that are turned on when a high-frequency voltage is supplied, a plurality of connection portions 3 that electrically connect the cold-cathode tube lamps 2, and a plurality of connection portions. 3 is provided with a lamp connection substrate 4 and an inverter substrate 5 for supplying a high-frequency voltage to the cold cathode tube lamp 2.

  Each cold cathode tube lamp 2 has one end connected to the inverter board 5 via the connector 21 and the conductive wire 22, and the other end connected to the connecting portion 3. Each connecting portion 3 is constituted by a conductive pattern formed on the lamp connecting substrate 4 and electrically connects a pair of cold cathode tube lamps 2a and 2b in series.

  That is, the light source device 1 has a configuration in which a pair of cold-cathode tube lamps 2 a and 2 b are electrically connected in series by a single connection portion 3. A pair of cold-cathode tube lamps 2a and 2b and a pair of cold-cathode tube lamps 2a and 2b are electrically connected in series to form a pseudo U-shaped cold-cathode tube lamp. . The light source device 1 includes a plurality of pairs of cold cathode tube lamps 2a and 2b and one connection portion 3 (pseudo U-shaped cold cathode tube lamps) connected in this way.

  The light source device 1 includes an FFC (flexible flat cable) 6 that is an electric cable for electrically connecting the lamp connection substrate 4 and the inverter substrate 5, a system control substrate 7 that controls the operation of the light source device 1, A housing 8 for storing and supporting these is provided. Each of the lamp connection substrate 4 and the inverter substrate 5 is provided with connectors 64 and 65 for connecting the FFC 6.

  The FFC 6 is connected to a connector 64 provided on the lamp connection board 4 and a connector 65 provided on the inverter board 5, and the lamp connection board 4 and the inverter board 5 are electrically connected by the FFC 6. . The inverter board 5 and the system control board 7 are electrically connected by a conductive line (not shown).

  The light source device 1 having such a configuration supplies a high-frequency voltage to each cold-cathode tube lamp 2 from the inverter substrate 5 through the conductive wire 22 and the connector 21 under the control of the system control board 7 (cold-cathode tube lamp 2a The cold-cathode tube lamps 2b are driven to light by supplying a high-frequency voltage of opposite phase to the cold-cathode tube lamps 2b (that is, supplying opposite-phase high-frequency voltages to both ends of the pseudo U-shaped cold-cathode tube lamps).

  FIG. 2 shows an electrical block configuration of the light source device 1. In addition to the above-described configuration, the light source device 1 includes an inverter 31 that generates a high-frequency voltage for lighting the cold-cathode tube lamp 2, an inverter drive circuit 32 that drives the inverter 31, and driving of the inverter 31 by the inverter drive circuit 32. And an inverter control circuit 33 for controlling. In addition, the light source device 1 detects whether or not the voltage of the connection unit 3 has increased to a predetermined value or more based on the voltage detection circuit 34 that detects the voltage of the connection unit 3 and the voltage detected by the voltage detection circuit 34. And a microcomputer 36 that controls the operation of the light source device 1. The light source device 1 includes a plurality of inverters 31 and a plurality of voltage detection circuits 34 corresponding to a plurality of pairs of cold-cathode tube lamps 2a and 2b and one connection portion 3 (pseudo U-shaped cold-cathode tube lamp). Yes.

  The inverter 31, the inverter drive circuit 32, the inverter control circuit 33, and the rise detection circuit 35 are provided on the inverter board 5. The voltage detection circuit 34 is pattern-mounted on the lamp connection board 4 and provided on the lamp connection board 4. The voltage detection circuit 34 and the rise detection circuit 35 are electrically connected via the FFC 6. The microcomputer 36 is provided on the system control board 7.

  The inverter 31 includes a transformer. When the PWM modulation current is supplied from the inverter drive circuit 32, the inverter 31 generates a high-frequency voltage by the transformer using the PWM modulation current, and the inverter terminals 31a and 31b have phases opposite to each other. Outputs high frequency voltage. One end side of the cold cathode tube lamps 2 a and 2 b is connected to the inverter terminals 31 a and 31 b through the inverter substrate 5 (conductive pattern formed on the inverter substrate 5), the conductive wire 22, and the connector 21. The cold cathode tube lamp 2 a and the cold cathode tube lamp 2 b are supplied with high-frequency voltages of opposite phases from the inverter 31 through the inverter substrate 5, the conductive wire 22, and the connector 21.

  The inverter drive circuit 32 includes a switching element. When a high frequency pulse signal is supplied from the inverter control circuit 33, the switching element performs a switching operation at a high frequency by the high frequency pulse signal, and generates a PWM modulation current. The PWM modulation current is supplied to the inverter 31. The inverter control circuit 33 generates a high frequency pulse signal and supplies the high frequency pulse signal to the inverter drive circuit 32. The microcomputer 36 controls the supply / stop of supply of the high-frequency pulse signal to the inverter drive circuit 32 by the inverter control circuit 33.

  When the high frequency pulse signal is supplied from the inverter control circuit 33 to the inverter drive circuit 32, a PWM modulation current is generated by the inverter drive circuit 32, and the PWM modulation current is supplied from the inverter drive circuit 32 to the inverter 31. Thus, a high frequency voltage is generated by the inverter 31, and the high frequency voltage is supplied from the inverter 31 to the cold cathode tube lamps 2a and 2b, so that the cold cathode tube lamps 2a and 2b are driven to light. When the supply of the high frequency pulse signal from the inverter control circuit 33 to the inverter drive circuit 32 is stopped, the generation of the PWM modulation current by the inverter drive circuit 32 is stopped, and the PWM modulation current from the inverter drive circuit 32 to the inverter 31 is stopped. Supply stops. Thereby, the generation of the high frequency voltage by the inverter 31 is stopped, the supply of the high frequency voltage from the inverter 31 to the cold cathode tube lamps 2a and 2b is stopped, and the cold cathode tube lamps 2a and 2b are turned off.

  The voltage detection circuit 34 detects the voltage of the connection unit 3 and outputs the detected voltage as a feedback signal voltage. The plurality of voltage detection circuits 34 are connected in parallel to one feedback signal line 37, and are connected to the rise detection circuit 35 through one feedback signal line 37. That is, the voltage detection circuit 34 outputs a feedback signal voltage to the rise detection circuit 35 via one feedback signal line 37. The plurality of voltage detection circuits 34 are connected in parallel to one ground line 38, and are connected to the ground via one ground line 38.

  Based on the feedback signal voltage output from the voltage detection circuit 34, the rise detection circuit 35 detects whether or not the voltage at the connection unit 3 has risen above a predetermined value, and the voltage at the connection unit 3 exceeds the predetermined value. A protection signal is output when the rise is detected. The rise detection circuit 35 is connected to the microcomputer 36 via the protect line 39 and outputs a protect signal to the microcomputer 36 via the protect line 39. The voltage detection circuit 34 and the rise detection circuit 35 constitute voltage rise detection means. Details of the voltage detection circuit 34 and the rise detection circuit 35 will be described later.

  When the rise detection circuit 35 detects that the voltage of the connection unit 3 has risen above a predetermined value (that is, when the protect signal is output from the rise detection circuit 35), the microcomputer 36 A protection operation for stopping the supply of the high-frequency voltage to the cathode tube lamps 2a and 2b is performed. At this time, the microcomputer 36 stops the supply of the high-frequency voltage to the cold-cathode tube lamps 2a and 2b by stopping the generation of the high-frequency voltage by the inverter 31. That is, the microcomputer 36 stops the supply of the high frequency pulse signal to the inverter drive circuit 32 by the inverter control circuit 33. Thereby, the generation of the PWM modulation current by the inverter drive circuit 32 is stopped, the supply of the PWM modulation current from the inverter drive circuit 32 to the inverter 31 is stopped, and the generation of the high frequency voltage by the inverter 31 is stopped, The supply of the high frequency voltage from the inverter 31 to the cold cathode tube lamps 2a and 2b is stopped. The microcomputer 36 constitutes a protection means.

  The voltage detection circuit 34 and the rise detection circuit 35 will be described. The voltage detection circuit 34 includes capacitors C1 and C2, resistors R1 and R2, and a diode D1. One end of the capacitor C <b> 1 is connected to the connection portion 3. One end of the capacitor C2 is connected to the other end of the capacitor C1, and the other end is connected to the ground line 38 (connected to the ground via the ground line 38). One end of the resistor R1 is connected between the capacitor C1 and the capacitor C2. One end of the resistor R2 is connected to the other end of the resistor R1, and the other end is connected to the ground line 38 (connected to the ground via the ground line 38). The diode D1 has an anode connected between the resistors R1 and R2, and a cathode connected to the feedback signal line 37 (connected to the rise detection circuit 35 via the feedback signal line 37). The connection point between the cold cathode tube lamp 2a and the connection portion 3 and the connection point between the cold cathode tube lamp 2b and the connection portion 3 are pseudo ground points.

  The rise detection circuit 35 includes a transistor Tr1, capacitors C3, C4, and C5, and a resistor R3. The transistor Tr1 has a base connected to the feedback signal line 37, a collector connected to the protect line 39 (connected to the microcomputer 36 via the protect line 39), and an emitter connected to the ground. One end of each of the capacitors C3, C4, and C5 is connected between the feedback signal line 37 and the base of the transistor Tr1, and the other end is connected to the ground. The resistor R3 is connected in parallel with the capacitor C3.

  With the voltage detection circuit 34 and the rise detection circuit 35 configured as described above, the voltage of the connection unit 3 is divided by the capacitors C1 and C2 and the resistors R1 and R2, and the divided voltage is rectified by the diode D1. The rectified voltage is output to the feedback signal line 37 as a feedback signal voltage. As shown in FIG. 3, when a connection failure occurs in the connection between the cold cathode tube lamp 2 and the connection portion 3 (an arc discharge (spark) occurs between the cold cathode tube lamp 2 and the connection portion 3), The voltage (AC voltage) at the connection part 3 (pseudo ground point) is increased several times as compared with the normal time when no connection failure occurs in the connection between the tube lamp 2 and the connection part 3, and the feedback signal voltage ( The pulsating voltage after being rectified by the diode D1 is increased.

  The feedback signal voltage output to the feedback signal line 37 is smoothed by the capacitors C3, C4, C5, and the resistor R3, and the transistor Tr1 is turned on according to the magnitude of the smoothed feedback signal voltage. Turn off. The feedback signal voltage smoothed by the capacitors C3, C4, C5 and the resistor R3 corresponds to the feedback signal voltage of the feedback signal line 37 and corresponds to the voltage of the connection unit 3. Therefore, the transistor Tr1 is turned on / off according to the voltage of the connection portion 3.

  The transistor Tr1 is turned on when the voltage at the connection part 3 is equal to or higher than a predetermined value (voltage value when arc discharge occurs between the cold cathode tube lamp 2 and the connection part 3), and the voltage at the connection part 3 is Turns off when below a predetermined value. When the transistor Tr1 is on, the voltage level of the collector of the transistor Tr is low, a signal with a low voltage level is output to the protect line 39, and when the transistor Tr1 is off, the voltage level of the collector of the transistor Tr is high. A signal having a high voltage level is output to the protect line 39.

  That is, when the connection between the cold-cathode tube lamp 2 and the connection portion 3 is normal and no connection failure occurs, the transistor Tr1 is turned off, and the voltage of the connection portion 3 is at a normal value on the protect line 39. A high level signal is output as a normal signal. When a connection failure occurs in the connection between the cold cathode tube lamp 2 and the connection portion 3, the transistor Tr1 is turned on, and a protect signal indicating that the voltage of the connection portion 3 has risen to a predetermined value or more is applied to the protect line 39. As a result, a low level signal is output. In this way, the voltage detection circuit 34 and the rise detection circuit 35 detect whether or not the voltage of the connection unit 3 has risen above a predetermined value.

  According to the light source device 1 having such a configuration, when arc discharge occurs between the cold cathode tube lamp 2 and the connection portion 3 and the voltage of the connection portion 3 rises to a predetermined value or more, the voltage detection circuit 34 and The rise detection circuit 35 detects that the voltage of the connecting portion 3 has risen to a predetermined value or more, and the microcomputer 36 stops the supply of the high frequency voltage to the cold cathode tube lamp 2. As a result, even if arc discharge occurs between the cold cathode tube lamp 2 and the connection portion 3, the supply of the high frequency voltage to the cold cathode tube lamp 2 can be stopped before the connection portion 3 is burned out. The connecting part 3 can be prevented from burning out.

  In addition, this invention is not restricted to the structure of the said embodiment, A various deformation | transformation is possible. For example, the rise detection circuit may be provided on the lamp connection substrate. Further, the connection portion for electrically connecting the 11 cold cathode tube lamps is not limited to the conductive pattern formed on the lamp connection substrate, and may be formed of a metal plate. Further, the light source device of the present invention is not limited to a backlight light source of a liquid crystal display, and can be used as a light source for other purposes.

(A) is sectional drawing seen from the back side which shows schematic structure of the light source device which concerns on one Embodiment of this invention, (b) is sectional drawing seen from the same lower side, (c) was seen from the lateral side Sectional drawing. The electric block block diagram of the light source device. The figure which shows the voltage waveform of the voltage of the connection part of the light source device, and the voltage waveform of a feedback signal voltage. (A) is sectional drawing seen from the back side of the conventional light source device, (b) is sectional drawing seen from the lower side, (c) is sectional drawing seen from the lateral side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source device 2, 2a, 2b Cold cathode tube lamp 3 Connection part 4 Substrate for lamp connection 5 Inverter substrate 6 FFC (flexible flat cable)
7 System control board 8 Housing 21 Connector 22 Conductive wire 31 Inverter 32 Inverter drive circuit 33 Inverter control circuit 34 Voltage detection circuit (voltage rise detection means)
35 rise detection circuit (voltage rise detection means)
36 Microcomputer (protection means)
37 Feedback signal line 38 Ground line 39 Protect line 64, 65 Connector

Claims (5)

A pair of cold-cathode tube lamps, a connection part for electrically connecting the pair of cold-cathode tube lamps in series, and an inverter for generating a high-frequency voltage for lighting the pair of cold-cathode tube lamps A light source device in which the pair of cold-cathode tube lamps are driven to be driven by supplying a high-frequency voltage from the inverter to the pair of cold-cathode tube lamps,
Voltage rise detection means for detecting whether or not the voltage of the connection portion has risen above a predetermined value;
Protection that performs a protective operation to stop the high-frequency voltage from being supplied from the inverter to the cold-cathode tube lamp when the voltage rise detecting means detects that the voltage of the connection portion has risen to a predetermined value or more. Means,
A light source device characterized by that. A lamp connecting substrate provided with the connecting portion;
An inverter board provided with the inverter,
The voltage rise detection means includes
A voltage detection unit that detects a voltage of the connection unit and outputs the detected voltage as a feedback signal voltage;
A rise detection unit that detects whether or not the voltage of the connection unit has risen above a predetermined value based on the feedback signal voltage output from the voltage detection unit;
The voltage detection unit is provided on the lamp connection substrate,
The rise detection unit is provided on the inverter board,
The voltage detection unit and the rise detection unit are connected via an electric cable.
The light source device according to claim 1. The electrical cable is a flexible flat cable,
Each of the lamp connection board and the inverter board is provided with a connector for connecting the flexible flat cable.
The light source device according to claim 2. A plurality of sets of the pair of cold cathode tube lamps and connection portions,
The voltage rise detection means includes a plurality of the voltage detection units corresponding to the plurality of pairs of cold cathode tube lamps and connection units,
The plurality of voltage detection units are connected in parallel to one feedback signal line, and output the feedback signal voltage to the rise detection unit via the feedback signal line.
The light source device according to claim 3. The plurality of voltage detection units are connected in parallel to one ground line, and are connected to the ground via the ground line and the inverter board.
The light source device according to claim 4.