JP4898745B2 - Hot cathode discharge tube lighting circuit - Google Patents

Description

  The present invention relates to a hot cathode discharge tube lighting circuit for lighting a hot cathode discharge tube used as a backlight of a liquid crystal display device.

  Liquid crystal panels are used as display screens for liquid crystal televisions, navigation systems, amusement devices, etc., but the largest market is large screen liquid crystal televisions. As a backlight for a liquid crystal screen, a cold cathode fluorescent tube is mainly used. However, use of a hot cathode fluorescent tube is being studied as the screen becomes larger.

  In order to drive the hot cathode fluorescent tube (HCFL), a heater power source for heating the filament and a discharge power source for discharging are required. These power sources were obtained by boosting the power source voltage through a transformer. Generally, a configuration for applying a high voltage is employed. Furthermore, a circuit for detecting an abnormality such as a disconnection or a short circuit in the discharge tube portion or a circuit for detecting an abnormality such as a disconnection or a short circuit of the heater is required. These functions are composed of an inverter transformer and a peripheral circuit. However, the circuit configuration becomes complicated, and the size of the apparatus and the circuit become inevitable.

Further, since it is necessary to light a plurality of discharge tubes in parallel in a large-screen liquid crystal display device, it is necessary to prevent variations in luminance among these discharge tubes. Therefore, it is necessary to arrange a balance circuit (balancer) between the secondary side of the step-up transformer of the discharge power supply and the discharge tube, and a coil generally called a Jin balancer coil is used.
Japanese Patent No. 2643961 JP-A-6-140179

  The present invention provides a lighting circuit for a hot cathode discharge tube, which can reduce the number of parts of an inverter unit for lighting a hot cathode discharge tube, and can reduce the mounting area by integration and combination. Is. Further, the device and circuit are miniaturized by integrating a winding for synchronization and abnormality detection in a transformer portion for heater, which occupies a large area in the circuit.

  The present invention solves the above problem by integrally forming a discharge transformer and an abnormality detection winding integrally with a heater transformer. That is, a heater voltage is applied to each electrode of a plurality of hot cathode discharge tubes via a heater transformer, and an output voltage of an inverter transformer is applied to the electrodes of the plurality of hot cathode discharge tubes to thereby apply the plurality of hot cathode discharges. A hot cathode discharge tube lighting circuit for lighting a tube is characterized in that a tertiary winding is provided in the heater transformer of each hot cathode discharge tube.

  In addition, a heater voltage is applied to each electrode of a plurality of hot cathode discharge tubes via a heater transformer, and the output voltage of the inverter transformer is composed of a primary coil and a secondary coil on the electrodes of the plurality of hot cathode discharge tubes. In the hot-cathode discharge tube lighting circuit for lighting the plurality of hot-cathode discharge tubes by applying them through the balancer, the primary side of the heater transformer of the hot-cathode discharge tube is the heater power supply and the secondary side is the hot-cathode discharge. A plurality of balancers connected to the electrodes of the tube and having a tertiary winding and connected to the hot cathode discharge tube are connected in series on the primary side and the output of the inverter transformer and the hot cathode on the secondary side, respectively. It is characterized in that the electrodes of the discharge tube are connected.

  In addition, a heater voltage is applied to each electrode of a plurality of hot cathode discharge tubes via a heater transformer, and the output voltage of the inverter transformer is configured by a primary coil and a secondary coil to the electrodes of the plurality of hot cathode discharge tubes. In the hot-cathode discharge tube lighting circuit for lighting the plurality of hot-cathode discharge tubes by applying them through the balancer, the primary side of the heater transformer of the hot-cathode discharge tube is the heater power supply and the secondary side is the hot-cathode discharge. A plurality of balancers connected to the electrodes of the tube and having a tertiary winding and connected to the hot cathode discharge tube are connected in series on the primary side and the output of the inverter transformer and the hot cathode on the secondary side, respectively. It is characterized by being connected to the electrode of the discharge tube and having a tertiary winding.

  According to the present invention, the heater driving transformer inherent to the hot cathode discharge tube and the balancer coil for controlling the lamp current of the hot cathode tube can be integrated to save a large space. This transformer can be constituted by a transformer having a withstand voltage separation structure having a primary / secondary winding configuration.

  In addition, since the tertiary winding can be formed integrally with the heater transformer, it is easy to detect abnormalities such as heater disconnection and short circuit, or the heater current value is made the same to improve current variation. It becomes possible to do.

  Embodiments of the present invention will be described below with reference to the drawings. An example of a transformer used in the circuit according to the present invention is shown in FIG. It is composed of a magnetic core 41, two bobbins 42 and 43, and windings wound around these bobbins. The bobbin 42 has a so-called Jin coil primary winding and tertiary winding 44 as a balancer coil. And the secondary winding 45 of the Jin coil is wound. At this time, the number of winding grooves of the secondary winding 45 is determined according to the withstand voltage. The bobbin 43 is wound with a primary winding and tertiary winding 46 of the heater transformer and a secondary winding 47 of the heater transformer. The end of each winding is connected to a terminal implanted in the bobbin. In other words, in this integrated transformer, in addition to the primary and secondary windings of the heater transformer, a tertiary winding that acts as a detection winding, etc. is added to the primary and secondary windings of the balancer coil. In addition, a tertiary winding that acts as a detection winding is wound.

  FIG. 1 is a circuit diagram showing an embodiment of the present invention. A heater driving current is applied to both ends of the hot cathode discharge tube 10 via a heater transformer. That is, the primary side of the heater transformer is connected to the heater power source, and the secondary side is connected to the hot cathode discharge tube 10, respectively. Tertiary windings are provided for each heater transformer, and these are connected to an abnormality detection circuit to detect changes in the output voltage (current) when abnormality such as heater disconnection or short circuit occurs. A detection signal is input to the detection circuit. When an abnormality signal is input by the action of the abnormality detection circuit, the heater and the power supply are shut off to protect the circuit and device.

Lighting of the discharge tube 10 is performed by the power supply voltage is input through the secondary side of Jin coil is boosted by insulating transformer. Primary side of Jin coil of the plurality of discharge tubes are connected to each other, it acts to the tube current of the plurality of discharge tubes to the same value. This eliminates variations in luminance among the plurality of discharge tubes. Further, the Jin coil is provided with a tertiary winding, which detects an abnormality such as a disconnection or a short circuit of the discharge tube by detecting an abnormality in the output of the Jin coil. In the figure, the connection is omitted, but normally used feedback is performed, and the power is cut off in the event of an abnormality.

  FIG. 2 is a circuit diagram showing another embodiment of the present invention, and the basic configuration is the same as the example of FIG. In this example, since the tertiary windings of the heater transformer are connected to each other, they function as a current balancer for the heater transformer. That is, since the effect of correcting the variation in the output of the heater transformer is performed, the variation in the heater current applied to the discharge tube can be eliminated.

Figure 3 is a circuit diagram showing another embodiment of the present invention, in this example constitutes a loop as a whole is connected to the tertiary winding of the primary winding and the heater transformer Jin coils in series. With this connection configuration, it is possible to balance the current of the discharge part and to obtain stable lighting and current balance of the heater part simultaneously by synchronizing the discharge part and the heater part.

  In the above example, the hot cathode discharge tube and the balancer coil / heater transformer have been described as one-to-one. However, the present invention can also be used when a plurality of hot cathode discharge tubes are driven by one heater transformer. Further, even when the balancer coil is replaced with other ballast means, the heater transformer according to the present invention having the tertiary winding in the heater transformer can be applied. As for the transformer, the two bobbins shown in FIG. 4 are not integrated, but the primary to tertiary windings of the heater transformer may be wound around the bobbin 52 as shown in FIG.

  INDUSTRIAL APPLICABILITY The present invention is a hot cathode discharge tube lighting circuit that can be used for all hot cathode discharge tubes and is particularly suitable for large liquid crystal display devices such as liquid crystal televisions.

Circuit diagram showing an embodiment of the present invention Circuit diagram showing another embodiment of the present invention Circuit diagram showing another embodiment of the present invention A perspective view of an example of a transformer used in the present invention The perspective view of the other example of the transformer used for this invention

Explanation of symbols

41: Core
42, 43: Bobbin
44: Primary winding and tertiary winding of Jin coil
45: Secondary winding of Jin coil
46: Heater transformer primary and tertiary windings
47: Secondary winding of heater transformer

Claims (1)

A heater voltage is applied to each electrode of the plurality of hot cathode discharge tubes via a heater transformer, and an output voltage of the inverter transformer is configured by a primary coil and a secondary coil on the electrodes of the plurality of hot cathode discharge tubes. In a hot cathode discharge tube lighting circuit for lighting the plurality of hot cathode discharge tubes by applying through a balancer,
Each heater transformer of the hot cathode discharge tube has a primary side connected to a heater power source and a secondary side connected to an electrode of the hot cathode discharge tube, and has a tertiary winding, and the tertiary windings are connected in series. And
The plurality of balancers connected to the hot cathode discharge tube include a primary winding connected in series, a secondary side connected to the output of the inverter transformer and the electrode of the hot cathode discharge tube, respectively, and a tertiary winding .
Together with the primary winding between the third winding and the balancer of the heater transformer being connected in series, the hot cathode discharge tube lighting circuit heater transformer and balancer wherein Rukoto is integral.

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