Abstract:
A liquid crystal television receiver includes a DC power supply to generate and output tuning DC power, a receiving portion, a display portion, and a series regulator. Preferably, the receiving portion is fed the tuning DC power and receives a video signal, the display portion includes an active-matrix liquid crystal panel, a gate driver to generate a gate-on signal and drive a gate line and a data driver to drive a data line, allowable ranges of voltage of the tuning DC power and the gate-on DC power share a common range in which a voltage of the tuning DC power is set, the tuning DC power is fed to the gate driver, and the series regulator is provided on at least one of power supply paths to feed the tuning DC power from the DC power supply to the gate driver and to the receiving portion, and removes noise component.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a liquid crystal television receiver having a receiving portion, which uses a variable-capacitance diode as an element of a receiving tuning circuit, and a display portion using a liquid crystal panel as a display device.  
         [0003]     2. Description of the Related Art  
         [0004]     As shown in  FIG. 3 , in a television receiver (hereunder referred to as first related art) employing a liquid crystal panel as a display device, a display portion  91  for displaying video signals outputted from a receiving portion  2  is provided with a gate driver  11  for driving gate lines of the liquid crystal panel  12 , and with a data driver  14  for driving data lines thereof. Further, the display portion  91  is also provided with a DC power supply portion  3  for generating and outputting 3.3 V DC power  21  needed by the receiving portion  2 . Moreover, the DC power supply portion  3  generates and outputs 3.3 V tuning DC power  22  required to generate tuning signals applied to a variable-capacitance diode  18  of a tuning circuit  17  of a tuner  16  provided in the receiving portion  2 . On the other hand, in a display portion  91 , a DC-DC converter  15  using the 3.3 V DC power  21  as operating power thereof is provided and generates 12 V DC power needed by the data driver  14 . Also, a charge pump  92  employing 12 V DC power  23  as operating power thereof is provided therein and generates 33 V gate-on DC power, which is needed by the gate driver  11  for generating gate-on signals.  
         [0005]     Furthermore, the following related art (hereunder referred to as second related art) has been proposed. That is, in this related art, a tuner unit ( 22   a ) is configured in such a way as to be able to be attached to various kinds of liquid crystal display units ( 21 ). Further, the tuner unit ( 22   a ) is provided with a power supply portion ( 90 ) for generating power needed by the liquid crystal display unit ( 21 ). Furthermore, this related art is adapted so that “a liquid crystal display kind signal (MS) from a liquid crystal display kind signal generating portion ( 64 ) is outputted to the power supply portion ( 90 ) of a tuner unit ( 22   a ), and drive power associated with the kind of a liquid crystal display portion ( 60 ) is supplied to the liquid crystal display portion ( 60 )” (see for example, JP-A-8-5986 (Paragraph No. [0056], and FIGS.  1  to  3 )).  
       SUMMARY OF THE INVENTION  
       [0006]     However, an electric power supply has a slight instability in some regions, where a stabilizing mechanism is necessary for a television receiver. The stabilizing mechanism can be implemented by a series regulator. Although, in order to reduce a cost a television receiver in other area can dispense with the stabilizing mechanism, television receivers in market include the stabilizing mechanism for safety.  
         [0007]     The use of the first related art causes the following problems. That is, although a charge pump  92  is used for generating gate-on DC power  93 , which is needed by the gate driver  11 , this charge pump  92  is a circuit requiring plural capacitors and plural diodes, so that the size of the circuit is relative large. This has resulted in increase in the number of components and in rise in the cost of the components.  
         [0008]     Further, the second related art is techniques of generating drive power associated with the kind of the liquid crystal display unit, to which the tuner unit is attached, in the tuner unit and supplying the generated power to the liquid crystal display portion. Thus, from the viewpoint of resolving the problems of the first related art, the second related art is difficult to apply.  
         [0009]     The invention is created to solve the problems. An object of the invention is to provide a liquid crystal television receiver enabled to prevent increase in the number of components thereof and decrease in receiver sensitivity due to the sneaking of noises, which occurs when the gate driver drives the gate lines, by supplying tuning DC power, which is to be supplied to a receiving portion for performing an analog operation, also to a gate driver, which performs a digital operation, as gate-on DC power, to thereby eliminate the use of a charge pump for generating gate-on DC power in a configuration thereof, in which there is a common range between an allowable range of voltages corresponding to the tuning DC power and an allowable range of voltages corresponding to the gate-on DC power.  
         [0010]     Further, an object of the invention is to provide a liquid crystal television receiver enabled to prevent increase in the number of components thereof by supplying tuning DC power, which is to be supplied to a receiving portion for performing an analog operation, also to a gate driver, which performs a digital operation, as gate-on DC power to thereby eliminate the use of a charge pump for generating gate-on DC power in a configuration thereof, in which there is a common range between an allowable range of voltages corresponding to the tuning DC power and an allowable range of voltages corresponding to the gate-on DC power.  
         [0011]     To solve the foregoing problems, according to an aspect of the invention, there is provided a liquid crystal television receiver including a DC power supply to generate and to output tuning DC power providing a predetermined voltage, a receiving portion to output a video signal, a display portion to display the video signal, and a lowpass filter. Preferably, the receiving portion is fed the tuning DC power, sets a tuning frequency of a tuning circuit at a frequency corresponding to a received channel by applying a tuning signal to a variable-capacitance diode included in the tuning circuit, and receives a video signal, the tuning signal being generated according to the tuning DC power, the display portion includes an active-matrix liquid crystal panel, a gate driver to generate a gate-on signal and to drive a gate line of the active-matrix liquid display panel using the gate-on signal which turns on a gate by using gate-on DC power as operating power, and a data driver to drive a data line of the active-matrix liquid crystal panel, an allowable range of voltage corresponding to the tuning DC power and an allowable range of voltage corresponding to the gate-on DC power share, at least partly, a common allowable range of voltage, the tuning DC power is fed to the gate driver as the gate-on DC power, the lowpass filter is provided on at least one of a first power supply path to feed the tuning DC power from the DC power supply to the gate driver and a second power supply path to feed the tuning DC power from the DC power supply to the receiving portion and removes noise component which is generated when the gate driver drives the gate lines, and a voltage corresponding to the tuning DC power is set to be within the common allowable range of voltage.  
         [0012]     That is, the gate driver is operated by the tuning DC power supplied as a substitute for the gate-on DC power. A noise component, which sneaks through a path of the tuning DC power into the receiving portion, is removed by the lowpass filer, so that the noise component is not transmitted to the receiving portion.  
         [0013]     According to another aspect of the invention, there is provided a liquid crystal television receiver including a DC power supply to generate and to output tuning DC power providing a predetermined voltage, a receiving portion to output a video signal, a display portion to display the video signal, and a series regulator. Preferably, the receiving portion is fed the tuning DC power, sets a tuning frequency of a tuning circuit at a frequency corresponding to a received channel by applying a tuning signal to a variable-capacitance diode included in the tuning circuit, and receives a video signal, the tuning signal being generated according to the tuning DC power, the display portion includes an active-matrix liquid crystal panel, a gate driver to generate a gate-on signal and to drive a gate line of the active-matrix liquid display panel using the gate-on signal, which turns on a gate by using gate-on DC power as operating power, and a data driver to drive a data line of the active-matrix liquid crystal panel, an allowable range of voltage corresponding to the tuning DC power and an allowable range of voltage corresponding to the gate-on DC power share, at least partly, a common allowable range of voltage, the tuning DC power is fed to the gate driver as the gate-on DC power, the series regulator is provided on at least one of a first power supply path to feed the tuning DC power from the DC power supply to the gate driver and a second power supply path to feed the tuning DC power from the DC power supply to the receiving portion, removes noise component, which is generated when the gate driver drives the gate lines, and stabilize a voltage applied to the gate driver, and a voltage corresponding to the tuning DC power is set to be within the common allowable range of voltage.  
         [0014]     That is, the gate driver is operated by the tuning DC power supplied as a substitute for the gate-on DC power. A voltage applied to the gate driver, which is different from the tuning DC power voltage, is controlled to be stabilized, as well as a noise component, which sneaks through a path of the tuning DC power into the receiving portion, is removed by the series regulator, so that the noise component is not transmitted to the receiving portion.  
         [0015]     Further, according to yet another aspect of the invention, there is provided a liquid crystal television receiver including a DC power supply to generate and to output tuning DC power providing a predetermined voltage, a receiving portion to output a video signal, and a display portion to display the video signal. Preferably, the receiving portion is fed the tuning DC power, sets a tuning frequency of a tuning circuit at a frequency corresponding to a received channel by applying a tuning signal to a variable-capacitance diode included in the tuning circuit, and receives a video signal, the tuning signal being generated according to the tuning DC power, the display portion includes an active-matrix liquid crystal panel, a gate driver to generate a gate-on signal and to drive a gate line of the active-matrix liquid display panel using the gate-on signal which turns on a gate by using gate-on DC power as operating power, and a data driver to drive a data line of the active-matrix liquid crystal panel, an allowable range of voltage corresponding to the tuning DC power and an allowable range of voltage corresponding to the gate-on DC power share, at least partly, a common allowable range of voltage, the tuning DC power is fed to the gate driver as the gate-on DC power, and a voltage corresponding to the tuning DC power is set to be within the common allowable range of voltage.  
         [0016]     That is, the gate driver is operated by the tuning DC power supplied as a substitute for the gate-on DC power. The constitution of directly connecting the DC power supply with the gate driver reduces a cost. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Preferred embodiments of the present invention will be described in detail based on the following figures, wherein:  
         [0018]      FIG. 1  is a block diagram showing the electrical configuration of an embodiment of a liquid crystal television receiver;  
         [0019]      FIG. 2  is a circuit diagram showing the electrical connection between a connection path of a tuning DC power supply and a series regulator; and  
         [0020]      FIG. 3  is a block diagram showing the electrical configuration of the related art. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Hereinafter, an embodiment of the invention is described by referring to the accompanying drawings.  
         [0022]      FIG. 1  is block diagram showing the electrical configuration of an embodiment of a liquid crystal television receiver according to the invention. In this figure, a block, whose configuration is the same as that of a component of the related art shown in  FIG. 3 , is designated by reference character, which is the same as that denoting the component of the related art in  FIG. 3 .  
         [0023]     As illustrated in  FIG. 1 , a switching power supply  4  generates 12 V DC power from a commercial power source  31 . Then, the switching power supply  4  sends the generated 12 V DC power  24  to the DC power supply  3  and the backlight  5 . The DC power supply  3  generates 3.3 V DC power  21  from the 12 V DC power  24 . Also, the DC power supply  3  generates 33 V DC power  22  serving as analog power (tuning DC power) used for permitting a tuner  16  of the receiving portion  2  to use the tuning frequency of a tuning circuit  17  as a target frequency. Then, the DC power supply  3  sends the generated DC power  22  to the receiving portion  2 . Additionally, the DC power supply  3  sends the tuning DC power  22 , which is analog power, to the gate driver  11 , which performs a digital operation, through the series regulator  6  as 33 V gate-on DC power. That is, the 33 V DC power supply  22  is used as a power source for the receiving portion  2 , which is an analog circuit, and also used as a power source for the gate drier  11  that is a circuit block provided in a display portion  1 , which is independent of the receiving portion  2 , and that performs a digital operation.  
         [0024]     The receiving portion  2  receives a commercial broadcast on a channel designated by a controller  7 , and sends video signals, which are obtained by being received, to a signal processor  13  of the display portion. Thus, the receiving portion  2  has a tuner  16 . Further, the tuner  16  sets the tuning frequency of the tuning circuit  17  at a frequency associated to the received channel by applying a tuning signal, which is generated according to the 33 V tuning DC power  22 , to a variable-capacitance diode  18 , which is an element of the tuning circuit  17 . Incidentally, the allowable range of voltages corresponding to the tuning DC power supply  22  of the receiving portion  2  is a neighborhood range of 33 V.  
         [0025]     The display portion  1  displays video signals, which are sent from the receiving portion  2 , on a liquid crystal panel  12 . Thus, the display portion  1  has the gate driver  11 , the signal processor  13 , and the data driver (source driver)  14 , and a DC-DC converter  15 . The signal processor  13  is a block using 3.3 V DC power  21  as operating power. Further, the signal processor  13  generates a signal, which represents scanning timing, from the video signals sent from the receiving portion  2  and sends the generated signal to the gate driver  11 . Also, the signal processor  13  generates signals, which respectively represent the luminances of primary colors, from the video signals and sends the generated signals to the data driver  14 . The DC-DC converter  15  generates 12 V DC power  23  (the voltage corresponding to which may have another value (for example, 9 V or 10 V) from the 3.3 V DC power  21  and sends the generated power to the data driver  14 .  
         [0026]     The gate driver  11  is a block using 33 V gate-on DC power  221 , which is sent from the series regulator  6 , and the 3.3 V DC power  21  as operating power (the value of current corresponding to the gate-on DC power  221  is 10 mA at a maximum, and usually several mA). Further, the gate driver  11  generates a gate-on signal according to a signal representing timing, which is sent from the signal processor  13 , by using the 33 V gate-on DC power. Furthermore, the gate lines of the liquid crystal panel  12  are driven by the generated gate-on signals. Incidentally, in the gate driver  11 , the allowable range of voltages corresponding to the gate-on DC power  221  is the neighborhood range of 33 V.  
         [0027]     The data driver  14  is a block using 12 V DC power  23 , which is sent from the DC-DC converter  15 , and the 3.3 V DC power as operating power. Further, the data driver  14  generates data signals representing luminances according to signals that are sent from the signal processor  13  and that represent the luminances of primary colors. Also, the data driver  14  drive data lines (source lines) of the liquid crystal panel  12  according to the generated data signals.  
         [0028]     The backlight  5  has a cold cathode tube serving as a light source, and a light guide plate for changing light, which is generated by the cold cathode tube, to surface-like light. Also, the backlight  5  has a boosting circuit  19  for generating a high voltage needed by the cold cathode tube.  
         [0029]     The control portion  7  mainly comprises a microcomputer, which is operated by the 3.3 V DC power  21 , and controls a primary operation of the television receiver. Thus, the control portion  7  controls a channel received by the receiving portion  2 . Also, the control portion  7  controls display in the display portion  1 . That is, the control portion  7  controls the brightness, the contrast, and the hue of an image displayed on the liquid crystal panel  12 .  
         [0030]     The series regulator  6  serves as a filter for preventing reduction in the receiver sensitivity in the receiving portion  2  from being caused by the sneaking of noise components, which are generated when the gate driver  11  drives gate lines, toward the receiving portion  2 . Thus, as illustrated in  FIG. 2 , the series regulator  6  has a capacitor C 4 . Incidentally, the capacitor C 4  is connected to a terminal of the transistor T 1 , which is provided at the side of the gate driver  11 , and to the ground level.  
         [0031]     A voltage of the tuning DC power is slightly different from the voltage of the gate driver, i.e. the voltage of the gate driver is lower. The object of the circuit in  FIG. 2  is to adjust a voltage to the voltage of the tuning DC power to the voltage of the gate driver.  
         [0032]     On the other hand, in the DC power supply  3 , an output of a secondary coil is rectified and smoothed by using a rectifying/smoothing circuit consisting of a diode D 1  and a capacitor C 1 . Thus, the 33 V DC power  22  is generated. Also, a capacitor C 2  is connected between a position in the vicinity of an output point of the DC power supply  22  and the ground level so as to remove high-frequency components (noise components generated when the gate driver  11  drives gate lines) Furthermore, a printed wiring pattern is formed so that the path  22   a  of the tuning DC power to be sent to the series regulator  6  and the path  22   b  of the turning DC power to be sent to the receiving portion  2  branch out in the vicinity of the position of a terminal of the capacitor C 2 .  
         [0033]     Thus, in the case where the gate driver  11  is viewed from the side of the receiving portion  2  through the path of the 33 V power, the gate driver  11  is connected thereto through a series regulator consisting of the resistors R 1 , R 2 , transistor T 1 , zener diode Z 1 , and capacitors C 3  and C 4 . Thus, the noise components, which are generated from the gate driver  11  and sneak into the receiving portion  2 , are effectively removed, and the voltage is stabilized.  
         [0034]     An operation of the embodiment of the aforementioned configuration is described hereinbelow.  
         [0035]     The receiving portion  2  is supplied with the tuning DC power  22  corresponding to a voltage in the allowable range. Thus, the tuner  16  generates a tuning signal according to the tuning DC power  22  and applies the generated signal to the variable-capacitance diode  18  that is a constituent element of the tuning circuit  17 . Therefore, the tuning frequency of the tuning circuit  17  is set at a frequency associated with the received channel. Consequently, video signals in the received channel are sent to the display portion  1 .  
         [0036]     On the other hand, the gate driver  11  of the display portion  1  is supplied with the gate-on DC power (or the tuning DC power)  221  corresponding to a voltage in the allowable range. Thus, the gate driver  11  generates the gate-on signals by using the gate-on DC power  221 , and drives the gate lines of the liquid crystal panel  12 . Further, the data driver  14  drives the data lines of the liquid crystal panel  12 . Consequently, in the liquid crystal panel  12 , video signals in the received channel are displayed.  
         [0037]     During the aforementioned operation is performed, the noise components caused due to the driving of the gate lines by the gate driver  11  leak to the path  221  for the gate-on DC power. However, regarding the path of the 33V DC power, the gate driver  11  and the receiving portion  2  are separated from each other by the π-type filter consisting of the capacitor C 2  and the series regulator  6 , which are provided in the DC power supply  3 . Thus, the noise components leaking out to the path  221  are removed at a high rate, and do not intrude into the receiving portion  2 . The voltage of the gate driver is stabilized. Consequently, the receiving portion  2  can receive a commercial broadcast without reducing the sensitivity thereof.  
         [0038]     Incidentally, the invention is not limited to the aforementioned embodiment. In the case that there is a common range between the allowable range of voltages corresponding to the tuning DC power and the allowable range of voltages corresponding to the gate-on DC power, the invention can similarly be applied to a case where the voltage corresponding to the tuning DC power and the voltage corresponding to the gate-on DC power are other voltages.  
         [0039]     Additionally, although it has been described that the series regulator  6  is provided on the path  22   a  from the DC power supply  3  to the gate driver  11 , the receiver may be configured so that the series regulator  6  is provided on the path  22   b  from the DC supply  3  to the receiving portion  2 .  
         [0040]     Moreover, a lowpass filter can be provided in place of the series regulator  6 , in order to remove the noise component and to reduce a cost.  
         [0041]     As described above, according to the invention, the tuning DC power outputted by the DC power supply is fed to the gate driver as the gate-on DC power. Additionally, the voltage corresponding to the tuning DC power is set to be within a range of volts allowed by both the receiving portion and the gate driver. Further, the lowpass filter for removing noise components generated by driving the gate lines by the gate driver is provided on at least one of the power path for feeding the tuning DC power to the gate driver, and the power path for feeding the tuning DC power from the DC power supply to the receiving portion. Therefore, the gate driver is operated by the tuning DC power supplied instead of the gate-on DC power. Further, the noise components, which are generated at the gate driver and would intrude into the receiving portion through the path for the tuning DC power, are removed by the lowpass filter, so that the noise components are not transmitted to the receiving portion. Thus, the charge pump is unnecessary. Consequently, increase in the number of parts can be prevented. Also, decrease in the receiver sensitivity due to the sneaking of noises, which occurs when the gate driver drives the gate lines, can be prevented.  
         [0042]     According to the invention, the tuning DC power outputted by the DC power supply is fed to the gate driver as the gate-on DC power. Additionally, the voltage corresponding to the tuning DC power is set to be within a range of volts allowed by both the receiving portion and the gate driver. Further, the series regulator for removing noise components generated by driving the gate lines by the gate driver and for stabilizing the voltage applied to the gate driver is provided on at least one of the power path for feeding the tuning DC power to the gate driver, and the power path for feeding the tuning DC power from the DC power supply to the receiving portion. Therefore, the gate driver is operated by the tuning DC power supplied instead of the gate-on DC power. Further, the noise components, which are generated at the gate driver and would intrude into the receiving portion through the path for the tuning DC power, are removed by the series regulator, so that the noise components are not transmitted to the receiving portion. Moreover, the voltage applied from the DC power supply to the gate driver is stabilized. Thus, the charge pump is unnecessary. Consequently, increase in the number of parts can be prevented. Also, decrease in the receiver sensitivity due to the sneaking of noises, which occurs when the gate driver drives the gate lines, can be prevented.  
         [0043]     According to the invention, the tuning DC power outputted by the DC power supply is fed to the gate driver as the gate-on DC power. Moreover, the voltage corresponding to the tuning DC power is set to be within a range of volts allowed by both the receiving portion and the gate driver. Thus, the gate driver is operated by the tuning DC power supplied instead of the gate-on DC power. Consequently, increase in the number of components can be prevented, and the cost is reduced.