JP4628652B2 - Plasma display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma display device used for image display of a television receiver and a computer terminal.
[0002]
[Prior art]
In general, a plasma display apparatus using a plasma display panel as a display device is configured as shown in FIG. That is, the plasma display panel 1 has a structure in which a discharge space is formed by overlapping two glass plates, and a plurality of discharge cells are provided by forming a plurality of scan electrode groups, sustain electrode groups, and write electrode groups. It is. A writing circuit 2 is connected to the writing electrode group of the plasma display panel 1 and a scanning circuit 3 is connected to the scanning electrode group, and discharge is performed by a selection pulse from the writing circuit 2 and the scanning circuit 3. An address operation is performed on the discharge cell. Further, a sustain circuit 4 is connected to the scan electrode group of the plasma display panel 1 through the scan circuit 3, and a sustain circuit 5 is connected to the sustain electrode group, and outputs are alternately output from the sustain circuit 4 and the sustain circuit 5. The display is driven by performing a sustain discharge operation in the discharge cell in which writing is performed with the sustain pulse. The sustain circuits 4 and 5 include a switch element for supplying a sustain discharge current, a switch element for supplying a sustain pulse switching current, a capacitor, and an inductance. A semiconductor element such as a MOSFET is used as the switch element. It is done.
[0003]
In such a plasma display device, by controlling the number of sustain pulses in accordance with the state of image display, that is, the lighting rate of display, it is possible to obtain a good image quality and to control power consumption as much as possible. Is called. In other words, for images with a small display area, the number of sustain pulses is increased so that a bright image can be obtained. For images with a large display area, the number of sustain pulses is decreased so that the power consumption of the plasma display panel does not become excessive. It controls (refer patent document 1).
[0004]
[Patent Document 1]
JP 2000-338933 A
[Problems to be solved by the invention]
However, in such a conventional plasma display device, since the number of sustain pulses is large and the sustain discharge current is small when the lighting rate is low, the power loss of the switch element that supplies the switching current of the sustain pulse is increased, and the sustain discharge current is increased. The power loss of the switch element that supplies is reduced. When the lighting rate is high, the number of sustain pulses is small and the discharge current is large. On the contrary, the power loss of the switch element that supplies the sustain pulse switching current is small, and the power loss of the switch element that supplies the sustain discharge current is small. growing.
[0006]
In addition, since semiconductor devices such as MOSFETs used for the switch elements perform a switching operation by passing a sustain discharge current or a sustain pulse switching current, power loss due to switch on-resistance or switching occurs. It is necessary to determine the size of the heat sink according to the maximum power loss of each switch element, but when the number of sustain pulses is controlled according to the lighting rate, as described above Since the maximum power loss in each switch element increases, the size of the heat sink increases, and as a result, the size of the substrate of the sustain circuit on which the switch element and the heat sink are mounted increases.
[0007]
The present invention has been made to solve such a problem, and an object thereof is to obtain a plasma display device capable of reducing the substrate size of the sustain circuit.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a plasma display apparatus according to the present invention includes a plasma display panel having a scan electrode, a sustain electrode, and a write electrode, and a sustain pulse voltage applied to the scan electrode and the sustain electrode during the sustain discharge operation of the plasma display panel. And a sustain circuit configured to increase the number of sustain pulses in an image with a low lighting rate and reduce the number of sustain pulses in an image with a high lighting rate, and the sustain circuit is provided in the plasma display panel. First and second power loss decreases when the power supply voltage is supplied in series so as to supply a sustain pulse voltage and the lighting rate is small, and the power loss increases when the lighting rate increases. One end of the switch element and a connection point between the first switch element and the second switch element. When an inductance that forms an LC resonance circuit with a laser display panel is inserted and connected between this inductance and a capacitor for a recovery circuit and the lighting rate is small, the power loss increases and the power loss increases when the lighting rate increases. A third switch element that is lowered, and the first, second, and third switch elements are attached to a common heat sink, and the first, second, and third switch elements and the heat sink are printed The heat sink is attached to a wiring board, and the size of the heat sink is smaller than the total size of the heat sink according to the individual maximum power loss of the first, second and third switch elements . With this configuration, it is possible to reduce the size of the heat sink as the entire switch element, and to reduce the size of the substrate.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plasma display device according to an embodiment of the present invention will be described with reference to FIGS.
[0010]
FIG. 1 shows an overall configuration of a plasma display device according to an embodiment of the present invention. In the figure, reference numeral 11 denotes a plasma display panel. The plasma display panel 11 discharges by overlapping two glass plates. In addition to forming a space, a plurality of discharge cells are provided by forming a plurality of scan electrode groups, sustain electrode groups, and write electrode groups. A writing circuit 12 is connected to the writing electrode of the plasma display panel 11 and a scanning circuit 13 is connected to the scanning electrode, and writing operation is performed on a discharge cell that discharges with a selection pulse from the writing circuit 12 and the scanning circuit 13. I do. A sustain circuit 14 is connected to the scan electrode group of the plasma display panel 11 via the scan circuit 13, and a sustain circuit 15 is connected to the sustain electrode group. The sustain circuit 14 and the sustain circuit 15 alternately output the sustain circuit 14. The display is driven by performing a sustain discharge operation in the discharge cell in which writing is performed with the sustain pulse.
[0011]
The sustain circuit 14 includes switch elements 141 and 142 made of semiconductor elements such as MOSFETs and IGBTs as first and second switch elements inserted and connected in series to a circuit to which a power supply voltage of Vsus is supplied, and the switch elements One end is connected to a connection point between the switch element 142 and the switch element 142, and an inductance 143 that forms an LC resonance circuit with the scan electrode capacitance of the plasma display panel 11 is inserted between the inductance 143 and the capacitor 144 for the recovery circuit. And a switch element 145 made of a semiconductor element such as a MOSFET or IGBT as a connected third switch element.
[0012]
Similarly to the sustain circuit 14, the sustain circuit 15 includes semiconductor elements such as MOSFETs and IGBTs as first and second switch elements inserted and connected in series to a circuit to which a power supply voltage of Vsus is supplied. An inductance 153 that forms an LC resonance circuit with the switch elements 151 and 152, one end connected to the connection point of the switch element 151 and the switch element 152, and the sustain electrode capacitance of the plasma display panel 11, and the recovery of the inductance 153 A switch element 155 made of a semiconductor element such as a MOSFET or IGBT is provided as a third switch element inserted and connected between the circuit capacitor 154.
[0013]
In the sustain circuits 14 and 15, the switch elements 141, 142, and 145 and the switch elements 151, 152, and 155 used in the respective circuits are a common heat radiating plate as shown by dotted line regions A and B in FIG. It is attached to. FIG. 2 shows the configuration of that portion.
[0014]
FIG. 2 shows a mounting structure of the switch elements 141, 142, and 145 on the sustain circuit 14 side. Since the mounting structure of the switching elements 151,152,155 of the sustain circuit 15 side, the same configuration as FIG. 1, is omitted.
[0015]
As shown in FIG. 2, switch elements 141, 142, and 145 made of semiconductor elements such as MOSFETs and IGBTs are mounted on the printed wiring board 16 that constitutes the sustain circuit 14, and the switch elements 141, 142, and 145 are The heat radiation fins 17a are attached to a flat surface 17b of a common heat radiation plate 17 made of aluminum in close contact with an adhesive or a screw. The heat radiating plate 17 has a mounting leg 17 c that is inserted into a mounting hole 16 a provided in the printed wiring board 16 and is attached to the printed wiring board 16 together with the switch elements 141, 142, and 145.
[0016]
Next, the operation of the sustain circuit 14 of the plasma display device having the above configuration will be described in detail.
[0017]
The sustain circuit 14 outputs a sustain pulse voltage 50 as shown in FIG. First, the switch element 145 is turned on at the start point of t1, and the sustain pulse is applied to the plasma display panel 11 from the voltage ½ Vsus (V) of the capacitor 144 via the switch element 145, the inductance 143, and the scanning circuit 13 in the period t1. A switching current 52 having a voltage 50 flows, and the output voltage of the sustain circuit 14 is switched from 0 (V) to Vsus (V) using LC resonance between the inductance 143 and the scan electrode capacitance of the plasma display panel 11.
[0018]
At the start point of the subsequent t2 period, the switch element 145 is turned off and the switch element 141 is turned on, and the scanning circuit 13 according to the number of discharge cells in which the write operation is performed from the Vsus power source through the switch element 141 in the t2 period. A sustain discharge current 54 flows through the plasma display panel 11 via the.
[0019]
At the starting point of the subsequent t3 period, the switch element 141 is turned off and the switch element 145 is turned on. During the t3 period, the voltage from the voltage ½ Vsus (V) of the capacitor 144 passes through the switch element 145, the inductance 143, and the scanning circuit 13. A switching current 53 having a sustain pulse voltage 50 flows through the display panel 11, and the output voltage of the sustain circuit 14 is changed from Vsus (V) to 0 (V) using LC resonance between the inductance 143 and the electrode capacitance of the plasma display panel 11. Switched to
[0020]
At the starting point of the subsequent t4 period, the switch element 145 is turned off and the switch element 142 is turned on. In the subsequent t4, t5, and t6 periods, the switching current 55 by the sustain pulse voltage 51 from the sustain circuit 15 is written. The sustain discharge current 56 and the switching current 57 flow through the switch element 142 according to the number of discharge cells.
[0021]
As shown in FIG. 3, sustain circuit 15 performs the same operation as sustain circuit 14 except that the phase of the sustain pulse is shifted by 180 degrees.
[0022]
In the plasma display device according to the present embodiment, as shown in FIG. 4, the number of sustain pulses is controlled according to the state of image display, that is, the lighting rate of image display. That is, control is performed so that a bright image can be obtained by increasing the number of sustain pulses for an image with a small display area (small lighting rate), and a number of sustain pulses for an image with a large display area (large lighting rate). Control is performed so that the power consumption of the plasma display panel does not become excessive. By controlling the number of sustain pulses in accordance with the display lighting rate in this way, good image quality and reduction in power consumption are achieved.
[0023]
As described above, in the plasma display device according to the present embodiment, the switch elements 141, 142, and 145 constituting the sustain circuit 14 are attached to the common single heat sink 17, and the switch elements 141, 142, and 145 are mounted. And the heat sink 17 are attached to the printed wiring board 16, and the switch elements 151, 152, and 155 constituting the sustain circuit 15 are attached to the common single heat sink 17, and the switch elements 151, 152, and 155 and the heat sink 17 is attached to the printed wiring board 16, thereby reducing the size of the heat sink and reducing the size of the printed wiring board constituting the circuit as compared with the case where the heat sink is individually attached to each switch element. can do.
[0024]
Here, this will be further described. FIG. 5 is a graph showing an example of the relationship between the lighting rate of image display and the power loss of the switch elements 141, 142, and 145. In the plasma display device, the display lighting rate is changed by changing the display area while keeping the luminance level of the image input signal constant. As shown in FIG. 5, the power loss of the switch element 145 is dominant when the number of sustain pulses is dominant, and is large when the lighting rate is small, but decreases as the lighting rate increases. On the other hand, the total power loss of the switch elements 141 and 142 is dominated by the increase in the sustain discharge current peak due to the increase in the lighting rate, and is small when the lighting rate is small, but gradually increases as the lighting rate increases. Yes.
[0025]
Thus, as the lighting rate increases, the power loss of the switch element 145 decreases, and the total power loss of the switch elements 141 and 142 increases. When the switches 141, 142, and 145 are attached to different heat sinks, the size of the heat sink must be determined according to the respective maximum power loss (Pmax1 and Pmax2 in FIG. 5). By attaching the elements 141, 142, 145 to one heat sink 17, the size of the heat sink 17 is determined in accordance with the maximum total power loss of the switch elements 141, 142, 145 (Pmax 3 in FIG. 5). Can do. As shown in FIG. 5, it is possible to reduce the size of the heat sink by about 15% compared to the total size of the heat sink when the heat sink is individually attached according to each maximum power loss, and the substrate size of the sustain circuit 14 can be reduced accordingly. So the cost can be reduced. Although explanation is omitted, the same operation and effect can be obtained for the sustain circuit 15.
[0026]
In the above description, a case where a MOSFET semiconductor element having a normal exterior is used as a switching element has been described as an example. However, when a bare chip semiconductor element is used, a single switching element composed of a bare chip semiconductor element is used. And mounting a single heat sink on the substrate. In the above example, the switch element is shown as a single switch. However, in the case where the switch element is actually composed of a semiconductor element, the switch elements 145 and 155 are switch elements that control bidirectional current. What is necessary is just to comprise combining several semiconductor elements, such as MOSFET.
[0027]
【The invention's effect】
As described above, according to the plasma display device of the present invention, the size of the heat dissipation plate of the sustain circuit can be reduced, the size of the substrate can be reduced correspondingly, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a plasma display device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the main structure of the device. FIG. 3 is a drive waveform diagram of the device. Fig. 5 is a characteristic diagram showing the relationship between the lighting rate of the device and the number of sustain pulses. Fig. 5 is a characteristic diagram showing the relationship between the lighting rate of the device and the power loss of the switch element. Fig. 6 is a block diagram showing a conventional plasma display device. Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Plasma display panel 12 Writing circuit 13 Scanning circuit 14, 15 Maintenance circuit 17 Heat sink 141, 142, 145, 151, 152, 155 Switch element

Claims (1)

A plasma display panel having a scan electrode, a sustain electrode and a write electrode, and a sustain pulse voltage is supplied to the scan electrode and the sustain electrode during the sustain discharge operation of the plasma display panel, and the number of sustain pulses is increased in an image with a low lighting rate. A sustain circuit configured to reduce the number of sustain pulses in an image with a high lighting rate, and the sustain circuit is a circuit to which a power supply voltage is supplied so as to supply a sustain pulse voltage to the plasma display panel. Connection between the first and second switch elements, which are inserted and connected in series and the power loss is reduced when the lighting rate is small and the power loss is increased when the lighting rate is large, and the first and second switch elements An inductor having one end connected to a point and forming an LC resonance circuit with the plasma display panel And a third switching element that is inserted and connected between the inductance and the capacitor for the recovery circuit and has a power loss that increases when the lighting rate is small and decreases when the lighting rate increases. The first, second, and third switch elements are attached to a common heat sink, and the first, second, and third switch elements and the heat sink are attached to a printed wiring board. The size of the heat sink is A plasma display apparatus, wherein the total size of the heat radiating plate is adjusted to the maximum power loss of each of the first, second and third switching elements .

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