JP4403729B2 - Display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power recovery circuit used in a display device.
[0002]
[Prior art]
Driving circuit for driving common electrodes (also referred to as sustain electrodes), scan electrodes, and address electrodes (these electrodes are electrically regarded as capacitive loads) constituting an AC type plasma display panel (hereinafter abbreviated as PDP) The common electrode driving circuit, scan electrode driving circuit, address electrode driving circuit, and the like are generally provided with a power recovery circuit in order to effectively use the driving power. It is disclosed in FIG.
[0003]
In FIG. 5, the power recovery circuit provided in the drive circuit includes a recovery coil L, diodes D1 and D2 connected to the recovery coil L, and a switch S1 connected to the reverse side of the recovery coil L side of the diode D1. And a switch S2 connected to the opposite side of the recovery coil L side of the diode D2, and an intersection between the other terminal of the switch S1 and the other terminal of S2, and a ground (hereinafter abbreviated as GND). And the recovered capacitor Css.
[0004]
In the power recovery circuit provided in the drive circuit, the recovery coil L is used for charging and discharging the capacitor Cp indicating the panel capacitance, and most of the energy lost in the capacitor Cp due to resonance between the recovery coil L and the capacitor Cp. Is recovered in the recovery capacitor Css through the recovery coil L.
[0005]
The voltage Vss of the recovery capacitor Css is ½ of the power supply voltage Vcc, and the voltage Vp applied to the capacitor Cp is theoretically LC resonance as shown in FIG. Due to this, it periodically changes between the power supply voltage Vcc and the GND potential.
[0006]
However, in the section (1) in FIG. 6 of Patent Document 1 below, a loss occurs due to the resistance component in the power recovery circuit, particularly the resistance component of the recovery coil L, diode D1, and switch S1, and the voltage Vp rises to Vcc. Instead, a jump (rising edge) occurs at the boundary between the sections (1) and (2). For the same reason, a jump (falling edge) occurs at the boundary between the sections {circle around (3)} and {circle around (4)} without being fully lowered to the GND potential in the section {circle around (3)}. Along with this, it is pointed out in paragraph No. [0009] to paragraph No. [0011] of Patent Document 2 below that current including harmonics flows in the capacitor Cp and radiates unnecessary electromagnetic waves.
[0007]
Therefore, in Patent Document 2 below, as disclosed in FIGS. 3, 5, 7, etc., in order to eliminate the above-described jump (edge), the power recovery circuit corrects the loss caused by the resistance component. The voltage of the recovery capacitor is held at a potential lower than the voltage clamp unit CL1 or 1/2 Vsus which holds the voltage of the recovery capacitor at a potential higher than 1/2 Vsus (Vsus is a power supply voltage corresponding to the power supply voltage Vcc of Patent Document 1 below). The power recovery circuit includes the voltage clamp part CL2 or both voltage clamp parts CL1 and CL2.
[0008]
Thus, in the following Patent Document 2, the above-described jump (edge) is eliminated, and unnecessary electromagnetic radiation is reduced.
[0009]
[Patent Document 1]
Japanese Patent Publication No. 7-109542 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-27888
[Problems to be solved by the invention]
In the above-mentioned Patent Document 2, as described above, the voltage recovery unit that corrects the loss due to the resistance component is provided in the power recovery circuit to eliminate the above-described jump (edge) and reduce unnecessary electromagnetic radiation.
[0011]
However, for this purpose, a power supply having a voltage V3 (70 to 90V) lower by several tens of V (volt) than ½ Vsus or a power supply having V2 (110 to 130V) higher by several tens of V than ½ Vsus is required. Thus, there are problems such as an increase in the scale of the power supply circuit and an increase in cost.
[0012]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a power recovery circuit for a plasma display panel that can reduce an increase in scale and cost of a power supply circuit.
[0013]
[Means for Solving the Problems]
The present invention relates to an electrode pair in which discharge is performed by applying an alternating sustaining voltage, an inductor having one end connected to at least one electrode of the electrode pair, and a capacitor having one end connected to the other end of the inductor, A first switch unit connected in parallel to the other end of the capacitor, a second switch unit, and a negative power source connected to a side of the first switch unit different from the side to which the capacitor is connected A positive power supply voltage unit connected to a side different from a side to which the capacitor of the second switch unit is connected, and in the charge recovery period from the electrode, the first switch Is turned on to apply a negative voltage from the negative power supply voltage unit to the other end of the capacitor, and during the charge discharge period to the electrode, the second switch is turned on and the other end of the capacitor is turned on to the positive power supply voltage. A positive voltage is applied by the parts, the absolute value of the negative power supply voltage section and the positive power supply voltage section is the voltage supplied has a structure that 5-15% of the absolute value of the alternating of sustain voltage.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments relating to a power recovery circuit used in a common electrode driving circuit, a scan electrode driving circuit, an address electrode driving circuit, and the like, which are driving circuits for driving an AC plasma display panel, will be described in detail with reference to the drawings. In all the drawings, parts having common functions are denoted by the same reference numerals, and once described, repeated description is omitted to avoid complexity.
[0015]
FIG. 1 is a diagram showing a common electrode driving circuit according to a first embodiment of the present invention, and FIG. 4 is a timing diagram for explaining the operation of the common electrode driving circuit of FIG.
[0016]
First, the configuration of the common electrode driving circuit will be described with reference to FIG. In FIG. 1, a capacitor 9 indicates a panel cell capacitance which is a capacitance between the common electrode and GND, and a common electrode is indicated by a symbol b. A power recovery circuit 100 is connected to the common electrode b, and a switch 7 and a switch 8 are connected between a power supply having a voltage Vs (hereinafter referred to as a power supply Vs) and GND.
[0017]
The power recovery circuit 100 includes a recovery coil (inductance) 1 connected to the common electrode b, a recovery capacitor 2 connected in series to the recovery coil, switches 3 and 5 connected to the recovery capacitor 2, A diode 4 which is a one-way conducting element connected to the other terminal side, a power supply (hereinafter referred to as a power supply V2) having a voltage V2 which is a + power supply connected to the other terminal of the diode 4, A diode 6 which is a unidirectional conducting element having a characteristic opposite to that of the diode 4 connected to the other terminal side, and a power supply (hereinafter referred to as a power supply) connected to the other terminal of the diode 6 and having a voltage −V1 which is a power supply V1).
[0018]
Here, when the switches 3 and 5 of the recovery capacitor 2 are grounded (connected to GND), the configuration of the common electrode drive circuit is the same as that of FIG. At this time, if there is no loss due to the resistance component of the power recovery circuit, the voltage of the common electrode b of the capacitor 9 (hereinafter referred to as b voltage) is the power supply due to LC resonance between the recovery coil 1 and the capacitor 9 during charging and discharging. It rises to Vs and then falls to GND, but if there is a loss, it will not reach that point as described in the section of the prior art, and a leap will occur. Therefore, at least a positive voltage or negative voltage power supply having a voltage value corresponding to about ½ of the jump value ΔV due to loss (when converted to the recovery capacitor side, it becomes about ½ of ΔV due to LC resonance action). (Power supply V2 or power supply-V1) is connected in series to the recovery capacitor 2 in accordance with the charging period or discharging period of the capacitor 9 (that is, in accordance with the discharge or recovery of power of the recovery capacitor), and the power supply voltage is superimposed. The feature of the present invention resides in that no leap occurs.
[0019]
Needless to say, if the leap value at the time of charging and discharging differs depending on the polarity or the like, the voltage value (absolute value) of the power supply superimposed on the recovery capacitor 2 is changed.
[0020]
Next, the operation of the common electrode driving circuit will be described with reference to FIG. In FIG. 4, first, in the section T1, the switch 8 is first opened, the switch 3 is closed, and the switches 5 and 7 are continuously opened. At this time, a voltage of about ½ Vs is held in the recovery capacitor 2. Therefore, a voltage of (1/2 Vs + V2) is applied to the series LC resonance circuit of the recovery coil 1 and the capacitor 9. Note that the fact that the voltage of about 1/2 Vs is held in the recovery capacitor 2 is described in detail from page 10 right column 40th line to page 11 left column 5th line of Patent Document 1.
[0021]
FIG. 5 shows an equivalent circuit when the capacitor 9 is charged. In FIG. 5, 101 indicates an equivalent loss resistance of the power recovery circuit corresponding to the jump value ΔV, and VL indicates the output voltage of the recovery coil 1.
[0022]
Since the voltage drop loss due to the resistance component of the power recovery circuit (equal to the jump value ΔV described above) is corrected by the superimposed voltage V2 (= approximately ΔV / 2), at the end of the charging period of the section T1, the LC resonance Due to the action, VL becomes as shown in Equation 1.
VL = (1 / 2Vs + V2) × 2 = Vs + 2V2 = Vs + ΔV (Equation 1)
Therefore, the voltage b, that is, the voltage Vb applied to the capacitor 9 rises to almost the power source Vs.
[0023]
In the section T2, the switch 3 is opened, the switch 7 is closed, and the b voltage is pulled up to the power source Vs. However, since the b voltage does not jump at the boundary between the sections T1 and T2, unnecessary electromagnetic radiation is not generated.
[0024]
In the section T3, the switch 7 is opened, the switch 5 is closed, and the capacitor 9 starts discharging along the route of the recovery coil 1, the recovery capacitor 2, the switch 5, the diode 6, and the power source -V1. At this time, since the power supply -V1 is connected to the recovery capacitor 2, the loss of the voltage drop due to the resistance component of the power recovery circuit is corrected by the superimposed voltage -V1 as in the case of charging, and the discharge period of the section T3 is corrected. Finally, the b voltage falls almost to the electric GND potential. At this time, since there is no jump between the GND potential and unnecessary electromagnetic wave radiation does not occur. The recovery capacitor 2 is charged to about ½ Vs, which is ½ of the power source Vs, by transferring power (energy) to and from the capacitor 9 via the recovery coil 1, and the energy stored in the capacitor 9 is stored. Most of the energy is recovered by the recovery capacitor 2.
[0025]
In the section T4, the switch 5 is opened, the switch 8 is closed, the other switches remain open, the common electrode is grounded and fixed at the ground potential, and the charge of the capacitor 9 is discharged. Since the b voltage does not jump at the boundary between the sections T3 and T4, unnecessary electromagnetic radiation does not occur.
[0026]
The section from T1 to T3 described above is the driving section of the common electrode b. A period T4 following this period is a scanning electrode driving period (not shown). A power recovery circuit (not shown) having the same configuration is also connected to the scan electrode (not shown). During this period, the scan electrode is charged and discharged by a capacitor (not shown) formed between the scan electrode and GND. Needless to say, no jump occurs in the voltage (not shown; hereinafter referred to as the “d voltage”). The operation of the scanning electrode (not shown) during the driving period is the same as the operation of the common electrode b, and the description thereof is omitted.
[0027]
When the section T4 ends, the operation between the sections T1 to T3 is repeated again. In this way, an alternating sustaining voltage is applied between the common electrode and the scanning electrode (not shown), and the discharge is continuously maintained. At this time, it is possible to apply a periodic common electrode drive pulse without a jump at the rise or fall to the common electrode, discharge the power accumulated in the recovery capacitor 2 in the section T1, and recover the power in the section T3. it can. That is, electric power can be recovered while suppressing unnecessary electromagnetic radiation.
[0028]
When the power supply Vs is about 200 V, as described in the above-mentioned Patent Document 2, the clamp voltage Vb in FIG. 3 is 110 to 130 V, and the clamp voltage Va in FIG. The voltage to be corrected (corresponding to the above-described jump value ΔV) is about 10 to 30 V, and the absolute values of the power source V2 and the power source −V1 of the power recovery circuit of the present embodiment are about 10 to 30 V.
[0029]
Therefore, it is possible to use the low power supply voltage used in the PDP circuit for the power supply V2 and the power supply -V1, and it is possible to suppress an increase in cost compared to the conventional case. In addition, even if there is no power supply having a desired voltage value in the PDP circuit, the leap value can be reduced by using a low-voltage power supply that is close to the desired voltage value, so that unnecessary electromagnetic radiation is suppressed and the cost is increased. Can be suppressed.
[0030]
Further, even when a power supply having a desired voltage value is not in the PDP circuit and is newly provided, a conventional high voltage power supply of about 100 V is not used, so that power consumption and withstand voltage of the power supply can be reduced, and the power supply circuit Increase in scale and cost can be suppressed.
[0031]
FIG. 2 is a diagram showing a power recovery circuit 200 used in the common electrode driving circuit according to the second embodiment. In FIG. 2, the power source V2 is changed to the power source V2 ′ in FIG. 1, and the cathode side of the diode 6 is connected to the GND instead of the power source −V1. Therefore, in the present embodiment, since there is no power supply -V1 to be superimposed and superimposed, unlike FIG. 1, a leap occurs at the boundary between the section T3 and the section T4 in FIG.
[0032]
FIG. 6 is a timing chart for explaining the operation of the common electrode driving circuit of FIG. 2 during the discharge sustain period. In FIG. 6, first, in the section T1, the switch 8 is first opened, the switch 3 is closed, and the switches 5 and 7 are continuously opened. At this time, the recovery capacitor holds approximately (1 / 2Vs−1 / 2ΔV), which is a voltage somewhat lower than the voltage of 1 / 2Vs (details will be described later). Accordingly, a voltage of (1 / 2Vs−1 / 2ΔV + V2 ′) is applied to the series LC resonance circuit of the recovery coil 1 and the capacitor 9.
[0033]
Here, the power source V2 ′ is a superimposed power source that corrects the loss ΔV due to the resistance component of the power recovery circuit 200. In this embodiment, V2 ′ = 1 / 2ΔV + 1 / 2ΔV (Equation 2)
In addition to the voltage ½ΔV for correcting the loss ΔV due to the resistance component, the amount by which the voltage of the recovery capacitor 2 is lower than ½Vs (approximately equal to ½ΔV) is also corrected. Therefore, since (1 / 2Vs + 1 / 2ΔV) is applied to the series LC resonance circuit, at the end of the charging period of the section T1, the b voltage, that is, the voltage Vb applied to the capacitor 9 rises to almost the power supply Vs by the LC resonance action. .
[0034]
In the section T2, the switch 3 is opened, the switch 7 is closed, and the b voltage is pulled up to the power source Vs. However, since the b voltage does not jump at the boundary between the sections T1 and T2, unnecessary electromagnetic radiation is not generated.
[0035]
In the section T3, the switch 7 is opened, the switch 5 is closed, and the capacitor 9 starts discharging along the route of the recovery coil 1, the recovery capacitor 2, the switch 5, the diode 6, and the GND. However, unlike the case of FIG. 4, since the loss due to the resistance component of the power recovery circuit 200 is not corrected during discharge, the b voltage does not fall to the GND potential at the end of the discharge period of the section T3. Further, most of the energy stored in the capacitor 9 is recovered in the recovery capacitor 2, but the voltage is slightly lower than 1 / 2Vs due to the loss ΔV due to the resistance component in the power recovery circuit (Vs−ΔV). ) / 2 only charged.
[0036]
In the section T4, the switch 5 is opened, the switch 8 is closed, the other switches remain open, the common electrode is grounded and fixed at the ground potential, and the charge of the capacitor 9 is discharged. Since the jump ΔV occurs in the b voltage at the boundary between the sections T3 and T4, unnecessary electromagnetic radiation is generated. However, since there is no jump at the boundary between the section T1 and the section T2, unnecessary electromagnetic radiation is reduced as a whole.
[0037]
As described above, in the present embodiment, unlike FIG. 1, a jump occurs when the capacitor 9 is discharged, but since there is no jump when charging, it has an effect of suppressing unnecessary electromagnetic radiation somewhat. Further, since the superimposed power supply V2 ′ may be a low voltage power supply as in the first embodiment, an increase in cost can be suppressed.
[0038]
FIG. 3 is a diagram showing a power recovery circuit 300 used in the common electrode driving circuit according to the third embodiment. FIG. 3 shows that the anode side of the diode 4 in FIG. 1 is connected to GND instead of the power source V2. Accordingly, in the present embodiment, since there is no power supply V2 to be superimposed and superimposed, unlike FIG. 1, a jump occurs at the boundary between the section T1 and the section T2 in FIG. 4, but there is a superimposed power supply −V1 at the boundary between the section T3 and the section T4. Therefore, no leap occurs, and unnecessary electromagnetic radiation is reduced as a whole. Note that the voltage across the recovery capacitor 2 at the time of power recovery at the recovery capacitor 2 is approximately ½ Vs. Other operations are the same as those in FIG. 1, and detailed description thereof is omitted.
[0039]
As described above, in the present embodiment, unlike FIG. 1, a jump occurs when the capacitor 9 is charged. However, since there is no jump when discharging, there is an effect of suppressing unnecessary electromagnetic radiation somewhat. Further, since the superimposed power source -V1 is the same as that of the first embodiment and may be a low voltage power source, an increase in cost can be suppressed.
[0040]
As described above, according to the present invention, the loss due to the resistance component at the time of power discharge or power recovery of the recovery capacitor in the power recovery circuit that occurs during the common electrode drive, the scan electrode drive, and the address electrode drive is caused to the recovery capacitor. In accordance with the power release or power recovery of the recovery capacitor, at least a positive voltage or negative voltage power supply having a voltage for correcting the loss is connected in series and superimposed, and correction is performed, so that unnecessary electromagnetic radiation can be suppressed. In addition, since the power supply can be set to a low voltage, it is possible to provide a power recovery circuit for a plasma display panel that can reduce an increase in scale and cost of a power supply circuit.
[0041]
【The invention's effect】
According to the present invention, a highly reliable display device can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a common electrode driving circuit according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a power recovery circuit used in a common electrode drive circuit according to a second embodiment.
FIG. 3 is a diagram showing a power recovery circuit used in a common electrode drive circuit according to a third embodiment.
4 is a timing chart for explaining the operation in the discharge sustain period of the common electrode driving circuit of FIG. 1; FIG.
FIG. 5 is an equivalent circuit when the capacitor 9 is charged.
6 is a timing chart for explaining the operation in the discharge sustain period of the common electrode driving circuit of FIG. 2;
[Explanation of symbols]
1 ... recovery coil, 2 ... recovery capacitor, 3 ... switch, 4 ... diode,
5 ... switch, 6 ... diode, 7 ... switch, 8 ... switch,
9: Capacitor,
100, 200, 300 ... power recovery circuit, 101 ... loss resistance

Claims (1)

An electrode pair to which an alternating sustaining voltage is applied and discharge is performed;
An inductor having one end connected to at least one electrode of the electrode pair ;
A capacitor having one end connected to the other end of the inductor ;
A first switch unit and a second switch unit connected in parallel to the other end of the capacitor;
A negative power supply voltage unit connected to a side different from the side to which the capacitor of the first switch unit is connected;
A positive power supply voltage unit connected to a side different from the side to which the capacitor of the second switch unit is connected,
In the charge recovery period from the electrode,
Turn on the first switch and apply a negative voltage by the negative power supply voltage unit to the other end of the capacitor,
In the charge discharge period to the electrode,
Turn on the second switch and apply a positive voltage from the positive power supply voltage unit to the other end of the capacitor;
The absolute value of the voltage which the said negative power supply voltage part and the said positive power supply voltage part supply is 5 to 15% of the absolute value of the said alternating maintenance voltage, The display apparatus characterized by the above-mentioned.

Images