JP2005338582A - Capacitive load driving devicea and plasma display mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device for a capacitive load that increases the maximum number of pulses applied to the capacitive load within a fixed period by suppressing reactive power due to charging and discharging of the capacitive load with a less number of components than a conventional driving device and further shortening the time needed for the charging and discharging. <P>SOLUTION: A sustain electrode drive section (2) includes a series connection (Q1 and Q2) of two switch elements between a power terminal (1T) and a ground terminal. The connection point (J1) of the series connection (Q1 and Q2) is connected to a sustain electrode (X) of a PDP (20). A scanning electrode drive section (3) includes another series connection (Q3 and Q4) of two switch elements between the power terminal (1T) and the ground terminal. The connection point (J2) of the series connection (Q3 and Q4) is connected to a scanning electrode (Y) of the PDP (20). An inductor (L) is connected between the two connection points (J1 and J2) in parallel to a panel capacitor (Cp) of the PDP (20) to sustain power feeding throughout a discharge sustain period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive device for a capacitive load such as a plasma display panel (PDP).

  A plasma display is a display device that utilizes a light emission phenomenon associated with gas discharge. A plasma display panel (PDP) is more advantageous than other display devices in terms of a large screen, a thin profile, and a wide viewing angle. PDPs are roughly classified into a DC type that operates with a DC pulse and an AC type that operates with an AC pulse. The AC type PDP has a particularly high luminance and a simple structure. Therefore, the AC type PDP is suitable for mass production and pixel definition and is widely used.

  FIG. 4 is a block diagram showing the configuration of a conventional plasma display (see, for example, Patent Documents 1 and 2). The conventional plasma display includes a PDP 20, a power factor correction (PFC) converter 40, a PDP driving device 10, and a control unit 30.

The PDP 20 is, for example, an AC type and has a three-electrode surface discharge type structure (see, for example, Patent Documents 1 and 2). Address electrodes A1, A2, A3,... Are arranged on the back substrate of the PDP 20 in the vertical direction of the panel. On the front substrate of PDP 20, sustain electrodes X1, X2, X3,... And scan electrodes Y1, Y2, Y3,... Are alternately arranged in the horizontal direction of the panel. Since the sustain electrodes X1, X2, X3,... Are connected to each other, the potentials are substantially equal. The address electrodes A1, A2, A3,... And the scan electrodes Y1, Y2, Y3,.
Discharge cells are installed at a pair of sustain electrodes and scan electrodes adjacent to each other (for example, a pair of sustain electrode X2 and scan electrode Y2) and an intersection P (shaded portion shown in FIG. 4) of an address electrode (for example, A2). (See, for example, Patent Document 1). On the surface of the discharge cell, a layer made of a dielectric (dielectric layer), a layer for protecting the electrode and the dielectric layer (protective layer), and a layer containing a fluorescent substance (fluorescent layer) are provided. Gas is sealed inside the discharge cell. When a predetermined pulse voltage is applied between the sustain electrode, the scan electrode, and the address electrode, discharge occurs in the discharge cell. At that time, gas molecules in the discharge cell are ionized and emit ultraviolet rays. The ultraviolet rays excite the fluorescent material on the surface of the discharge cell to generate fluorescence. Thus, the discharge cell emits light.

The PFC converter 40 converts AC power from an external commercial AC power source AC into DC power. In particular, the PFC converter 40 keeps the power factor substantially equal to 1 for the input from the commercial AC power source AC.
The PDP driving device 10 includes a DC-DC converter 1, a sustain electrode driving unit 2, a scan electrode driving unit 3, and an address electrode driving unit 4.
The DC-DC converter 1 converts the output voltage of the PFC converter 40 into a predetermined DC voltage Vc and maintains the DC voltage Vc constant. The DC-DC converter 1 is generally an insulation type, and insulates between the high voltage section on the input side and the PDP 20 on the output side. Thereby, the PDP driving device 10 sufficiently secures safety.

Each of the sustain electrode drive unit 2, the scan electrode drive unit 3, and the address electrode drive unit 4 includes a switch element, and generates a pulse voltage by switching these switch elements.
The sustain electrode drive unit 2 is connected to the sustain electrodes X1, X2, X3,... Of the PDP 20, converts the output voltage of the DC-DC converter 1 into a predetermined pulse voltage, and the sustain electrodes X1, X2, X3,. Apply simultaneously.
The scan electrode driving unit 3 is connected to the scan electrodes Y1, Y2, Y3,... Of the PDP 20, converts the output voltage of the DC-DC converter 1 into a predetermined pulse voltage, and with respect to the scan electrodes Y1, Y2, Y3,. Apply individually.
The address electrode driver 4 is connected to the address electrodes A1, A2, A3,... Of the PDP 20, and applies a predetermined pulse voltage to them individually.

The control unit 30 controls switching of each of the sustain electrode driving unit 2, the scan electrode driving unit 3, and the address electrode driving unit 4. The switching control follows an ADS (Address Display-period Separation) system.
The ADS method is a kind of subfield method. In the subfield method, one field of an image is divided into a plurality of subfields. Each subfield includes an initialization period, an address period, and a discharge sustain period. Particularly in the ADS system, the above three periods are set in common for all the discharge cells of the PDP 20 (see, for example, Patent Document 1).

In the initialization period, an initialization pulse voltage is applied between the sustain electrodes X1, X2, X3,... Of the PDP 20 and the scan electrodes Y1, Y2, Y3,. Thereby, wall charges are made uniform in all the discharge cells.
In the address period, the scan pulse voltage is sequentially applied to the scan electrodes Y1, Y2, Y3,. At the same time, a signal pulse voltage is applied to some of the address electrodes A1, A2, A3,. Here, the address electrode to which the signal pulse voltage is to be applied is selected based on a video signal input from the outside. When a scan pulse voltage is applied to one of the scan electrodes Y2 and a signal pulse voltage is applied to one of the address electrodes A2, a discharge is performed at a discharge cell located at the intersection P between the scan electrode Y2 and the address electrode A2. Occurs. The discharge accumulates wall charges on the surface of the discharge cell P.
In the discharge sustain period, the discharge sustain pulse voltage is simultaneously and periodically applied between the sustain electrodes X1, X2, X3,... And the scan electrodes Y1, Y2, Y3,. At that time, in the discharge cell P in which the wall charges are accumulated during the address period, the gas discharge is maintained and light emission occurs. Since the length of the discharge sustaining period is different for each subfield, the light emission time per field of the discharge cell, that is, the luminance of the discharge cell is adjusted by selecting the subfield to emit light.
Based on the video signal, the control unit 30 determines an address electrode and a subfield to which the signal pulse voltage is applied. As a result, an image corresponding to the image signal is reproduced on the PDP 20.

  The light emission of each discharge cell of the PDP requires the accumulation of wall charges. That is, the PDP is a capacitive load. In the PDP, as in the above-described three-electrode surface discharge structure, a large number of electrodes run vertically and horizontally on the panel and are close to each other. Therefore, the PDP has a large stray capacitance. In particular, the stray capacitance (hereinafter referred to as panel capacitance) between the sustain electrode and the scan electrode is large. When a pulse voltage is applied between the sustain electrode and the scan electrode, the panel capacitance is charged / discharged. Due to the charging current and the discharging current, power is consumed by the respective resistances of the circuit elements of the PDP driving device, the sustain electrodes and the scanning electrodes of the PDP, and the lead wires. The power consumption is reactive power and does not contribute to the light emission of the discharge cell. The larger the size of the PDP, the larger the length and number of sustain electrodes and scan electrodes, and the larger the panel capacity. Therefore, the reduction of the reactive power is indispensable for achieving both a large screen and power saving of the PDP.

  A conventional PDP driving device has, for example, a power recovery unit, and thereby reduces the reactive power particularly in the discharge sustaining period (see, for example, Patent Documents 2 and 3). 5 and 6 are equivalent circuit diagrams of the sustain electrode driver 2, the scan electrode driver 3, and the PDP 20 in the discharge sustain period. In FIG. 5, sustain electrode drive unit 2 and scan electrode drive unit 3 have similar power recovery units 6A and 6B, respectively. In FIG. 6, the power recovery unit 6C is connected between the sustain electrode driving unit 2 and the scan electrode driving unit 3.

The switch elements Q1 and Q2 of the sustain electrode driving unit 2 and the switch elements Q3 and Q4 of the scan electrode driving unit 3 constitute, for example, a full bridge type discharge sustain pulse generating unit 5. The sustaining pulse generator 5 is connected to the sustain electrode X and the scan electrode Y of the PDP 20. Here, the equivalent circuit of the PDP 20 is represented only by the panel capacitance Cp, and the path of the current flowing through the PDP 20 when discharging in the discharge cells is omitted.
The control unit 30 (see FIG. 4) turns on and off the switch elements Q1 to Q4 of the sustaining pulse generating unit 5 at a predetermined timing. Thereby, an AC pulse voltage Vp having a constant period is applied to the panel capacitance Cp as a sustaining voltage pulse.

On the other hand, the control unit 30 turns on and off the switch elements of the power recovery units 6A and 6B or 6C during the rising / falling period of the sustaining voltage pulse Vp to resonate the inductor L and the panel capacitance Cp. The resonance inverts the voltage Vp across the panel capacitance Cp with almost no power consumption. That is, during the resonance period, the power consumed by the switching elements Q1 to Q4 of the sustaining pulse generating section 5, the sustaining electrode X and the scanning electrode Y of the PDP 20, and the resistances (not shown) of the lead wires are suppressed.
Thus, reactive power resulting from charging / discharging of the panel capacitance Cp is reduced.

JP 2004-13168 Japanese Examined Patent Publication No. 7-109542 Japanese Patent Laid-Open No. 11-344952

The PDP is desired to have a large screen, a thin shape, a light weight, and power saving. However, the enlargement of the screen is accompanied by an increase in reactive power due to charging / discharging of the panel capacity. Since the increase in reactive power leads to an increase in overall power consumption, power saving is prevented. The increase in reactive power further increases the current capacity of the circuit elements of the PDP driving device or increases the withstand voltage. As a result, since the size of the circuit element increases, the mounting area of the entire PDP driving device increases. Thus, the overall thickness and weight of the PDP is hindered.
In order to simultaneously achieve a large screen, thinning, lightening, and power saving of the PDP, it is desirable to configure a PDP driving device that can effectively suppress the above reactive power with a smaller number of components.
Therefore, it is desirable that the power recovery unit of the PDP drive device has a smaller number of parts.

In addition, higher image quality is desired for PDP. High image quality requires finer gradation of PDP. On the other hand, the display time per field is constant. For example, in Japanese television broadcasting, images are sent one field at a time in 1/60 second (= about 16.7 msec) intervals. Therefore, in the PDP, the light emission time of the discharge cell (especially the number of pulses of the sustaining pulse voltage) can be adjusted more precisely as the number of subfields per field is larger. That is, the gradation of the PDP can be refined.
In the conventional PDP driving apparatus, as described above, the power recovery unit turns on and off the switch element during the rising / falling period of the sustaining voltage pulse, and causes the inductor to resonate with the panel capacitance. Here, the resonance period is limited to the rising / falling period of the sustaining voltage pulse. However, since no current flows through the inductor at the start of the resonance, the rise / fall of the sustaining voltage pulse is relatively slow. As a result, since it is difficult to further shorten the discharge sustain period, it is difficult to further increase the number of subfields per field.

  As a capacitive load driving device, the present invention suppresses reactive power due to charging / discharging of the capacitive load with fewer parts than a conventional driving device, and further reduces the time required for charging / discharging, thereby An object of the present invention is to provide a driving device that increases the maximum number of pulses that can be applied to a capacitive load during a certain period.

A capacitive load driving device according to the present invention is a device for applying a predetermined pulse voltage to a capacitive load;
A pulse generator for converting a predetermined DC voltage into a pulse voltage by switching the switch element; and
An inductor connected in parallel with the capacitive load, to which the pulse voltage is applied and which is continuously energized;
Have

Here, the capacitive load is preferably a plasma display panel (PDP). In that case, the capacitive load driving device according to the present invention is:
A rectifying unit for converting an AC voltage from an external power source into a predetermined DC voltage;
A PDP driving device for converting the DC voltage into a predetermined pulse voltage; and
A PDP including a discharge cell that emits light by discharge of a gas enclosed therein, and a plurality of electrodes for applying a pulse voltage output by the PDP driving device to the discharge cell;
Is mounted as a PDP driving device.

  In the above capacitive load driving device according to the present invention, the inductor is connected in parallel with the capacitive load to which the pulse voltage is applied. The pulse voltage is applied to the capacitive load and the inductor. At that time, the inductor resonates with the capacitive load during the rising / falling period of the pulse voltage. The resonance reverses the polarity of the pulse voltage with little power consumption. That is, during the resonance period, the power consumed by the circuit elements of the pulse generation unit, the capacitive load, and the resistances of the lead wires is suppressed. Thus, reactive power due to charging / discharging of the capacitive load is reduced.

  Since the inductor is connected in parallel with the capacitive load, the resonance period with the capacitive load is limited to the rising period / falling period of the pulse voltage. Therefore, particularly when the capacitive load is a PDP, the above resonance does not adversely affect the image of the PDP. In addition, since the ringing associated with the resonance does not have to be taken into account when the PDP emits light, the withstand voltage of the circuit element of the capacitive load driving device may be low.

  In the capacitive load driving device according to the present invention, unlike the conventional driving device, the inductor continues to be energized. That is, the energization of the inductor is not cut off. As a result, the switch element for controlling the energization of the inductor may be removed, so that the capacitive load driving device according to the present invention has a small number of components and a small mounting area.

Furthermore, current has already flowed through the inductor at the start of resonance between the inductor and the capacitive load. Therefore, the rise / fall of the pulse voltage is fast. As a result, the maximum number of pulses that can be applied to the capacitive load in a certain period increases.
In particular, when the capacitive load is a PDP, the discharge sustain period is shortened by shortening the rise / fall periods of the sustain pulse voltage. Therefore, when the PDP display method is the subfield method, the number of subfields per field is easily increased.
Thus, the plasma display including the above-described capacitive load driving device according to the present invention can easily further refine the PDP gradation, that is, further improve the image quality.

In the capacitive load driving device according to the present invention, preferably, the pulse generator regenerates electric power from the inductor to the DC voltage supply source by switching of the switch element. Here, the DC voltage supply source corresponds to, for example, a rectifying unit in the plasma display described above.
For example, when the pulse generator includes a high-side switch element and a low-side switch element as switch elements, the switch elements are connected in series, and the connection point is connected to the capacitive load and the inductor, either The switch element may be turned on at the end of application of the pulse voltage, and a regenerative current may be passed from the inductor to the DC voltage supply source.
For example, when the application of a series of pulse voltages to the capacitive load ends, such as at the end of the discharge sustain period in the plasma display, resonance energy remains accumulated between the inductor and the capacitive load. In the above capacitive load driving device according to the present invention, the remaining resonance energy is regenerated to a DC voltage supply source. Accordingly, since the reactive power is further reduced, the efficiency is further improved in the above-described capacitive load driving device according to the present invention.

In the above capacitive load driving device according to the present invention, the inductor is connected in parallel with the capacitive load and resonates with the capacitive load. The resonance reduces reactive power resulting from charging and discharging of the capacitive load.
In the capacitive load driving device according to the present invention, unlike the conventional driving device, the inductor continues to be energized. As a result, the switch element for controlling the energization of the inductor may be removed, so that the capacitive load driving device according to the present invention has a small number of components and a small mounting area.

  Furthermore, when the inductor starts to resonate with the capacitive load, current is already flowing through the inductor. Therefore, the rise / fall of the pulse voltage is faster than those in the conventional driving device. As a result, the maximum number of pulses that can be applied to the capacitive load over a certain period of time is more easily increased than the maximum number of pulses in a conventional drive device. In particular, when the capacitive load is a PDP, the discharge sustain period is shortened by shortening the rising / falling period of the discharge sustain pulse voltage. Therefore, when the display method of the PDP is a subfield method, the number of subfields per field is easily increased, so that it is easy to further refine the gradation of the PDP, that is, further improve the image quality.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a plasma display according to the embodiment. The plasma display includes a PDP 20, a PFC converter 40, a PDP driving device 10, and a control unit 30.

The PDP 20 is preferably an AC type and has a three-electrode surface discharge type structure. Address electrodes A1, A2, A3,... Are arranged on the back substrate of the PDP 20 in the vertical direction of the panel. On the front substrate of PDP 20, sustain electrodes X1, X2, X3,... And scan electrodes Y1, Y2, Y3,... Are alternately arranged in the horizontal direction of the panel. Since the sustain electrodes X1, X2, X3,... Are connected to each other, the potentials are substantially equal. The address electrodes A1, A2, A3,... And the scan electrodes Y1, Y2, Y3,.
Discharge cells are installed at a pair of sustain electrodes and scan electrodes adjacent to each other (for example, a pair of sustain electrode X2 and scan electrode Y2) and an intersection P (shaded portion shown in FIG. 1) of an address electrode (for example, A2). The On the surface of the discharge cell, a layer made of a dielectric (dielectric layer), a layer for protecting the electrode and the dielectric layer (protective layer), and a layer containing a fluorescent substance (fluorescent layer) are provided. Gas is sealed inside the discharge cell. When a predetermined pulse voltage is applied between the sustain electrode, the scan electrode, and the address electrode, discharge occurs in the discharge cell. At that time, gas molecules in the discharge cell are ionized and emit ultraviolet rays. The ultraviolet rays excite the fluorescent material on the surface of the discharge cell to generate fluorescence. Thus, the discharge cell emits light.

The PFC converter 40 is connected to an external commercial AC power source AC. The PFC converter 40 receives AC power (general effective voltage 85 to 265 V) from the commercial AC power source AC, and converts the AC power into DC power (for example, an average voltage Vs of about 400 V). Further, the PFC converter 40 keeps the power factor substantially equal to 1 for the input from the commercial AC power supply AC by the switching operation.
The plasma display may include a full-wave rectification type AC-DC converter that does not improve the power factor, instead of the PFC converter 40. In addition, it is sufficient to have a full-wave rectifier circuit composed of a diode bridge and a capacitor.

The PDP driving device 10 includes a DC-DC converter 1, a sustain electrode driving unit 2, a scan electrode driving unit 3, an address electrode driving unit 4, and an inductor L.
The DC-DC converter 1 converts the output voltage of the PFC converter 40 into a predetermined DC voltage Vc and maintains the DC voltage Vc constant. The DC-DC converter 1 is generally an insulation type, and insulates between the high voltage section on the input side and the PDP 20 on the output side. Thereby, the PDP driving device 10 sufficiently secures safety.

Each of the sustain electrode drive unit 2, the scan electrode drive unit 3, and the address electrode drive unit 4 includes a switch element, and generates a pulse voltage by switching these switch elements.
The sustain electrode drive unit 2 is connected to the sustain electrodes X1, X2, X3,... Of the PDP 20, converts the output voltage of the DC-DC converter 1 into a predetermined pulse voltage, and the sustain electrodes X1, X2, X3,. Apply simultaneously.
The scan electrode driving unit 3 is connected to the scan electrodes Y1, Y2, Y3,... Of the PDP 20, converts the output voltage of the DC-DC converter 1 into a predetermined pulse voltage, and with respect to the scan electrodes Y1, Y2, Y3,. Apply individually.
The address electrode driver 4 is connected to the address electrodes A1, A2, A3,... Of the PDP 20, and applies a predetermined pulse voltage to them individually.

The control unit 30 controls switching of each of the sustain electrode driving unit 2, the scan electrode driving unit 3, and the address electrode driving unit 4. The switching control preferably follows an ADS (Address Display-period Separation) system.
The ADS system is a kind of subfield system, and one field of an image (for example, an interval of 1/60 seconds (= about 16.7 msec in Japanese television broadcasting)) is divided into a plurality of (for example, 8 to 12) subfields. Each subfield includes an initialization period, an address period, and a discharge sustain period. These periods are set in common for all the discharge cells of the PDP 20.

In the initialization period, an initialization pulse voltage is applied between the sustain electrodes X1, X2, X3,... Of the PDP 20 and the scan electrodes Y1, Y2, Y3,. Thereby, wall charges are made uniform in all the discharge cells.
In the address period, the scan pulse voltage is sequentially applied to the scan electrodes Y1, Y2, Y3,. At the same time, a signal pulse voltage is applied to some of the address electrodes A1, A2, A3,. Here, the address electrode to which the signal pulse voltage is to be applied is selected based on a video signal input from the outside. When a scan pulse voltage is applied to one of the scan electrodes Y2 and a signal pulse voltage is applied to one of the address electrodes A2, a discharge is performed at a discharge cell located at the intersection P between the scan electrode Y2 and the address electrode A2. Occurs. The discharge accumulates wall charges on the surface of the discharge cell P.
In the discharge sustain period, the discharge sustain pulse voltage is simultaneously and periodically applied between the sustain electrodes X1, X2, X3,... And the scan electrodes Y1, Y2, Y3,. At that time, in the discharge cell P in which the wall charges are accumulated during the address period, the gas discharge is maintained and light emission occurs. Since the length of the discharge sustaining period is different for each subfield, the light emission time per field of the discharge cell, that is, the luminance of the discharge cell is adjusted by selecting the subfield to emit light.
Based on the video signal, the control unit 30 determines an address electrode and a subfield to which the signal pulse voltage is applied. As a result, an image corresponding to the image signal is reproduced on the PDP 20.

  The inductor L is connected in parallel with the PDP 20 between the sustain electrode driver 2 and the scan electrode driver 3. That is, when a pulse voltage is applied to the sustain electrodes X1, X2, X3,... Or the scan electrodes Y1, Y2, Y3,..., The pulse voltage is also applied to the inductor L. As a result, the inductor L resonates with the stray capacitance between the sustain electrodes X1, X2, X3,... And the scan electrodes Y1, Y2, Y3,. The resonance inverts the voltage across the panel capacitance with almost no power consumption, reducing the reactive power due to the charging and discharging of the panel capacitance.

FIG. 2 is an equivalent circuit diagram of the sustain electrode driver 2, the scan electrode driver 3, and the PDP 20 in the discharge sustain period for the PDP driver 10 according to the embodiment of the present invention.
The sustain electrode driver 2 includes a series connection of a first high-side switch element Q1 and a first low-side switch element Q2 between a power supply terminal 1T and a ground terminal. A connection point J1 between the two switch elements Q1 and Q2 is connected to the sustain electrode X of the PDP 20.
Scan electrode driver 3 includes a series connection of second high-side switch element Q3 and second low-side switch element Q4 between power supply terminal 1T and the ground terminal. A connection point J2 between the two switch elements Q3 and Q4 is connected to the scan electrode Y of the PDP 20.
Here, the DC voltage Vs is applied from the PFC converter 40 to the power supply terminal 1T.
The equivalent circuit of the PDP 20 is represented only by the panel capacitance Cp connected between the sustain electrode X and the scan electrode Y, and the path of the current flowing through the PDP 20 when discharging in the discharge cell is omitted.
An inductor L is further connected in parallel with the panel capacitance Cp of the PDP 20 between the two connection points J1 and J2.

  The four switch elements Q1 to Q4 are preferably MOSFETs. In addition, an IGBT or a bipolar transistor may be used. These four switch elements Q1 to Q4 form a full-bridge inverter and function as the discharge sustain pulse generator 5. That is, the DC voltage Vs is converted into the discharge sustain pulse voltage Vp by turning on and off the four switch elements Q1 to Q4, and is applied between the sustain electrode X and the scan electrode Y of the PDP 20.

  The control unit 30 alternately and periodically turns on and off the pair of the first switch element Q1 and the fourth switch element Q4 and the pair of the second switch element Q2 and the third switch element Q3. . Thereby, an alternating voltage having a constant period, that is, a primary pulse voltage VF is applied to the primary winding 2a of the transformer 2. At that time, on the secondary side of the transformer 2, the sustaining voltage pulse Vp is applied between the sustaining electrode X and the scanning electrode Y of the PDP 20, and the panel capacitance Cp is charged / discharged.

The controller 30 reverses the polarity of the sustaining voltage pulse Vp as follows by the on / off control of the sustaining pulse generator 5 with respect to the switching elements Q1 to Q4.
FIG. 3 is a waveform diagram showing the potentials VX and VY of the sustain electrode X and the scan electrode Y of the PDP 20, the discharge sustain pulse voltage Vp, and the current IL flowing through the inductor L during the discharge sustain period.
A voltage VX−VY between the sustain electrode X and the scan electrode Y is applied to the discharge cell of the PDP 20 as a discharge sustain pulse voltage Vp: Vp = VX−VY. On the other hand, the sustaining voltage pulse Vp is equal to the voltage across the inductor L.

When the first high-side switch element Q1 and the second low-side switch element Q4 maintain the on state and the other switch elements Q2 and Q3 maintain the off state, the potential VX of the sustain electrode X is the power supply terminal 1T. The potential Vs of the scan electrode Y is maintained at the ground potential (≈0) (refer to the section I shown in FIG. 3). That is, the sustaining voltage pulse Vp maintains the positive peak value Vs.
When the discharge is maintained in the discharge cell of the PDP 20, electric power for maintaining the discharge current is supplied to the discharge cell through the power supply terminal 1T.
On the other hand, since the voltage Vp across the inductor L is maintained at a constant value Vs, the current IL flowing through the inductor L increases linearly in the direction of the arrow shown in FIG.

When the above state is maintained for a predetermined time, the control unit 30 turns off the first high-side switch element Q1 and the second low-side switch element Q4 (see time T1 shown in FIG. 3). At that time, resonance occurs between the inductor L and the panel capacitance Cp.
At the start of the resonance, the current IL flowing through the inductor L quickly discharges the panel capacitance Cp and further charges in the opposite direction. Along with this, the potential VX of the sustain electrode X quickly decreases, and the potential VY of the scan electrode Y rapidly increases (see section II shown in FIG. 3). That is, the sustaining voltage pulse Vp quickly reverses the polarity from positive to negative.

When the voltage Vp across the panel capacitance Cp reaches the negative peak value −Vs, the control unit 30 turns on the first low-side switch element Q2 and the second high-side switch element Q3 (time T2 shown in FIG. 3). reference). At that time, since the both-end voltage is substantially equal to zero in each of the first low-side switch element Q2 and the second high-side switch element Q3, no switching loss occurs. By this switching, the potential VX of the sustain electrode X is maintained at the ground potential, and the potential VY of the scan electrode Y is maintained at the potential Vs of the power supply terminal 1T (see section III shown in FIG. 3). That is, the sustaining voltage pulse Vp is maintained at the negative peak value −Vs.
When the discharge is maintained in the discharge cell of the PDP 20, electric power for maintaining the discharge current is supplied to the discharge cell through the power supply terminal 1T.
On the other hand, since the voltage Vp across the inductor L is maintained at a constant value −Vs, the current IL flowing through the inductor L increases linearly in the direction opposite to the arrow shown in FIG.

When the above state is maintained for a predetermined time, the control unit 30 turns off the first low-side switch element Q2 and the second high-side switch element Q3 (see time T3 shown in FIG. 3). At that time, resonance occurs between the inductor L and the panel capacitance Cp.
At the start of the resonance, the current IL flowing through the inductor L quickly discharges the panel capacitance Cp and further charges in the opposite direction. Along with this, the potential VX of the sustain electrode X rises rapidly, and the potential VY of the scan electrode Y falls quickly (see section IV shown in FIG. 3). That is, the sustaining voltage pulse Vp quickly reverses the polarity from negative to positive.

When the sustaining voltage pulse Vp reaches the positive peak value Vs, the control unit 30 turns on the first high-side switch element Q1 and the second low-side switch element Q4 (see time T4 shown in FIG. 3). At that time, in both the first high-side switch element Q1 and the second low-side switch element Q4, the voltage across the terminals is substantially equal to zero, so that no switching loss occurs. By the switching, the potential VX of the sustain electrode X is maintained at the potential Vs of the power supply terminal 1T, and the potential VY of the scan electrode Y is maintained at the ground potential. That is, the sustaining voltage pulse Vp is maintained at the positive peak value Vs.
Thus, the state in the section I shown in FIG. 3 is restored.

During the discharge sustain period, the control unit 30 repeats the above-described on / off control for the switch elements Q1 to Q4. Thereby, the sections I to IV shown in FIG. 3 are repeated.
In particular, in the section II / IV corresponding to the rising / falling period of the sustaining voltage pulse Vp, as described above, the inductor L resonates with the panel capacitance Cp. The resonance inverts the polarity of the sustaining voltage pulse Vp quickly and smoothly. At that time, almost no power is consumed, and is exchanged between the inductor L and the panel capacitance Cp. That is, during the resonance period II / IV, the power consumed by the respective resistances (not shown) of the switching elements Q1 to Q4, the sustain electrode X and the scan electrode Y of the PDP 20, and the lead wire is suppressed. Thus, the reactive power due to charging / discharging of the panel capacitance Cp is reduced during the discharge sustain period.

At the end of the discharge sustain period, for example, when the last rise of the sustain pulse voltage Vp corresponds to the rise of the potential VX of the sustain electrode X as shown in FIG. One low-side switch element Q2 and the second high-side switch element Q3 are turned off (see time T5 shown in FIG. 3). At that time, resonance occurs between the inductor L and the panel capacitance Cp.
At the start of the resonance, the current IL flowing through the inductor L quickly discharges the panel capacitance Cp. Along with this, the potential VX of the sustain electrode X quickly decreases, and the potential VY of the scan electrode Y rapidly increases (see section V shown in FIG. 3). That is, the sustaining voltage pulse Vp drops.
When the sustaining voltage pulse Vp reaches the negative peak value −Vs, the control unit 30 turns on the first high-side switch element Q1 and the second low-side switch element Q4 (see time T6 shown in FIG. 3). . At that time, the current IL flowing through the inductor L flows as a regenerative current to the power supply terminal 1T through the first high-side switch element Q1. Further, immediately before the current IL flowing through the inductor L is attenuated to zero, the control unit 30 turns off the first high-side switch element Q1 and the second low-side switch element Q4. Thereby, all the energy remaining in the inductor L is regenerated in the DC-DC converter 1.
The regeneration period immediately after the discharge sustain period, that is, the period during which the potential VY of the scan electrode Y is maintained high (section VI shown in FIG. 3) is preferably used as part of the initialization pulse voltage in the next initialization period. Is done.
Thus, the efficiency at the end of the discharge sustain period is improved.

  Apart from the above, the control unit 30 turns off both the first high-side switch element Q1 and the second low-side switch element Q4 at the end of the discharge sustain period, that is, in the sections V and VI shown in FIG. The state may be maintained. Since the discharge current is cut off during the off period, the discharge cell of the PDP 20 cannot accumulate new wall charges. Therefore, the transition to the next initialization period is smooth. Particularly preferably, the voltage change in the off period is used as a part of the initialization pulse voltage in the next initialization period.

  In the PDP driving apparatus 10 according to the embodiment of the present invention, unlike the conventional driving apparatus, the current IL flowing through the inductor L is not cut off throughout the discharge sustaining period. However, since the inductor L is connected in parallel with the panel capacitance Cp, the resonance period II / IV is limited to the rising / falling period of the sustaining voltage pulse Vp. Therefore, the above resonance does not adversely affect the image of the PDP 20. Furthermore, since the ringing associated with the resonance does not have to be taken into account when the PDP 20 emits light, the withstand voltage of the circuit elements of the PDP driving device 10 may be low.

In addition, the current IL continues to flow through the inductor L during periods other than the resonance period (sections II and IV shown in FIG. 3) with the panel capacitance Cp (see sections I and III shown in FIG. 3). In particular, at the start of resonance between the inductor L and the panel capacitance Cp, the current IL flowing through the inductor L is relatively large (see times T1 and T3 shown in FIG. 3). Accordingly, the charging / discharging of the panel capacitance Cp due to resonance is fast, and the rising / falling of the sustaining voltage pulse Vp is fast. That is, the rising / falling period of the sustaining voltage pulse Vp is shortened. As a result, since the discharge sustain period is shortened, the number of subfields per field is easily increased.
Thus, the PDP driving apparatus 10 according to the embodiment of the present invention easily realizes further refinement of the gradation of the PDP 20, that is, further improvement of the image quality.

  In the PDP driving apparatus 10 according to the embodiment of the present invention, the current IL flowing through the inductor L may not be controlled by the switch element. Thereby, the PDP driving device 10 described above has a small number of components and a small mounting area.

  The sustaining pulse generator 5 according to the embodiment of the present invention includes a full-bridge inverter as shown in FIG. In addition, the discharge sustaining pulse generation unit may include a half-bridge inverter, for example, one obtained by replacing the second high-side switch element Q3 and the second low-side switch element Q4 with capacitors.

  The present invention relates to a drive device for a capacitive load such as a PDP, for example. As described above, while a pulse voltage is repeatedly generated, energization of an inductor connected in parallel with the capacitive load is continued. Thus, the present invention is clearly industrially applicable.

It is a block diagram which shows the structure of the plasma display by embodiment of this invention. FIG. 4 is an equivalent circuit diagram of the sustain electrode driving unit 2, the scan electrode driving unit 3, and the PDP 20 in the sustain period for the PDP driving device according to the embodiment of the present invention. The PDP driving device according to the embodiment of the present invention shows the potentials VX and VY of the sustain electrode X and the scan electrode Y of the PDP 20, the discharge sustain pulse voltage Vp, and the current IL flowing through the inductor L during the discharge sustain period. It is a waveform diagram. It is a block diagram which shows the structure of the conventional plasma display. FIG. 6 is an equivalent circuit diagram of sustain electrode driver 2, scan electrode driver 3, and PDP 20 in a discharge sustain period for a conventional PDP driver having two similar power recovery units 6A and 6B. FIG. 6 is an equivalent circuit diagram of sustain electrode driver 2, scan electrode driver 3, and PDP 20 in a discharge sustain period for a conventional PDP driver having a power recovery unit 6C different from FIG.

Explanation of symbols

1T power terminal
2 Sustain electrode drive
Q1 First high-side switch element
Q2 First low-side switch element
3 Scan electrode driver
Q3 Second high-side switch element
Q4 Second low-side switch element
5 Discharge sustain pulse generator
L inductor
20 PDP
Panel capacity of Cp PDP20
X PDP20 sustain electrode
Y PDP20 scan electrode

Claims (10)

A device for applying a predetermined pulse voltage to a capacitive load;
A pulse generation unit including a switch element for converting a predetermined DC voltage into the pulse voltage by switching of the switch element; and
An inductor connected in parallel with the capacitive load, to which the pulse voltage is applied, and to maintain an energized state;
A capacitive load driving device.   The capacitive load driving device according to claim 1, wherein the inductor resonates with the capacitive load during a rising period and a falling period of the pulse voltage.   The capacitive load driving device according to claim 1, wherein the pulse generator regenerates electric power from the inductor to the DC voltage supply source by switching of the switch element.   The pulse generation unit includes a high-side switch element and a low-side switch element as the switch elements, the high-side switch element and the low-side switch element are connected in series, and the high-side switch element and the low-side switch element The capacitive load driving device according to claim 1, wherein a connection point is connected to the capacitive load and the inductor.   5. The capacitive load drive according to claim 4, wherein at the end of application of the pulse voltage, either the high-side switch element or the low-side switch element is turned on, and a regenerative current is passed from the inductor to the DC voltage supply source. apparatus. A rectifying unit for converting an AC voltage from an external power source into a predetermined DC voltage;
A plasma display panel (PDP) driving device for converting the DC voltage into a predetermined pulse voltage; and
A PDP comprising: a discharge cell that emits light by discharge of gas enclosed therein; and a plurality of electrodes for applying the pulse voltage to the discharge cell;
A plasma display having
The PDP driving device is
A pulse generator for converting the DC voltage into the pulse voltage by switching the switch element; and
An inductor connected in parallel with the capacitance between the electrodes, to which the pulse voltage is applied, and to maintain an energized state;
A plasma display.   The plasma display according to claim 6, wherein the inductor resonates with the capacitance between the electrodes during a rising period and a falling period of the pulse voltage.   The plasma display according to claim 6, wherein the pulse generator regenerates power from the inductor to the rectifier by switching of the switch element.   The pulse generation unit includes a high-side switch element and a low-side switch element as the switch elements, the high-side switch element and the low-side switch element are connected in series, and the high-side switch element and the low-side switch element The plasma display according to claim 6, wherein a connection point is connected to the electrode and the inductor.   10. The plasma display according to claim 9, wherein at the end of application of the pulse voltage, one of the high-side switch element and the low-side switch element is turned on, and a regenerative current is passed from the inductor to the rectifying unit.

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