Power consumption controller, image processor, self-luminous display apparatus, elelcrtonic equipment, power consumption control method and computer program

The prior art power consumption control techniques convert the video signal (gray level) in one way or another based on the estimated power consumption level. The present invention proposes a power consumption controller which includes (a) a power consumption calculation section which sequentially calculates the power consumption level of a self-luminous display device based on a video signal input from the beginning of each frame up to the time of calculation, (b) a power consumption status determination section which determines whether the calculated power consumption level exceeds a reference value for comparison by constantly comparing the two levels. If this is the case, the same section detects the timing at which the power consumption exceeds the reference value for comparison and (c) a peak brightness control section which controls the peak brightness of the self-luminous display device if the power consumption level exceeds the reference value for comparison based on the detected timing.

TECHNICAL FIELD

The invention described in this specification relates to a technique for controlling the power consumption of a self-luminous display apparatus to within an allowable limit.

It should be noted that the invention proposed by the inventors relates to a power consumption controller, an image processor, a self-luminous display apparatus, electronic equipment, a power consumption control method and a computer program.

BACKGROUND ART

A self-luminous display device has the property that the power consumption changes at all times depending on the image displayed. Therefore, the establishment of a technique is required which can control the power consumption of a self-luminous display device to within an allowable range.

Among examples of power consumption control techniques is that descried in Japanese Patent Laid-Open No. 2004-354762.

Japanese Patent Laid-Open No. 2004-354762 discloses an arrangement which estimates the power consumption of the entire screen based on a video signal (gray level) per frame stored in a frame memory and converts the video signal (gray level) stored in the frame memory according to the estimated power consumption.

DISCLOSURE OF THE INVENTION

In the case of the invention described in Japanese Patent Laid-Open No. 2004-354762, however, the video signal (gray level) is converted in one way or another based on the estimated power consumption level. That is, even an image which inherently does not require any conversion (which does not consume power beyond the allowable limit) is subjected to conversion which entails image quality degradation.

For this reason, the inventors propose a power consumption controller which includes (a) a power consumption calculation section, (b) a power consumption status determination section and (c) a peak brightness control section. The power consumption calculation section sequentially calculates the power consumption level of a self-luminous display device based on a video signal input from the beginning of each frame up to the time of calculation. The power consumption status determination section determines whether the calculated power consumption level exceeds a reference value for comparison by constantly comparing the two levels. If this is the case, the same section detects the timing at which the power consumption exceeds the reference value for comparison. The peak brightness control section controls the peak brightness of the self-luminous display device if the power consumption level exceeds the reference value for comparison based on the detected timing.

The control technique proposed by the inventors makes it possible to calculate the power consumption of a self-luminous display device in real time despite using a simple system configuration, thus controlling the power consumption only if the allowable limit is exceeded.

BEST MODE FOR CARRYING OUT THE INVENTION

The power consumption control techniques according to the present invention will be described below.

It should be noted that well-known or publicly known techniques in the pertaining technical field are applied to any item which is not particularly illustrated or described in the present specification.

It should also be noted that the embodiments described herein are merely exemplary and that the invention is not limited to such examples.

The first control technique proposed by the inventors will be described below.

(A-1) Configuration of the Self-Luminous Display Panel

Here, we assume that an organic EL display panel is used which has pixels arranged in a matrix form. That is, we assume that the self-luminous display panel used has organic-EL elements provided at intersections between Y electrodes (data lines) and X electrodes (gate lines) on a glass substrate. It should be noted that the organic EL panel is designed to display color image. Therefore, each pixel on the display includes subpixels of RGB.

It should also be noted that linear sequential scanning is used to drive the organic EL display panel. That is, the drive method used controls the lighting of pixels on a horizontal line by horizontal line basis.

In the present embodiment, however, the organic EL panel used incorporates a capacitor in a pixel circuit for each of the organic EL elements.

In this organic EL display panel, therefore, written gray level information (voltage level) is held until a next write timing thanks to the storage capability of the capacitor incorporated. As a result, the organic EL display panel lights up in the same manner as in frame sequential scanning. That is, gray level information (voltage level) is written on a horizontal line by horizontal line basis, and the lighting of each pixel based on the gray level information (voltage level) is maintained for one frame from the moment of writing.

(A-2) Basic Configuration of the Power Consumption Controller

FIG. 1illustrates the basic configuration of a power consumption controller1proposed by the inventors. The same controller1includes three functional blocks, namely, a power consumption calculation section3, a power consumption status determination section5and a peak brightness control section7.

The power consumption calculation section3is a processing device operable to sequentially calculate the power consumption level of the self-luminous display device based on a video signal input from the beginning of each frame up to the time of calculation. That is, the same section3resets the calculated value when a vertical synchronizing signal is detected. Thereafter, the same section3cumulatively updates the power consumption on a pixel by pixel basis or at intervals of one horizontal line period according to the input video signal (nature of the image).

The power consumption status determination section5is a processing device operable to determine whether the calculated power consumption level exceeds the allowable limit (reference value for comparison) by constantly comparing the two levels. If this is the case, the same section5detects the timing at which the power consumption exceeds the reference value for comparison.

This determination is most accurate when the display screen lights up almost uniformly as a whole. Incidentally, we assume that the display screen lights up almost uniformly as a whole. Then, the larger the power consumed per frame, the earlier the power consumption level per frame exceeds the allowable limit (reference value for comparison) after the beginning of reception of a video signal for the frame. It should be noted that the timing at which the allowable limit is exceeded is determined on a pixel by pixel or horizontal line by horizontal line basis although this timing is affected by the timing at which the power consumption level is updated.

The peak brightness control section7is a processing device operable to control the peak brightness of an organic EL panel module9if the power consumption level exceeds the allowable limit (reference value for comparison). The same section7does so based on the detected timing. To control the peak brightness, the same section7changes the length of lighting time per frame (duty pulse length). Alternatively, the same section7controls the supply or interruption of supply voltage required to light up and drive the organic EL elements. The control procedures for the two methods will be described later.

(a) Internal Configuration of the Power Consumption Calculation Section3

FIG. 2illustrates the functional block configuration of the power consumption calculation section3. In the present embodiment, the same section3includes three functional blocks, namely, a current conversion section11, a current accumulation section13and a power consumption calculation section15.

The current conversion section11is a processing device operable to convert a video signal for each pixel (gray level) into a current i. In the present embodiment, the same section11converts the gray level for each pixel into a current using a conversion table which stores the relationship between the gray level and the current flowing through the organic EL element.

FIG. 3illustrates an example of relationship between the gray level and the current. As illustrated inFIG. 3, a non-linear relationship is generally observed between the gray level and the current. This relationship can be found by experiment in advance. In the present embodiment, this relationship is stored in the conversion table.

The current accumulation section13is a processing device operable to calculate the sum of the current i for a video signal input from the beginning of each frame up to the time of calculation. Basically, the total current is updated on a pixel by pixel basis. However, the total current may also be calculated every horizontal line period by accumulating the current for the horizontal resolution.

The power consumption calculation section15is a processing device operable to calculate power W (=IXVcc; Vcc is a supply voltage applied to the organic EL element) consumed by displaying the video signal input from the beginning of each frame up to the time of calculation. To do so, the same section15multiplies a total current I (=Σi) by the supply voltage Vcc. In the case of an ordinary display system, the supply voltage Vcc is fixed. However, if the supply voltage Vcc is varied, for example, to control the peak brightness, the supply voltage Vcc at the time of calculation is used.

(b) Internal Configuration of the Power Consumption Status Determination Section

FIGS. 4(A) to 4(D)illustrate the details of the processing performed by the power consumption status determination section5. Incidentally,FIG. 4(A)illustrates a vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 4(B)illustrates video signal trains which appear during a frame period. Video signal trains appear in synchronism with a horizontal synchronizing pulse. As many of signal trains as the vertical resolution appear.

FIGS. 4(C) and 4(D)illustrate the change in power consumption resulting from displaying a video signal input during a frame period. However, if the video signal is a moving image, an error may occur between the calculated and actual power consumption levels depending on the nature of the peak brightness control method.

The reason for the above is as follows. The power consumption W calculated by the power consumption calculation section3represents only the power consumed by writing the video signal (gray level) to the pixel circuits. Therefore, the power consumption W does not reflect the power consumed by the pixels in which the organic EL element continues to emit light due to the video signal written during the previous frame period.

FIG. 4(C)illustrates the case in which the power consumption calculated based on the video signal making up one frame remains below the allowable limit. In this case, the power consumption status determination section5does not output any signal indicating that the allowable limit has been exceeded.

On the other hand,FIG. 4(D)illustrates the case in which the power consumption calculated based on the video signal making up one frame exceeds the allowable limit halfway through the frame period. In this case, the power consumption status determination section5outputs an over-limit timing signal indicating that the allowable limit has been exceeded upon exceeding of the limit.

An over-limit timing signal is output on a pixel by pixel or horizontal line by horizontal line basis. Naturally, the timing can be detected with more precision if the signal is output on a pixel by pixel basis. However, the appropriate one of the two choices is selected in consideration of various factors, including the accuracy required of the calculation, the load required for the calculation and effects to be achieved by the peak brightness control.

(A-3) Control Operation and Effects

A description will be made below about the power consumption control performed by the power consumption controller1having the above functional configuration in terms of the processing steps.

FIG. 5illustrates the steps until the power consumption level is calculated.FIG. 6illustrates the steps until the details of the peak brightness control to be exercised based on the calculated power consumption level are determined.

First, the power consumption calculation section3converts the video signal (gray level) that is sequentially input into the current i (S1). Next, the same section3cumulatively adds up the current i for each pixel obtained by the conversion to calculate the total current I (S2).

After the total current I is calculated, the same section3multiplies the total current I by the supply voltage Vcc to calculate the power W consumed by displaying the video signal input from the beginning of each frame up to the time of calculation (S3). It should be noted that the power W is transmitted to the power consumption status determination section5each time it is updated. It should also be noted that the above processing steps are repeated.

Upon receipt of the current power consumption level W, the power consumption status determination section5determines whether the power consumption level W exceeds the allowable limit (S11).

When the power consumption level W remains below the allowable limit (when the determination is negative), the peak brightness control section7maintains the set peak brightness condition (S12).

That is, the same section7outputs the preset peak brightness condition to the organic EL panel module9. Then, the same section7determines whether the frame period has ended. While the determination is negative, the same section7returns to step S11(S13). Incidentally, if the determination is affirmative (if the frame has ended), the same section7resets the peak brightness condition to be ready for the processing in the next frame period.

On the other hand, if the power consumption level exceeds the allowable limit (if the determination is affirmative in step S11), the same section7changes the peak brightness condition to suit the detected timing (over-limit detection timing). In this case, the same section7changes the peak brightness condition so as to reduce the lighting time of the organic EL element per frame and outputs the changed condition to the organic EL panel module9.

For example, the peak brightness condition is, changed so that the earlier the detection of the over-limit timing signal appears, the shorter the duty pulse length. It should be noted that the duty pulse is transmitted one line at a time to the next stage starting from the first line on the display panel in synchronism with the horizontal synchronizing pulse. Therefore, the duty pulse with a reduced lighting time propagates over the entire screen over one frame period. This translates to uniformly shorter lighting time of the horizontal lines, thus suppressing the power consumption during this period.

Moreover, for example, the earlier the detection of the over-limit timing signal appears, the earlier in the frame period the supply voltage Vcc is changed to 0 V. It should be noted that, in the case of an ordinary display panel, the supply voltage Vcc is applied commonly to all the pixels (all the organic EL elements). Therefore, if the supply voltage Vcc is changed to 0V, the entire screen is unlit (black screen) from the moment of change to the end of the frame. Although this causes the screen to look dark to the user, the power consumption can be positively suppressed.

The repetition of the above processing steps keeps down the power, consumption of the organic EL panel module9. Further, the peak brightness control is carried out only if the power consumption level exceeds the allowable limit. Therefore, so long as the power consumption level remains below the allowable limit, the image will be displayed at the optimal quality under the preset peak brightness condition.

In addition, this processing method requires absolutely no frame memories. This ensures downsizing of the processing system. Therefore, if the power consumption controller1is incorporated in an organic EL display apparatus or other electronic equipment, it can be incorporated in part of the existing semiconductor circuitry. This eliminates the need to provide a new space or external wirings at the time of incorporation.

Here, the second control technique proposed by the inventors will be described below. The second control technique employs the same procedures as the first technique with the exception of the concrete procedure for the peak brightness control. Therefore, the self-luminous display panel and the power consumption controller used remain unchanged in basic configuration from those in the control technique1.

(B-1) Basic Configuration of the Power Consumption Controller

FIG. 7illustrates the basic configuration of a power consumption controller21proposed by the inventors. The same controller21includes three functional blocks, namely, the power consumption calculation section3, a power consumption status determination section23and a peak brightness control section25. A description will be made below about the power consumption status determination section23and the peak brightness control section25.

The power consumption status determination section23is a processing device operable to determine whether the calculated power consumption level exceeds each of two reference values for comparison (allowable limit and half the allowable limit) by constantly comparing the power consumption level against each of the two reference values.

The power consumption status determination section calculates the difference between the current power consumption and the allowable limit if the power consumption level exceeds half the allowable limit. The same section23continues this calculation until the power consumption level exceeds the allowable limit. Also in this case, the timing at which the allowable limit is exceeded is determined on a pixel by pixel or horizontal line by horizontal line basis.

The peak brightness control section25is a processing device operable to control the peak brightness of the organic EL panel module9so that the peak brightness gradually decreases while the power consumption level exceeds half the allowable limit but not the allowable limit. The same section25does so based on a parameter indicating the point in time of processing (scan position/vertical resolution) and another parameter indicating available power (=(allowable limit-current power consumption level)/allowable limit).

It should be noted, however, the peak brightness control section25controls the peak brightness so as to reduce the brightness down to zero if it receives an input indicating that the power consumption level exceeds the allowable limit.

As described above, the peak brightness control section25differs from the counterpart used in the control technique1in that the same section25does not force the peak brightness down to zero, but instead controls the peak brightness in consideration of the current power consumption level, over-limit timing and other factors so that the peak brightness varies at a smaller rate and more mildly.

It should be noted that the peak brightness is controlled in the same manner as in the control technique1. That is, the length of lighting time per frame (duty pulse length) is changed. Alternatively, the supply voltage required to light up and drive the organic EL element is sequentially changed.

(a) Internal Configuration of the Power Consumption Status Determination Section

FIGS. 8(A) to 8(D)illustrate the details of the processing performed by the power consumption status determination section23. Incidentally,FIG. 8(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 8-(B) illustrates video signal trains which appear during a frame period. Video signal trains appear in synchronism with a horizontal synchronizing pulse. As many of signal trains as the vertical resolution appear.

FIGS. 8(C) and 8(D)illustrate the change in power consumption resulting from displaying the video signal input during a frame period.

FIG. 8(C)illustrates the case in which the power consumption calculated based on the video signal making up one frame remains below half the allowable limit. In this case, the power consumption status determination section23does not output any over-limit signal indicating that the allowable limit has been exceeded.

On the other hand,FIG. 8(D)illustrates the case in which the power consumption calculated based on the video signal making up one frame exceeds both half the allowable limit and the allowable limit halfway through a frame period. In this case, the power consumption status determination section23outputs an over-limit timing signal indicating that half the allowable limit or the allowable limit has been exceeded upon exceeding of each limit.

(B-2) Control Operation and Effects

A description will be made below about the power consumption control performed by the power consumption controller21having the above functional configuration in terms of the processing steps. It should be noted that the steps up to the calculation of the power consumption level are the same as in the control technique1, and therefore the description thereof will be omitted.

FIG. 9illustrates the steps after the power consumption level is calculated.

Upon receipt of the current power consumption level W, the power consumption status determination section23determines whether the power consumption level W exceeds half the allowable limit (S21).

When the power consumption level W remains below the allowable limit (when the determination is negative), the peak brightness control section23maintains the set peak brightness condition (S22).

That is, the same section23outputs the preset peak brightness condition to the organic EL panel module9. Then, the same section23determines whether the frame period has ended. While the determination is negative, the same section25returns to step S21(S23). Incidentally, if the determination is affirmative (if the frame has ended), the peak brightness control section25resets the peak brightness condition to be ready for the processing in the next frame period.

On the other hand, if the power consumption level exceeds half the allowable limit (if the determination is affirmative in step S21), the same section25further determines whether the power consumption level exceeds the allowable limit (S24).

If the determination is affirmative (if the power consumption level exceeds the allowable limit), the same section25reduces the peak brightness condition to zero (S25).

On the other hand, when the determination is negative (when half the allowable limit<power consumption<allowable limit), the same section25changes the peak brightness condition to match the available power and current position (S26).

Basically, the same section25controls the peak brightness so that the earlier the half the allowable limit is exceeded, the smaller the peak brightness so as to keep down power consumption thereafter.

Practically, the same section25employs these two control conditions in a combined manner to determine the peak brightness condition. As a result, the same section25controls the peak brightness so that the peak brightness gradually decreases between the set peak brightness and zero until the current power consumption level exceeds the allowable limit.

The repetition of the above processing steps is expected to basically provide the same effects as in the control technique1. It should be noted that the present control technique does not reduce the peak brightness suddenly from the set brightness to zero, thus keeping image quality degradation to a minimum.

(C) Concrete Example

As a follow-up to the description given above, concrete examples of devices using the control techniques1and2will be described.

(C-1) Concrete Example 1 (Controlling the Duty Pulse Length Using the Control Technique1)

FIG. 10illustrates an example of a display apparatus which will be described in this concrete example. It should be noted that the same reference numerals as inFIG. 1are used to denote the like components inFIG. 10. Here, the display apparatus includes the organic EL panel module9and a power consumption controller51.

(a) Functional Configuration of the Organic EL Panel Module

First, a description will be made about a configuration example of the organic EL panel module9which is also used in other concrete examples.

The organic EL panel module9includes a timing control section31, a data line driver33, gate line drivers35and37and an organic EL display panel39.

The timing control section31is a processing device operable to generate timing signals required for screen display based on a video signal.

The data line driver33is a circuit operable to drive data lines of the organic EL display panel39. The same driver33converts the gray level which specifies the emission brightness of each pixel into an analog voltage level and supplies the voltage to the associated data line. The same driver33includes a well-known drive circuit.

The gate line driver35is a circuit operable to select and drive, through linear sequential scanning, a gate line provided for selection of a horizontal line to which to write the gray level. The same driver35includes a shift register having as many stages as the vertical resolution. A horizontal line selection signal is sequentially shifted in synchronism with a horizontal synchronizing pulse and applied through the register stages to the gate line which runs horizontally. The same driver35also includes a well-known drive circuit.

The gate line driver37is a circuit operable to drive, through linear sequential scanning, a gate line provided for transfer of a duty pulse. The same driver37also includes a shift register having as many stages as the vertical resolution. In this application example, a duty pulse is fed to the first stage of the register at every horizontal synchronization timing.

The organic EL display panel39is a display device having display pixels arranged in a matrix form.FIG. 11illustrates a circuit example of a display pixel41. The display pixel41is disposed at an intersection between a data line and a gate line. The display pixel41includes a data switching element T1, a capacitor C1, a current supply element T2and an emission period control element T3.

Here, the data switching element T1is a transistor adapted to control the loading of a voltage level applied via the data line. The gate line driver35controls the loading timing.

The capacitor C1is a storage element adapted to hold the loaded voltage level for a period of one frame. The capacitor C1provides light emission as in frame sequential scanning.

The current supply element T2is a transistor operable to supply a drive current commensurate with the voltage level of the capacitor C1to an organic EL element D1.

The emission period control element T3is a transistor operable to control the supply or interruption of drive current to the organic EL element D1.

The emission period control element T3is disposed in series with the supply path of the drive current. The organic EL element D1is lit while the same element T3is on. On the other hand, the organic EL element D1is unlit while the same element T3is off.

FIGS. 12(A) and 12(B)illustrate an example of duty pulse used in this concrete example. As illustrated inFIG. 12(B), the length of time during which the duty pulse is at low level corresponds to the lighting time of the organic EL element D1. It should be noted that the maximum lighting time of the same element D1is one frame period as illustrated inFIG. 12(A). In the present concrete example, the preset duty pulse length is about 70% of the maximum lighting time.

(b) Functional Configuration of the Power Consumption Controller

A description will be made next about the functional block configuration of the power consumption controller51. The same controller51includes three functional blocks, namely, the power consumption calculation section3, the power consumption status determination section5and a duty pulse generating section53. The component specific to the present concrete example is the duty pulse generating section53. The same section53generates a set duty pulse or a duty pulse of arbitrary length and outputs the generated pulse to the organic EL panel module9.

The duty pulse generated by the duty pulse generating section53is given to the gate line driver37in the organic EL panel module9to control the lighting time of the organic EL display panel39. Naturally, the duty pulse is generated in synchronism with a vertical synchronizing pulse.

FIG. 13illustrates an example of internal configuration of the duty pulse generating section53. The same section53includes two functional blocks, namely, a set duty pulse generator61and a logical sum circuit63.

The set duty pulse generator61is a processing device operable to generate a duty pulse of preset fixed length.

The logical sum circuit63is a processing device operable to generate a duty pulse for control purposes by finding the logical sum of an over-limit timing signal and a set duty pulse. Incidentally, the over-limit timing signal is at low level until the power consumption level exceeds the allowable limit and maintained at high level after the allowable limit is exceeded.

FIGS. 14(A) to 14(D)illustrate the details of operation of the duty pulse generating section53.FIG. 14(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 14(B)illustrates the set duty pulse.FIG. 14(C)illustrates the over-limit timing signal output from the power consumption status determination section5.FIG. 14(D)illustrates the duty pulse output from the logical sum circuit63.

(c) Control Operation and Effects

FIGS. 15(A) to 15(D)illustrates the relationship between the calculated power consumption level and the generated duty pulse length.FIG. 15(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 15(B)illustrates video signal trains which appear during a frame period. Video signal trains appear in synchronism with a horizontal synchronizing pulse. As many of signal trains as the vertical resolution appear.

FIG. 15(C)illustrates the change in power consumption level per frame calculated by the power consumption calculation section3based on the input video signal.FIG. 15(C)shows the case in which the calculated power consumption level exceeds the allowable limit earlier than the set pulse length.

FIG. 15(D)illustrates the duty pulse output from the duty pulse generating section53.

As illustrated inFIG. 15(D), the duty pulse rises to high level when the power consumption level exceeds the allowable limit, considerably reducing the lighting time per frame period. Thus, the pulse length shorter than the set length keeps down the actual power consumption level.

It is to be noted that, in the present concrete example, the length of the duty pulse output from the duty pulse generating section53remains unchanged even if the power consumption level exceeds the allowable limit later than the set pulse length. Therefore, other control method is required to deal with the case as described above.

For example, a possible solution would be to express the timing at which the power consumption level exceeds the allowable limit within a frame period in percentage form and multiply the set pulse length by the percentage value. In this case, however, the control is delayed by one frame. Therefore, it is necessary, for example, to delay the video signal output by one frame.

(C-2) Concrete Example 2 (Controlling the Supply Voltage Using the Control Technique1)

FIG. 16illustrates an example of a display apparatus described in this concrete example. It should be noted that, also inFIG. 16, the same reference numerals as inFIG. 1are used to denote the like components. This display apparatus includes the organic EL panel module9and a power consumption controller71.

(a) Functional Configuration of the Organic EL Panel Module

A configuration example of the organic EL panel module9will be described first. The organic EL panel module9includes the timing control section31, the data line driver33, the gate line driver35, the organic EL display panel39and a supply voltage source81.

The organic EL panel module9in the present concrete example is identical to that in the concrete example 1 except for the supply voltage source81. Practically, however, a supply voltage source is provided in the concrete example 1. It should be noted that the supply voltage source in the concrete example 1 differs from that in the present concrete example in that it supplies voltage to both the capacitor C1and the current supply element T2and that the supply voltage level is fixed.

FIG. 17illustrates the connection between the organic EL panel module9and the display pixel in the present example. As illustrated inFIG. 17, the supply voltage generated by the supply voltage source81is applied only to one of the electrodes of the current supply element T2. It should be noted that a fixed potential is supplied to one of the electrodes of the capacitor C1from a supply voltage source which is not shown.

FIGS. 18(A) to 18(C)illustrate an example of supply voltage supplied from the supply voltage source81. As illustrated inFIG. 18(C), a constant supply voltage is basically supplied to the power line.FIG. 18(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 18(B)illustrates video signal trains which appear during a frame period.

(b) Functional Configuration of the Power Consumption Controller

The functional block configuration of the power consumption controller71will be described below. The same controller71includes three functional blocks, namely, the power consumption calculation section3, the power consumption status determination section5and a supply voltage control section73.

The component specific to the present concrete example is the supply voltage control section73. Although basically generating a constant voltage, the same section73forcefully resets the supply voltage level to zero from the moment when the power consumption level exceeds the allowable limit onward.

FIG. 19illustrates an example of internal configuration of the supply voltage control section73. The supply voltage control section73includes two functional blocks, namely, a supply voltage level memory83and a multiplying circuit85.

The supply voltage level memory83is a storage element adapted to store a supply voltage level determined in advance in consideration of the gamma characteristic of the organic EL element.

The multiplying circuit85is a processing device operable to multiply a set supply voltage level by an over-limit timing signal and output the result of multiplication as a supply voltage level. Incidentally, the over-limit timing signal is at high level until the power consumption level exceeds the allowable limit and is switched to low level after the allowable limit is exceeded.

FIGS. 20(A) to 20(C)illustrate the details of operation of the supply voltage control section73.FIG. 20(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 20(B)illustrates the over-limit timing signal.FIG. 20(C)illustrates the supply voltage level output from the supply voltage control section73.

(c) Control Operation and Effects

FIGS. 21(A) to 21(D)illustrate the relationship between the calculated power consumption level and the generated supply voltage level.FIG. 21(A)illustrates the vertical synchronizing pulse VS adapted to give the start position of a frame.FIG. 21(B)illustrates video signal trains which appear during a frame period. Video signal trains appear in synchronism with a horizontal synchronizing pulse. As many of signal trains as the vertical resolution appear.

FIG. 21(C)illustrates the change in power consumption level per frame calculated by the power consumption calculation section3based on the input video signal.FIG. 21(C)shows the case in which the calculated power consumption level exceeds the allowable limit earlier than the set pulse length.

FIG. 21(D)illustrates the supply voltage level output from the supply voltage control section73.

As illustrated inFIG. 21(D), the supply voltage level is forced down to zero when the power consumption level exceeds the allowable limit. This causes light emission of the entire screen to be halted until the termination of the frame.

This means that the lighting time per frame period is reduced considerably shorter than the set duty pulse length. Thus, if the power consumed by displaying the frame image exceeds the allowable limit, the screen is forced to turn off, positively keeping down the actual power consumption level.

In the present concrete example, the entire screen is turned off even if the power consumption level exceeds the allowable limit later than the set duty pulse length. In this regard, the reduction of power consumption is reflected earlier in the actual power consumption in the present concrete example than in the concrete example 1.

(C-3) Concrete Example 3 (Controlling the Supply Voltage Using the Control Technique2)

FIG. 22illustrates an example of a display apparatus described in this concrete example. It should be noted that the same reference numerals as inFIGS. 7 and 16are used to denote the like components inFIG. 22. This display apparatus includes the organic EL panel module9and a power consumption controller91. The organic EL panel module9includes the same components as those described in the concrete example 2.

(a) Functional Configuration of the Power Consumption Controller

The functional block configuration of the power consumption controller91will be described below. The same controller91includes three functional blocks, namely, the power consumption calculation section3, the power consumption status determination section23and a supply voltage control section93.

The component specific to the present concrete example is the supply voltage control section93. Although basically generating a constant voltage, the same section93operates so that the smaller the difference between the power consumption level at the time of calculation and the allowable limit, the more the same section93reduces the supply voltage level from the moment when the power consumption level exceeds half the allowable limit onward.

FIG. 23illustrates an example of internal configuration of the supply voltage control section93. The same section includes two functional blocks, namely, a supply voltage level memory95and an arithmetic circuit97.

The supply voltage level memory95is a storage element adapted to store a supply voltage level determined in advance in consideration of the gamma characteristic of the organic EL element.

The arithmetic circuit97is a processing device operable to output an appropriate supply voltage level based on the relationship in magnitude between a power consumption level Wnow at the time of calculation and two reference values for comparison (allowable limit and half the allowable limit). In this case, while the power consumption level Wnow remains below half the allowable limit, the arithmetic circuit97outputs the setting read from the supply voltage level memory95as is.

On the other hand, while the power consumption level Wnow exceeds half an allowable limit L but not the allowable limit L, the arithmetic circuit97outputs the supply voltage level calculated by the equation given below.
Supply voltage level=((L−Wnow)/L)×(Scan position/Vertical resolution)×Set voltage level

In this case, the scan position is given as the position relative to the first horizontal line at the time of calculation of the power consumption level Wnow. The earlier the power consumption level Wnow exceeds half the allowable limit L, the smaller the multiplier in the second term (=Scan position/Vertical resolution).

FIGS. 24(A) to 24(C) and 25(A) to 25(C)illustrate the details of operation of the supply voltage control section93. Incidentally,FIGS. 24(A) to 24(C)are associated with the case in which the power consumption level Wnow exceeds half the allowable limit L but not the allowable limit L until the end of the frame.FIGS. 25(A) to 25(C)are associated with the case in which the power consumption level Wnow exceeds the allowable limit L before the end of the frame.

FIGS. 24(A) and 25(A)illustrate the vertical synchronizing pulse VS adapted to give the start position of a frame.FIGS. 24(B1) and25(B1) illustrate an over-limit timing signal1adapted to give the timing at which the power consumption level Wnow exceeds half the allowable limit L.FIGS. 24(B2) and25(B2) illustrate an over-limit timing signal2adapted to give the timing at which the power consumption level Wnow exceeds the allowable limit L.

InFIGS. 24(B1) to24(B2), only the over-limit timing signal1changes from low to high level halfway through the frame. In contrast, inFIGS. 25(B1) to25(B2), both the over-limit timing signals1and2change from low to high level halfway through the frame.

FIGS. 24(C) and 25(C)illustrate the supply voltage level output from the supply voltage control section93.

As illustrated inFIGS. 24(C) and 25(C), the supply voltage level changes not in a binary manner but continuously to approach zero. Incidentally, if the power consumption level Wnow remains below the allowable limit L at the end of the frame, the supply voltage level changes so as to approach the level calculated according to the difference between the power consumption level Wnow and the allowable limit L. In any case, the brightness of the entire screen will drop uniformly. This minimizes image quality degradation as compared to the case where the screen is turned off in a binary manner.

(c) Control Operation and Effects

FIGS. 26(A) to 26(D) and 27(A) to 27(D)illustrate the relationship between the calculated power consumption level and the generated supply voltage level.FIGS. 26(A) and 27(A)illustrate the vertical synchronizing pulse VS adapted to give the start position of a frame.FIGS. 26(B) and 27(B)illustrate video signal trains which appear during a frame period. Video signal trains appear in synchronism with a horizontal synchronizing pulse. As many of signal trains as the vertical resolution appear.

FIGS. 26(C) and 27(C)illustrate the change in power consumption level per frame calculated by the power consumption calculation section3based on the input video signal.FIG. 26(C)is associated with the case where the power consumption level does not exceed the allowable limit until the end of the frame.FIG. 27(C)is associated with the case where the power consumption level exceeds the allowable limit before the end of the frame.

FIGS. 26(D) and 27(D)illustrate the supply voltage level output from the supply voltage control section73.

InFIG. 26(D), the power consumption level Wnow remains below the allowable limit L at the end of the frame. Therefore, the supply voltage level changes so as to approach the level calculated according to the final difference between the power consumption level Wnow and the allowable limit L. It should be noted that the organic EL element is illuminated by the duty pulse as well. Therefore, the supply voltage control is reflected only until the duty pulse remains at high level.

InFIG. 27(D), on the other hand, the power consumption level Wnow exceeds the allowable limit L at the end of the frame. Therefore, the supply voltage level drops from the setting down to zero before the end of the frame and remains at zero until the end of the frame thereafter. Also in this case, the organic EL element is illuminated by the duty pulse as well. Therefore, the supply voltage control is reflected only until the duty pulse is switched to low level or the supply voltage level reaches zero, whichever comes earlier.

In any case, the screen brightness is continuously reduced within a frame period, thus avoiding image quality degradation due to sudden decline in screen brightness. Naturally, if the power consumed by displaying the frame image exceeds the allowable limit, the entire screen is forced to turn off, positively keeping down the actual power consumption level.

(D) OTHER EMBODIMENTS

(D-1) Examples of Incorporation

Here, examples of incorporating the above-mentioned power consumption controller in other devices will be described.

The aforementioned power consumption controller may be incorporated in a self-luminous display apparatus (including a panel module)101as illustrated inFIG. 28.

The self-luminous display apparatus101illustrated inFIG. 28includes a display panel103and a power consumption controller105.

(b) Image Processor

The aforementioned power consumption controller may be incorporated in an image processor121as illustrated inFIG. 29. The image processor121supplies a video signal to a self-luminous display apparatus111.

The image processor121illustrated inFIG. 29includes an image processing section123and a power consumption controller125.

(c) Electronic Equipment

The aforementioned power consumption controller may be incorporated in various types of electronic equipment incorporating a self-luminous display apparatus, irrespective of whether the electronic equipment is portable or stationary. Further, the self-luminous display apparatus need not necessarily be incorporated in the electronic equipment.

(c1) Broadcast Wave Receiver

The aforementioned power consumption and peak brightness controllers may be incorporated in a broadcast wave receiver.

FIG. 30illustrates an example of functional configuration of the broadcast wave receiver. A broadcast wave receiver201includes a display panel203, a system control section205, an operation section207, a storage medium209, a power supply211and a tuner213as its main devices.

It should be noted that the system control section205includes, for example, a microprocessor. The same section205controls the entire operation of the system. The operation section207includes not only mechanical controls but also a graphical user interface.

The storage medium209is used as a storage area adapted to store not only image and video data to be displayed on the display panel203but also firmware and application programs. Battery power is used as the power supply211if the broadcast wave receiver201is portable. Naturally, commercial power is used if the broadcast wave receiver201is stationary.

The tuner213is a wireless-device operable to selectively receive the broadcast wave of the user-selected specific channel from among incoming broadcast waves.

The configuration of this broadcast wave receiver is applicable, for example, to television and radio program receivers.

(c2) Audio Device

FIG. 31illustrates an example of functional configuration of an audio device serving as an audio player to which the aforementioned power consumption and peak brightness controllers are applied.

An audio device301serving as an audio player includes a display panel303, a system control section305, an operation section307, a storage medium309, a power supply311, an audio processing section313and a speaker315as its main devices.

Also in this case, the system control section305includes, for example, a microprocessor. The same section305controls the entire operation of the system. The operation section307includes not only mechanical controls but also a graphical user interface.

The storage medium309is a storage area adapted to store not only audio data but also firmware and application programs. Battery power is used as the power supply311if the audio device301is portable. Naturally, commercial power is used if the audio device301is stationary.

The audio processing section313is a processing device operable to process audio data signals. The same section313also decompresses compression-coded audio data. The speaker315outputs reproduced sounds.

It should be noted that if the audio device301is used as an audio recorder, a microphone is connected in place of the speaker315. In this case, the audio device301provides the capability to compression-code audio data.

(c3) Communication Device

FIG. 32illustrates an example of functional configuration of a communication device to which the aforementioned power consumption and peak brightness controllers are applied. A communication device401includes a display panel403, a system control section405, an operation section407, a storage medium409, a power supply411and a wireless communication section413as its main devices.

It should be noted that the system control section405includes, for example, a microprocessor. The same section405controls the entire operation of the system. The operation section407includes not only mechanical controls but also a graphical user interface.

The storage medium409is used as a storage area adapted to store not only image and video data files to be displayed on the display panel403but also firmware and application programs. Battery power is used as the power supply411if the communication device401is portable. Naturally, commercial power is used if the communication device401is stationary.

The wireless communication section413is a wireless device operable to exchange data with other devices. The configuration of this communication device is applicable, for example, to a stationary telephone set and mobile phone.

(c4) Imaging Device

FIG. 33illustrates an example of functional configuration of an imaging device to which the aforementioned power consumption and peak brightness controllers are applied. An imaging device501includes a display panel503, a system control section505, an operation section507, a storage medium509, a power supply511and an imaging section513as its main devices.

It should be noted that the system control section505includes, for example, a microprocessor. The same section505controls the entire operation of the system. The operation section507includes not only mechanical controls but also a graphical user interface.

The storage medium509is used as a storage area adapted to store not only image and video data files to be displayed on the display panel503but also firmware and application programs. Battery power is used as the power supply511if the imaging device501is portable. Naturally, commercial power is used if the imaging device501is stationary.

The imaging section513includes, for example, a CMOS sensor and a signal processing section operable to process the output signal from the CMOS sensor. The configuration of this imaging device is applicable, for example, to a digital camera and video camcorder.

(c5) Information Processing Device

FIG. 34illustrates an example of functional configuration of a portable information processing device to which the aforementioned power consumption and peak brightness controllers are applied. An information processing device601includes a display panel603, a system control section605, an operation section607, a storage medium609and a power supply611as its main devices.

It should be noted that the system control section605includes, for example, a microprocessor. The same section605controls the entire operation of the system. The operation section607includes not only mechanical controls but also a graphical user interface.

The storage medium609is used as a storage area adapted to store not only image and video data files to be displayed on the display panel603but also firmware and application programs. Battery power is used as the power supply611if the information processing device601is portable. Naturally, commercial power is used if the information processing device601is stationary.

The configuration of this information processing device is applicable, for example, to a gaming machine, electronic book, electronic dictionary and computer.

(D-2) Display Apparatus

The foregoing embodiments were described by taking an organic EL display panel as an example. However, this display control technique is widely applicable to other types of self-luminous display apparatus. For example, the technique is applicable to display panels such as inorganic EL display panel and FED display panel.

(D-3) Computer Program

The power consumption and peak brightness controllers described in the foregoing embodiments can be implemented by hardware or software alone or the two in combination with each other, with each assigned to perform specific functions.

(D-4) Peak Brightness Control Timing

In the above description, the case was described where the peak brightness was controlled upon detection of the power consumption level in excess of half the allowable limit or the allowable limit on a pixel by pixel basis.

However, the peak brightness may be controlled in the next frame as illustrated inFIG. 35. It should be noted that the peak brightness control condition is determined on a pixel by pixel or horizontal line by horizontal line basis.FIGS. 35(A) and 35(B)illustrate the case where the duty pulse length is reduced to less than the set length.FIG. 35(A)illustrates the input timing of the vertical synchronizing pulse.FIG. 35(B)illustrates the waveform of the duty pulse output for control purposes. Naturally, this peak brightness control is applicable to supply voltage control.

Further, the peak brightness may be controlled in synchronism with the horizontal line timing. Also in this case, the peak brightness control condition is determined on a pixel by pixel or horizontal line by horizontal line basis. Incidentally,FIGS. 36(A) to 36(D)also illustrate the case where the duty pulse length is reduced to less than the set length. If the video signal is a still image, controlling the peak brightness in the next frame as described above eliminates any difference in brightness over the screen.

FIG. 36(A)illustrates the input timing of the vertical synchronizing pulse.FIG. 36(B)illustrates the input timing of the horizontal synchronizing pulse.FIG. 36(C)illustrates an example of the set duty pulse.FIG. 36(D)illustrates the duty pulse output for control purposes.

As illustrated inFIGS. 36(B) and 36(D), an over-limit timing occurs in the middle of a horizontal line period. However, the duty pulse length is reduced at the immediately following horizontal line timing. As described above, controlling the peak brightness on a pixel by pixel or horizontal line by horizontal line basis effectively keeps down power consumption, for example, if the video signal is a moving image.

(D-5) Duty Pulse

In the above description, the duty pulse was described as a signal adapted to control the lighting and non-lighting times per frame period. As illustrated inFIGS. 37(A) and 37(B), however, the duty pulse (FIG. 37(B)) may be defined as a signal adapted to control the lighting and non-lighting times per horizontal line period (FIG. 37(A)). This means that, of as many duty pulses generated per frame period as the vertical resolution, the length of a duty pulse generated at a given timing onward is varied.

Also in the above description, the case was described where the duty pulse was at high and low levels once each per frame period.

As illustrated inFIG. 38(B), however, the aforementioned control techniques are applicable when the duty pulse is at high and low levels a plurality of times each per frame period (FIG. 38(A)).

In the above description, the description of a concrete example was omitted in which the control technique 2 was combined with the continuous control of the duty pulse. However, if the current flowing through the emission period control element T3can be varied according to the amplitude of the duty pulse, the brightness can be continuously reduced by continuously varying the current flow through the same element T3.

In addition to the above, various other modifications are possible without departing from the scope of the invention. Further, various modifications and application examples created or combined based on the description herein are also possible.