CN100392878C

CN100392878C - LED drive device and LED drive method

Info

Publication number: CN100392878C
Application number: CNB2004800011227A
Authority: CN
Inventors: 尾崎丰
Original assignee: HUNET Inc
Current assignee: HUNET Inc
Priority date: 2003-04-01
Filing date: 2004-03-26
Publication date: 2008-06-04
Anticipated expiration: 2024-03-26
Also published as: JP4015965B2; CN1701448A; JP2004311460A

Abstract

Drive voltage of LED of each color is stored in application voltage storage registers (11,12,13) so that each LED is driven by independent drive voltage, thereby reducing the current consumption. Moreover, the data in the application voltage storage registers (11,12,13) can be rewritten via a storage value setting bus (14). When the LED's actually mounted have individual irregularities in minimum light emitting voltage, the voltage stored in the application voltage storage registers (11,12,13) can be modified according to the irregularities.

Description

Light emitting diode drive device

Technical field

The present invention be more particularly directed to a kind of R of making, G, B primitive colours LED (Light Emitting Diode, light-emitting diode) is luminous and the LED drive unit and the LED driving method of display color.

Background technology

In the past, in the liquid crystal indicator that uses R (red), G (green), B (indigo plant) primitive colours LED, for example realized opening the liquid crystal indicator of the field-sequential mode (abbreviating the FS mode as) that the 2000-241811 communique delivers the spy.The liquid crystal indicator of FS mode is at liquid crystal shutter back side configuration three-color LED, by making it synchronous at the liquid crystal shutter with each location of pixels of switch when lighting LED of all kinds successively at a high speed, thereby can show desired color at each location of pixels.

For example, in the time of showing redness, between the red LED light emission period, open liquid crystal shutter, then between the light emission period of green LED and blue led, close liquid crystal shutter.Show that green and blue situation also is same, only opens liquid crystal shutter, and close liquid crystal shutter between other LED light emission period between the LED of this color light emission period.

In addition, if between redness and green LED light emission period, open liquid crystal shutter then can show Y (yellow), if between redness and blue led light emission period, open liquid crystal shutter then can show M (carmetta), if between green and blue led light emission period, open liquid crystal shutter then can show C (dark green), if during luminous whole of red, green, blue look LED, open liquid crystal shutter then can show W (white).

Above-mentioned FS mode is with the additive color ratio juris, by make the three-color LED luminous demonstration that realizes color successively with the speed faster speed than people's vision response.In addition, adopt the FS mode, can under the condition of not using colour filter, demonstrate distinct color.

In recent years, along with popularizing of portable type electronic products such as mobile phone, people wish to realize to be installed in portable type electronic product and with the display unit of high-fineness display color.Here, as described above, because adopt the liquid crystal indicator of three-color LED not need colour filter, so can show with high brightness.

Yet in the liquid crystal indicator that uses three-color LED, operated by rotary motion has a plurality of led chips that constitute LED of all kinds, these a plurality of led chips is applied voltage make LED of all kinds luminous.Therefore, in a plurality of led chips, consume electric power.

Relatively, portable type electronic product is limited because of battery capacity, is few more good more so be used for the current sinking of display unit.Certainly, this not and be limited to portable type electronic product, reducing current sinking is that all electronic products are desired.

In addition, because the LED characteristic there are differences, so people require to eliminate this species diversity to carry out consistent demonstration.For eliminating this species diversity, the method that is adopted had the method that the resistance value corresponding with each LED finely tuned etc. in the past, but that the problem of aforesaid operations is its process is very complicated.

Summary of the invention

Main purpose of the present invention is to provide a kind of light emitting diode drive device that can effectively reduce current sinking.In addition, the present invention also aims to provide the light emitting diode drive device of the difference that can eliminate each light-emitting diode characteristic.

For this reason, the invention provides a kind of like this light emitting diode drive device, it has:

The supply voltage production part;

Apply the store voltages parts, for the red, green, blue light-emitting diode of all kinds that is arranged in the display unit, the required minimum of brightness of storing independently in order to obtain being greater than or equal to expectation brightness by light-emitting diode of all kinds applies magnitude of voltage as digital value;

Apply voltage and form parts, have and be used for being stored in that the described digital value that applies the store voltages parts is carried out the D/A converter of digital-to-analogue conversion and the voltage transitions that is used for described supply voltage production part is produced is the voltage variable parts through the voltage of the size of the analogue value of described D/A converter conversion;

The duty ratio memory unit, the duty ratio of storing the pulse-width signal that the brightness of light-emitting diode of all kinds is finely tuned by light-emitting diode of all kinds independently; And

The pulse width modulation controlled parts form the pulse-width signal of the duty ratio of being stored based on described duty ratio memory unit independently by light-emitting diode of all kinds, and light-emitting diode of all kinds is carried out pulse width modulation controlled independently,

Described apply voltage form parts light-emitting diode of all kinds is applied independently different apply voltage in, described pulse width modulation controlled parts make the control of the luminosity of light-emitting diode of all kinds near described expectation brightness.

In addition, above-mentioned purpose realizes by following manner: respectively light-emitting diode of all kinds is being applied under the state of minimum driving voltage, by by different PWM (pulse-width modulation) signal of light-emitting diode duty ratio of all kinds light-emitting diode of all kinds being carried out PWM control.

Description of drawings

Fig. 1 is the block diagram of structure of the LED drive unit of expression embodiment of the present invention 1;

Fig. 2 is the figure that is expressed as the required minimum voltage value of the expectation brightness that obtains LED of all kinds;

Fig. 3 is the block diagram of structure of the driving voltage setting device of expression embodiment;

Fig. 4 is used for illustrating the flow chart that applies voltage and duty ratio setting processing that is undertaken by the driving voltage setting device;

Fig. 5 is used for being illustrated as the duty ratio that obtains the expectation white balance to set the flow chart of handling;

Fig. 6 is used for being illustrated as the duty ratio that obtains the expectation white balance to set the chrominance space figure that handles;

Fig. 7 is the oscillogram that is used for illustrating the action of LED drive unit;

Fig. 8 is the block diagram of structure of the LED drive unit of expression embodiment 2;

Fig. 9 is the oscillogram that is used for illustrating the LED drive unit action of embodiment 2.

Embodiment

The present inventor is conceived to the following fact and finishes the present invention: for making R, G, B LED of all kinds is not all to be the same at all LED with the luminous needed voltage that applies of expectation brightness respectively, but according to LED of all kinds and different.

Main contents of the present invention are, when measuring red, green, blue LED of all kinds in advance and can obtain the minimum driving voltage of expectation brightness, the driving voltage of LED of all kinds are stored in the memory unit, LED of all kinds are applied the driving voltage of the value of being deposited.

Below, specify embodiment of the present invention with reference to accompanying drawing.

(embodiment 1)

At Fig. 1,10 represent the LED drive unit of embodiment of the present invention 1 on the whole.LED drive unit 10 is located at liquid crystal indicator, is used for R, G, the B three-color LED of drive arrangements at the liquid crystal panel back side.And as specific embodiment, the present embodiment will describe the situation that the present invention is applied to the liquid crystal indicator of field-sequential mode.

LED drive unit 10 has R (red) with applying store voltages register 11, G (green) with applying store voltages register 12 and B (indigo plant) with applying store voltages register 13.Above-mentioned each

register

11,12,13 is stored the magnitude of voltage that is applied to R, G, each LED of B respectively.Each

register

11,12,13 and storing value are set and are connected with bus 14, make each

register

11,12,13 store the magnitude of voltage that applies that LED of all kinds uses respectively by the storing value setting with bus 14 during production line under the product of LED drive unit 10.

LED of all kinds by each

register

11,12,13 output is imported into register selection circuit 15 with applying magnitude of voltage.The luminous timing signal TR of red LED, the luminous timing signal TG of green LED and the luminous timing signal TB of blue led input register are selected circuit 15, select according to this luminous timing signal that output R, G, B's apply any one of magnitude of voltage.

For example, when the logical value of the luminous timing signal TR of red LED is the logical value of " 1 " and green and the luminous timing signal TG of blue led, TB during for " 0 ", select output R with applying the magnitude of voltage that applies that store voltages register 11 stores.In this embodiment because show, so, then make LED of all kinds luminous successively with its 195Hz frequency of 3 times if field frequency is 65Hz with field-sequential mode.That is to say that register selects circuit 15 to select to export R successively with applying store voltages register 11, G with applying store voltages register 12 and B with applying 13 stored voltage values of store voltages register with the interval that is about 5mS.

After converting the analogue value to, digital simulation (DA) change-over circuit 17 of magnitude of voltage through applying voltage and forming portion 16 be output to voltage variable circuit 18 by register applying of selecting that circuit 15 selects.Voltage variable circuit 18 will be become by the voltage transitions that circuit for generating source voltage 19 produces corresponding to behind the voltage of the analogue value of D/A conversion circuit 17 inputs, offer LED unit 20.

As mentioned above, LED drive unit 10 has storage and is applied to LED of all

kinds register

11,12,13 with magnitude of voltage respectively, and offers LED after the voltage transitions that circuit for generating source voltage 19 produces being become the value of

register

11,12,13 storages.Thus, compare, can reduce consumption electric power with the situation that LED of all kinds is applied identical magnitude of voltage.

Fig. 2 is expressed as at LED of all kinds and obtains to expect that the required minimum of brightness applies magnitude of voltage (hereinafter referred to as minimum luminous voltage).From then on figure as can be known, the minimum luminous voltage of green LED and blue led much at one, but the minimum luminous voltage of red LED is lower than the minimum luminous voltage of the two.

LED drive unit 10 apply the minimum luminous voltage value that store voltages register 11,12,13 is being stored LED of all kinds.And in fact, in the minimum luminous voltage value of being stored, the value of red LED is lower than the value of green LED and blue led.That is to say, because of applying required minimal voltage, so can reduce current sinking LED of all kinds.

In addition, as can be seen from Figure 2, minimum luminous voltage also can be variant at LED of all kinds.For example, if red LED then is distributed in 1.75V between the 2.45V; And if green and blue led then are distributed in 2.9V between the 3.9V.And the difference of minimum luminous voltage is the difference of each product when resulting from manufacturing LED.

In this embodiment, be not only merely make be applied to red LED apply voltage less than the green and blue voltage that applies, also make of all kinds the storage that minimum luminous voltage is applied voltage in addition after the difference between each product is listed consideration in

register

11,12,13.Promptly can when reducing consumption electric power, obtain expectation brightness thus at LED of all kinds.The storage that 11,12,13 pairs in above-mentioned register of all kinds applies magnitude of voltage is to set by storing value to carry out with bus 14, and this part is with aftermentioned.

Get back to Fig. 1 now the structure of LED drive unit 10 is described.LED drive unit 10 has R duty ratio memory register 21, G duty ratio memory register 22 and B duty ratio memory register 23.Above-mentioned each

register

21,22 and 23 is being stored respectively to R, G, B LED of all kinds being carried out the pwm signal duty ratio data of PWM control.Each

register

21,22 and 23 is set with storing value and is connected with bus 14, during production line, makes each

register

21,22,23 store the duty ratio data that LED of all kinds uses respectively by the storing value setting with bus 14 under the product of LED drive unit 10.

Be output to PWM

waveform formation circuit

24,25,26 from the LED of all kinds of each

register

21,22,23 outputs respectively with the duty ratio data.Each PWM waveform forms the PWM waveform that

circuit

24,25,26 and clock signal clk synchronously form corresponding duty data.

The PWM waveform forms the base stage that

circuit

24,25,26 outputs to the PWM waveform according to the luminous timing signal TR of red LED, the luminous timing signal TG of green LED and the luminous timing signal TB of

blue led transistor

27,28,29.When the collector electrode of each

transistor

27,28,29 is connected respectively to the output of R, G, each LED of B, grounded emitter.

Thus, between the red LED light emission period, only there is the logical value of the luminous timing signal TR of red LED to be " 1 ", only there be the PWM waveform corresponding to form circuit 24 output pwm signals with red LED, and the electric current of corresponding this pwm signal flows to red LED, makes red LED luminous.Similarly, between the green LED light emission period, only there is the logical value of the luminous timing signal TG of green LED to be " 1 ", only there be the PWM waveform corresponding to form circuit 25 output pwm signals with green LED, and the electric current of corresponding this pwm signal flows to green LED, makes green LED luminous.And between the blue led light emission period, only have the logical value of the luminous timing signal TB of blue led to be " 1 ", and only have the PWM waveform corresponding to form circuit 26 output pwm signals, and the electric current of corresponding this pwm signal flow to blue led with blue led, make blue led luminous.

The structure of Fig. 3 display driver voltage setting device 30, this driving voltage setting device 30 is set and is stored in the magnitude of voltage that usefulness of all kinds applies store voltages register 11,12 and 13.Yet, the structure of driving voltage setting device 30 is the LED magnitudes of voltage of all kinds that apply store voltages register 11,12,13 for obtaining to be stored in, and also can obtain to be stored in the duty ratio data that the LED of all kinds of duty

ratio memory register

21,22,23 uses.

Driving voltage setting device 30 has brightness/chroma meter 31, is used to measure brightness and colourity from the transmitted light of LCD panel.And incide brightness/chroma meter 31 by light guide plate (not shown) and LCD panel 40 by the light that LED unit 20 sends.Apply the switch that assigned voltage drives LCD panel 40 to the liquid crystal of each location of pixels at the appointed time by LCD drive circuit (not shown), so that can carry out printing opacity or shading to the light that LED sends.And this LED unit 20, light guide plate and LCD panel 40 are to assemble during production line under the product.

Data by 31 resulting brightness of brightness/chroma meter and colourity are transferred in the microcomputer (Microcomputer) 32.And driving voltage setting device 30 has the magnitude of voltage of applying configuration part 33 and duty ratio configuration part 34, the DA change-over circuit 17 that the magnitude of voltage of setting voltage configuration part 33 is transferred to LED drive unit 10 will be applied, simultaneously, the duty ratio transfer of data that duty ratio configuration part 34 is set

forms circuit

24,25,26 to the PWM waveform.This setting voltage value and setting duty ratio are to be specified by microcomputer 32.That is to say magnitude of voltage and duty ratio that microcomputer identification sets.

Microcomputer 32 is judged whether brightness and colourity have and is reached predefined desired value, when reaching desired value, set the magnitude of voltage that applies this time and duty ratio to be write by storing value and apply store voltages register 11,12,13 and duty

ratio memory register

21,22,23 with bus 14.That is to say that microcomputer 32 has as the function that data is write the storage data read-in unit that applies store voltages register 11,12,13 and duty

ratio memory register

21,22,23.

Now utilize Fig. 4 to describe in detail and apply magnitude of voltage (minimum luminous voltage) recording processing by what 30 pairs of usefulness of all kinds of driving voltage setting device applied that store voltages register 11,12,13 carried out, and to duty

ratio memory register

21,22, the 23 duty ratio data recording and processing of being carried out.

If the processing of driving voltage device 30 beginning step ST10, the then duty ratio of setting duty ratio configuration part 34 in following step ST11.Because of Fig. 4 is the processing that applies magnitude of voltage of bestowing red LED for setting, thus the conducting duty ratio of red LED is set at maximum, and the conducting duty ratio of green and blue led is set at 0.That is to say, the conducting duty ratio is formed circuit 24 for maximum data offer the PWM waveform, and be that 0 data offer the PWM waveform and

form circuit

25,26 the conducting duty ratio.At step ST12, microcomputer 32 target setting brightness.

At step ST13, apply magnitude of voltage configuration part 33 setting minimums and apply magnitude of voltage Vmin (as 1.5V), voltage variable circuit 18 will become this setting voltage after-applied to LED unit 20 by the voltage transitions that circuit for generating source voltage 19 produces.This time is because of only form the pwm signal of circuit 24 output conducting duty ratio maximums from the PWM waveform of redness usefulness, so but only have red LED to be in luminance.

At step ST14, microcomputer 32 judges that whether mensuration brightness by brightness/chroma meter 31 gained is greater than object brightness, then move on to step ST15 if be less than or equal to object brightness, with the setting that applies magnitude of voltage configuration part 33 apply voltage increase the k component (as, carry out the judgement of step ST14 after 0.1V) once again.

If obtain positive result at step ST14, then this is expressed as and obtains to expect that the required minimal voltage of brightness is just putting on red LED, so move on to step ST16, microcomputer 32 will be executed the magnitude of voltage of setting as magnitude of voltage configuration part 33 at present and write R with applying magnitude of voltage memory register 11.Thus, R has stored to making red LED obtain the minimum luminous voltage value of expectation brightness with applying magnitude of voltage memory register 11.

At following step ST17, microcomputer 32 judges whether mensuration brightness is consistent with object brightness, moves on to step ST18 when inconsistent, and the conducting duty ratio that duty ratio configuration part 32 is set reduces to return step ST17 behind the r component.

If obtain positive result at step ST17, then this expression can be made red LED luminous with expectation brightness by the pwm signal that present duty ratio configuration part 34 sets duty ratio, so move on to step ST19, the magnitude of voltage that microcomputer 32 is set present duty ratio configuration part 34 writes R with applying store voltages register 11.Thus, R has stored with duty ratio memory register 21 and has made red LED obtain the duty ratio data of expectation brightness.

In other words, it is after step ST14 sets the minimum that can obtain object brightness to step ST16 and applies voltage that this described step ST17 be can be said to the processing of step ST19, carries out more detailed brilliance control by pwm signal and sets the duty ratio that is used near object brightness.Driving voltage setting device 30 finishes R is write processing with applying store voltages register 11 and the R data with duty ratio memory register 21 at following step ST20.

Yet, though here just write to handle and describe with applying store voltages register 11 and R data with duty ratio memory register 21 for R, G with and B use and apply

store voltages register

12,13 and G to use with B also be to carry out with identical order with the processing that writes of the data of duty

ratio memory register

22,23.

Secondly, will serve as to obtain the order that the duty ratio of all kinds of expectation white balance is stored in

register

21,22,23 with Fig. 5 explanation.

If beginning the white balance adjustment at step ST30, handles driving voltage setting device 30, then make LED of all kinds luminous successively with the pwm signal of the conducting duty ratio that applies voltage and 21,22,23 storages of duty ratio memory register that applies store voltages register 11,12,13 storage at following step ST31, simultaneously, drive LCD panel 40 with LCD drive circuit (not shown).

In fact, LED drive unit 10 will apply the LED of all kinds that store voltages register 11,12,13 stored and put on LED unit 20 successively with voltage, and to form the LED usefulness pwm signal of all kinds of duty ratio corresponding memory registers 21,22,23 duty ratios of store synchronous with it and the PWM waveform forms

circuit

24,25,26.

That is to say that the LED that carries out actual field-sequential mode at step ST31 drives and the LCD driving.Here will be stored in the data that apply store voltages register 11,12,13 and duty

ratio memory register

21,22,23 and be assumed to the data that set as Fig. 4.

Measure the colourity that shows look at step ST32 with brightness/chroma meter 31.Be shown in chrominance space if should measure chromatic diagram, then as shown in Figure 6.Then, calculate the poor of the desired value of measuring colourity and white balance by microcomputer 32, change the duty ratio of setting duty ratio configuration part 34 and offer of all kinds with PWM

waveform formation circuit

24,25,26 according to this difference.Here, constituting of microcomputer 32: can read the duty ratio of using of all kinds that duty

ratio memory register

21,22,23 is stored, and specify in the duty ratio of using of all kinds that duty ratio configuration part 34 is set according to the difference with duty ratio and the desired value of measuring colourity and white balance of all kinds of being read.Thus, make the value that can obtain the target white balance that becomes with duty ratio of all kinds.

Particularly, at first judge at step ST33 whether the Y coordinate of measuring colourity is positioned at white permissible range shown in Figure 6, judge at step ST34 whether the X coordinate of measuring colourity is positioned at white permissible range shown in Figure 6 simultaneously.When in any one step of step ST33 or step ST34, obtaining negative decision, move on to step ST35, change duty ratio by duty ratio configuration part 34.

The change of this duty ratio is to consider which how many components of deviation in driction is measured value carry out to respect to the impact point of white balance.In this embodiment, microcomputer 32 carries out pro rate by the direction and the departure that will depart from R, G, B colourity, thereby sets the duty ratio that next will offer the usefulness of all kinds of LED drive unit 10.

Be the example Y coordinate of considering measured value with Fig. 6 with respect to impact point to depart from than general orientation and the X coordinate of measured value with respect to impact point the situation during to less deviation in driction.Therefore here, the distribution on the chrominance space of R, G, B LED of all kinds generally is as shown in Figure 6, reduces for the Y component that makes white balance and the X component increases with near impact point, for example can increase red with the conducting duty ratio and reduce green conducting duty ratio.

Can find out the duty ratio of using of all kinds that can obtain the target white balance with less set point number by the setting of carrying out next conducting duty ratio with above-mentioned pro rate.

If driving voltage device 30 all obtains positive result at step ST33 and step ST34, then this expression white balance has entered in the white permissible range, so move on to step ST36, the redness that present duty ratio configuration part 34 is set with, green with, bluely store corresponding duty

ratio memory register

21,22,23 into duty ratio, finish this white balance adjustment at following step ST37 and handle.

As mentioned above, driving voltage device 30 is from obtaining to expect the duty ratio of brightness independently at R, G, B LED of all kinds, measure and show look actual white balance, of all kinds seek the duty ratio that can obtain to expect white balance in duty ratio according to this measurement result changing, the duty

ratio memory register

21,22,23 that stores correspondence with duty ratio into of all kinds when obtaining the expectation white balance.

As mentioned above, driving voltage device 30 is because of can of all kindsly recently adjusting white balance with duty by changing, so can easily carry out trickle adjustment to white balance.And, be stored in

rewritable register

21,22,23 by the duty ratio that will be used to adjust white balance, can when measuring the actual colourity of product, write the distinctive duty ratio of each product, therefore, even each product variant white balance that also can in each product, obtain expectation on LED, light guide plate and LCD panel.

Next, utilize Fig. 7 that the action of LED drive unit 10 in this embodiment is described.LED drive unit 10 is LR between the red LED light emission period at first, select circuit 15 in the output that applies store voltages register 11,12,13, to select the R output that applies store voltages register 11 by register, after the corresponding R of voltage variable circuit 18 formation was with the 2.2V voltage that applies the output of store voltages register, the voltage with this 2.2V shown in Fig. 7 (a) offered LED unit 20.

In addition, when if the luminous timing signal TR of red LED time t2 in the LR between the red LED light emission period rises, then output to transistor 27 by R is formed circuit 24 with the duty ratio pwm signal of duty ratio memory register 21 storage from the PWM waveform, red LED can be with luminous to brightness that should pwm signal.Be close to time t3, if the luminous timing signal TR of red LED descends, then when PWM waveform formation circuit 24 stopped to export, register selected circuit 15 to select G to replace the R output that applies store voltages register 11 with the output that applies store voltages register 12.

Thus, LED drive unit 10 forms the 3.3V voltage of corresponding G with the data that apply voltage register 12 by voltage variable circuit 18 in the LG between the green LED light emission period, and this 3.3V voltage is offered LED unit 20.In addition, when if the luminous timing signal TG of green LED time t4 in the LG between the green LED light emission period rises, then output to transistor 28 by G is formed circuit 25 with the duty ratio PWN signal of duty ratio memory register 22 storage from the PWM waveform, green LED can be with luminous to brightness that should pwm signal.Be close to time t5, if the luminous timing signal TG of green LED descends, when then PWM waveform formation circuit 25 stopped to export, register selected circuit 15 to select B to replace the G output that applies store voltages register 12 with the output that applies store voltages register 13.

Thus, LED drive unit 10 forms the 3.4V voltage of corresponding B with the data that apply store voltages register 13 by voltage variable circuit 18 in the LB between the blue led light emission period, and this 3.4V voltage is offered LED unit 20.In addition, when if the luminous timing signal TB of blue led time t6 in the LB between the blue led light emission period rises, then output to transistor 29 by B is formed circuit 26 with the duty ratio PWN signal of duty ratio memory register 23 storage from the PWM waveform, blue led can be with luminous to brightness that should pwm signal.Be close to time t7, if the luminous timing signal TB of blue led descends, when then the output of PWM waveform formation circuit 26 stopped, register selected circuit 15 to select R to replace the B output that applies store voltages register 13 with the output that applies store voltages register 11.

Below similarly by repeating between the red LED light emission period between LR, green LED light emission period LB between LG and blue led light emission period, can be with the field-sequential mode display color.

In addition, in this embodiment, be to select LR, LG and LB between LED light emission period of all kinds with 5mS approximately, and selected of all kinds with 2000 μ S approximately with between the pwm signal period of output.And the pwm signal waveform is to be unit period with 50 μ S, and the duty ratio in this unit period is stored in duty ratio memory register 21～23.In addition in this embodiment, each duty ratio memory register 21～23 can be stored the duty ratio of 8 (=256 kinds).

Therefore,, the driving voltage of LED of all kinds is stored in applies store voltages register 11,12,13, by driving LED of all kinds, thereby realize to reduce the LED drive unit 10 of current sinking with driving voltage independently according to the present embodiment.

And, by being set by storing value, the data that apply

voltage register

11,12,13 rewrite with bus 14, even thereby have minimum luminous voltage (just because of the difference of product at the LED of actual setting, apply voltage for obtaining the needed minimum of expectation brightness) difference the time, also can appropriate change be stored in the voltage that applies

voltage register

11,12,13 and come the difference between should product.So, for example after product is finished, promptly can easily set LED of all kinds driving voltage separately, and this driving voltage can obtain the desired brightness of this product and can suppress current sinking.

In addition, by LED of all kinds being carried out PWM control time, to be stored in independently in the duty

ratio memory register

21,22,23 by LED of all kinds for the duty ratio of carrying out PWM control, can carry out independent control to the brightness of LED of all kinds with the pwm signal that has independently duty ratio of all kinds, therefore be carried out the brightness adjustment of trickleer LED of all kinds.

In addition, by voltage variable circuit 18 is set, the voltage transitions that a circuit for generating source voltage 19 is produced becomes the driving voltage of LED of all kinds, thus, compare with the situation of the circuit for generating source voltage of the driving voltage that a plurality of generations LED of all kinds is set, can simplified structure.

(embodiment 2)

Fig. 8 represents the structure of the LED drive unit 50 of embodiment of the present invention 2, and part corresponding with Fig. 1 in Fig. 8 indicates same numeral.LED drive unit 50 is except the LED connected mode in LED unit 51, and the LED drive unit 10 of all the other structures and embodiment 1 is identical.

In the present embodiment, the red LED among the red, green, blue LED of all kinds is connected mutually.Thus, can reduce electric power system number, make the luminous needed current sinking of red LED thereby be reduced to red LED.

That is to say that the present embodiment is conceived to the following fact: making red LED almost is to make green and blue led with half of the luminous required driving voltage of expectation brightness with expectation brightness luminous required driving voltage.

Expecting thus can be to make two red LED of series connection luminous with the voltage voltage much at one that puts on green and blue led.That is to say that if as the present embodiment red LED is connected, circuit for generating source voltage 19 does not just need to produce king-sized voltage, can effectively reduce current sinking.

Fig. 9 represents the action of the LED drive unit 50 of the present embodiment.The place that its above-mentioned Fig. 7 that neutralizes is different only is shown in Fig. 9 (a), for the red LED that makes series connection changes 4.4V with the luminous voltage that LR offers LED unit 20 between the red LED light emission period of expectation brightness into by 2.2V.The voltage of this 4.4V is the interior voltage of battery voltage range of general portable type electronic product.

Therefore,, the red LED among the red, green, blue LED of all kinds is connected mutually, can realize except embodiment 1 resulting effect, can also further reducing the LED drive unit 50 of current sinking according to the structure of the present embodiment.

(other embodiment)

Yet, for simplifying accompanying drawing and explanation, constitute

LED unit

20 and 51 with two red LED, two blue leds and a green LED respectively, but the quantity of LED of all kinds is not limited to this in the above-described embodiment.

And, do not limit for the quantity of

LED unit

20 and 51, can set driving voltage and the duty ratio of LED of all kinds independently in each LED unit and be stored in the memory.

In addition, can apply variable voltage independently to homochromy LED, homochromy LED is measured its brightness independently, apply store voltages register 11～13 and will the minimum when homochromy LED detects the brightness that is greater than or equal to desired value respectively apply to be stored in after magnitude of voltage is set at driving voltage value independently, and drive each LED with this magnitude of voltage.Thus, be used in promptly between homochromy LED that to obtain the required driving voltage of expectation brightness variant, also can therefore can reduce current sinking further so that minimum driving voltage that should difference is driven homochromy LED respectively.

Similarly, can control with the different pwm signal of duty ratio respectively for homochromy LED, also can be stored in independently in the duty ratio memory register 21～23, and each LED be carried out PWM control with this duty ratio with detect the duty ratio of expectation during brightness respectively at homochromy LED.Thus, even be that to obtain the needed duty ratio of expectation brightness between homochromy LED variant, also can be so that duty ratio that should difference be carried out PWN control to each LED, thus can carry out trickleer brightness adjustment and white balance adjustment.

In addition, also can be applied in the driving of a plurality of White LEDs of combination and colour filter with each White LED of the liquid crystal indicator of display color.That is to say,, and make minimum luminous voltage and the duty ratio of a plurality of memory stores, then can obtain the effect identical with above-mentioned embodiment to difference that should characteristic if respectively a plurality of memories of corresponding each White LED are set.

In addition, also can set in the present invention and be stored in the value that applies store voltages register 11～13 and/or duty ratio memory register 21～23 according to the configuration of LED.Thus, can easily carry out the brightness adjustment corresponding with the allocation position of LED.For example, in the liquid crystal indicator of a plurality of White LEDs being used for colour filter mode backlight, if have in the time of to make near the brightness in picture marginal portion be higher than near requiring of the brightness of picture central authorities, make corresponding picture marginal portion White LED apply magnitude of voltage and conducting duty ratio greater than the White LED of corresponding picture middle body apply magnitude of voltage and conducting duty ratio, just can easily carry out the brightness adjustment corresponding with the allocation position of LED.

In addition, though in the above-described embodiment the situation that LED drive unit of the present invention is applied in the liquid crystal indicator of field-sequential mode is described, but LED drive unit of the present invention is not limited to this, also can be widely used in the display unit of using R, G, B three-color LED display color.

The present invention is not limited to above-mentioned embodiment, also can carry out all changes and be implemented.

A structure that embodiment adopted of LED drive unit of the present invention is to have: the supply voltage production part; Apply the store voltages parts, storage be arranged on display unit red, green, blue LED of all kinds each LED independently apply magnitude of voltage; Apply voltage and form parts, the voltage transitions that the supply voltage production part is produced becomes to be stored in and applies applying magnitude of voltage and being applied to LED of all kinds of store voltages parts.

According to this structure, because according to the magnitude of voltage that applies the store voltages component stores, in LED of all kinds, be applied with following driving voltage, promptly, apply identical driving voltage to homochromy, and different colours is applied different driving voltages, so compare with the situation that LED of all kinds is applied same drive voltage, can reduce current sinking.

A structure that embodiment adopted of LED drive unit of the present invention is: the described store voltages parts that apply are made of writeable memory, this memory be used to import the voltage value signal line that applies that will store and be connected.

According to this structure, because can change at any time be stored in the LED of all kinds that applies the store voltages parts independently apply magnitude of voltage, even so make minimum luminous voltage (just because of the difference of product at the LED of actual setting, apply voltage for obtaining the needed minimum of expectation brightness) when having difference, also can appropriate change be stored in the voltage that applies the store voltages parts and come the difference between should product.So, for example after product is finished, promptly can easily set LED of all kinds driving voltage separately, and this driving voltage can obtain the desired brightness of this product and can suppress current sinking.

An embodiment of LED drive unit of the present invention is: applying the structure that the store voltages parts are adopted is also to store at homochromy LED independently to apply magnitude of voltage.

According to this structure, though between homochromy LED for the required driving voltage that obtains expectation brightness has difference, also can therefore can reduce current sinking further with to minimum driving voltage driving LED that should difference.

A structure that embodiment adopted of LED drive unit of the present invention is to have: the duty ratio memory unit, be made of writeable memory, LED of all kinds stores the duty ratio of the pwm signal that the brightness between the light emission period of each LED of LED of all kinds is finely tuned independently; The PWM control assembly, the pwm signal by LED of all kinds forms the duty ratio of being stored based on the duty ratio memory unit independently carries out PWM control independently to LED of all kinds; Holding wire is connected with the duty ratio memory unit, is used for duty ratio input duty cycle memory unit.

According to this structure, can carry out independent control to the brightness of LED of all kinds with the pwm signal that has independently duty ratio of all kinds, therefore can carry out the brightness adjustment of trickleer LED of all kinds.In addition, because of changing the independently duty ratio of all kinds that is stored in the duty ratio memory unit at any time, when even the brightness of the LED that is provided with in reality or light guide plate and liquid crystal panel etc. are variant, also the duty ratio of difference that can the be corresponding above-mentioned display brightness that can obtain to expect by holding wire suitably writes the duty ratio memory unit.In addition, because of can independently changing duty ratio, so can carry out the white balance adjustment easily by LED of all kinds.

A structure that embodiment adopted of LED drive unit of the present invention is: the magnitude of voltage that applies that applies store voltages component stores LED of all kinds, this applies magnitude of voltage can make LED of all kinds luminous with the brightness that is greater than or equal to expectation brightness, and the duty ratio storage component stores is to make the duty ratio of the luminosity of LED of all kinds near described expectation brightness.

According to this structure, can when reducing current sinking, make the brightness of LED of all kinds reach desired value.

A structure that embodiment adopted of LED drive unit of the present invention is: the duty ratio memory unit is also stored independently duty ratio for homochromy LED.

According to this structure,, also can in each LED, store duty ratio that should difference, thereby can carry out trickleer brightness adjustment even variant for obtaining the needed duty ratio of expectation brightness between homochromy LED.

A structure that embodiment adopted of LED drive unit of the present invention is: the red LED among the red, green, blue LED of all kinds is connected mutually.

According to this structure,, therefore can be reduced to the required current sinking that makes red LED luminous because of producing the low red LED driving voltage of minimum luminous voltage expeditiously.Here, it almost is to make green and blue led half the fact with the luminous required driving voltage of expectation brightness with the luminous required driving voltage of expectation brightness that the present inventor is conceived to make red LED, and expecting thus can be to make two red LED of connecting luminous with the voltage voltage much at one that puts on green and blue led.That is to say,, can not make the supply voltage production part unnecessary voltage of generation and reduce current sinking according to said structure.

A structure that embodiment adopted of LED drive unit of the present invention is: the supply voltage production part produces single magnitude of voltage, apply voltage formation parts and have D/A converter and voltage variable parts, D/A converter is used for carrying out digital-to-analogue conversion to applying store voltages magnitude of voltage that parts are deposited, and the voltage variable parts are used for converting the single magnitude of voltage that the supply voltage production part produces to be equivalent to through the analogue value of D/A converter conversion voltage.

According to this structure, independently apply voltage because of being stored in the LED of all kinds that applies the store voltages parts with the voltage formation that the common supply voltage production part of LED of all kinds produces, so compare with the situation of the supply voltage production part that corresponding LED of all kinds is set, can simplified construction.

A structure that embodiment adopted of driving voltage setting device of the present invention is to have: the voltage application portion part applies variable voltage to each LED of red, green, blue LED of all kinds; Detection part, the brightness of the LED of all kinds when detection voltage application portion part applies voltage; When data read-in unit, detection part detect the brightness that is greater than or equal to desired value at each LED of LED of all kinds, the minimum that is applied to each LED of LED of all kinds is applied the driving voltage value write memory of magnitude of voltage as LED of all kinds.

According to this structure, can be applied to the minimum driving voltage of LED of all kinds by independent setting of all kinds, and this minimum driving voltage of all kinds can make LED of all kinds luminous with the brightness that is greater than or equal to desired value.

An embodiment of LED driving method of the present invention is: be determined at the minimum driving voltage that red, green, blue LED of all kinds can obtain expectation brightness in advance, the driving voltage of each LED of this LED of all kinds is stored in applies the store voltages parts, LED of all kinds is applied described stored voltage value.

According to this method,,, can reduce current sinking so compare with the situation that LED of all kinds is applied identical driving voltage because of applying independently driving voltage to LED of all kinds according to the magnitude of voltage that applies the store voltages component stores.

An embodiment of LED driving method of the present invention is: apply under the state of described minimum driving voltage at each LED to LED of all kinds, the pwm signals different with each LED duty ratio of LED of all kinds carry out PWM control to LED of all kinds.

According to this method, can carry out trickle brightness adjustment to LED of all kinds.

As mentioned above, according to the present invention, when driving red, green, blue three-color LED display color, can effectively reduce current sinking.In addition, thus the difference that can eliminate each LED characteristic carry out consistent color and show.

Patent application 2003-98486, patent application 2003-98487 and patent application 2003-98489 that the application submitted to based on April 1st, 2003.Its content all is contained among the application.

The feasibility of utilizing on the industry of the present invention is that the present invention is applicable to for example liquid crystal display dress Put etc.

Claims

1. light emitting diode drive device has:

The supply voltage production part;

Apply the store voltages parts,, will apply magnitude of voltage for the required minimum of brightness that obtains being greater than or equal to expectation brightness independently by light-emitting diode of all kinds and store as digital value for the red, green, blue light-emitting diode of all kinds that is arranged in the display unit;

2. light emitting diode drive device as claimed in claim 1, wherein, the described store voltages component stores that applies also is a digital value independently for homochromy light-emitting diode.

3. light emitting diode drive device as claimed in claim 1, wherein, described duty ratio storage component stores also is a duty ratio independently for homochromy light-emitting diode.

4. light emitting diode drive device as claimed in claim 1, wherein, the red light emitting diodes in the light-emitting diode of all kinds of red, green, blue is connected mutually.

5. light emitting diode drive device as claimed in claim 1 has:

Detection part detects the brightness of described red, green, blue light-emitting diode of all kinds;

The data read-in unit when described detection part detects the described expectation brightness of being greater than or equal to of light-emitting diode of all kinds respectively, writes the described store voltages parts that apply with the digital value that puts on light-emitting diode of all kinds respectively.

6. light emitting diode drive device as claimed in claim 5, also has the duty ratio read-in unit, in light-emitting diode of all kinds, detect expectation respectively during brightness at described detection part, the duty ratio separately of light-emitting diode of all kinds is write described duty ratio memory unit.

7. light emitting diode drive device as claimed in claim 5, wherein

The described voltage formation parts that apply also apply variable voltage independently for homochromy light-emitting diode;

Described detection part is for homochromy light-emitting diode also sensed luminance independently;

Described data read-in unit also will detect at each light-emitting diode homochromy light-emitting diode and be greater than or equal to the apply magnitude of voltage of expectation during brightness and write the described store voltages parts that apply independently as digital value.

8. light emitting diode drive device as claimed in claim 6, wherein

Described pulse width modulation controlled parts are also controlled with the variant pulse-width signal of duty ratio for homochromy light-emitting diode;

Described duty ratio read-in unit also writes described duty ratio memory unit with the duty ratio when each light-emitting diode detects expectation brightness independently for homochromy light-emitting diode.