CN103081565B - For driving the method for at least one light emitting diode and for implementing the illuminator of the method - Google Patents

Abstract

One is used for driving at least one light emitting diode (4a, 4b, method 4c), at least one of which light emitting diode (4a, 4b, 4c) at least drive by means of pulse density modulated in the range of some, described pulse density modulated arranges according to light energy expected value, especially degree of dimming in default interval duration (T) quantity (n_dim) of identical current impulse (p_red).Illuminator (1) is configured with at least one light emitting diode (4a, 4b, 4c) and at least one driver (3a, 3b, 3c) fed at least one light emitting diode (4a, 4b, 4c), and wherein illuminator (1) is designed as implementing described method.

Description

For driving the method for at least one light emitting diode and for implementing the illuminator of the method

Technical field

The present invention relates to a kind of for driving at least one light emitting diode or sending out at least one The method of optical diode feed.The invention still further relates to a kind of illuminator, described illuminator has At least one light emitting diode and driving at least one fed at least one light emitting diode Dynamic device.

Background technology

In order to regulate the brightness of light emitting diode (LED) in wide scope, drive LED's The change (levels of current modulation) of LED current is inappropriate, because at low and high electricity In the case of stream the brightness of LED can deviate from other respects good meet linear electric current/ Brightness ratio, and LED can be compromised in addition.Therefore, LED in most cases by means of Pulse width modulation (PWM) drives, and wherein LED is at default on-time t1 Drive with constant electric current I in (also referred to as turn-on time) and hereafter continue in default disconnection Time t2 switches to no power in (also referred to as turn-off time).Here, have cycle duration Pulse duty factor t1/T of T=(t1+t2) is approximately corresponding to expect degree of dimming.If will hold in the cycle Continuous time T=(t1+t2) selects long (typically longer than 10ms), then described PWM Light-dimming method is perceived by human viewer by flicker.In on-time t1 upper integral Current intensity or electric current I be limited in cycle T the light energy or the light quantity that produce.

PWM excitation or PWM light-dimming method propose to want dynamically for the current source used Ask.In ideal conditions, in on-time t1, provide constant electric current, and Electric current is not had to flow through (it is to say, handoff procedure is negligible during break time t2 Ground Rapid Implementation).Only in this way, pulse duty factor t1/ (t1+t2) just directly with the having of LED Effect brightness or intensity are proportional.But, this has big rise-time constant t_PSU at current source (it is to say, needed for current source with by its current value from disconnect state rise to rated value The persistent period of preset ratio) and low degree of dimming in the case of be no longer guaranteed, to such an extent as to because of This dimming characteristic deviates from linear characteristic.

In (color) mixing, there is required different strength ratio or single on-time The light of the LED of the different colours of (such as t1i, i represent different LED) is so as to arrange In the case of specific tertiary colour coordinate, depend on the circumstances the intensity between needing different LED Ratio or brightness ratio are maintained at specific value.But, at degree of dimming (present current level and maximum electricity The ratio of intensity of flow) too low in the case of, the such as brightness between the LED of two different colours More proportional to t1a/t1b than no longer, and effectively mixed color changes significantly.

Therefore, mainly by the speed of current source or rise-time constant t_PSU and Cycle duration T determines actually available degree of dimming.Therefore, in practice, it is not less than The cycle duration T of about 0.1ms, this disadvantageously limit degree of dimming.Therefore, by means of arteries and veins Rush the light modulation that width modulated carries out and be especially positioned at 10ms at cycle duration T T > 0.1ms scope Use in the case of Nei.In such cycle duration T, it is no longer able to perceive flicker.

Process a kind of probability of described shortcoming and be to use quick current source, but described electric current Source is relatively costly.Flicker in the case of low degree of dimming and/or in the situation of low degree of dimming Under color error ratio also be able to be accepted, but this is regarded by the user as being disadvantageous.

Summary of the invention

It is an object of the invention to, the shortcoming getting rid of prior art at least in part, and especially for Low degree of dimming improves the photocurrent versus light intensity of at least one light emitting diode, the most more strongly by described Photocurrent versus light intensity linearisation.

Described purpose realizes according to the feature described in embodiments herein.Enable in particular to follow-up Explanation in draw preferred form of implementation.

Described purpose by a kind of for driving the method for at least one light emitting diode to realize, its In at least one light emitting diode at least drive by means of pulse density modulated in the range of some, Wherein according to the expected value (" light of the light energy for be radiated by least one light emitting diode Energy expectation value "), especially degree of dimming identical electric current is set in default interval duration The quantity of pulse.Therefore, in other words, the quantity of current impulse can be according to desired light energy Expected value changes, and it is next close to described expectation to enable in particular to the quantity by producing minimum deflection Value.

Set luminous energy can be specifically improved in a straightforward manner by Novel pulse density modulation Linear relationship between amount expected value and the actual value actually reached, more precisely, the most right For low degree of dimming.Here, pulse density modulated benefit from the fact that due to current impulse consistent Property and the most known every current impulse are by light energy produced by least one light emitting diode, more Even if exactly not knowing the shape of current impulse.In other words, degree of dimming accurately can limit ground Change step by step and can seriously reduce non-linear.Enable in particular to be significantly reduced to the light energy phase Prestige value, especially expectation degree of dimming and actual degree of dimming be correlated with light energy actual value it Between relative error.Step by step property with remaining non-linear can be by the size of current impulse or connect Persistent period is configured simply.Pulse density modulated also is able to should by current source at a slow speed With.

Degree of dimming enables in particular to be considered as about for feeding at least one light emitting diode Big current value or the brightness value of light that radiated by least one light emitting diode proportional Light energy value, current value and/or proportional brightness value.But, light energy expected value also is able to Including other parameters, such as electrical power.

One design is, described method includes especially in higher degree of dimming or towards higher Degree of dimming in the case of pulse width modulation (in described pulse width modulation especially in accordance with Desired degree of dimming arranges the on-time of current impulse) and especially in relatively low degree of dimming Or switch between the pulse density modulated in the case of relatively low degree of dimming.Thus can Enough different working ranges that mode of operation is matched with light emitting diode individually, are especially matched with Different dimming scopes.Pulse width modulation for such as 10% or more the highest degree of dimming Application can realize encouraging at least one light source there or at least one light particularly simplely Source feeds, more precisely, until the state not dimmed.

Especially, it is possible to switch between pulse width modulation and pulse density modulated so that Pulse width modulation reaches the most roughly the same with pulse density modulated on relevant switching point Light intensity, light energy, brightness etc. and/or identical precision.

Another design is, when up to or over the current impulse corresponding to pulse width modulation The degree of dimming of the shortest on-time time implement switching, current impulse is held described short circuit is logical Its rated current is reached in the continuous time.Therefore, enable in particular to apply pulse on described degree of dimming Width modulated, and under described degree of dimming, apply pulse density modulated.Utilize at this: when not When reaching the rated current of relevant single current impulse again, although absolute deviation diminishes, but Linear relationship between expectation degree of dimming and actual degree of dimming is in the case of pulse width modulation Notable variation.Otherwise show, application pulse density modulated the most multiple, relatively short or relatively Little current impulse improves linear relationship.

Another design is, has for the current source fed at least one light emitting diode Rise time constant, described rise-time constant compared with the cycle duration of pulse width modulation more Short, especially for 0.01 times or 0.1 times of cycle duration of pulse width modulation.Thus, Can apply for the wide scope of degree of dimming and there is the best linear simple and nothing The pulse width modulation of level.Rise-time constant is the cycle duration of pulse width modulation The situation of 0.01 times to 0.1 times has an advantage that therefore can be logical in cycle duration Stable state is reached after being equivalent to the persistent period of about three rise-time constants in the case of Chang.

Rise-time constant enables in particular to be needed for current source to be rated current 0.5 times to reach Current value, or preferably to reach to be equivalent to the current value (1-1/e) of rated current 0.63 times Persistent period.

Another design is, described method is included in the pulse width in the case of higher degree of dimming Switch between pulse density modulated in the case of degree modulation and relatively low degree of dimming.Thus Go out following advantage: at least one light emitting diode can be driven with following degree of dimming, in described light modulation In the case of degree, (applying continuously) levels of current of levels of current modulation is positioned under its lower threshold value. Utilizing at this: in order to without damage drive, multiple light emitting diodes need the electricity with at least lower threshold value Flow horizontal feeds.But, it is also possible to the value in levels of current or degree of dimming is higher In the case of implement pulse density modulated, wherein compared with the modulation of pulse density modulated and levels of current Realize higher precision.

Another design is, during the pulse persistance of at least one current impulse of pulse density modulated Between or the on-time less than or equal to for feeding at least one light emitting diode Current source, the rise-time constant of such as driver.In the situation that the on-time is the most longer Under, limit the quantity of the pulse in each interval or cycle significantly, and then limit degree of dimming significantly (discrete) quantity.

Another design is, when the connection of at least one current impulse of pulse density modulated continues Between be positioned at the big of the rise-time constant for the current source fed at least one light emitting diode Between about 0.1 times and about 10 times of rise-time constant, particular on rise-time constant Between 0.3 times and 1.5 times of rise-time constant.In the situation that the on-time is the most longer Under, limit the quantity of the pulse in each interval or cycle significantly, and then limit degree of dimming significantly (discrete) quantity.In on-time or the feelings of the most shorter on-time Under condition, switch needs quick shutter, and this can result in high consuming and High-frequency Interference radiation.

Yet another design scheme is, interval duration is between about 1 μ s and about 10ms, especially It is between about 0.5ms and about 10ms, including end value.

Another design is, has continuous print brightness or the light of at least one light emitting diode Implement switching at the switching point of energy, therefore, do not cause brightness step by switching.Therefore, right The transition between two kinds of excitation is will not notice that for observer.

Another design is, the time point in switching based at least one current impulse determines Quantity determines pulse duration of at least one current impulse of pulse density modulated and connects Persistent period.In other words, the electricity for the pulse density modulated switched is preset with first can determine The quantity of stream pulse, and in the case of learning the quantity of current impulse, determine described current impulse On-time or the pulse duration so that carry out transition as continuously as possible.Suitably Pulse duration such as can determine by means of suitable characteristic curve.As an alternative, pulse Persistent period can come by means of sensing system (such as optical sensor) and such as control loop It is configured so that carry out transition as continuously as possible.

The design of one alternative is, transition between pulse width modulation and pulse density modulated Time, pulse duration or the connection of the current impulse of predetermined pulse density modulation definitely continue Time and the quantity of current impulse is set so that as continuously as possible or with the least rank Leap row transition.Such as can in the case of the brightness learnt at transition point or light energy or By being produced by current impulse in the case of learn the light energy produced by current impulse Light energy is multiplied with the quantity of the current impulse as variable and determines the suitable number of current impulse Amount.

As an alternative, the quantity of the current impulse of pulse density modulated and pulse duration or connection Persistent period can determine as the modification of two values or best of breed.If desired, for joining Within the boundary value that at least one in number is preset.

Especially, the current impulse of the pulse density modulated of each cycle persistent period at transition point Quantity be the maximum quantity of current impulse.The number of current impulse is reduced by light modulation further Amount.Therefore, the maximum quantity of current impulse also correspond to can by pulse density modulated arrange bright Degree level or the quantity of luminance level.

Another design is, implements concurrently for the light emitting diode of many group different colours Described method.Each one or more light-emitting diodes can with same color in described group Pipe.Here, there is expectation tertiary colour coordinate by (mixing) light of LED radiation.Due to Excitation types is matched with individually different duties, it is possible to simplify and make tertiary colour coordinate meet For low degree of dimming, wherein said different duty especially can be by particularly degree of dimming The different scope of light energy expected value is distinguished.

Described purpose realizes also by a kind of illuminator, and described illuminator has at least one Light emitting diode and at least one driver of feeding at least one light emitting diode, wherein Illuminator is designed as implementing method as above.

Accompanying drawing explanation

Schematically illustrate in greater detail the present invention according to embodiment in following accompanying drawing.Here, be Visuality, element that is identical or that play phase same-action can be provided with identical reference.

Fig. 1 be shown for the current source of relatively slow speed, through at least one light emitting diode, Normalize to the electric current I and the time t with random time unit of the pulse width modulation of rated current Between the curve chart of dependency；

Fig. 2 be shown for relatively quick current source, through at least one light emitting diode, Normalize to the electric current I and the time t with random time unit of the pulse width modulation of rated current Between the curve chart of dependency；

Fig. 3 is shown for having the current source of the relatively slow speed of longer on-time, warp The electric current I of pulse width modulation that cross at least one light emitting diode, that normalize to rated current And the curve chart with the dependency between the time t of random time unit；

Fig. 4 is shown for having the current source of the relatively slow speed of shorter on-time, warp The electric current I of pulse width modulation that cross at least one light emitting diode, that normalize to rated current And the curve chart with the dependency between the time t of random time unit；

Fig. 5 is shown for being positioned at the connection of the current source on rise-time constant t_PSU when continuing Between, Fig. 4 has its pulse width modulation song together with the pulse density modulated of alternative Line chart；

Fig. 6 is shown for being positioned at the connection of the current source under rise-time constant t_PSU when continuing Between, pulse width modulation is together with the curve chart of pulse density modulated as an alternative；With

Fig. 7 illustrates the LED light device for implementing pulse density modulated.

Detailed description of the invention

Fig. 1 illustrate through one LED's or multiple LED (not shown), normalize to volume Determine electric current In=1, pulse width modulation electric current I and with the time t of random time unit between The curve chart of dependency, or rather for the current source of relatively slow speed for.One individually The PWM cycle of current impulse P or cycle duration T be about 10 unit of time at this. Cycle duration T enables in particular between 0.5ms and 10ms.The connection of current impulse P is held Continuous time t1 and break time t2 (=T-t1) has the expectation of just 5 unit of time Value, to such an extent as to corresponding to expecting expectation pulse duty factor t1/T or the t1/ (t1+t2) of degree of dimming It is 50% in the ideal case.

But, due to current source is (rising) that can not ignore of 0.5 unit of time at this Time constant t_PSU, actual (actual) degree of dimming is only 46%, this corresponding approximately to The relative error of 8%.Accordingly, because the inertia of current source, degree of dimming reduces about 4%.

Fig. 2 is shown for the relatively quick electric current with the t_PSU of about 0.1 unit of time Source, the curve chart that is similar to Fig. 1.Relative error accordingly, with respect to degree of dimming is little to negligible Disregard.

Curve chart that Fig. 3 is shown for the current source of relatively slow speed, that be similar to Fig. 1, its mid-term Hope that on-time t1 is eight unit of time now, corresponding to the expectation degree of dimming of 80%. But, actual (actual) degree of dimming is only 80%-4%=76%, and this is corresponding approximately to 5% Relative error.

Curve chart that Fig. 4 is shown for the current source of relatively slow speed, that be similar to Fig. 1, its mid-term Hope that on-time t1 is two unit of time now, corresponding to the expectation degree of dimming of 20%. But, actual (actual) degree of dimming is only 20%-4%=16%, and this is corresponding approximately to 20% Relative error.

If reaching rated current at I=1, then degree of dimming for above-mentioned example substantially The reason of reduction by 4% is the most constant shape at current impulse edge consistently.

If degree of dimming is reduced under 20%, then no longer reach rated current, and edge Become steeper.Absolute error is reduced under 4% by this, but improves relative error.

If the on-time t1 of a such as unit of time dims corresponding to the expectation of 10% Degree, then actual degree of dimming is 7%, this, corresponding to the deviation of 3%, but is corresponding to 30% Relative error.Similarly, 0.5 or 0.2 unit of time (expectation light modulation of 5% or 2% Degree) on-time t1 corresponding to 3% or 1% actual degree of dimming.Relevant is relative Error is 40% or 50%.

Fig. 5 illustrates that the curve chart similar with the curve chart of Fig. 4, described similar curve chart have band There are the pulse width modulation of the traditional type illustrated there of single current impulse P, described electricity Stream pulse has parameters described below: t1_min=1.9 unit of time (adjust by the expectation corresponding to 19% Luminosity), the actual degree of dimming of 15% and the relative error of 21%.T1_min is interpreted as individually The shortest on-time of current impulse P, current impulse is in the shortest described on-time The most still reach the rated value In=1 of electric current.

Additionally, Novel pulse density modulation (PZM) shown in broken lines.Pulse density modulated exists There is in the initial cycle duration T of 10 unit of time multiple " reduction " electric current arteries and veins Rushing p_red, described current impulse is not reaching to rated current In and thus reaches the steepest Edge.The cycle duration T-phase of pulse width modulation is when holding in the interval of pulse density modulated The continuous time.

Quantity n_dim of the current impulse p_red of the reduction in initial cycle duration T All it is chosen as with on-time t1_LLD or pulse width so that at " transition point " At t=t1_min, pulse width modulation has the identical phase with 21% with pulse density modulated To error, the identical actual degree of dimming of 15%.Therefore, the characteristic, outstanding of (multiple) LED It is light characteristic be identical at transition point t1_min, to such an extent as at transition point t1_min Two kinds of modulation types between conversion (such as PWM is for t1 > t1_min or for T1>=t1_min, and PZM is for t1≤t1_min or for t1<t1_min) for seeing Can not be perceived by brightness for the person of examining.

In shown example, the identical characteristic at transition point t1_min is passed through The current impulse of the reduction of n_dim=10 reaches, and described current impulse is respectively provided with pulse width Or on-time t1_LLD=t_PSU, and then there is current rating In of about 0.63 Levels of current I.

If especially the on-time t1 of the single current impulse P of pulse width modulation is less than T1_min, then therefore degree of dimming declines towards extremely low degree of dimming, the reduction of pulse density modulated The application of current impulse substantially improving between expectation degree of dimming and actual degree of dimming linear Relation.To this end, Fig. 6 illustrates when having on-time t1=0.95 < t1_min=0.5 1.9 Between traditional single PWM electric current of unit (being equivalent to the half of t1_min in Fig. 5) Pulse P, this corresponding to 6.2% actual degree of dimming and the relative error of 35%.Now, individually Current impulse P the most also reach about the 0.85% of rated current.

The current impulse p_red of the reduction of pulse density modulated is correspondingly reduced to The quantity of n_dim=0.5 10=5 draws the actual degree of dimming of the improvement of 7.6% and the improvement of 25% The electric current of the reduction shown in relative error, the shape of the current impulse of wherein said reduction and Fig. 5 Pulse p_red identical (i.e. degree of dimming is constant).Due to for n_dim > the electric current arteries and veins of the reduction of 1 The pulse frequency rushing p_red is higher than the single current impulse P in pulse width modulation, the most not Flicker can be perceived.

It is still possible that two different quantity n_dim of the current impulse p_red by reducing Substitute the PWM current impulse P applied up to now.Such as, by t1=0.4 time The single PWM current impulse P of unit (the expectation degree of dimming corresponding to 4%) is capable of The actual degree of dimming of 2% and the relative error of 50%.Fall at the n_dim=2 applying above-mentioned shape In the case of low current impulse p_red, show that the actual degree of dimming of 3% is relative with 25% by mistake Difference.In the case of the current impulse p_red of the reduction of application n_dim=3, draw 4.5% Actual degree of dimming and the relative error of only 13%.

Therefore, the line between expectation degree of dimming and actual degree of dimming or the brightness of (multiple) LED Sexual relationship can improve as follows, i.e. have single current impulse P for t1 > about t1_min Pulse width modulation rise when about t1_min and be switched to for the t1 < pulse of about t1_min Density modulation, wherein has one or many according to the pulse width modulation of the second pattern according to degree of dimming The current impulse p_red of individual reduction, and vice versa.

Generally, the on-time t1_LLD=t_PSU of the current impulse p_red of reduction can Determined in the requirement of transition point t1_min transition continuously by brightness or light energy, and Followed by the on-time t1_LLD of current impulse p_red reduced and/or optimal Quantity n_dim is come close to expectation degree of dimming.Here, launch from a LED or multiple LED Light quantity proportional to n_dim t1_LLD.

As from example it is seen that, the relative error in the case of low degree of dimming can be passed through Application pulse density modulated significantly decreases.Therefore, linear in the case of low degree of dimming Relation can raise significantly.

For multiple LED different types of, especially different colours, it is possible to be performed separately Pulse density modulated.The excitation of different types of LED enable in particular in a synchronous manner or with Collaborative mode is carried out.Especially, for different types of LED, interval duration energy It is enough identical.

Additionally, realize following advantage by pulse density modulated:

Even if-the most invisible flicker in the case of extremely low degree of dimming (0% < t/T < 10%).Even can Enough reach the degree of dimming less than 1% with sufficiently accurate linear relationship.

Time constant t_PSU of-current source can than in order to reach low degree of dimming (t1/T < 10%, especially Its < 2%) necessary to PWM on-time t1_LLD longer.

Even if-also be able to realize until less than 10% degree of dimming in the case of big time constant t_PSU The linearity light adjusting characteristic of (especially between 1% and 10%), this is particularly with color mixture control It is favourable.

Fig. 7 illustrates and sends out for the possible LED implementing pulse density modulated and especially said method Electro-optical device 1.LED light emission device 1 has grid interface 2, and described grid interface is at this illustratively It is that three drivers 3a, 3b, 3c power.Three drivers 3a, 3b, 3c are respectively luminous two Pole pipe 4a, 4b, 4c feed, described light emitting diode launch different colours light, such as red, Green or blue.Driver 3a, 3b, 3c can encourage and it according to said method respectively Light emitting diode 4a, 4b or the 4c being associated.Driver 3a, 3b, 3c can be the most collaborative, Make the excitation of described driver light emitting diode 4a, 4b or 4c associated there respectively so that Close to or arrange, especially regulate by light emitting diode 4a, 4b or 4c produce mixed light Desired tertiary colour coordinate.

Illuminator 1 can be such as lamp or luminaire.

Self-evident, the present invention is not limited to shown embodiment.

Such as can be advantageously for particularly effectively close expectation degree of dimming: t1_LLD<t_PSU。

Reference numerals list

1 LED light device

2 grid interface

3a driver

3b driver

3c driver

4a light emitting diode

4b light emitting diode

4c light emitting diode

I electric current

In rated current

T cycle duration

P current impulse

The t time

The t1 on-time

T2 break time

T1_min transition point

T_PSU rise-time constant

The current impulse that p_red reduces

The quantity of n_dim current impulse

The t1_LLD on-time

Claims (15)

1. the method being used for driving at least one light emitting diode (4a, 4b, 4c), wherein said At least one light emitting diode (4a, 4b, 4c) at least in the range of some by means of impulse density Modulation drives, and holds at default interval according to light energy expected value in described pulse density modulated The quantity (n_dim) of identical current impulse (p_red) was set in the continuous time (T),

Wherein said method is included in the pulse width modulation in the case of higher degree of dimming and relatively Switch between described pulse density modulated in the case of low degree of dimming, or

Wherein said method be included in the case of higher degree of dimming levels of current modulation and relatively Switch between described pulse density modulated in the case of low degree of dimming.

Method the most according to claim 1, wherein when up to or over corresponding to described During the degree of dimming of the shortest on-time (t1_min) of the current impulse of pulse width modulation, It is implemented in the pulse width modulation in the case of higher degree of dimming and the situation of relatively low degree of dimming Under described pulse density modulated between switching, the current impulse of described pulse width modulation is in institute Its rated current (In) is reached in stating the shortest on-time.

Method the most according to claim 1 and 2, is wherein used for as at least one luminescence described The current source of diode feed has a rise-time constant (t_PSU), described rise-time constant with The cycle duration of described pulse width modulation is compared shorter.

Method the most according to claim 1 and 2, wherein said pulse density modulated is at least The on-time (t1_LLD) of one described current impulse is less than or equal to for for described The rise-time constant (t_PSU) of the current source of at least one light emitting diode feed.

Method the most according to claim 1 and 2, wherein said pulse density modulated is at least The on-time (t1_LLD) of one described current impulse is positioned at for for described at least one 0.1 times of the rise-time constant (t_PSU) of the current source of individual light emitting diode feed with described Between 10 times of rise-time constant (t_PSU).

Method the most according to claim 1 and 2, wherein said interval duration (T) It is between 1 μ s and 10ms.

Method the most according to claim 1 and 2, wherein has at least one luminescence described Switching is implemented at the switching point of the continuous print brightness of diode.

Method the most according to claim 4, wherein has at least one luminescence two described Switching is implemented at the switching point of the continuous print brightness of pole pipe.

Method the most according to claim 8, at least the one of wherein said pulse density modulated The described on-time (t1_LLD) of individual described current impulse is based at least one electricity described The quantity (n_dim) that the time point in described switching of stream pulse determines determines.

Method the most according to claim 1 and 2, wherein sends out for many group different colours Described method is implemented concurrently, wherein by described luminous two for optical diode (4a, 4b, 4c) The light that pole pipe (4a, 4b, 4c) radiates has expectation tertiary colour coordinate.

11. methods according to claim 1, wherein hold at default interval according to degree of dimming The quantity (n_dim) of identical current impulse (p_red) was set in the continuous time (T).

12. methods according to claim 3, wherein said rise-time constant is described arteries and veins Rush 0.01 times to 0.1 times of cycle duration of width modulated.

13. methods according to claim 5, the wherein said on-time (t1_LLD) It is positioned at 0.3 times and described rise-time constant (t_PSU) of described rise-time constant (t_PSU) 1.5 times between.

14. methods according to claim 6, wherein said interval duration (T) is Between 0.5ms and 10ms.

15. illuminators (1), have at least one light emitting diode (4a, 4b, 4c) and use In feed for described at least one light emitting diode (4a, 4b, 4c) at least one driver (3a, 3b, 3c), wherein said illuminator (1) be designed as implement according to the claims it Method described in one.