CN105764204A - PWM light modulation method and device - Google Patents
PWM light modulation method and device Download PDFInfo
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Abstract
The invention provides a PWM light modulation method and device. A plurality of PWM periods are combined into a control signal, so as to achieve the control of the brightness of illumination equipment. After the above design is employed, the light modulation precision cannot be affected while the frequency of a PWM signal is improve. Through the change of a combined scheme, more light modulation levels can be obtained, thereby achieving higher light modulation precision and a more smooth and flexible light modulation effect.
Description
Technical field
The present invention relates to a kind of PWM light-dimming method and PWM light modulating device.
Background technology
Along with the development of the rapid technology of LED, increasing LED light source instead of traditional light source.It is known that LED has many advantages as light source, easily light modulation toning is one of great advantage of LED.Along with development and the popularization of Internet of Things and Smart Home, dimming light source demand is got more and more, and the prescription of light modulation is also more and more higher.So the light regulating technology of LED needs constantly progressive, the advantage of competence exertion self, comply with the development spring tide of Smart Home.
At present, the most frequently used LED dimming mode is PWM light modulation, and its principle is to utilize pwm signal that Buck/Boost type switching power circuit is controlled, the dutyfactor value according to pwm signal, the voltage x current value that output is corresponding.The switching frequency of Buck/Boost type Switching Power Supply is higher as shown in Figure 1, is typically between tens of Khz to hundreds of Khz.The frequency of PWM is typically in hundreds of between several Khz, is controlled the electric current on/off of Switching Power Supply first-harmonic by the High/Low of PWM level.The cycle of pwm signal is generally the integral multiple in switching power circuit cycle, because, if the part Δ t that the PWM pulsewidth PWMHIGH time increases as shown in Figure 1 is placed exactly in the LOW in one cycle of switching power circuit, increasing for output electric current of such PWM pulsewidth is exactly invalid, rear end exports to the electric current of LED unchanged, it is impossible to play the light modulation effect of reality.And consider the stationary problem of two signals, therefore in existing PWM control program effective light adjusting grade of PWM equal to switching power circuit frequency fbDivided by PWM frequency fp(Leff=fb/fp).
Due to the PWM above-mentioned operation principle controlled, just create a contradiction, if it is desired to increase light adjusting grade and just should reduce the frequency of pwm signal, but when PWM frequency is low, easily there is stroboscopic in LED light source, when LED light source being shot with picture pick-up device, can be appreciated that obvious ripple.Otherwise, the raising of PWM frequency, although described stroboscopic ripple problem can be reduced, but the negative effect brought is reduction of light adjusting grade number and then light modulation fineness meeting step-down, causes brightness flop in dimming process smooth not, visually even can feel light source scintillation.
Summary of the invention
The invention aims to solve the problems referred to above, it is provided that a kind of dimming effect more smoothes out soft PWM light-dimming method, PWM light modulating device.
The present invention, for realizing above-mentioned functions, be employed technical scheme comprise that a kind of PWM light-dimming method of offer, turns on drive circuit by the high/low level of pwm signal and to load outputting drive voltage or drives electric current, and described pwm signal is pulse signal, and the cycle is Tp, TpFor drive circuit cycle TdIntegral multiple, PWM basis light adjusting grade number LPWM=Tp/Td, the pulsewidth of described pwm signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), it is characterised in that:
Being compiled in collaboration with made control signal by N number of (N >=2, N is positive integer) described pwm signal periodic groups, the cycle of described control signal is N*Tp, actually active working time t in the described control signal cycleeffFor the pulsewidth sum in pwm signal cycle each in this cycle, i indicates the position in pwm signal cycle, 1≤i≤N, t described in the described control signal cycleeff=∑N i=1Tw (i), described PWM light-dimming method is by teffValue performance light adjusting grade.
Preferably, described PWM light-dimming method realizes different t by different Tw (i) combinationseffShow whole light adjusting grade, it may be achieved light adjusting grade be N*LPWM。
Preferably, described control signal is produced by following steps:
Step A receives dim signal Lin；
Step B calculates the composite sequence of the described N number of pwm signal in the described control signal cycle, makes the combination of described N number of pwm signal can realize dim signal LinExpressed light adjusting grade；
Step C controls the output of described pwm signal.
Preferably, the single described control signal cycle is by m (m is positive integer, 1≤m≤N) Tw=p*TdThe described pwm signal cycle and N-m Tw=(p+1) * TdThe described pwm signal cycle combine.
Preferably, described step B can be analyzed to following steps:
Step B1 calculates immediate pwm signal pulsewidth, namely calculates p value, p=INT ((Lin/LMAX)*LPWM), wherein LMAXFor maximum dimmer value；
Step B2 calculates m value, m=INT (N* (p+1-(Lin/LMAX)*(Tp/Tb))+0.5)；
Step B3 organizes into groups, it is determined that m Tw=p*TdThe described pwm signal cycle and N-m Tw=(p+1) * TdThe collating sequence in described pwm signal cycle.
Preferably, described step B3 adopts following algorithm:
As the middle position i=j*INT (N/m) in pwm signal cycle, then Tw (i)=p*Td, j is the positive integer of 1 to m, does not meet other positions then Tw (i)=(p+1) * T of the equationd。
Preferably, described step B3 adopts following algorithm:
As m≤N/2, such as i≤2*m, then odd bits Tw (i)=p*Td, even bit Tw (i)=(p+1) * Td, the whole Tw (i) of i > 2*m=(p+1) * Td；As m > N/2, such as i≤2* (N-m), then odd bits Tw (i)=(p+1) * Td, even bit Tw (i)=p*Td, i > 2* (N-m) is Tw (i)=p*T alld。
Preferably, the value of each Tw (i) leaves a memory element in, and described step C comprises the steps:
I assignment is 0 by step C1；
Step C2 intervalometer performs a timing cycle, and described timing cycle is equal to Tp；
Step C3i=i+1, reads Tw (i) from described memory element, revises the dutycycle of described pwm signal according to Tw (i)；
Step C4 judges that whether i is equal to N, equal execution step C1, does not wait performing step C2.
Preferably, after described step B completes, also including Tw (i) write step, described Tw (i) write step includes:
Interrupt described step C to perform；Each Tw (i) value is write described memory element；Step C starts to perform from step C1 again.
The present invention also provides for a kind of PWM light modulating device, including:
Dim signal interface circuit, receives dim signal；
Drive circuit, outputting drive voltage or driving electric current, its working cycle is Td；
Drive power output interface circuit, connect load；
Control circuit, described control circuit receives described dim signal from described dim signal interface circuit, generate control signal, output is described drive circuit extremely, it is characterized in that described control circuit includes computing module and pwm signal performs module, described computing module adopts the arbitrary described PWM light-dimming method of claim 1-9, calculates pwm signal eigenvalue according to described dim signal, and described pwm signal performs module and generates control signal according to described pwm signal eigenvalue.
Preferably, described control circuit also includes memory element, and described pwm signal eigenvalue is stored in described memory element.
Preferably, described pwm signal performs module and includes PWM signal generator, module for reading and writing, intervalometer, enumerator, described intervalometer triggers described module for reading and writing and is transferred to described PWM signal generator from the pwm signal eigenvalue of described memory element reading ad-hoc location, the position of described pwm signal eigenvalue is determined by the numerical value of described enumerator, described PWM signal generator generates corresponding pwm signal according to described pwm signal eigenvalue, and the N number of described PWM of continuous print forms control signal and exports to described drive circuit.
Preferably, described pwm signal eigenvalue is pwm value or dutyfactor value.
The brightness of luminaire is controlled by technical scheme provided by the present invention by the combination of multiple PWM cycle is formed control signal, after employing a design in which, can not affect light modulation precision in the frequency improving pwm signal simultaneously, simultaneously by the change of assembled scheme, more light adjusting grade can also be obtained, thus it is higher and more smooth out soft dimming effect to realize light modulation precision.
Accompanying drawing explanation
Fig. 1 is the waveform diagram of existing PWM light-dimming method；
Fig. 2 is consistent with the structural representation of the PWM light modulating device of the preferred embodiment of the present invention；
Fig. 3 is the flow chart of PWM light-dimming method embodiment one of the present invention；
Fig. 4 is the flow chart of PWM light-dimming method embodiment two of the present invention；
Fig. 5 is consistent with the waveform diagram of the PWM light-dimming method of the preferred embodiment of the present invention.
Detailed description of the invention
A kind of PWM light-dimming method, the PWM light modulating device that the present invention are proposed below in conjunction with the drawings and specific embodiments are described in further detail.
Refer to shown in Fig. 2, Fig. 2 the structural representation of the preferred embodiment being a kind of PWM light modulating device that the present invention proposes, this PWM light modulating device includes dim signal interface circuit 1, control circuit 2, drive circuit 3, drive circuit output interface circuit 4.Dim signal interface circuit 1 receives the dimming control signal transmitted outside and sends control circuit 2 to, control circuit 2 dimming control signal is resolved, and produces control signal and be sent to drive circuit 3.This control signal is to be combined by multiple pwm signals of the particular duty cycle corresponding with dimming control signal, and circulate output, drive circuit is according to the driving voltage current value of the dutyfactor value output correspondence of PWM, and is exported to corresponding light source by driving power output interface circuit 4.Control circuit 2 can be built can also be realized by a MCU by some resolution elements.Certain complete light modulating device will also include power supply, AC/DC circuit etc. (not shown in Fig. 2), and this can do corresponding configuration according to actual practical situation.
The processing method differring primarily in that control circuit of the present invention and existing light adjusting system.In existing PWM light modulating device, general control circuit is by obtaining a single PWM duty cycle value to the computing of outside dimming control signal, and PWM signal generator realizes light modulation according to this dutycycle output pwm signal.But thus there will be as previously mentioned a kind of problem, inadequate etc. including stroboscopic, light modulation precision.And the solution of the present invention is that the combination of multiple PWM cycle is formed control signal, in the preferred embodiment of the present invention, in a control signal cycle, the dutycycle of each pwm signal is different, such as the dutycycle 3.5% being obtained with originally can not realizing by the pwm signal combination that dutycycle is 3% and 4%.Adopt the frequency that can improve PWM in such a way, as system needs the brightness of 3.5%, if the half of at least this compound mode of PWM frequency carried out either directly through pwm signal pulsewidth.It addition, so more light adjusting grade can be obtained by the combination of the pwm signal of the various different duty of combination.In order to realize such scheme, the structure of control circuit also have to be correspondingly improved, first it is necessary to have a computing module 21 in control circuit, the input of this computing module 21 is dimming control signal, it is output as in the control signal cycle eigenvalue of each pwm signal, and they put in order, this pwm signal eigenvalue can be expressed as the dutycycle of pwm signal, it is also possible to represents the pulsewidth becoming pwm signal.Also including a pwm signal in control circuit and perform module 23, this execution module is sequentially output the pwm signal cycle of different duty or pulsewidth one by one according to the pwm signal eigenvalue that computing obtains, and forms final control signal.That is, pwm signal performs module by one group of pwm signal eigenvalue circulation output, forms control signal.Computing module 21 can perform module 23 in each pwm signal cycle to pwm signal and export corresponding pwm signal eigenvalue, but it is so obviously economical not, therefore in the present embodiment, also include a memory element 22, computing module 21 only carries out once-through operation when dimming control signal changes detecting, then by operation result write storage unit 22, described memory element 22 can be a hardware storage device, it is also possible to realized by data structures such as array, stack, queues.And perform module 23 at pwm signal and include PWM signal generator 2301, module for reading and writing 2302, timer 2 303 and enumerator 2304, timer 2 303 sets timing and is equal to the cycle time of pwm signal, timer 2 303 is covered the timing triggering module for reading and writing 2302 of setting and is performed read-write operation, module for reading and writing 2302 reads the pwm signal eigenvalue of sum counter 2304 numerical value opposite position from memory element 22, and transferring data to PWM signal generator 2301, PWM signal generator 2301 produces to meet the pwm signal of this eigenvalue according to this eigenvalue.A control signal is by N number of (N >=2 in the present embodiment, N is positive integer) pwm signal cycle composition, timer 2 303 is often covered a timing enumerator 2304 and is added 1, reset during to N, when enumerator 2304 completes a circulation from 1 to N, PWM signal generator 2301 produces N number of pwm signal cycle and just completes a control signal cycle, and the constantly circulation in control signal cycle achieves brightness adjustment control.
With regard to the flow chart of specific embodiment, the PWM light-dimming method of the present invention being illustrated below, Fig. 3 is the flow chart of embodiment one, and Fig. 5 is the oscillogram of the control signal obtained according to PWM light-dimming method of the present invention.Here first PWM is controlled ultimate principle and icon does and illustrates, PWM light-dimming method be the high/low level by pwm signal turn on drive circuit 3 to load outputting drive voltage or drive electric current, thus realizing different voltage or electric current output realization to the bright dark adjustment of light source, pwm signal is pulse signal, and the cycle is Tp, adopt Buck/Boost type switching power circuit as drive circuit in the present embodiment, the periodic chart of drive circuit 3 is shown as Td, in order to realize controlled light modulation pwm signal cycle TpFor TdIntegral multiple, PWM basis light adjusting grade number LPWM=Tp/Td, the pulsewidth of pwm signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), the different choosing values of p form different light modulation output.In the present embodiment, as it is shown in figure 5, a pwm signal cycle TpIn comprise 5 drive circuit cycle Td, what Tw represented is the pulsewidth of pwm signal, and when pwm signal is high level, drive circuit is to load output voltage or electric current, and when pwm signal is low level, drive circuit output is shielded.Can certainly when low level output voltage, shielded signal during high level, the light-dimming method of the present invention is not affected by this.As previously mentioned owing to the output of drive circuit is also impulse form, therefore when Tw is Tp10% to 20% between variation time, the time voltage of output will not change, so in this embodiment, it may be achieved light adjusting grade actually only 5 grades, LPWM=5, drive power cycle T by allowing Tw comprise 1,2,3,4 or 5dRealizing 20%, 40%, 60%, 80%, 100% these 5 grades of light adjusting grades, percentage ratio here refers to that output brightness and drive circuit can realize the ratio of high-high brightness.5 light adjusting grades are the needs that can not meet us obviously, when we want that increasing light adjusting grade is not desired to again increase pwm signal cycle Tp, the method that we adopt is to compile in collaboration with make control signal by N number of (N >=2, N is positive integer) pwm signal periodic groups, and the present embodiment adopts 4 pwm signal cycle marshallings to become a control signal cycle T as shown in Figure 5c, Tc=N*TpWe adopt variable i to indicate the position in pwm signal cycle described in the control signal cycle, 1≤i≤N, Tw (i) represents the pulsewidth in i-th pwm signal cycle in the control signal cycle, the light adjusting grade of more stages, Tw (1)=2T in Fig. 5 just can be produced when adopting different pulsewidth combinationsd, Tw (2)=Tw (3)=Tw (4)=Td, such control signal cycle TcIn actually active working time teffFor the pulsewidth sum in pwm signal cycle each in this cycle, teff=Tw(1)+Tw(2)+Tw(3)+Tw(4)=5Td, TcIn altogether comprise 20 Td, therefore in such a control signal cycle TcThe light of middle reality is output as 5Td/20TdEqual to 25%, thus achieve the light adjusting grade of originally cannot realize 25%, 4 pwm signal cycles organizing into groups attainable light adjusting grade is N*LPWM, the light adjusting grade of 20 grades can be realized in the present embodiment.
One complete PWM light-dimming method flow process is as it is shown on figure 3, include three steps:
Step A receives dim signal Lin；
Step B calculates the composite sequence of the described N number of pwm signal in the described control signal cycle, makes the combination of described N number of pwm signal can realize dim signal LinExpressed light adjusting grade；
The combination output that step C is realized pwm signal by pwm signal execution module forms control signal.
That step B calculates is the Tw (i) in the 1st to n-th pwm signal cycle in the present embodiment, namely calculates each pwm signal cycle TpRespective pwm value, so that the actually active working time t that combination is outeffDim signal L can be realizedinExpressed light adjusting grade.The Tw (i) in each pwm signal cycle in one control signal can be arbitrary, as long as it meets Tw (i) for TdIntegral multiple, i.e. Tw=p*T as mentioned befored, it is preferable that, the Tw (i) in each pwm signal cycle one T of difference at most in a control signal cycled, namely it is by p*Td(p+1) * TdCombine.That is the single control signal cycle is by m (m is positive integer, 1≤m≤N) Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdThe pwm signal cycle combine.The fluctuation that such benefit is light modulating device output voltage is not too large, and p*Td(p+x) * TdCombination (x here is the integer be more than or equal to 2), completely can by adjust m quantity realize, as in the present embodiment, adopt 1 4TdThe pwm signal cycle and 3 2TdPwm signal periodic groups incompatible realize 50% light adjusting grade, 2 3T can be passed through completelydThe pwm signal cycle and 2 2TdThe incompatible realization of pwm signal periodic groups, and adopt latter combination output voltage fluctuation be substantially less than the former, do not have obvious light and shade flicker.
As it is shown on figure 3, step B can refine further is decomposed into following steps:
Step B1 calculates immediate pwm signal pulsewidth.Owing to we adopt p*Td(p+1) * TdCombination, that is it is combined by two adjacent PWM basis light adjusting grades, the light adjusting grade that so we need must between the light adjusting grade of the two PWM basis, here we illustrate with the concrete Wave data shown in Fig. 5 for example, when we need the light adjusting grade of 25%, and our PWM basis light adjusting grade only has 20%, 40%, 60%, 80%, 100% these selections, if adjacent two light adjusting grade can only be adopted to be combined, so we can only select 20% and 40% combination to adopt the light adjusting grade realizing 25%, if this light adjusting grade is converted to pulsewidth, namely p needs to meet equation below p*Td≤(Lin/LMAX)*Tp< (p+1) * Td.Wherein LMAXFor maximum dimmer value, LinAnd LMAXUnit must unify, if input dim signal LinFor brightness value, then LMAXFor the attainable high-high brightness of system；As inputted dim signal LinFor light adjusting grade, then LMAXFor the attainable maximum light adjusting grade numbers of system；As inputted dim signal LinFor the percentage ratio of high-high brightness, then LMAXIt is 1.In other words namely the value of p is less than LinRequired light adjusting grade and immediate value, this step seeks to calculate p value, and by the conversion of formula above, we can draw p=INT ((Ld/LMAX)*LPWM), here INT represents bracket function, because p is only integer and just removes fractional part in time calculating and decimal occur, for actual numerical value, the light modulation brightness of 25% is p=INT ((25%/1) * 5)=INT (1.25)=1 when base level is 5, and so we just can show that the light modulation brightness of 25% should by 1TdAnd 2TdCombine.
Step B2 calculates m value.Since the single control signal cycle is by m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdThe pwm signal cycle combine, then m is also a calculative significant in value.By equation (m*p*Td+(N-m)*(p+1)*Td)/N=(Lin/LMAX)*TpCarry out conversion and can draw m=N* (p+1-(Lin/LMAX)*(Tp/Tb)), but cannot ensure that the value of calculation of m is just for integer in actual applications, it is necessary to structure is rounded up, then computing formula is then for conversion into m=INT (N* (p+1-(Lin/LMAX)*(Tp/Tb))+0.5)。
Step B3 organizes into groups, it is determined that m Tw=p*TdThe described pwm signal cycle and N-m Tw=(p+1) * TdThe collating sequence in described pwm signal cycle.Since there being m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdThe pwm signal cycle, then how this arranged and also required over computing and determine these pwm signal cycles.We can first send m Tw=p*T simplydThe pwm signal cycle, then send N-m Tw=(p+1) * TdThe pwm signal cycle, but the change of output voltage so can be made obvious, it is preferred that mode is to be arranged by staggered arrangement during the pwm signal week of distinct pulse widths.Here these signals can be uniformly distributed by we, and specific algorithm is as follows: as the middle position i=j*INT (N/m) in pwm signal cycle, then Tw (i)=p*Td, j is the positive integer of 1 to m, does not meet other positions then Tw (i)=(p+1) * T of the equationd.With a concrete numbers illustrated, when, in the marshalling being made up of 10 pwm signal cycles, having 3 Tw=p*TdPwm signal, then j substitute into 1,2,3, then i be equal to 1*INT (10/3), 2*INT (10/3), 3*INT (10/3) 3 Tw=p*T of these 3 position distributiondPwm signal, respectively the 3rd, the 6th, the 9th, all the other positions are then Tw=(p+1) * TdPwm signal.The available another kind of algorithm of this step is, original position selects the pulsewidth occupied the minority as initial signal, signal below is spaced until this pulsewidth number occupied the minority is finished one by one, follow-up is all then another kind of pulsewidth, or it is example with numerical value above: 10 pwm signal cycle composition marshallings, such as Tw=p*TdThe signal of pwm signal have 3, Tw=(p+1) * TdPwm signal have 7, then first Tw (1)=p*Td, Tw (2) subsequently=(p+1) * Td、Tw(3)=p*Td、Tw(4)=(p+1)*Td、Tw(5)=p*TdAt this moment 3 Tw=p*TdPwm signal be distributed, Tw (6) to Tw (10) below is all just (p+1) * TdIf, Tw=p*TdSignal occupy the majority, then first Tw (1)=(p+1) * TdLatter one is p*TdAlternately compile until Tw=(p+1) * TdSignal use up, all the other are all Tw=p*TdSignal.That is as m≤N/2, such as i≤2*m, then odd bits Tw (i)=p*Td, even bit Tw (i)=(p+1) * Td, Tw (i)=(p+1) the * T as i > 2*md；As m > N/2, such as i≤2* (N-m), then odd bits Tw (i)=(p+1) * Td, even bit Tw (i)=p*Td, Tw (i)=p*T as i > 2* (N-m)d。
As it is shown on figure 3, step C also can refine decomposition further, we specifically explain step C in conjunction with the hardware configuration module in Fig. 2:
I assignment is 0 by step C1, and enumerator 2304 resets；
Step C2 timer 2 303 performs a timing cycle, and described timing cycle is equal to Tp, TpBeing set in advance in timer 2 303, a timing cycle completes, and on hardware, timer 2 303 triggers module for reading and writing 2302 and works, and performs subsequent step C3 in program；
Step C3 enumerator performs to add an operation, then i=i+1, module for reading and writing 2302 reads Tw (i) from memory element 22, and PWM signal generator 2301 is revised the dutycycle of described pwm signal according to Tw (i) and exports this pwm signal；
Step C4 judges that whether i is equal to N, namely judges whether enumerator 2304 overflows, and then performs step C2 as i=N performs step C1, i ≠ N.
PWM light-dimming method described above is embodiments of the invention one, and superincumbent light modulation performs in step to be first receive dimming information, and again through computing and export control signal, this is a basic step.But the light modulation demand of user is uncertain in actual applications, it is necessary to whether running check has light modulation demand, and therefore we this provide embodiment two, as shown in Figure 4.In embodiment two, most operating procedure is similar with embodiment one, but step A includes two sub-steps, namely dimming control signal is detected, dimming control signal and current brightness value are compared, such as the execution step B that changes, unchanged, continue detection, say, that only just perform calculation step when brightness needs and changes.When system is run first, current brightness value is zero, just has monochrome information come hence into calculation step as long as so opening light fixture, and concrete operation method is with embodiment one.And computing performs step C after completing in this example, the particular content of step C is with embodiment one, but the difference is that, in the present embodiment, step C is at independent execution state after starting execution, should be step C is a circulation execution program, just constantly exports according to currently stored pwm signal eigenvalue as long as no turning off the light, thus realizing a fixing specific brightness.While step C performs, step A also continues to constantly detect, once find that the change of light modulation brightness begins to perform step B.Pattern due to this step A and step C executed in parallel, Tw (i) write step is also had after step B completes, because step B needs operation result write storage unit 22 after completing, and now step C is ceaselessly reading the data in memory element, the words write direct can produce read-write error, and make the light modulation that the pulsewidth generation great change in follow-up pwm signal cycle cannot realize smoothing change when a control signal cycle goes to half.Therefore first sending an interruptive command in Tw (i) write step, the execution of interrupt step C, then by the operation result write storage unit 22 of step B.But the output that such interruption is step C pwm signal out of service can't stop, but due to do not carry out counting and read operation, during interrupting, the pulsewidth of pwm signal will not change, and remains current Tw value output pwm signal.When write completes then reboot step C, namely bring into operation step C from the starting point P of step C, before no matter dimming, step C runs to where, now all enumerator 2304 is reset, and again it is timed triggering, start to read Tw (i) from the 1st position, and output realizes new light modulation brightness one by one.
Description of the preferred embodiment of the present invention illustrates that and describes above, it is not intended to limit of the present invention or is confined to disclosed concrete form, obviously, it is likely to make many modifications and variations, these modifications and variations are obvious possibly for those skilled in the art, it should include within the scope of the present invention being defined by the appended claims.
Claims (13)
1. a PWM light-dimming method, turn on drive circuit by the high/low level of pwm signal and to load outputting drive voltage or drive electric current, described pwm signal is pulse signal, cycle is Tp, Tp is the integral multiple of drive circuit cycle T d, PWM basis light adjusting grade number LPWM=Tp/Td, and the pulsewidth of described pwm signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), it is characterised in that:
By N number of (N >=2, N is positive integer) described pwm signal periodic groups compiles in collaboration with and makes control signal, the cycle of described control signal is N*Tp, actually active working time teff in the described control signal cycle is the pulsewidth sum in each pwm signal cycle in this cycle, i indicates the position in pwm signal cycle described in the described control signal cycle, 1≤i≤N, teff=∑ Ni=1Tw (i), described PWM light-dimming method is showed light adjusting grade by the value of teff.
2. PWM light-dimming method according to claim 1, it is characterised in that described PWM light-dimming method realizes different teff by different Tw (i) combinations and shows whole light adjusting grade, it may be achieved light adjusting grade be N*LPWM.
3. PWM light-dimming method according to claim 1 and 2, it is characterised in that described control signal is produced by following steps:
Step A receives dim signal Lin；
Step B calculates the composite sequence of the described N number of pwm signal in the described control signal cycle, makes the combination of described N number of pwm signal can realize the light adjusting grade expressed by dim signal Lin；
Step C controls the output of described pwm signal.
4. PWM light-dimming method according to claim 3, it is characterized in that the single described control signal cycle was combined by m the described pwm signal cycle of (m is positive integer, 1≤m≤N) Tw=p*Td and the described pwm signal cycle of N-m Tw=(p+1) * Td.
5. PWM light-dimming method according to claim 4, it is characterised in that described step B can be analyzed to following steps:
Step B1 calculates immediate pwm signal pulsewidth, namely calculates p value, and p=INT ((Lin/LMAX) * LPWM), wherein LMAX is maximum dimmer value；
Step B2 calculates m value, m=INT (N* (p+1-(Lin/LMAX) * (Tp/Tb))+0.5)；
Step B3 organizes into groups, it is determined that the collating sequence in the described pwm signal cycle of m Tw=p*Td and the described pwm signal cycle of N-m Tw=(p+1) * Td.
6. PWM light-dimming method according to claim 5, it is characterised in that described step B3 adopts following algorithm:
When the middle position i=j*INT (N/m) in pwm signal cycle, then Tw (i)=p*Td, j is the positive integer of 1 to m, does not meet other positions then Tw (i)=(p+1) * Td of the equation.
7. PWM light-dimming method according to claim 5, it is characterised in that described step B3 adopts following algorithm:
As m≤N/2, such as i≤2*m, then odd bits Tw (i)=p*Td, even bit Tw (i)=(p+1) * Td, i whole Tw (i) of > 2*m=(p+1) * Td；As m > N/2, such as i≤2* (N-m), then odd bits Tw (i)=(p+1) * Td, even bit Tw (i)=p*Td, i > 2* (N-m) all Tw (i)=p*Td.
8. PWM light-dimming method according to claim 1 and 2, it is characterised in that the value of each Tw (i) leaves a memory element in, and described step C comprises the steps:
I assignment is 0 by step C1；
Step C2 intervalometer performs a timing cycle, and described timing cycle is equal to Tp；
Step C3i=i+1, reads Tw (i) from described memory element, revises the dutycycle of described pwm signal according to Tw (i)；
Step C4 judges that whether i is equal to N, equal execution step C1, does not wait performing step C2.
9. PWM light-dimming method according to claim 8, it is characterised in that after described step B completes, also includes Tw (i) write step, and described Tw (i) write step includes:
Interrupt described step C to perform；Each Tw (i) value is write described memory element；Step C starts to perform from step C1 again.
10. a PWM light modulating device, including:
Dim signal interface circuit, receives dim signal；
Drive circuit, outputting drive voltage or driving electric current, its working cycle is Td；
Drive power output interface circuit, connect load；
Control circuit, described control circuit receives described dim signal from described dim signal interface circuit, generate control signal, output is described drive circuit extremely, it is characterized in that described control circuit includes computing module and pwm signal performs module, described computing module adopts the arbitrary described PWM light-dimming method of claim 1-9, calculates pwm signal eigenvalue according to described dim signal, and described pwm signal performs module and generates control signal according to described pwm signal eigenvalue.
11. PWM light modulating device according to claim 10, it is characterised in that described control circuit also includes memory element, and described pwm signal eigenvalue is stored in described memory element.
12. PWM light modulating device according to claim 11, it is characterized in that described pwm signal performs module and includes PWM signal generator, module for reading and writing, intervalometer, enumerator, described intervalometer triggers described module for reading and writing and is transferred to described PWM signal generator from the pwm signal eigenvalue of described memory element reading ad-hoc location, the position of described pwm signal eigenvalue is determined by the numerical value of described enumerator, described PWM signal generator generates corresponding pwm signal according to described pwm signal eigenvalue, the N number of described PWM of continuous print forms control signal and exports to described drive circuit.
13. according to the PWM light modulating device described in claim 10,11 or 12, it is characterised in that described pwm signal eigenvalue is pwm value or dutyfactor value.
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