CN105764204B - A kind of PWM light-dimming methods and PWM light modulating devices - Google Patents
A kind of PWM light-dimming methods and PWM light modulating devices Download PDFInfo
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Abstract
The present invention provides a kind of PWM light-dimming methods and PWM light modulating devices, to form control signal by the way that multiple PWM cycles are combined and be controlled come the brightness to lighting apparatus, after employing a design in which, light modulation precision can not be influenceed in the frequency for improving pwm signal simultaneously, pass through the change of assembled scheme simultaneously, more light adjusting grades can also be obtained, so as to realize that light modulation precision is higher and more smooth out soft dimming effect.
Description
Technical field
The present invention relates to a kind of PWM light-dimming methods and PWM light modulating devices.
Background technology
With the development of LED rapid technology, increasing LED light source instead of traditional light source.It is well known that
LED has the advantages of many as light source, and easily light modulation toning is one of LED great advantage.With Internet of Things and smart home
Development and popularization, it is more and more to dimming light source demand, and to the quality requirement of light modulation also more and more higher.So LED tune
Light technology needs constantly progressive, the advantage of competence exertion itself, complies with the development spring tide of smart home.
At present, the most frequently used LED dimming modes dim for PWM, and its principle is to Buck/Boost types using pwm signal
Switching power circuit is controlled, according to the dutyfactor value of pwm signal, voltage x current value corresponding to output.As shown in Figure 1
The switching frequency of Buck/Boost type Switching Power Supplies is higher, typically between tens of Khz to hundreds of Khz.PWM frequency typically exists
Hundreds of arrive between several Khz, are turned on/off by the High/Low of PWM level come the electric current of controlling switch power supply fundamental wave.PWM believes
Number cycle be generally the integral multiple in switching power circuit cycle because the PWM pulsewidths PWM HIGH times as shown in Figure 1 increase
If part Δ t when being placed exactly in the LOW in switching power circuit a cycle, the increase of such PWM pulsewidths is for output
It is exactly invalid for electric current, rear end exports unchanged to LED electric current, it is impossible to play actual light modulation effect.And consider
To the stationary problem of two signals, therefore PWM effective light adjusting grade is equal to switch power supply in existing PWM control programs
Road frequency fbDivided by PWM frequency fp(Leff=fb/fp)。
Due to the above-mentioned operation principle of PWM controls, a contradiction is just generated, if it is desired to increase light adjusting grade and just should
Reduce the frequency of pwm signal, but when PWM frequency is low, stroboscopic easily occurs in LED light source, and LED light source is clapped with picture pick-up device
When taking the photograph, obvious ripple can be appreciated that.Conversely, the raising of PWM frequency, although can reduce described stroboscopic ripple problem, brings
Negative effect be reduction of light adjusting grade number, and then dim fineness can step-down, cause brightness change in dimming process inadequate
Smoothly, light source scintillation can even visually be felt.
The content of the invention
The invention aims to solve the above problems, there is provided a kind of dimming effect more smoothes out soft PWM light modulations
Method, PWM light modulating devices.
To realize above-mentioned function, used technical scheme is to provide a kind of PWM light-dimming methods, believed by PWM the present invention
Number high/low level come turn on drive circuit to load outputting drive voltage or driving current, the pwm signal be arteries and veins
Rush signal, cycle Tp, TpFor drive circuit cycle TdIntegral multiple, PWM bases light adjusting grade number LPWM=Tp/Td, the PWM
The pulsewidth of signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), it is characterised in that：
Compiled in collaboration with by N number of (N >=2, N are positive integer) pwm signal periodic groups and control signal is made, the control signal
Cycle is N*Tp, the actually active working time t in the control signal cycleeffFor the arteries and veins in each pwm signal cycle in the cycle
Wide sum, i indicate the position in pwm signal cycle described in a control signal cycle, 1≤i≤N, teff=∑N I=1Tw
(i), the PWM light-dimming methods are by teffValue performance light adjusting grade.
Preferably, the PWM light-dimming methods realize different t by different Tw (i) combinationseffTo show whole light modulations
Grade, achievable light adjusting grade are N*LPWM。
Preferably, the control signal is produced by following steps：
Step A receives dim signal Lin；
Step B calculates the composite sequence of N number of pwm signal in the control signal cycle, makes N number of PWM letters
Number combination dim signal L can be achievedinExpressed light adjusting grade；
Step C controls the pwm signal output.
Preferably, the single control signal cycle is by m (m be positive integer, 1≤m≤N) Tw=p*TdThe PWM
Signal period and N-m Tw=(p+1) * TdThe pwm signal cycle combine.
Preferably, the step B can be analyzed to following steps：
Step B1 calculates immediate pwm signal pulsewidth, that is, calculates p value, p=INT ((Lin/LMAX)*LPWM), wherein LMAX
For maximum dimmer value；
Step B2 calculates m values, m=INT (N* (p+1- (Lin/LMAX)*(Tp/Td))+0.5)；
Step B3 is organized into groups, and determines m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdIt is described
The collating sequence in pwm signal cycle.
Preferably, the step B3 uses following algorithm：
When the middle position i=j*INT (N/m) in pwm signal cycle, then Tw (i)=p*Td, j is 1 positive integer for arriving m, is not inconsistent
Close other positions then Tw (i)=(p+1) * T of the equationd。
Preferably, the step B3 uses 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 ＞ 2*m are complete
Portion Tw (i)=(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) whole Tw (i)=p*Td。
Preferably, the value of each Tw (i) is stored in a memory cell, and the step C comprises the following steps：
Step C1 is entered as 0 to i；
Step C2 timers perform a timing cycle, and the timing cycle is equal to Tp；
Step C3i=i+1, Tw (i) is read from the memory cell, the duty of the pwm signal is changed according to Tw (i)
Than；
Step C4 judges whether i is equal to N, equal execution step C1, does not wait performing step C2.
Preferably, after the completion of the step B, in addition to Tw (i) write step, Tw (i) write step include：
The step C is interrupted to perform；Each Tw (i) value is write into the memory cell；Step C is held since step C1 again
OK.
The present invention also provides a kind of PWM light modulating devices, including：
Dim signal interface circuit, receive dim signal；
Drive circuit, outputting drive voltage or driving current, its work period are Td；
Driving power output interface circuit, connection load；
Control circuit, the control circuit receive the dim signal, generation control from the dim signal interface circuit
Signal, exporting to the drive circuit, it is characterised in that the control circuit includes computing module and pwm signal execution module,
The computing module calculates pwm signal using any described PWM light-dimming methods of claim 1-9 according to the dim signal
Characteristic value, the pwm signal execution module generate control signal according to the pwm signal characteristic value.
Preferably, the control circuit also includes memory cell, and it is single that the pwm signal characteristic value is stored in the storage
Member.
Preferably, the pwm signal execution module includes PWM signal generator, module for reading and writing, timer, counter, institute
State module for reading and writing described in timers trigger from the memory cell read ad-hoc location pwm signal characteristic value be transferred to it is described
PWM signal generator, the position of the pwm signal characteristic value determine by the numerical value of the counter, the PWM signal generator
Corresponding pwm signal is generated according to the pwm signal characteristic value, continuous N number of PWM forms control signal to the driving
Circuit output.
Preferably, the pwm signal characteristic value is pwm value or dutyfactor value.
Technical scheme provided by the present invention by multiple PWM cycles by combining to form control signal come to lighting apparatus
Brightness is controlled, and after employing a design in which, can not influence light modulation precision simultaneously in the frequency for improving pwm signal,
Simultaneously by the change of assembled scheme, more light adjusting grades can also be obtained, so as to realize that light modulation precision is higher and more
Smooth out soft dimming effect.
Brief description of the drawings
Fig. 1 is the waveform diagram of existing PWM light-dimming methods；
Fig. 2 is the structural representation for the PWM light modulating devices for meeting the preferred embodiment of the present invention；
Fig. 3 is the flow chart of PWM light-dimming methods embodiment one of the present invention；
Fig. 4 is the flow chart of PWM light-dimming methods embodiment two of the present invention；
Fig. 5 is the waveform diagram for the PWM light-dimming methods for meeting the preferred embodiment of the present invention.
Embodiment
A kind of PWM light-dimming methods proposed by the present invention, PWM light modulating devices are made below in conjunction with the drawings and specific embodiments into
One step is described in detail.
Fig. 2 is refer to, is a kind of structure of a preferred embodiment of PWM light modulating devices proposed by the present invention shown in Fig. 2
Schematic diagram, the PWM light modulating devices include dim signal interface circuit 1, control circuit 2, drive circuit 3, drive circuit and export and connect
Mouth circuit 4.Dim signal interface circuit 1 receives the outside dimming control signal transmitted and sends control circuit 2 to, by control electricity
Road 2 parses to dimming control signal, and produces control signal and be sent to drive circuit 3.The control signal is by being controlled with light modulation
Multiple pwm signals of the corresponding particular duty cycle of signal processed combine, and circulate output, and drive circuit is according to PWM's
Driving voltage current value corresponding to dutyfactor value output, and exported by driving power output interface circuit 4 to corresponding light source.Control
Circuit 2 processed can be built by some resolution elements to be realized by a MCU.Certain complete light modulating device
(not shown in Fig. 2) such as power supply, AC/DC circuits is will also include, this can make corresponding configuration according to actual practical situation.
The main distinction of of the invention and existing light adjusting system is the processing method of control circuit.Dimmed in existing PWM
In device, general control circuit obtains a single PWM duty cycle value, PWM by the computing to outside dimming control signal
Signal generator is realized according to this dutycycle output pwm signal and dimmed.But one kind as previously mentioned thus occurs
Problem, including stroboscopic, light modulation precision not enough etc..And the solution method of the present invention is to combine multiple PWM cycles to form control letter
Number, in the preferred embodiment of the present invention, the dutycycle of each pwm signal is different in a control signal cycle, as that will account for
The empty pwm signal combination than for 3% and 4% is obtained with original impossible dutycycle 3.5%.Using such side
Formula can improve PWM frequency, as system needs 3.5% brightness, directly by pwm signal pulsewidth come the PWM frequency that carries out
If the half of at least this combination.In addition, so can be with by the combination for the pwm signal for combining various different duties
Obtain more light adjusting grades.In order to realize such scheme, the structure of control circuit also has to be correspondingly improved, first
It must have a computing module 21 in control circuit, the computing module 21 input is dimming control signal, is exported as a control
The characteristic value of each pwm signal in signal period processed, and they put in order, this pwm signal characteristic value can be expressed as
The dutycycle of pwm signal, the pulsewidth as pwm signal can also be represented.Also include a pwm signal in control circuit and perform mould
Block 23, the pwm signal characteristic value that the execution module obtains according to computing are sequentially output the PWM letters of different duty or pulsewidth one by one
Number cycle, form final control signal.That is, pwm signal execution module exports one group of pwm signal characteristic value circulation, is formed
Control signal.Computing module 21 can export corresponding PWM in each pwm signal cycle to pwm signal execution module 23 to be believed
Number characteristic value, but it is so obviously not economical enough, therefore in the present embodiment, in addition to a memory cell 22, computing module
21 only carry out once-through operation when detecting that dimming control signal changes, then by operation result write storage unit 22,
The memory cell 22 can be a hardware storage device, can also be realized by data structures such as array, stack, queues.
And include PWM signal generator 2301, module for reading and writing 2302, timer 2 303 and counter in pwm signal execution module 23
2304, timer 2 303 sets the cycle time that timing is equal to pwm signal, and timer 2 303 covers the timing of setting
Trigger module for reading and writing 2302 and perform read-write operation, module for reading and writing 2302 reads relative with the numerical value of counter 2304 from memory cell 22
The pwm signal characteristic value of position is answered, and transfers data to PWM signal generator 2301, PWM signal generator 2301 is according to this
Characteristic value produces the pwm signal for meeting this feature value.A control signal is by N number of (N >=2, N are positive integer) in the present embodiment
The pwm signal cycle forms, and timer 2 303 often covers a timing counter 2304 plus 1, resets during to N, works as counter
2304 complete one from 1 to N circulations, and PWM signal generator 2301 produces N number of pwm signal cycle and just completes a control
Signal period, the continuous circulation in control signal cycle realize brightness adjustment control.
The flow chart of specific embodiment is illustrated to the PWM light-dimming methods of the present invention below, Fig. 3 is embodiment one
Flow chart, Fig. 5 are the oscillogram of the control signal obtained according to PWM light-dimming methods of the present invention.Here base first is controlled to PWM
Present principles and icon, which are done, to be illustrated, PWM light-dimming methods are to turn on drive circuit by the high/low level of pwm signal
3 to load outputting drive voltage or driving current, so as to realize that different voltage or electric current output realize dark tune bright to light source
Whole, pwm signal is pulse signal, cycle Tp, in the present embodiment using Buck/Boost types switching power circuit as drive
Dynamic circuit, the cycle of drive circuit 3 are expressed as Td, in order to realize controllable light modulation pwm signal cycle TpFor TdIntegral multiple, PWM
Basic light adjusting grade number LPWM=Tp/Td, the pulsewidth of pwm signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), p difference
Choosing is worth to form different light modulation output.In the present embodiment, as shown in figure 5, a pwm signal cycle TpIn comprising 5 driving
Circuit period Td, what Tw was represented is the pulsewidth of pwm signal, when pwm signal is high level drive circuit to load output voltage or
Electric current, drive circuit is exported and shielded when pwm signal is low level.Can certainly in low level output voltage, high level
When shielded signal, this on the present invention light-dimming method do not influence.As previously described because the output of drive circuit is also pulse
Form, therefore when Tw is Tp10% to 20% between when changing, the time voltage of output will not change, thus
In this embodiment, achievable light adjusting grade actually only has 5 grades, LPWM=5, by allowing Tw to include 1,2,3,4 or 5 drive
Dynamic power cycle Td20%, 40%, 60%, 80%, 100% this 5 grades of light adjusting grades are realized, percentage here refers to export bright
Degree and drive circuit can realize the ratio of high-high brightness.Obviously 5 light adjusting grades are can not to meet our needs, when us
Wanting increases light adjusting grade is not desired to increase pwm signal cycle T againp, the method that we use is with N number of (N >=2, N are positive integer)
Pwm signal periodic groups, which are compiled in collaboration with, is made control signal, and the present embodiment as shown in Figure 5 turns into one using 4 pwm signal cycle marshallings
Control signal cycle Tc, Tc=N*Tp, we indicate the position in pwm signal cycle described in a control signal cycle using variable i
Put, 1≤i≤N, Tw (i) represent the pulsewidth in i-th of pwm signal cycle in the control signal cycle, are combined when using different pulsewidths
When can produce the light adjusting grade of more stages, Tw (1)=2T in Fig. 5d, Tw (2)=Tw (3)=Tw (4)=Td, so control
Signal period TcIn actually active working time teffFor the pulsewidth sum in each pwm signal cycle in the cycle, teff=Tw (1)
+ Tw (2)+Tw (3)+Tw (4)=5Td, TcIn altogether include 20 Td, therefore in such a control signal cycle TcMiddle reality
Light output be 5Td/20TdEqual to 25%, 25% light adjusting grade that can not be realized originally is so achieved that, is believed by 4 PWM
It is N*L that number cycle, which organizes into groups achievable light adjusting grade,PWM, 20 grades of light adjusting grade can be realized in the present embodiment.
One complete PWM light-dimming methods flow is as shown in figure 3, including three steps：
Step A receives dim signal Lin；
Step B calculates the composite sequence of N number of pwm signal in the control signal cycle, makes N number of PWM letters
Number combination dim signal L can be achievedinExpressed light adjusting grade；
Step C realizes that the combination of pwm signal exports by pwm signal execution module and forms control signal.
That step B is calculated in the present embodiment is the 1st Tw (i) for arriving the n-th pwm signal cycle, that is, calculates each PWM letters
Number cycle TpRespective pwm value, to be combined into the actually active working time t comeeffDim signal L can be realizedinInstitute
The light adjusting grade of expression.The Tw (i) in each pwm signal cycle in one control signal can be arbitrary, as long as it meets
Tw (i) is TdIntegral multiple, i.e., Tw=p*T as mentioned befored, it is preferable that, each PWM letters in a control signal cycle
The Tw (i) in number cycle at most one T of differenced, it is by p*Td(p+1) * TdCombine.That is single control signal
Cycle is by m (m be positive integer, 1≤m≤N) Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdPWM letter
Number cycle combines.Such benefit is that the fluctuation of light modulating device output voltage is not too large, and p*Td(p+x) * Td's
Combination (x here is the integer more than or equal to 2), can be realized by adjusting m quantity completely, such as in the present embodiment,
Using 1 4TdThe pwm signal cycle and 3 2TdThe pwm signal cycle combine and realize 50% light adjusting grade, completely can be with
Pass through 2 3TdThe pwm signal cycle and 2 2TdPwm signal cycle combine and realize, and use latter combination output electricity
The fluctuation of pressure is substantially less than the former, does not have obvious light and shade flicker.
As shown in figure 3, step B, which can be refined further, is decomposed into following steps：
Step B1 calculates immediate pwm signal pulsewidth.Because we are to use p*Td(p+1) * TdCombination, also
It is say to be combined by two adjacent PWM bases light adjusting grades, the light adjusting grade that so we need must will be located at this
Between two PWM bases light adjusting grades, we illustrate using the specific Wave data shown in Fig. 5 as example here, when we need
25% light adjusting grade is wanted, and our PWM bases light adjusting grade only has 20%, 40%, 60%, 80%, 100% these choosings
Select, if can only be combined using two adjacent light adjusting grades, then we can only select 20% and 40% combination to adopt
With the light adjusting grade for realizing 25%, if this light adjusting grade is converted into pulsewidth, i.e. 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 light modulation
Signal LinFor brightness value, then LMAXFor the achievable high-high brightness of system；Such as input dim signal LinFor light adjusting grade, then LMAX
For the achievable at most light adjusting grade number of system；Such as input dim signal LinFor the percentage of high-high brightness, then LMAXFor 1.Change speech
I.e. p value be less than LinRequired light adjusting grade and immediate value, the step seek to calculate p value, by public above
The conversion of formula we can draw p=INT ((Ld/LMAX)*LPWM), INT represents bracket function here, because p is only integer
Fractional part is just removed when decimal occurs in calculating, by taking actual numerical value as an example, 25% light modulation brightness is 5 in base level
When p=INT ((25%/1) * 5)=INT (1.25)=1, so our cans show that 25% light modulation brightness should be by 1Td
And 2TdCombine.
Step B2 calculates m values.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)*TpM=N* (p+1- (L can be drawn by entering line translationin/LMAX)*(Tp/Td)),
But can not to ensure m calculated value in actual applications be just integer, it is necessary to be rounded up to structure, then is calculated public
Formula is then for conversion into m=INT (N* (p+1- (Lin/LMAX)*(Tp/Td))+0.5)。
Step B3 is organized into groups, and determines m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdInstitute
State the collating sequence in pwm signal cycle.Since there is m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * Td's
The pwm signal cycle, then how this arranged and needed to determine by computing in pwm signal cycles these.We can letter
Single ground first sends m Tw=p*TdThe pwm signal cycle, then send N-m Tw=(p+1) * TdThe pwm signal cycle, still
It can so make the change of output voltage obvious, preferably be arranged wrong 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/ in pwm signal cycle
M), then Tw (i)=p*Td, j is 1 positive integer for arriving m, does not meet the other positions of the equation then Tw (i)=(p+1) * Td.With one
Individual concrete numerical value explanation, when in the marshalling being made up of 10 pwm signal cycles, there is 3 Tw=p*TdPwm signal, then j generations
Enter 1,2,3, then i is equal to 3 1*INT (10/3), 2*INT (10/3), this 3 position distributions of 3*INT (10/3) Tw=p*Td's
Pwm signal, the respectively the 3rd, the 6th, the 9th, remaining position is then Tw=(p+1) * TdPwm signal.This step is available
Another algorithm is, the pulsewidth that original position selection occupies the minority as initial signal, signal below be spaced one by one until
This pulsewidth number to occupy the minority is finished, subsequently then all another pulsewidths, or with exemplified by numerical value above：10 PWM letters
The composition marshalling of number cycle, such as Tw=p*TdThe signal of pwm signal have 3, Tw=(p+1) * TdPwm signal have 7, then
One Tw (1)=p*Td, subsequent Tw (2)=(p+1) * Td, Tw (3)=p*Td, Tw (4)=(p+1) * Td, Tw (5)=p*TdThis
When 3 Tw=p*TdPwm signal be distributed completion, Tw (6) below to Tw (10) just all (p+1) * TdIf Tw=
p*TdSignal occupy the majority, then first Tw (1)=(p+1) * TdLatter position is p*TdAlternating is compiled until Tw=(p+1) * Td
Signal use up, remaining 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) * 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 shown in figure 3, step C also can further refine decomposition, the hardware configuration module that we are combined in Fig. 2 is come specifically
Solve step C：
Step C1 is entered as 0 to i, and counter 2304 is reset；
Step C2 timer 2s 303 perform a timing cycle, and the timing cycle is equal to Tp, TpIt is set in advance in timer
In 2303, a timing cycle is completed, and timer 2 303 triggers module for reading and writing 2302 and worked on hardware, and follow-up step is performed in program
Rapid C3；
Step C3 counters perform plus an operation, then i=i+1, module for reading and writing 2302 read Tw (i) from memory cell 22,
PWM signal generator 2301 changes the dutycycle of the pwm signal according to Tw (i) and exports the pwm signal；
Step C4 judges whether i is equal to N, that is, judges whether counter 2304 overflows, as i=N performs step C1, i ≠ N then
Perform step C2.
PWM light-dimming methods described above are embodiments of the invention one, and it is first that superincumbent light modulation, which is performed in step,
Dimming information is received, then by computing and output control signal, this is a basic step.But user in actual applications
Light modulation demand be uncertain, it is necessary to whether running check has light modulation demand, therefore provide embodiment two here,
As shown in Figure 4.Most operating procedure is similar with embodiment one in embodiment two, but step A includes two sub-steps,
Dimming control signal is detected, dimming control signal and current brightness value are compared, such as changes and performs step B, it is unchanged
Then continue to detect, that is to say, that only just perform calculation step when brightness needs to change.When system is run first, current brightness
Value is zero, is come as long as so opening light fixture and just having monochrome information hence into calculation step, concrete operation method is the same as implementation
Example one.And in this example after the completion of computing perform step C, step C particular content with embodiment one, but unlike,
In the present embodiment, step C starts to be at single execution state after performing, and should be step C is a circulation configuration processor,
Just constantly exported according to currently stored pwm signal characteristic value as long as no turning off the light, so as to realize that fixed one is specific bright
Degree.While step C is performed, step A also continues to constantly detect, once find that the change of light modulation brightness begins to perform step
Rapid B.Due to the pattern that this step A and step C are performed parallel, there is Tw (i) write step after the completion of step B, because
To be needed operation result write storage unit 22 after the completion of step B, and now step C is ceaselessly read in memory cell
Data, read-write error can be produced if writing direct, and after causing when half is gone in a control signal cycle
Great change, which occurs, for the pulsewidth in continuous pwm signal cycle can not realize smooth light modulation change.Therefore in Tw (i) write steps first
Send an interruptive command, interrupt step C execution, then by step B operation result write storage unit 22.In such
Disconnected simply step C out of service but the output of pwm signal can't stop, but due to without counting and read operation,
It will not be changed in the pulsewidth of Interruption period between The following article pwm signal, remain current Tw value output pwm signals.When write-in is completed
Then reboot step C, that is, the step C that brought into operation at step C starting point P, no matter what step C runs to before light modulation
Place, now all resets counter 2304, and is timed triggering again, and Tw (i) is read since the 1st position, and defeated one by one
Go out and realize new light modulation brightness.
Description of the preferred embodiment of the present invention above is to illustrate and describe, and is not intended to limit of the present invention or office
It is limited to disclosed concrete form, it is clear that many modifications and variations may be made, these modifications and variations may be for this area
It is obvious for technical staff, should be included with the scope of the present invention being defined by the appended claims.
Claims (10)
1. a kind of PWM light-dimming methods, drive circuit is turned on to load output driving by the high/low level of pwm signal
Voltage or driving current, the pwm signal are pulse signal, cycle Tp, TpFor drive circuit cycle TdIntegral multiple, PWM bases
Plinth light adjusting grade number LPWM=Tp/Td, the pulsewidth of the pwm signal is Tw=p*Td(p is positive integer, 1≤p≤LPWM), its feature
It is：
Compiled in collaboration with by N number of (N >=2, N are positive integer) pwm signal periodic groups and control signal is made, the cycle of the control signal
For N*Tp, the actually active working time t in the control signal cycleeffFor each pwm signal cycle in the cycle pulsewidth it
With the position in pwm signal cycle, 1≤i≤N, t described in i one control signal cycle of signeff=∑N I=1Tw (i),
The PWM light-dimming methods are by teffValue performance light adjusting grade,
The control signal is produced by following steps：
Step A receives dim signal Lin；
Step B calculates the composite sequence of N number of pwm signal in the control signal cycle, makes N number of pwm signal
Dim signal L can be achieved in combinationinExpressed light adjusting grade；
Step C controls the pwm signal output,
The single control signal cycle is by m (m be positive integer, 1≤m≤N) Tw=p*TdThe pwm signal cycle and N-m
Individual Tw=(p+1) * TdThe pwm signal cycle combine,
The step B can be analyzed to following steps：
Step B1 calculates immediate pwm signal pulsewidth, that is, calculates p value, p=INT ((Lin/LNAX)*LPWM), wherein LMAXFor most
Big light modulation value；
Step B2 calculates m values, m=INT (N* (p+1- (Lin/LMAX)*(Tp/Td))+0.5)；
Step B3 is organized into groups, and determines m Tw=p*TdThe pwm signal cycle and N-m Tw=(p+1) * TdThe PWM letter
The collating sequence in number cycle.
2. PWM light-dimming methods according to claim 1, it is characterised in that the PWM light-dimming methods pass through different Tw (i)
Different t is realized in combinationeffTo show whole light adjusting grades, achievable light adjusting grade is N*LPWM。
3. PWM light-dimming methods according to claim 1, it is characterised in that the step B3 uses following algorithm：
When the middle position i=j*INT (N/m) in pwm signal cycle, then Tw (i)=p*Td, j is 1 positive integer for arriving m, does not meet this
The other positions of equation then Tw (i)=(p+1) * Td。
4. PWM light-dimming methods according to claim 1, it is characterised in that the step B3 uses 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 ＞ 2*m wholes Tw
(i)=(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) whole Tw (i)=p*Td。
5. PWM light-dimming methods according to claim 1 or 2, it is characterised in that the value of each Tw (i) is stored in a storage list
Member, the step C comprise the following steps：
Step C1 is entered as 0 to i；
Step C2 timers perform a timing cycle, and the timing cycle is equal to Tp；
Step C3 i=i+1, Tw (i) is read from the memory cell, the dutycycle of the pwm signal is changed according to Tw (i)；
Step C4 judges whether i is equal to N, equal execution step C1, does not wait performing step C2.
6. PWM light-dimming methods according to claim 5, it is characterised in that after the completion of the step B, in addition to a Tw
(i) write step, Tw (i) write step include：
The step C is interrupted to perform；Each Tw (i) value is write into the memory cell；Step C performs since step C1 again.
7. a kind of PWM light modulating devices, including：
Dim signal interface circuit, receive dim signal；
Drive circuit, outputting drive voltage or driving current, its work period are Td；
Driving power output interface circuit, connection load；
Control circuit, the control circuit receive the dim signal from the dim signal interface circuit, generate control signal,
Export to the drive circuit, it is characterised in that the control circuit includes computing module and pwm signal execution module, the fortune
Calculate module and use any described PWM light-dimming methods of claim 1-6, pwm signal characteristic value is calculated according to the dim signal,
The pwm signal execution module generates control signal according to the pwm signal characteristic value.
8. PWM light modulating devices according to claim 7, it is characterised in that the control circuit also includes memory cell, institute
State pwm signal characteristic value and be stored in the memory cell.
9. PWM light modulating devices according to claim 8, it is characterised in that the pwm signal execution module includes pwm signal
Generator, module for reading and writing, timer, counter, module for reading and writing described in the timers trigger read special from the memory cell
Position the pwm signal characteristic value put and be transferred to the PWM signal generator, the position of the pwm signal characteristic value is by the meter
The numerical value of number device determines that the PWM signal generator generates corresponding pwm signal according to the pwm signal characteristic value, continuously
N number of PWM forms control signal and exported to the drive circuit.
10. according to the PWM light modulating devices described in claim 7,8 or 9, it is characterised in that the pwm signal characteristic value is pulsewidth
Value or dutyfactor value.
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