CN204272462U - A kind of PWM light modulating device - Google Patents
A kind of PWM light modulating device Download PDFInfo
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- CN204272462U CN204272462U CN201420803380.8U CN201420803380U CN204272462U CN 204272462 U CN204272462 U CN 204272462U CN 201420803380 U CN201420803380 U CN 201420803380U CN 204272462 U CN204272462 U CN 204272462U
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Abstract
The utility model provides a kind of PWM light modulating device, control by multiple PWM cycle is combined the brightness of formation control signal to lighting apparatus, after have employed such design, 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 realize the higher and more smooth-going soft dimming effect of light modulation precision.
Description
Technical field
The utility model relates to a kind of 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.As everyone knows, LED has many advantages as light source, and easy 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 also more and more higher to the quality requirement of light modulation.So the light regulating technology of LED needs constantly progressive, the advantage of competence exertion self, complies with the development spring tide of Smart Home.
At present, the most frequently used LED dimming mode is PWM light modulation, and its principle utilizes pwm signal to control Buck/Boost type switching power circuit, according to the dutyfactor value of pwm signal, exports corresponding electric current and voltage value.The switching frequency of Buck/Boost type Switching Power Supply is higher as shown in Figure 1, generally between tens of Khz to hundreds of Khz.The frequency of PWM, generally between hundreds of to a few Khz, carrys out the electric current on/off of control switch 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 when the part Δ t that increases of PWM pulsewidth PWM HIGH time is just in time positioned at the LOW of switching power circuit one-period as shown in Figure 1, the increase of such PWM pulsewidth is exactly invalid for output current, the electric current that LED is exported in rear end is unchanged, can not play actual light modulation effect.And consider the stationary problem of two signals, therefore in existing PWM control program, effective light adjusting grade of PWM equals switching power circuit frequency f
bdivided by PWM frequency f
p(L
eff=f
b/ f
p).
Due to the above-mentioned operation principle that PWM controls, just create a contradiction, if wish to increase the frequency that light adjusting grade just should reduce pwm signal, but when PWM frequency is low, easily there is stroboscopic in LED light source, when taking LED light source with picture pick-up device, can see obvious ripple.Otherwise the raising of PWM frequency, although can reduce described stroboscopic ripple problem, but the negative effect brought is reduction of light adjusting grade number, and then light modulation fineness meeting step-down, cause brightness change in dimming process level and smooth not, visually even can feel light source scintillation.
Summary of the invention
The purpose of this utility model is to solve the problem, and provides a kind of dimming effect more smooth-going soft PWM light modulating device.
The utility model is for realizing above-mentioned functions, and the technical scheme adopted is to provide a kind of PWM light modulating device, comprising:
Dim signal interface circuit, receives dim signal;
Drive circuit, outputting drive voltage or drive current, its work period is T
d;
Driving power output interface circuit, connects load;
Control circuit, described control circuit receives described dim signal from described dim signal interface circuit, generate control signal, export described drive circuit to, it is characterized in that described control circuit comprises computing module and pwm signal Executive Module, described computing module calculates pwm signal characteristic value according to described dim signal, and described pwm signal Executive Module generates control signal according to described pwm signal characteristic value.
Preferably, pwm signal characteristic value circulation described in a group exports by described pwm signal Executive Module, forms described control signal.
Preferably, described control circuit also comprises memory cell, and described pwm signal characteristic value is stored in described memory cell.
Preferably, described pwm signal Executive Module comprises pwm signal generator, module for reading and writing, timer, counter, described timer triggers described module for reading and writing and is transferred to described pwm signal generator from the pwm signal characteristic value of described memory cell reading ad-hoc location, the position of described pwm signal characteristic value is determined by the numerical value of described counter, described pwm signal generator generates corresponding pwm signal according to described pwm signal characteristic value, and the N number of described PWM formation control signal of continuous print exports to described drive circuit.
Preferably, described pwm signal characteristic value is pwm value or dutyfactor value.
Technical scheme provided by the utility model controls by multiple PWM cycle is combined the brightness of formation control signal to lighting apparatus, after have employed such design, 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 realize the higher and more smooth-going soft dimming effect of light modulation precision.
Accompanying drawing explanation
Fig. 1 is the waveform schematic diagram of existing PWM light-dimming method;
Fig. 2 is the structural representation of the PWM light modulating device meeting the utility model preferred embodiment;
Fig. 3 is the flow chart of the utility model PWM light-dimming method embodiment one;
Fig. 4 is the flow chart of the utility model PWM light-dimming method embodiment two;
Fig. 5 is the waveform schematic diagram of the PWM light-dimming method meeting the utility model preferred embodiment.
Embodiment
Below in conjunction with the drawings and specific embodiments, a kind of PWM light modulating device that the utility model proposes is described in further detail.
Please refer to Fig. 2, be the structural representation of a preferred embodiment of a kind of PWM light modulating device that the utility model proposes shown in Fig. 2, this PWM light modulating device comprises 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 that transmits outside and sends control circuit 2 to, is resolved by control circuit 2 pairs of dimming control signals, and produces control signal and be sent to drive circuit 3.This control signal is combined by multiple pwm signals of the particular duty cycle corresponding with dimming control signal, and circulation exports, drive circuit exports corresponding driving voltage current value according to the dutyfactor value of PWM, and exports to corresponding light source by driving power output interface circuit 4.Control circuit 2 can be built by some resolution elements and also can be realized by a MCU.Certain complete light modulating device also can comprise power supply, AC/DC circuit etc. (not shown in Fig. 2), and this can do corresponding configuration according to the practical situation of reality.
The main distinction of the utility model and existing light adjusting system is the processing method of control circuit.In existing PWM light modulating device, general control circuit is by obtaining a single PWM dutyfactor value to the computing of outside dimming control signal, pwm signal generator realizes light modulation according to this duty ratio output pwm signal.But so just there will be a kind of problem as previously mentioned, comprise stroboscopic, light modulation precision inadequate etc.And solution of the present utility model is combined formation control signal multiple PWM cycle, in the utility model preferred embodiment, in a control signal cycle, the duty ratio of each pwm signal is different, as by duty ratio be 3% and 4% pwm signal combination just can obtain the duty ratio 3.5% that originally can not realize.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 of directly being undertaken by pwm signal pulsewidth.In addition, more light adjusting grade can be obtained by the combination of the pwm signal of the various different duty of combination like this.In order to realize such scheme, the structure of control circuit also must do corresponding improvement, first a computing module 21 must be had in control circuit, this computing module 21 is input as dimming control signal, output is the characteristic value of each pwm signal in the control signal cycle, and they put in order, this pwm signal characteristic value can be expressed as the duty ratio of pwm signal, also can represent the pulsewidth becoming pwm signal.Also comprise a pwm signal Executive Module 23 in control circuit, this Executive Module exports the pwm signal cycle of different duty or pulsewidth one by one successively according to the pwm signal characteristic value that computing obtains, and forms final control signal.That is, one group of pwm signal characteristic value circulation exports by pwm signal Executive Module, formation control signal.Computing module 21 can export corresponding pwm signal characteristic value in each pwm signal cycle to pwm signal Executive Module 23, but it is obvious so economical not, therefore in the present embodiment, also comprise a memory cell 22, computing module 21 only carries out once-through operation when detecting that dimming control signal changes, then by operation result write storage unit 22, described memory cell 22 can be a hardware storage device, also can be realized by data structures such as array, stack, queues.And comprise pwm signal generator 2301, module for reading and writing 2302, timer 2 303 and counter 2304 at pwm signal Executive Module 23, timer 2 303 sets the cycle time that timing equals pwm signal, the timing triggering module for reading and writing 2302 that timer 2 303 covers setting performs read-write operation, module for reading and writing 2302 reads the pwm signal characteristic value of sum counter 2304 numerical value opposite position from memory cell 22, and data are sent to pwm signal generator 2301, pwm signal generator 2301 produces the pwm signal meeting this characteristic value according to this characteristic value.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 counter 2304 and is added 1, reset to during N, when counter 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 continuous circulation in control signal cycle achieves brightness adjustment control.
Flow chart below with regard to specific embodiment is described PWM light-dimming method of the present utility model, and Fig. 3 is the flow chart of embodiment one, and Fig. 5 is the oscillogram of a control signal according to the acquisition of the utility model PWM light-dimming method.Here first PWM control general principle and icon are done and illustrate, PWM light-dimming method carrys out on/off drive circuit 3 to load outputting drive voltage or drive current by the high/low level of pwm signal, thus realize different voltage or electric current and export and realize the bright adjustment secretly of light source, pwm signal is pulse signal, and the cycle is T
p, adopt Buck/Boost type switching power circuit as drive circuit in the present embodiment, the cycle of drive circuit 3 is expressed as T
d, in order to realize controlled light modulation pwm signal cycle T
pfor T
dintegral multiple, PWM basis light adjusting grade number L
pWM=T
p/ T
d, the pulsewidth of pwm signal is Tw=p*T
d(p is positive integer, 1≤p≤L
pWM), the difference choosing value of p forms different light modulations and exports.In the present embodiment, as shown in Figure 5, a pwm signal cycle T
pin comprise 5 drive circuit cycle T
d, the pulsewidth of what Tw represented is pwm signal, 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 exports conductively-closed.Can certainly when low level output voltage, shielded signal during high level, this does not affect light-dimming method of the present utility model.As previously mentioned because the output of drive circuit is also impulse form, therefore when Tw is T
p10% to 20% between when changing, the voltage that the time exports can not change, so in this embodiment, in fact attainable light adjusting grade only has 5 grades, L
pWM=5, comprise 1,2,3,4 or 5 driving power cycle T by allowing Tw
drealize 20%, 40%, 60%, 80%, 100% these 5 grades of light adjusting grades, percentage 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 does not want again to increase pwm signal cycle T
p, the method that we adopt is compiled 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 5
c, T
c=N*T
pwe 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, just more multistage light adjusting grade can be produced, Tw (1)=2T in Fig. 5 when adopting different pulsewidth combinations
d, Tw (2)=Tw (3)=Tw (4)=T
d, such control signal cycle T
cin actual effective time t
efffor the pulsewidth sum in pwm signal cycle each in this cycle, t
eff=Tw (1)+Tw (2)+Tw (3)+Tw (4)=5T
d, T
cin comprise altogether 20 T
d, therefore in such control signal cycle T
cthe light output of middle reality is 5T
d/ 20T
dequal 25%, so just achieve the light adjusting grade of originally cannot realize 25%, organizing into groups attainable light adjusting grade by 4 pwm signal cycles is N*L
pWM, the light adjusting grade of 20 grades can be realized in the present embodiment.
A complete PWM light-dimming method flow process as shown in Figure 3, comprises three steps:
Steps A receives dim signal L
in;
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 L
inexpressed light adjusting grade;
Step C realizes the array output formation control signal of pwm signal by pwm signal Executive Module.
That step B calculates in the present embodiment is the Tw (i) in the 1 to the N number of pwm signal cycle, namely calculates each pwm signal cycle T
prespective pwm value, to make the actual effective time t combining out
effdim signal L can be realized
inexpressed light adjusting grade.The Tw (i) in each pwm signal cycle in a control signal can be arbitrary, as long as it meets Tw (i) for T
dintegral multiple, i.e. Tw=p*T as mentioned before
dbut, preferably, the Tw (i) in an each pwm signal cycle difference T at most in a control signal cycle
d, be namely by p*T
d(p+1) * T
dcombine.That is the single control signal cycle is by m (m is positive integer, 1≤m≤N) Tw=p*T
dthe pwm signal cycle and N-m Tw=(p+1) * T
dthe pwm signal cycle combine.Such benefit is that the fluctuation of light modulating device output voltage is not too large, and p*T
d(p+x) * T
dcombination (x be here be more than or equal to 2 integer), can realize by adjusting the quantity of m completely, as in the present embodiment, adopting 1 4T
dthe pwm signal cycle and 3 2T
dpwm signal periodic groups incompatible realize 50% light adjusting grade, can 2 3T be passed through completely
dthe pwm signal cycle and 2 2T
dthe incompatible realization of pwm signal periodic groups, and after adopting, a kind of fluctuation of array output voltage is obviously less than the former, does not have the flicker of obvious light and shade.
As shown in Figure 3, step B refinement can be decomposed into following steps further:
Step B1 calculates immediate pwm signal pulsewidth.Because we adopt p*T
d(p+1) * T
dcombination, that is be combined by two adjacent PWM basis light adjusting grades, the light adjusting grade that we need like this must between these two PWM basis light adjusting grades, here we with the concrete Wave data shown in Fig. 5 for example illustrates, 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 two adjacent light adjusting grades can only be adopted to combine, 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, the i.e. following formula p*T of p demand fulfillment
d≤ (L
in/ L
mAX) * T
p< (p+1) * T
d.Wherein L
mAXfor maximum dimmer value, L
inand L
mAXunit must unify, if input dim signal L
infor brightness value, then L
mAXfor the attainable high-high brightness of system; As inputted dim signal L
infor light adjusting grade, then L
mAXfor the attainable maximum light adjusting grade number of system; As inputted dim signal L
infor the percentage of high-high brightness, then L
mAXbe 1.In other words be that the value of p is for being less than L
inrequired light adjusting grade and immediate value, this step will calculate p value exactly, and by the conversion of formula above, we can draw p=INT ((L
d/ L
mAX) * L
pWM), here INT represents bracket function, because p just can only remove fractional part for integer in time calculating and occur decimal, for actual numerical value, light modulation brightness p=INT ((25%/1) * 5)=INT (1.25)=1 when base level is 5 of 25%, we just can show that the light modulation brightness of 25% should by 1T like this
dand 2T
dcombine.
Step B2 calculates m value.Since the single control signal cycle is by m Tw=p*T
dthe pwm signal cycle and N-m Tw=(p+1) * T
dthe pwm signal cycle combine, so m is also a calculative significant in value.By equation (m*p*T
d+ (N-m) * (p+1) * T
d)/N=(L
in/ L
mAX) * T
pcarry out conversion and can draw m=N* (p+1-(L
in/ L
mAX) * (T
p/ T
b)), but the calculated value that cannot ensure m is in actual applications just in time integer, need to round up to structure, so computing formula is then for conversion into m=INT (N* (p+1-(L
in/ L
mAX) * (T
p/ T
b))+0.5).
Step B3 organizes into groups, and determines m Tw=p*T
dthe described pwm signal cycle and N-m Tw=(p+1) * T
dthe collating sequence in described pwm signal cycle.Since there be m Tw=p*T
dthe pwm signal cycle and N-m Tw=(p+1) * T
dthe pwm signal cycle, so how this is arranged and also needs to be determined by computing these pwm signal cycles.We can first send m Tw=p*T simply
dthe pwm signal cycle, then send N-m Tw=(p+1) * T
dthe pwm signal cycle, but the change of output voltage can be made so obvious, preferably by arrangement 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 position i=j*INT (N/m), then Tw (i)=p*T in the pwm signal cycle
d, j is the positive integer of 1 to m, does not meet other positions then Tw (i)=(p+1) * T of this equation
d.With a concrete numbers illustrated, when in the marshalling be made up of 10 pwm signal cycles, there are 3 Tw=p*T
dpwm signal, so j substitute into 1,2,3, then i equals 1*INT (10/3), 2*INT (10/3), these 3 position distribution of 3*INT (10/3) 3 Tw=p*T
dpwm signal, be respectively the 3rd, the 6th, the 9th, all the other positions are then Tw=(p+1) * T
dpwm signal.The available another kind of algorithm of this step is, original position selects the pulsewidth occupied the minority as initial signal, signal is below spaced one by one until this pulsewidth number occupied the minority is finished, follow-up is all then another kind of pulsewidth, or use numerical value to be above example: 10 pwm signal cycles composition marshallings, as Tw=p*T
dthe signal of pwm signal have 3, Tw=(p+1) * T
dpwm signal have 7, then first Tw (1)=p*T
d, Tw (2) subsequently=(p+1) * T
d, Tw (3)=p*T
d, Tw (4)=(p+1) * T
d, Tw (5)=p*T
dat this moment 3 Tw=p*T
dpwm signal distributed, Tw (6) to Tw (10) is below all just (p+1) * T
dif, Tw=p*T
dsignal occupy the majority, so first Tw (1)=(p+1) * T
dlatter one is p*T
dalternately compile until Tw=(p+1) * T
dsignal use up, all the other are all Tw=p*T
dsignal.That is as m≤N/2, as i≤2*m, then odd bits Tw (i)=p*T
d, even bit Tw (i)=(p+1) * T
d, Tw (i)=(p+1) the * T as i > 2*m
d; As m > N/2, as i≤2* (N-m), then odd bits Tw (i)=(p+1) * T
d, even bit Tw (i)=p*T
d, Tw (i)=p * T as i > 2* (N-m)
d.
As shown in Figure 3, step C also can decompose further in refinement, and the hardware configuration module in our composition graphs 2 specifically explains step C:
Step C1 is 0 to i assignment, and counter 2304 resets;
Step C2 timer 2 303 performs a timing cycle, and described timing cycle equals T
p, T
pbe 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 counter performs and adds an operation, then i=i+1, and module for reading and writing 2302 reads Tw (i) from memory cell 22, and pwm signal generator 2301 is revised the duty ratio of described pwm signal according to Tw (i) and exported this pwm signal;
Step C4 judges whether i equals N, namely judges whether counter 2304 overflows, and then performs step C2 as i=N performs step C1, i ≠ N.
PWM light-dimming method described above is embodiment one of the present utility model, it is first receive dimming information that superincumbent light modulation performs in step, then exports control signal by computing, and this is a basic step.But the light modulation demand of user is uncertain in actual applications, has constantly checked whether light modulation demand, and therefore we this provide embodiment two, as shown in Figure 4.In embodiment two most operating procedure and embodiment one similar, but steps A comprises two sub-steps, namely dimming control signal is detected, dimming control signal and current brightness value are compared, step B is performed as changed, unchanged, continue to detect, that is only need just to perform calculation step when changing in brightness.When system is run first, current brightness value is zero, and just have monochrome information and come as long as open light fixture like this thus enter calculation step, concrete operation method is with embodiment one.And in this example computing complete after execution step C, the particular content of step C is with embodiment one, but unlike, in the present embodiment, step C is just in independent executing state after starting execution, should be step C is a circulation executive program, just constantly exports according to the pwm signal characteristic value of current storage as long as no turning off the light, thus realizes a fixing specific brightness.While step C performs, steps A detects with also keeping, once find that the change of light modulation brightness just starts to perform step B.Due to the pattern of this steps A and step C executed in parallel, Tw (i) write step is also had after step B completes, because need operation result write storage unit 22 after step B completes, and the now data of step C ceaselessly in reading cells, the words of writing direct can produce read-write error, and make the pulsewidth generation great change in follow-up pwm signal cycle cannot realize level and smooth light modulation change when a control signal cycle performs half.Therefore in Tw (i) write step, an interruptive command is first sent, 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 owing to not carrying out counting and read operation, can not change in the pulsewidth of intercourse pwm signal, remain current Tw value output pwm signal.When write completes then reboot step C, namely to bring into operation step C from the starting point P of step C, where is run to regardless of step C before light modulation, now all counter 2304 is reset, and re-start clocked flip, from the 1st position, read Tw (i), and output realizes new light modulation brightness one by one.
To illustrate and describing to the description of the utility model preferred embodiment above, and undesired is the utility model limit or be confined to disclosed concrete form, obviously, many modifications and variations may be made, these modifications and variations may be obvious to those skilled in the art, should be included within the scope of the present invention that defined by appended claims.
Claims (5)
1. a PWM light modulating device, comprising:
Dim signal interface circuit, receives dim signal;
Drive circuit, outputting drive voltage or drive current, its work period is Td;
Driving power output interface circuit, connects load;
Control circuit, described control circuit receives described dim signal from described dim signal interface circuit, generate control signal, export described drive circuit to, it is characterized in that described control circuit comprises computing module and pwm signal Executive Module, described computing module calculates pwm signal characteristic value according to described dim signal, and described pwm signal Executive Module generates control signal according to described pwm signal characteristic value.
2. PWM light modulating device according to claim 1, is characterized in that pwm signal characteristic value circulation described in a group exports by described pwm signal Executive Module, forms described control signal.
3. PWM light modulating device according to claim 1, is characterized in that described control circuit also comprises memory cell, and described pwm signal characteristic value is stored in described memory cell.
4. PWM light modulating device according to claim 3, it is characterized in that described pwm signal Executive Module comprises pwm signal generator, module for reading and writing, timer, counter, described timer triggers described module for reading and writing and is transferred to described pwm signal generator from the pwm signal characteristic value of described memory cell reading ad-hoc location, the position of described pwm signal characteristic value is determined by the numerical value of described counter, described pwm signal generator generates corresponding pwm signal according to described pwm signal characteristic value, the N number of described PWM formation control signal of continuous print exports to described drive circuit.
5., according to the arbitrary described PWM light modulating device of claim 1 to 4, it is characterized in that described pwm signal characteristic value is pwm value or dutyfactor value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420803380.8U CN204272462U (en) | 2014-12-18 | 2014-12-18 | A kind of PWM light modulating device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420803380.8U CN204272462U (en) | 2014-12-18 | 2014-12-18 | A kind of PWM light modulating device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110225615A (en) * | 2019-05-31 | 2019-09-10 | 惠州华阳通用智慧车载系统开发有限公司 | A kind of LED background light brightness uniformity adjusting method and device |
-
2014
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110225615A (en) * | 2019-05-31 | 2019-09-10 | 惠州华阳通用智慧车载系统开发有限公司 | A kind of LED background light brightness uniformity adjusting method and device |
| CN110225615B (en) * | 2019-05-31 | 2021-06-25 | 惠州华阳通用智慧车载系统开发有限公司 | Method and device for adjusting brightness consistency of LED background light |
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