CN111511071A - PWM signal correction method, L ED lighting device - Google Patents
PWM signal correction method, L ED lighting device Download PDFInfo
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Abstract
The invention relates to a PWM signal correction method and an L ED lighting device, wherein the PWM signal correction method is used for a L ED lighting device comprising n paths of PWM driving circuits, and comprises the following steps of measuring the current I when the maximum value of the output current in the ith path of PWM driving circuit is obtainedimaxAnd current I at current minimumiminWherein i is 1,2, … n; determining the corresponding current IimaxPWM value of (1), denoted as PWMimaxDetermining the corresponding current IiminPWM value of (1), denoted as PWMimin(ii) a Determining dimming whole-course time T and PWM duty ratio refreshing time T; according to the PWMimax、PWMiminT, t calculating a PWM adjustment step PWMistep; according to the PWMimax、PWMimin、PWMistep corrects the PWM signal input into the ith PWM driving circuit. According to the invention, the PWM output signals of each PWM driving loop are synchronously adjusted according to the maximum value and the minimum value of PWM in each PWM driving loop, and uniform synchronous control dimming of each loop can be realized.
Description
Technical Field
The present invention relates to lighting devices, and more particularly, to a PWM signal correction method and an L ED lighting device using the same.
Background
Light emitting diodes (L ED) have the advantages of energy conservation and environmental protection as lighting sources, and are widely used. L ED dimming devices can be used in L ED lighting systems to provide desired brightness according to different times, different locations and specific needs of users. L ED dimming devices can not only reduce energy consumption, but also provide a comfortable lighting environment.
However, with the increasing of L ED driving schemes, the precision of PWM dimming and the requirement of dimming interval will change accordingly according to the different driving IC chips, if only one set of MCU control program is used to perform PWM dimming control, the situation of jump will occur during dimming, and especially the jump will be obvious at low brightness.
The three-way L ED driving circuit for a L ED lighting device shown in fig. 1 does not have a consistent driving current output waveform for each driving circuit when the PWM value is changed to adjust the PWM value from 0.1% to 100% to adjust the PWM value to a L ED load as time T increases, for the first driving circuit, when the duty ratio of the PWM signal from the MCU increases from 0.1% to 25%, as shown by current waveform L in fig. 1, the brightness (i.e., I-current ratio) of the L ED load in the first driving circuit has already changed from 5% to 100%, and when the PWM signal duty ratio is adjusted upward no matter how much after 25%, the brightness of the L ED load remains substantially unchanged, so that the overall change time of the brightness adjustment of the lighting device is relatively short, for the second driving circuit, when the duty ratio of the PWM signal increases from 0.1% to 50%, as shown by current waveform L in fig. 1, the brightness of the second driving circuit does not change from L% to 100%, and when the PWM signal does not change from 0.1% to 50%, as the PWM signal does not change from 5% to 5% and when the PWM signal does not change from 0.1% to 5% and when the PWM signal reaches the duty ratio of the PWM signal reaches the threshold of the PWM signal reaches the threshold of the PWM signal is increased from 0.1, the threshold of the PWM signal is equal to 5% and the threshold of the PWM signal is equal to 5% as shown by 7% after the threshold value of the PWM signal is increased, the threshold of the threshold value of the PWM signal is increased, the PWM signal is equal to.
In order to obtain the ideal dimming curve shown in fig. 1 (as shown in the current waveform curve L4 in fig. 1, the ideal dimming effect of the designer is that the I-current ratio is uniformly changed and the time is substantially synchronized when the PWM duty cycle signal is changed), so as to avoid the uncomfortable dimming caused by the unsmooth dimming curve, the designer needs to adjust the lighting circuit, but this approach is inefficient in design, and if a lighting device involves dimming and dimming of multiple L ED circuits, it is necessary to make special adjustments to each circuit at the same time to ensure that the loads in the multiple L ED circuits can achieve smooth dimming, and the process universality is poor.
Disclosure of Invention
The present invention provides a PWM signal modification method with smoother and softer dimming effect, and an L ED lighting device, so as to solve the above-mentioned drawbacks in the prior art.
The invention provides a PWM signal correction method, which is used in an L ED lighting device comprising n PWM driving loops, wherein n is an integer and is more than or equal to 1, and the method comprises the following steps of S1, measuring the current I when the maximum value of the output current in the ith PWM driving loop is obtainedimaxAnd current I at current minimumiminWherein i is 1,2, … n; s2, determining the current IimaxPWM value of (1), denoted as PWMimaxDetermining the corresponding current IiminPWM value of (1), denoted as PWMimin(ii) a S3, determining dimming whole time T and PWM duty ratio refreshing time T; s4, according to the PWMimax、PWMiminT, t calculating a PWM adjustment step PWMistep; s5, according to the PWMimax、PWMimin、PWMistep corrects the PWM signal input into the ith PWM driving circuit.
Further, in step S4, a PWM adjustment step PWM is calculated using a linear equation or a correction curve equationistep。
Further, PWMistep＝(PWMimax-PWMimin)/N，N＝T/t。
Further, the steps S1, S2 are completed in the learning correction mode.
Further, in step S1, detecting a current value in the i-th PWM driving loop in real time, determining that the output current of the i-th PWM driving loop reaches a maximum value after detecting that the current in the i-th PWM driving loop is not increased in a forward direction and the continuous change of the current value does not exceed a preset first threshold value for a plurality of times, and taking an average value of a plurality of PWM values during the plurality of times of measurement as the PWMimax。
Further, the first threshold value is 100% ± 5% of the maximum current value.
Further, in step S1, the current value output by the i-th PWM driving circuit is detected in real time, the current value detected each time is compared with the current value detected last time, and when the maximum current reduction is detected, the PWM value corresponding to the current value detected last time is taken as the PWMimin。
Further, T is a prescribed value selected from the range of 1 to 3 seconds, and T is a value obtained by dividing said T by a prescribed accuracy value.
The L ED lighting device is characterized by comprising a control unit, n PWM driving loops and n current detection circuits, wherein n is an integer and is not less than 1, the n current detection circuits are used for detecting current values output by the n PWM driving loops in real time, and the control unit measures current I when the ith PWM driving loop outputs the maximum current value according to the current value detected by the current detection circuits in real timeimaxAnd current I at current minimumiminDetermining the corresponding current IimaxAnd is recorded as PWMimaxDetermining the corresponding current IiminAnd is recorded as PWMiminDetermining the whole dimming time T and the PWM duty ratio refreshing time T, and according to the PWMimax、PWMiminT, t calculating a PWM adjustment step PWMistep and according to said PWMimax、PWMimin、PWMistAnd ep, correcting the PWM signal input into the ith PWM driving circuit, wherein i is 1,2 and … n.
Further, the control unit calculates PWM regulating step length PWM by adopting a linear equation or a correction curve equationistep。
Further, PWMistep＝(PWMnmaxPWMimax-PWMimin)/N，N＝T/t。
Further, the L ED lighting device comprises a learning correction mode, and the control unit obtains I in the learning correction modeimax、Iimin，PWMimaxAnd PWMimin。
Further, the L ED lighting device further comprises an instruction receiving circuit, wherein the instruction receiving circuit receives a control instruction for entering the self-learning correction mode, which is input by a user, and the learning correction mode is entered.
Further, the instruction receiving circuit is selected from one of a remote controller, a Bluetooth module, a touch device comprising touch keys and a wireless transmission module.
Further, the control unit is a main control MCU.
Further, in the learning correction mode, a 16-bit precision timer is used for generating a PWM (pulse width modulation) adjusting step length used by a user when the user adjusts light upwards/downwards through the instruction receiving circuit.
Further, when the control unit detects that the output current of the ith PWM driving circuit is not increased in the forward direction for multiple times and the continuous change of the current value does not exceed a preset first threshold value, the control unit judges that the output current of the ith PWM driving circuit reaches the maximum value, and takes the average value of multiple PWM values during multiple measurements as the PWM valueimax。
Further, the first threshold value is 100% ± 5% of the maximum current value.
Further, the control unit compares the current value detected each time with the current value detected last time, and when the maximum current reduction amplitude is detected, the PWM value corresponding to the current value detected last time is taken as the PWMimin。
Further, T is a prescribed value selected from the range of 1 to 3 seconds, and T is a value obtained by dividing said T by a prescribed accuracy value.
Furthermore, the ith PWM driving circuit is composed of a driving IC chip and an L ED load circuit, and is configured to receive the PWM signal output by the control unit to perform dimming driving.
Further, in the learning correction mode, each time a user performs upward/downward dimming through the instruction receiving circuit, the PWM adjustment step size is 0.1%.
Another aspect of the present invention provides an L ED lighting device, which executes the PWM signal correction method to generate a corrected PWM signal.
According to the technical scheme of the invention, the maximum value and the minimum value of PWM of each PWM driving loop are obtained, the PWM duty ratio regulating step length is calculated by utilizing the maximum value and the minimum value of the PWM, and the PWM output signal of each PWM driving loop is regulated according to the parameters, so that the uniform synchronous control of each loop can be realized.
Drawings
Fig. 1 is a dimming graph of a prior L ED lighting device;
fig. 2 is a schematic circuit configuration diagram of an L ED lighting device according to an embodiment of the invention;
FIG. 3 is a schematic diagram of an instruction receiving circuit according to an embodiment of the invention;
FIG. 4 is a flow chart of entering a modified learning mode according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of PWM duty cycle in self-learning correction mode according to an embodiment of the present invention;
FIG. 6 is a flow chart of a method of step size correction for n PWM drive loops in L ED lighting devices;
FIG. 7 is a schematic diagram of PWM duty cycle adjustment for n PWM drive loops in L ED lighting devices;
fig. 8 is a schematic diagram of a specific example of PWM duty cycle adjustment of a PWM drive loop in an L ED lighting device.
Detailed Description
The control unit can be built by a plurality of separate elements or can be realized by a microcontroller (MCU control circuit). in a preferred embodiment of the invention, the control unit is an MCU main processing module.
Fig. 2 is a schematic circuit diagram of an L ED lighting device according to an embodiment of the invention.
As shown in fig. 2, the L ED lighting device includes an MCU main processing module 1, an instruction receiving circuit 2, and at least one PWM driving circuit, wherein for each PWM driving circuit, the L ED lighting device is provided with a corresponding current detection circuit.
The MCU main processing module 1 analyzes the instruction receiving signal received by the instruction receiving circuit 2, compares the current sampled by the current detecting circuit, and identifies the maximum value of the current in each PWM driving circuit and the PWM threshold value PWM when the maximum value of the current is stablemaxAnd PWM threshold value PWM when current is minimum and stableminAnd through algorithm processing, the corrected PWM data is output, so that the output of the multi-path PWM driving loop in the L ED lighting device can be kept synchronous.
In the present embodiment, the L ED lighting device includes a first PWM driving loop 3 and a second PWM driving loop 4. correspondingly, the L ED lighting device includes a first current detection circuit 5 for detecting the current in the first PWM driving loop 3 in real time and a second current detection circuit 6 for detecting the current in the second PWM driving loop 4 in real time.
Fig. 3 is a schematic diagram of a command receiving circuit according to an embodiment of the present invention, which is a remote controller. The remote controller can be any existing remote controller, and only the remote controller comprises at least three input parts, such as three keys. As shown in fig. 3, the remote controller includes a learning mode key 7, an up dimming key 8, and a down dimming key 9. The user enters a self-learning correction mode instruction by using the learning mode key 7, and the up dimming key 8 and the down dimming key 9 perform operations of up dimming (up) and down dimming (down), respectively. The up and down dimming keys can be operated by single pressing or continuous pressing, the PWM span of each step, i.e. the duty cycle change step length, is fixed and can be generated by a 16bit precision timer, in a preferred embodiment, the PWM duty cycle change step length is 0.1% when the up dimming key or the down dimming key is pressed once, and the precision and the span can be modified and defined, and can be set according to different application occasions. Meanwhile, the dimming duration time T can be set according to different application occasions.
A user sends a learning mode entering instruction to an instruction receiving circuit 2 by using a learning mode key 7, the instruction receiving circuit 2 sends the learning mode entering instruction to an MCU (microprogrammed control Unit) main processing module 1, the MCU main processing module 1 controls the L ED lighting device to enter a self-learning correction mode, PWM (pulse-Width modulation) driving loops 3 and 4 receive PWM (pulse-Width modulation) signals sent by the MCU main processing module, dimming driving is carried out according to the PWM signals, meanwhile, the MCU main processing module 1 starts a current acquisition function, PWM real-time data and acquired current data are analyzed and processed, a first current detection circuit 5 carries out real-time detection on current in the first PWM driving loop 3, a second current detection circuit 6 carries out real-time detection on current in the second PWM driving loop 4, and therefore the maximum value of current of each driving loop and stable PWM threshold value PWM (pulse-Width modulation) are obtainedmaxPWM threshold value PWM when value and current are minimum and stableminThe value is obtained. Restarting after learning is finished, and prompting the user to learn through light flickerAnd finishing the calculation of the acquired data.
FIG. 4 is a flow chart of a modified learning mode, the method comprising the steps of:
step S401: starting;
if the MCU main processing module 1 receives a learning mode entering instruction sent by a user through pressing a learning mode key on a remote controller, the MCU main processing module 1 controls the L ED lighting device to enter a self-learning correction mode and enter a step S403, otherwise, the MCU main processing module enters a step S409 and still keeps a normal mode;
step S403: starting AD current detection, and then entering step S404;
step S404: judging whether a user presses an upward dimming key on the remote controller, if so, entering a step S405, otherwise, entering a step S410;
step S405: the PWM duty is increased by a predetermined step size, and the process proceeds to step S406;
step S406: starting a current acquisition function, detecting the current in the first PWM driving loop 3 in real time by the first current detection circuit 5, detecting the current in the second PWM driving loop 4 in real time by the second current detection circuit 6, transmitting the ratio of the current value detected by each current detection circuit to the rated maximum output current, namely the current ratio, to the MCU main processing module 1, storing the current ratio of each time point and the corresponding PWM value in an internal ROM by the MCU main processing module 1 in real time, and then entering the step S407;
step S407: the MCU main processing module 1 analyzes and processes the PWM real-time data and the acquired current ratio data, judges whether each PWM driving loop is in a stable current ratio maximum state, if so, enters a step S408, otherwise, returns to the step S404;
step S408: the MCU main processing module 1 is provided with ImaxIdentifying the mark, recording the corresponding PWM value when each path of PWM driving loop is in the maximum current ratio and the stable state, and recording as PWMmaxA value;
step S409, the L ED lighting device is in a normal mode;
step S410: judging whether the user presses a downward dimming key on the remote controller, if so, entering step S411, otherwise, entering step S418;
step S411: the PWM duty is decreased by a predetermined step size, and the process proceeds to step S412;
step S412: starting a current acquisition function, detecting the current in the first PWM driving loop 3 in real time by the first current detection circuit 5, detecting the current in the second PWM driving loop 4 in real time by the second current detection circuit 6, transmitting the ratio of the detected current value to the rated maximum output current, namely the current ratio, to the MCU main processing module 1, storing the current ratio and the corresponding PWM value of each time point in the internal ROM by the MCU main processing module 1 in real time, and then entering the step S413;
step S413: the MCU main processing module 1 analyzes and processes the PWM real-time data and the acquired current ratio data, judges whether each PWM driving loop is in a state of minimum and stable current ratio, if so, enters a step S414, otherwise, returns to the step S404;
step S414: the MCU main processing module 1 is provided with IminIdentifying the mark, recording the corresponding PWM value when each PWM driving loop is in the stable current ratio minimum state, and recording as PWMminA value;
step S415: to ImaxAnd IminThe identification bits are judged whether all are 1, namely, the PWM of each PWM driving loop is judgedmaxValue, PWMminWhether the values are recorded with the effect is finished, if yes, the step S416 is carried out, and if not, the step S404 is carried out;
step S416: prompting the user to learn and obtain data through light flicker, and completing calculation;
l ED lighting device restarts;
step S418: and (6) ending.
Fig. 5 is a waveform diagram illustrating a current ratio in the self-learning correction mode. In fig. 5, the second vertical axis on the right side is the current ratio, and the first vertical axis on the left side is labeled as the real-time PWM value corresponding to the current ratio waveform for convenience.
As shown in fig. 5, as the user continuously presses the up-dimming button, the PWM value correspondingly increases, but since the increasing trend of the brightness (i.e. I current ratio) of the L ED load is not completely consistent with the increasing trend of the PWM value (the variation curve of the PWM value is not shown in fig. 5), when the current ratio outputted from the PWM driving circuit reaches the maximum value, even if the up-dimming button is pressed again, that is, the PWM value is increased (i.e. the DE stage shown in fig. 5), the current ratio does not continuously increase any more, and the PWM value corresponding to the current ratio at this time is defined as the PWM value corresponding to the PWM valuemaxThe value is obtained. However, due to the existence of discrete errors, when the current ratio is detected to be the maximum value of the current ratio, the deviation of the set current ratio meets a certain error range, and then the corresponding PWM value is regarded as being at the maximum value, and the PWM driving loop can be confirmed to be in a stable maximum state of the current ratio by continuously fluctuating for a plurality of times in the error range, namely, the PWM value at the moment can be determined to be the PWM valuemaxThe value is obtained. For example, when it is detected that the current ratio in the PWM driving loop is not continuously increased in the forward direction for a plurality of times and the continuous change of the current ratio does not exceed a certain preset first threshold, it is determined that the current ratio reaches the maximum value, and the average value of the corresponding PWM values at the last measurement times is taken as the PWMmaxThe value is obtained. In a preferred embodiment, the first threshold may be 100% ± 5% of the maximum current value.
Similarly, as the user continuously presses the down dimming button in the on state, the PWM value correspondingly decreases, and similarly, since the decreasing trend of the brightness of the L ED load is not completely synchronous with the decreasing trend of the PWM value, various conditions may occur in the low current stage, as shown in fig. 5, between the line segment AB point, even if the up dimming button is pressed or the down dimming button is pressed, because the MCU main processing module outputs the PWM value but the current ratio does not change, the I current ratio is not output all the time, that is, the L ED lighting device is in the off state, and in the curve segment BC, for example, when the up dimming button is pressed, the I current ratio suddenly starts to light the L ED lighting device with the increasing output of the PWM value, the curve is jagged and not smooth, so that the selection can be made to be in the on stateThe current ratio at the point C (i.e. the current ratio before the point where the current detection has the maximum amplitude reduction) is taken as the minimum current ratio, and the corresponding stable PWM threshold value at the time is taken as the PWMminAnd (6) recording the value. More specifically, it may be preferable, for example, that a current ratio detected after each downward dimming key is pressed is compared with a current ratio detected last time, and when the current ratio is detected to be decreased maximally, a PWM value corresponding to the current ratio detected last time is taken as PWMmin。
Fig. 6 is a flowchart of a method for PWM step correction adjustment of n PWM drive loops in an L ED lighting device, the method comprising the steps of:
s601: obtaining PWM of each PWM driving loop through learning modemaxAnd PWMminRecorded as PWM, respectivelyimaxAnd PWMimin；
S602: setting dimming whole-course time T and PWM duty ratio refreshing time T, wherein the whole-course time T can be selected and set to be proper time, preferably 2 seconds, between 1 and 3 seconds according to the environment and the specific situation of the lighting device and according to the adaptive effect experiment of human eyes. T is primarily determined by selectively dividing the full time T into, for example, 1/1000, according to the required accuracy of the PWM variation, and in the present embodiment, T may preferably be 2 ms when the full time T is 2 seconds.
S603: calculating PWM regulating step PWMstep of each PWM driving circuit and recording as PWMistep, said PWMistep＝(PWMimax-PWMimin) N is T/T, and N is the number of PWM duty ratio refreshing sections; those skilled in the art will appreciate that although a linear relationship is used for the calculation, a correction curve or other optimized curve equation may be used for the calculation.
S604: the MCU main processing module 1 is used for processing the PWMiAnd step adjusts the PWM signals of each PWM driving circuit, respectively generates corresponding PWM control signals and sends the PWM control signals to each PWM driving circuit.
Fig. 7 is a schematic diagram of PWM duty cycle adjustment of n PWM driving loops in L ED lighting device according to an embodiment of the present invention.
In fig. 7, the horizontal axis is time, the first vertical axis on the left side is the PWM dimming signal value output by the MCU main processing module 1, and the second vertical axis on the right side is the current ratio output by each PWM driving circuit, which is the ratio of the current value actually output by the PWM driving circuit to the rated maximum output current.
As shown in fig. 7, when the PWM value is changed to adjust from 0.1% to 100% to dim L ED loads as the dimming whole time T increases, the line segment O is a signal curve of the PWM dimming signal sent by the MCU main processing module 1, the curve Q1 is a graph of the current ratio output by the first PWM driving loop, and the curve P1 is a graph of the current ratio output by the second PWM driving loop, as can be seen from fig. 7, at this time, the outputs of the two PWM driving loops are not synchronized with the PWM dimming signal.
According to the detection result of the current detection circuit, when the output in the first PWM driving circuit is at the maximum value of the current ratio and the minimum value of the current ratio, the PWM duty ratios corresponding to the maximum PWM duty ratio and the minimum PWM duty ratio are respectively PWM1maxAnd PWM1minAnd recording the PWM duty ratios of the output current ratio maximum value and the output current ratio minimum value in the second PWM driving circuit as PWM2maxAnd PWM2minAnd recorded, in this embodiment, PWM1minAnd PWM2minAre all equal to PWMmin. And then, the previous PWM output signal is adjusted according to the parameters, the adjustment range and the accuracy are still in the initial basic setting, and only the interval of PWM output is adjusted according to the detection result.
The calculated PWM regulating step length is as follows: step-size-adjusting PWM of first PWM driving circuit1step＝(PWM1max–PWM1min) N, where N is T/T, in this embodiment, T still continues to use the previous dimming whole time T, and T is the PWM duty cycle refresh time; step-size-adjusting PWM of second PWM driving circuit2step＝(PWM2max–PWM2min)/N。
Adjusting PWM output signals of each PWM driving circuit according to the calculation result, wherein the maximum value of the PWM duty ratio of each PWM output signal is PWMimaxMinimum value being PWMiminThe PWM duty ratio refreshing time is t, and the PWM duty ratio regulating step length is PWMistep。
As shown in FIG. 7, the line segment O1 is in accordance with PWM1step PWM duty ratio regulating step length, and PWM value input into first PWM driving circuit is regulated from PWM1minRegulating to PWM1maxIn this case, the signal curve of the PWM dimming signal, the curve Q2 is the current ratio graph of the output of the first PWM driving loop corresponding to the curve, and the segment O2 is according to the PWM2step PWM duty ratio regulating step length, and PWM value input into second PWM driving circuit is regulated from PWM2minRegulating to PWM2maxIn the meantime, a signal curve of the PWM dimming signal, curve P2, is a graph of the current ratio output by the second PWM driving loop corresponding to the signal curve, and as can be seen from fig. 7, the current ratios of the two PWM driving loops both change synchronously with the input PWM value, and are uniform and smooth, and the synchronous change of the outputs of the two PWM driving loops is also realized.
A specific example is substituted below to specifically describe one of the PWM driving circuits.
For ease of notation, the subscript i labels that distinguish between different PWM drive loops are omitted below.
In this example, when the full time T is 2 seconds, the PWM duty refresh time T is 2 milliseconds, and N is T/T is 2000/2 is 1000, that is, the PWM slave PWMminTo PWMmaxDividing into 1000 sections; PWM through self-learning mode detectionmin＝7％，PWM max75%, the PWM duty cycle adjustment step PWMstep is (PWM)max-PWMmin) And/1000 is 0.068. Of PWM dimming signalsThe signal curve and the current ratio curve of the PWM driving circuit are shown in fig. 8, and are not described herein again.
According to the technical scheme of the invention, through a self-learning mode, PWM values, namely PWM values, which correspond to PWM driving loops when the output current ratio reaches the maximum or the minimum respectively, are obtained and recordedmaxValue sum PWMminValue and using the PWMmaxValue sum PWMminAnd calculating the PWM duty ratio adjusting step length, and adjusting the PWM output signal of each PWM driving loop according to the parameters, so that smooth and uniform synchronous control of each loop can be realized.
In the present embodiment, the PWM signal correction method according to the present invention is described using a current ratio, that is, a ratio of a real-time current value output from the PWM drive circuit to a rated maximum output current. Those skilled in the art will appreciate that the present invention may be implemented as well by detecting the absolute maximum or minimum of the real-time current value output by the PWM drive loop and determining the PWM value corresponding to the absolute maximum and minimum.
It should be understood by those skilled in the art that the present embodiment has been described with respect to the first PWM driving circuit 3 and the second PWM driving circuit 4, but it is possible to implement the present invention and obtain the corresponding technical effects in the case of only one PWM driving circuit. And will not be repeated herein.
In addition, it will be appreciated by those of ordinary skill in the art that in the embodiments described above, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solutions claimed in the claims of the present application can be basically implemented without these technical details and various changes and modifications based on the above-described embodiments. Accordingly, in actual practice, various changes in form and detail may be made to the above-described embodiments without departing from the spirit and scope of the invention.
Claims (23)
1. A PWM signal correction method is used in an L ED lighting device comprising n PWM driving loops, wherein n is an integer and n ≧ 1, and the method comprises the following steps:
s1, measuring the current I when the output current in the ith PWM driving loop is maximumimaxAnd current I at current minimumiminWherein i is 1,2, … n;
s2, determining the current IimaxPWM value of (1), denoted as PWMimaxDetermining the corresponding current IiminPWM value of (1), denoted as PWMimin；
S3, determining dimming whole time T and PWM duty ratio refreshing time T;
s4, according to the PWMimax、PWMiminT, t calculating a PWM adjustment step PWMistep；
S5, according to the PWMimax、PWMimin、PWMistep corrects the PWM signal input into the ith PWM driving circuit.
2. The PWM signal modification method according to claim 1,
in step S4, a linear equation or a correction curve equation is used to calculate the PWM adjustment step PWMistep。
3. The PWM signal modification method according to claim 1 or 2,
PWMistep＝(PWMimax-PWMimin)/N，N＝T/t。
4. the PWM signal modification method according to claim 1 or 2,
the steps S1, S2 are completed in the learning correction mode.
5. The PWM signal modification method according to claim 1 or 2,
in step S1, detecting the current value in the ith PWM driving loop in real time, and when it is detected that the current in the ith PWM driving loop is not increased in the forward direction for multiple times and the continuous change of the current value does not exceed the preset valueAfter the first threshold value, the output current of the ith path of PWM driving loop is judged to reach the maximum value, and the average value of a plurality of PWM values in the multiple times of measurement is taken as the PWMimax。
6. The PWM signal modification method according to claim 5,
the first threshold value is 100% ± 5% of the maximum current value.
7. The PWM signal modification method according to claim 1 or 2,
in step S1, the current value output by the i-th PWM driving circuit is detected in real time, the current value detected each time is compared with the current value detected last time, and when the maximum current drop is detected, the PWM value corresponding to the current value detected last time is taken as the PWMimin。
8. The PWM signal modification method according to claim 1 or 2,
t is a defined value selected between 1 and 3 seconds, and T is the value obtained by dividing said T by a defined precision value.
9. An L ED lighting device, characterized in that,
comprises a control unit, n PWM driving loops and n current detection circuits, wherein n is an integer and is more than or equal to 1,
the n current detection circuits are used for detecting the current values output by the n PWM driving circuits in real time,
the control unit measures the current I when the ith PWM driving loop outputs the maximum current value according to the current value detected by the current detection circuit in real timeimaxAnd current I at current minimumiminDetermining the corresponding current IimaxAnd is recorded as PWMimaxDetermining the corresponding current IiminAnd is recorded as PWMiminDetermining the whole dimming time T and the PWM duty ratio refreshing time T, and according to the PWMimax、PWMiminT, t calculationPWM regulating step length PWMistep and according to said PWMimax、PWMimin、PWMistep corrects the PWM signal input into the ith PWM driving circuit, wherein i is 1,2, … n.
10. L ED lighting device as claimed in claim 9,
the control unit calculates PWM (pulse-Width modulation) regulating step length PWM by adopting a linear equation or a correction curve equationistep。
11. L ED lighting device as claimed in claim 9 or 10,
PWMistep＝(PWMnmaxPWMimax-PWMimin)/N，N＝T/t。
12. l ED lighting device as claimed in claim 9 or 10,
the L ED lighting device comprises a learning correction mode, and the control unit obtains I in the learning correction modeimax、Iimin，PWMimaxAnd PWMimin。
13. L ED lighting device as claimed in claim 9 or 10,
the L ED lighting device further comprises an instruction receiving circuit, wherein the instruction receiving circuit receives a control instruction for entering the self-learning correction mode and entering the learning correction mode, wherein the control instruction is input by a user.
14. The L ED lighting device of claim 13,
the instruction receiving circuit is selected from one of a remote controller, a Bluetooth module, a touch device comprising touch keys and a wireless transmission module.
15. L ED lighting device as claimed in claim 9 or 10,
the control unit is a main control MCU.
16. The L ED lighting device of claim 12,
in the learning correction mode, a 16-bit precision timer is used for generating a PWM (pulse width modulation) adjusting step length used when a user adjusts light upwards/downwards through the instruction receiving circuit each time.
17. L ED lighting device as claimed in claim 9 or 10,
when the control unit detects that the output current of the ith PWM driving circuit is not increased in the positive direction for multiple times and the continuous change of the current value does not exceed a preset first threshold value, the control unit judges that the output current of the ith PWM driving circuit reaches the maximum value, and takes the average value of multiple PWM values during multiple times of measurement as PWMimax。
18. The L ED lighting device of claim 17,
the first threshold value is 100% ± 5% of the maximum current value.
19. L ED lighting device as claimed in claim 9 or 10,
the control unit compares the current value detected each time with the current value detected last time, and when the maximum current reduction amplitude is detected, the PWM value corresponding to the current value detected last time is taken as PWMimin。
20. L ED lighting device as claimed in claim 9 or 10,
t is a defined value selected between 1 and 3 seconds, and T is the value obtained by dividing said T by a defined precision value.
21. L ED lighting device as claimed in claim 9 or 10,
the ith PWM driving circuit is composed of a driving IC chip and an L ED load circuit and is used for receiving the PWM signal output by the control unit to carry out dimming driving.
22. The L ED lighting device of claim 17,
in the learning correction mode, each time a user performs upward/downward dimming through the instruction receiving circuit, the PWM adjustment step size is 0.1%.
23. An L ED lighting device, performing the PWM signal modification method of any one of claims 1-8, generating a modified PWM signal.
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