CN111836432B - Linear constant-current driving circuit, chip and method for PWM dimming - Google Patents
Linear constant-current driving circuit, chip and method for PWM dimming Download PDFInfo
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- CN111836432B CN111836432B CN201910236606.8A CN201910236606A CN111836432B CN 111836432 B CN111836432 B CN 111836432B CN 201910236606 A CN201910236606 A CN 201910236606A CN 111836432 B CN111836432 B CN 111836432B
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Abstract
The invention discloses a linear constant current driving circuit, a chip and a method for PWM dimming, wherein the circuit comprises: the decoding module is used for decoding N parts of dimming gear codes modulated into the power supply from the power supply; the PWM generating module is used for generating N paths of PWM signals corresponding to the N parts of decoded dimming gear codes after a power supply source recovers to a normal power supply stage from a stage of modulating the dimming gear codes; each constant current driving module is used for carrying out constant current driving on a light emitting load connected to the constant current driving module when the constant current driving module is conducted; each PWM switch module is used for adjusting the conduction state of a corresponding constant current driving module based on the corresponding path of PWM signal so as to control the magnitude of driving current for driving the luminous load; the invention can solve the problems of PWM dimming by directly utilizing VCC in the prior art, can realize the effect that one chip is simultaneously connected with N paths of loads, and can realize the independent control of N paths of luminous loads.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a linear constant current driving circuit, a chip and a method for PWM dimming.
Background
Referring to fig. 1 and 2, the conventional soft light strip LED driving chip works as follows: each LED occupies one chip, VCC generates an internal power supply VDD through LDO, an error amplifier EA samples the voltage of a resistor Rcs and controls the grid of a MOS transistor M1, so that constant current is realized, and the current Iout flowing through the resistor Rcs is equal to Vref/Rcs; the PWM dimming function is realized by superposing the PWM signal on the VCC. To illustrate with VCC equal to 24V (the voltage range of VCC is not particularly limited in the present invention), as shown in fig. 3, when VCC is equal to 0, each LED current is 0, and when VCC is equal to 24V, each LED current is I equal to Vref/Rcs.
The disadvantages and shortcomings of the prior art are as follows:
1) because the PWM dimming is directly carried out through VCC voltage, when each time of PWM is switched from 0 to 1, a chip needs to be restarted to generate time delay, and the distortion is generated by overhigh PWM frequency; and because the VCC route has heavy current, too high PWM frequency can produce very big burr, influences system stability and chip life-span. The two factors limit that the PWM frequency cannot be too high, and the PWM frequency is 1-4 KHz generally, so that noise and stroboscopic phenomena are easy to generate; then, PWM dimming is performed by VCC, and the total current Iout _ all has a pulse waveform, resulting in a large ripple.
2) Each path of LED needs one chip, the structure is complex, and the cost is high;
3) the behavior of each path of LED is consistent, and more complex functions cannot be realized.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a linear constant current driving circuit, a chip and a method for PWM dimming, aiming at the problems generated by directly using VCC voltage to perform PWM dimming in the prior art and the defect that a chip can only support one LED lamp.
The technical scheme adopted by the invention for solving the technical problem is as follows: constructing a linear constant current driving circuit for PWM dimming, the circuit comprising:
the decoding module is used for decoding N parts of dimming gear codes modulated into the power supply from the power supply, wherein N is a positive integer;
the PWM generating module is used for generating N paths of PWM signals corresponding to the N parts of decoded dimming gear codes after the power supply source recovers to a normal power supply stage of unmodulated dimming gear codes from a stage of modulating the dimming gear codes;
each constant current driving module is used for carrying out constant current driving on a light emitting load connected to the constant current driving module when the constant current driving module is conducted;
and the N PWM switch modules correspond to the N paths of PWM signals and the N constant current driving modules respectively one by one, and each PWM switch module is used for adjusting the conduction state of a corresponding constant current driving module based on the corresponding path of PWM signal so as to control the magnitude of the driving current for driving the luminous load.
Preferably, the power supply source is a positive input power VCC of the whole driving circuit or a negative input power GND of the whole driving circuit;
each part of the dimming gear code corresponds to a binary level, and the binary level is modulated into the power supply source in a mode of being superposed with the voltage of the power supply source.
Preferably, the decoding module is configured to decode, after monitoring handshake code information in a power supply source, N parts of dimming shift codes modulated into the power supply source from the power supply source.
Preferably, the PWM generation module includes:
a clock unit for generating a standard clock signal;
and the PWM unit is used for delaying corresponding time and then generating a corresponding path of PWM signals by using the clock signal according to each path of N paths of PWM signals when the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, and the duty ratio of each path of PWM signals is related to a corresponding dimming gear code.
Preferably, the PWM generation module further includes:
and the random delay generating unit is used for respectively generating random delay time for the N paths of PWM signals so that the PWM unit starts to output the N paths of PWM signals according to the generated random delay time.
Preferably, the circuit further comprises:
and the N constant current driving modules are used for generating corresponding driving constant currents by utilizing the reference current in a mirror image mode when the N constant current driving modules are respectively conducted.
Preferably, the reference current source module includes a reference unit for generating a reference voltage and a reference current, a first error amplifier and a first switch tube, one input end of the first error amplifier is connected to the reference voltage, the other input end of the first error amplifier is connected to a drain of the first switch tube, an output end of the first error amplifier is connected to a gate of the first switch tube, the drain of the first switch tube is connected to the reference current, and a source of the first switch tube is connected to a negative input power GND;
each constant current driving module is provided with: the light-emitting diode comprises a second error amplifier, a second switching tube and a third switching tube, wherein one input end of the second error amplifier is connected with a drain electrode of the first switching tube, the other input end of the second error amplifier is connected with a source electrode of the second switching tube, an output end of the second error amplifier is connected with a grid electrode of the second switching tube, the drain electrode of the second switching tube is used for being connected with a negative electrode of a light-emitting load, the source electrode of the second switching tube is connected with a drain electrode of the third switching tube, the grid electrode of the third switching tube is connected with the grid electrode of the first switching tube, and the source electrode of the third switching tube is connected with a negative input power supply GND;
each PWM switch module comprises a fourth switch tube, the grid electrode of the fourth switch tube is connected with a corresponding PWM signal, the drain electrode of the fourth switch tube is connected with the grid electrode of the second switch tube in the corresponding constant current driving module to control the on or off of the constant current driving module, so that the current of the constant current driving module is controlled, and the source electrode of the fourth switch tube is connected with a negative input power supply GND.
Preferably, the driving circuit further includes:
and the VDD voltage module is used for generating working voltage VDD required by components in the whole driving circuit based on a positive input power VCC.
The invention also discloses a linear constant current driving chip for PWM dimming, wherein the circuit as any one of the above is integrated in the chip.
Preferably, the chip includes VCC end, GND end and a N OUT end, wherein, the VCC end is used for inserting positive input power VCC, GND end is used for inserting negative input power GND, each can insert luminous load of the same way between OUT end and the VCC end.
The invention also discloses a linear constant current driving method for PWM dimming, which comprises the following steps:
decoding N parts of dimming gear codes modulated into a power supply from the power supply, wherein N is a positive integer;
after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, generating N paths of PWM signals corresponding to the N parts of the decoded dimming gear codes;
and adjusting the conduction state of the corresponding N constant current driving modules based on the N paths of PWM signals, and further controlling the magnitude of driving current for driving a luminous load, wherein the constant current driving modules can be connected into the luminous load and carry out constant current driving on the luminous load.
The linear constant current driving circuit, the chip and the method for PWM dimming have the following beneficial effects: the dimming gear code is modulated into the power supply source, after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, N paths of PWM signals corresponding to N parts of the decoded dimming gear code are generated inside the circuit, and then the N paths of PWM signals are utilized to realize constant current drive of N paths of luminous loads accessed by N constant current drive modules, so that:
1) can solve among the prior art directly utilize VCC to carry out a great deal of problem that PWM adjusted luminance, for example: the problems of system stability and chip service life can be solved, the problems of limited PWM frequency and easy generation of noise and stroboscopic phenomena can be solved, and the problem of large total current ripple can be solved;
2) when N is a positive number larger than 1, the effect that one chip is simultaneously connected with N paths of loads can be realized;
3) by modulating N parts of dimming gear codes, each path of luminous load can correspond to one dimming gear code, and the N paths of luminous loads can be independently controlled, so that when the colors of the N paths of LED loads are various, the whole dimming control can be realized by dimming each path of luminous load.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only examples of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts:
fig. 1 is a schematic diagram of an application system of a conventional flexible light strip LED driving chip;
fig. 2 is an internal block diagram of a conventional flexible light strip LED driver chip;
fig. 3 is a PWM dimming waveform diagram of a conventional flexible light strip LED driving chip;
FIG. 4 is a schematic diagram of an application system of the linear constant current driving chip of the present invention;
fig. 5 is an internal block diagram of an embodiment of a linear constant current driving chip according to the present invention;
fig. 6 is a PWM dimming waveform diagram of the linear constant current driving chip of the present invention;
fig. 7 is an internal block diagram of another embodiment of a linear constant current driving chip according to the invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Exemplary embodiments of the invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It is noted that reference herein to "connected" or "coupled" includes not only direct connection of two entities but also indirect connection through other entities with beneficial or improved effects.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The terms "first", "second", and the like, including ordinal numbers, used in the present specification may be used to describe various components, but the components are not limited by the terms. These terms are used only for the purpose of distinguishing one constituent element from other constituent elements. For example, a first component may be named a second component, and similarly, a second component may also be named a first component, without departing from the scope of the present invention.
The general idea of the invention is as follows: the method comprises the steps that a dimming gear code is used for representing a dimming target, and N parts of dimming gear codes modulated into a power supply source are decoded from the power supply source; then, after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, generating N paths of PWM signals corresponding to the N parts of the decoded dimming gear codes; and finally, adjusting the conduction states of the corresponding N constant current driving modules based on the N paths of PWM signals, and further controlling the magnitude of driving current for driving a luminous load, wherein the constant current driving modules can be connected into the luminous load and carry out constant current driving on the luminous load.
In order to better understand the technical solutions, the technical solutions will be described in detail below with reference to the drawings and the specific embodiments of the specification, and it should be understood that the embodiments and specific features of the embodiments of the present invention are detailed descriptions of the technical solutions of the present application, and are not limited to the technical solutions of the present application, and the technical features of the embodiments and examples of the present invention may be combined with each other without conflict.
Referring to fig. 4-5, fig. 4 is a schematic diagram of an application system of the linear constant current driving chip of the present invention, and fig. 5 is an internal block diagram of an embodiment of the linear constant current driving chip of the present invention.
The chip of this embodiment is integrated with the linear constant current driving circuit of the present invention, and includes a VCC terminal, a GND terminal, and N OUT terminals, where the VCC terminal is used to access a positive input power VCC, the GND terminal is used to access a negative input power GND, and a light-emitting load may be connected between each of the OUT terminals and the VCC terminal.
Referring to fig. 5, the linear constant current driving circuit inside the chip includes:
the decoding module 101 is connected with a VCC end and used for decoding N parts of dimming gear codes modulated into a power supply from the power supply, wherein N is a positive integer;
the PWM generating module 102 is connected to the decoding module 101, and configured to generate N PWM signals corresponding to the N decoded dimming level codes after the power supply source recovers from a phase in which the dimming level code is modulated to a normal power supply phase in which the dimming level code is not modulated;
each of the N constant current driving modules 104 is configured to perform constant current driving on a light emitting load connected thereto when the light emitting load is turned on;
the N PWM switch modules 103 correspond to the N PWM signals and the N constant current driver modules one to one, the N PWM switch modules 103 are respectively connected to the PWM generating module 102 to respectively receive the corresponding PWM signals, meanwhile, the N PWM switch modules 103 are also respectively connected to the N constant current driver modules 104 in a one to one correspondence, and each PWM switch module is configured to adjust a conduction state of a corresponding constant current driver module based on the corresponding one of the PWM signals, so as to control a magnitude of a driving current for driving the light emitting load.
In this embodiment, taking N as 2 as an example for explanation, as shown in the two ports of OUT1 and OUT2, the PWM generating module 102 outputs two paths of PWM signals: the numbers of the PWM1, the PWM2, the PWM switching module 103 and the constant current driving module 104 are two. It is understood that N is 1 and other positive numbers greater than 2 are also within the scope of the present invention.
In this embodiment, the dimming shift code is modulated into the positive input power VCC, that is, the power supply source is the positive input power VCC of the entire driving circuit. It is of course understood that the dimming notch code may also be modulated into the negative input power supply GND, which is then the negative input power supply GND of the entire drive circuit.
Each part of the dimming gear code corresponds to a binary level, and the binary level is modulated into the power supply source in a mode of being superposed with the voltage of the power supply source.
Specifically, the dimming level includes an M level, and after the dimming level is set for a certain path of light-emitting load, the dimming level needs to be converted into a binary system with a preset number of digits, and then a binary level representing a dimming level code is generated according to the binary system. For example, the dimming ranges include 128 ranges, which are: if the predetermined number of bits is 8 bits, the binary numbers of the 0 th, 1 th, … th, 126 th, 127 th, the 0 th, 1 th, … th, 126 th, 127 th, are 00000000, 00000001, …, 01111110 th, 0111111 th. If the gear of the load connected to the OUT1 terminal is selected as the 64 th gear, the corresponding binary value is 01000000.
It should be noted that 0 and 1 of the binary level can be represented by different voltage amplitudes or different time widths. Suppose that the convention represents 0 and 1 by different voltage amplitudes, such as-1V for 0 and 0V for 1, and then the time width of each bit of the binary level is the same, all for the convention duration. Assuming that the normal amplitude of the positive input power VCC is 24V, after superimposing the binary level on VCC, it should be 23V for 0 and 24V for 1.
Considering that in this embodiment, since 24V represents 1, it cannot be distinguished from the normal voltage of VCC, and therefore when decoding starts, it is preferable that handshake code information is first inserted into the power supply source, and the decoding module is configured to decode N dimming shift codes modulated into the power supply source from the power supply source after monitoring the handshake code information in the power supply source.
The specific form of the handshake code information is not limited as long as the decoding module can distinguish from the normal VCC voltage, for example, a level lower than 24V (e.g., 22V) lasting for a certain period of time. Obviously, the specific form of the handshake code information needs the circuit and the chip to be well defined in advance with the matching system.
With continuing reference to fig. 5, in this embodiment, the PWM generation module 102 includes:
a clock unit 1021 for generating a standard clock signal;
the PWM unit 1022 is configured to, for each N-channel PWM signal, delay corresponding time and generate a corresponding channel of PWM signal by using the clock signal after the power supply source recovers from the phase of modulating the dimming bit code to the normal power supply phase of not modulating the dimming bit code.
In this embodiment, the duty ratio of each PWM signal is positively correlated with a corresponding dimming level code. For example, the larger the shift position is, the larger the duty ratio is, whereas the smaller the shift position is, the smaller the duty ratio is. Of course, it is understood that the duty cycle of the PWM signal may be inversely related to a corresponding dimming gear code, as long as a dimming gear code corresponds to a unique duty cycle.
In this embodiment, each of the PWM signals is output after a corresponding time delay, which aims to control the time delays of the PWM1 and the PWM2, so that peak values of the Iout1 and the Iout2 are not superimposed, and thus ripples of the total current Iout _ all are smoothed, as shown in fig. 6, taking a 50% duty ratio as an example, the Iout1 and the Iout2 are output at different time delays, and thus no current superposition occurs, and ripples of the Iout _ all are very small.
With reference to fig. 5, in this embodiment, a current mirror mode is used to provide a driving current for each constant current driving module 104, so the circuit in the chip in this embodiment further includes:
and a reference current source module 105 for generating a reference current Iref. The N constant current driving modules 104 of the present invention can respectively generate corresponding driving constant currents Iout1, Iout2, …, and IoutN by using the reference current Iref in a mirror image manner when being turned on.
More specifically, referring to fig. 5, the reference current source module 105 includes a reference unit for generating a reference voltage Vbias and a reference current Iref, a first error amplifier EA1 and a first switch tube M0, where the reference voltage Vbias may be implemented with reference to a conventional driving chip, the reference current Iref may be implemented with reference to a design scheme of a reference current of a commonly used mirror current source, and is not expanded here. One input end of the first error amplifier EA1 is connected to the reference voltage, the other input end is connected to the drain of the first switching tube M0, the output end is connected to the gate of the first switching tube M0, the drain of the first switching tube M0 is connected to the reference current, and the source of the first switching tube M0 is connected to the negative input power GND.
In each of the constant current driving modules 104: the LED driving circuit comprises a second error amplifier EA2/EA3, a second switch tube HM1/HM2 and a third switch tube M1/M2, wherein one input end of the second error amplifier EA2/EA3 is connected with the drain electrode of the first switch tube M0, the other input end of the second error amplifier EA2/EA3 is connected with the source electrode of the second switch tube HM1/HM2, the output end of the second error amplifier EA2/EA is connected with the grid electrode of the second switch tube HM1/HM2, the grid electrode of the second switch tube HM1/HM2 is connected with the OUT1/OU2 end and used for being connected with the negative electrode of a light-emitting load, the source electrode of the second switch tube HM1/HM2 is connected with the drain electrode of the third switch tube M1/M2, the grid electrode of the third switch tube M1/M2 is connected with the grid electrode of the first switch tube M0, and the source electrode of the third switch tube M1/M2 is connected with a negative input power supply GND.
Each PWM switch module 103 includes a fourth switch tube M3/M4, a gate of the fourth switch tube M3/M4 is connected to a corresponding one of the PWM signals, a drain of the fourth switch tube M3/M4 is connected to a gate of the second switch tube HM1/HM2 in the corresponding constant current drive module 104 to control on or off of the constant current drive module 104, so as to control a current of the constant current drive module 104, and a source of the fourth switch tube M3/M4 is connected to a negative input power GND.
It is understood that the type of the switch transistor in the present embodiment can be selected but not limited to MOS transistor.
Furthermore, the driving circuit in the chip further includes a VDD voltage module 106, configured to generate an operating voltage VDD required by components in the entire driving circuit based on a positive input power VCC. This can be achieved by means of voltage conversion, linear voltage stabilization techniques, etc. commonly used in chips, for example, by using LDO to generate the internal power supply VDD, which is not expanded here.
It can be seen that the chip in this embodiment can drive 2 LED lighting loads, so the total number of chips is half of the scheme in fig. 1, and the cost can be greatly saved. The reference current source module 105 generates a current reference Iref and flows through M0, EA2 makes Vd0 equal to Vd1, and since the G/S/D three-terminal voltages of M1 and M0 are equal, Iout1 equal to M × Iref (M is the ratio of the sum of the numbers of the MOS transistors HM1 and M1 to the number of M0); in order to implement PWM, in this embodiment, the VCC superimposes the signal, and the signal is decoded by the decoding module 101 inside the chip and inputted into the PWM unit 1022, and the corresponding PWM signal is generated in cooperation with the clock generated by the clock unit 1021, and the gate signals G1 and G2 of the HM1 and HM2 are controlled by M3 and M4, so as to implement PWM dimming. Meanwhile, by controlling the time delay of the PWM1 and the PWM2 to make the switches of the G1 and the G2 asynchronous, the peak value superposition of the Iout1 and the Iout2 does not occur, so that the ripple of the total current Iout _ all is smoothed, as shown in fig. 6, for example, with a 50% duty ratio, the current superposition of the Iout1 and the Iout2 does not occur, and the ripple of the Iout _ all is very small. In the invention, the effect of PWM dimming is obtained by switching the HM1 and the HM2 in the chip, the switching speed of the HM1 and the HM2 can be very high, and the time delay is 10nS level, so the PWM dimming frequency can be very high, such as 30-60K, and the problems of noise and flash can be completely avoided.
In addition, the chip of this embodiment can realize a color matching function, as shown in fig. 4, if the odd channel Iout1 to L-1 is a white LED, and the even channel Iout2 to L is a yellow LED, different PWM gear codes can be respectively sent to the PWM1 and the PWM2, and different colors can be realized by mixing and modulating the brightness of the white and yellow LEDs, that is, the color matching of the LEDs can be realized.
In order to further optimize the ripple of the total current Iout _ all, a random delay function may be added to the chip of the present invention, and in other embodiments, preferably, the PWM generating module 102 further includes: and the random delay generating unit 1023 is used for respectively generating random delay time for the N paths of PWM signals so that the PWM unit starts to output the N paths of PWM signals according to the generated random delay time. When the number of the LED light emitting loads is large, these different time delays further average the Iout of each LED light emitting load channel, thereby reducing the ripple of Iout _ all.
Based on the same invention concept, the invention also discloses a linear constant current driving method for PWM dimming, which comprises the following steps:
s101, decoding N parts of dimming gear codes modulated into a power supply from the power supply, wherein N is a positive integer;
s102, after the power supply source recovers from a stage of modulating the dimming gear code to a normal power supply stage of not modulating the dimming gear code, generating N paths of PWM signals corresponding to the N parts of the decoded dimming gear codes;
and S103, adjusting the conduction states of the corresponding N constant current driving modules based on the N paths of PWM signals, and further controlling the magnitude of driving current for driving a luminous load, wherein the constant current driving modules can be connected to the luminous load and carry out constant current driving on the luminous load.
The method of the present invention can be implemented based on the linear constant current driving circuit or the chip, so more details can be referred to the above device embodiment, and are not described herein again.
In summary, the linear constant current driving circuit, the chip and the method for PWM dimming of the present invention have the following beneficial effects: the invention modulates the dimming gear code into the power supply source, after the power supply source recovers to the normal power supply stage of unmodulating the dimming gear code from the stage of modulating the dimming gear code, N paths of PWM signals corresponding to N parts of the decoded dimming gear code are generated in the circuit, and then the N paths of PWM signals are utilized to realize the constant current drive of N paths of luminous loads accessed by N constant current drive modules, thus:
1) can solve among the prior art directly utilize VCC to carry out a great deal of problems that PWM adjusted luminance, for example: the problems of system stability and chip service life can be solved, the problems of limited PWM frequency and easy generation of noise and stroboscopic phenomena can be solved, and the problem of large total current ripple can be solved;
2) when N is a positive number larger than 1, the effect that one chip is simultaneously connected with N paths of loads can be realized;
3) by modulating N parts of dimming gear codes, each path of luminous load can correspond to one part of dimming gear code, and independent control over the N paths of luminous loads can be realized.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A linear constant current driving circuit for PWM dimming, the circuit comprising:
the decoding module is used for decoding N parts of dimming gear codes modulated into the power supply from the power supply, wherein N is a positive integer greater than 1;
the PWM generating module is used for generating N paths of PWM signals corresponding to the N parts of decoded dimming gear codes after the power supply source recovers from the phase of modulating the dimming gear codes to the normal power supply phase of not modulating the dimming gear codes;
each constant current driving module is used for carrying out constant current driving on a light emitting load connected to the constant current driving module when the constant current driving module is conducted;
the N PWM switch modules correspond to the N paths of PWM signals and the N constant current driving modules respectively one by one, and each PWM switch module is used for adjusting the conduction state of a corresponding constant current driving module based on the corresponding path of PWM signal so as to control the magnitude of driving current for driving a luminous load;
wherein the PWM generation module comprises:
a clock unit for generating a standard clock signal;
and the PWM unit is used for delaying corresponding time to generate a corresponding path of PWM signals by using the clock signal after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code aiming at each path of N PWM signals, and the duty ratio of each path of PWM signals is related to a corresponding dimming gear code.
2. The circuit according to claim 1, wherein the power supply source is a positive input power source VCC of the whole driving circuit or a negative input power source GND of the whole driving circuit;
each part of the dimming gear code corresponds to a binary level, and the binary level is modulated into the power supply source in a mode of being superposed with the voltage of the power supply source.
3. The circuit of claim 1, wherein the decoding module is configured to decode N parts of the dimming gear code modulated into the power supply from the power supply after monitoring handshake code information in the power supply.
4. The circuit of claim 1, wherein the PWM generation module further comprises:
and the random delay generating unit is used for respectively generating random delay time for the N paths of PWM signals so that the PWM unit starts to output the N paths of PWM signals according to the generated random delay time.
5. The circuit of claim 1, further comprising:
and the N constant current driving modules are used for generating corresponding driving constant currents by using the reference currents in a mirror mode when the N constant current driving modules are respectively conducted.
6. The circuit according to claim 5, wherein the reference current source module comprises a reference unit for generating a reference voltage and a reference current, a first error amplifier and a first switch tube, one input end of the first error amplifier is connected to the reference voltage, the other input end of the first error amplifier is connected to the drain of the first switch tube, the output end of the first error amplifier is connected to the gate of the first switch tube, the drain of the first switch tube is connected to the reference current, and the source of the first switch tube is connected to a negative input power supply GND;
each constant current driving module comprises: the light-emitting diode comprises a second error amplifier, a second switching tube and a third switching tube, wherein one input end of the second error amplifier is connected with a drain electrode of the first switching tube, the other input end of the second error amplifier is connected with a source electrode of the second switching tube, an output end of the second error amplifier is connected with a grid electrode of the second switching tube, the drain electrode of the second switching tube is used for being connected with a negative electrode of a light-emitting load, the source electrode of the second switching tube is connected with a drain electrode of the third switching tube, the grid electrode of the third switching tube is connected with the grid electrode of the first switching tube, and the source electrode of the third switching tube is connected with a negative input power supply GND;
each PWM switch module comprises a fourth switch tube, the grid electrode of the fourth switch tube is connected with a corresponding PWM signal, the drain electrode of the fourth switch tube is connected with the grid electrode of the second switch tube in the corresponding constant current driving module to control the on or off of the constant current driving module, so that the current of the constant current driving module is controlled, and the source electrode of the fourth switch tube is connected with a negative input power supply GND.
7. The circuit of claim 1, wherein the driver circuit further comprises:
and the VDD voltage module is used for generating working voltage VDD required by components in the whole driving circuit based on a positive input power VCC.
8. A linear constant current driving chip for PWM dimming, wherein the circuit of any one of claims 1-7 is integrated inside the chip.
9. The chip according to claim 8, wherein the chip comprises a VCC terminal, a GND terminal, and N OUT terminals, wherein the VCC terminal is connected to a positive input power VCC, the GND terminal is connected to a negative input power GND, and a light emitting load is connected between each of the OUT terminals and the VCC terminal.
10. A linear constant current driving method for PWM dimming is characterized by comprising the following steps:
decoding N parts of dimming gear codes modulated into a power supply from the power supply, wherein N is a positive integer greater than 1;
after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, generating N paths of PWM signals corresponding to the N parts of the decoded dimming gear codes, specifically comprising: for each path of N paths of PWM signals, after the power supply source recovers from the stage of modulating the dimming gear code to the normal power supply stage of not modulating the dimming gear code, delaying corresponding time and then generating a corresponding path of PWM signals by using a standard clock signal, wherein the duty ratio of each path of PWM signals is related to a corresponding dimming gear code;
and adjusting the conduction state of the corresponding N constant current driving modules based on the N paths of PWM signals, and further controlling the magnitude of driving current for driving a luminous load, wherein the constant current driving modules can be connected to the luminous load and carry out constant current driving on the luminous load.
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