阅读说明：本技术 多路led驱动方法及驱动电路 (Multi-path LED driving method and driving circuit ) 是由 黄必亮 于 2020-10-22 设计创作，主要内容包括：本发明公开了多路LED灯串的驱动方法及驱动电路,通过设置高于LED灯串期望工作电流的第一参考值,根据第一参考值调节LED灯串的电流使得LED灯串实际的工作电流大于其期望的工作电流,并且实时监测该LED灯串的光亮度,当检测到所述LED灯串的亮度控制检测信号达到该支路LED灯串期望亮度输出的亮度控制基准信号时,则关闭对LED灯串的电流调节。如此,可保证该LED灯串的亮度输出达到需求值,实现每路LED灯串亮度的精确控制,并且系统功耗小,效率达到提高。(The invention discloses a driving method and a driving circuit of a multi-path LED lamp string, wherein a first reference value higher than the expected working current of the LED lamp string is set, the current of the LED lamp string is adjusted according to the first reference value, so that the actual working current of the LED lamp string is larger than the expected working current of the LED lamp string, the brightness of the LED lamp string is monitored in real time, and when the brightness control detection signal of the LED lamp string reaches a brightness control reference signal output by the expected brightness of the LED lamp string of a branch circuit, the current adjustment of the LED lamp string is closed. Therefore, the brightness output of the LED lamp string can reach a required value, the accurate control of the brightness of each LED lamp string is realized, the power consumption of the system is low, and the efficiency is improved.)

1. A driving method of a multi-path LED lamp string is characterized by comprising the following steps;

s1: setting a first reference value higher than the expected current of each path of LED lamp string for each path of LED lamp string;

s2: controlling and adjusting the working current of the LED lamp string according to the first reference value, so that the working current of the LED lamp string is maintained at the first reference value;

synchronously monitoring the luminance of the LED lamp string, obtaining a luminance control detection signal, and comparing the luminance control detection signal with a luminance control reference signal representing the expected luminance output of the LED lamp string;

s3: and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal, the regulation of the working current of the LED lamp string is closed.

2. The driving method according to claim 1, wherein in step S1, the first reference value V_REFThe specific setting method comprises the following steps:

V_REF＝I_LED*R_SN(1+A％)

wherein, I_LEDDesired current, R, for the LED string_SNIs the resistance value of the sampling resistor, A is a natural number, the setting range is larger than zero and makes I_LED(1+ A%) is less than the maximum current of LED string.

3. The driving method according to claim 1, wherein in step S2, the acquiring of the luminance control detection signal includes:

sampling to obtain a sampling voltage signal representing the current of the LED lamp string;

and integrating the sampling voltage signal with time in real time to obtain the brightness control detection signal.

4. The driving method according to claim 1, wherein the step of turning off the regulation of the operating current of the LED light string in step S3 specifically includes,

and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal representing the expected brightness output of the LED lamp string, the main switching tube for regulating the working current of the LED lamp string is turned off.

5. A drive circuit of a plurality of paths of LED lamp strings is characterized in that the drive circuit comprises a plurality of paths of current regulating circuits and a plurality of paths of luminance brightness control circuits, the plurality of paths of current regulating circuits and the plurality of paths of luminance brightness control circuits are in one-to-one correspondence with the plurality of paths of LED lamp strings,

each path of the brightness detection circuit monitors the brightness of the path of LED lamp string in real time, and compares a brightness control detection signal with a brightness control reference signal representing the expected brightness output of the path of LED lamp string to obtain a comparison signal;

each path of current regulating circuit receives the comparison signal, and the current regulating circuit regulates the working current of the path of LED lamp string according to a preset first reference value, so that the working current of the path of LED lamp string is maintained at the first reference value, wherein the first reference value is set to be higher than the expected working current of the path of LED lamp string;

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the current regulating circuit closes the regulation of the working current of the LED lamp string.

6. The driving circuit of claim 5, wherein each of the current regulating circuits comprises a main switch tube and a sampling resistor connected in series with the LED light string, and a current regulation control circuit for controlling the main switch tube,

the current regulation control circuit obtains a sampling voltage signal through the sampling resistor, and performs operational amplification on the sampling voltage signal and the first reference value so as to transmit a first operational result to the control end of the main switching tube.

7. The driving circuit according to claim 6, wherein the first reference value V_REFThe specific setting method comprises the following steps:

V_REF＝I_LED*R_SN(1+A％)

wherein, I_LEDFor the desired current, R, of the corresponding branch LED string_SNIs the resistance value of the sampling resistor, A is a natural number, the setting range of A is larger than zero and makes I_LED(1+ A%) is less than the maximum current of LED string.

8. The driving circuit according to claim 6, wherein each of the light intensity control circuits includes an integrating circuit and a comparing circuit,

the integration circuit obtains a sampling voltage signal through the sampling resistor and integrates the sampling voltage signal with time in real time to obtain the brightness control detection signal,

the comparison circuit compares the brightness control detection signal with a brightness control reference signal representing the expected brightness output of the LED lamp string, and transmits the comparison signal to the current regulation control circuit.

9. The driving circuit of claim 8, wherein a plurality of luminance control reference signals corresponding to desired luminance outputs of a plurality of LED light strings are set according to luminance requirements of the plurality of LED light strings, the plurality of luminance control reference signals are correspondingly input to the plurality of luminance control circuits,

wherein, the plurality of luminance control reference signals can be same or different in size.

10. The driving circuit as claimed in claim 6, wherein each of the current regulating circuits further comprises a first switch tube and a pull-down circuit,

the first switch tube is connected between the output end of the current regulation control circuit and the control end of the main switch tube,

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the first switch tube is disconnected, and the pull-down circuit pulls down the control end voltage of the main switch tube to turn off the main switch tube.

11. The driver circuit of claim 6, wherein each of the current regulation circuits further comprises an enable circuit,

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the enabling circuit outputs an enabling signal,

the current regulation control circuit further comprises an disable end, and the disable end receives the enable signal to disable the operation of the current regulation control circuit.

Technical Field

The invention relates to the technical field of LED driving, in particular to a multi-path LED driving method and a multi-path LED driving circuit.

Background

In the LED lighting technology applied to the backlight, a plurality of LED strings are often arranged to be used in parallel, and the driving controller needs to control the plurality of LED strings to work, where each string of LEDs has a separate brightness requirement.

In the prior art, the current flowing through the LED string is regulated and controlled by a current regulating circuit, such as a linear regulator LDO, which is matched with the branch circuit, as shown in fig. 1, the current regulating circuit is a common LDO circuit structure in the prior art, and the LDO circuit includes a switching tube Q, a resistor R and an operational amplifier OP, and a reference value V representing the expected operating current of the LED branch circuit is set_RAnd the current of the LED branch circuit is maintained at the expected working current through operation feedback.

However, the above current control method has the problems that due to differences in manufacturing of LED light strings, voltage drops of each LED light string are different, so that voltage drops of each LDO are different, and under the condition that a voltage drop of a certain LDO is large, if a switch maintaining a current of the LED branch at an expected working current is long in conduction time, power consumption on the switching tube Q is large, so that heat dissipation of a system is high and efficiency is low.

Disclosure of Invention

In view of the above, the present invention provides a multi-path LED driving method and a driving circuit, so as to solve the technical problems of high heat dissipation and low efficiency of the multi-path LED driving circuit in the prior art.

The technical scheme of the invention is that the driving method of the multipath LED lamp string is provided, which comprises the following steps;

s1: setting a first reference value higher than the expected current of each path of LED lamp string for each path of LED lamp string;

s2: controlling and adjusting the working current of the LED lamp string according to the first reference value, so that the working current of the LED lamp string is maintained at the first reference value;

synchronously monitoring the brightness of the LED lamp string to obtain a brightness control detection signal, and comparing the brightness control detection signal with a brightness control reference signal representing the expected brightness output of the LED lamp string;

s3: and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal, the regulation of the working current of the LED lamp string is closed.

Preferably, the first reference value V_REFThe specific setting method comprises the following steps:

V_REF＝I_LED*R_SN(1+A％)

wherein, I_LEDDesired current, R, for the LED string_SNIs the resistance value of the sampling resistor, A is a natural number, the setting range is larger than zero and makes I_LED(1+ A%) is less than the maximum current of LED string.

Preferably, in step S2, the acquiring of the brightness control detection signal includes:

sampling to obtain a sampling voltage signal representing the current of the LED lamp string;

and integrating the sampling voltage signal with time in real time to obtain the brightness control detection signal.

Preferably, in step S3, the step of turning off the regulation of the operating current of the LED light string includes,

and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal representing the expected brightness output of the LED lamp string, the main switching tube for regulating the working current of the LED lamp string is turned off.

In a second aspect, the invention discloses a driving circuit of a multi-path LED lamp string, the driving circuit comprises a multi-path current regulating circuit and a multi-path light brightness control circuit, the multi-path current regulating circuit and the multi-path light brightness control circuit correspond to the multi-path LED lamp string one by one,

each path of the brightness detection circuit monitors the brightness of the path of LED lamp string in real time, and compares a brightness control detection signal with a brightness control reference signal representing the expected brightness output of the path of LED lamp string to obtain a comparison signal;

each path of current regulating circuit receives the comparison signal, and the current regulating circuit regulates the working current of the path of LED lamp string according to a preset first reference value, so that the working current of the path of LED lamp string is maintained at the first reference value, wherein the first reference value is set to be higher than the expected working current of the path of LED lamp string;

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the current regulating circuit closes the regulation of the working current of the LED lamp string.

Preferably, each of the current adjusting circuits includes a main switching tube and a sampling resistor connected in series with the LED light string, and a current adjusting control circuit for controlling the main switching tube,

the current regulation control circuit obtains a sampling voltage signal through the sampling resistor, and performs operational amplification on the sampling voltage signal and the first reference value so as to transmit a first operational result to the control end of the main switching tube.

Preferably, each light intensity control circuit comprises an integrating circuit and a comparing circuit,

the integration circuit obtains a sampling voltage signal through the sampling resistor and integrates the sampling voltage signal with time in real time to obtain the brightness control detection signal,

the comparison circuit compares the brightness control detection signal with a brightness control reference signal representing the expected brightness output of the LED lamp string, and transmits the comparison signal to the current regulation control circuit.

Preferably, a plurality of paths of brightness control reference signals corresponding to the desired brightness output of the plurality of paths of LED lamp strings are set according to the brightness requirement of the plurality of paths of LED lamp strings, the plurality of paths of brightness control reference signals are correspondingly input to the plurality of paths of brightness control circuits,

wherein, the plurality of luminance control reference signals can be same or different in size.

Preferably, each of the current adjusting circuits further comprises a first switch tube and a pull-down circuit,

the first switch tube is connected between the output end of the current regulation control circuit and the control end of the main switch tube,

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the first switch tube is disconnected, and the pull-down circuit pulls down the control end voltage of the main switch tube to turn off the main switch tube.

Preferably, each of the current regulating circuits further comprises an enabling circuit,

when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the enabling circuit outputs an enabling signal,

the current regulation control circuit further comprises an disable end, and the disable end receives the enable signal to disable the operation of the current regulation control circuit. By adopting the multi-path LED driving technology, the current flowing through the LED lamp string is larger than the expected working current of the branch circuit of the LED lamp string by setting the first reference value higher than the expected working current of the branch circuit of the LED lamp string, the brightness of the LED lamp string is monitored in real time, and when the detected brightness control detection signal reaches the brightness control reference signal of the expected brightness output of the branch circuit LED lamp string, the current regulation of the branch circuit LDO circuit to the LED lamp string is closed, so that the brightness output of the LED lamp string can be ensured to reach the required value, the accurate control of the brightness of each string of LED lamps is realized, the power consumption of a switching tube is small, and the system efficiency is high.

Drawings

FIG. 1 is a block diagram of a prior art multi-channel LED driver circuit;

FIG. 2 is a block diagram of a multi-way LED driver circuit according to the present invention;

FIG. 3 is a circuit diagram of a first embodiment of a multi-way LED driving circuit according to the present invention;

FIG. 4 is a flow chart of a multi-way LED driving method according to the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to only these embodiments. The invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention.

In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in simplified form and are not to precise scale, which is only used for convenience and clarity to assist in describing the embodiments of the present invention.

Fig. 2 is a block diagram of a multi-path LED driving circuit according to the present invention and fig. 3 is a detailed circuit diagram of the multi-path LED driving circuit according to the present invention, wherein a voltage regulator receives an input voltage Vin to generate an output voltage Vo to be supplied to the multi-path LED light string, the multi-path LED light string includes LED light strings 1 to n connected in parallel, and the voltage regulator may be a suitable voltage converter such as a boost type, a buck type, a flyback type, a forward type, or the like.

Referring to fig. 2, the driving circuit includes a plurality of current adjusting circuits and a plurality of luminance control circuits, the plurality of current adjusting circuits and the plurality of luminance control circuits correspond to the plurality of LED light strings one to one, as shown in fig. 2, the current adjusting circuit 1 and the luminance control circuit 1 both correspond to the LED1 light strings, the current adjusting circuit n and the luminance control circuit n both correspond to the LEDn light strings, and hereinafter, each of the signals 1 to n also corresponds to one.

In one embodiment, each of the luminance detection circuits monitors the luminance of the LED light string in real time, and compares a luminance control detection signal with a luminance control reference signal representing an expected luminance output of the LED light string to obtain a comparison signal, each of the current regulation circuits receives the comparison signal, and the current regulation circuit regulates the operating current of the LED light string according to a preset first reference value, so that the operating current of the LED light string is maintained at the first reference value, wherein the first reference value is set to be higher than the expected operating current of the LED light string; when the comparison signal represents that the brightness control detection signal reaches a brightness control reference signal representing the expected brightness output of the LED lamp string, the current regulating circuit closes the regulation of the working current of the LED lamp string. According to the scheme, the brightness of the LED lamp string can be controlled to achieve the required brightness output, the brightness of the LED lamp string is accurately controlled, and when the required brightness is achieved, the adjustment of the working current of the LED lamp string is stopped, so that the conducting time of the switch tube can be reduced, the power consumption of the switch tube is reduced, and the system efficiency is improved.

Referring to fig. 3, in one embodiment, each of the current regulating circuits includes a main switch Q and a sampling resistor R connected in series with the LED string_SNAnd a current regulation control circuit for controlling the main switching tube, wherein the current regulation control circuit comprises an operational amplifier OP, and the current regulation control circuit passes through the sampling resistor R_SNObtaining a sampled voltage signal V_SNThe operational amplifier OP will sample the voltage signalV_SNAnd said first reference value V_REFAnd performing operation comparison to transmit a first operation result to the control end of the main switching tube.

Wherein the first reference value V_REFThe specific setting method comprises the following steps:

V_REF＝I_LED*R_SN(1+A％)

wherein, I_LEDFor the desired current, R, of the corresponding branch LED string_SNIs the resistance value of the sampling resistor, A is a natural number, the setting range of A is larger than zero and makes I_LED(1+ A%) is less than the maximum current of LED string.

Specifically, each path of light brightness control circuit comprises an integrating circuit and a comparing circuit, the comparing circuit comprises a comparator CMP, and the integrating circuit obtains a sampling voltage signal V through the sampling resistor_SNSaid sampled voltage signal V_SNCharacterizing the current flowing through the LED lamp string, and integrating the sampled voltage signal with time in real time to obtain the brightness control detection signal V_BIHere, the brightness control detection signal is multiplied by the consumed time under a certain current to obtain the corresponding product area, and the brightness of the LED light string is represented on the LED light string, that is, different detection signals correspond to different brightness outputs, so that the brightness of the LED light string can be monitored in real time.

The comparator CMP compares the brightness control detection signal V_BIAnd a brightness control reference signal V for representing the expected brightness output of the LED lamp string_RBIAnd comparing the result V_BAnd transmitting the current to the current regulation control circuit.

Here, by externally setting a plurality of luminance control reference signals corresponding to desired luminance outputs of a plurality of LED light strings, the plurality of luminance control reference signals being set according to luminance requirements of the plurality of LED light strings, the plurality of luminance control reference signals being input to the plurality of luminance control circuits in a one-to-one correspondence, where the luminance control reference signals are received by one input terminal of the comparator CMP, wherein the plurality of luminance control reference signals may be set to be the same or different in magnitude according to the luminance requirements of the plurality of LED light strings.

In an embodiment, each of the current regulation circuits further includes a first switch tube S1 and a pull-down circuit, the first switch tube S1 is connected between the output end of the current regulation control circuit and the control end of the main switch tube Q, when the comparison signal indicates that the brightness control detection signal reaches a brightness control reference signal indicating the desired brightness output of the LED light string, the comparison signal becomes inactive at a low level, the first switch tube S1 is turned off, and the pull-down circuit pulls down the control end voltage of the main switch tube. Here, the pull-down circuit may be composed of a switching tube and a pull-down current source, but is not limited thereto, the pull-down circuit receives the comparison signal, and when the comparison signal changes to an active state of a high level, the switching tube is turned on, so that the pull-down current source pulls down the voltage at the control end of the main switching tube, and the main switching tube is turned off.

In another embodiment, the current regulation circuit further includes an enable circuit, the enable circuit outputs an enable signal when the comparison signal indicates that the brightness control detection signal reaches the brightness control reference signal indicating the desired brightness output of the LED light string when the brightness control detection signal and the brightness control reference signal indicating the desired brightness output of the LED light string are received by the enable circuit, and the current regulation control circuit (operational amplifier OP) further includes an disable-enable terminal, and the disable-enable terminal receives the enable signal to disable the current regulation control circuit. The enabling circuit may be any circuit that can implement the enabling function.

According to the circuit structure, when the light brightness of the LED lamp string does not reach the expected light brightness, the LED lamp string is powered by the expected working current larger than the LED lamp string, and the working current larger than the expected current is subjected to time integration at the moment, so that the brightness of the LED lamp string can quickly reach the expected brightness output, and then the main switch tube for controlling the LED lamp string is quickly disconnected.

Finally, as shown in fig. 4, the invention also discloses a driving method of the multi-path LED lamp string, which is characterized by comprising the following steps;

s1: setting a first reference value higher than the expected current of each path of LED lamp string for each path of LED lamp string;

s2: controlling and adjusting the working current of the LED lamp string according to the first reference value, so that the working current of the LED lamp string is maintained at the first reference value;

synchronously monitoring the brightness of the LED lamp string to obtain a brightness control detection signal, and comparing the brightness control detection signal with a brightness control reference signal representing the expected brightness output of the LED lamp string;

s3: and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal, the regulation of the working current of the LED lamp string is closed.

Preferably, the first reference value V_REFThe specific setting method comprises the following steps:

V_REF＝I_LED*R_SN(1+A％)

wherein, I_LEDDesired current, R, for the LED string_SNIs the resistance value of the sampling resistor, A is a natural number, the setting range is larger than zero and makes I_LED(1+ A%) is less than the maximum current of LED string.

Preferably, the acquiring of the brightness control detection signal includes:

sampling to obtain a sampling voltage signal representing the current of the LED lamp string;

and integrating the sampling voltage signal with time in real time to obtain the brightness control detection signal.

Preferably, in step S3, the step of turning off the regulation of the operating current of the LED light string includes,

and when the brightness control detection signal obtained by comparison reaches the brightness control reference signal representing the expected brightness output of the LED lamp string, the main switching tube for regulating the working current of the LED lamp string is turned off.

The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.