CN118301815A - Constant-current control circuit and constant-current control method for multi-channel LED lamp strings - Google Patents

Abstract

The application discloses a constant current control circuit and a constant current control method of a multi-channel LED lamp string, and belongs to the technical field of circuits. An input power supply of the constant current control circuit is connected with the switching tube module, the switching tube module is connected with the LED switching module, the LED switching module is connected with the LED lamp string, and the voltage conversion controller is connected with the switching tube module and the LED switching module; when one time-sharing time zone is in the switching period, the voltage conversion controller is used for controlling one switch corresponding to the time-sharing time zone in the LED switch module to be closed, when the other switches are opened, the series connection conducting voltage and the input voltage of the LED lamp string corresponding to the closed switch are compared, the switching tube module is controlled to perform voltage reduction operation or voltage boosting operation according to the comparison result, and constant current control is performed on the current of the LED lamp string according to an externally input dimming instruction. The application can control the LED lamp string in a time-sharing way, reduce the circuit cost, reduce the circuit volume and improve the electric energy conversion efficiency.

Description

Constant-current control circuit and constant-current control method for multi-channel LED lamp strings

Technical Field

The application relates to the technical field of circuits, in particular to a constant current control circuit and a constant current control method of a multi-channel LED lamp string.

Background

A plurality of light emitting diodes (LIGHT EMITTING Diode, LEDs) are usually arranged in the automotive headlamp, and constant current control is required to be performed on the automotive headlamp so as to achieve a stable lighting effect.

As shown in fig. 1, the constant current control circuit of the multi-path LED lamp string includes an input power supply (VIN), first switching tube modules (Q1 and Q2), a Boost Controller (Boost Controller), three buck controllers (Buck LED Controller), three second switching tube modules (Q3 and Q4, Q5 and Q6, Q7 and Q8), three inductors (L1) and three paths of LED lamp strings, each buck Controller being connected to one path of LED lamp string through one second switching tube module and one inductor. When the LED lamp string works, the input voltage of 12V is increased to about 40-60V through the boost controller, and then the voltage is converted into multiple paths of constant current output through the multiple buck controllers, so that the multiple paths of LED lamp strings are controlled to realize illumination. The step-down controller can flexibly control the output voltage, so that the switching of the brightness of each LED lamp string from one lamp to a plurality of lamps can be realized.

If the constant current control of the three-way LED lamp string is to be realized, three buck controllers, three third switching tube modules and three inductors are required to be configured, so that the circuit cost is increased, the circuit volume is increased, and the electric energy conversion efficiency is reduced.

Disclosure of Invention

The application provides a constant current control circuit and a constant current control method of a multi-channel LED lamp string, which are used for solving the problems that the existing constant current control circuit has more devices, the circuit cost is increased, the circuit volume is increased, and the electric energy conversion efficiency is reduced. The technical scheme is as follows:

According to a first aspect of the present application, there is provided a constant current control circuit of a multi-path LED string light, the constant current control circuit comprising: the LED lamp string comprises an input power supply, a switching tube module, a voltage conversion controller, an LED switching module and a plurality of LED lamp strings;

The input power supply is connected with the switching tube module, the switching tube module is connected with the LED switching module, the LED switching module is connected with the multi-path LED lamp string, and the voltage conversion controller is respectively connected with the switching tube module and the LED switching module;

When the LED lamp string is in one time-sharing time zone in the switching period, the voltage conversion controller is used for controlling one switch corresponding to the time-sharing time zone in the LED switch module to be closed, when other switches are opened, the series connection conducting voltage and the input voltage of the LED lamp string corresponding to the closed switch are compared, the switching tube module is controlled to perform voltage reduction operation, voltage boosting operation or voltage lifting operation according to a comparison result, and constant current control is performed on the current of the LED lamp string according to an externally input dimming instruction.

In one possible implementation, the voltage conversion controller is one of a buck-boost controller, a buck controller, a boost controller, a single-ended primary inductive conversion SEPIC controller.

In one possible implementation, when the voltage conversion controller is a buck-boost controller, the switching tube module includes a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, an inductor, a first capacitor, and a second capacitor;

The first input end of the buck-boost controller is connected with the analog dimming command input end, the second input end of the buck-boost controller is connected with the Pulse Width Modulation (PWM) dimming command input end, the four first output ends of the buck-boost controller are respectively connected with the grid electrodes of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube, and each second output end of the buck-boost controller is respectively connected with one switch in the LED switching module;

The drain electrode of the first switching tube is respectively connected with the input power supply and the first end of the first capacitor, the source electrode of the first switching tube is respectively connected with the first end of the inductor and the drain electrode of the second switching tube, the second end of the inductor is respectively connected with the source electrode of the third switching tube and the drain electrode of the fourth switching tube, the drain electrode of the third switching tube is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrodes of the second switching tube and the fourth switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

In one possible implementation of the present invention,

When the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than a threshold value, the first switching tube and the second switching tube are alternately conducted, the third switching tube is kept conducting, and the fourth switching tube is kept disconnected so as to realize step-down operation;

When the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than a threshold value, the first switch tube is kept on, the second switch tube is kept off, and the third switch tube and the fourth switch Guan Jiaoti are turned on so as to realize boosting operation;

When the series connection conducting voltage is close to the input voltage and the absolute value of the difference value between the series connection conducting voltage and the input voltage is smaller than a threshold value, the first switch tube and the second switch tube are alternately conducted, and the third switch tube and the fourth switch Guan Jiaoti are conducted so as to realize voltage boosting and dropping operation.

In one possible implementation, where the series conduction voltage is close to the input voltage:

When the series connection conducting voltage is smaller than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are adjustable, the duty ratios corresponding to the third switching tube and the fourth switching tube are fixed, and the duty ratio corresponding to the first switching tube and the current of the LED lamp string are in positive correlation;

When the series connection on voltage is larger than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are fixed, the duty ratios corresponding to the third switching tube and the fourth switching tube are adjustable, and the duty ratio corresponding to the fourth switching tube and the current of the LED lamp string are in positive correlation.

In one possible implementation, when the voltage conversion controller is a buck controller, the switching tube module includes a first switching tube, a second switching tube, an inductor, a first capacitor, and a second capacitor;

The first input end of the step-down controller is connected with the analog dimming instruction input end, the second input end of the step-down controller is connected with the PWM dimming instruction input end, the two first output ends of the step-down controller are respectively connected with the grid electrodes of the first switching tube and the second switching tube, and each second output end of the step-down controller is respectively connected with one switch in the LED switching module;

The drain electrode of the first switching tube is respectively connected with the input power supply and the first end of the first capacitor, the source electrode of the first switching tube is respectively connected with the first end of the inductor and the drain electrode of the second switching tube, the second end of the inductor is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrode of the second switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

In one possible implementation, when the voltage conversion controller is a boost controller, the switching tube module includes a first switching tube, a second switching tube, an inductor, a first capacitor, and a second capacitor;

The first input end of the boost controller is connected with the analog dimming command input end, the second input end of the boost controller is connected with the PWM dimming command input end, the two first output ends of the boost controller are respectively connected with the grid electrodes of the first switching tube and the second switching tube, and each second output end of the boost controller is respectively connected with one switch in the LED switching module;

The first end of the inductor is respectively connected with the input power supply and the first end of the first capacitor, the second end of the inductor is respectively connected with the source electrode of the first switching tube and the drain electrode of the second switching tube, the drain electrode of the first switching tube is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrode of the second switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

In one possible implementation, when the voltage conversion controller is a SEPIC controller, the switching tube module includes a first switching tube, a first inductor, a second inductor, a diode, a first capacitor, a second capacitor, and a third capacitor;

The first input end of the SEPIC controller is connected with the analog dimming command input end, the second input end of the SEPIC controller is connected with the PWM dimming command input end, one first output end of the SEPIC controller is connected with the grid electrode of the first switch tube, and each second output end of the SEPIC controller is respectively connected with one switch in the LED switch module;

The first end of the first inductor is respectively connected with the input power supply and the first end of the first capacitor, the second end of the first inductor is respectively connected with the grid electrode of the first switch tube and the first end of the second capacitor, the second end of the second capacitor is respectively connected with the first end of the second inductor and the positive electrode of the diode, the negative electrode of the diode is connected with the first end of the third capacitor, and the second ends of the first capacitor and the third capacitor, the second end of the second inductor and the source electrode of the first switch tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

According to a second aspect of the present application, there is provided a constant current control method of a multi-path LED string light, for use in a constant current control circuit of a multi-path LED string light as described above, the method comprising:

When one time-sharing time zone is in a switching period, controlling one switch corresponding to the time-sharing time zone in the LED switch module to be closed, and other switches to be opened;

Comparing the series connection conducting voltage of the LED lamp string corresponding to the closed switch with the input voltage;

Controlling the switching tube module to perform buck operation, boost operation or buck-boost operation according to the comparison result;

And carrying out constant current control on the current of the LED lamp string according to an externally input dimming instruction.

In one possible implementation manner, the controlling the switching tube module to perform a buck operation or a boost operation according to the comparison result includes:

when the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than a threshold value, controlling the switching tube module to perform step-down operation;

when the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than a threshold value, controlling the switching tube module to perform boosting operation;

and when the series connection conducting voltage is close to the input voltage and the absolute value of the difference value between the series connection conducting voltage and the input voltage is smaller than a threshold value, controlling the switching tube module to perform step-up and step-down operation.

The technical scheme provided by the application has the beneficial effects that at least:

the constant current control circuit comprises a switching tube module, an LED switching module and a voltage conversion controller, a plurality of step-down controllers and a plurality of switching tube modules are not required to be arranged, circuit devices are reduced, the circuit cost can be reduced, the circuit size can be reduced, and the electric energy conversion efficiency can be improved; in addition, the LED switch module can realize time-sharing control of the multi-path LED lamp strings, effectively improve system efficiency, realize system light weight, improve endurance mileage and realize energy conservation and emission reduction.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a constant current control circuit of a multi-channel LED string light according to the related art;

Fig. 2 is a schematic block diagram of a constant current control circuit of a multi-path LED string according to an embodiment of the present application;

Fig. 3 is a schematic structural diagram of a four-tube driving constant current control circuit according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a time-sharing control circuit of an LED string light with a single switching cycle according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a time-sharing control timing of an LED string with a single switching cycle according to one embodiment of the present application;

FIG. 6 is a schematic diagram of the operation of a four-tube driven constant current control circuit according to one embodiment of the present application;

FIG. 7 is a schematic diagram of the operation of a two-tube driven constant current control circuit according to one embodiment of the present application;

FIG. 8 is a schematic diagram of the operation of a two-tube driven constant current control circuit according to one embodiment of the present application;

fig. 9 is a schematic operation diagram of a single-tube-driven constant current control circuit according to an embodiment of the present application;

fig. 10 is a flowchart of a constant current control method of a multi-path LED string light according to an embodiment of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the following detailed description of the embodiments of the present application will be given with reference to the accompanying drawings.

As shown in fig. 2, one embodiment of the present application provides a constant current control circuit for a multi-path LED string, where the constant current control circuit includes: input power 110, switching tube module 120, voltage conversion controller 130, LED switching module 140, and multi-channel LED string 150. The input power 110 is connected to the switching tube module 120, the switching tube module 120 is connected to the LED switching module 140, the LED switching module 140 is connected to the multi-path LED string 150, and the voltage conversion controller 130 is connected to the switching tube module 120 and the LED switching module 140, respectively.

The input power supply 110 is used for providing an input voltage, so as to drive the constant current control circuit to operate.

The switching tube module 120 includes at least one switching tube driven by a pulse signal so as to perform constant current control on the LED string 150 by a duty ratio of the pulse signal.

The voltage conversion controller 130 is used for performing voltage conversion according to the magnitude relation between the input voltage and the series connection conducting voltage of the LED lamp string 150. For example, when the input voltage is greater than the series turn-on voltage, the voltage conversion controller 130 is configured to perform a step-down operation; the voltage conversion controller 130 is used to perform a boosting operation when the input voltage is less than the series on voltage. Wherein the series turn-on voltage is the sum of the turn-on voltages of all the LED lamps in the LED string 150.

The LED switch module 140 includes a plurality of switches, and each switch is connected to one LED string 150 and is used for controlling the working state of one LED string 150. In this embodiment, the switching period may be divided into a plurality of time-sharing time zones according to the number of the LED light strings 150, for example, when n LED light strings 150 are provided, each switching period is divided into n time-sharing time zones, and one LED light string 150 is independently controlled to operate by a switch in each time-sharing time zone. The on-off state of the switch is determined by a control signal output by the voltage conversion controller 130. For example, when the 1 st time-sharing time zone in the switching period, the voltage conversion controller 130 outputs a control signal through the K1 port to control the switch K1 to be turned on, and then the LED light string 1 corresponding to the switch K1 is turned on; when the voltage conversion controller 130 outputs a control signal through the port K2 to control the switch K2 to be closed in the time zone of the 2 nd minute in the switching period, one LED light string 2 corresponding to the switch K2 is lighted; when the voltage conversion controller 130 outputs a control signal through the K3 port to control the switch K3 to be turned on in the 3 rd time division period in the switching period, the LED string 3 corresponding to the switch K3 is turned on.

Because the brightness of the LED lamp is limited by the average current, the number of the divided time-sharing time zones cannot be increased infinitely, and reasonable time zone distribution is required according to the luminous capacity of the LED lamp and the practical application occasion.

In this embodiment, when the LED lamp string is in a time zone in the switching cycle, the voltage conversion controller 130 is configured to control one of the LED switch modules 140 corresponding to the time zone to be turned on, and when the other switch is turned off, the series connection turn-on voltage and the input voltage of the LED lamp string 150 corresponding to the turned-on switch are compared, and according to the comparison result, the switching tube module 120 is controlled to perform a step-down operation, a step-up operation, or a step-up operation, and to perform constant current control on the current of the LED lamp string 150 according to an externally input dimming command. The Dimming commands include Analog Dimming commands (Analog Dimming) and PWM Dimming commands (PWM DIMING).

That is, the input voltage can be boosted or reduced according to the number of the LED lamps, and the current of the LED lamps is controlled, so that compared with the traditional headlamp scheme, the direct conversion of the primary power is realized, and the electric energy conversion efficiency of the system can be greatly improved. In addition, in order to realize that one input power supply 110 can independently control multiple LED strings 150, the corresponding time-sharing time zone of each LED string 150 is divided in one switching period, and the dimming time of the LED string 150 is limited to the time-sharing time zone in the corresponding switching period by connecting the switches in series in each LED string 150, so that the current of different LED strings 150 can be independently regulated by only one additional switch, and analog dimming or PWM dimming is performed.

In this embodiment, the voltage conversion controller 130 may be one of a buck-boost controller, a buck controller, a boost controller, and a single-ended primary inductive conversion (SINGLE ENDED PRIMARY Inductor Converter, SEPIC) controller.

(1) Voltage conversion controller 130 is a Buck-boost controller (Buck-Boost LED Controller):

as shown in fig. 3, when the voltage conversion controller 130 is a buck-boost controller, the switching tube module 120 includes a first switching tube (Q1), a second switching tube (Q2), a third switching tube (Q3), a fourth switching tube (Q4), an inductor (L1), a first capacitor (C1), and a second capacitor (C2).

The Buck-boost controller (Buck-Boost LED Controller) has a first input connected to the Analog Dimming command input (Analog Dimming), a second input connected to the PWM Dimming command input (PWM DIMING), and four first outputs connected to the gates of the first (Q1), second (Q2), third (Q3) and fourth (Q4) switching tubes, respectively, each of which is connected to one of the switches in the LED switching module 140. In fig. 3, n=3 is taken as an example, and each second output is connected to three switches (K1, K2 and K3), respectively.

The drain electrode of the first switching tube (Q1) is respectively connected with an input power supply (VIN) and the first end of a first capacitor (C1), the source electrode of the first switching tube (Q1) is respectively connected with the first end of an inductor (L1) and the drain electrode of a second switching tube (Q2), the second end of the inductor (L1) is respectively connected with the source electrode of a third switching tube (Q3) and the drain electrode of a fourth switching tube (Q4), the drain electrode of the third switching tube (Q3) is connected with the first end of a second capacitor (C2), and the second ends of the first capacitor (C1) and the second capacitor (C2) and the source electrodes of the second switching tube (Q2) and the fourth switching tube (Q4) are grounded;

the first end of each switch in the LED switch module 140 is connected to the first end of the second capacitor (C2), and the second end of each switch is connected to a corresponding LED string 150. In fig. 3, n=3, each switch is connected to three LED strings 150 (string 1, string 2, and string 3), respectively.

As shown in fig. 4, taking the control of the three-way LED light string 150 as an example, each switching period is divided into three time-sharing time zones, K1 (on) time zone, K2 (on) time zone and K3 (on):

① In the time zone of K1 (on), the control switches K1 are turned on, the control switches K2 and K3 are turned off, and the Buck-boost controller (Buck-Boost LED Controller) only supplies power to the LED light string 1, so that the LED light string 1 can be dimmed in an analog dimming or PWM dimming mode. The Buck-boost controller (Buck-Boost LED Controller) can automatically switch the boost, buck or Buck-boost operation mode according to the number of LEDs (related to series on voltage) in the LED string 1.

② In the time zone K2 (on), the control turns on the switch K2, the switch K1 and the switch K3 are turned off, the Buck-boost controller (Buck-Boost LED Controller) only supplies power to the LED lamp string 2, and the LED lamp string 2 can be dimmed in an analog dimming or PWM dimming mode. The Buck-boost controller (Buck-Boost LED Controller) can automatically switch the boost, buck or Buck-boost operating mode according to the number of LEDs (related to the series on voltage) in the LED string 2.

③ In the time zone of K3 (on), the switch K3 is controlled to be turned on, the switches K1 and K2 are controlled to be turned off, and the Buck-boost controller (Buck-Boost LED Controller) only supplies power to the LED lamp string 3, so that the LED lamp string 3 can be dimmed in an analog dimming or PWM dimming mode. The Buck-boost controller (Buck-Boost LED Controller) can automatically switch the boost, buck or Buck-boost operation mode according to the number of LEDs (related to the series on voltage) in the LED string 3.

Fig. 5 shows time zone allocation and control timing for three LED strings 150 that are independently adjusted during one switching cycle.

These three modes of operation are described separately below.

(A) When the series on voltage is smaller than the input voltage and the difference between the input voltage and the series on voltage is greater than the threshold, the first switching tube (Q1) and the second switching tube (Q2) are alternately turned on, the third switching tube (Q3) is kept on, and the fourth switching tube (Q4) is kept off to achieve the step-down operation, as shown in (1) of fig. 6.

When the number of LEDs is small and the series connection conducting voltage is smaller than the input voltage (such as 12V), the circuit enters a step-down mode in which two tubes work simultaneously, the first switching tube (Q1) and the second switching tube (Q2) are conducted alternately, the third switching tube (Q3) is normally on, and the fourth switching tube (Q4) is normally closed. At this time, constant current control is realized on the current of the LED lamp by the duty ratio of the conduction of the first switching tube (Q1). The average current of the LED lamp is adjusted through Analog Dimming (Analog Dimming) or PWM Dimming (PWM DIMMING), so that the brightness adjustment of the LED lamp is realized.

(B) When the series on voltage is greater than the input voltage and the difference between the series on voltage and the input voltage is greater than the threshold, the first switching tube (Q1) remains on, the second switching tube (Q2) remains off, and the third switching tube (Q3) and the fourth switching tube (Q4) are alternately turned on to achieve the boosting operation, as shown in (2) of fig. 6.

When the number of LEDs is large and the series connection conducting voltage is larger than the input voltage (such as 12V), the circuit enters a boosting mode of two tubes working simultaneously, the first switching tube (Q1) is normally on, the second switching tube (Q2) is normally closed, and the third switching tube (Q3) and the fourth switching tube (Q4) are alternately conducted. At the moment, constant current control is realized on the current of the LED lamp through the on-duty ratio of the fourth switching tube (Q4). The average current of the LED lamp is adjusted through Analog Dimming (Analog Dimming) or PWM Dimming (PWM DIMMING), so that the brightness adjustment of the LED lamp is realized.

(C) When the series turn-on voltage is close to the input voltage and the absolute value of the difference between the series turn-on voltage and the input voltage is smaller than the threshold, the first switching tube (Q1) and the second switching tube (Q2) are alternately turned on, and the third switching tube (Q3) and the fourth switching tube (Q4) are alternately turned on to realize the step-up and step-down operation, as shown in (3) of fig. 6.

When the number of LEDs increases to enable the series connection conducting voltage to be close to the input voltage (such as 12V), the circuit enters a lifting mode of four-tube simultaneous operation, the first switching tube (Q1) and the second switching tube (Q2) are conducted alternately, and the third switching tube (Q3) and the fourth switching tube (Q4) are conducted alternately. At the moment, constant current control is realized on the current of the LED lamp by modulating the duty ratio corresponding to the four tubes. The average current of the LED lamp is adjusted through Analog Dimming (Analog Dimming) or PWM Dimming (PWM DIMMING), so that the brightness adjustment of the LED lamp is realized.

Specifically, in the case where the series on voltage is close to the input voltage:

When the series turn-on voltage is smaller than the input voltage, the duty ratios of the first switching tube (Q1) and the second switching tube (Q2) are adjustable, the duty ratios of the third switching tube (Q3) and the fourth switching tube (Q4) are fixed, and the duty ratio of the first switching tube (Q1) and the current of the LED string light 150 are in positive correlation. That is, the larger the duty ratio corresponding to the first switching tube (Q1), the larger the current of the LED string 150; the smaller the corresponding duty cycle of the first switching tube (Q1), the smaller the current of the LED string 150.

When the series connection on voltage is larger than the input voltage, the duty ratio corresponding to the first switching tube (Q1) and the second switching tube (Q2) is fixed, the duty ratio corresponding to the third switching tube (Q3) and the fourth switching tube (Q4) is adjustable, and the duty ratio corresponding to the fourth switching tube and the current of the LED lamp string 150 are in positive correlation. That is, the larger the duty ratio corresponding to the fourth switching tube (Q4), the larger the current of the LED string 150; the smaller the duty cycle corresponding to the fourth switching tube (Q4), the smaller the current of the LED string 150.

(2) The voltage conversion controller 130 is a buck controller (Buck LED Controller):

As shown in fig. 7, when the voltage conversion controller 130 is a buck controller (Buck LED Controller), the switching tube module 120 includes a first switching tube (Q1), a second switching tube (Q2), an inductor (L1), a first capacitor (C1), and a second capacitor (C2).

The buck controller (Buck LED Controller) has a first input connected to the Analog Dimming command input (Analog Dimming), a second input connected to the PWM Dimming command input (PWM DIMING), two first outputs connected to the gates of the first and second switching transistors (Q1, Q2), respectively, and each second output connected to one of the switches in the LED switch module 140, respectively. In fig. 7, n=3, each second output is connected to three switches (K1, K2 and K3), respectively.

The drain electrode of the first switch tube (Q1) is respectively connected with an input power supply (VIN) and the first end of the first capacitor (C1), the source electrode of the first switch tube (Q1) is respectively connected with the first end of the inductor (L1) and the drain electrode of the second switch tube (Q2), the second end of the inductor (L1) is connected with the first end of the second capacitor (C2), and the second ends of the first capacitor (C1) and the second capacitor (C2) and the source electrode of the second switch tube (Q2) are grounded;

The first end of each switch in the LED switch module 140 is connected to the first end of the second capacitor (C2), and the second end of each switch is connected to a corresponding LED string 150. In fig. 7, n=3, each switch is connected to three LED strings 150 (string 1, string 2, and string 3), respectively.

When the voltage conversion controller 130 is a buck controller (Buck LED Controller), the operation principle is similar to that of the circuit operating in the buck mode, and will not be described here.

(3) The voltage conversion controller 130 is a boost controller (Boost LED Controller):

As shown in fig. 8, when the voltage conversion controller 130 is the boost controller (Boost LED Controller), the switching tube module 120 includes a first switching tube (Q1), a second switching tube (Q2), an inductor (L1), a first capacitor (C1), and a second capacitor;

The boost controller (Boost LED Controller) has a first input connected to the Analog Dimming command input (Analog Dimming), a second input connected to the PWM Dimming command input (PWM DIMING), two first outputs connected to the gates of the first and second switching transistors (Q1, Q2), respectively, and each second output connected to one of the switches in the LED switch module 140, respectively. In fig. 8, n=3, each second output is connected to three switches (K1, K2 and K3), respectively.

The first end of the inductor (L1) is respectively connected with an input power supply (VIN) and the first end of the first capacitor (C1), the second end of the inductor (L1) is respectively connected with the source electrode of the first switching tube (Q1) and the drain electrode of the second switching tube (Q2), the drain electrode of the first switching tube (Q1) is connected with the first end of the second capacitor (C2), and the second ends of the first capacitor (C1) and the second capacitor (C2) and the source electrode of the second switching tube (Q2) are grounded;

The first end of each switch in the LED switch module 140 is connected to the first end of the second capacitor (C2), and the second end of each switch is connected to a corresponding LED string 150. In fig. 8, n=3, each switch is connected to three LED strings 150 (string 1, string 2, and string 3), respectively.

When the voltage conversion controller 130 is a boost controller (Boost LED Controller), the working principle is similar to that of the circuit working in the boost mode, and will not be described here.

(4) The voltage conversion controller 130 is a SEPIC controller (SEPIC LED Controller):

As shown in fig. 9, when the voltage conversion controller 130 is the SEPIC controller (SEPIC LED Controller), the switching tube module 120 includes a first switching tube (Q1), a first inductor (L1), a second inductor (L2), a diode (D1), a first capacitor (C1), a second capacitor (C2), and a third capacitor (C3).

The SEPIC controller (SEPIC LED Controller) has a first input connected to the Analog Dimming command input (Analog Dimming), a second input connected to the PWM Dimming command input (PWM DIMING), a first output connected to the gate of the first switching tube (Q1), and each second output connected to a switch of the LED switching module 140. In fig. 9, n=3, each second output is connected to three switches (K1, K2, and K3), respectively.

The first end of the first inductor (L1) is respectively connected with an input power supply (VIN) and the first end of the first capacitor (C1), the second end of the first inductor (L1) is respectively connected with the grid electrode of the first switch tube (Q1) and the first end of the second capacitor (C2), the second end of the second capacitor (C2) is respectively connected with the first end of the second inductor (L2) and the positive electrode of the diode (D1), the negative electrode of the diode (D1) is connected with the first end of the third capacitor (C3), and the second ends of the first capacitor (C1) and the third capacitor (C3), the second end of the second inductor (L2) and the source electrode of the first switch tube (Q1) are grounded;

The first end of each switch in the LED switch module 140 is connected to the first end of the second capacitor (C2), and the second end of each switch is connected to a corresponding LED string 150. In fig. 9, n=3, each switch is connected to three LED strings 150 (string 1, string 2, and string 3), respectively.

When the voltage conversion controller 130 is a SEPIC controller (SEPIC LED Controller), the operation principle is similar to that of the circuit operating in the buck-boost mode, and will not be repeated here.

In summary, the constant current control circuit of the multi-path LED lamp string provided by the embodiment of the present application includes a switching tube module, an LED switching module and a voltage conversion controller, and there is no need to provide a plurality of step-down controllers and a plurality of switching tube modules, so that circuit devices are reduced, circuit cost can be reduced, circuit volume can be reduced, and electric energy conversion efficiency can be improved; in addition, the LED switch module can realize time-sharing control of the multi-path LED lamp strings, effectively improve system efficiency, realize system light weight, improve endurance mileage and realize energy conservation and emission reduction.

As shown in fig. 10, the present embodiment provides a constant current control method applied to the above constant current control circuit, the constant current control method including:

In step 1001, when one of the time slots is in the switching period, one of the switches in the LED switch module corresponding to the time slot is controlled to be closed, and the other switches are controlled to be opened.

As shown in fig. 4, taking the control of the three-way LED light string 150 as an example, each switching period is divided into three time-sharing time zones, K1 (on) time zone, K2 (on) time zone and K3 (on):

① In the K1 (on) time zone, the control switches K1 are open, K2 and K3 are closed.

② In the K2 (on) time zone, the control turns on the switches K2, K1 and K3.

③ In the K3 (on) time zone, the control turns on the switch K3, and the switches K1 and K2 are turned off.

Step 1002, comparing the series connection conducting voltage of the LED string corresponding to the closed switch with the input voltage.

When the number of LEDs is small, the series connection conducting voltage is smaller than the input voltage; when the number of LEDs is large, the series connection conducting voltage is larger than the input voltage.

And step 1003, controlling the switching tube module to perform buck operation, boost operation or buck-boost operation according to the comparison result.

Specifically, controlling the switching tube module to perform the buck operation or the boost operation according to the comparison result may include:

(1) When the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than the threshold value, the switch tube module is controlled to perform step-down operation.

When the number of LEDs is small, the series connection conducting voltage is smaller than the input voltage (such as 12V), and the circuit enters a step-down mode that two tubes work simultaneously.

(2) When the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than the threshold value, the switch tube module is controlled to conduct boosting operation.

When the number of LEDs is large, and the series connection conducting voltage is larger than the input voltage (such as 12V), the circuit enters a boosting mode that two tubes work simultaneously.

(3) When the series connection conducting voltage is close to the input voltage and the absolute value of the difference value between the series connection conducting voltage and the input voltage is smaller than the threshold value, the switching tube module is controlled to perform voltage boosting and dropping operation.

When the number of LEDs increases to make the series connection conducting voltage approach to the input voltage (such as 12V), the circuit enters a step-up and step-down mode in which four tubes work simultaneously.

And step 1004, performing constant current control on the current of the LED lamp string according to an externally input dimming instruction.

The dimming command may be an analog dimming command or a PWM dimming command.

Taking the voltage conversion controller as a buck-boost controller for illustration, then:

(1) When the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than the threshold value, constant current control is realized on the current of the LED lamp through the duty ratio of the first switching tube.

(2) When the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than the threshold value, constant current control is realized on the current of the LED lamp through the duty ratio of the conduction of the fourth switching tube.

(3) When the series conduction voltage is close to the input voltage and the absolute value of the difference between the series conduction voltage and the input voltage is smaller than the threshold value,

When the series connection conducting voltage is smaller than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are adjustable, the duty ratio corresponding to the third switching tube and the fourth switching tube is fixed, and the duty ratio corresponding to the first switching tube and the current of the LED lamp string are in positive correlation;

when the series connection on voltage is larger than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are fixed, the duty ratios corresponding to the third switching tube and the fourth switching tube are adjustable, and the duty ratio corresponding to the fourth switching tube and the current of the LED lamp string are in positive correlation.

In summary, in the constant current control method provided by the embodiment of the application, the constant current control circuit includes a switching tube module, an LED switching module and a voltage conversion controller, so that a plurality of step-down controllers and a plurality of switching tube modules are not required to be arranged, circuit devices are reduced, the circuit cost is reduced, the circuit volume is reduced, and the electric energy conversion efficiency is improved; in addition, the LED switch module can realize time-sharing control of the multi-path LED lamp strings, effectively improve system efficiency, realize system light weight, improve endurance mileage and realize energy conservation and emission reduction.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program for instructing relevant hardware, where the program may be stored in a computer readable storage medium, and the storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.

The above description should not be taken as limiting the embodiments of the application, but rather should be construed to cover all modifications, equivalents, improvements, etc. that may fall within the spirit and principles of the embodiments of the application.

Claims (10)

1. The utility model provides a constant current control circuit of multichannel LED lamp cluster which characterized in that, constant current control circuit includes: the LED lamp string comprises an input power supply, a switching tube module, a voltage conversion controller, an LED switching module and a plurality of LED lamp strings;

The input power supply is connected with the switching tube module, the switching tube module is connected with the LED switching module, the LED switching module is connected with the multi-path LED lamp string, and the voltage conversion controller is respectively connected with the switching tube module and the LED switching module;

When the LED lamp string is in one time-sharing time zone in the switching period, the voltage conversion controller is used for controlling one switch corresponding to the time-sharing time zone in the LED switch module to be closed, when other switches are opened, the series connection conducting voltage and the input voltage of the LED lamp string corresponding to the closed switch are compared, the switching tube module is controlled to perform voltage reduction operation, voltage boosting operation or voltage lifting operation according to a comparison result, and constant current control is performed on the current of the LED lamp string according to an externally input dimming instruction.

2. The constant current control circuit of the multi-channel LED string light of claim 1, wherein the voltage conversion controller is one of a buck-boost controller, a buck controller, a boost controller, a single-ended primary inductance conversion SEPIC controller.

3. The constant current control circuit of the multi-channel LED light string according to claim 2, wherein when the voltage conversion controller is a buck-boost controller, the switching tube module comprises a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, an inductor, a first capacitor and a second capacitor;

The first input end of the buck-boost controller is connected with the analog dimming command input end, the second input end of the buck-boost controller is connected with the Pulse Width Modulation (PWM) dimming command input end, the four first output ends of the buck-boost controller are respectively connected with the grid electrodes of the first switching tube, the second switching tube, the third switching tube and the fourth switching tube, and each second output end of the buck-boost controller is respectively connected with one switch in the LED switching module;

The drain electrode of the first switching tube is respectively connected with the input power supply and the first end of the first capacitor, the source electrode of the first switching tube is respectively connected with the first end of the inductor and the drain electrode of the second switching tube, the second end of the inductor is respectively connected with the source electrode of the third switching tube and the drain electrode of the fourth switching tube, the drain electrode of the third switching tube is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrodes of the second switching tube and the fourth switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

4. The constant current control circuit of the multi-channel LED lamp string according to claim 3, wherein,

When the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than a threshold value, the first switching tube and the second switching tube are alternately conducted, the third switching tube is kept conducting, and the fourth switching tube is kept disconnected so as to realize step-down operation;

When the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than a threshold value, the first switch tube is kept on, the second switch tube is kept off, and the third switch tube and the fourth switch Guan Jiaoti are turned on so as to realize boosting operation;

When the series connection conducting voltage is close to the input voltage and the absolute value of the difference value between the series connection conducting voltage and the input voltage is smaller than a threshold value, the first switch tube and the second switch tube are alternately conducted, and the third switch tube and the fourth switch Guan Jiaoti are conducted so as to realize voltage boosting and dropping operation.

5. The constant current control circuit of a multi-channel LED light string of claim 4, wherein, in the case where the series turn-on voltage is close to the input voltage:

When the series connection conducting voltage is smaller than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are adjustable, the duty ratios corresponding to the third switching tube and the fourth switching tube are fixed, and the duty ratio corresponding to the first switching tube and the current of the LED lamp string are in positive correlation;

When the series connection on voltage is larger than the input voltage, the duty ratios corresponding to the first switching tube and the second switching tube are fixed, the duty ratios corresponding to the third switching tube and the fourth switching tube are adjustable, and the duty ratio corresponding to the fourth switching tube and the current of the LED lamp string are in positive correlation.

6. The constant current control circuit of the multi-channel LED light string according to claim 2, wherein when the voltage conversion controller is a buck controller, the switching tube module comprises a first switching tube, a second switching tube, an inductor, a first capacitor and a second capacitor;

The first input end of the step-down controller is connected with the analog dimming instruction input end, the second input end of the step-down controller is connected with the PWM dimming instruction input end, the two first output ends of the step-down controller are respectively connected with the grid electrodes of the first switching tube and the second switching tube, and each second output end of the step-down controller is respectively connected with one switch in the LED switching module;

The drain electrode of the first switching tube is respectively connected with the input power supply and the first end of the first capacitor, the source electrode of the first switching tube is respectively connected with the first end of the inductor and the drain electrode of the second switching tube, the second end of the inductor is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrode of the second switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

7. The constant current control circuit of the multi-channel LED light string according to claim 2, wherein when the voltage conversion controller is a boost controller, the switching tube module comprises a first switching tube, a second switching tube, an inductor, a first capacitor and a second capacitor;

The first input end of the boost controller is connected with the analog dimming command input end, the second input end of the boost controller is connected with the PWM dimming command input end, the two first output ends of the boost controller are respectively connected with the grid electrodes of the first switching tube and the second switching tube, and each second output end of the boost controller is respectively connected with one switch in the LED switching module;

The first end of the inductor is respectively connected with the input power supply and the first end of the first capacitor, the second end of the inductor is respectively connected with the source electrode of the first switching tube and the drain electrode of the second switching tube, the drain electrode of the first switching tube is connected with the first end of the second capacitor, and the second ends of the first capacitor and the second capacitor and the source electrode of the second switching tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

8. The constant current control circuit of the multi-channel LED light string according to claim 2, wherein when the voltage conversion controller is a SEPIC controller, the switching tube module comprises a first switching tube, a first inductor, a second inductor, a diode, a first capacitor, a second capacitor and a third capacitor;

The first input end of the SEPIC controller is connected with the analog dimming command input end, the second input end of the SEPIC controller is connected with the PWM dimming command input end, one first output end of the SEPIC controller is connected with the grid electrode of the first switch tube, and each second output end of the SEPIC controller is respectively connected with one switch in the LED switch module;

The first end of the first inductor is respectively connected with the input power supply and the first end of the first capacitor, the second end of the first inductor is respectively connected with the grid electrode of the first switch tube and the first end of the second capacitor, the second end of the second capacitor is respectively connected with the first end of the second inductor and the positive electrode of the diode, the negative electrode of the diode is connected with the first end of the third capacitor, and the second ends of the first capacitor and the third capacitor, the second end of the second inductor and the source electrode of the first switch tube are grounded;

the first end of each switch in the LED switch module is connected with the first end of the second capacitor, and the second end of each switch is connected with a corresponding LED light string.

9. A constant current control method for a multi-path LED lamp string, which is used in the constant current control circuit for a multi-path LED lamp string according to any one of claims 1 to 8, the method comprising:

When the LED switch module is in one time-sharing time zone in the switch period, the voltage conversion controller is used for controlling one switch corresponding to the time-sharing time zone in the LED switch module to be closed, and other switches are opened;

Comparing the series connection conducting voltage of the LED lamp string corresponding to the closed switch with the input voltage;

Controlling the switching tube module to perform buck operation, boost operation or buck-boost operation according to the comparison result;

And carrying out constant current control on the current of the LED lamp string according to an externally input dimming instruction.

10. The method for constant current control of a multi-channel LED string light according to claim 9, wherein the step-down operation or the step-up operation of the switching tube module is controlled according to the comparison result, comprising:

when the series connection conducting voltage is smaller than the input voltage and the difference value between the input voltage and the series connection conducting voltage is larger than a threshold value, controlling the switching tube module to perform step-down operation;

when the series connection conducting voltage is larger than the input voltage and the difference value between the series connection conducting voltage and the input voltage is larger than a threshold value, controlling the switching tube module to perform boosting operation;

And when the series connection conducting voltage is close to the input voltage and the absolute value of the difference value between the series connection conducting voltage and the input voltage is smaller than a threshold value, controlling the switching tube module to perform voltage boosting and dropping operation.