A linear constant current control circuit based on automatic switching of LED light modes

Abstract

This invention relates to the field of LED lighting control technology, and provides a linear constant current control circuit based on automatic switching of LED lamp modes. On one hand, an efficiency detection module is set up between the first load and the series-parallel switching module. After the power is turned on, the loss voltage on the first load is detected, and the working efficiency is calculated based on the loss voltage to determine whether the current input power voltage value is appropriate to drive the series-parallel switching module to turn on or off the branch, so that the first load and the second load are connected in parallel or in series. At the same time, the drive current switching module maintains or reduces the circuit voltage divider resistance value to maintain a constant current output. The series-parallel connection mode of the LED group is automatically adjusted by the working efficiency of the LEDs in the circuit. It has strong versatility, can accommodate changes in the VF parameter and voltage range of the LED string, and maintains the circuit efficiency above 80%. The circuit structure is simple, has no signal interference, and the device cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of LED lighting control, and particularly to a linear constant current control circuit based on automatic switching of LED lamp modes. Background Art

[0002] Currently, the mainstream circuits for driving LEDs with constant current are divided into two types, specifically as follows:

[0003] Solution (1): Using a linear constant current circuit to drive the LED circuit with constant current;

[0004] Solution (2): Using a DC-DC constant current chip to drive the LED circuit with constant current.

[0005] Among them, in Solution (1), the linear constant current circuit requires the power supply voltage VIN to be slightly larger than the voltage drop VF_LED of the LED string, but not too large, because the excess voltage needs to be adjusted through an adjustment transistor and a resistor connected in series in the circuit. The larger the value of VIN - VF_LED, the greater the power consumption of the adjustment transistor and the resistor connected in series in the circuit, which affects the efficiency of the circuit and the reliability of the adjustment transistor and the resistor connected in series in the circuit; nor can it be less than the forward voltage drop of the LED string, because when VIN < VF_LED, the LED cannot be normally lit. Therefore, the characteristic of such a circuit is that VIN generally needs to be a fixed value (or change little).

[0006] In Solution (2), the DCDC constant current chip is relatively expensive, and the DC-DC circuit will cause EMC problems.

[0007] There are two characteristics in the application of the LED supplementary lighting circuit built in a vehicle-mounted 4G camera:

[0008] 1. The power input needs to be compatible with two types of vehicle power supplies (12V or 24V);

[0009] 2. The 4G camera will have a built-in GPS antenna, and such products have extremely high requirements for EMC (electromagnetic compatibility).

[0010] Therefore:

[0011] When choosing Solution (1), since there are two types of vehicle power supply voltages (12V or 24V), it is impossible to drive the LED string through a linear constant current circuit to be compatible with the two types of vehicle power supplies (12V or 24V);

[0012] When choosing Solution (2), the DC-DC constant current chip will interfere with sensitive signals such as GPS signals in the 4G camera, and the price of the DCDC constant current chip is relatively high.

[0013] Meanwhile, in existing series-parallel control circuits, if the LED string with different parameters is replaced, the switching timing of the input voltage will also change due to the change in VF value. Since the switching timing is determined by detecting the input voltage, which is a separate part, the switching timing needs to be re-established when the parameters of the LED string change. This requires changing the switching judgment voltage of the detection circuit and the reverse breakdown voltage of the diode, resulting in a lack of circuit flexibility. Summary of the Invention

[0014] This invention provides a linear constant current control circuit based on automatic switching of LED light modes, which solves the technical problems of existing LED constant current control circuits being incompatible with the two power supplies in vehicles, or having signal interference that fails to meet equipment requirements and has high cost, as well as poor flexibility in series-parallel switching.

[0015] To address the above technical problems, this invention provides a linear constant current control circuit based on automatic switching of LED light modes, including a load component and a series-parallel switching module, a current switching module, and an efficiency detection module connected to the load component; the load component includes at least a first load and a second load; one end of the first load is connected to the power input terminal, and the other end is connected to the series-parallel switching module and the efficiency detection module; one end of the second load is connected to the power input terminal through the series-parallel switching module, and the other end is connected to the current switching module; the detection terminal of the efficiency detection module is connected between the first load and the series-parallel switching module, the output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module, and the power supply terminal is connected to the power input terminal;

[0016] The efficiency detection module is used to collect the power supply voltage and the loss voltage on the first load, and then calculate the working efficiency of the load component, and drive the series-parallel switching module and the current switching module according to the working efficiency;

[0017] The series-parallel switching module is used to turn on or off the branch under the drive of the efficiency detection module so that the first load and the second load are connected in parallel or in series.

[0018] The current switching module is used to maintain or reduce the circuit voltage divider resistance value under the drive of the efficiency detection module so that the drive current value is kept constant current output.

[0019] This basic solution improves upon the traditional LED constant current control circuit. Firstly, it incorporates an efficiency detection module connected between the first load and the series-parallel switching module. After power is turned on, it detects the voltage loss on the first load and calculates the operating efficiency based on this voltage to determine whether the current input power voltage is suitable for parallel or series connection of the first and second loads. This drives the series-parallel switching module to turn the branch on or off, allowing the first and second loads to be connected in parallel or series. Simultaneously, the drive current switching module maintains or reduces the circuit's voltage divider resistance to maintain a constant current output. The circuit automatically adjusts the series-parallel connection method of the LED group based on the operating efficiency of the LEDs (load components). This solution is highly versatile, compatible with variations in the VF parameters and voltage range of the LED string, and maintains a circuit efficiency of over 80%. The circuit structure is simple, free from signal interference, and has low cost.

[0020] In a further embodiment, the efficiency detection module includes a comparator, a first resistor, and a second resistor; one end of the first resistor serves as a power supply terminal connected to the power input terminal, and the other end is connected to the non-inverting input terminal of the comparator and grounded through the second resistor; the inverting input terminal of the comparator serves as a detection terminal connected between the first load and the series-parallel switching module, and the output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module.

[0021] The first resistor and the second resistor are connected in series to form a voltage divider circuit. The voltage divider circuit is used to set the switching reference voltage of the comparator, that is, to set the reference value of the loss efficiency.

[0022] The comparator is used to acquire the loss voltage on the first load and compare it with the switching reference voltage, and then output a parallel signal or a series signal according to the comparison result.

[0023] This solution uses a comparator as its core for efficiency detection. On one hand, it utilizes a voltage divider circuit formed by a first and second resistor in series to set a benchmark value for loss efficiency (i.e., setting the optimal switching timing for series-parallel operation). The voltage divider allows for power detection compatible with different power supply voltage inputs. On the other hand, the detection terminal (inverting input) is connected to the output terminal of the first load (between the first load and the series-parallel switching module) to continuously monitor the circuit's loss efficiency. This efficiency is compared with the comparator, and a parallel or series signal (high or low level) is output for series-parallel control. Because it uses efficiency detection, it is compatible with changes in input power supply voltage and load component parameters without requiring modifications to circuit parameters due to variations in input voltage range or LED parameters, thus enhancing the overall circuit's versatility.

[0024] In a further embodiment, the current switching module includes a first switching module, a shunt circuit, and a first voltage divider resistor; the enable terminal of the first switching module is connected to the main controller, the input terminal is connected to the load component and the series-parallel switching module, and the output terminal is connected to the shunt circuit and the first voltage divider resistor; the control terminal of the shunt circuit is connected to the efficiency detection module.

[0025] The first switching module conducts the circuit under the control of the main controller, thereby energizing the load component;

[0026] The shunt circuit is turned on when the parallel signal is received, and then connected in parallel with the first voltage divider resistor to reduce the voltage divider resistance value of the circuit and perform current shunt to maintain constant current output; it is turned off when the series signal is received to maintain the voltage divider resistance value of the circuit to maintain constant current output.

[0027] In a further embodiment, the first switching module includes a first switching transistor, a second switching transistor, and a third resistor. When both the first and second switching transistors are NPN transistors:

[0028] The collector of the first switching transistor is connected to the load component and the series-parallel switching module, the base is connected to the main controller through the third resistor as an enable terminal, and the emitter is grounded through the first voltage divider resistor and also connected to the shunt circuit; the base of the second switching transistor is connected to the emitter of the first switching transistor, the collector is connected to the base of the first switching transistor, and the emitter is grounded.

[0029] This solution utilizes a combination of switching transistors (first switching transistor and second switching transistor) for circuit on / off control, offering long service life, safety and reliability, no mechanical wear, fast switching speed, and small size.

[0030] In a further embodiment, the shunt circuit includes a third switch, a fourth resistor, a fifth resistor, and a second voltage divider resistor. When the third switch is an N-channel MOSFET:

[0031] The gate of the third switching transistor is connected to the output terminal of the efficiency detection module through the fourth resistor, the source is grounded, and the drain is connected to the first switching module through the second voltage divider resistor; one end of the fifth resistor is connected to the gate of the three switching transistors, and the other end is grounded.

[0032] This scheme sets up a shunt circuit in parallel with the first voltage divider resistor, and the third switch is connected in series with the second voltage divider resistor. When a parallel signal or a series signal is received, the switch is controlled to turn on or off. When the power supply voltage is 12V, the second voltage divider resistor is connected in parallel with the first voltage divider resistor to reduce the voltage divider resistance of the circuit so that the drive current value is kept constant current output.

[0033] In a further embodiment, the series-parallel switching module includes a second switching circuit and a third switching circuit. The second switching circuit is connected in series between the second load and the power input terminal, and its control terminal is connected to the output terminal of the efficiency detection module. The third switching circuit is connected to the output terminal of the first load, the input terminal of the second load, and the current switching module, and its control terminal is connected to the efficiency detection module.

[0034] When the parallel / series signal is received, the second switching circuit turns on / off the loop between the second load and the power input terminal; at the same time, the third switching circuit turns on / off the loop between the first load and the current switching module, so that the first load and the second load are connected in parallel / series.

[0035] In a further embodiment, the second switching circuit includes a fourth switching transistor, a fifth switching transistor, and a sixth to a tenth resistor. When the fourth switching transistor is a P-channel MOSFET and the fifth switching transistor is an NPN transistor:

[0036] The gate of the fourth switch is connected to the collector of the fifth switch via the seventh resistor, the source is connected to the power input terminal, and the drain is connected to the second load; the two ends of the sixth resistor are connected to the gate and source of the fourth switch; the emitter of the fifth switch is grounded, and the base is connected to the power input terminal via the eighth and ninth resistors; the two ends of the tenth resistor are connected to the emitter and base of the fifth switch; the output terminal of the efficiency detection module is connected between the eighth and ninth resistors.

[0037] This scheme uses a combination of switching transistors (fourth and fifth switching transistors) to control the power input of the second load. The fifth switching transistor is used to obtain the parallel or series signal output by the efficiency detection module, and then the power supply voltage is directly input to the second load by turning the fourth switching transistor on or off, so as to realize the parallel or series connection of the first load and the second load.

[0038] In a further embodiment, the third switching circuit includes a first diode and a sixth switching transistor, wherein the sixth switching transistor is an N-channel MOSFET:

[0039] The drain of the sixth switching transistor is connected to the output terminal of the first load and the input terminal of the efficiency detection module, the gate is connected to the output terminal of the efficiency detection module as a control terminal, and the source is connected to the output terminal of the second load and the current switching module; the anode of the first diode is connected to the drain of the sixth switching transistor, and the cathode is connected to the input terminal of the second load.

[0040] This scheme connects a first diode between the first load and the second load to establish a unidirectional series circuit. The sixth switch is connected between the output terminal of the first load and the current switching module. The first load and the second load are connected in parallel or in series according to the parallel signal or series signal.

[0041] In a further embodiment, the first load includes a protection resistor and several LED loads connected in series, and the first load and the second load have the same structure. Attached Figure Description

[0042] Figure 1 This is a partial structural diagram of a linear constant current control circuit based on automatic switching of LED light modes provided in an embodiment of the present invention;

[0043] Figure 2 This is a hardware circuit diagram of the efficiency detection module provided in an embodiment of the present invention;

[0044] Figure 3 This is a hardware circuit diagram of the current switching module provided in an embodiment of the present invention;

[0045] Wherein: comparator U1, first switch Q1 to sixth switch Q6, first resistor R1 to tenth resistor R10, first voltage divider resistor R11, second voltage divider resistor R12, protection resistor R13 / R14, LED load LED1 to LED10. Detailed Implementation

[0046] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0047] This invention provides a linear constant current control circuit based on automatic switching of LED light modes, such as... Figures 1-3 As shown, in this embodiment, a load component is included, along with a series-parallel switching module, a current switching module, and an efficiency detection module connected to the load component. The load component includes at least a first load and a second load. One end of the first load is connected to the power input terminal, and the other end is connected to the series-parallel switching module and the efficiency detection module. One end of the second load is connected to the power input terminal via the series-parallel switching module, and the other end is connected to the current switching module. The detection terminal of the efficiency detection module is connected between the first load and the series-parallel switching module, the output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module, and the power supply terminal is connected to the power input terminal.

[0048] The efficiency detection module is used to collect the power supply voltage and the loss voltage on the first load, and then calculate the working efficiency of the load components, and drive the series-parallel switching module and the current switching module according to the working efficiency;

[0049] The series-parallel switching module is used to turn on or off branches under the drive of the efficiency detection module, so that the first load and the second load are connected in parallel or in series.

[0050] The current switching module is used to maintain or reduce the voltage divider resistance value of the circuit under the drive of the efficiency detection module, so that the drive current value is kept constant.

[0051] In this embodiment, the efficiency detection module includes a comparator U1, a first resistor R1, and a second resistor R2. One end of the first resistor R1 serves as a power supply terminal and is connected to the power input terminal, while the other end is connected to the non-inverting input terminal of the comparator U1 and is also grounded through the second resistor R2. The inverting input terminal of the comparator U1 serves as a detection terminal and is connected between the first load and the series-parallel switching module. The output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module.

[0052] The first resistor R1 and the second resistor R2 are connected in series to form a voltage divider circuit. The voltage divider circuit is used to set the switching reference voltage of comparator U1, that is, to set the reference value of loss efficiency.

[0053] Comparator U1 is used to acquire the loss voltage on the first load and compare it with the switching reference voltage, and then output a parallel signal or a series signal based on the comparison result.

[0054] See Figure 2 The efficiency detection working principle of this embodiment is as follows:

[0055] By comparing the voltage at point b with the voltage at point c, the voltage at point a (i.e., the parallel signal or the series signal) is obtained, thus determining the series and parallel connection relationship of the LED group.

[0056] The voltage at point c is:

[0057]

[0058] The voltage at point b is:

[0059]

[0060] Compare the voltage at point b with the voltage at point c. If the voltage at point b is greater than the voltage at point c, then:

[0061]

[0062]

[0063] VIN is the power supply voltage, VF is the forward voltage of the first or second load of a single group, and the value of (VIN-VF) / VIN is the loss efficiency of the drive circuit when the loads are connected in parallel. In the circuit design, a certain loss efficiency needs to be reserved for the regulating tube and the series resistor as necessary losses when adjusting the current. That is, setting the value of R2 / (R1+R2) also sets the minimum value of (VIN-VF) / VIN when the comparator U1 level switches.

[0064] In this embodiment, the series-parallel switching is taken as an example, with both the first and second loads being LED light strings (each string containing 5 LED loads, i.e., the VF value of the LED string is 10V), the input voltage being 12V / 24V, and the operating efficiency being less than 45.5%.

[0065] When the first load and the second load are connected in parallel, if VIN = 12V, then the loss efficiency (VIN - VF) / VIN is greater than R16 / (R15 + R16), which is approximately 54.5%. The loss efficiency is approximately 54.5%, meaning the utilization efficiency is approximately 45.5%. When the comparator outputs a low level, the first and second loads switch to series mode, at which point the VF value doubles, and the efficiency doubles. For example:

[0066] If VIN = 24V, the detected efficiency VF / VIN ≈ 41.67% (< 45.5%), then the comparator outputs a high level, and the first and second loads switch to series mode with an efficiency of VF*2 / VIN ≈ 83.33%. If VIN = 12V and VF = 10V, the detected efficiency VF / VIN ≈ 83.33% (> 45.5%), and the first and second loads switch to parallel mode.

[0067] Conversely, if the loss efficiency (VIN-VF) / VIN is greater than R16 / (R15+R16) when LED groups are connected in series, then the first load and the second load switch to parallel mode.

[0068] Where VF is the VF value when two sets of LEDs are connected in parallel in parallel mode, and VF*2 is the VF value when two sets of LEDs are connected in series in series mode.

[0069] This case only involves optimizing the series-parallel connection mode.

[0070] This embodiment uses comparator U1 as the core for efficiency detection. On one hand, it utilizes a voltage divider circuit formed by the first resistor R1 and the second resistor R2 connected in series to set a reference value for loss efficiency (i.e., setting the optimal switching timing for series-parallel operation). The voltage divider allows for power detection compatible with different power supply voltage inputs. On the other hand, the detection terminal (inverting input terminal) is connected to the output terminal of the first load (between the first load and the series-parallel switching module) to continuously monitor the circuit's loss efficiency. This efficiency is input to comparator U1 for comparison, and then outputs a parallel signal or a series signal (high or low level) for series-parallel control. Because it uses efficiency detection, it is compatible with changes in input power supply voltage and load component parameters without requiring modifications to circuit parameters due to changes in the input voltage range or LED lamp parameters, making the entire circuit more versatile.

[0071] In this embodiment, the current switching module includes a first switching module, a shunt circuit, and a first voltage divider resistor R11; the enable terminal of the first switching module is connected to the main controller, the input terminal is connected to the load component and the series-parallel switching module, and the output terminal is connected to the shunt circuit and the first voltage divider resistor R11; the control terminal of the shunt circuit is connected to the efficiency detection module.

[0072] The first switching module conducts the circuit under the control of the main controller, thereby energizing the load components;

[0073] The shunt circuit turns on when it receives a parallel signal, and then connects in parallel with the first voltage divider resistor R11 to reduce the voltage divider resistance of the circuit and shunt the current to maintain a constant current output; it turns off when it receives a series signal to maintain the voltage divider resistance of the circuit to maintain a constant current output.

[0074] In this embodiment, the main controller is a conventional processing chip with data processing capabilities, such as an MCU, used for the wake-up circuit; a push-button switch can also be used instead, and this embodiment does not impose any restrictions.

[0075] In this embodiment, the first switching module includes a first switching transistor Q1, a second switching transistor Q2, and a third resistor R3. When both the first switching transistor Q1 and the second switching transistor Q2 are NPN transistors:

[0076] The collector of the first switching transistor Q1 is connected to the load component and the series-parallel switching module. The base is connected to the main controller through the third resistor R3 as the enable terminal. The emitter is grounded through the first voltage divider resistor R11 and is also connected to the shunt circuit. The base of the second switching transistor Q2 is connected to the emitter of the first switching transistor Q1, the collector is connected to the base of the first switching transistor Q1, and the emitter is grounded.

[0077] This embodiment uses a combination of switching transistors (first switching transistor Q1 and second switching transistor Q2) for circuit on / off control, which has a long service life, is safe and reliable, has no mechanical wear, fast switching speed, and small size.

[0078] In this embodiment, the shunt circuit includes a third switch Q3, a fourth resistor R4, a fifth resistor R5, and a second voltage divider resistor R12. When the third switch Q3 is an N-channel MOSFET:

[0079] The gate of the third switch Q3 is connected to the output terminal of the efficiency detection module through the fourth resistor R4, the source is grounded, and the drain is connected to the first switch module through the second voltage divider resistor R12; one end of the fifth resistor R5 is connected to the gate of the three switches, and the other end is grounded.

[0080] Specifically, taking an example where both the first and second loads are LED light strings (each string includes 5 LED loads):

[0081] Assuming V(Rs) = 0.684V, then the drive current I = 0.684 / Rs (RS is the voltage divider resistance of the circuit). If the third switch Q3 is off, then Rs = R11 = 3.6R, and the drive current is approximately 190mA; if the third switch Q3 is on, then Rs = R11*R12 / (R11+R12) = 1.8R, and the drive current is approximately 380mA.

[0082] When VIN = 12V, comparator U1 outputs a high level (i.e., point a is at a high level), the third switch Q3 is turned on, Rs = 1.8R, and the constant current drive current is about 380mA.

[0083] When VIN = 24V, comparator U1 outputs a low level (i.e., point a is low level), the third switch Q3 is cut off, Rs = 3.6R, and the constant current drive current is about 190mA.

[0084] Assuming the VF value of a single LED load is 2V, we know that:

[0085] When VIN = 12V, the first and second loads are connected in parallel, and the constant current drive current is approximately 380mA (i.e., each of the two LED strings receives approximately 190mA). Therefore, the voltage distributed across Rs is VIN - LED_VF = 12V - 2V * 5 LEDs = 2V, allowing the circuit to operate relatively stably.

[0086] When VIN = 24V, the first and second loads are in series, and the constant current drive current is approximately 190mA. Therefore, the voltage across Rs is VIN - LED_VF = 24V - 2V * 10 LEDs = 4V, and the circuit can operate relatively stably.

[0087] In this embodiment, a shunt circuit is set up in parallel with the first voltage divider resistor R11. The third switch Q3 is connected in series with the second voltage divider resistor R12. When a parallel signal or a series signal is received, the switch is controlled to turn on or off. When the power supply voltage is 12V, the second voltage divider resistor R12 is connected in parallel with the first voltage divider resistor R11 to reduce the voltage divider resistance of the circuit so that the drive current value is kept constant current output.

[0088] In this embodiment, the series-parallel switching module includes a second switching circuit and a third switching circuit. The second switching circuit is connected in series between the second load and the power input terminal, and its control terminal is connected to the output terminal of the efficiency detection module. The third switching circuit is connected to the output terminal of the first load, the input terminal of the second load, and the current switching module, and its control terminal is connected to the efficiency detection module.

[0089] When a parallel / series signal is received, the second switching circuit turns on / off the loop between the second load and the power input terminal; at the same time, the third switching circuit turns on / off the loop between the first load and the current switching module, so that the first load and the second load are connected in parallel / series.

[0090] In this embodiment, the second switching circuit includes a fourth switching transistor Q4, a fifth switching transistor Q5, and a sixth resistor R6 to a tenth resistor R10. When the fourth switching transistor Q4 is a P-channel MOSFET and the fifth switching transistor Q5 is an NPN transistor:

[0091] The gate of the fourth switch Q4 is connected to the collector of the fifth switch Q5 through the seventh resistor R7, the source is connected to the power input terminal, and the drain is connected to the second load; the two ends of the sixth resistor are connected to the gate and source of the fourth switch Q4; the emitter of the fifth switch Q5 is grounded, and the base is connected to the power input terminal through the eighth resistor R8 and the ninth resistor R9; the two ends of the tenth resistor R10 are connected to the emitter and base of the fifth switch Q5; the output terminal of the efficiency detection module is connected between the eighth resistor R8 and the ninth resistor R9.

[0092] In this embodiment, a combination of switching transistors (fourth switching transistor Q4 and fifth switching transistor Q5) is used to control the power input of the second load. The fifth switching transistor Q5 is used to obtain the parallel or series signal output by the efficiency detection module, and then the power supply voltage is directly input to the second load by turning on or off the fourth switching transistor Q4, so as to realize the parallel or series connection of the first load and the second load.

[0093] In this embodiment, the third switching circuit includes a first diode and a sixth switching transistor Q6. When the sixth switching transistor Q6 is an N-channel MOSFET:

[0094] The drain of the sixth switching transistor Q6 is connected to the output terminal of the first load and the input terminal of the efficiency detection module, the gate is connected to the output terminal of the efficiency detection module as the control terminal, and the source is connected to the output terminal of the second load and the current switching module; the anode of the first diode is connected to the drain of the sixth switching transistor Q6, and the cathode is connected to the input terminal of the second load.

[0095] In this embodiment, taking LED light strings as an example where both the first load and the second load are LED light strings, the series-parallel switching principle is as follows:

[0096] If VIN = 12V, comparator U1 outputs a high level. At this time, the fifth switch Q5 and the fourth switch Q4 (PMOS) are turned on, and the sixth switch Q6 is turned on. The two LED strings ("fourth switch Q4, R14 / LED6-LED10" and "R13, LED1-LED5, sixth switch Q6") are connected in parallel. The current paths for the two LED strings are VIN > Q4 > R14 > LED6-LED10 > Q1 and VIN > R13 > LED1-LED5 > Q6 > Q1, respectively.

[0097] If VIN = 24V, comparator U1 outputs a low level. At this time, the fifth switch Q5 and the fourth switch Q4 (PMOS) are cut off, and the sixth switch Q6 is cut off. At this time, the two sets of LED strings are in series mode, and the current path is VIN > R13 > LED1-LED5 > D1 > R14 > LED6-LED10 > Q1.

[0098] In this embodiment, a first diode is connected between the first load and the second load to establish a unidirectional series circuit. The sixth switch Q6 is connected between the output terminal of the first load and the current switching module. The first load and the second load are connected in parallel or in series according to the parallel signal or series signal.

[0099] In this embodiment, the first load includes a protection resistor connected in series and several LED loads. The first load and the second load have the same structure. In other embodiments, the load components include, but are not limited to, LED strings. See also Figure 1 The first load includes a protection resistor R13 and LED1 to LED5 connected in series; the second load includes a protection resistor R14 and LED6 to LED10 connected in series (this embodiment does not limit the number of LED loads, and users can set them according to their needs).

[0100] This invention improves upon traditional LED constant current control circuits by incorporating an efficiency detection module connected between the first load and the series-parallel switching module. After power is applied, the module detects the voltage loss on the first load and calculates the operating efficiency based on this voltage to determine whether the current input power voltage is suitable for parallel or series connection of the first and second loads. This drives the series-parallel switching module to either turn the branch on or off, allowing the first and second loads to be connected in parallel or series. Simultaneously, the current switching module maintains or reduces the circuit's voltage divider resistance to maintain a constant current output. The circuit automatically adjusts the series-parallel connection method of the LED group based on the operating efficiency of the LEDs (load components). This design offers strong versatility, is compatible with variations in the VF parameters and voltage range of the LED string, and maintains a circuit efficiency of over 80%. The circuit structure is simple, free from signal interference, and has low cost.

[0101] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A linear constant current control circuit based on automatic switching of LED light modes, characterized in that: The system includes a load component, and a series-parallel switching module, a current switching module, and an efficiency detection module connected to the load component. The load component includes at least a first load and a second load. One end of the first load is connected to a power input terminal, and the other end is connected to the series-parallel switching module and the efficiency detection module. One end of the second load is connected to the power input terminal through the series-parallel switching module, and the other end is connected to the current switching module. The detection terminal of the efficiency detection module is connected between the first load and the series-parallel switching module, the output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module, and the power supply terminal is connected to the power input terminal. The efficiency detection module is used to collect the power supply voltage and the loss voltage on the first load, and then calculate the working efficiency of the load component, and drive the series-parallel switching module and the current switching module according to the working efficiency; The series-parallel switching module is used to turn on or off the branch under the drive of the efficiency detection module so that the first load and the second load are connected in parallel or in series. The current switching module is used to maintain or reduce the circuit voltage divider resistance value under the drive of the efficiency detection module so that the drive current value is kept constant current output. The efficiency detection module includes a comparator, a first resistor, and a second resistor; one end of the first resistor serves as a power supply terminal and is connected to the power input terminal, and the other end is connected to the non-inverting input terminal of the comparator and is also grounded through the second resistor; the inverting input terminal of the comparator serves as a detection terminal and is connected between the first load and the series-parallel switching module, and the output terminal is connected to the control terminal of the series-parallel switching module and the control terminal of the current switching module. The first resistor and the second resistor are connected in series to form a voltage divider circuit. The voltage divider circuit is used to set the switching reference voltage of the comparator, that is, to set the reference value of the loss efficiency. The comparator is used to acquire the loss voltage on the first load and compare it with the switching reference voltage, and then output a parallel signal or a series signal according to the comparison result.

2. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 1, characterized in that: The current switching module includes a first switching module, a shunt circuit, and a first voltage divider resistor; the enable terminal of the first switching module is connected to the main controller, the input terminal is connected to the load component and the series-parallel switching module, and the output terminal is connected to the shunt circuit and the first voltage divider resistor; the control terminal of the shunt circuit is connected to the efficiency detection module. The first switching module conducts the circuit under the control of the main controller, thereby energizing the load component; The shunt circuit is turned on when the parallel signal is received, and then connected in parallel with the first voltage divider resistor to reduce the voltage divider resistance value of the circuit and perform current shunt to maintain constant current output; it is turned off when the series signal is received to maintain the voltage divider resistance value of the circuit to maintain constant current output.

3. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 2, characterized in that, The first switching module includes a first switching transistor, a second switching transistor, and a third resistor. When both the first and second switching transistors are NPN transistors: The collector of the first switching transistor is connected to the load component and the series-parallel switching module, the base is connected to the main controller through the third resistor as an enable terminal, and the emitter is grounded through the first voltage divider resistor and also connected to the shunt circuit; the base of the second switching transistor is connected to the emitter of the first switching transistor, the collector is connected to the base of the first switching transistor, and the emitter is grounded.

4. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 3, characterized in that, The shunt circuit includes a third switch, a fourth resistor, a fifth resistor, and a second voltage divider resistor. When the third switch is an N-channel MOSFET: The gate of the third switching transistor is connected to the output terminal of the efficiency detection module through the fourth resistor, the source is grounded, and the drain is connected to the first switching module through the second voltage divider resistor; one end of the fifth resistor is connected to the gate of the three switching transistors, and the other end is grounded.

5. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 1, characterized in that: The series-parallel switching module includes a second switching circuit and a third switching circuit. The second switching circuit is connected in series between the second load and the power input terminal, and its control terminal is connected to the output terminal of the efficiency detection module. The third switching circuit is connected to the output terminal of the first load, the input terminal of the second load, and the current switching module, and its control terminal is connected to the efficiency detection module. When the parallel / series signal is received, the second switching circuit turns on / off the loop between the second load and the power input terminal; at the same time, the third switching circuit turns on / off the loop between the first load and the current switching module, so that the first load and the second load are connected in parallel / series.

6. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 5, characterized in that, The second switching circuit includes a fourth switching transistor, a fifth switching transistor, and a sixth to a tenth resistor. When the fourth switching transistor is a P-channel MOSFET and the fifth switching transistor is an NPN transistor: The gate of the fourth switch is connected to the collector of the fifth switch via the seventh resistor, the source is connected to the power input terminal, and the drain is connected to the second load; the two ends of the sixth resistor are connected to the gate and source of the fourth switch; the emitter of the fifth switch is grounded, and the base is connected to the power input terminal via the eighth and ninth resistors; the two ends of the tenth resistor are connected to the emitter and base of the fifth switch; the output terminal of the efficiency detection module is connected between the eighth and ninth resistors.

7. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 5, characterized in that, The third switching circuit includes a first diode and a sixth switching transistor. When the sixth switching transistor is an N-channel MOSFET: The drain of the sixth switching transistor is connected to the output terminal of the first load and the input terminal of the efficiency detection module, the gate is connected to the output terminal of the efficiency detection module as a control terminal, and the source is connected to the output terminal of the second load and the current switching module; the anode of the first diode is connected to the drain of the sixth switching transistor, and the cathode is connected to the input terminal of the second load.

8. The linear constant current control circuit based on automatic switching of LED light modes as described in claim 1, characterized in that: The first load includes a protection resistor and several LED loads connected in series. The first load and the second load have the same structure.

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