A segmented LED driver circuit and lighting system

Abstract

This utility model relates to a segmented LED driving circuit and lighting system, including a DC source, a first lamp segment, a second lamp segment, a diode, a first constant current switching circuit, a second constant current switching circuit, and a third constant current switching circuit. The positive terminal of the first lamp segment is connected to the DC source, the negative terminal of the first lamp segment is connected to the positive terminal of the diode, and the negative terminal of the diode is connected to the second lamp segment. The first terminal of the first constant current switching circuit is connected to the DC source, and the second terminal is connected to the negative terminal of the diode. The first terminal of the second constant current switching circuit is connected to the negative terminal of the first lamp segment, and the second terminal is grounded. The first terminal of the third constant current switching circuit is connected to the negative terminal of the second lamp segment, and the second terminal is grounded. In this utility model, when the DC source voltage is low, the first and second lamp segments are connected in parallel; when the DC source voltage is high, the first and second lamp segments are connected in series. The two lamp segments can always maintain synchronous lighting and extinguishing, and the lamp segments always maintain current sharing control, thereby ensuring the lighting effect.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to a segmented LED driving circuit and lighting system. Background Technology

[0002] Currently, lamp tubes containing multiple LED segments can be driven and controlled using a segmented linear driver. The segmented linear driver illuminates a corresponding number of segments based on the input voltage level. When the input voltage level is high, all segments in the lamp tube can be lit. However, when the input voltage level is low, only some segments in the lamp tube are lit, resulting in uneven brightness and affecting the lighting effect. Utility Model Content

[0003] To address at least one of the aforementioned technical problems, this utility model proposes a segmented LED driving circuit and lighting system.

[0004] According to some embodiments of this utility model, a segmented LED driving circuit is provided, including a DC source, a first lamp segment, a second lamp segment, a diode, a first constant current switching circuit, a second constant current switching circuit, and a third constant current switching circuit. Both the first and second lamp segments are composed of LED beads connected in series. The positive terminal of the first lamp segment is connected to the DC source, the negative terminal of the first lamp segment is connected to the positive terminal of the diode, and the negative terminal of the diode is connected to the positive terminal of the second lamp segment. The first terminal of the first constant current switching circuit is connected to the DC source, the second terminal of the first constant current switching circuit is connected to the negative terminal of the diode, and the third constant current switching circuit... The first end of the circuit is connected to the negative terminal of the first lamp segment, the second end of the second constant current switch circuit is grounded, the first end of the third constant current switch circuit is connected to the negative terminal of the second lamp segment, and the second end of the third constant current switch circuit is grounded; when the DC source voltage is less than a preset voltage value, the first constant current switch circuit, the second constant current switch circuit, and the third constant current switch circuit are all turned on, and the currents of the second constant current switch circuit and the third constant current switch circuit are equal; when the DC source voltage is greater than or equal to the preset voltage value, the first constant current switch circuit and the second constant current switch circuit are both turned off, and the third constant current switch circuit is turned on.

[0005] In some possible implementations, the first constant current switching circuit includes a first operational amplifier and a first switching transistor. The first input terminal of the first operational amplifier receives a first preset voltage, and the second input terminal of the first operational amplifier receives a sampling signal characterizing the DC source voltage. The first terminal of the first switching transistor is connected to the DC source, the second terminal of the first switching transistor is connected to the negative terminal of the diode, and the control terminal of the first switching transistor is connected to the output terminal of the first operational amplifier.

[0006] In some possible implementations, the first constant current switching circuit further includes a current sampling circuit, wherein the sampling signal characterizing the DC source voltage is a current sampling signal obtained through the current sampling circuit; wherein the current sampling circuit includes a current sampling resistor and a differential circuit, the first end of the current sampling resistor is connected to the negative terminal of the diode, and the second end of the current sampling resistor is connected to the positive terminal of the second lamp segment; the two ends of the current sampling resistor are connected to the second input terminal of the first operational amplifier through the differential circuit.

[0007] In some possible implementations, the first constant current switching circuit further includes a voltage detection circuit, wherein the sampling signal characterizing the DC source voltage is a voltage sampling signal obtained through the voltage detection circuit; wherein the voltage detection circuit includes a first voltage divider resistor, a second voltage divider resistor, and a voltage sampling resistor, wherein a first end of the first voltage divider resistor is connected to the DC source, a second end of the first voltage divider resistor is connected to a first end of the second voltage divider resistor, a second end of the second voltage divider resistor is connected to the positive terminal of the second lamp segment, a first end of the voltage sampling resistor is connected to a first end of the second voltage divider resistor, and a second end of the voltage sampling resistor is connected to a second input terminal of the first operational amplifier.

[0008] In some possible implementations, the first constant current switching circuit further includes a reference generation circuit, the input terminal of which is connected to the DC source, and the output terminal of which is connected to the first input terminal of the first operational amplifier. The reference generation circuit is used to generate the first preset voltage.

[0009] In some possible implementations, the segmented LED driving circuit includes a single-segment linear LED driver, in which the first constant current switching circuit is integrated.

[0010] In some possible implementations, the second constant current switching circuit includes a second operational amplifier and a second switching transistor. The first terminal of the second switching transistor is connected to the negative terminal of the first lamp segment, the second terminal of the second switching transistor is connected to the first terminal of a feedback resistor, the second terminal of the feedback resistor is grounded, the control terminal of the second switching transistor is connected to the output terminal of the second operational amplifier, the first input terminal of the second operational amplifier receives a second preset voltage, and the second input terminal of the second operational amplifier is connected to the first terminal of the feedback resistor.

[0011] In some possible implementations, the third constant current switching circuit includes a third operational amplifier and a third switching transistor. The first terminal of the third switching transistor is connected to the negative terminal of the second lamp segment, the second terminal of the third switching transistor is connected to the first terminal of the feedback resistor, the control terminal of the third switching transistor is connected to the output terminal of the third operational amplifier, the first input terminal of the third operational amplifier receives a third preset voltage, and the second input terminal of the third operational amplifier is connected to the first terminal of the feedback resistor.

[0012] In some possible implementations, the segmented LED driving circuit includes a segmented linear LED driver, in which the second constant current switching circuit and the third constant current switching circuit are integrated.

[0013] In some possible implementations, the DC source is a rectifier, the input terminal of which is connected to an AC power supply, the positive output terminal of which is connected to the positive terminal of the first lamp segment and the first terminal of the first constant current switching circuit, and the negative output terminal of which is connected to the second terminal of the second constant current switching circuit.

[0014] According to some embodiments of the present invention, a lighting system is provided, including the segmented LED driving circuit described in any one of the above embodiments.

[0015] This utility model has the following beneficial effects:

[0016] The segmented LED driving circuit of this invention includes a diode and three constant current switching circuits. The diode is positioned between two LED segments. When the DC source output is low, all three constant current switching circuits are turned on, and the first and second segments are connected in parallel. When the DC source output is high, only the third constant current switching circuit is turned on, and the first and second segments are connected in series. Based on the three constant current switching circuits, the two LED segments can always maintain synchronous lighting and extinguishing, and the segments always maintain current sharing control, thereby ensuring the lighting effect.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the present invention.

[0018] Other features and aspects of the present invention will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions and advantages in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A circuit schematic diagram of a piecewise linearly driven LED according to the prior art is shown.

[0021] Figure 2 A circuit structure diagram of a segmented LED driving circuit according to an embodiment of the present invention is shown;

[0022] Figure 3 A circuit structure diagram of a first constant current switch circuit based on current-controlled turn-off according to an embodiment of the present invention is shown.

[0023] Figure 4 A circuit structure diagram of a first constant current switch circuit based on voltage-controlled turn-off according to an embodiment of the present invention is shown.

[0024] Figure 5 A circuit diagram of a second constant current switching circuit according to an embodiment of the present invention is shown.

[0025] In the picture,

[0026] 1-DC source; 2-First lamp segment; 3-Diode; 4-Second lamp segment; 5-First constant current switching circuit; 6-Second constant current switching circuit; 7-Third constant current switching circuit; U1-First operational amplifier; U2-Second operational amplifier; U3-Third operational amplifier; U4-Fourth operational amplifier; Q1-First switching transistor; Q2-Second switching transistor; Q3-Third switching transistor; Q4-Fourth switching transistor; Ri-Current sampling resistor; Rv-Voltage sampling resistor; R1-First voltage divider resistor; R2-Second voltage divider resistor; Rf-Feedback resistor. Detailed Implementation

[0027] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0029] Various exemplary embodiments, features, and aspects of the present invention will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0030] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0031] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0032] Furthermore, to better illustrate this utility model, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this utility model can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this utility model.

[0033] Currently, lamps containing multiple LED segments can be driven and controlled using a piecewise linear driver. The circuit for a piecewise linear LED driver is as follows: Figure 1As shown, the lamp tube includes three segments (LED1, LED2, and LED3). The negative terminal of each segment is connected to a switching transistor. The control signal for the switching transistor is generated by an operational amplifier. When the power supply voltage is detected to be greater than the forward voltage of LED1, the switching transistor corresponding to LED1 turns on, and LED1 lights up. As the power supply voltage increases to be greater than the forward voltage of LED1 and LED2, the switching transistor corresponding to LED2 turns on, and LED1 and LED2 light up. When the power supply voltage is greater than the forward voltage of all three segments, the switching transistor corresponding to LED3 turns on, and all three segments light up.

[0034] The purpose of piecewise linear drive control is to adapt to different input voltages. A piecewise linear driver can control the number of LED segments to light up according to the input voltage level, thus ensuring that some LEDs are lit even at low voltage levels. However, piecewise linear drives suffer from uneven brightness. Specifically, when the input voltage level is low, only some LED segments in the lamp are lit, resulting in uneven brightness and failing to achieve current equalization, thus affecting the lighting effect.

[0035] To solve the above-mentioned technical problems, this utility model provides a segmented LED driving circuit, please refer to... Figure 2 The segmented LED driving circuit includes a DC source 1, a first lamp segment 2, a second lamp segment 4, a diode 3, a first constant current switching circuit 5, a second constant current switching circuit 6, and a third constant current switching circuit 7. The first lamp segment 2 and the second lamp segment 4 are both composed of multiple LED beads connected in series. The positive terminal of the first lamp segment 2 is connected to the positive output of the DC source 1, the negative terminal of the first lamp segment 2 is connected to the positive terminal of the diode 3, and the negative terminal of the diode 3 is connected to the positive terminal of the second lamp segment 4. The first terminal of the first constant current switching circuit 5 is connected to the DC source 1, and the second terminal of the first constant current switching circuit 5 is connected to the negative terminal of the diode 3. The first terminal of the second constant current switching circuit 6 is connected to the negative terminal of the first lamp segment 2, and the second terminal of the second constant current switching circuit 6 is grounded. The first terminal of the third constant current switching circuit 7 is connected to the negative terminal of the second lamp segment 4, and the second terminal of the third constant current switching circuit 7 is grounded.

[0036] In this embodiment, the switching on and off of the first constant current switch circuit 5, the second constant current switch circuit 6, and the third constant current switch circuit 7 are all determined based on the output voltage level of the DC source 1. When the output voltage of the DC source 1 is less than the preset voltage value, the first constant current switch circuit 5, the second constant current switch circuit 6, and the third constant current switch circuit 7 are all turned on, and the currents of the second constant current switch circuit 6 and the third constant current switch circuit 7 are equal. At this time, the positive voltage of the first lamp segment 2 is almost equal to the positive voltage of the second lamp segment 4, both of which are the output voltage of the DC source 1. Therefore, the negative voltage of the diode 3 is greater than the positive voltage of the diode 3, and the diode 3 isolates the first lamp segment 2 and the second lamp segment 4. The first lamp segment 2 and the second lamp segment 4 are connected in parallel. When the output voltage of the DC source 1 is greater than or equal to the preset voltage value, the first constant current switch circuit 5 and the second constant current switch circuit 6 are both turned off, and the third constant current switch circuit 7 is turned on. At this time, the positive terminal of the second lamp segment 4 is disconnected from the DC source 1, the positive voltage of the diode 3 is greater than the negative voltage of the diode 3, the diode 3 is turned on, and the first lamp segment 2 and the second lamp segment 4 are connected in series.

[0037] The aforementioned preset voltage value is determined based on the forward voltage of the first lamp segment 2 and the second lamp segment 4. Specifically, the preset voltage value can be set to be greater than or equal to the sum of the forward voltages of the first lamp segment 2 and the second lamp segment 4. Taking the preset voltage value being equal to the sum of the forward voltages of the first lamp segment 2 and the second lamp segment 4 as an example, when the output voltage of the DC source 1 is greater than or equal to the preset voltage value, that is, when the output voltage of the DC source 1 is greater than or equal to the sum of the forward voltages of the first lamp segment 2 and the second lamp segment 4, the first lamp segment 2 and the second lamp segment 4 are connected in series. When the output voltage of the DC source 1 is less than the preset voltage value, the first lamp segment 2 and the second lamp segment 4 are connected in parallel.

[0038] Based on the diode 3, the first constant current switching circuit 5, the second constant current switching circuit 6, and the third constant current switching circuit 7 described above, the segmented LED driving circuit of this embodiment can realize that the two lamp segments are connected in parallel when the power supply voltage is low and in series when the power supply voltage is high. The two lamp segments can be lit and turned off synchronously, and the lamp segments always maintain current sharing control, so that the brightness of the segmented LEDs is uniform, thereby ensuring the lighting effect.

[0039] This invention does not limit the specific type of DC source 1. For example, DC source 1 can be a battery, a generator, or a power conversion circuit connected to a battery or generator. In some embodiments, DC source 1 is configured as a rectifier. The input terminal of the rectifier is connected to an AC power supply. The positive output terminal of the rectifier is connected to the positive terminal of the first lamp segment 2 and the first terminal of the first constant current switching circuit 5. The negative output terminal of the rectifier is connected to the second terminal of the second constant current switching circuit 6 and the negative terminal of the second lamp segment 4. The negative output terminal of the rectifier is grounded. In some preferred embodiments, a fuse is provided on the input line of the rectifier, and a varistor is connected in parallel to the input of the rectifier for surge protection.

[0040] This invention does not limit the specific structure of each constant current switching circuit; that is, it does not limit the method by which each constant current switching circuit controls the on / off state after detecting the output voltage of DC source 1. For example, a voltage detector can be set in the constant current switching circuit to directly detect the output voltage of DC source 1, thereby controlling the on / off state of the constant current switching circuit; a power detector can also be set in the constant current switching circuit to detect the electrical parameters (voltage or current) of the lamp segment, thereby controlling the on / off state of the constant current switching circuit. It should be understood that the principle and structure of the constant current switching circuit are not limited.

[0041] In some embodiments, the first constant current switching circuit 5 includes a first operational amplifier U1 and a first switching transistor Q1. The first input terminal of the first operational amplifier U1 receives a first preset voltage, and the second input terminal of the first operational amplifier U1 receives a sampling signal characterizing the voltage of the DC source 1. The first terminal of the first switching transistor Q1 is connected to the DC source 1, the second terminal of the first switching transistor Q1 is connected to the cathode of the diode 3, and the control terminal of the first switching transistor Q1 is connected to the output terminal of the first operational amplifier U1. The sampling signal characterizing the voltage of the DC source 1 can be directly obtained by detecting the DC source 1, or indirectly obtained by detecting circuit components, such as using current sampling or voltage sampling.

[0042] In some specific embodiments, the first constant current switching circuit 5 can be configured to be turned off based on the current control of the second lamp segment 4, that is, the sampling signal characterizing the voltage of the DC source 1 is realized based on the current detection of the second lamp segment 4. Specifically, the first constant current switching circuit 5 also includes a current sampling circuit, and the sampling signal characterizing the voltage of the DC source 1 is a current sampling signal obtained through the current sampling circuit. The current sampling circuit includes a current sampling resistor Ri and a differential circuit, please refer to... Figure 3At this time, the first constant current switching circuit 5 includes a first operational amplifier U1, a first switching transistor Q1, and a current sampling resistor Ri. The first end of the current sampling resistor Ri is connected to the negative terminal of the diode 3, and the second end of the current sampling resistor Ri is connected to the positive terminal of the second lamp segment 4. The first end of the first switching transistor Q1 is connected to the DC source 1, and the second end of the first switching transistor Q1 is connected to the first end of the current sampling resistor Ri. The two ends of the current sampling resistor Ri are connected to the second input terminal of the first operational amplifier U1 through a differential circuit.

[0043] Based on the above circuit structure, the voltage at the second input terminal of the first operational amplifier U1 is equal to the voltage of the current sampling resistor Ri. When the voltage of the current sampling resistor Ri is less than the first preset voltage, the first operational amplifier U1 outputs a turn-on control signal to turn on the first switching transistor Q1, that is, the first constant current switching circuit 5 turns on. When the third constant current switching circuit 7 also turns on, the output voltage of the DC source 1 is greater than the positive voltage of the second lamp segment 4. The DC source 1, the first switching transistor Q1, the current sampling resistor Ri, the second lamp segment 4, and the third constant current switching circuit 7 form a circuit, and the second lamp segment 4 lights up. At this time, the current of the first constant current switching circuit 5 is the same as the current of the third constant current switching circuit 7. As the output voltage of the DC source 1 increases, the voltage value of the current sampling resistor Ri also increases accordingly until the voltage of the current sampling resistor Ri is greater than or equal to the first preset voltage. The first operational amplifier U1 outputs a turn-off control signal to turn off the first switching transistor Q1, and the second lamp segment 4 is disconnected from the DC source 1.

[0044] In the above embodiment, the first preset voltage corresponds to the current after the first constant current switching circuit 5 is turned on. Specifically, the first preset voltage is Vref1, then the current I1 after the first constant current switching circuit 5 is turned on is Vref1 / Ri. Since the current value flowing through the current sampling resistor Ri is related to the preset voltage value, when the output voltage of the DC source 1 is less than the preset voltage value, the current of the first constant current switching circuit 5 remains unchanged at I1. When the output voltage of the DC source 1 is greater than or equal to the preset voltage value, the first constant current switching circuit 5 is turned off.

[0045] In some specific embodiments, the first preset voltage can be generated by a reference generation circuit; specifically, please refer to... Figure 3 The first constant current switching circuit 5 also includes a reference generation circuit. The input terminal of the reference generation circuit is connected to the DC source 1, and the output terminal of the reference generation circuit is connected to the first input terminal of the first operational amplifier U1. The reference generation circuit is used to sample the output voltage of the current source and generate the aforementioned first preset voltage.

[0046] In some specific embodiments, the first constant current switching circuit 5 can also be configured to be voltage-controlled off, that is, the sampling signal characterizing the voltage of the DC source 1 is implemented based on voltage detection. Specifically, the first constant current switching circuit 5 further includes a voltage detection circuit, and the sampling signal characterizing the voltage of the DC source 1 is a voltage sampling signal obtained through the voltage detection circuit. The voltage detection circuit includes a first voltage divider resistor R1, a second voltage divider resistor R2, and a voltage sampling resistor Rv. Please refer to [reference needed]. Figure 4 At this time, the first constant current switching circuit 5 includes a first operational amplifier U1, a first switching transistor Q1, a first voltage divider resistor R1, a second voltage divider resistor R2, and a voltage sampling resistor Rv. The first end of the first voltage divider resistor R1 is connected to the DC source 1. The second end of the second voltage divider resistor R2 is connected to the first end of the second voltage divider resistor R2. The second end of the second voltage divider resistor R2 is connected to the positive terminal of the second lamp segment 4. The first end of the voltage sampling resistor Rv is connected to the first end of the second voltage divider resistor R2. The second end of the voltage sampling resistor Rv is connected to the second input terminal of the first operational amplifier U1.

[0047] Based on the above circuit structure, the voltage detection circuit adopts a voltage divider circuit design. The voltage detection circuit can detect the voltage across the first switching transistor Q1 and feed it back to the first operational amplifier U1. When the feedback voltage of the voltage detection circuit is less than the first preset voltage, the first operational amplifier U1 outputs a turn-on control signal to turn on the first switching transistor Q1, that is, the first constant current switching circuit 5 turns on. When the third constant current switching circuit 7 also turns on, the output voltage of the DC source 1 is greater than the positive voltage of the second lamp segment 4. The DC source 1, the first switching transistor Q1, the current sampling resistor Ri, the second lamp segment 4, and the third constant current switching circuit 7 form a circuit, and the second lamp segment 4 lights up. At this time, the current of the first constant current switching circuit 5 is the same as the current of the third constant current switching circuit 7. As the output voltage of the DC source 1 increases, the voltage across the first switching transistor Q1 also increases accordingly, and the feedback voltage of the voltage detection circuit also increases accordingly, until the feedback voltage of the voltage detection circuit is greater than or equal to the first preset voltage. The first operational amplifier U1 outputs a turn-off control signal to turn off the first switching transistor Q1, and the second lamp segment 4 is disconnected from the DC source 1.

[0048] The above embodiments respectively introduce the schemes of the first constant current switching circuit 5 based on current feedback turn-off and voltage feedback turn-off. In practical applications, the first constant current switching circuit 5 can be implemented based on an LED driver chip. Specifically, in some embodiments, the segmented LED driving circuit includes a single-segment linear LED driver, which integrates the above-mentioned first constant current switching circuit 5. That is, the single-segment linear LED driver has the function of current feedback / voltage feedback and the function of current sharing control. By driving a single LED segment through the single-segment linear LED driver, the current of the LED segment can be kept stable. This embodiment does not limit the specific model of the single-segment linear LED driver.

[0049] In some embodiments, please refer to Figure 5 The second constant current switching circuit 6 includes a second operational amplifier U2 and a second switching transistor Q2. The first terminal of the second switching transistor Q2 is connected to the negative terminal of the first lamp segment 2. The second terminal of the second switching transistor Q2 is connected to the first terminal of the feedback resistor Rf. The second terminal of the feedback resistor Rf is grounded. The control terminal of the second switching transistor Q2 is connected to the output terminal of the second operational amplifier U2. The first input terminal of the second operational amplifier U2 receives a second preset voltage. The second input terminal of the second operational amplifier U2 is connected to the first terminal of the feedback resistor Rf.

[0050] Based on the above circuit structure, the second operational amplifier U2 compares the voltage of the feedback resistor Rf with the second preset voltage. When the voltage of the feedback resistor Rf is less than the second preset voltage, the second operational amplifier U2 outputs a turn-on control signal to turn on the second switch Q2. At this time, the DC source 1, the first lamp segment 2, and the second switch Q2 form a circuit. When the output voltage of the DC source 1 is greater than the positive voltage of the first lamp segment 2, the first lamp segment 2 lights up. As the output voltage of the DC source 1 increases to be greater than or equal to the preset voltage value, the voltage of the feedback resistor Rf is greater than or equal to the second preset voltage. The second operational amplifier U2 outputs a turn-off control signal to turn off the second switch Q2. At this time, the first constant current switch circuit 5 is simultaneously turned off, and the first lamp segment 2 and the second lamp segment 4 are connected in series and lit up synchronously.

[0051] In a further embodiment, please refer to Figure 5 Similar to the structure of the second constant current switching circuit 6, the third constant current switching circuit 7 includes a third operational amplifier U3 and a third switching transistor Q3. The first terminal of the third switching transistor Q3 is connected to the negative terminal of the second lamp segment 4, the second terminal of the third switching transistor Q3 is connected to the first terminal of the feedback resistor Rf, the control terminal of the third switching transistor Q3 is connected to the output terminal of the third operational amplifier U3, the first input terminal of the third operational amplifier U3 receives a third preset voltage, and the second input terminal of the third operational amplifier U3 is connected to the first terminal of the feedback resistor Rf. The third constant current switching circuit 7 and the second constant current switching circuit 6 share the same feedback resistor Rf, and the second constant current switching circuit 6 and the third constant current switching circuit 7 form a piecewise linear LED driving circuit.

[0052] Based on the above circuit structure, when the DC source 1 voltage is relatively small, the voltage at the second input terminal of the second operational amplifier U2 is less than the second preset voltage, the voltage at the second input terminal of the third operational amplifier U3 is less than the third preset voltage, and both the second switch Q2 and the third switch Q3 are turned on; while when the DC source 1 voltage is relatively large, the voltage at the second input terminal of the second operational amplifier U2 is greater than or equal to the second preset voltage, the second switch Q2 is turned off, and the voltage at the first input terminal of the third operational amplifier U3 is less than the third preset voltage, and the third switch Q3 is turned on.

[0053] In practical applications, the second constant current switching circuit 6 and the third constant current switching circuit 7 can be implemented based on an LED driver chip. Specifically, in some embodiments, the segmented LED driving circuit includes a segmented linear LED driver, which integrates the aforementioned second constant current switching circuit 6 and the aforementioned third constant current switching circuit 7. The segmented linear LED driver has the function of selectively turning on one or more switches based on the output voltage of the DC source 1, and it also has the function of current sharing control, enabling the current of each LED segment to be stable. This embodiment does not limit the specific model of the segmented linear LED driver.

[0054] This utility model embodiment also provides a lighting system, which includes the segmented LED driving circuit described in any of the above embodiments.

[0055] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A segmented LED driving circuit, characterized in that, It includes a DC source, a first lamp segment, a second lamp segment, a diode, a first constant current switching circuit, a second constant current switching circuit, and a third constant current switching circuit. The first lamp segment and the second lamp segment are both composed of LED beads connected in series. The positive terminal of the first lamp segment is connected to the DC source, the negative terminal of the first lamp segment is connected to the positive terminal of the diode, and the negative terminal of the diode is connected to the positive terminal of the second lamp segment; The first terminal of the first constant current switching circuit is connected to the DC source, the second terminal of the first constant current switching circuit is connected to the negative terminal of the diode, the first terminal of the second constant current switching circuit is connected to the negative terminal of the first lamp segment, the second terminal of the second constant current switching circuit is grounded, the first terminal of the third constant current switching circuit is connected to the negative terminal of the second lamp segment, and the second terminal of the third constant current switching circuit is grounded. When the DC source voltage is less than the preset voltage value, the first constant current switch circuit, the second constant current switch circuit, and the third constant current switch circuit are all turned on. When the DC source voltage is greater than or equal to the preset voltage value, both the first constant current switch circuit and the second constant current switch circuit are disconnected, and the third constant current switch circuit is turned on.

2. The segmented LED driving circuit according to claim 1, characterized in that, The first constant current switching circuit includes a first operational amplifier and a first switching transistor. The first input terminal of the first operational amplifier receives a first preset voltage, and the second input terminal of the first operational amplifier receives a sampling signal characterizing the DC source voltage. The first terminal of the first switching transistor is connected to the DC source, the second terminal of the first switching transistor is connected to the negative terminal of the diode, and the control terminal of the first switching transistor is connected to the output terminal of the first operational amplifier.

3. The segmented LED driving circuit according to claim 2, characterized in that, The first constant current switching circuit further includes a current sampling circuit, wherein the sampling signal characterizing the DC source voltage is a current sampling signal obtained through the current sampling circuit; wherein the current sampling circuit includes a current sampling resistor and a differential circuit, the first end of the current sampling resistor is connected to the negative terminal of the diode, and the second end of the current sampling resistor is connected to the positive terminal of the second lamp segment; the two ends of the current sampling resistor are connected to the second input terminal of the first operational amplifier through the differential circuit.

4. The segmented LED driving circuit according to claim 2, characterized in that, The first constant current switching circuit further includes a voltage detection circuit, wherein the sampling signal characterizing the DC source voltage is a voltage sampling signal obtained through the voltage detection circuit; wherein the voltage detection circuit includes a first voltage divider resistor, a second voltage divider resistor, and a voltage sampling resistor, the first end of the first voltage divider resistor is connected to the DC source, the second end of the first voltage divider resistor is connected to the first end of the second voltage divider resistor, the second end of the second voltage divider resistor is connected to the positive terminal of the second lamp segment, the first end of the voltage sampling resistor is connected to the first end of the second voltage divider resistor, and the second end of the voltage sampling resistor is connected to the second input terminal of the first operational amplifier.

5. The segmented LED driving circuit according to claim 2, characterized in that, The first constant current switching circuit further includes a reference generation circuit. The input terminal of the reference generation circuit is connected to the DC source, and the output terminal of the reference generation circuit is connected to the first input terminal of the first operational amplifier. The reference generation circuit is used to generate the first preset voltage.

6. The segmented LED driving circuit according to any one of claims 1-5, characterized in that, The segmented LED driving circuit includes a single-segment linear LED driver, in which the first constant current switching circuit is integrated.

7. The segmented LED driving circuit according to claim 1, characterized in that, The second constant current switching circuit includes a second operational amplifier and a second switching transistor. The first terminal of the second switching transistor is connected to the negative terminal of the first lamp segment. The second terminal of the second switching transistor is connected to the first terminal of a feedback resistor. The second terminal of the feedback resistor is grounded. The control terminal of the second switching transistor is connected to the output terminal of the second operational amplifier. The first input terminal of the second operational amplifier receives a second preset voltage. The second input terminal of the second operational amplifier is connected to the first terminal of the feedback resistor.

8. The segmented LED driving circuit according to claim 7, characterized in that, The third constant current switching circuit includes a third operational amplifier and a third switching transistor. The first terminal of the third switching transistor is connected to the negative terminal of the second lamp segment, the second terminal of the third switching transistor is connected to the first terminal of the feedback resistor, the control terminal of the third switching transistor is connected to the output terminal of the third operational amplifier, the first input terminal of the third operational amplifier receives a third preset voltage, and the second input terminal of the third operational amplifier is connected to the first terminal of the feedback resistor.

9. The segmented LED driving circuit according to claim 8, characterized in that, The segmented LED driving circuit includes a segmented linear LED driver, which integrates the second constant current switching circuit and the third constant current switching circuit.

10. A lighting system, characterized in that, The segmented LED driving circuit includes any one of claims 1-9.

Images