LED string, string combination, and system

Abstract

Disclosed are an LED string, a string combination, and a system. The LED string comprises a power processor and a plurality of LED beads sequentially connected in series. The power processor comprises a reference voltage circuit, a sensing resistor, a voltage comparator, and a field-effect transistor. The power processor is configured to: receive a loop current of the LED string, control the voltage comparator to acquire a sensing voltage on the basis of a resistance value of the sensing resistor and the loop current; and control the voltage comparator to generate an adjustment voltage signal on the basis of a magnitude relationship between a reference voltage provided by the reference voltage circuit and the sensing voltage. When the sensing voltage is less than the reference voltage, the adjustment voltage signal is to raise the loop current, the field-effect transistor is controlled to be in an on state, and the loop current increases; and when the sensing voltage is greater than the reference voltage, the adjustment voltage signal is to lower the loop current, the field-effect transistor is controlled to be in an off state, and the loop current is reduced. In the LED string provided by the present application, the stability of the loop current can be maintained and the conversion efficiency of a power supply can be improved.

Description

An LED light string, light string combination and system Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to an LED light string, a light string combination, and a system. Background Technology

[0002] The mainstream products in the Christmas light market are high-voltage 220V LED light strings. The common specification is 50 LED beads connected in series to form a circuit, and then several circuits are connected in parallel to form finished light strings of different lengths.

[0003] In a typical LED string, each LED has only one LED chip. To meet the power supply voltage requirements of the LED string, resistors are mainly used to distribute the voltage across the LED string. The higher the power supply voltage, the more LEDs need to be connected in series. To reduce the number of LEDs connected in series, the resistance value or the number of resistors needs to be increased to meet the power supply voltage requirements.

[0004] However, LED strings with resistors connected in series will cause power loss when the LED string is working, resulting in current flowing through the resistors and reducing the power conversion efficiency. The resistors will also cause fluctuations in the loop current of the LED string, thus affecting the stability of the LED string's light emission.

[0005] Therefore, how to design an LED light string to achieve intelligent regulation of the loop current and thus ensure the current stability of the LED light string has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides an LED light string, a light string combination, and a system to solve the technical problem of how to design an LED light string to achieve intelligent regulation of the circuit current, thereby ensuring the current stability of the LED light string, so as to improve the power conversion efficiency of the LED light string and enhance the stability of the LED light string's luminous brightness.

[0007] In a first aspect, in order to solve the above-mentioned technical problems, the present invention provides an LED light string, including a power processor and a light-emitting unit, wherein the light-emitting unit includes a plurality of LED beads connected in series.

[0008] The power processor includes a reference voltage circuit, a sensing resistor, a voltage comparator, and a field-effect transistor. The output terminal of the light-emitting unit is connected to the input terminal of the reference voltage circuit and the first input terminal of the field-effect transistor, respectively. The output terminal of the reference voltage circuit is connected to the first input terminal of the voltage comparator. The input terminal of the sensing resistor is connected to the second input terminal of the voltage comparator and the output terminal of the field-effect transistor, respectively. The output terminal of the voltage comparator is connected to the second input terminal of the field-effect transistor. The output terminal of the sensing resistor is the common terminal of the power processor.

[0009] The power processor is configured to:

[0010] The loop current of the LED string is received, and the voltage comparator is controlled to obtain the detection voltage based on the resistance value of the detection resistor and the loop current.

[0011] The voltage comparator is controlled to generate an adjustment voltage signal based on the relationship between the reference voltage provided by the reference voltage circuit and the detection voltage, and the adjustment voltage signal is sent to the field-effect transistor; the adjustment voltage signal is set to increase the loop current when the detection voltage is less than the reference voltage, and to decrease the loop current when the detection voltage is greater than the reference voltage;

[0012] When the adjustment voltage signal is to increase the loop current, the field-effect transistor is controlled to be in the on state to increase the loop current; when the adjustment voltage signal is to decrease the loop current, the field-effect transistor is controlled to be in the off state to decrease the loop current.

[0013] Preferably, the reference voltage is greater than or equal to 0.5% of the external input voltage of the LED string.

[0014] Preferably, each of the LED beads comprises two or more LED chips connected in series.

[0015] Preferably, controlling the voltage comparator to obtain the detection voltage based on the resistance value of the detection resistor and the loop current includes:

[0016] The detection voltage is obtained using the following formula: V J =I×R J

[0017] Among them, V J Represents the detected voltage, I represents the loop current, and R... J This indicates the resistance value of the sensing resistor.

[0018] Preferably, the formula for calculating the resistance value of the detection resistor is:

[0019] Where V represents the external input voltage of the LED string, R d This represents the equivalent resistance of the light-emitting unit.

[0020] Preferably, the reference voltage circuit includes a one-time programmable memory and a bandgap reference source.

[0021] Preferably, the power processor is encapsulated within one of the LED beads in the light-emitting unit circuit.

[0022] Preferably, the LED string also includes a pair of male and female connectors;

[0023] The male and female connectors are located at the two ends of the LED string, respectively, to connect the LED string in series into a circuit.

[0024] Secondly, this application also provides an LED light string assembly, comprising a plurality of LED light strings as described above.

[0025] Thirdly, this application also provides an LED system including a rectifier and an LED string assembly as described above connected to the rectifier.

[0026] The LED light strings, light string combinations, and systems disclosed in this invention have advantages over the prior art, including at least one of the following:

[0027] (1) Maintain the stability of the LED string circuit current, thereby ensuring the stability of the LED string brightness;

[0028] (2) When the external input voltage is higher than the total rated voltage of the light-emitting unit, the internal circuit of the power processor processes the higher voltage. When the external input voltage is lower than the total rated voltage of the light-emitting unit, the internal circuit of the power processor releases sufficient voltage, thereby improving the power conversion efficiency. Attached Figure Description

[0029] Figure 1 is a schematic diagram of an LED light string provided in one embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of an LED string in one embodiment of the present invention, in which a power processor is encapsulated in one of the LED beads of the light-emitting unit circuit.

[0031] Figure 3 is a schematic diagram of an LED string connected by male and female connectors according to one embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of the LED string combination provided in one embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] An embodiment of the present invention provides an LED light string, including a power processor and a light-emitting unit, wherein the light-emitting unit includes a plurality of LED beads connected in series.

[0038] The power processor includes a reference voltage circuit, a sensing resistor, a voltage comparator, and a field-effect transistor. The output terminal of the light-emitting unit is connected to the input terminal of the reference voltage circuit and the first input terminal of the field-effect transistor, respectively. The output terminal of the reference voltage circuit is connected to the first input terminal of the voltage comparator. The input terminal of the sensing resistor is connected to the second input terminal of the voltage comparator and the output terminal of the field-effect transistor, respectively. The output terminal of the voltage comparator is connected to the second input terminal of the field-effect transistor. The output terminal of the sensing resistor is the common terminal of the power processor.

[0039] The power processor is configured to:

[0040] The loop current of the LED string is received, and the voltage comparator is controlled to obtain the detection voltage based on the resistance value of the detection resistor and the loop current.

[0041] The voltage comparator is controlled to generate an adjustment voltage signal based on the relationship between the reference voltage provided by the reference voltage circuit and the detection voltage, and the adjustment voltage signal is sent to the field-effect transistor; the adjustment voltage signal is set to increase the loop current when the detection voltage is less than the reference voltage, and to decrease the loop current when the detection voltage is greater than the reference voltage;

[0042] When the adjustment voltage signal is to increase the loop current, the field-effect transistor is controlled to be in the on state to increase the loop current; when the adjustment voltage signal is to decrease the loop current, the field-effect transistor is controlled to be in the off state to decrease the loop current.

[0043] LED beads typically use LED chips to emit light. The current, voltage, and power of LED chips have a non-linear relationship. Connecting multiple LED chips in series to form an LED bead can increase the total rated voltage of the LED bead and reduce the current of the LED bead, thereby reducing the power of the LED bead while maintaining the brightness.

[0044] In view of this, in the preferred embodiment of this application, two or more LED chips are connected in series in each LED bead of the light-emitting unit. Under the premise of ensuring that the brightness of a single LED bead remains unchanged, the total voltage of the light-emitting unit is increased and the current flowing through the light-emitting unit is reduced.

[0045] To ensure the stability of the loop current of the LED string, a power processor dynamically adjusts the loop current based on changes in the loop current, as shown in Figure 1. The power processor includes a reference voltage circuit, a sensing resistor, a voltage comparator, and a field-effect transistor. The output terminal of the light-emitting unit is connected to the input terminal of the reference voltage circuit and the first input terminal of the field-effect transistor, respectively. The reference voltage circuit provides a reference voltage, which, in this application, should be greater than or equal to 0.5% of the external input voltage of the LED string. The reference voltage circuit includes a one-time programmable memory and a bandgap reference source. A one-time programmable memory is a memory that can only be programmed once; once data is written, it cannot be erased or reprogrammed. One-time programmable memory exhibits excellent stability and can maintain data integrity under various environmental conditions. Due to its one-time programming characteristic, it has significant advantages in security. Compared to rewritable memory, the manufacturing cost of one-time programmable memory is relatively low because it does not require additional erasure operations. Even when power is off, the stored data in one-time programmable memory will not be lost. A bandgap reference source is a circuit structure used to provide a stable reference voltage. It utilizes the properties of semiconductor materials and achieves a stable reference voltage output by designing a suitable circuit structure. Based on the reference voltage value stored in a one-time programmable memory, the bandgap reference source generates a reference voltage of a corresponding magnitude.

[0046] As shown in Figure 1, the output of the reference voltage circuit is connected to the first input of the voltage comparator (i.e., the positive input of the voltage comparator in the figure). The input of the sensing resistor is connected to the second input of the voltage comparator (i.e., the negative input of the voltage comparator in the figure) and the output of the field-effect transistor (FET). The output of the voltage comparator is connected to the second input of the FET. The output of the sensing resistor is the common terminal of the power processor. The FETs selected in this application are mainly of two types: junction field-effect transistors (JFETs) and metal-oxide-semiconductor field-effect transistors (MOS-FETs). MOS-FETs, also known as metal-oxide-semiconductor field-effect transistors, generally have depletion-mode and enhancement-mode types. Enhancement-mode MOS-effect transistors can be further divided into NPN and PNP types. Field-effect transistors (FETs) control the current between the source and drain by changing the gate voltage. In enhancement-mode FETs, the gate voltage must reach a certain threshold for current to flow; while in depletion-mode FETs, current can flow even when the gate voltage is zero. Changes in the gate voltage are used to regulate the magnitude of the current. In this embodiment, an enhancement-mode FET is selected. Optionally, as shown in Figure 1, an N-type enhancement-mode FET is selected, with the first input terminal being the drain, the second input terminal being the gate, and the output terminal being the source.

[0047] The gate of the field-effect transistor (FET) in this application is connected to the output terminal of the voltage comparator to receive the voltage output by the voltage comparator, thereby controlling the FET to turn on or off. Specifically, as shown in Figure 1, the input terminal of the sensing resistor is connected to the second input terminal of the voltage comparator and the output terminal of the FET, respectively. Based on the desired brightness of a single LED bead, the rated voltage for the LED string is determined. The power processor receives the loop current of the LED string to provide power. The reference voltage circuit outputs a reference voltage and inputs it to the first input terminal of the voltage comparator. At this time, the FET is in the off state, and the second input terminal of the voltage comparator is 0. Therefore, the reference voltage at the first input terminal of the voltage comparator is greater than the sensing voltage at the second input terminal. The voltage comparator outputs an adjustment voltage signal, which increases the loop current. At this time, the FET is in the on state under the action of the adjustment voltage signal, so that the loop current flows through the sensing resistor, increasing the loop current. Because the input terminal of the sensing resistor is connected to the second input terminal of the voltage comparator, the voltage comparator can acquire the sensing voltage across the sensing resistor. The formula for calculating the sensing voltage is: V J =I×R J

[0048] In the formula, V J Represents the detected voltage, I represents the loop current, and R... J This indicates the resistance value of the sensing resistor.

[0049] The resistance value of the sensing resistor is determined according to the following formula:

[0050] In the formula, V represents the external input voltage of the LED string, and R... d This represents the equivalent resistance of the light-emitting unit.

[0051] The voltage comparator compares the reference voltage and the detected voltage. When the detected voltage is less than the reference voltage, it indicates that the loop current is less than the rated current, requiring an increase in the loop current. Conversely, when the detected voltage is greater than the reference voltage, it indicates that the loop current is greater than the rated current, requiring a decrease in the loop current. The field-effect transistor (FET) is in a conducting state when the voltage signal is adjusted to increase the loop current, and in a destructive state when the voltage signal is adjusted to decrease the loop current, thus reducing the loop current. This dynamic cyclical state of the sensing resistor, voltage comparator, and FET keeps the loop current of the LED string constant, ensuring stable brightness. Because the FET is off for less than the time perceptible to the human eye, the flickering of the LED beads is imperceptible and does not affect their brightness.

[0052] The external input voltage for the LED light string must be DC. In practical applications, a rectifier is needed to convert the effective AC voltage of 220V to DC voltage. This application compares the LED light string provided in this application with a commonly used 50-LED-bead string. Table 1 shows the reference comparison data between the traditional LED light string and the LED light string of this application.

[0053] Table 1

[0054] Traditionally, LED beads have a voltage rating of 2.5V to 3.5V and an operating range of 1mA to 25mA. When 50 LED beads are connected in series in a circuit with 10 680-ohm resistors, the measured circuit current is 12 mA. The total voltage across the 50 LEDs is 133V, and the voltage across the resistors is 65V. The brightness of a single LED is 15260 LUX. Calculating the total power of the LED string, the power of each LED bead is 133 * 0.012 = 1.596W, and the power of the resistors is 65 * 0.12 = 0.78W. The total power of the LED string is 1.596W + 0.78W = 2.376W. The power conversion efficiency is 0.9 (198V / 220V).

[0055] Using the LED string disclosed in this invention, two LED chips are packaged in the same LED bead. The specifications of a single LED are 5V~7V / 1mA~25mA. 50 LED beads are connected in series in one circuit. Under the action of the power processor, the required circuit current of the LED string is determined according to the brightness of a single LED. When the brightness of a single LED bead is 15320LUX, the required circuit current of the LED string is 7mA. When a stable state is reached, the total voltage of the 50 LED beads in the tested circuit is 208V, and the voltage of the power processor is 1V. Calculate the total power of the LED string. The power of the LED beads is 208 * 0.007 = 1.456W, and the power consumed by the power processor is 1 * 0.007 = 0.007W. The total power of the LED string is 1.456 + 0.007 = 1.463W. At the same brightness, compared to the traditional method of using resistors for voltage reduction, the power saving is approximately 38%. The calculation formula is: (2.376 - 1.463) / 2.376. Furthermore, the power supply conversion efficiency is 209V / 220V, reaching 0.95.

[0056] In a traditional LED string light, when an 8K ohm resistor is connected in the circuit, the measured circuit current is 9 mA, the total voltage of 50 LEDs in the circuit is 131V, the voltage across the resistor is 67V, and the brightness of a single LED is 12270 LUX. Calculate the total power of the LED string: the power of the LED is 131 * 0.009 = 1.179W, the power of the resistor is 67 * 0.009 = 0.603W, and the total power of the LED string is 1.179W + 0.603W = 1.782W. The power conversion efficiency is 198V / 220V, which is 0.9.

[0057] When the brightness of a single LED bead is 14500 LUX, the required loop current for the LED string is 6 mA. At a steady state, the measured total voltage of the 50 LED beads in the loop is 207V, and the power processor voltage is 2V. Calculating the total power of the LED string, the power of the LED beads is 207 * 0.006 = 1.242W, the power consumed by the power processor is 2 * 0.006 = 0.012W, and the total power of the LED string is 1.242 + 0.012 = 1.254W. At the same brightness, compared to the traditional resistor-based voltage reduction, the power saving is approximately 29.6%, calculated as (1.782 - 1.254) / 1.782. Furthermore, the power conversion efficiency is 209V / 220V, reaching 0.95, and the brightness of a single LED string in this application is 2230 LUX higher than that of a traditional single LED string.

[0058] In a traditional LED string light, when a 20K ohm resistor is connected in the circuit, the measured circuit current is 4.5 mA. The total voltage of the 50 LEDs in the circuit is 126V, the voltage across the resistor is 72V, and the brightness of a single LED is 6220 LUX. Calculate the total power of the LED string. The power of each LED is 126 * 0.0045 = 0.567W, the power of the resistor is 72 * 0.0045 = 0.324W, and the total power of the LED string is 0.567W + 0.324W = 0.891W. The power conversion efficiency is 198V / 220V, which is 0.9.

[0059] The LED string provided in this application has a loop current of 4.5 mA. At this point, the brightness of a single LED is 10560 LUX. When the circuit reaches a steady state, the total voltage of the 50 LEDs in the loop is measured to be 205 V, and the power processor voltage is 4 V. The total power of the LED string is calculated as follows: the power of the LED beads is 205 * 0.0045 = 0.9225 W, the power consumed by the power processor is 4 * 0.0045 = 0.018 W, and the total power of the LED string is 0.9225 + 0.018 = 0.9405 W. While maintaining a similar power to traditional LED strings, this application increases the brightness of a single LED bead by 4340 LUX. Furthermore, the power conversion efficiency is 209 V / 220 V, reaching 0.95.

[0060] As can be seen from the above comparative data, although the current in the LED string circuit of the present invention is reduced, the brightness of a single LED is not affected because each LED has two LED chips that emit light simultaneously. At the same time, the power consumed by the LED string is reduced, the power conversion efficiency is improved, and the current of the LED string is kept constant, thus ensuring the stability of the brightness of the LED beads.

[0061] In this application, a traditional LED string with 40 LED beads is used as an example for comparison with the LED string provided in this application. When the loop current of the LED string is 9 mA, the brightness of a single LED bead is approximately 12270 LUX, the average voltage of 40 LEDs is 105 volts, and the power is 0.945 W. In addition, the voltage consumed through the series resistor is 93 volts, with a power loss of 0.837 W. Therefore, the total power of a conventional LED string is 0.945 + 0.837 = 1.782 W.

[0062] When using the LED string of this application, each LED bead encapsulates two LED chips, and the total voltage of the LED string circuit reaches 209V. To achieve a brightness of 12270 LUX per LED bead, the required circuit current is 6 mA. The total voltage of the 40 energy-saving LED beads is 165V, and the voltage across the power processor is 44V. When the voltage across the power processor is greater than 44V, the power processor shares the excess voltage; when the voltage across the power processor is less than 44V, the power processor releases sufficient voltage. In this way, the circuit current of the LED string is maintained at 6 mA, and the total voltage of the 44 LED beads in the circuit is maintained at 165V, achieving a power conversion efficiency of over 0.95. Although the circuit current of the LED string is 6 mA, because it contains two LED chips emitting light simultaneously, the actual luminous brightness of a single LED bead reaches 14500 LUX, exceeding the luminous brightness of a typical LED circuit with a circuit current of 9 mA. The power of 40 LED beads is 165 * 0.006 = 0.99W, the power processor consumes 44V * 0.006 = 0.264W, and the total power of the LED string is 1.254W. Compared with the traditional resistor element voltage reduction, it saves more than 30% of the power.

[0063] In this application, a traditional LED string with 32 LED beads is used as an example for comparison with the LED string provided in this application. When the loop current of the LED string is 4.5 mA, the brightness of a single LED bead is approximately 6220 LUX, the average voltage of the 32 LEDs is 101 volts, and the power is 0.4545 W. In addition, the voltage consumed through the series resistor is 97 volts, with a power loss of 0.4365 W. Therefore, the total power of a conventional LED string is 0.4545 + 0.4365 = 0.891 W.

[0064] When using the LED string of this application, each LED bead encapsulates two LED chips, and the total voltage of the LED string circuit reaches 209V. When the circuit current of the LED string is 4.5 mA, the total voltage of the 32 energy-saving LED beads is 131V, and the voltage across the power processor is 78V. When the voltage across the power processor is greater than 78V, the power processor shares the excess voltage; when the voltage across the power processor is less than 78V, the power processor releases sufficient voltage. In this way, the circuit current of the LED string is maintained at 4.5 mA, and the total voltage of the 44 LED beads in the circuit is maintained at 131V, with a power conversion efficiency of over 0.95. Although the circuit current of the LED string is 4.5 mA, because it has two LED chips emitting light simultaneously, the actual luminous intensity of a single LED bead reaches 10560 LUX, exceeding the luminous intensity of 4340 LUX for a common light-emitting diode with a circuit current of 4.5 mA. The power of 32 LED beads is 131 * 0.0045 = 0.5859W, the power processor consumes 78V * 0.0045 = 0.351W, and the total power of the LED string is 0.9405W. Compared with traditional resistor voltage reduction, with the same loop current, the power consumption only increases by 5.5%, but the luminous brightness is increased by about 70% compared with traditional LED beads.

[0065] As shown in Figure 2, in a preferred embodiment of this application, the power processor can also be packaged in one of the LED beads in the light-emitting unit circuit, such as LED bead B shown in Figure 2. During production, it can be made into a through-hole type or a surface-mount type to adapt to the automated production of LED light strings.

[0066] As shown in Figure 3, in a preferred embodiment of this application, the LED string also includes two male and female connectors. These connectors are electrical connection devices, consisting of a male and a female part. Electrical connection is achieved through insertion and removal. The male and female connectors are located at opposite ends of the LED string, connecting the LEDs in series to form a circuit. Therefore, in this application, the LED string has two ways of connecting to an external power source: one is direct connection, and the other is connection via the male and female connectors.

[0067] Based on LED light strings, this invention also discloses an LED light string combination, comprising a number of LED light strings disclosed in the embodiments of this application. Several LED light strings can also be connected in series via male and female connectors, as shown in Figure 4.

[0068] Based on LED string combinations, an LED system is also disclosed in this embodiment of the invention, including a rectifier and the LED string combination disclosed in this application connected to the rectifier.

[0069] The rectifier receives external AC voltage and converts it into DC voltage suitable for LED strings. The rectifier can be directly connected to the LED strings, or male and female connectors can be installed on the rectifier to connect several LED strings in series.

[0070] The output of the rectifier is connected to the input of each LED string, and the output of each LED string is connected to the input of the rectifier to extend the length of the LED string.

[0071] In this embodiment of the invention, to address the technical problem of how to design an LED string to achieve intelligent regulation of the loop current and thus ensure the current stability of the LED string, an LED string, a string combination, and a system are disclosed. The LED string includes a power processor and light-emitting units. Each light-emitting unit includes several LED beads connected in series. The power processor includes a reference voltage circuit, a detection resistor, a voltage comparator, and a field-effect transistor. The output terminal of the light-emitting unit is connected to the input terminal of the reference voltage circuit and the first input terminal of the field-effect transistor, respectively. The output terminal of the reference voltage circuit is connected to the first input terminal of the voltage comparator. The input terminal of the detection resistor is connected to the second input terminal of the voltage comparator and the output terminal of the field-effect transistor, respectively. The output terminal of the voltage comparator is connected to the second input terminal of the field-effect transistor. The output terminal of the detection resistor is the common terminal of the power processor. The power processor is configured to: receive L... The loop current of the LED string is controlled by a voltage comparator that obtains a detection voltage based on the resistance value of the detection resistor and the loop current. The voltage comparator generates an adjustment voltage signal based on the relationship between the reference voltage provided by the reference voltage circuit and the detection voltage, and sends the adjustment voltage signal to the field-effect transistor. The adjustment voltage signal is set to increase the loop current when the detection voltage is less than the reference voltage and decrease the loop current when the detection voltage is greater than the reference voltage. When the adjustment voltage signal increases the loop current, the field-effect transistor is turned on to increase the loop current; when the adjustment voltage signal decreases the loop current, the field-effect transistor is turned off to reduce the loop current. The LED string provided in this application can maintain the stability of the LED string loop current, thereby ensuring the stability of the LED string's luminous brightness. When the external input voltage is higher than the total rated voltage of the light-emitting unit, the internal circuit of the power processor processes the excess voltage; when the external input voltage is lower than the total rated voltage of the light-emitting unit, the internal circuit of the power processor releases sufficient voltage, thereby improving the power conversion efficiency.

[0072] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An LED light string, characterized in that, The LED lamp string comprises a power processor and a light emitting unit, wherein the light emitting unit comprises a plurality of LED lamp beads connected in series. The power processor comprises a reference voltage circuit, a detection resistor, a voltage comparator and a field effect transistor; the output ends of the light emitting unit are connected with the input end of the reference voltage circuit and the first input end of the field effect transistor respectively; the output end of the reference voltage circuit is connected with the first input end of the voltage comparator; the input ends of the detection resistor are connected with the second input end of the voltage comparator and the output end of the field effect transistor respectively; the output end of the voltage comparator is connected with the second input end of the field effect transistor; and the output end of the detection resistor is the common end of the power processor. The power processor is configured to: receive the loop current of the LED lamp string, control the voltage comparator to obtain a detection voltage according to the resistance value of the detection resistor and the loop current; control the voltage comparator to generate an adjustment voltage signal based on the size relationship between the reference voltage provided by the reference voltage circuit and the detection voltage, and send the adjustment voltage signal to the field effect transistor; the adjustment voltage signal is set to be an increased loop current when the detection voltage is less than the reference voltage, and a decreased loop current when the detection voltage is greater than the reference voltage; when the adjustment voltage signal is the increased loop current, control the field effect transistor to be in a conductive state to increase the loop current; and when the adjustment voltage signal is the decreased loop current, control the field effect transistor to be in a non-conductive state to decrease the loop current.

2. The LED lamp string of claim 1, wherein, The reference voltage is greater than or equal to 0.5% of an external input voltage input to the LED lamp string.

3. The LED lamp string of claim 1, wherein, Each of the LED lamp beads comprises two or more light emitting LED chips connected in series.

4. The LED lamp string of claim 3, wherein, The control of the voltage comparator to obtain the detection voltage according to the resistance value of the detection resistor and the loop current comprises: the detection voltage is obtained by the following calculation formula: V J = I x R J wherein V J represents a detection voltage, I represents a circuit current, and R J represents a resistance value of the detection resistor.

5. The LED lamp string of claim 4, wherein, The calculation formula of the resistance value of the detection resistor is: wherein V represents an external input voltage of the LED light string, R d represents an equivalent resistance of the light emitting unit.

6. The LED lamp string of claim 1, wherein, The reference voltage circuit comprises a one-time programmable memory and a band gap reference source.

7. The LED lamp string of claim 1, wherein, The power processor is packaged in one of the LED lamp beads in the loop of the light emitting unit.

8. The LED lamp string of claim 1, wherein, The LED lamp string further comprises a pair of male and female connectors. The male and female connectors are respectively located at two ends of the LED lamp string to connect the LED lamp string in series into a loop.

9. An LED light string combination, characterized in that The LED lamp string comprises a plurality of LED lamp strings according to any one of claims 1-8.

10. An LED system, characterized by The LED lamp string combination comprises a rectifier and the LED lamp string according to claim 9 connected with the rectifier.

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