High-voltage power-free serially connectable LED light string

Abstract

The utility model discloses a high pressure power -free can be in series LED lamp string, including plug, tail plug, a plurality of lamp pearl disc and voltage reducing current -limiting circuit. Plug and tail plug are connected through firewire and zero line, and form complete circuit passage. Voltage reducing current -limiting circuit input end connects plug firewire output end, is used for limiting current voltage reduction to input voltage. Each lamp pearl disc is equipped with the LED lamp pearl of opposite back -to -back connection in pairs, forms no bridge type rectification topology structure, simplifies circuit design and promotes reliability. A plurality of lamp pearl discs are in series in proper order, and are connected respectively through firewire and zero line, realize multi -lamp string parallel expansion. Tail plug is equipped with the plug -in structure matched with plug, can realize the pluggable connection of multiple lamp string, has good modularization stringing capacity. The utility model has the advantages of simple structure, need not external power supply, convenient installation, stringing nimble etc.

Description

Technical Field

[0001] This utility model relates to the field of LED light string technology, and in particular to a high-voltage, power-free LED light string that can be connected in series. Background Technology

[0002] With the rapid development of LED lighting technology, LED lights are widely used in indoor and outdoor lighting, decorative lighting, and holiday lighting due to their advantages such as high brightness, low energy consumption, and long lifespan. In multi-lamp series applications, users often want to be able to directly connect multiple LED strings to simplify the wiring structure, thereby achieving scalable series lighting effects.

[0003] Most LED light strings on the market currently use low-voltage power supply, such as 12V or 24V, requiring an external transformer power supply, which is cumbersome and costly. Furthermore, some LED light strings that use high-voltage AC direct power supply generally require bridge rectifier circuits and electrolytic capacitors to achieve rectification and current limiting. This not only results in a complex overall structure, large size, and poor reliability, but also poses certain safety hazards due to the aging of the capacitors.

[0004] Most existing LED light strings lack good modularity and cannot achieve plug-and-play scalability, making maintenance and wiring extremely inconvenient, especially in large-scale outdoor applications. Furthermore, traditional bridge rectifier structures suffer from significant power loss and low circuit efficiency.

[0005] Therefore, there is an urgent need for an LED string solution that is simple in structure, low in cost, can be directly connected to high-voltage AC power, supports pluggable series connection of multiple sets of light strings, and requires no additional power supply equipment, in order to meet the comprehensive needs of modern lighting for high reliability, convenience and safety. Utility Model Content

[0006] To address the shortcomings of existing technologies, the purpose of this utility model is to provide a high-voltage, power-free LED light string that can be connected in series. By adopting a bridgeless rectifier topology and a modular series connection structure, it achieves an LED light string that does not require an external power supply under high voltage, can be flexibly connected in series, has a simplified structure, and is safe and reliable.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a high-voltage, power-free LED string that can be connected in series, including a plug, a tail plug, multiple LED bead disks, and a step-down current limiting circuit;

[0008] The plug has a live wire output terminal and a neutral wire output terminal, and the tail plug has a live wire input terminal and a neutral wire input terminal. A live wire is connected between the live wire output terminal of the plug and the live wire input terminal of the tail plug, and a neutral wire is connected between the neutral wire output terminal of the plug and the neutral wire input terminal of the tail plug.

[0009] The input terminal of the step-down current limiting circuit is connected to the live wire output terminal of the plug;

[0010] Each of the aforementioned lamp bead disks is provided with:

[0011] The first LED chip pad and the second LED chip pad are arranged vertically opposite each other.

[0012] The first and second wiring pads are arranged opposite each other from left to right.

[0013] The first LED and the second LED are connected back-to-back between the first LED pad and the second LED pad, forming a bridgeless rectifier topology, wherein:

[0014] The positive terminal of the first LED bead is directly connected to the pad of the second LED bead, and the negative terminal is directly connected to the pad of the first LED bead.

[0015] The positive terminal of the second LED is directly connected to the pad of the first LED, and the negative terminal is directly connected to the pad of the second LED.

[0016] The multiple LED chip disks are connected in series with each other, specifically: in two adjacent LED chip disks, the second wiring pad of the first LED chip disk is electrically connected to the first wiring pad of the second LED chip disk through the live wire.

[0017] The first wiring pads of the plurality of lamp bead disks are connected in series with each other via the neutral wire;

[0018] The output terminal of the step-down current limiting circuit is electrically connected to the first wiring pad of the first LED chip; the second wiring pad of the last LED chip is electrically connected to the live wire input terminal of the tail plug.

[0019] The neutral input terminal of the tail plug is electrically connected to the neutral wire;

[0020] The tail plug is provided with a plug-in structure that matches the plug, so that the plug of the next LED string can be plugged into the tail plug of the current LED string.

[0021] Furthermore, the step-down current limiting circuit includes a step-down capacitor C1 and a discharge resistor R1;

[0022] The first terminal of the step-down capacitor C1 and the first terminal of the discharge resistor R1 are both connected to the input terminal of the step-down current limiting circuit; the second terminal of the step-down capacitor C1 and the second terminal of the discharge resistor R1 are both connected to the output terminal of the step-down current limiting circuit.

[0023] The step-down capacitor C1 is configured to step down and limit the current of the live wire input to the step-down current limiting circuit; the discharge resistor R1 is configured to discharge the step-down capacitor C1 when the LED string is powered off.

[0024] Furthermore, the substrate of the LED chip is a flame-retardant FR-4 circuit board, and an isolation groove is provided between the first LED chip pad and the second LED chip pad. The isolation groove is configured to block the arc path between the first LED chip and the second LED chip.

[0025] Furthermore, the step-down current limiting circuit is encapsulated in a flame-retardant engineering plastic shell, and the surface of the flame-retardant engineering plastic shell is provided with heat dissipation fins, the heat dissipation fins corresponding to the installation position of the discharge resistor R1.

[0026] Furthermore, the plug-in structure of the tail plug includes a live wire pin, a neutral wire pin, and an insulating shell. The insulating shell is provided with a guide groove to prevent mis-insertion, and the length of the live wire pin is greater than the length of the neutral wire pin.

[0027] Furthermore, a temperature sensor is embedded in the substrate of the lamp bead disk, and multiple heat dissipation channels parallel to the wiring direction of the live wire and the neutral wire are opened on the back of the substrate.

[0028] The heat dissipation channel has a trapezoidal cross-section, a depth of 0.5mm to 1mm, and a spacing of 2mm to 3mm between adjacent channels;

[0029] The temperature sensor is in contact with the aluminum substrate of the first LED bead through a thermally conductive silicone layer.

[0030] Furthermore, the casing surface of the buck current limiting circuit is provided with a voltage detection contact group, including:

[0031] The first contact is connected to the live wire connection pad of the first LED chip disk via a wire;

[0032] The second contact is connected to the live wire connection pad of the last lamp bead disk via a wire.

[0033] The third contact is connected to the trigger pin of the thyristor voltage regulator unit;

[0034] The heat sink of the thyristor voltage regulating unit is fixedly connected to the heat dissipation fins.

[0035] Furthermore, the insulating outer shell of the tail plug is provided with an annular metal shielding layer, the inner wall of which wraps the live wire pin;

[0036] The metal shielding layer is connected to the grounding pad located at the bottom of the insulating shell via an elastic copper sheet;

[0037] The heat sink of the thyristor voltage regulating unit extends above the grounding pad, with a gap of 0.5mm to 1mm between them.

[0038] The beneficial effects of this utility model are:

[0039] (1) No external power supply required: The LED light string in this utility model can be directly connected to high voltage AC power to work without the need for an external transformer or rectifier power supply device, which simplifies the use and reduces the system cost.

[0040] (2) Bridgeless rectifier topology: The bridgeless rectifier structure is formed by back-to-back connected LED beads, which eliminates the traditional bridge rectifier and electrolytic capacitor, reducing circuit complexity and improving system stability and safety.

[0041] (3) Series connection design: The tail of the light string is equipped with a plug-in structure that matches the plug, which can realize the rapid series connection between multiple light strings, improve the expandability and installation flexibility, and facilitate maintenance and networking.

[0042] (4) Modular design of LED chip tray: Each LED chip tray has a standardized structure and is connected in series with the live wire and the neutral wire, which facilitates mass production and replacement, and improves product consistency and reliability.

[0043] (5) Current limiting and voltage reduction circuit improves safety: The built-in voltage reduction and current limiting circuit effectively regulates the high voltage power supply to prevent excessive current from damaging the LED beads, thereby improving product life and safety. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the medium-voltage, no-power-supply LED light string of this utility model;

[0045] Figure 2 This is a schematic diagram of the structure of the lamp bead disk in this utility model.

[0046] Reference numerals in the attached diagram: 1. Plug; 2. Tail plug; 3. LED chip tray; 31. First LED chip pad; 32. Second LED chip pad; 33. First wiring pad; 34. Second wiring pad; 4. Step-down current limiting circuit; 5. First LED chip; 6. Second LED chip; 7. Isolation groove. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, and the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0048] Example 1, referring to Figures 1 to 2 This is the first embodiment of the present utility model. This embodiment provides a high-voltage, power-free LED light string that can be connected in series. By adopting a bridgeless rectifier topology and a modular series connection structure, it realizes an LED light string that does not require an external power supply under high voltage, can be flexibly connected in series, has a simplified structure, and is safe and reliable. It includes: a plug 1, a tail plug 2, multiple LED bead disks 3, and a step-down current limiting circuit 4.

[0049] Plug 1 has a live wire output terminal and a neutral wire output terminal for connecting to AC power; plug 2 has a live wire input terminal and a neutral wire input terminal for pluggable connection to the next set of light strings. Plug 1 and plug 2 form a complete circuit path through the live and neutral wires.

[0050] The input terminal of the step-down and current-limiting circuit 4 is connected to the live wire output terminal of the plug 1, and the output terminal is connected to the first wiring pad 33 of the first LED bead disk 3. It is used to limit and reduce the voltage of the input high-voltage AC power to ensure the normal operation of the LED beads.

[0051] Each LED bead plate 3 has:

[0052] The first LED chip pad 31 and the second LED chip pad 32 are arranged symmetrically, one above the other.

[0053] The first wiring pad 33 and the second wiring pad 34 are arranged symmetrically on the left and right sides;

[0054] A pair of LED beads connected back to back, namely the first LED bead 5 and the second LED bead 6, are connected between the first LED bead pad 31 and the second LED bead pad 32.

[0055] In this configuration, the positive terminal of the first LED bead 5 is connected to the second LED bead pad 32, and the negative terminal is connected to the first LED bead pad 31; the positive terminal of the second LED bead 6 is connected to the first LED bead pad 31, and the negative terminal is connected to the second LED bead pad 32, thus forming a bridgeless rectifier topology.

[0056] Multiple LED chip trays 3 are connected in series in the following way: the second wiring pad 34 of the previous LED chip tray 3 is connected to the first wiring pad 33 of the next LED chip tray 3 via a live wire; the first wiring pads 33 of all LED chip trays 3 are connected in series via a neutral wire.

[0057] The second wiring pad 34 of the last LED chip 3 is connected to the live wire input terminal of the tail plug 2, and the neutral wire input terminal of the tail plug 2 is connected to the neutral wire.

[0058] Working principle of Example 1:

[0059] When plug 1 is connected to AC power: during the positive half-cycle of AC power, the current path is: live wire → first LED bead 5 (forward conduction) → neutral wire, forming a loop, and the first LED bead 5 conducts and emits light;

[0060] During the negative half-cycle of the AC current, the current path is: live wire → second LED bead 6 (forward conduction) → neutral wire, forming a loop, and the second LED bead 6 conducts and emits light;

[0061] Because the two LED beads are connected back to back, they are turned on alternately during the positive and negative half-cycles of AC, thus achieving a light-emitting effect similar to full-wave rectification. This replaces the traditional bridge rectifier circuit, which not only reduces the number of components and circuit complexity, but also improves system stability and safety.

[0062] The tail plug 2 allows another set of LED strings with the same structure to be plugged and detached from the current string through plug 1, forming a multi-segment series expansion, which facilitates rapid wiring and maintenance in large-scale application scenarios.

[0063] Example 2, refer to Figure 2 This is the second embodiment of the present invention. Unlike the previous embodiment, this embodiment optimizes the structure of the step-down current limiting circuit 4, thereby improving electrical safety and stability.

[0064] The step-down current limiting circuit 4 includes: a step-down capacitor C1 and a discharge resistor R1. Wherein:

[0065] The first end of the step-down capacitor C1 and the first end of the discharge resistor R1 are connected together to the input end of the step-down current limiting circuit 4, that is, the live wire output end of plug 1.

[0066] The second end of the step-down capacitor C1 and the second end of the discharge resistor R1 are connected together to the output end of the step-down current limiting circuit 4, which is further connected to the first wiring pad 33 of the first lamp bead disk 3.

[0067] The step-down capacitor C1 is a CBB capacitor adapted to high-voltage AC input, and its capacitance value is designed based on the total power of the light string, the voltage level, and the LED operating current; the discharge resistor R1 is a high-resistance resistor, and its resistance value is determined according to the charge release rate of the step-down capacitor C1 to ensure safe discharge.

[0068] Working principle of Example 2:

[0069] When the LED string is powered on (connected to AC power):

[0070] The high-voltage AC power first enters the step-down and current-limiting circuit 4; the step-down capacitor C1 reduces the voltage of the live wire current and limits the current flowing through the circuit through impedance, protecting the downstream LED beads and the entire circuit; the AC power after being limited by the step-down capacitor C1 passes through the back-to-back LED beads in the LED bead disk 3, and emits light alternately in the positive and negative half-cycles as described in Example 1, achieving a bridgeless rectification lighting effect.

[0071] When the LED light string is powered off:

[0072] To prevent residual charge on the step-down capacitor C1 from causing electric shock or damage to components, the discharge resistor R1 automatically provides a discharge path for the step-down capacitor C1 when there is no external power supply, causing its voltage to quickly decrease to below a safe value, thus ensuring safe use.

[0073] This embodiment combines the step-down capacitor C1 with the discharge resistor R1 to form a simple and efficient step-down current limiting circuit 4, which not only simplifies the traditional power supply design, but also has the advantages of high electrical safety, low component cost and compact overall structure, making it particularly suitable for LED light strings used in large quantities outdoors.

[0074] Example 3 is the third embodiment of this utility model. Unlike the previous embodiment, the system structure is further optimized based on Example 2, and the thermal management, safe connection and intelligent voltage regulation capabilities are improved, as detailed below:

[0075] The step-down current limiting circuit 4 is encapsulated in a flame-retardant engineering plastic housing. The housing has good insulation and heat resistance, and the surface of the flame-retardant engineering plastic housing is provided with heat dissipation fins. The heat dissipation fins correspond to the installation position of the discharge resistor R1, which facilitates rapid heat dissipation of high-temperature devices and prevents overheating failure.

[0076] The plug structure of the tail plug 2 includes a live wire pin, a neutral wire pin, and an insulating shell. The insulating shell is provided with a guide groove to prevent mis-insertion, which restricts the insertion direction and ensures electrical safety. The length of the live wire pin is greater than the length of the neutral wire pin. When plugging in, the live wire is connected first, which is beneficial to grounding protection and current stability.

[0077] The substrate of the LED bead disk 3 is embedded with a temperature sensor to monitor the heating status in real time, and multiple heat dissipation channels parallel to the wiring direction of the live wire and neutral wire are opened on the back of the substrate.

[0078] The heat dissipation channel has a trapezoidal cross-section with a depth of 0.5mm to 1mm and a spacing of 2mm to 3mm between adjacent channels, which helps air convection and improves heat dissipation efficiency.

[0079] The temperature sensor contacts the aluminum substrate of the first LED bead 5 through a thermally conductive silicone layer, ensuring a sensitive and accurate temperature response.

[0080] The casing of the step-down current limiting circuit 4 is provided with a voltage detection contact group, including:

[0081] The first contact point is connected to the live wire connection pad of the first LED chip 3 via a wire;

[0082] The second contact is connected to the live wire solder pad of the last LED chip 3 via a wire;

[0083] The third contact is connected to the trigger pin of the thyristor voltage regulator unit;

[0084] The heat sink and heat dissipation fins of the thyristor voltage regulating unit are snapped together to achieve centralized heat conduction.

[0085] Preferably, the insulating shell of the tail plug 2 is provided with an annular metal shielding layer, the inner wall of which is wrapped with the live wire pin to reduce external electromagnetic interference.

[0086] The metal shielding layer is connected to the grounding pad located at the bottom of the insulating shell via a flexible copper sheet;

[0087] The heat sink of the thyristor voltage regulator unit extends above the grounding pad, with a gap of 0.5mm to 1mm between them, further enhancing electrostatic discharge and safe grounding capabilities.

[0088] Working principle of Example 3:

[0089] Step-down current limiting and rectification: Similar to Example 2, AC power is input to step-down current limiting circuit 4 via the live wire. Step-down capacitor C1 limits the current, and the positive and negative half cycles respectively turn on the back-to-back LED beads to achieve bridgeless rectification and light emission.

[0090] Temperature control and voltage regulation process: During continuous operation, the temperature sensor monitors the temperature rise of the LED substrate. If the temperature exceeds the set threshold, the thyristor voltage regulation unit can be triggered through the third contact to reduce the input voltage, reduce heat generation, and extend the life.

[0091] Heat dissipation optimization mechanism: The discharge resistor R1 and the thyristor voltage regulation unit generate heat in a concentrated manner. The heat is quickly released into the air through the fins and heat dissipation channels, which effectively prevents the device from overheating and ensures the long-term stable operation of the system.

[0092] Shielding and grounding protection: The ring-shaped metal shielding layer weakens the electromagnetic interference caused by the high-voltage live wire pins, forming an electromagnetic protection barrier; at the same time, it forms an electrostatic discharge path with the thyristor heat sink through the grounding pad to prevent surge breakdown.

[0093] This embodiment not only achieves efficient voltage reduction and current limiting of LED light strings and alternating positive and negative half-cycle light emission, but also integrates functions such as intelligent voltage regulation, temperature monitoring, safety grounding and electromagnetic shielding, which greatly improves the safety, maintainability and environmental adaptability of the product, and is particularly suitable for high-power series lighting scenarios in complex power grid environments.

[0094] Preferably, the substrate of the LED chip 3 is a flame-retardant FR-4 circuit board, whose flame retardancy rating meets the UL94V-0 standard; and an isolation groove 7 is provided between the first LED chip pad 31 and the second LED chip pad 32, with the parameters of 0.5mm width and 0.3mm depth. The isolation groove 7 is configured to block the arc path between the first LED chip 5 and the second LED chip 6, and the isolation groove 7 penetrates the copper foil layer of the substrate and extends to the glass fiber layer.

[0095] Specifically, in this embodiment, when the lamp string is connected to 220V AC high voltage: the critical distance for high voltage to break down air is 0.1mm / 100V (Paschen's Law). The isolation groove 7 forcibly separates the distance between the first lamp bead pad 31 and the second lamp bead pad 32 to ≥0.5mm, so that the arc cannot cross under 220V voltage (≥0.22mm is required); the isolation increases the arc creepage path to 1.2mm, which far exceeds the 0.64mm required by the safety standard IEC 62368-1.

[0096] When abnormally high temperatures cause the substrate to carbonize, the flame retardant of FR-4 material decomposes and absorbs heat. At this time, the isolation groove 7 can cut off the carbonization conduction path, thereby preventing the formation of a conductive carbon bridge between the live wire and the neutral wire. Therefore, the setting of the isolation groove 7 significantly improves the electrical safety of the lamp bead disk 3.

[0097] The above are merely preferred embodiments of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are within its protection scope. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within its protection scope.

Claims

1. A high-voltage, power-free LED light string that can be connected in series, characterized in that: It includes a plug (1), a tail plug (2), multiple LED bead arrays (3), and a step-down current limiting circuit (4); The plug (1) has a live wire output terminal and a neutral wire output terminal, the tail plug (2) has a live wire input terminal and a neutral wire input terminal, a live wire is connected between the live wire output terminal of the plug (1) and the live wire input terminal of the tail plug (2), and a neutral wire is connected between the neutral wire output terminal of the plug (1) and the neutral wire input terminal of the tail plug (2). The input terminal of the step-down current limiting circuit (4) is connected to the live wire output terminal of the plug (1); Each of the aforementioned lamp bead disks (3) is provided with: The first LED chip pad (31) and the second LED chip pad (32) are arranged vertically opposite each other. The first wiring pad (33) and the second wiring pad (34) are arranged opposite each other on the left and right. The first LED (5) and the second LED (6) are connected back-to-back between the first LED pad (31) and the second LED pad (32) to form a bridgeless rectifier topology, wherein: The positive electrode of the first LED bead (5) is directly connected to the second LED bead pad (32), and the negative electrode is directly connected to the first LED bead pad (31); The positive electrode of the second LED bead (6) is directly connected to the first LED bead pad (31), and the negative electrode is directly connected to the second LED bead pad (32); The multiple LED bead disks (3) are connected in series with each other, specifically: in two adjacent LED bead disks (3), the second wiring pad (34) of the first LED bead disk (3) is electrically connected to the first wiring pad (33) of the second LED bead disk (3) through the live wire; The first wiring pads (33) of the plurality of lamp bead disks (3) are connected in series with each other through the neutral wire; The output terminal of the step-down current limiting circuit (4) is electrically connected to the first wiring pad (33) of the first lamp bead plate (3); the second wiring pad (34) of the last lamp bead plate (3) is electrically connected to the live wire input terminal of the tail plug (2); The neutral input terminal of the tail plug (2) is electrically connected to the neutral wire; The tail plug (2) is provided with a plug-in structure that matches the plug (1), so that the plug (1) of the next LED string can be plugged into and detachably connected to the tail plug (2) of the current LED string.

2. The high-voltage, power-free, series-connectable LED light string according to claim 1, characterized in that: The step-down current limiting circuit (4) includes a step-down capacitor C1 and a discharge resistor R1; The first end of the step-down capacitor C1 and the first end of the discharge resistor R1 are both connected to the input end of the step-down current limiting circuit (4); the second end of the step-down capacitor C1 and the second end of the discharge resistor R1 are both connected to the output end of the step-down current limiting circuit (4). The step-down capacitor C1 is configured to step down and limit the current of the live wire input to the step-down current limiting circuit (4); the discharge resistor R1 is configured to discharge the step-down capacitor C1 when the LED string is powered off.

3. The high-voltage, power-free LED string according to claim 1, characterized in that: The substrate of the LED chip plate (3) is a flame-retardant FR-4 circuit board, and an isolation groove (7) is provided between the first LED chip pad (31) and the second LED chip pad (32). The isolation groove (7) is configured to block the arc path between the first LED chip (5) and the second LED chip (6).

4. The high-voltage, power-free, series-connectable LED light string according to claim 2, characterized in that: The step-down current limiting circuit (4) is encapsulated in a flame-retardant engineering plastic shell, and the surface of the flame-retardant engineering plastic shell is provided with heat dissipation fins, the heat dissipation fins being corresponding to the installation position of the discharge resistor R1.

5. The high-voltage, power-free LED string according to claim 4, characterized in that: The plug-in structure of the tail plug (2) includes a live wire pin, a neutral wire pin and an insulating shell. The insulating shell is provided with a guide groove to prevent mis-insertion, and the length of the live wire pin is greater than the length of the neutral wire pin.

6. The high-voltage, power-free LED string according to claim 5, characterized in that: The substrate of the lamp bead disk (3) is embedded with a temperature sensor, and multiple heat dissipation channels parallel to the wiring direction of the live wire and the neutral wire are opened on the back of the substrate. The heat dissipation channel has a trapezoidal cross-section, a depth of 0.5mm to 1mm, and a spacing of 2mm to 3mm between adjacent channels; The temperature sensor is in contact with the aluminum substrate of the first LED bead (5) through a thermally conductive silicone layer.

7. The high-voltage, power-free LED string according to claim 6, characterized in that: The casing surface of the step-down current limiting circuit (4) is provided with a voltage detection contact group, including: The first contact point is connected to the live wire connection pad of the first lamp bead plate (3) via a wire; The second contact is connected to the live wire connection pad of the last lamp bead disk (3) via a wire; The third contact is connected to the trigger pin of the thyristor voltage regulator unit; The heat sink of the thyristor voltage regulating unit is fixedly connected to the heat dissipation fins.

8. The high-voltage, power-free LED string according to claim 7, characterized in that: The insulating shell of the tail plug (2) is provided with an annular metal shielding layer, the inner wall of which wraps the live wire pin; The metal shielding layer is connected to the grounding pad located at the bottom of the insulating shell via an elastic copper sheet; The heat sink of the thyristor voltage regulating unit extends above the grounding pad, with a gap of 0.5mm to 1mm between them.

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