Wide-input-voltage flicker-free LED driver circuit

Abstract

The present application discloses a wide-input-voltage flicker-free LED driver circuit, comprising a rectifier circuit, a snubber circuit, a first conducting branch, a second conducting branch, a third conducting branch and a load branch. When the real-time voltage rectified by the rectifier circuit is greater than the turn-on voltage of the load branch, the second conducting branch is turned on, and the first conducting branch and the third conducting branch are turned off. When the real-time voltage is less than the turn-on voltage of the load branch, the first conducting branch is turned on, and the second conducting branch and the third conducting branch are turned off. When the real-time voltage continues to decrease until the first conducting branch and the second conducting branch are turned off, the third conducting branch is turned on. Therefore, the problem of insufficient input current when the input voltage is reduced can be solved, it is guaranteed that the LED luminance is consistent under the wide input voltage, the flicker problem caused by mains supply ripples is solved, and the requirement of environmental protection authentication on sub-harmonics is met.

Description

A wide input voltage flicker-free LED driver circuit Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a wide input voltage flicker-free LED driving circuit. Background Art

[0002] LED lighting, as an energy-saving and environmentally friendly lighting method, has become the mainstream lighting method. Currently, people's requirements for flicker, wide voltage, low cost, and subharmonics for various environmental certifications are important indicators to pay attention to.

[0003] Because the LED loads used in LED lighting require direct current to drive, and the current flowing through the LED loads determines the brightness of the LEDs, existing LED driver control systems have the following main drawbacks: During the LED driver control process, low-frequency ripple from the input AC mains is often introduced into the LED loads, causing light fluctuations in the LED loads, which in turn lead to flickering. The mains power grid experiences voltage fluctuations due to various factors. When the voltage is low, it cannot maintain the current value of the LED loads, resulting in a decrease in LED brightness and a reduced user experience. The subharmonic requirements of various environmental certifications make existing circuits ineffective.

[0004] Therefore, it is necessary to develop a simple and reliable LED driver circuit with flicker removal and wide input voltage, and meet the input current harmonic requirements. Technical issues

[0005] The main purpose of this application is to provide a wide input voltage flicker-free LED driving circuit. Technical Solutions

[0006] To achieve the above objectives, the present application provides a wide input voltage flicker-free LED driver circuit, comprising a rectifier circuit, an absorption circuit, a first conductive branch, a second conductive branch, a third conductive branch, and a load branch. The input end of the rectifier circuit is connected to the AC mains, the output end of the rectifier circuit is connected to the input end of the absorption circuit and the input end of the second conductive branch, the output end of the absorption circuit is connected to the input end of the first conductive branch and the input end of the third conductive branch, and the load branch comprises a first resistor R1, a first group of LED loads, a second resistor R2, and a second group of LEDs connected in series. load, the output end of the first conductive branch and the output end of the second conductive branch are connected to the first end of the first resistor R1, and the output end of the third conductive branch is connected to the first end of the second resistor R2, wherein, when the real-time voltage after rectification by the rectifier circuit is greater than the conduction voltage of the load branch, the second conductive branch is turned on, and the first conductive branch and the third conductive branch are turned off; when the real-time voltage is less than the conduction voltage of the load branch, the first conductive branch is turned on, and the second conductive branch and the third conductive branch are turned off; when the real-time voltage continues to decrease until the first conductive branch and the second conductive branch are both turned off, the third conductive branch is turned on.

[0007] In the wide input voltage flicker-free LED driving circuit provided in the present application, the absorption circuit includes a diode D1 and a capacitor C1, the positive electrode of the diode D1 is connected to the output end of the rectifier circuit and the input end of the second conductive branch, and the negative electrode of the diode D1 is connected to the first end of the capacitor C1 and the input end of the first conductive branch and the input end of the third conductive branch.

[0008] In the wide input voltage flicker-free LED driving circuit provided in the present application, the first conducting branch includes a first operational amplifier U1 and a first MOS transistor Q1, the drain of the first MOS transistor Q1 is connected to the cathode of the diode D1, the source of the first MOS transistor Q1 is connected to the first end of the first resistor R1 and the inverting input of the first operational amplifier U1, the gate of the first MOS transistor Q1 is connected to the output of the first operational amplifier U1, and the non-inverting input of the first operational amplifier U1 is connected to the first reference voltage REF1.

[0009] In the wide input voltage flicker-free LED driving circuit provided in the present application, the second conducting branch includes a second operational amplifier U2 and a second MOS transistor Q2, the drain of the second MOS transistor Q2 is connected to the anode of the diode D1, the source of the second MOS transistor Q2 is connected to the first end of the first resistor R1 and the inverting input terminal of the second operational amplifier U2, the gate of the second MOS transistor Q2 is connected to the output terminal of the second operational amplifier U2, and the non-inverting input terminal of the second operational amplifier U2 is connected to the second reference voltage REF2.

[0010] In the wide input voltage flicker-free LED driving circuit provided in the present application, the second reference voltage REF2 is greater than the first reference voltage REF1.

[0011] In the wide input voltage flicker-free LED driver circuit provided in the present application, the third conducting branch includes a third operational amplifier U3 and a third MOS transistor Q3, the drain of the third MOS transistor Q3 is connected to the cathode of the diode D1, the source of the third MOS transistor Q3 is connected to the first end of the second resistor R2 and the inverting input of the third operational amplifier U3, the gate of the third MOS transistor Q3 is connected to the output of the third operational amplifier U3, and the non-inverting input of the third operational amplifier U3 is connected to the third reference voltage REF3.

[0012] In the wide input voltage flicker-free LED driver circuit provided in the present application, the third conducting branch further includes a fourth operational amplifier U4 and a fourth MOS transistor Q4, the drain of the fourth MOS transistor Q4 is connected to the anode of the diode D1, the source of the fourth MOS transistor Q4 is connected to the first end of the second resistor R2 and the inverting input terminal of the fourth operational amplifier U4, the gate of the fourth MOS transistor Q4 is connected to the output terminal of the fourth operational amplifier U4, and the non-inverting input terminal of the fourth operational amplifier U4 is connected to the fourth reference voltage REF4.

[0013] In the wide input voltage flicker-free LED driving circuit provided in the present application, the fourth reference voltage REF4 is greater than the third reference voltage REF3. Beneficial effects

[0014] The wide input voltage flicker-free LED driving circuit provided by the present application has the following beneficial effects: the wide input voltage flicker-free LED driving circuit provided by the present application includes a rectifier circuit, an absorption circuit, a first conduction branch, a second conduction branch, a third conduction branch and a load branch. When the real-time voltage after rectification by the rectifier circuit is greater than the conduction voltage of the load branch, the second conduction branch is turned on, and the first conduction branch and the third conduction branch are turned off. When the real-time voltage is less than the conduction voltage of the load branch, the first conduction branch is turned on, and the second conduction branch and the third conduction branch are turned off. When the real-time voltage continues to decrease until both the first conduction branch and the second conduction branch are turned off, the third conduction branch is turned on. In this way, the problem of insufficient input current when the input voltage decreases can be improved, and the LED luminous brightness is guaranteed to be consistent under a wide input voltage. The flicker problem caused by the mains ripple is also improved, meeting the requirements of environmental protection certification for subharmonics. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only embodiments of the present application. Those skilled in the art can also derive other drawings based on the provided drawings without inventive effort.

[0016] FIG1 is a schematic diagram showing the circuit structure of a wide input voltage flicker-free LED driving circuit provided by an embodiment of the present application;

[0017] Figure 2 shows the voltage waveform after the AC voltage passes through the rectifier circuit;

[0018] FIG3 shows the AC current and voltage waveforms and the current waveform when the circuit of the present application is working;

[0019] FIG4 is a schematic diagram showing the circuit structure of a wide input voltage flicker-free LED driving circuit provided by another embodiment of the present application. Modes for Carrying Out the Invention

[0020] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate exemplary embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0022] The general idea of ​​this application is to address the problems of flicker, voltage fluctuation and inability to meet subharmonic requirements in existing LED drive circuits, and to provide a wide input voltage flicker-free LED drive circuit, comprising a rectifier circuit, an absorption circuit, a first conduction branch, a second conduction branch, a third conduction branch and a load branch. When the real-time voltage after rectification by the rectifier circuit is greater than the conduction voltage of the load branch, the second conduction branch is turned on, and the first and third conduction branches are turned off. When the real-time voltage is less than the conduction voltage of the load branch, the first conduction branch is turned on, and the second and third conduction branches are turned off. When the real-time voltage continues to decrease until both the first and second conduction branches are turned off, the third conduction branch is turned on. In this way, the problem of insufficient input current when the input voltage decreases can be improved, and the LED luminous brightness is guaranteed to be consistent under a wide input voltage. The flicker problem caused by mains ripple is also improved, and the subharmonic requirements of environmental protection certification are met.

[0023] In order to better understand the above technical solution, the above technical solution will be described in detail below in combination with the drawings and specific implementation methods of the specification. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0024] FIG1 shows a circuit diagram of a wide input voltage, flicker-free LED driver circuit provided in one embodiment of the present application. As shown in FIG1 , the wide input voltage, flicker-free LED driver circuit provided in this embodiment includes a rectifier circuit 10, an absorption circuit 20, a first conductive branch 30, a second conductive branch 40, a third conductive branch 50, and a load branch 60. The rectifier circuit has an input connected to an AC mains supply, configured to receive the AC mains supply and rectify the AC mains supply for output. When the real-time voltage after rectification by the rectifier circuit is greater than the load branch's conduction voltage, the second conductive branch is turned on, and the first and third conductive branches are turned off. When the real-time voltage is less than the load branch's conduction voltage, the first conductive branch is turned on, and the second and third conductive branches are turned off. When the real-time voltage continues to decrease until both the first and second conductive branches are turned off, the third conductive branch is turned on. Thus, when the rectified real-time voltage is high, power is drawn through the first conductive branch. When the rectified real-time voltage drops below the conduction voltage of the load branch, power is drawn through the second conductive branch. This allows continuous current to flow through the LED lamp beads in the load branch, achieving continuous and stable light emission and solving the problem of flicker. When the rectified real-time voltage further drops to the point where both the first and second conductive branches cannot operate, the third conductive branch allows some LED lamp beads in the load branch to continue operating, so that current still flows through the LED light-emitting diodes under low voltage, causing the LEDs to emit light.

[0025] Specifically, in one embodiment of the application, as shown in Figure 1, the absorption circuit 20 includes a diode D1 and a capacitor C1, wherein the positive electrode of the diode D1 is connected to the output end of the rectifier circuit and the input end of the second conductive branch, and the negative electrode of the diode D1 is connected to the first end of the capacitor C1 and the input end of the first conductive branch and the input end of the third conductive branch. Thus, when a spike voltage enters the outside, it will be absorbed by the capacitor C1, protecting the devices at the back end, thereby improving the reliability of the circuit. In addition, in the prior art, the capacitor C1 is directly charged by the rectifier current, which will cause subharmonics to not meet the requirements of environmental certification for subharmonics. In the present application, as shown in Figure 1, the capacitor C1 is charged by the diode D1. When the capacitor voltage is high enough and greater than the real-time voltage after rectification, the capacitor is no longer charged. At this time, since the real-time voltage after rectification is greater than the conduction voltage of the load branch, the second conductive branch is turned on, so the AC voltage from the mains passes through the rectifier circuit to the second conductive branch and then through the load branch to form a loop. During the time when capacitor C1 is not charging, current is also drawn to the line network through the second conducting branch. The line network input current waveform (the smooth waveform is the current waveform) is shown in Figure 3. This waveform helps to improve harmonics so that the subharmonics meet the subharmonic requirements of environmental certification.

[0026] Specifically, in one embodiment of the present application, the first conducting branch includes a first operational amplifier U1 and a first MOS transistor Q1, the second conducting branch includes a second operational amplifier U2 and a second MOS transistor Q2, the third conducting branch includes a third operational amplifier U3 and a third MOS transistor Q3, and the load branch includes a first resistor R1, a first group of LED loads, a second resistor R2, and a second group of LED loads connected in series, wherein the first group of LED loads and the second group of LED loads respectively include multiple LED lamp beads.

[0027] Furthermore, in one embodiment of the application, the drain of the first MOS transistor Q1 is connected to the cathode of the diode D1, the source of the first MOS transistor Q1 is connected to the first end of the first resistor R1 and the inverting input terminal of the first operational amplifier U1, the gate of the first MOS transistor Q1 is connected to the output terminal of the first operational amplifier U1, and the non-inverting input terminal of the first operational amplifier U1 is connected to the first reference voltage REF1; the drain of the second MOS transistor Q2 is connected to the anode of the diode D1, the source of the second MOS transistor Q2 is connected to the first end of the first resistor R1 and the inverting input terminal of the second operational amplifier The first MOS transistor Q3 is connected to the inverting input terminal of the second operational amplifier U2, the gate of the second MOS transistor Q2 is connected to the output terminal of the second operational amplifier U2, and the non-inverting input terminal of the second operational amplifier U2 is connected to the second reference voltage REF2; the drain of the third MOS transistor Q3 is connected to the cathode of the diode D1, the source of the third MOS transistor Q3 is connected to the first end of the second resistor R2 and the inverting input terminal of the third operational amplifier U3, the gate of the third MOS transistor Q3 is connected to the output terminal of the third operational amplifier U3, and the non-inverting input terminal of the third operational amplifier U3 is connected to the third reference voltage REF3.

[0028] Furthermore, in the present application, after the AC voltage is rectified by the rectifier circuit DB1, it is shaped into a steamed bun wave as shown in Figure 2. When the rectified real-time voltage is greater than the conduction voltage on the load branch, the second MOS transistor Q2 on the second conduction branch is turned on. After the conduction, current flows through the resistor R1, making the voltage reference on R1 equal to the second reference voltage REF2. At the same time, because the second reference voltage REF2 is greater than the voltage value of the first reference voltage REF1, the first MOS transistor Q1 of the first conduction branch is turned off. Similarly, due to the current flowing through the second resistor R2, a voltage is generated on the second resistor R2. This voltage is greater than the third reference voltage REF3 of the third conduction branch, and the third MOS transistor Q3 of the third conduction branch is turned off. When the rectified real-time voltage decreases and becomes less than the load branch's conduction voltage, the second MOS transistor Q2 turns off, rendering the second conduction branch inoperable. At this point, because capacitor C1 stores energy, the voltage across capacitor C1 exceeds the load branch's conduction voltage, causing the first MOS transistor Q1 to turn on, taking over operation from the second MOS transistor Q2. Similarly, current flowing through the second resistor R2 generates a voltage across the second resistor R2 that is greater than the third reference voltage REF3 of the third conduction branch, turning off the third MOS transistor Q3 of the third conduction branch. Consequently, the first and second MOS transistors Q1 and Q2 alternately conduct, ensuring continuous current flows through the LEDs on the load branch, ensuring consistent and stable illumination and addressing the issue of flicker. Furthermore, when the second MOS transistor Q2 is on, it draws energy directly from the mains, while when the first MOS transistor Q1 is on, it draws energy from capacitor C1. This allows the capacitance of capacitor C1 to be smaller than that used in the prior art.

[0029] Furthermore, when the input mains voltage drops further, the energy stored in capacitor C1 is consumed, causing the voltage across capacitor C1 to fall below the load branch's conduction voltage. Both the first and second MOS transistors Q1 and Q2 cease operation. At this point, the voltage across resistor R2 decreases. Due to the presence of the third conduction branch, the third MOS transistor Q3 turns on. The first set of LEDs in the load branch no longer operates, reducing the voltage on the LEDs. The mains power maintains the conduction of the second set of LEDs. This allows current to flow through the second set of LEDs in the load branch, even at low voltages, causing the LEDs to emit light. Consequently, when the input voltage drops, the third MOS transistor Q3 turns on, halting operation of some LEDs while allowing the remaining LEDs to conduct normally. This ensures normal lamp illumination and achieves a wide input voltage range.

[0030] FIG2 shows a circuit diagram of a wide-input-voltage, flicker-free LED driver circuit according to another embodiment of the present application. As shown in FIG2 , the third conducting branch 50 further includes a fourth operational amplifier U4 and a fourth MOS transistor Q4. The drain of the fourth MOS transistor Q4 is connected to the anode of the diode D1, the source of the fourth MOS transistor Q4 is connected to the first end of the second resistor R2 and the inverting input of the fourth operational amplifier U4, the gate of the fourth MOS transistor Q4 is connected to the output of the fourth operational amplifier U4, and the non-inverting input of the fourth operational amplifier U4 is connected to a fourth reference voltage REF4.

[0031] When the grid voltage is sufficient, similar to the embodiment shown in FIG1 , the AC voltage is rectified by DB1 and shaped into a steamed bun wave as shown in FIG2 . When the rectified real-time voltage is greater than the conduction voltage on the load branch, the second MOS transistor Q2 on the second conduction branch turns on. After the conduction, current flows through the resistor R1, making the voltage reference on R1 equal to the second reference voltage REF2. At the same time, because the second reference voltage REF2 is slightly greater than the first reference voltage REF1, the first MOS transistor Q1 of the first conduction branch is turned off. Similarly, the current flowing through the second resistor R2 generates a voltage across the second resistor R2. This voltage is greater than the reference voltages REF3 and REF4 of the third conduction branch, turning off the third and fourth MOS transistors Q3 and Q4 of the third conduction branch.

[0032] When the rectified real-time voltage decreases and becomes less than the load branch's conduction voltage, the second MOS transistor Q2 turns off, rendering the second conduction branch inoperable. At this point, due to the stored energy within capacitor C1, the voltage across capacitor C1 exceeds the load branch's conduction voltage, causing the first MOS transistor Q1 to turn on, taking over from the second MOS transistor Q2. This ensures continuous and stable illumination of the LED. Similarly, current flowing through the second resistor R2 generates a voltage across the second resistor R2 that is greater than the reference voltages REF3 and REF4 of the third conduction branch, turning off the third and fourth MOS transistors Q3 and Q4 of the third conduction branch. Consequently, the first and second MOS transistors Q1 and Q2 alternately conduct, ensuring continuous current flows through the LED on the load branch, ensuring continuous and stable illumination and resolving the issue of flicker.

[0033] Furthermore, when the input mains voltage drops further, no current flows through resistor R1, causing the current in resistor R2 to decrease, and the voltage across resistor R2 to drop. When the voltage falls below the reference voltages REF3 and REF4, and because REF4 > REF3, the fourth MOS transistor Q4 turns on. Once Q4 turns on, it draws current directly from the grid, turning on the second set of LED loads. When the real-time grid voltage is insufficient to turn on the second set of LED loads, the energy stored in the capacitors prevents the fourth MOS transistor Q4 from turning on, and the third MOS transistor Q3 continues to turn on, continuing to supply current to the second set of LED loads. This allows the entire circuit to achieve a higher energy supply while using smaller capacitors, enabling a wider input voltage range to ensure consistent LED brightness.

[0034] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0035] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various application aspects, in the above description of the exemplary embodiments of the present application, various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: that the claimed application requires more features than those explicitly recited in each claim. More precisely, as reflected in the claims below, aspects of the present application lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present application.

[0036] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination.

[0037] It should be noted that the above embodiments illustrate rather than limit the present application, and that a person skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbols placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present application may be implemented by means of hardware comprising several different elements and by means of appropriately programmed computers. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

Claims

1. A wide input voltage non-flicker LED driving circuit, characterized in that: The invention comprises a rectifier circuit, an absorption circuit, a first conductive branch, a second conductive branch, a third conductive branch and a load branch, wherein the input end of the rectifier circuit is connected to the AC mains, the output end of the rectifier circuit is connected to the input end of the absorption circuit and the input end of the second conductive branch, the output end of the absorption circuit is connected to the input end of the first conductive branch and the input end of the third conductive branch, and the load branch comprises a first resistor R1, a first group of LED loads, a second resistor R2 and a second group of LEDs connected in series. load, the output end of the first conductive branch and the output end of the second conductive branch are connected to the first end of the first resistor R1, and the output end of the third conductive branch is connected to the first end of the second resistor R2, wherein, when the real-time voltage after rectification by the rectifier circuit is greater than the conduction voltage of the load branch, the second conductive branch is turned on, and the first conductive branch and the third conductive branch are turned off; when the real-time voltage is less than the conduction voltage of the load branch, the first conductive branch is turned on, and the second conductive branch and the third conductive branch are turned off; when the real-time voltage continues to decrease until the first conductive branch and the second conductive branch are both turned off, the third conductive branch is turned on.

2. The wide input voltage flicker-free LED driving circuit according to claim 1, characterized in that: The absorption circuit includes a diode D1 and a capacitor C1, the anode of the diode D1 is connected to the output end of the rectifier circuit and the input end of the second conductive branch, and the cathode of the diode D1 is connected to the first end of the capacitor C1 and the input end of the first conductive branch and the input end of the third conductive branch.

3. The wide input voltage flicker-free LED driving circuit according to claim 2, characterized in that: The first conducting branch includes a first operational amplifier U1 and a first MOS transistor Q1, the drain of the first MOS transistor Q1 is connected to the cathode of the diode D1, the source of the first MOS transistor Q1 is connected to the first end of the first resistor R1 and the inverting input end of the first operational amplifier U1, the gate of the first MOS transistor Q1 is connected to the output end of the first operational amplifier U1, and the non-inverting input end of the first operational amplifier U1 is connected to the first reference voltage REF1.

4. The wide input voltage flicker-free LED driving circuit according to claim 3, characterized in that: The second conducting branch includes a second operational amplifier U2 and a second MOS transistor Q2, the drain of the second MOS transistor Q2 is connected to the anode of the diode D1, the source of the second MOS transistor Q2 is connected to the first end of the first resistor R1 and the inverting input end of the second operational amplifier U2, the gate of the second MOS transistor Q2 is connected to the output end of the second operational amplifier U2, and the non-inverting input end of the second operational amplifier U2 is connected to the second reference voltage REF2.

5. The wide input voltage flicker-free LED driving circuit according to claim 4, characterized in that: The second reference voltage REF2 is greater than the first reference voltage REF1.

6. The wide input voltage flicker-free LED driving circuit according to claim 2, characterized in that: The third conducting branch includes a third operational amplifier U3 and a third MOS tube Q3, the drain of the third MOS tube Q3 is connected to the cathode of the diode D1, the source of the third MOS tube Q3 is connected to the first end of the second resistor R2 and the inverting input end of the third operational amplifier U3, the gate of the third MOS tube Q3 is connected to the output end of the third operational amplifier U3, and the non-inverting input end of the third operational amplifier U3 is connected to the third reference voltage REF3.

7. The wide input voltage flicker-free LED driving circuit according to claim 6, characterized in that: The third conducting branch further includes a fourth operational amplifier U4 and a fourth MOS tube Q4, the drain of the fourth MOS tube Q4 is connected to the anode of the diode D1, the source of the fourth MOS tube Q4 is connected to the first end of the second resistor R2 and the inverting input end of the fourth operational amplifier U4, the gate of the fourth MOS tube Q4 is connected to the output end of the fourth operational amplifier U4, and the non-inverting input end of the fourth operational amplifier U4 is connected to the fourth reference voltage REF4.

8. The wide input voltage flicker-free LED driving circuit according to claim 7, characterized in that: The fourth reference voltage REF4 is greater than the third reference voltage REF3.

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