LED driving circuit and control method thereof

Abstract

The invention provides an LED driving circuit and a control method thereof.According to the LED driving circuit, a control circuit controls commercial power to charge a first energy storage unit to a charging threshold value, the charging threshold value is determined by the commercial power or the voltage of a second energy storage unit, on one hand, when the voltage of the second energy storage unit is too high, the energy conversion efficiency of the circuit is low, and on the other hand, the energy conversion efficiency of the circuit is low; the charging threshold of the first energy storage unit can be reduced, so that the energy provided by the mains supply and the first energy storage unit to the load branch and the second energy storage unit is reduced in the negative half cycle of the mains supply, and the energy conversion efficiency of the circuit is improved; and on the second aspect, when the voltage of the second energy storage unit is relatively low and the energy is insufficient, the charging threshold of the first energy storage unit can be improved, so that the commercial power and the first energy storage unit can be ensured to provide enough energy to the load branch and the second energy storage unit in the negative half cycle of the commercial power, and the current flowing through the load branch is ensured to be stable.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to an LED drive circuit and a control method thereof. Background Art

[0002] LED (Light-Emitting Diode) lighting is widely used in furniture, office, outdoor lighting and stage lighting. Dimming technology can make the brightness of LED loads adjustable, thereby expanding the application scenarios and practical experience of LED lighting. In recent years, with the progress of society, higher requirements have been placed on LED lighting, requiring high PF (Power Factor), no flicker, and high efficiency, so as to reduce damage to human eyes and improve energy utilization.

[0003] In the field of LED lighting, energy conversion efficiency is an important indicator. In traditional LED linear dimming solutions, a large amount of energy is lost in the power tube. Therefore, how to reduce the loss of the power tube and thus improve the energy conversion efficiency of LED dimming is a problem that needs to be solved urgently. Summary of the invention

[0004] The object of the present invention is to provide an LED driving circuit and a control method thereof, so as to solve the problem of how to reduce the energy loss of the driving circuit and thus improve the energy conversion efficiency of LED dimming.

[0005] To solve the above technical problems, based on one aspect of the present invention, the present invention provides an LED driving circuit for driving a load branch, comprising:

[0006] A rectifier bridge, used for receiving the mains power and outputting the rectified mains power at an output port of the rectifier bridge, wherein the load branch is connected to the output port;

[0007] A first energy storage unit connected to the input end of the rectifier bridge;

[0008] a second energy storage unit connected in parallel with the load branch;

[0009] The control circuit is configured to control the mains to charge the first energy storage unit to a charging threshold, wherein the charging threshold is determined by the voltage of the mains or the second energy storage unit.

[0010] Optionally, the magnitude of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage slope of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage of the second energy storage unit is inversely correlated with the charging threshold.

[0011] Optionally, in the positive half cycle of the mains, the control circuit is configured to control the mains to charge the first energy storage unit to the charging threshold, and when the voltage of the mains is greater than the voltage of the second energy storage unit, the mains supplies power to the load branch and charges the second energy storage unit; and

[0012] In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit is greater than the voltage of the second energy storage unit, the mains and the first energy storage unit supply power to the load branch and charge the second energy storage unit.

[0013] Optionally, in the positive half cycle of the mains, when the voltage of the mains is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch; and

[0014] In the negative half cycle of the mains power, when the sum of the voltage of the mains power and the voltage of the first energy storage unit is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch.

[0015] Optionally, the control circuit is configured to generate a first reference voltage according to the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit;

[0016] In the positive half cycle of the AC power, the control circuit controls the AC power to charge the first energy storage unit when the first voltage sampling signal representing the voltage of the first energy storage unit is less than a first reference voltage, and the control circuit controls the AC power to stop charging the first energy storage unit when the first voltage sampling signal reaches the first reference voltage, so that the first energy storage unit is charged to the charging threshold.

[0017] Optionally, the control circuit includes a voltage detection unit, a voltage adjustment unit, a comparator and a first power switch;

[0018] The voltage detection unit generates the first voltage sampling signal according to the voltage of the first energy storage unit;

[0019] The voltage adjustment unit generates the first reference voltage according to the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit;

[0020] The first input terminal of the comparator receives the first voltage sampling signal, the second input terminal of the comparator receives the first reference voltage, and the output terminal of the comparator is connected to the control terminal of the first power switch;

[0021] A branch formed by the first energy storage unit and the first power switch being connected in series is connected between the input end of the rectifier bridge and the ground.

[0022] Optionally, in the positive half cycle of the mains power, the comparator controls the first power switch to turn on when the first voltage sampling signal is less than the first reference voltage, so that the mains power charges the first energy storage unit; and the comparator controls the first power switch to turn off when the first voltage sampling signal reaches the first reference voltage, so that the mains power stops charging the first energy storage unit;

[0023] In the negative half cycle of the AC power, the first power switch is turned on, so that the first energy storage unit is discharged.

[0024] Optionally, the voltage detection unit includes a first resistor and a second resistor, the first end of the first resistor is connected to the first end of the first energy storage unit, the second end of the first resistor is grounded through the second resistor, and the second end of the first resistor is connected to the first input end of the comparator.

[0025] Optionally, the voltage adjustment unit includes a detection unit and a reference voltage generating unit; the detection unit is used to provide a second voltage sampling signal based on the voltage of the AC power, the voltage slope of the AC power, or the voltage of the second energy storage unit; the reference voltage generating unit generates the first reference voltage based on the second voltage sampling signal.

[0026] Optionally, the reference voltage generating unit calculates and obtains the first reference voltage based on the following formula:

[0027] Vref1=V0-k*Vd, wherein Vref1 is the first reference voltage, V0 is a preset fixed voltage, Vd is the second voltage sampling signal, and k is a coefficient.

[0028] Optionally, the detection unit includes a third resistor and a fourth resistor;

[0029] The first end of the third resistor is connected to the second energy storage unit or the load branch or the input end of the rectifier bridge, the second end of the third resistor is grounded through a fourth resistor, and the second end of the third resistor is connected to the reference voltage generating unit to provide the second voltage sampling signal.

[0030] Optionally, the voltage adjustment unit further includes a filter capacitor, and the filter capacitor is connected in parallel with the fourth resistor.

[0031] Optionally, the load branch includes a load and a constant current control circuit connected to each other;

[0032] The constant current control circuit includes a second power switch, an operational amplifier and a fifth resistor. The first end of the second power switch is connected to the first end of the constant current control circuit. The first input end of the operational amplifier is connected to a second reference voltage. The second input end of the operational amplifier is connected to the second end of the second power switch and then to the second end of the constant current control circuit through the fifth resistor. The output end of the operational amplifier is connected to the control end of the second power switch.

[0033] To solve the above technical problems, based on another aspect of the present invention, the present invention further provides a control method of an LED driving circuit, which is used to drive a load branch. The LED driving circuit includes a rectifier bridge, a load branch, a first energy storage unit and a second energy storage unit. The rectifier bridge rectifies the mains power and outputs it at its own output port. The load branch is connected to the output port. The first energy storage unit is connected to the input end of the rectifier bridge. The second energy storage unit is connected in parallel with the load branch. The control method includes:

[0034] The mains power is controlled to charge the first energy storage unit to a charging threshold, wherein the charging threshold is determined by the voltage of the mains power or the second energy storage unit.

[0035] Optionally, the magnitude of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage slope of the mains power is inversely correlated with the charging threshold, or the voltage of the second energy storage unit is inversely correlated with the charging threshold.

[0036] Optionally, in the positive half cycle of the mains, the mains is controlled to charge the first energy storage unit to the charging threshold, and when the voltage of the mains is greater than the voltage of the second energy storage unit, the mains supplies power to the load branch and charges the second energy storage unit; and

[0037] In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit is greater than the voltage of the second energy storage unit, the mains and the first energy storage unit supply power to the load branch and charge the second energy storage unit.

[0038] Optionally, in the positive half cycle of the mains, when the voltage of the mains is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch; and

[0039] In the negative half cycle of the mains power, when the sum of the voltage of the mains power and the voltage of the first energy storage unit is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch.

[0040] Optionally, in the positive half cycle of the mains, when a first voltage sampling signal representing the voltage of the first energy storage unit is less than a first reference voltage, the mains is controlled to charge the first energy storage unit, and when the first voltage sampling signal reaches the first reference voltage, the mains is controlled to stop charging the first energy storage unit, so that the first energy storage unit is charged to the charging threshold;

[0041] The first reference voltage is generated based on the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

[0042] Optionally, the first reference voltage is obtained based on the following formula:

[0043] Vref1=V0-k*Vd, wherein Vref1 is the first reference voltage, V0 is a preset fixed voltage, Vd is a second voltage sampling signal, and k is a coefficient;

[0044] The second voltage sampling signal represents the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

[0045] In summary, in the LED driving circuit provided by the present invention, the charging threshold of the first energy storage unit is controlled by the control circuit based on the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit, that is, the maximum voltage on the first energy storage unit is adjusted, so that the first energy storage unit is controlled to be charged by the mains in the positive half cycle of the mains, and the first energy storage unit is controlled to stop being charged when the voltage of the first energy storage unit reaches the charging threshold, and the first energy storage unit is controlled to discharge in the negative half cycle of the mains to supply power to the load branch and charge the second energy storage unit. In this way, on the first hand, when the voltage of the second energy storage unit is too high, the energy conversion efficiency of the circuit is low, the charging threshold of the first energy storage unit can be reduced, and the charging threshold can even be reduced to 0V, thereby reducing the energy provided by the AC power and the first energy storage unit to the load branch and the second energy storage unit in the negative half cycle of the AC power, thereby improving the energy conversion efficiency of the circuit; on the second hand, when the voltage of the second energy storage unit is low and the energy is insufficient, the charging threshold of the first energy storage unit can be increased, thereby ensuring that the first energy storage unit provides sufficient energy to the load branch and the second energy storage unit in the negative half cycle of the AC power, thereby ensuring the stability of the current flowing through the load branch.

[0046] It should be noted that the control method of the LED driving circuit and the LED driving circuit of the present invention are based on the same inventive concept and have the same or corresponding specific technical features, and therefore also have the technical effects of the LED driving circuit, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Those skilled in the art should understand that the drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0048] Figure 1 is a schematic diagram of an LED driving circuit according to an embodiment of the present invention;

[0049] Figure 2 is a waveform diagram of the voltage of the mains, the voltage of the first energy storage unit, the voltage of the second energy storage unit, and the current flowing through the load according to an embodiment of the present invention;

[0050] Figure 3 is another schematic diagram of an LED driving circuit according to an embodiment of the present invention;

[0051] Figure 4 FIG. 4 is another schematic diagram of an LED driving circuit according to an embodiment of the present invention.

[0052] In the attached figure:

[0053] 10-rectifier bridge; 20-constant current control circuit; 30-control circuit; 31-reference voltage generating unit; 40-load;

[0054] C1-first energy storage unit; C2-second energy storage unit; C3-filter capacitor; R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; Q1-first power switch; Q2-second power switch; D1-first voltage regulator diode; D2-second voltage regulator diode; U1-comparator; U2-op amp. DETAILED DESCRIPTION

[0055] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0056] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "the proximal end" and "the distal end" generally refer to two corresponding parts, which include not only the endpoints, and the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. In addition, as used in the present invention, an element disposed on another element generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements may be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element may be in any orientation such as inside, outside, above, below or on one side of another element, unless otherwise clearly indicated in the content. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] See also Figure 1 An embodiment of the present invention schematically provides an LED driving circuit for driving a load branch, wherein the load branch includes a load 40 and a constant current control circuit 20 connected to each other, and the LED driving circuit includes a rectifier bridge 10, a first energy storage unit C1, a second energy storage unit C2, and a control circuit 30. The input end of the rectifier bridge 10 is used to connect to the mains power VAC, thereby rectifying the mains power and outputting a DC voltage at its output port, see Figure 1, the DC voltage output by the rectifier bridge 10 after rectifying the AC power VAC is Vin. The load branch is connected to the output port of the rectifier bridge 10, and the second energy storage unit C2 is connected to the output port of the rectifier bridge 10. The load branch is connected in parallel with the second energy storage unit C2. Specifically, the first end of the load branch and the first end of the second energy storage unit C2 are both connected to the first output end of the rectifier bridge 10 (here it can be the positive output end of the rectifier bridge 10), and the second end of the load branch and the second end of the second energy storage unit C2 are both connected to the second output end of the rectifier bridge 10. The second output end of the rectifier bridge 10 is grounded. The load 40 here is also an LED (Light-Emitting Diode), in which LEDs with different lamp voltages can be selected according to requirements in different application scenarios. The first end of the first energy storage unit C1 is connected to the input end of the rectifier bridge 10, and the second end of the first energy storage unit C1 is connected to the control circuit 30. The control circuit 30 can be connected to the input end of the rectifier bridge 10 or to the second energy storage unit C2. The control circuit 30 can detect the voltage of the mains, or the voltage slope of the mains, or the voltage of the second energy storage unit C2, and can control the mains to charge the first energy storage unit C1 to a charging threshold in the positive half cycle of the mains, wherein the charging threshold of the first energy storage unit C1 is a variable value, which is determined by the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit C2. In other words, the control circuit 30 determines the charging threshold of the first energy storage unit C1 based on the voltage of the mains or the voltage slope, or the voltage of the second energy storage unit C2. It should be noted that the charging threshold of the first energy storage unit C1 can be calculated based on the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit C2.

[0058] In some embodiments, the magnitude of the AC power VAC is inversely correlated with the charging threshold, or the magnitude of the voltage slope of the AC power VAC is inversely correlated with the charging threshold, or the magnitude of the voltage of the second energy storage unit C2 is inversely correlated with the charging threshold.

[0059] In some embodiments, in the positive half cycle of the mains power VAC, when the mains power (specifically the DC voltage Vin output by the rectifier bridge 10) is greater than the voltage of the second energy storage unit C2, the mains power VAC (specifically the DC voltage Vin) supplies power to the load 40 in the load branch and charges the second energy storage unit C2; when the mains power (specifically the DC voltage Vin) is less than or equal to the voltage of the second energy storage unit C2, the second energy storage unit C2 supplies power to the load branch; in the negative half cycle of the mains power VAC, when the sum of the voltage of the mains power VAC (specifically the DC voltage Vin) and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the mains power VAC and the first energy storage unit C1 supply power to the load branch and charge the second energy storage unit C2; when the sum of the voltage of the mains power VAC (specifically the DC voltage Vin) and the voltage of the first energy storage unit C1 is less than or equal to the voltage of the second energy storage unit C2, the second energy storage unit C2 supplies power to the load branch. The first energy storage unit C1 and the second energy storage unit C2 are, for example, energy storage capacitors, or other energy storage circuits. The current of the constant current control circuit 20 remains stable within a certain range and does not change with the load 40, thereby limiting the current flowing through the load 40 and ensuring the current stability of the load 40. In addition, the second energy storage unit C2 is also used to supply power to the constant current control circuit 20 to ensure the normal startup and operation of the constant current control circuit 20, or the DC voltage output by the rectifier bridge 10 supplies power to the constant current control circuit 20. In this embodiment, the control circuit 30 determines the charging threshold of the first energy storage unit C1 according to the voltage or voltage slope of the mains VAC, or the voltage of the second energy storage unit C2, so that the voltage of the first energy storage unit C1 (referring to the maximum voltage reached by the first energy storage unit C1 when charged under the corresponding mains) is moderate, such as slightly lower than the peak voltage of the mains, which improves the efficiency of the drive circuit on the one hand, and ensures the stability of the current flowing through the load 40 on the other hand.

[0060] See also Figure 2 , wherein AC represents the voltage waveform of the mains, V-C1 represents the voltage waveform of the first energy storage unit C1, V-C2 represents the voltage waveform of the second energy storage unit C2, and I-LED represents the current waveform flowing through the load 40. It should be noted that the same type of lines in the figure represent the voltage of the first energy storage unit C1, the voltage of the second energy storage unit C2, and the current flowing through the load 40 under the mains voltage level. In this embodiment, the rated voltage of the mains is 230V, and the effective value limit range is ±10%. For example, the X line represents a voltage waveform with an effective value of 253V for the mains voltage, the Y line represents a voltage waveform with an effective value of 230V for the mains voltage, and the Z line represents a voltage waveform with an effective value of 207V for the mains voltage. Continue to refer to Figure 2, during the positive half cycle of the mains and the voltage of the mains is from 0V to the voltage peak, the greater the effective value of the mains voltage, the greater its slope, for example, the voltage slope of the mains represented by the X line is greater than the voltage slope of the mains represented by the Y line, which is greater than the voltage slope of the mains represented by the Z line. Further, the voltage of the mains is inversely correlated with the charging threshold of the first energy storage unit C1, or the voltage of the second energy storage unit C2 is inversely correlated with the charging threshold, the smaller the voltage of the mains, or the smaller the voltage slope of the mains, or the smaller the voltage of the second energy storage unit C2, the greater the charging threshold of the first energy storage unit C1. Specifically, among the effective values ​​of the mains voltage represented by the X line, the Y line and the Z line, the effective value of the mains voltage represented by the Z line is the smallest, the voltage slope is the smallest during the positive half cycle of the mains and the voltage is from 0V to the voltage peak, the voltage waveform of the second energy storage unit C2 represented by V-C2, which is the same type as the Z line, has the smallest voltage, and the voltage waveform of the first energy storage unit C1 represented by V-C1, which is the same type as the Z line, has the largest voltage; the effective value of the mains voltage represented by the X line is the largest, and at this time the charging threshold of the first energy storage unit C1 is the smallest, such as 0V.

[0061] Further, the control concept of the control circuit 30 of the present embodiment is that in the positive half cycle of the mains, the control circuit 30 is configured to control the mains to charge the first energy storage unit C1 to the charging threshold, and when the voltage of the mains is greater than the voltage of the second energy storage unit C2, the rectified mains supplies power to the load branch and charges the second energy storage unit C2. In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the rectified mains and the first energy storage unit C1 supply power to the load branch and charge the second energy storage unit. In the positive half cycle of the mains, when the voltage of the mains is less than or equal to the voltage of the second energy storage unit C2, the second energy storage unit C2 supplies power to the load branch. In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit C1 is less than or equal to the voltage of the second energy storage unit C2, the second energy storage unit C2 supplies power to the load branch.

[0062] See also Figure 2As an example, in a cycle of the mains, in the positive half cycle, the control circuit 30 controls the mains to charge the first energy storage unit C1, so that the voltage of the first energy storage unit C1 increases until the voltage of the first energy storage unit C1 is charged to the charging threshold (that is, the charging threshold is the maximum voltage reached by the first energy storage unit C1 under the corresponding mains). As the voltage of the mains gradually increases, the second energy storage unit C2 discharges to supply power to the load 40, so that the voltage of the second energy storage unit C2 decreases linearly. In the process of the mains gradually increasing and the voltage of the second energy storage unit C2 decreasing linearly, the voltage of the second energy storage unit C2 is always greater than the voltage of the mains. When the mains increases and the voltage of the second energy storage unit C2 decreases until the two are equal, the mains then supplies power to the load 40 and charges the second energy storage unit C2. In the negative half cycle of the mains, the first energy storage unit C1 discharges, so that the discharged energy and the energy of the mains are rectified by the rectifier bridge 10 and output to the load 40, and the second energy storage unit C2 is charged by the voltage output by the rectifier bridge 10. The charge and discharge time of the second energy storage unit C2 depends on the voltage of the mains in the positive half cycle or the voltage of the mains in the negative half cycle and the voltage of the first energy storage unit C1. It is understandable that when the mains (which may refer to the voltage of the mains or the voltage slope of the mains) is small or the voltage on the second energy storage unit C2 is small, the charging threshold of the first energy storage unit C1 is large, and the charge and discharge time of the second energy storage unit C2 is long, such as shown by the Z line type; when the mains is large or the voltage on the second energy storage unit C2 is large, the charging threshold of the first energy storage unit C1 is small, and can even be 0, and the charge and discharge time of the second energy storage unit C2 is short, such as shown by the X line type.

[0063] It is particularly important to note that when the mains power is large or the voltage on the second energy storage unit C2 is large, the charging threshold of the first energy storage unit can be 0V, and the control circuit 30 will not control the mains power to charge the first energy storage unit C1, and the first energy storage unit C1 is in a state of no energy storage, such as the voltage waveform of the first energy storage unit C1 under the mains power of the voltage effective value represented by the X line type in the figure. In addition, it can be understood that the lower the effective value of the mains voltage or the smaller the voltage slope of the mains or the smaller the voltage on the second energy storage unit C2, the larger the charging threshold of the first energy storage unit C1, the higher the effective value of the mains voltage or the larger the voltage slope of the mains or the larger the voltage on the second energy storage unit C2, the smaller the charging threshold of the first energy storage unit C1, or the first energy storage unit C1 is in a state of no energy storage. The charging threshold of the first energy storage unit C1 is determined according to the voltage of the AC power or the voltage slope of the AC power or the voltage on the second energy storage unit C2, which helps to control the voltage of the second energy storage unit C2 so that it is neither too high nor too low, thereby improving the efficiency of the drive circuit and ensuring the stability of the current flowing through the resistor 40.

[0064] In this way, the charging threshold of the first energy storage unit C1 is determined by the control circuit 30 based on the voltage of the mains or the voltage slope of the mains or the voltage of the second energy storage unit C2, that is, the maximum voltage that the first energy storage unit C1 can store under different mains is adjusted, so that it can be ensured that when the voltage of the first energy storage unit C1 is less than the charging threshold, the first energy storage unit C1 is controlled to be charged by the mains, and when the voltage of the first energy storage unit C1 reaches the charging threshold, the first energy storage unit C1 is controlled to stop being charged, and the first energy storage unit C1 is discharged when the sum of the voltage of the mains and the voltage of the first storage unit C1 is greater than the voltage of the second energy storage unit C2 in the negative half cycle of the mains, and the discharged energy and the energy of the mains are rectified by the rectifier bridge 10 to supply power to the load 40 and charge the second energy storage unit C2. In this way, on the first hand, when the voltage of the second energy storage unit C2 is too high, the circuit energy conversion efficiency is low, and the charging threshold of the first energy storage unit C1 can be reduced, thereby reducing the voltage of the second energy storage unit C2 and improving the circuit energy conversion efficiency; on the second hand, when the voltage of the second energy storage unit C2 is too small, it means that the voltage of the second energy storage unit is low and the energy is insufficient, then the charging threshold of the first energy storage unit C1 can be increased, thereby increasing the voltage of the second energy storage unit C2 to ensure that the current flowing through the load 40 is stable.

[0065] Based on the above control concept, the control circuit 30 is configured to generate a first reference voltage according to the voltage of the mains, the voltage slope of the mains (such as the rising slope of the voltage) or the voltage of the second energy storage unit C2. In the positive half cycle of the mains, the control circuit 30 controls the mains to charge the first energy storage unit C1 when the first voltage sampling signal representing the voltage of the first energy storage unit C1 is less than the first reference voltage, and the control circuit 30 controls the mains to stop charging the first energy storage unit C1 when the first voltage sampling signal reaches the first reference voltage, at which time the voltage of the first energy storage unit C1 reaches the charging threshold, wherein the charging threshold can be calculated based on the first reference voltage. In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the first energy storage unit C1 is discharged, so that the discharged energy and the energy of the mains are rectified by the rectifier bridge 10 and output to the load branch and the second energy storage unit C2, thereby supplying power to the load branch and charging the second energy storage unit C2.

[0066] In one embodiment, continue to refer to Figure 1The control circuit 30 includes a voltage detection unit, a voltage adjustment unit 31, a comparator U1 and a first power switch Q1. The voltage detection unit detects the voltage of the first energy storage unit C1 to generate a first voltage sampling signal, and the voltage adjustment unit 31 generates a first reference voltage Vref1 according to the voltage of the mains, the voltage slope of the mains or the voltage of the second energy storage unit. The first input terminal (such as the inverting input terminal) of the comparator U1 receives the first voltage sampling signal, the second input terminal (such as the non-inverting input terminal) of the comparator U1 receives the first reference voltage Vref1, and the output terminal of the comparator U1 is connected to the control terminal of the first power switch Q1, so as to output the comparison result of the first voltage sampling signal and the first reference voltage Vref1 to the control terminal of the first power switch Q1 to control the on and off of the first power switch Q1. The branch formed by the first energy storage unit C1 and the first power switch Q1 connected in series is connected between the input end of the rectifier bridge 10 and the ground. Exemplarily, the first end of the first energy storage unit C1 is connected to the input end of the rectifier bridge 10, the second end of the first energy storage unit C1 is connected to the first end of the first power switch Q1, and the second end of the first power switch Q1 is grounded.

[0067] It is understandable that in the positive half cycle of the mains, when the first power switch Q1 is turned on, the rectifier bridge 10, the first energy storage unit C1 and the first power switch Q1 form a charging loop, thereby charging the first energy storage unit C1, and when the first power switch Q1 is turned off, the mains stops charging the first energy storage unit C1. Specifically, in the positive half cycle of the mains, when the first voltage sampling signal is less than the first reference voltage Vref1, the comparator U1 controls the first power switch Q1 to turn on, and when the first voltage sampling signal reaches the first reference voltage Vref1, the first power switch Q1 is turned off, and at this time, the voltage of the first energy storage unit C1 reaches the charging threshold, which is calculated by Vref1 and the first voltage sampling signal provided by the voltage detection unit. In the negative half cycle of the mains, when the first power switch Q1 is turned on and the sum of the voltage of the mains and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the first energy storage unit C1, the rectifier bridge 10 and the load branch form a discharge loop, and the first energy storage unit C1, the rectifier bridge 10 and the second energy storage unit C2 form a charging loop, so that the first energy storage unit C1 discharges to the load 40 and charges the second energy storage unit C2. Specifically, in the negative half cycle of the mains, the baseband of the first power switch Q1 is on, so when the sum of the voltage of the mains and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the first energy storage unit C1, the rectifier bridge 10 and the load branch form a discharge loop, and the first energy storage unit C1, the rectifier bridge 10 and the second energy storage unit C2 form a charging loop. In some embodiments, in the negative half cycle of the AC power, the voltage of the first energy storage unit C1 decreases, so that the first voltage sampling signal is less than the first reference voltage Vref1, thereby controlling the first power switch Q1 to turn on, so that when the sum of the voltage of the AC power and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the first energy storage unit C1, the rectifier bridge 10 and the load branch form a discharge circuit, and the first energy storage unit C1, the rectifier bridge 10 and the second energy storage unit C2 form a charging circuit.

[0068] The comparator U1 outputs a driving signal according to the comparison result between the first voltage sampling signal and the first reference voltage Vref1, and the first power switch Q1 is controlled to be turned on and off by the driving signal. Specifically, in the positive half cycle of the mains, when the first voltage sampling signal is less than the first reference voltage Vref1, the driving signal (at this time, for example, a high level) controls the first power switch Q1 to be turned on, so that the mains charges the first energy storage unit C1. When the first voltage sampling signal reaches the first reference voltage Vref1, the driving signal (at this time, for example, a low level) controls the first power switch Q1 to be turned off, so that the mains stops charging the first energy storage unit C1. At this time, the voltage of the first energy storage unit C1 reaches the charging threshold. In the negative half cycle of the AC power, when the first voltage sampling signal is less than the first reference voltage Vref1, the driving signal controls the first power switch Q1 to turn on, so that when the sum of the voltage of the AC power and the voltage of the first energy storage unit C1 is greater than the voltage of the second energy storage unit C2, the first energy storage unit C1 discharges and the voltage of the first energy storage unit C1 and the voltage of the AC power are rectified by the rectifier bridge 10 to supply power to the load 40 and charge the second energy storage unit C2.

[0069] As an example, the first power switch Q1 is an NMOS tube, the first end of the first power switch Q1 is a drain, the second end is a source, and the control end is a gate. In another example, the first power switch Q1 is an NPN transistor, the first end of the first power switch Q1 is a collector, the second end is an emitter, and the control end is a base.

[0070] Continue reading Figure 1 , the voltage detection unit includes a first resistor R1 and a second resistor R2, the first end of the first resistor R1 is connected to the first end of the first energy storage unit C1, the second end of the first resistor R1 is grounded through the second resistor R2, and the second end of the first resistor R1 is connected to the first input end of the comparator U1. In this way, the voltage of the first energy storage unit C1 is sampled by the voltage division of the first resistor R1 and the second resistor R2, thereby generating a first voltage sampling signal. It can be understood that the first voltage sampling signal is VC1×R2 / (R1+R2). When the first voltage sampling signal reaches the first reference voltage Vref1, the voltage of the first energy storage unit C1 is charged to the charging threshold, so the charging threshold is equal to Vref1×(R1+R2) / R2, where VC1 is the voltage of the first energy storage unit C1, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor.

[0071] The voltage adjustment unit includes a detection unit and a reference voltage generating unit 31. The detection unit provides a second voltage sampling signal Vd to the reference voltage generating unit 31, so that the reference voltage generating unit 31 generates a first reference voltage Vref1 according to the second voltage sampling signal Vd. Among them, the detection unit provides the second voltage sampling signal Vd in the following three ways: the detection unit is used to provide the second voltage sampling signal Vd according to the voltage of the mains; the detection unit is used to provide the second voltage sampling signal Vd according to the voltage slope of the mains; the detection unit is used to provide the second voltage sampling signal according to the voltage of the second energy storage unit Vd. Specifically, the detection unit can be connected to the input end of the rectifier bridge 10 to provide the second voltage sampling signal according to the voltage of the mains or the voltage slope of the mains; the detection unit can also be connected to the end of the second energy storage capacitor C2 connected to the rectifier bridge 10 or connected to the load branch to provide the second voltage sampling signal according to the voltage of the second energy storage unit C2.

[0072] Further, the reference voltage generating unit 31 calculates the first reference voltage Vref1 based on the following formula: Vref1 = V0-k*Vd, wherein V0 is a preset fixed voltage, Vd is the second voltage sampling signal, and k is a coefficient. It can be understood that Vd is in a dynamic change process, and Vref1 changes in a negative correlation with Vd.

[0073] The detection unit includes a third resistor R3 and a fourth resistor R4, a first end of the third resistor R3 is connected to the second energy storage unit C2, the load branch or the input end of the rectifier bridge 10, a second end of the third resistor R3 is grounded through the fourth resistor R4, and a second end of the third resistor R3 is connected to the reference voltage generating unit 31 to provide a second voltage sampling signal Vd. As an example, the first end of the third resistor R3 is connected to the connection point between the load 40 and the constant current control circuit 20, and the second end of the third resistor R3 is connected to the reference voltage generating unit 31. Specifically, the first end of the third resistor R3 is connected to the second energy storage unit C2, and the second end of the third resistor R3 provides a second voltage sampling signal according to the voltage of the second energy storage unit C2; the first end of the third resistor R3 is connected to the connection point between the load 40 and the constant current control circuit 20, and the second end of the third resistor R3 provides a second voltage sampling signal according to the voltage difference between the voltage of the second energy storage unit C2 and the load 40. Since the voltage of the load 40 is a constant value under certain applications, the voltage difference can reflect the voltage of the second energy storage unit C2; the first end of the third resistor R3 is connected to the input end of the rectifier bridge, and the second end of the third resistor R3 provides a second voltage sampling signal according to the voltage of the AC power or the voltage slope of the AC power.

[0074] The detection unit may also be other circuits as long as it can detect the mains voltage, the voltage of the second energy storage unit C2 and the voltage at the connection point between the load 40 and the constant current control circuit 20 .

[0075] The detection unit is connected to the input end of the rectifier bridge 10, and is used to collect two voltage signals within a predetermined time from 0° to 90° of the mains phase, and calculate the voltage slope of the mains according to the two voltage signals and the predetermined time, and provide a second voltage sampling signal according to the voltage slope of the mains. The specific circuit of the detection unit is not limited, as long as the detection circuit can realize the voltage slope detection of the rising mains.

[0076] Preferably, the voltage adjustment unit further includes a filter capacitor C3, which is connected in parallel with the fourth resistor R4. After filtering by the filter capacitor C3, the average value of the sampled voltage is used as the second voltage sampling signal Vd.

[0077] Preferably, the control circuit 30 further includes a first zener diode D1 and a second zener diode D2. The first zener diode D1 is reversely connected between the first resistor R1 and the ground, that is, the cathode of the first zener diode D1 is connected to the connection point between the first resistor R1 and the second resistor R2, and the anode of the first zener diode D1 is grounded. The second zener diode D2 is reversely connected between the third resistor R3 and the ground, that is, the cathode of the second zener diode D2 is connected to the second end of the third resistor R3, and the anode of the second zener diode D2 is grounded.

[0078] It should be noted that in the load branch, refer to Figure 1 and Figure 3 The first end of the load 40 (the anode of the light emitting diode) is used as the first end of the load branch to be connected to the positive output end of the rectifier bridge 10, the second end of the load 40 (the cathode of the light emitting diode) is connected to the first end of the constant current control circuit 20, and the second end of the constant current control circuit 20 is used as the second end of the load branch; see Figure 4 Alternatively, the first end of the constant current control circuit 20 serves as the first end of the load branch to be connected to the positive output end of the rectifier bridge 10, the second end of the constant current control circuit 20 is connected to the first end of the load 40 (the anode of the light-emitting diode), and the second end (cathode) of the load 40 serves as the second end of the load branch.

[0079] As an example, the constant current control circuit 20 includes an operational amplifier U2 (operational amplifier), a second power switch Q2 and a fifth resistor R5, the first input terminal (such as the in-phase input terminal) of the operational amplifier U2 is connected to the second reference voltage Vref2, the second input terminal (such as the inverting input terminal) of the operational amplifier U2 is grounded through the fifth resistor R5, the output terminal of the operational amplifier U2 is connected to the control terminal of the second power switch Q2, the first terminal of the load 40 is connected to the positive output terminal of the rectifier bridge 10, the first terminal of the second power switch Q2 is connected to the second terminal of the load 40, and the second terminal of the second power switch Q2 is grounded through the fifth resistor R5. In this way, the input voltage signal (the second reference voltage Vref2) is converted into a current signal through the operational amplifier U2, and the converted current signal is equivalent to a simple constant current source with adjustable output, and the current is the quotient of the reference voltage Vref2 and the fifth resistor R5. In some embodiments, the detection unit is connected to the first end of the second power switch Q2, and is used to detect the voltage of the first end of the second power switch Q2. The voltage of the first end of the second power switch Q2 is the difference between the voltage of the second energy storage unit C2 and the voltage of the load 40. In specific applications, the voltage of the load 40 is fixed, so the voltage of the first end of the second power switch Q2 reflects the voltage of the second energy storage unit C2.

[0080] See also Figure 4 The first end of the second power switch Q2 is connected to the output port of the rectifier bridge 10, the second end of the second power switch Q2 is connected to the first end of the load 40 through the fifth resistor R5, the second end of the load 40 is grounded, and the second end of the load 40 is grounded. The current is the quotient of the second reference voltage Vref2 and R5.

[0081] In one embodiment, the second power switch Q2 is an NMOS tube, the drain terminal of the second power switch Q2 is the drain, the source terminal is the source, and the gate terminal is the gate. In another example, the second power switch Q2 is an NPN transistor, the drain terminal of the second power switch Q2 is the collector, the source terminal is the emitter, and the gate terminal is the base.

[0082] Based on the same inventive concept as the above-mentioned LED driving circuit, an embodiment of the present invention further provides a control method, which is applied to the LED driving circuit. The LED driving circuit includes a rectifier bridge, a load branch, a first energy storage unit and a second energy storage unit. The rectifier bridge rectifies the mains power and outputs it at its own output port. The load branch is connected to the output port. The first energy storage unit is connected to the input end of the rectifier bridge. The second energy storage unit is connected in parallel with the load branch. The control method includes:

[0083] The mains power is controlled to charge the first energy storage unit to a charging threshold, wherein the charging threshold is determined by the voltage of the mains power or the second energy storage unit.

[0084] Further, the magnitude of the mains voltage is inversely correlated with the charging threshold, or the magnitude of the mains voltage slope is inversely correlated with the charging threshold, or the magnitude of the voltage of the second energy storage unit is inversely correlated with the charging threshold.

[0085] Further, in the positive half cycle of the mains, the mains is controlled to charge the first energy storage unit to the charging threshold, and when the voltage of the mains is greater than the voltage of the second energy storage unit, the mains is controlled to supply power to the load branch and charge the second energy storage unit; and

[0086] In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit is greater than the voltage of the second energy storage unit, the mains and the first energy storage unit supply power to the load branch and charge the second energy storage unit.

[0087] Further, in the positive half cycle of the mains, when the voltage of the mains is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch; and

[0088] In the negative half cycle of the mains power, when the sum of the voltage of the mains power and the voltage of the first energy storage unit is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch.

[0089] Further, in the positive half cycle of the mains, when the first voltage sampling signal representing the voltage of the first energy storage unit is less than the first reference voltage, the mains is controlled to charge the first energy storage unit, and when the first voltage sampling signal reaches the first reference voltage, the mains is controlled to stop charging the first energy storage unit, so that the first energy storage unit is charged to the charging threshold;

[0090] The first reference voltage is generated based on the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

[0091] Furthermore, the first reference voltage is obtained based on the following formula:

[0092] Vref1=V0-k*Vd, wherein Vref1 is the first reference voltage, V0 is a preset fixed voltage, Vd is a second voltage sampling signal, and k is a coefficient; the second voltage sampling signal represents the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

[0093] It should be noted that those skilled in the art can understand the control method here based on the description of the LED driving circuit mentioned above, which will not be described in detail here.

[0094] Although the present invention is disclosed as above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.

Claims

1. An LED driving circuit for driving a load branch, characterized in that: include: A rectifier bridge, used for receiving the mains power and outputting the rectified mains power at an output port of the rectifier bridge, wherein the load branch is connected to the output port; A first energy storage unit connected to the input end of the rectifier bridge; a second energy storage unit connected in parallel with the load branch; The control circuit is configured to control the mains to charge the first energy storage unit to a charging threshold, wherein the charging threshold is determined by the voltage of the mains or the second energy storage unit.

2. The LED driving circuit according to claim 1, characterized in that: The magnitude of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage slope of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage of the second energy storage unit is inversely correlated with the charging threshold.

3. The LED driving circuit according to claim 1, characterized in that: In a positive half cycle of the mains power, the control circuit is configured to control the mains power to charge the first energy storage unit to the charging threshold, and when the voltage of the mains power is greater than the voltage of the second energy storage unit, the mains power supplies power to the load branch and charges the second energy storage unit; as well as In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit is greater than the voltage of the second energy storage unit, the mains and the first energy storage unit supply power to the load branch and charge the second energy storage unit.

4. The LED driving circuit according to claim 3, characterized in that: In the positive half cycle of the mains, when the voltage of the mains is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch; as well as In the negative half cycle of the mains power, when the sum of the voltage of the mains power and the voltage of the first energy storage unit is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch.

5. The LED driving circuit according to claim 1, characterized in that: The control circuit is configured to generate a first reference voltage according to the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit; In the positive half cycle of the AC power, the control circuit controls the AC power to charge the first energy storage unit when the first voltage sampling signal representing the voltage of the first energy storage unit is less than a first reference voltage, and the control circuit controls the AC power to stop charging the first energy storage unit when the first voltage sampling signal reaches the first reference voltage, so that the first energy storage unit is charged to the charging threshold.

6. The LED driving circuit according to claim 5, characterized in that: The control circuit includes a voltage detection unit, a voltage adjustment unit, a comparator and a first power switch; The voltage detection unit generates the first voltage sampling signal according to the voltage of the first energy storage unit; The voltage adjustment unit generates the first reference voltage according to the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit; The first input terminal of the comparator receives the first voltage sampling signal, the second input terminal of the comparator receives the first reference voltage, and the output terminal of the comparator is connected to the control terminal of the first power switch; A branch formed by the first energy storage unit and the first power switch being connected in series is connected between the input end of the rectifier bridge and the ground.

7. The LED driving circuit according to claim 6, characterized in that: In the positive half cycle of the mains power, the comparator controls the first power switch to be turned on when the first voltage sampling signal is less than the first reference voltage, so that the mains power charges the first energy storage unit; and the comparator controls the first power switch to be disconnected when the first voltage sampling signal reaches the first reference voltage, so that the mains stops charging the first energy storage unit; In the negative half cycle of the AC power, the first power switch is turned on, so that the first energy storage unit is discharged.

8. The LED driving circuit according to claim 6, characterized in that: The voltage detection unit includes a first resistor and a second resistor, wherein the first end of the first resistor is connected to the first end of the first energy storage unit, the second end of the first resistor is grounded through the second resistor, and the second end of the first resistor is connected to the first input end of the comparator.

9. The LED driving circuit according to claim 6, characterized in that: The voltage adjustment unit includes a detection unit and a reference voltage generation unit; the detection unit is used to provide a second voltage sampling signal according to the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit; The reference voltage generating unit generates the first reference voltage according to the second voltage sampling signal.

10. The LED driving circuit according to claim 9, characterized in that: The reference voltage generating unit calculates and obtains the first reference voltage based on the following formula: Vref1=V0-k*Vd, wherein Vref1 is the first reference voltage, V0 is a preset fixed voltage, Vd is the second voltage sampling signal, and k is a coefficient.

11. The LED driving circuit according to claim 9, characterized in that: The detection unit includes a third resistor and a fourth resistor; The first end of the third resistor is connected to the second energy storage unit or the load branch or the input end of the rectifier bridge, the second end of the third resistor is grounded through a fourth resistor, and the second end of the third resistor is connected to the reference voltage generating unit to provide the second voltage sampling signal.

12. The LED driving circuit according to claim 11, characterized in that: The voltage adjustment unit further includes a filter capacitor, and the filter capacitor is connected in parallel with the fourth resistor.

13. The LED driving circuit according to claim 1, characterized in that: The load branch includes a load and a constant current control circuit connected to each other; The constant current control circuit includes a second power switch, an operational amplifier and a fifth resistor. The first end of the second power switch is connected to the first end of the constant current control circuit. The first input end of the operational amplifier is connected to a second reference voltage. The second input end of the operational amplifier is connected to the second end of the second power switch and then to the second end of the constant current control circuit through the fifth resistor. The output end of the operational amplifier is connected to the control end of the second power switch.

14. A control method for an LED driving circuit, wherein the LED driving circuit comprises a rectifier bridge, a load branch, a first energy storage unit and a second energy storage unit, wherein the rectifier bridge rectifies the mains power and outputs it at its output port, the load branch is connected to the output port, the first energy storage unit is connected to the input end of the rectifier bridge, and the second energy storage unit is connected in parallel with the load branch, characterized in that: The control method comprises: The mains power is controlled to charge the first energy storage unit to a charging threshold, wherein the charging threshold is determined by the voltage of the mains power or the second energy storage unit.

15. The control method of the LED driving circuit according to claim 14, characterized in that: The magnitude of the mains power is inversely correlated with the charging threshold, or the magnitude of the voltage slope of the mains power is inversely correlated with the charging threshold, or the voltage of the second energy storage unit is inversely correlated with the charging threshold.

16. The control method of the LED driving circuit according to claim 14, characterized in that: In the positive half cycle of the mains power, the mains power is controlled to charge the first energy storage unit to the charging threshold, and when the voltage of the mains power is greater than the voltage of the second energy storage unit, the mains power supplies power to the load branch and charges the second energy storage unit; as well as In the negative half cycle of the mains, when the sum of the voltage of the mains and the voltage of the first energy storage unit is greater than the voltage of the second energy storage unit, the mains and the first energy storage unit supply power to the load branch and charge the second energy storage unit.

17. The control method of the LED driving circuit according to claim 16, characterized in that: In the positive half cycle of the mains power, when the voltage of the mains power is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch; as well as In the negative half cycle of the mains power, when the sum of the voltage of the mains power and the voltage of the first energy storage unit is less than or equal to the voltage of the second energy storage unit, the second energy storage unit supplies power to the load branch.

18. The control method of the LED driving circuit according to claim 14, characterized in that: In the positive half cycle of the mains power, when a first voltage sampling signal representing the voltage of the first energy storage unit is less than a first reference voltage, the mains power is controlled to charge the first energy storage unit, and when the first voltage sampling signal reaches the first reference voltage, the mains power is controlled to stop charging the first energy storage unit, so that the first energy storage unit is charged to the charging threshold; The first reference voltage is generated based on the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

19. The control method of the LED driving circuit according to claim 18, characterized in that: The first reference voltage is obtained based on the following formula: Vref1=V0-k*Vd, wherein Vref1 is the first reference voltage, V0 is a preset fixed voltage, Vd is a second voltage sampling signal, and k is a coefficient; The second voltage sampling signal represents the voltage of the mains, the voltage slope of the mains, or the voltage of the second energy storage unit.

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