LED driving circuit and control method

Abstract

The embodiment of the present invention discloses an LED driving circuit and a control method, which are used to drive an LED lamp according to an input voltage. The LED driving circuit includes: a control circuit, which is used to generate a control signal according to the input voltage; and a constant current circuit, which is connected in series with the LED lamp and is used to adjust the driving current flowing through the LED lamp according to the control signal. The circuit can be applied to different input voltage ranges to ensure that the input power is within the rated power range, thereby improving the reliability and safety of the system.

Description

Technical Field

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

[0002] Compared with traditional light sources, LED (Light Emitting Diode) has the advantages of small size, energy saving, long life, high brightness and environmental protection, so it is widely used in indoor and outdoor lighting.

[0003] The brightness of LED lights is related to the driving current, and the corresponding driving schemes are linear driving scheme and switch driving scheme. The two schemes use linear regulation transistors and switch control transistors to regulate the driving current respectively.

[0004] Figure 1 FIG. 2 shows a schematic circuit diagram of an LED driving circuit according to the prior art. Figure 1 As shown, the LED driving circuit 100 includes an AC current source 101, a rectifier bridge 102, an input capacitor Cin, a current sampling resistor Rs, and a linear constant current module 110. An input voltage Vin is provided between the two output ends of the rectifier bridge 102. The LED lamp 103 is connected in series with the linear constant current module 110 and the current sampling resistor Rs between the two output ends of the rectifier bridge 103.

[0005] The linear constant current module 110 includes a power tube 112 and an amplifier 111. The amplifier 111 compares the current sampling signal obtained by the current sampling resistor Rs with the reference voltage Vref, generates a driving signal according to the difference between the two, and controls the driving current flowing through the power tube 112. After the circuit is stable, the value of the driving current controlled by the linear constant current module 110 is Vref / Rs.

[0006] In the above-mentioned LED driving circuit, the input voltage Vin is required to be greater than the load voltage of the LED lamp, otherwise the rated current cannot be output. At the same time, since the voltage drop on the linear constant current chip is the difference between the input voltage and the output load voltage, the power consumption on the linear constant current system chip is directly related to the input voltage. The higher the input voltage, the lower the efficiency. In order to ensure sufficient light efficiency, the input voltage range of the existing LED driving circuit is generally 220Vac~240Vac or 110Vac~130Vac. When the input voltage exceeds the upper limit of the above-mentioned input voltage range, the input power will be greater than the rated power, which will affect the life of the LED lamp and the driving circuit, as well as the reliability and safety of the system. Summary of the invention

[0007] In view of this, the present invention is used to provide an LED driving circuit, which can be applicable to different input voltage ranges, ensure that the input power is within the rated power range, and improve the reliability and safety of the system.

[0008] According to a first aspect of the present invention, there is provided an LED driving circuit for driving an LED lamp according to an input voltage, the LED driving circuit comprising: a control circuit for generating a control signal according to the input voltage; and a constant current circuit connected in series with the LED lamp, for adjusting a driving current flowing through the LED lamp according to the control signal, so as to stabilize the output power of the LED lamp within a rated power range.

[0009] Preferably, the control signal is a voltage signal, and the constant current circuit includes: a first power tube, used to control the driving current flowing through the LED lamp; a first current sampling resistor, connected in series with the first power tube, used to provide a first current sampling signal; and a first amplifier, used to adjust the driving current according to the control signal and the first current sampling signal.

[0010] Preferably, the control signal is a current signal, and the constant current circuit includes: a second power tube, used to control the driving current flowing through the LED lamp; a second current sampling resistor, connected in series with the second power tube, used to provide a second current sampling signal; a second amplifier, used to compare a reference voltage with a voltage feedback signal to adjust the driving current; and a first feedback resistor, connected between the inverting input terminal of the second amplifier and the source of the second power tube, wherein the first feedback resistor is used to superimpose the control signal and the second current sampling signal to obtain the voltage feedback signal.

[0011] Preferably, the control circuit comprises: a voltage detection module, used for sampling the input voltage to obtain a voltage sampling signal; and a reference control module, used for obtaining the control signal according to the voltage sampling signal.

[0012] Preferably, the reference control module comprises: a current generating unit, for generating a regulating current according to the voltage sampling signal; and an output unit, connected to the current generating unit at an output node, for providing the control signal according to the regulating current.

[0013] Preferably, the current generating unit includes n current sub-units, where n is a natural number greater than zero, and each current sub-unit is used to convert the voltage difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, wherein the threshold voltage is used to characterize the maximum value or minimum value of the corresponding voltage interval.

[0014] Preferably, when the voltage sampling signal is in a first voltage interval, the control signal controls the driving current to decrease as the voltage sampling signal increases; when the voltage sampling signal is in a second voltage interval, the control signal controls the driving current to increase as the voltage sampling signal increases, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval.

[0015] Preferably, the LED driving circuit further includes: when the voltage sampling signal is in a third voltage interval, the control signal controls the driving current to decrease as the voltage sampling signal increases, and the minimum value of the third voltage interval is equal to / greater than the maximum value of the second voltage interval.

[0016] Preferably, the first voltage interval and the second voltage interval are located in a transition interval between a first rated voltage interval and a second rated voltage interval.

[0017] Preferably, the current generating unit includes: a first current sub-unit located on the first current path, used to obtain a first current based on a voltage difference between the voltage sampling signal and a first threshold voltage representing the minimum value of the first voltage interval, wherein the first current sub-unit is connected to the output node, used to output the first current as the regulated current.

[0018] Preferably, the current generating unit also includes: a second current sub-unit located on the second current path, connected to the first current sub-unit, and used to obtain a second current based on a voltage difference between the voltage sampling signal and a second threshold voltage representing the minimum value of the second voltage interval, wherein the second current sub-unit is used to compensate the first current based on the second current.

[0019] Preferably, the current generating unit also includes: a third current sub-unit located on a third current path, used to obtain a third current based on a voltage difference between the voltage sampling signal and a third threshold voltage representing the minimum value of the third voltage interval, wherein the third current sub-unit is connected to the output node, and is used to output the third current as the regulating current.

[0020] Preferably, the first current sub-unit, the second current sub-unit and the third current sub-unit respectively include: a first transistor and a second feedback resistor located on the corresponding current path; and a voltage divider module, which is used to compare the voltage sampling signal with the threshold voltage to control the conduction and shutdown of the first transistor.

[0021] Preferably, the voltage dividing module comprises a plurality of voltage dividing resistors, and the threshold voltage is adjusted by adjusting the resistance values ​​of the plurality of voltage dividing resistors.

[0022] Preferably, the first transistor is an NPN bipolar transistor.

[0023] Preferably, the output unit comprises: a first output resistor connected in series between a reference voltage and the output node, the first output resistor obtaining the control signal in a voltage form according to the regulating current.

[0024] Preferably, the output unit comprises a second transistor and a third transistor, wherein the second transistor and the third transistor constitute a first current mirror for converting the regulating current into the control signal in current form.

[0025] Preferably, the first current sub-unit, the second current sub-unit and the third current sub-unit respectively include: a fourth transistor, a third feedback resistor and a fifth transistor located on the corresponding current path; a third amplifier, used to drive the fourth transistor according to the voltage sampling signal and the potential of the intermediate node between the fourth transistor and the third feedback resistor; and a fourth amplifier, used to drive the third transistor according to the threshold voltage and the potential of the intermediate node between the fifth transistor and the third feedback resistor.

[0026] Preferably, the current generating unit also includes: a sixth transistor connected in series on the first current path; and a fifth amplifier, wherein the non-phase input terminal of the fifth amplifier is used to receive the second threshold voltage, the inverting input terminal is connected to the first terminal of the sixth transistor, and the output terminal is connected to the control terminal of the sixth transistor, and the fifth amplifier is used to drive the sixth transistor according to the second threshold voltage to limit the current value of the first current.

[0027] Preferably, the current generating unit further includes a seventh transistor and an eighth transistor, wherein the seventh transistor and the eighth transistor constitute a second current mirror, so as to mirror the second current to the first current path to compensate for the first current.

[0028] Preferably, the fourth transistor, the fifth transistor and the sixth transistor are respectively N-type metal oxide semiconductor field effect transistors, and the seventh transistor and the eighth transistor are respectively P-type metal oxide semiconductor field effect transistors.

[0029] Preferably, the output unit includes ninth to twelfth transistors and a second output resistor, wherein the ninth transistor, the tenth transistor, the eleventh transistor and the twelfth transistor constitute a third current mirror, the power supply end of the third current mirror is connected to the power supply voltage, the input end is connected to the output node, and the second output resistor is connected in series between the reference voltage and the output end of the third current mirror, wherein the third current mirror is used to mirror the regulating current to the second output resistor, and the second output resistor obtains the control signal in voltage form according to the regulating current.

[0030] Preferably, the ninth transistor and the tenth transistor are P-type metal oxide semiconductor field effect transistors, respectively, and the eleventh transistor and the twelfth transistor are N-type metal oxide semiconductor field effect transistors, respectively.

[0031] Preferably, the output unit includes a thirteenth transistor and a fourteenth transistor, wherein the thirteenth transistor and the fourteenth transistor constitute a fourth current mirror, a power supply end of the fourth current mirror is connected to the power supply voltage, and an input end is connected to the output node to convert the regulating current into the control signal in current form.

[0032] According to another aspect of an embodiment of the present invention, a control method for an LED driving circuit is provided, which is used to drive an LED lamp according to an input voltage. The control method comprises: generating a control signal according to the input voltage; and adjusting a driving current flowing through the LED lamp according to the control signal to stabilize the output power of the LED lamp within a rated power range.

[0033] Preferably, when the input voltage is in a first voltage range, the control signal controls the drive current to decrease as the input voltage increases; when the input voltage is in a second voltage range, the control signal controls the drive current to increase as the input voltage increases, and the minimum value of the second voltage range is equal to the maximum value of the first voltage range.

[0034] Preferably, the control method further comprises: when the input voltage is in a third voltage interval, the control signal controls the drive current to decrease as the input voltage increases, and the minimum value of the third voltage interval is equal to / greater than the maximum value of the second voltage interval.

[0035] Preferably, the first voltage interval and the second voltage interval are located in a transition interval between a first rated voltage interval and a second rated voltage interval.

[0036] Preferably, generating a control signal according to an input voltage comprises: sampling the input voltage to obtain a voltage sampling signal; generating a regulating current according to the voltage sampling signal, and obtaining the control signal in a current form or a voltage form according to the regulating current.

[0037] Preferably, generating the regulating current according to the voltage sampling signal includes: obtaining a first current according to a voltage difference between the voltage sampling signal and a first threshold voltage representing the minimum value of the first voltage interval; and obtaining the regulating current according to the first current, wherein the first current increases with an increase in the voltage difference between the voltage sampling signal and the first threshold voltage.

[0038] Preferably, generating a regulating current according to the voltage sampling signal also includes: obtaining a second current according to a voltage difference between the voltage sampling signal and a second threshold voltage representing the minimum value of the second voltage interval; and providing compensation for the first current according to the second current so that the first current decreases as the voltage difference between the voltage sampling signal and the second threshold voltage increases.

[0039] Preferably, generating a regulating current according to the voltage sampling signal includes: obtaining a third current according to a voltage difference between the voltage sampling signal and a third threshold voltage representing the minimum value of the third voltage interval; and obtaining the regulating current according to the first current and the third current or according to the third current, wherein the third current increases with an increase in the voltage difference between the voltage sampling signal and the third threshold voltage.

[0040] Preferably, generating the regulating current according to the voltage sampling signal further comprises setting a voltage dividing module, the voltage dividing module comprises a plurality of voltage dividing resistors, and the threshold voltage is adjusted by adjusting the resistance values ​​of the voltage dividing resistors.

[0041] Preferably, the control method further comprises providing a constant current circuit for adjusting the driving current flowing through the LED lamp according to the control signal.

[0042] Preferably, the control signal is a voltage signal, the constant current circuit adjusts the drive current according to the control signal and the first current sampling signal, and the change trend of the drive current is the same as the change trend of the control signal.

[0043] Preferably, the control signal is a current signal, and the constant current circuit adjusts the drive current according to the control signal, a reference voltage and a second current sampling signal, wherein the constant current circuit superimposes the control signal on the second current sampling signal so that the change trend of the drive current is opposite to the change trend of the control signal.

[0044] To summarize, the LED driving circuit and control method of the embodiments of the present invention control the driving current to decrease as the input voltage increases within the first voltage interval where the input voltage is greater than the rated voltage interval, thereby ensuring that the input power is always within the rated power range, improving circuit reliability and service life, and improving the utilization rate of the lamp beads, reducing the cost of the entire machine, and improving efficiency.

[0045] Furthermore, the LED driving circuit of the embodiment of the present invention controls the driving current to increase as the input voltage increases in the second voltage interval after the input voltage increases to the first voltage interval, so as to ensure that the system can operate stably when the input voltage increases to the next rated voltage interval. This allows the LED driving circuit to be applicable to input voltages in various voltage ranges, making the LED linear driving solution applicable to wider or more complex power grids, thereby saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages of the present invention will become more apparent through the description of the embodiments of the present invention with reference to the following drawings, in which:

[0047] Figure 1 A schematic circuit diagram of an LED driving circuit according to the prior art is shown;

[0048] Figure 2 A schematic block diagram of an LED driving circuit according to an embodiment of the present invention is shown;

[0049] Figure 3 A schematic circuit diagram of an LED driving circuit according to a first embodiment of the present invention is shown;

[0050] Figure 4 A schematic circuit diagram showing an LED driving circuit according to a second embodiment of the present invention;

[0051] Figure 5 A schematic circuit diagram of a reference control module according to a first embodiment of the present invention is shown;

[0052] Figure 6 Another schematic circuit diagram of a reference control module according to a first embodiment of the present invention is shown;

[0053] Figure 7 A schematic circuit diagram of a reference control module according to a second embodiment of the present invention is shown;

[0054] Figure 8 Another schematic circuit diagram of a reference control module according to a second embodiment of the present invention is shown;

[0055] Fig. 9 A waveform diagram showing the voltage sampling signal and the control signal according to the first embodiment of the present invention;

[0056] Fig.10 Another waveform diagram between the voltage sampling signal and the control signal according to the first embodiment of the present invention is shown;

[0057] Fig.11 A waveform diagram showing the voltage sampling signal and the control signal according to the second embodiment of the present invention;

[0058] Fig.12 Another waveform diagram between the voltage sampling signal and the control signal according to the second embodiment of the present invention is shown. DETAILED DESCRIPTION

[0059] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, and procedures are not described in detail. In addition, the drawings are not necessarily drawn to scale.

[0060] In the present application, the term "LED lamp" refers to, for example, an LED lamp string formed by connecting a plurality of LEDs in series. If a plurality of LEDs form an LED lamp string, the cathode of the preceding LED in the LED lamp string is connected to the anode of the next LED. The anode of the LED lamp refers to the anode of the first LED lamp in the LED lamp string, and the cathode of the LED lamp refers to the cathode of the last LED lamp in the LED lamp string.

[0061] The present invention may be embodied in various forms, some examples of which will be described below.

[0062] Figure 2 FIG. 2 shows a schematic block diagram of an LED driving circuit according to an embodiment of the present invention. Figure 2 As shown, the LED driving circuit 200 includes an AC current source 201, a rectifier bridge 202, an input capacitor Cin, a constant current circuit 230, and a control circuit 240. The rectifier bridge 202 is used to rectify the AC power into DC power, and an input voltage Vin is provided between two output terminals of the rectifier bridge 202, and the input voltage Vin supplies power to the LED lamp 203. The input capacitor Cin performs smooth filtering on the input voltage Vin.

[0063] The basic implementation scheme of the present invention is as follows: when the input voltage Vin is in the first rated voltage interval and the second rated voltage interval, the driving current flowing through the LED lamp 203 is controlled to be constant; when the input voltage Vin is in the first voltage interval, the driving current flowing through the LED lamp 203 is controlled to decrease as the input voltage Vin increases; when the input voltage Vin is in the second voltage interval, the driving current flowing through the LED lamp 203 is controlled to increase as the input voltage Vin increases, the first voltage interval and the second voltage interval are located in the transition interval between the first rated voltage interval and the second rated voltage interval, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval.

[0064] Specifically, Figure 2 As shown, the control circuit 240 is used to provide a control signal to the constant current circuit 230 according to the input voltage Vin. The constant current circuit 230 is connected in series with the LED lamp 203 to adjust the driving current flowing through the LED lamp 203 according to the control signal.

[0065] The control circuit 240 includes a voltage detection module 210 and a reference control module 220. The voltage detection module 210 is connected to the first output terminal of the rectifier bridge 202 to receive the input voltage Vin. The voltage detection module 210 is used to detect the input voltage Vin to obtain a voltage sampling signal. The reference control module 220 is connected to the voltage detection module 210 and is used to obtain a control signal according to the voltage sampling signal.

[0066] Figure 3 and Figure 4 The circuit structure diagrams of the first embodiment and the second embodiment based on the basic implementation scheme of the present invention are respectively shown, and the main difference between the two is the form of the control signal. If the control signal is a voltage signal, the reference voltage of the constant current circuit 230 is adjusted according to the control signal, and then the drive current is adjusted; if the control signal is a current signal, the current sampling signal of the constant current circuit 230 is adjusted according to the control signal, and then the drive current is adjusted. It should be noted that these two embodiments are only two specific circuit implementations based on the concept of the present invention, and do not constitute a limitation on the basic implementation scheme of the present invention.

[0067] like Figure 3 As shown, the LED driving circuit 300 includes an AC current source 301, a rectifier bridge 302, an LED lamp 303, an input capacitor Cin, a voltage detection module 310, a reference control module 320 and a constant current circuit 330. The AC current source 301, the rectifier bridge 302, the LED lamp 303 and the input capacitor Cin are connected to the Figure 2 The structures and functions of the AC current source 201, the rectifier bridge 202, the LED lamp 203 and the input capacitor Cin shown in FIG. 1 are the same and will not be described in detail here.

[0068] The voltage detection module 310 includes voltage-dividing resistors R1 and R2, and an amplifier U1. The positive input terminal of the amplifier U1 is connected to the intermediate node of the resistor R1 and the resistor R2. The negative input terminal of the amplifier U1 is connected to the output terminal, and the output terminal of the amplifier U1 is connected to the reference control module 320 to provide a voltage sampling signal V1.

[0069] The reference control module 320 is configured to obtain a control signal Vref1 in the form of a voltage based on the voltage sampling signal V1. The constant current circuit 330 includes an amplifier U2, a power transistor M1, and a current sampling resistor Rs1. The power transistor M1 and the current sampling resistor Rs1 are connected in series between the LED lamp 303 and the ground. The intermediate node of the power transistor M1 and the current sampling resistor Rs1 is used to provide a first current sampling signal. The positive input terminal of the amplifier U2 is used to receive the control signal Vref1, and the negative input terminal is used to receive the first current sampling signal. The amplifier U2 is configured to drive the power transistor M1 based on the control signal Vref1 and the first current sampling signal to adjust the driving current. For example, the constant current value Iout of the driving current = Vref1 / Rs1.

[0070] It can be seen from the above formula that the constant current value of the driving current Iout can be adjusted by adjusting the magnitude of the control signal Vref1. As Fig. 9 shown, when V1≤Va, the control signal Vref1 remains unchanged and the driving current remains constant; when Va<V1≤Vb, the control signal Vref1 decreases as the voltage sampling signal V1 increases; when Vb<V1≤Vc, the control signal Vref1 increases as the voltage sampling signal V1 increases, and when the control signal Vref1 increases to a preset voltage value Vref, the control signal Vref1 remains constant; when V1>Vc, the control signal Vref1 decreases as the voltage sampling signal V1 increases.

[0071] Fig.10 shows another waveform diagram between the voltage sampling signal and the control signal according to the first embodiment of the present invention. As Fig.10 shown, in another embodiment, before the control signal Vref1 increases to the preset voltage value Vref, the voltage sampling signal V1 has increased to the third threshold voltage Vc. At this time, the control signal Vref1 decreases as the voltage sampling signal V1 increases.

[0072] Among them, Va is the first threshold voltage, which is used to represent the minimum value of the first voltage interval; Vb is the second threshold voltage, which is used to represent the minimum value of the second voltage interval; Vc is the third threshold voltage, which is used to represent the minimum value of the third voltage interval. Among them, the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, and the minimum value of the third voltage interval is greater than or equal to the maximum value of the second voltage interval.

[0073] The threshold voltage can be preset, for example, the rated voltage range of the existing LED driving circuit generally includes a first rated voltage interval (e.g., 110Vac to 130Vac) and a second rated voltage interval (e.g., 220Vac to 240Vac), the first threshold voltage and the second threshold voltage are located in a transition interval between the first rated voltage interval and the second rated voltage interval, and the second threshold voltage is greater than the first threshold voltage. Of course, in a preferred embodiment, a third rated voltage interval is also included, and the third threshold voltage is located in a transition interval between the second rated voltage interval and the third rated voltage interval.

[0074] When the voltage sampling signal V1 is greater than the first threshold voltage Va (i.e., the input voltage is greater than the maximum voltage in the first rated voltage interval), the control signal Vref1 decreases as the voltage sampling signal V1 increases, so as to reduce the driving current flowing through the LED lamp, reduce the input power, and ensure that the input power is always within the rated power range in this interval, thereby improving the reliability and safety of the system. When the voltage sampling signal V1 is greater than the second threshold voltage Vb, in order to ensure that the system can work stably when the input voltage increases to the second rated voltage interval, during the period when the voltage sampling signal V1 is greater than the second threshold voltage and less than the third threshold voltage Vc, the control signal Vref1 increases as the voltage sampling signal V1 increases. When the control signal Vref1 increases to the preset voltage value Vref, the control signal Vref1 is kept constant, so as to ensure that the system can work stably when the input voltage is in the second rated voltage interval. When the voltage sampling signal V1 is greater than the third threshold voltage Vc, the control signal Vref1 decreases as the voltage sampling signal V1 increases, so as to reduce the driving current flowing through the LED lamp and reduce the input power. Or when the voltage sampling signal V1 has increased to the third threshold voltage Vc before the control signal Vref1 increases to the preset voltage value Vref, the control signal Vref1 decreases as the voltage sampling signal V1 increases, ensuring that the input power is always within the rated power range when the input voltage is greater than the maximum voltage of the second rated voltage interval, thereby improving the reliability and safety of the system.

[0075] like Figure 4 As shown, the LED driving circuit 400 includes an AC current source 401, a rectifier bridge 402, an LED lamp 403, an input capacitor Cin, a voltage detection module 410, a reference control module 420 and a constant current circuit 430. The AC current source 401, the rectifier bridge 402, the LED lamp 403, the voltage detection module 410 and the input capacitor Cin are connected to the LED driving circuit 400. Figure 3 The structures and functions of the AC current source 301, the rectifier bridge 302, the LED lamp 303, the voltage detection module 310 and the input capacitor Cin shown in FIG. 3 are the same and will not be described in detail herein.

[0076] The reference control module 420 is used to obtain a control signal Io based on the voltage sampling signal V1. The constant current circuit 430 includes a power transistor M2, a current sampling resistor Rs2, an amplifier U3, and a feedback resistor R3. The power transistor M2 and the current sampling resistor Rs2 are connected in series between the LED lamp 403 and the ground, and the intermediate node between the power transistor M2 and the current sampling resistor Rs2 is used to provide a second current sampling signal. The non-inverting input terminal of the amplifier U3 is used to receive a reference voltage Vref2, and the inverting input terminal is used to receive a voltage feedback signal. The feedback resistor R3 is connected between the inverting input terminal and the output terminal of the amplifier U3. In this embodiment, the amplifier U3 superimposes the control signal Io on the second current sampling signal to obtain a voltage feedback signal, and drives the power transistor M2 according to the reference voltage Vref2 and the voltage feedback signal to adjust the drive current. For example, the constant current value of the drive current Iout is Iout = (Vref2 - Io * R3) / Rs2.

[0077] It can be seen from the above formula that the constant current value of the drive current Iout can be adjusted by adjusting the magnitude of the control signal Io. As Fig.11 shown, when V1 ≤ Va, the control signal Io is 0 and the drive current remains constant; when Va < V1 ≤ Vb, the control signal Io increases as the voltage sampling signal V1 increases, and the drive current Iout decreases as the voltage sampling signal V1 increases; when Vb < V1 ≤ Vc, the control signal Io decreases as the voltage sampling signal V1 increases, and when the control signal Io decreases to 0, the control signal Io remains unchanged; when V1 > Vc, the control signal Io increases as the voltage sampling signal V1 increases.

[0078] Similarly, Va is the first threshold voltage, which is used to represent the minimum value of the first voltage interval; Vb is the second threshold voltage, which is used to represent the minimum value of the second voltage interval; Vc is the third threshold voltage, which is used to represent the minimum value of the third voltage interval. Among them, the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, and the minimum value of the third voltage interval is greater than or equal to the maximum value of the second voltage interval.

[0079] Fig.12 shows another waveform diagram between the voltage sampling signal and the control signal according to the second embodiment of the present invention. As Fig.12 shown, in another embodiment, before the control signal Io decreases to 0, the voltage sampling signal V1 has increased to the third threshold voltage Vc, and at this time, the control signal Io increases as the voltage sampling signal V1 increases.

[0080] The LED driving circuit of the embodiment of the present invention controls the driving current to decrease as the input voltage increases in the first voltage interval where the input voltage is greater than the rated voltage interval, thereby ensuring that the input power is always within the rated power range, improving the circuit reliability and service life, and improving the utilization rate of the lamp beads, reducing the cost of the entire machine, and improving efficiency.

[0081] In addition, the LED driving circuit of the embodiment of the present invention controls the driving current to increase as the input voltage increases in the second voltage interval after the input voltage increases to the first voltage interval, so as to ensure that the system can operate stably when the input voltage increases to the next rated voltage interval, so that the LED driving circuit can be suitable for input voltages in various voltage ranges, saving production costs.

[0082] Figure 5 FIG. 4 shows a circuit structure diagram of a reference control module according to a first embodiment of the present invention. Figure 5 As shown, the reference control module 520 includes a current generating unit 501 and an output unit 502. The current generating unit 501 is used to generate a regulating current Ig according to the voltage sampling signal V1, and the intermediate node between the output unit 502 and the current generating unit 501 is an output node, which is used to provide the regulating current Ig, and the output unit 502 is used to provide a control signal Vref1 according to the regulating current Ig.

[0083] Further, the current generating unit 501 includes n current subunits connected in parallel, where n is a natural number greater than 0. Each current subunit is used to convert the difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, and obtain the regulating current Ig according to the current signal.

[0084] As a non-limiting example, the current generating unit 501 includes a current subunit 511 located on a first current path, and a current subunit 512 located on a second current path. The current subunit 511 is used to obtain a first current I1 according to a voltage difference between a voltage sampling signal V1 and a first threshold voltage Va, and the current subunit 512 is used to obtain a second current I2 according to a voltage difference between the voltage sampling signal V1 and a second threshold voltage Vb. The current subunit 511 is connected to an output node, and is used to output the first current I1 as a regulating current Ig.

[0085] The current subunit 511 includes a transistor Q1 and a feedback resistor R21 connected in series on a first current path, and a voltage dividing module composed of voltage dividing resistors R13 and R14 connected between the voltage sampling signal V1 and the ground, wherein the intermediate node of the voltage dividing resistor R13 and the voltage dividing resistor R14 is used to provide a turn-on signal to the transistor Q1. The voltage dividing module is used to turn on the transistor Q1 when the voltage sampling signal V1 is greater than the first threshold voltage Va, and the current I1 flowing through the transistor Q1 is equal to (Vbq1-Vbeq1) / R21, wherein Vbq1 is the base voltage of the transistor Q1, and Vbeq1 is the be junction voltage of the transistor Q1, so the regulating current Ig=I1=(Vbq1-Vbeq1) / R21 can be obtained.

[0086] The output unit 502 includes an output resistor R31 connected between the reference voltage Vref and the output node. The output resistor R31 provides a control signal Vref1 at the output node according to the regulated current, for example, Vref1=Vref-Ig*R31=Vref-(Vbq1-Vbeq1)*(R31 / R21). It can be concluded from the above formula that the greater the voltage difference between the voltage sampling signal V1 and the first threshold voltage Va, the greater the base voltage of the transistor Q1, and then the smaller the control signal Vref1.

[0087] The current subunit 512 includes a transistor Q2 and a feedback resistor R22 connected in series on the second current path. The first end of the transistor Q2 is connected to the control end of the transistor Q1 for providing a compensation signal to the transistor Q1 when the transistor Q2 is turned on.

[0088] The current subunit 512 also includes a voltage dividing module composed of a voltage dividing resistor R11 and a voltage dividing resistor R12 connected in series between the voltage sampling signal V1 and the ground, and the intermediate node between the voltage dividing resistor R11 and the voltage dividing resistor R12 is used to provide a turn-on signal to the transistor Q2. The voltage dividing module is used to turn on the transistor Q2 when the voltage sampling signal V1 is greater than the second threshold voltage Vb, and the current I2 flowing through the transistor Q2 is (Vbq2-Vbeq2) / R22, where Vbq2 is the base voltage of the transistor Q2, and Vbeq2 is the be junction voltage of the transistor Q2. The greater the voltage difference between the voltage sampling signal V1 and the second threshold voltage Vb, the greater the base voltage of the transistor Q2, and then the greater the second current I2. Due to the compensation effect of the second current I2 on the transistor Q1, the control signal Vref1 = Vref-[V1-I2*R13-V1*R13 / (R13+R14)-Vbeq1]*R31 / R21 can be obtained when the voltage sampling signal V1 is greater than the second threshold voltage Vb. It can be seen from the above formula that the greater the second current I2, the greater the control signal Vref1, so the control signal Vref1 increases with the increase of the voltage sampling signal V1.

[0089] like Fig. 9 As shown, as the voltage difference between the voltage sampling signal V1 and the second threshold voltage Vb increases, the base voltage of the transistor Q1 gradually decreases. When the base voltage of the transistor Q1 is less than the turn-on threshold of the transistor Q1, the transistor Q1 is turned off. At this time, the control signal Vref1 is equal to the reference voltage Vref, and the control signal Vref1 is kept constant.

[0090] In some embodiments, the current generating unit 501 further includes a current sub-unit 513 located in the third current path, and the current sub-unit 513 is used to provide a third current I3 according to a voltage difference between the voltage sampling signal V1 and the third threshold voltage Vc.

[0091] like Figure 5 As shown, the current subunit 513 includes a transistor Q3, a feedback resistor R23, and a voltage dividing module composed of a voltage dividing resistor R15 and a voltage dividing resistor R16 connected in series between the voltage sampling signal V1 and the ground, and the intermediate node of the voltage dividing resistor R15 and the voltage dividing resistor R16 is used to provide a turn-on signal to the transistor Q3. The voltage dividing module is used to turn on the transistor Q3 when the voltage sampling signal V1 is greater than the third threshold voltage Vc, and the current I3 flowing through the transistor Q3 is (Vbq3-Vbeq3) / R23, wherein Vbq3 is the base voltage of the transistor Q3, and Vbeq3 is the be junction voltage of the transistor Q3.

[0092] Since transistor Q3 is also connected to the output node, the control signal Vref1=Vref-Ig*R31=Vref-(Vbq3-Vbeq3)*(R31 / R23) can be obtained. From the above formula, it can be concluded that the greater the voltage difference between the voltage sampling signal V1 and the third threshold voltage Vc, the greater the base voltage of transistor Q3, and then the smaller the control signal Vref1.

[0093] like Fig.10 As shown, in another embodiment, transistor Q1 and transistor Q3 are in the on state at the same time, so the adjustment current Ig is the combined current of the first current I1 and the third current I3. Due to the effect of the third current I3, the control signal Vref1 decreases as the voltage sampling signal V1 increases before it increases to the reference voltage Vref.

[0094] like Figure 5 As shown, the first threshold voltage Va=Vbeq1*(R13+R14) / R14, the second threshold voltage Vb=Vbeq2*(R11+R12) / R12, and the third threshold voltage Vc=Vbeq3*(R15+R16) / R16. Therefore, the value of the first threshold voltage Va-the third threshold voltage Vc can be changed by changing the resistance of the voltage-dividing resistors R11-R16, which actually changes the size of the threshold voltage. Therefore, the size of the threshold voltage can be changed by preset conditions.

[0095] Figure 6 FIG. 2 shows another circuit structure diagram of the reference control module according to the first embodiment of the present invention. Figure 6 As shown, the reference control module 620 includes a current generating unit 601 and an output unit 602. The current generating unit 601 is used to generate a regulating current Ig according to the voltage sampling signal V1, and the first connection point between the output unit 602 and the current generating unit 601 is an output node, which is used to provide the regulating current Ig, and the output unit 602 is used to provide a control signal Vref1 according to the regulating current Ig.

[0096] Further, the current generating unit 601 includes n current subunits connected in parallel, where n is a natural number greater than 0. Each current subunit is used to convert the difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, and obtain the regulating current Ig according to the current signal.

[0097] As a non-limiting example, the current generating unit 601 includes a current subunit 611 located on the fourth current path, and a current subunit 612 located on the fifth current path. The current subunit 611 is used to obtain a fourth current I4 according to the difference between the voltage sampling signal V1 and the first threshold voltage Va, and the current subunit 612 is used to obtain a fifth current I5 according to the difference between the voltage sampling signal V1 and the second threshold voltage Vb. The current subunit 611 is connected to the output node, and is used to output the fourth current I4 as the adjustment current Ig.

[0098] The current subunit 611 includes a transistor N4, a resistor R52, a transistor N5, and amplifiers U14 and U15 connected in series in a fourth current path.

[0099] The non-inverting input terminal of the amplifier U14 is used to receive the voltage sampling signal V1, and the inverting input terminal is connected to the middle node of the transistor N4 and the resistor R52. The amplifier U14 is used to drive the transistor N4 according to the voltage sampling signal V1 and the voltage difference between the middle node of the transistor N4 and the resistor R52. The non-inverting input terminal of the amplifier U15 is connected to the middle node of the transistor N5 and the resistor R52, and the inverting input terminal is used to receive the first threshold voltage Va. The amplifier U15 is used to drive the transistor N5 according to the voltage difference between the first threshold voltage Va and the middle node of the transistor N5 and the resistor R52.

[0100] When the voltage sampling signal V1 is less than the first threshold voltage Va, the transistor N5 is turned off and the fourth current path is disconnected; when the voltage sampling signal V1 is greater than the first threshold voltage Va and less than the second threshold voltage Vb, the transistors N4 and N5 are turned on, the voltage of the middle node between the transistor N4 and the resistor R52 is equal to V1, and the voltage of the middle node between the transistor N5 and the resistor R52 is equal to Va, then the fourth current I4 on the fourth current path is equal to (V1-Va) / R52. It can be seen from the above formula that the greater the difference between the voltage sampling signal V1 and the first threshold voltage Va, the greater the fourth current I4. At this time, the regulating current Ig is equal to I4. The output unit 602 includes transistors P3 and P4, transistors N8 and N9, and an output resistor R41. The transistor P3 and the transistor P4 as well as the transistor N8 and the transistor N9 form a current mirror structure for mirroring the regulating current Ig to the output resistor R41 to obtain a control signal Vref1=Vref-Ig*R41. From the above formula, it can be obtained that the control signal Vref1 decreases as the fourth current I4 increases.

[0101] In a preferred embodiment, the current generating unit 601 further includes a transistor N3 and an amplifier U13, wherein the non-inverting input terminal of the amplifier U13 is used to receive the second threshold voltage Vb, the inverting input terminal is connected to the second path terminal of the transistor N3, and the output terminal is connected to the control terminal of the transistor N3. The amplifier U13 is used to control the maximum current value of the fourth current I4 on the fourth current path according to the second threshold voltage Vb, for example, the current I4max=(Vb-Va) / R52.

[0102] The current subunit 612 includes a transistor N1, a transistor N2 and a resistor R51 connected in series in a fifth current path, and an amplifier U11 and an amplifier U12. The non-inverting input terminal of the amplifier U11 is used to receive the voltage sampling signal V1, and the inverting input terminal is connected to the middle node of the transistor N1 and the resistor R51. The amplifier U11 is used to drive the transistor N1 according to the voltage sampling signal V1 and the voltage difference between the middle node of the transistor N1 and the resistor R51. The non-inverting input terminal of the amplifier U12 is connected to the middle node of the transistor N2 and the resistor R51, and the inverting input terminal is used to receive the second threshold voltage Vb. The amplifier U12 is used to drive the transistor N2 according to the voltage difference between the second threshold voltage Vb and the middle node of the transistor N2 and the resistor R51.

[0103] When the voltage sampling signal V1 is less than the second threshold voltage Vb, the transistor N2 is turned off and the fifth current path is disconnected. When the voltage sampling signal V1 is greater than the second threshold voltage Vb, the transistors N1 and N2 are turned on, the voltage of the middle node between the transistor N1 and the resistor R51 is equal to V1, and the potential of the middle node between the transistor N2 and the resistor R51 is equal to Vb, then the fifth current I5 on the fifth current path = (V1-Vb) / R51. It can be seen from the above formula that the greater the difference between the voltage sampling signal V1 and the second threshold voltage Vb, the greater the fifth current I5.

[0104] The current generating unit 601 further includes a current mirror 614, which includes a transistor P1 and a transistor P2, and is used to mirror the fifth current I5 of the fifth current path to the fourth current path to compensate the fourth current I4, and the fourth current I4=I4max-I5. It can be seen from the above formula that the larger the fifth current I5 is, the smaller the fourth current I4 will be, and then the larger the control signal Vref1 will be.

[0105] In some embodiments, the current generating unit 601 further includes a current sub-unit 613 located on a sixth current path, configured to generate a sixth current I6 according to a difference between the voltage sampling signal V1 and the third threshold voltage Vc.

[0106] like Figure 6 As shown, the current subunit 613 includes a transistor N6, a transistor N7 and a resistor R53 connected in series in the sixth current path, and an amplifier U16 and an amplifier U17. The positive phase input terminal of the amplifier U16 is used to receive the voltage sampling signal V1, and the negative phase input terminal is connected to the middle node of the transistor N6 and the resistor R53. The amplifier U16 is used to drive the transistor N6 according to the voltage sampling signal V1 and the voltage difference between the middle node of the transistor N6 and the resistor R53. The positive phase input terminal of the amplifier U17 is connected to the middle node of the transistor N7 and the resistor R53, and the negative phase input terminal is used to receive the third threshold voltage Vc. The amplifier U17 is used to drive the transistor N7 according to the voltage difference between the third threshold voltage Vb and the middle node of the transistor N7 and the resistor R53.

[0107] When the voltage sampling signal V1 is less than the third threshold voltage Vc, transistor N7 is turned off and the sixth current path is disconnected. When the voltage sampling signal V1 is greater than the third threshold voltage Vc, transistors N6 and N7 are turned on, the voltage of the middle node between transistor N6 and resistor R53 is equal to V1, the voltage of the middle node between transistor N7 and resistor R53 is equal to Vc, and the sixth current I6 on the sixth current path is equal to (V1-Vc) / R53. It can be seen from the above formula that the greater the difference between the voltage sampling signal V1 and the third threshold voltage Vc, the greater the sixth current I6. At this time, the regulating current Ig=I6, the greater the sixth current I6, the greater the regulating current Ig, and the smaller the control signal Vref1.

[0108] In this embodiment, the current generating unit 601 is implemented by a semiconductor field effect transistor, and the threshold voltage can be adjusted without changing the circuit structure. The circuit stability is higher, and compared with bipolar transistors, the threshold voltage is less affected by the process and has higher accuracy.

[0109] Figure 7 FIG. 4 shows a circuit structure diagram of a reference control module according to a second embodiment of the present invention. Figure 7 As shown, the reference control module 720 includes a current generating unit 701 and an output unit 702. The current generating unit 701 is used to generate a regulating current Ig according to the voltage sampling signal V1, and the intermediate node between the output unit 702 and the current generating unit 701 is an output node, and the output node is used to provide the regulating current Ig, and the output unit 702 is used to provide a control signal Io according to the regulating current Ig. Figure 5 The structure and principle of the current generating unit 501 shown are the same and will not be described again.

[0110] The output unit 702 includes a transistor P5 and a transistor P6. The transistor P5 and the transistor P6 form a current mirror structure for mirroring the regulating current Ig into a control signal Io in the form of a current.

[0111] Figure 8 Another circuit structure diagram of the reference control module according to the second embodiment of the present invention is shown as follows: Figure 8 As shown, the reference control module 820 includes a current generating unit 801 and an output unit 802. The current generating unit 801 is used to generate a regulating current Ig according to the voltage sampling signal V1, and the middle connection point between the output unit 802 and the current generating unit 801 is an output node, and the output node is used to provide the regulating current Ig, and the output unit 802 is used to provide a control signal Io according to the regulating current Ig. Figure 6 The structure and principle of the current generating unit 601 shown are the same and will not be described again.

[0112] The output unit 802 includes a transistor P7 and a transistor P8. The transistor P7 and the transistor P8 form a current mirror structure for mirroring the regulating current Ig into a control signal Io in the form of a current.

[0113] Furthermore, in the above embodiment, transistors Q1 , Q2 , and Q3 are NPN bipolar transistors, transistors N1 - N9 are N-type oxide semiconductor field effect transistors, and transistors P1 - P8 are P-type oxide semiconductor field effect transistors.

[0114] According to another aspect of the present invention, a control method for an LED driving circuit is provided, which is used to control the above-mentioned LED driving circuit. When the input voltage is in a first voltage interval, the driving current is controlled to decrease as the input voltage increases, when the input voltage is in a second voltage interval, the driving current is controlled to increase as the input voltage increases, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval, when the input voltage is in a third voltage interval, the driving current is controlled to decrease as the input voltage increases, and the minimum value of the third voltage interval is equal to / greater than the maximum value of the second voltage interval, so as to stabilize the output power of the LED lamp within the rated power range.

[0115] To sum up, the LED driving circuit and control method of the embodiments of the present invention control the driving current to decrease as the input voltage increases in the first voltage interval after the input voltage is in the rated voltage interval, thereby ensuring that the input power is always within the rated power range, improving the circuit reliability and service life, and improving the utilization rate of the lamp beads, reducing the cost of the entire machine, and improving efficiency.

[0116] Furthermore, the LED driving circuit of the embodiment of the present invention controls the driving current to increase as the input voltage increases in the second voltage interval after the input voltage increases to the first voltage interval, so as to ensure that the system can operate stably when the input voltage increases to the next rated voltage interval. This allows the LED driving circuit to be applicable to input voltages in various voltage ranges, making the LED linear driving solution applicable to wider or more complex power grids, thereby saving costs.

[0117] According to the embodiments of the present invention, as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. An LED driving circuit for driving an LED lamp according to an input voltage, characterized in that: The LED driving circuit comprises: a control circuit, configured to generate a control signal according to the input voltage; and a constant current circuit, connected in series with the LED lamp, for adjusting the driving current flowing through the LED lamp according to the control signal, so as to stabilize the output power of the LED lamp within the rated power range, Wherein, the control circuit comprises: a voltage detection module, used for sampling the input voltage to obtain a voltage sampling signal; and A reference control module, used to obtain the control signal according to the voltage sampling signal, When the voltage sampling signal is in the first voltage interval, the control signal controls the driving current to decrease as the voltage sampling signal increases. When the voltage sampling signal is in a second voltage interval, the control signal controls the driving current to increase as the voltage sampling signal increases, and the minimum value of the second voltage interval is equal to the maximum value of the first voltage interval.

2. The LED driving circuit according to claim 1, characterized in that: The control signal is a voltage signal, and the constant current circuit comprises: A first power tube, used to control the driving current flowing through the LED lamp; A first current sampling resistor is connected in series with the first power tube and is used to provide a first current sampling signal; and The first amplifier is used to adjust the driving current according to the control signal and the first current sampling signal.

3. The LED driving circuit according to claim 1, characterized in that: The control signal is a current signal, and the constant current circuit comprises: A second power tube, used to control the driving current flowing through the LED lamp; A second current sampling resistor is connected in series with the second power tube and is used to provide a second current sampling signal; a second amplifier, for comparing a reference voltage with a voltage feedback signal to adjust the drive current; and A first feedback resistor is connected between the inverting input terminal of the second amplifier and the source of the second power tube. The first feedback resistor is used to superimpose the control signal and the second current sampling signal to obtain the voltage feedback signal.

4. The LED driving circuit according to claim 1, characterized in that: The reference control module comprises: a current generating unit, configured to generate a regulating current according to the voltage sampling signal; and An output unit is connected to the current generating unit at an output node and is used to provide the control signal according to the regulating current.

5. The LED driving circuit according to claim 4, characterized in that: The current generating unit includes n current subunits, where n is a natural number greater than zero. Each current subunit is used to convert the voltage difference between the voltage sampling signal and the corresponding threshold voltage into a current signal, wherein the threshold voltage is used to represent the maximum value or the minimum value of the corresponding voltage interval.

6. The LED driving circuit according to claim 5, characterized in that: Also includes: When the voltage sampling signal is in a third voltage interval, the control signal controls the driving current to decrease as the voltage sampling signal increases, and the minimum value of the third voltage interval is equal to / greater than the maximum value of the second voltage interval.

7. The LED driving circuit according to claim 1, characterized in that: The first voltage interval and the second voltage interval are located in a transition interval between a first rated voltage interval and a second rated voltage interval.

8. The LED driving circuit according to claim 6, characterized in that: The current generating unit comprises: a first current subunit located on the first current path, used to obtain a first current according to a voltage difference between the voltage sampling signal and a first threshold voltage representing a minimum value of the first voltage interval, The first current subunit is connected to the output node and is used to output the first current as the regulating current.

9. The LED driving circuit according to claim 8, characterized in that , the current generating unit also includes: a second current subunit located on the second current path, connected to the first current subunit, and configured to obtain a second current according to a voltage difference between the voltage sampling signal and a second threshold voltage representing a minimum value of the second voltage interval, The second current subunit is used to compensate the first current according to the second current.

10. The LED driving circuit according to claim 9, characterized in that: The current generating unit further comprises: a third current subunit located on the third current path, configured to obtain a third current according to a voltage difference between the voltage sampling signal and a third threshold voltage representing a minimum value of the third voltage interval, Wherein, the third current subunit is connected to the output node, and is used to output the third current as the regulating current.

11. The LED driving circuit according to claim 10, characterized in that: The first current subunit, the second current subunit and the third current subunit respectively include: a first transistor and a second feedback resistor located on a corresponding current path; and The voltage dividing module is used to compare the voltage sampling signal with the threshold voltage to control the on and off of the first transistor.

12. The LED driving circuit according to claim 11, characterized in that: The voltage division module includes a plurality of voltage division resistors, and the threshold voltage is adjusted by adjusting the resistance values ​​of the plurality of voltage division resistors.

13. The LED driving circuit according to claim 11, characterized in that: The first transistor is an NPN bipolar transistor.

14. The LED driving circuit according to claim 11, characterized in that: The output unit comprises: A first output resistor is connected in series between a reference voltage and the output node, and the first output resistor obtains the control signal in a voltage form according to the adjustment current.

15. The LED driving circuit according to claim 11, characterized in that: The output unit includes a second transistor and a third transistor, The second transistor and the third transistor form a first current mirror for converting the regulating current into the control signal in current form.

16. The LED driving circuit according to claim 10, characterized in that: The first current subunit, the second current subunit and the third current subunit respectively include: a fourth transistor, a third feedback resistor and a fifth transistor located on a corresponding current path; a third amplifier, configured to drive the fourth transistor according to the voltage sampling signal and a potential of an intermediate node between the fourth transistor and the third feedback resistor; and a fourth amplifier, configured to drive the fifth transistor according to the threshold voltage and a potential of an intermediate node between the fifth transistor and the third feedback resistor.

17. The LED driving circuit according to claim 16, characterized in that: The current generating unit further comprises: a sixth transistor connected in series on the first current path; and a fifth amplifier, wherein the non-inverting input terminal of the fifth amplifier is used to receive the second threshold voltage, the inverting input terminal is connected to the first terminal of the sixth transistor, and the output terminal is connected to the control terminal of the sixth transistor, The fifth amplifier is used for driving the sixth transistor according to the second threshold voltage to limit a current value of the first current.

18. The LED driving circuit according to claim 17, characterized in that: The current generating unit further includes a seventh transistor and an eighth transistor, The seventh transistor and the eighth transistor form a second current mirror, thereby mirroring the second current to the first current path to compensate for the first current.

19. The LED driving circuit according to claim 18, characterized in that: The fourth transistor, the fifth transistor and the sixth transistor are N-type metal oxide semiconductor field effect transistors respectively, The seventh transistor and the eighth transistor are respectively P-type metal oxide semiconductor field effect transistors.

20. The LED driving circuit according to claim 16, characterized in that: The output unit includes ninth to twelfth transistors and a second output resistor, The ninth transistor, the tenth transistor, the eleventh transistor and the twelfth transistor constitute a third current mirror, the power supply end of the third current mirror is connected to the power supply voltage, and the input end is connected to the output node. The second output resistor is connected in series between the reference voltage and the output terminal of the third current mirror. The third current mirror is used to mirror the regulating current to the second output resistor, and the second output resistor obtains the control signal in voltage form according to the regulating current.

21. The LED driving circuit according to claim 20, characterized in that: The ninth transistor and the tenth transistor are P-type metal oxide semiconductor field effect transistors respectively, The eleventh transistor and the twelfth transistor are respectively N-type metal oxide semiconductor field effect transistors.

22. The LED driving circuit according to claim 16, characterized in that: The output unit includes a thirteenth transistor and a fourteenth transistor, The thirteenth transistor and the fourteenth transistor form a fourth current mirror, a power supply end of the fourth current mirror is connected to a power supply voltage, and an input end is connected to the output node, so as to convert the regulating current into the control signal in current form.

23. A control method for an LED driving circuit, for driving an LED lamp according to an input voltage, characterized in that: The control method comprises: generating a control signal according to the input voltage; and adjusting the driving current flowing through the LED lamp according to the control signal to stabilize the output power of the LED lamp within the rated power range, Wherein, adjusting the driving current of the LED lamp according to the control signal comprises: When the input voltage is in the first voltage interval, the control signal controls the driving current to decrease as the input voltage increases. When the input voltage is in a second voltage interval, the control signal controls the driving current to increase as the input voltage increases, and a minimum value of the second voltage interval is equal to a maximum value of the first voltage interval.

24. The control method according to claim 23, characterized in that: Also includes: When the input voltage is in a third voltage interval, the control signal controls the driving current to decrease as the input voltage increases, and a minimum value of the third voltage interval is equal to / greater than a maximum value of the second voltage interval.

25. The control method according to claim 24, characterized in that: The first voltage interval and the second voltage interval are located in a transition interval between a first rated voltage interval and a second rated voltage interval.

26. The control method according to claim 25, characterized in that: Generating a control signal according to the input voltage comprises: Sampling the input voltage to obtain a voltage sampling signal; A regulating current is generated according to the voltage sampling signal, and the control signal in the form of current or voltage is obtained according to the regulating current.

27. The control method according to claim 26, characterized in that: Generating a regulating current according to the voltage sampling signal comprises: Obtaining a first current according to a voltage difference between the voltage sampling signal and a first threshold voltage representing a minimum value of the first voltage interval; and obtain the adjustment current according to the first current, The first current increases as the voltage difference between the voltage sampling signal and the first threshold voltage increases.

28. The control method according to claim 27, characterized in that: The generating a regulating current according to the voltage sampling signal further comprises: Obtaining a second current according to a voltage difference between the voltage sampling signal and a second threshold voltage representing a minimum value of the second voltage interval; and The first current is compensated according to the second current, so that the first current decreases as the voltage difference between the voltage sampling signal and the second threshold voltage increases.

29. The control method according to claim 28, characterized in that: Generating a regulating current according to the voltage sampling signal comprises: Obtaining a third current according to a voltage difference between the voltage sampling signal and a third threshold voltage representing a minimum value of the third voltage interval; and The regulating current is obtained according to the first current and the third current or according to the third current, The third current increases as the voltage difference between the voltage sampling signal and the third threshold voltage increases.

30. The control method according to any one of claims 27 to 29, characterized in that: Generating the regulating current according to the voltage sampling signal also includes setting a voltage dividing module, the voltage dividing module includes a plurality of voltage dividing resistors, and the threshold voltage is adjusted by adjusting the resistance value of the voltage dividing resistors.

31. The control method according to claim 23, characterized in that: It also includes a constant current circuit for adjusting the driving current flowing through the LED lamp according to the control signal.

32. The control method according to claim 31, characterized in that: The control signal is a voltage signal. The constant current circuit adjusts the driving current according to the control signal and the first current sampling signal, and a variation trend of the driving current is the same as a variation trend of the control signal.

33. The control method according to claim 31, characterized in that: The control signal is a current signal, The constant current circuit adjusts the driving current according to the control signal, the reference voltage and the second current sampling signal. The constant current circuit superimposes the control signal on the second current sampling signal, so that the change trend of the drive current is opposite to the change trend of the control signal.

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