LED driving circuit and LED lamp

Abstract

The present invention discloses an LED driving circuit and an LED lamp, wherein the LED driving circuit comprises at least two mutually cascaded LED light strips, a first switch tube, and at least one cascade driving circuit; at least two cascaded LED light strips, the input end of the first switch tube, and the output end of the first switch tube are connected in series between the positive and negative poles of a power supply; the enable end of the first switch tube is connected to the drive signal output end of a PWM signal generator; and the cascade driving circuit is connected between every two LED light strips. The LED driving circuit of the present invention can be driven and lit at the same time by arranging a cascade driving circuit between every two mutually connected LED light strips, and the circuit structure is simple and easy to implement.

Description

Technical Field

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

[0002] At present, the length of LED light strips on the market is generally several meters. They are made up of multiple strings of LED lamp beads connected in parallel. Each string has multiple LED lamp beads in series and is driven and lit by a controller. In some special occasions, such as when arranging the lighting in the living room during home decoration, it is necessary to cascade several light strips, and it is necessary to drive multiple light strips in the cascade to light up or extinguish at the same time. During the research process, the applicant found that if the same controller is used to drive multiple cascaded light strips, there will be a problem of insufficient driving power, resulting in the light strip connected to the rear end not being able to light up normally. If each light strip is driven by a corresponding controller, there is the problem of how to control it synchronously, and the use of multiple controllers will cause the circuit structure to be complicated and the cost to be high. Summary of the invention

[0003] Based on this, an object of the present invention is to provide an LED driving circuit and an LED lamp, wherein the LED driving circuit has a simple circuit structure and can simultaneously drive multiple cascaded light strips to work normally.

[0004] According to a first aspect of the present invention, there is provided an LED driving circuit, comprising at least two mutually cascaded LED light strips, a first switch tube, and at least one cascade driving circuit; the at least two cascaded LED light strips, the input end of the first switch tube, and the output end of the first switch tube are connected in series between the positive and negative poles of a power supply; the enable end of the first switch tube is connected to the drive signal output end of a PWM signal generator; the cascade driving circuit is connected between every two LED light strips; the cascade driving circuit comprises a photocoupler, a first resistor and a second switch tube; the photocoupler comprises a light emitting diode and a phototransistor; the light emitting diode is connected in series with the first resistor and then connected in parallel between the positive and negative poles of the LED light strip of the previous stage; the LED light strip of the next stage, the input end of the second switch tube, and the output end of the second switch tube are connected in series between the positive and negative poles of the power supply; the enable end of the second switch tube is connected to the positive pole of the power supply through the output end of the phototransistor and the input end of the phototransistor;

[0005] When the LED light strip of the previous level is lit, the light-emitting diode of the photocoupler is also lit, the photosensitive transistor of the photocoupler receives the light signal and turns on, the enable end of the second switch tube is connected to the positive pole of the power supply via the photosensitive transistor and turns on after receiving power, and the LED light strip of the next level is connected in series between the positive and negative poles of the power supply to form a power-on loop and is thus lit; when the LED light strip of the previous level is turned off, the light-emitting diode of the photocoupler is turned off at the same time, the photosensitive transistor of the photocoupler cannot receive the light signal and is turned off, the enable end of the second switch tube cannot be connected to the positive pole of the power supply and loses power and turns off, and the negative pole of the LED light strip of the next level cannot be connected to GND and cannot form a power-on loop and is thus turned off.

[0006] The LED driving circuit of the present invention provides a cascade driving circuit between every two LED light strips that are connected to each other, so that each LED light strip can be driven and lit at the same time, and the circuit structure is simple and easy to implement.

[0007] In an optional embodiment, the cascade drive circuit also includes a second resistor and a third resistor; the enable end of the second switch tube is connected to the output end of the phototransistor through the second resistor; and the third resistor is connected in parallel between the enable end and the output end of the second switch tube.

[0008] In an optional embodiment, the cascade drive circuit further includes a push-pull circuit; the push-pull circuit includes a third switch tube, a fourth switch tube, a fourth resistor, a fifth resistor and a sixth resistor; the third switch tube and the fourth switch tube have opposite polarities;

[0009] The enable end of the second switch tube is connected to the positive electrode of the power supply via the output end of the third switch tube and the output end of the third switch tube, and the enable end of the second switch tube is grounded via the input end of the fourth switch tube and the output end of the fourth switch tube;

[0010] The enable terminal of the third switch tube is connected to the positive electrode of the power supply via a fourth resistor;

[0011] The enable terminal of the fourth switch tube is connected to the node where the third switch tube and the fourth resistor are connected via a fifth resistor, and the enable terminal of the fourth switch tube is connected to the input terminal of the phototransistor via a sixth resistor;

[0012] The output end of the second switch tube, the output end of the fourth switch tube, and the output end of the phototransistor are connected to each other and then grounded.

[0013] In an optional embodiment, the third switch tube is an NPN transistor, the input end of the third switch tube is the collector of the transistor, the output end of the third switch tube is the emitter of the transistor, and the enable end of the third switch tube is the base of the transistor.

[0014] In an optional embodiment, the fourth switch tube is a PNP type transistor, the input end of the fourth switch tube is the emitter of the transistor, the output end of the fourth switch tube is the collector of the transistor, and the enable end of the fourth switch tube is the base of the transistor.

[0015] In an optional embodiment, the first switch tube is an N-channel field effect tube, the input end of the first switch tube is the drain of the field effect tube, the output end of the first switch tube is the source of the field effect tube, and the enable end of the first switch tube is the gate of the field effect tube.

[0016] In an optional embodiment, the second switch tube is an N-channel field effect tube, the input end of the second switch tube is the drain of the field effect tube, the output end of the second switch is the source of the field effect tube, and the enable end of the second switch tube is the gate of the field effect tube.

[0017] In an optional embodiment, the LED driving circuit also includes a power supply; the power supply includes at least two independent branch power supplies; the branch power supplies correspond one-to-one to the LED light strips, and each LED light strip is connected in series between the positive and negative poles of the corresponding power supply.

[0018] According to a second aspect of the present invention, there is provided an LED lamp, comprising an LED driving circuit and a PWM signal generator as described in any one of the above items; an enable end of a first switch tube of the LED driving circuit is connected to the PWM signal generator to receive a PWM driving signal; the power supply has an AC input end and a plurality of DC power output ends, wherein the AC input end is connected to an AC mains power source, and the plurality of DC output ends are respectively connected to each LED light strip.

[0019] By applying the technical solution of the present invention, a cascade driving circuit is provided between each two LED light strips connected to each other, so that each LED light strip can be driven and lit at the same time, and the circuit structure is simple and easy to implement. Furthermore, an independent power supply is provided for each LED light strip to prevent the LED light strip connected to the rear end from having a dim brightness due to a voltage drop problem.

[0020] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1is a circuit structure diagram of an LED driving circuit according to an embodiment of the present invention;

[0022] Figure 2 is a circuit structure diagram of the LED driving circuit described in Embodiment 1 of the present invention;

[0023] Figure 3 is a schematic diagram of the circuit structure of the cascade drive circuit described in Embodiment 1 of the present invention;

[0024] Figure 4 is a circuit structure diagram of the cascade drive circuit described in Embodiment 2 of the present invention;

[0025] Figure 5 It is a schematic diagram of the structure of the LED lamp according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will now be more fully described with reference to the accompanying drawings in the text which follow, in which embodiments of the present invention are shown. However, the present invention may be embodied in a variety of different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are intended to convey the scope of the present invention to those skilled in the art.

[0027] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0028] Several specific embodiments are given below to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0029] A general LED light strip is made up of multiple strings of LED lamp beads connected in parallel, each string has multiple LED lamp beads connected in series, and is driven and lit by a controller. In some special occasions, such as when decorating the living room lighting, it is necessary to cascade several light strips, and drive multiple light strips in the cascade to light up or extinguish at the same time. If the same controller is used to drive multiple cascaded light strips, there will be a problem of insufficient driving power, resulting in the light strip connected to the back end not being able to light up normally. If each light strip is driven by a corresponding controller, there is a problem of how to control it synchronously, and the use of multiple controllers will cause the circuit structure to be complicated and the cost to be high.

[0030] In view of the above technical problem, a first aspect of the present invention provides an LED driving circuit.

[0031] See also Figure 1 and Figure 2 , Figure 1 is a circuit structure diagram of an LED driving circuit according to an embodiment of the present invention; Figure 2 Schematic diagram of the circuit structure of the LED driving circuit according to the first embodiment of the present invention.

[0032] The LED driving circuit includes a power supply 10, at least two mutually cascaded LED light strips, a first switch tube 30, and at least one cascade driving circuit; two cascaded LED light strips, an input end of the first switch tube 30, and an output end of the first switch tube 30 are connected in series between the positive and negative electrodes of the power supply 10; an enable end of the first switch tube 30 is connected to a driving signal output end of a PWM signal generator 50; and the cascade driving circuit is connected between every two LED light strips.

[0033] Specifically, the plurality of sequentially cascaded LED light strips are respectively a first LED light strip 21, a second LED light strip 22 and a third LED light strip 23. The power supply provides a DC power supply to each LED light strip. The cascade drive circuit 41 is connected between the first LED light strip 21 and the second LED light strip 22, and the cascade drive circuit 42 is connected between the second LED light strip 22 and the third LED light strip 23.

[0034] The power supply 10 can provide a DC power supply of +5V to +24V or even higher voltage for the LED light strip, and the required working voltage of each LED light string may be different. The required working voltage of each LED light string is determined according to the number of lamp beads connected in series on each LED light string. The more lamp beads connected in series, the higher the required voltage. For example, when there are 3 lamp beads connected in series on each light string, the required working voltage of the light string may be +12V, when there are 6 lamp beads connected in series on each light string, the required working voltage of the light string may be +24V, and when there are more lamp beads connected in series on each light string, the required working voltage of the light string is higher.

[0035] The LED light strip includes a plurality of LED light strings connected in parallel, each LED light string having a plurality of lamp beads connected in series. In this embodiment, three LED light strips connected in cascade may be included, such as a first LED light strip 21 , a second LED light strip 22 and a third LED light strip 23 .

[0036] The first switch tube 30 can be a switch device such as a triode or a field effect tube.

[0037] The cascade driving circuit includes a first cascade driving circuit 41 and a second cascade driving circuit 42 .

[0038] See also Figure 3 , Figure 3Schematic diagram of the circuit structure of the cascade driving circuit according to an embodiment of the present invention.

[0039] The cascade drive circuit includes a photocoupler U1, a first resistor R1 and a second switch tube Q2; the photocoupler U1 includes a light-emitting diode and a phototransistor integrated in a housing; the light-emitting diode is connected in series with the first resistor R1 and then connected in parallel between the positive electrode VCC and the negative electrode GND of the LED light strip of the previous stage; the LED light strip of the next stage, the input end of the second switch tube Q2, and the output end of the second switch tube Q2 are connected in series between the positive electrode VCC and the negative electrode GND of the power supply; the enable end of the second switch tube Q2 is connected to the positive electrode VCC of the power supply through the output end of the phototransistor and the input end of the phototransistor. The second switch tube Q2 can be a switching device such as a transistor or a field effect tube.

[0040] The working principle of the embodiment of the present invention is:

[0041] The following working principle is described by taking the first switch tube Q1 as an N-channel field effect tube and the second switch tube Q2 as an N-channel field effect tube as an example. The input end of the first switch tube Q1 is the drain D of the field effect tube, the output end of the first switch tube Q1 is the source S of the field effect tube, the enable end of the first switch tube Q1 is the gate G of the field effect tube, and the first switch tube Q1 is turned on when the voltage difference between Vg and Vs of the first switch tube Q1 is greater than the turn-on voltage of the first switch tube Q1. The input end of the second switch tube Q2 is the drain D of the field effect tube, the output end of the second switch tube Q2 is the source S of the field effect tube, the enable end of the second switch tube Q2 is the gate G of the field effect tube, and the second switch tube Q2 is turned on when the voltage difference between Vg and Vs of the second switch tube Q2 is greater than the turn-on voltage of the second switch tube Q2.

[0042] When the enable end of the first switch tube Q1, that is, the gate G of the first switch tube Q1, receives a high-level driving signal from the PWM signal generator, the voltage difference between Vg and Vs is greater than the turn-on voltage of the first switch tube Q1, and the first LED light strip 21 is turned on, so that the first LED light strip 21 is connected in series between the positive and negative poles of the power supply to form a power-on loop, and the first LED light strip 21 is lit; when the enable end of the first switch tube Q1 receives a low-level driving signal from the PWM signal generator, the voltage difference between Vg and Vs is less than the turn-on voltage of the first switch tube Q1, and the first LED light strip 21 is turned off, so that the negative pole of the first LED light strip 21 cannot be connected to GND, and a power-on loop cannot be formed, and the first LED light strip 21 is extinguished. Therefore, the high and low levels of the PWM driving signal can be used to drive the first LED light strip to be on or off.

[0043] After the light-emitting diode of the photocoupler U1 in the cascade drive circuit is connected in series with the first resistor R1, it is connected in parallel between the positive electrode S+ and the negative electrode S- of the first LED light strip 21. When the first LED light strip 21 is lit, the light-emitting diode of the photocoupler U1 is also lit, and the photosensitive transistor of the photocoupler U1 can receive the light signal and turn on. At this time, the enable end of the second switch tube Q2 of the second LED light strip 22 is connected to the positive electrode VCC of the power supply through the photosensitive transistor to obtain power, so that the voltage difference between Vg and Vs of the second switch tube Q2 is greater than the conduction voltage of the second switch tube Q2, and the second LED light strip 22 is connected in series between the positive and negative electrodes of the power supply to form a power-on circuit, and the second LED light strip 22 is lit. When the first LED light strip 21 is turned off, the light-emitting diode of the photocoupler U1 is also turned off, and the photosensitive transistor of the photocoupler U1 cannot receive the light signal and is turned off. At this time, the enable end of the second switch tube Q2 of the second LED light strip 22 cannot be connected to the positive electrode VCC of the power supply and loses power, so that the voltage difference between Vg and Vs of the second switch tube Q2 is less than the turn-on voltage of the second switch tube Q2 and is turned off. The negative electrode of the second LED light strip 22 cannot be connected to GND and cannot form a power-on circuit, and the second LED light strip 22 is extinguished.

[0044] Through the above control method, the second LED light strip 22 and the first LED light strip 21 can be lit or extinguished at the same time. Similarly, the third LED light strip 23 connected to the rear end of the second LED light strip 22 can also be lit or extinguished at the same time, thereby realizing the synchronous control of multiple cascaded LED light strips by one controller.

[0045] The LED driving circuit of the present invention provides a cascade driving circuit between every two LED light strips that are connected to each other, so that each LED light strip can be driven and lit at the same time, and the circuit structure is simple and easy to implement.

[0046] In an optional embodiment, since the voltage of the gate G of the second switch tube Q2 is limited, that is, there is a rated voltage, in general, the DC voltage provided by the power supply will be higher than the rated voltage of the second switch tube Q2. In order to protect the second switch tube Q2 from being damaged by the high voltage, a voltage-dividing resistor is also connected to the gate G of the second switch tube Q2. The voltage-dividing resistor includes a second resistor R2 and a third resistor R3; the enable end of the second switch tube Q2 is connected to the output end of the phototransistor through the second resistor R2; the third resistor R3 is connected in parallel between the enable end and the output end of the second switch tube Q2.

[0047] When the second switch tube Q2 is a MOS tube, due to the influence of the junction capacitance Ciss of the MOS tube, there is a short delay in the opening and closing of the MOS tube. The specific delay time is related to the characteristics of the MOS tube used. If the frequency of the PWM drive signal is relatively high, or multiple light strips are connected, it is necessary to speed up the switching time of the MOS tube. Therefore, in an optional embodiment, the cascade drive circuit also includes a push-pull circuit. The push-pull circuit needs to be composed of two switch tubes with opposite polarities and the same parameters. They exist in the circuit in a push-pull manner, each responsible for the waveform amplification task of the positive and negative half cycles. When the circuit is working, only one of the two symmetrical power switch tubes is turned on at a time, and the conduction loss is small and the efficiency is high.

[0048] See also Figure 4 , Figure 4 Schematic diagram of the circuit structure of the cascade driving circuit according to the second embodiment of the present invention.

[0049] The push-pull circuit includes a third switch tube Q3, a fourth switch tube Q4, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6; the third switch tube Q3 and the fourth switch tube Q4 have opposite polarities; the enable end of the second switch tube Q2 is connected to the positive electrode VCC of the power supply via the output end of the third switch tube Q3 and the output end of the third switch tube Q3, and the enable end of the second switch tube Q2 is grounded via the input end of the fourth switch tube Q4 and the output end of the fourth switch tube Q4; the enable end of the third switch tube Q3 is connected to the positive electrode VCC of the power supply via the fourth resistor R4; the enable end of the fourth switch tube Q4 is connected to the node where the third switch tube Q3 and the fourth resistor R4 are connected via the fifth resistor R5, and the enable end of the fourth switch tube Q4 is connected to the input end of the phototransistor via the sixth resistor R6. The output end of the second switch tube Q2, the output end of the fourth switch tube Q4, and the output end of the phototransistor are connected to each other and then grounded.

[0050] In an optional embodiment, the third switch tube Q3 is an NPN transistor, the input end of the third switch tube Q3 is the collector C of the transistor Q3, the output end of the third switch tube Q3 is the emitter E of the transistor, and the enable end of the third switch tube Q3 is the base B of the transistor. The fourth switch tube Q4 is a PNP transistor, the input end of the fourth switch tube Q4 is the emitter E of the transistor, the output end of the fourth switch tube Q4 is the collector C of the transistor, and the enable end of the fourth switch tube Q4 is the base B of the transistor.

[0051] If the fourth switch tube Q4 is turned off when the third switch tube Q3 is turned on, and if the fourth switch tube Q4 is turned on when the third switch tube Q3 is turned off, that is, when the third switch tube Q3 and the fourth switch tube Q4 are in the same state, only one is turned on and the other is turned off. The conduction loss is small and the efficiency is high, which can solve the delay problem of the switch tube and enable the LED light strips at the rear end to be lit at the same time.

[0052] The working principle is: when the phototransistor of the photocoupler U1 receives the light signal and turns on, if the third switch tube Q3 is turned on and the fourth switch tube Q4 is turned off, the second switch tube Q2 is connected to the positive pole of the power supply via the third switch tube Q3 to obtain power, and the second switch tube Q2 is turned on, so that the LED light strip is connected in series between the positive and negative poles of the corresponding power supply to form a power-on loop, and the LED light strip is lit. When the third switch tube Q3 is turned on and the fourth switch tube Q4 is turned off, R4, R5 and R6 form a voltage-dividing resistor, which can reduce the power supply voltage to the voltage range that the third switch tube Q3 and the second switch tube Q2 can withstand, so as to protect the second switch tube Q2 and the third switch tube Q3 from being burned out.

[0053] When the phototransistor of the optocoupler U1 receives the light signal and turns on, if the fourth switch tube Q4 turns on, the third switch tube Q3 turns off, and the second switch tube Q2 is connected to the positive pole of the power supply via the fourth switch tube Q4, the fifth resistor R5, and the fourth resistor R4 to obtain power, and the second switch tube Q2 turns on, so that the LED light strip is connected in series between the positive and negative poles of the corresponding power supply to form a power-on loop, and the LED light strip is lit. When the third switch tube Q3 turns off and the fourth switch tube Q4 turns on, R4, R5, and R6 form a voltage-dividing resistor, which can reduce the power supply voltage to the voltage range that the fourth switch tube Q4 and the second switch tube Q2 can withstand, so as to protect the second switch tube Q2 and the fourth switch tube Q4 from being burned out.

[0054] In an optional embodiment, the power supply 10 includes at least two independent sub-power supplies, both of which can provide the working voltage when the LED light strip is working normally; the sub-power supplies correspond to the LED light strips one by one, and each LED light strip is connected in series between the positive and negative electrodes of the corresponding sub-power supplies. For example, the sub-power supply 11 provides power for the first LED light strip 21, the sub-power supply 12 provides power for the second LED light strip 22, and the sub-power supply 13 provides power for the third LED light strip 23. Through the distributed power supply scheme, that is, powering each LED light strip through an independent sub-power supply, the voltage drop between each cascaded LED light strip can be eliminated, so that each LED light strip can be lit to normal brightness.

[0055] The LED driving circuit of the embodiment of the present invention can drive and light up all LED light strips at the same time by setting a cascade driving circuit between each two LED light strips connected to each other, and the circuit structure is simple, easy to implement, and low in cost. Furthermore, an independent power supply is set for each LED light strip to prevent the LED light strip connected to the rear end from having a dim brightness due to a voltage drop problem.

[0056] According to a second aspect of the present invention, an LED lamp is provided.

[0057] See also Figure 5 , Figure 5 It is a schematic diagram of the structure of the LED lamp described in the embodiment of the present invention.

[0058] The LED lamp includes an LED driving circuit and a PWM signal generator 50 as described in any one of the above embodiments; the enable end of the first switch tube Q1 of the LED driving circuit is connected to the PWM signal generator 50 to receive a PWM driving signal; the power supply 10 has an AC input end and a plurality of DC power output ends, wherein the AC input end is connected to the AC mains, and the plurality of DC output ends are respectively connected to each LED light strip to provide power.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An LED driving circuit, characterized in that: It comprises at least two mutually cascaded LED light strips, a first switch tube, and at least one cascade drive circuit; At least two cascaded LED light strips, the input end of the first switch tube, and the output end of the first switch tube are connected in series between the positive electrode and the negative electrode of the power supply; The enable terminal of the first switch tube is connected to the drive signal output terminal of the PWM signal generator; The cascade driving circuit is connected between every two LED light strips; The cascade drive circuit includes a photoelectric coupler, a first resistor and a second switch tube; the photoelectric coupler includes a light emitting diode and a phototransistor; The light emitting diode is connected in series with the first resistor and then connected in parallel between the positive electrode and the negative electrode of the LED light strip of the previous stage; The LED light strip of the next stage, the input end of the second switch tube, and the output end of the second switch tube are connected in series between the positive electrode and the negative electrode of the power supply; The enable end of the second switch tube is connected to the positive electrode of the power supply through the output end of the phototransistor and the input end of the phototransistor; When the LED light strip of the previous stage is lit, the light-emitting diode of the photocoupler is lit at the same time, the photosensitive transistor of the photocoupler receives the light signal and turns on, the enable end of the second switch tube is connected to the positive electrode of the power supply via the photosensitive transistor and then turns on, and the LED light strip of the next stage is connected in series between the positive and negative electrodes of the power supply to form a power-on loop and is thus lit; When the LED light strip of the previous stage is turned off, the light-emitting diode of the photocoupler is turned off at the same time, the photosensitive transistor of the photocoupler cannot receive the light signal and is cut off, the enable end of the second switch tube cannot be connected to the positive pole of the power supply and loses power and is turned off, and the negative pole of the LED light strip of the next stage cannot be connected to GND and cannot form a power-on circuit and is turned off.

2. The LED driving circuit according to claim 1, characterized in that: The cascade drive circuit also includes a second resistor and a third resistor; the enable end of the second switch tube is connected to the output end of the phototransistor through the second resistor; and the third resistor is connected in parallel between the enable end and the output end of the second switch tube.

3. The LED driving circuit according to claim 1, characterized in that: The cascade drive circuit also includes a push-pull circuit; the push-pull circuit includes a third switch tube, a fourth switch tube, a fourth resistor, a fifth resistor and a sixth resistor; the third switch tube and the fourth switch tube have opposite polarities; The enable end of the second switch tube is connected to the positive electrode of the power supply via the output end of the third switch tube and the output end of the third switch tube, and the enable end of the second switch tube is grounded via the input end of the fourth switch tube and the output end of the fourth switch tube; The enable terminal of the third switch tube is connected to the positive electrode of the power supply via a fourth resistor; The enable terminal of the fourth switch tube is connected to the node where the third switch tube and the fourth resistor are connected via the fifth resistor, and the enable terminal of the fourth switch tube is connected to the input terminal of the phototransistor via the sixth resistor; The output end of the second switch tube, the output end of the fourth switch tube, and the output end of the phototransistor are connected to each other and then grounded.

4. The LED driving circuit according to claim 3, characterized in that: The third switch tube is an NPN transistor, the input end of the third switch tube is the collector of the transistor, the output end of the third switch tube is the emitter of the transistor, and the enable end of the third switch tube is the base of the transistor.

5. The LED driving circuit according to claim 4, characterized in that: The fourth switch tube is a PNP type transistor, the input end of the fourth switch tube is the emitter of the transistor, the output end of the fourth switch tube is the collector of the transistor, and the enable end of the fourth switch tube is the base of the transistor.

6. The LED driving circuit according to claim 1, characterized in that: The first switch tube is an N-channel field effect tube, the input end of the first switch tube is the drain of the field effect tube, the output end of the first switch tube is the source of the field effect tube, and the enable end of the first switch tube is the gate of the field effect tube.

7. The LED driving circuit according to claim 1, characterized in that: The second switch tube is an N-channel field effect tube, the input end of the second switch tube is the drain of the field effect tube, the output end of the second switch is the source of the field effect tube, and the enable end of the second switch tube is the gate of the field effect tube.

8. The LED driving circuit according to claim 1, characterized in that: The LED driving circuit also includes a power supply; the power supply includes at least two independent branch power supplies; the branch power supplies correspond to the LED light strips one by one, and each LED light strip is connected in series between the positive and negative poles of the corresponding power supply.

9. An LED lamp, characterized in that: It comprises an LED driving circuit and a PWM signal generator as described in any one of claims 1 to 8; the enable end of the first switch tube of the LED driving circuit is connected to the PWM signal generator to receive a PWM driving signal; the power supply has an AC input end and a plurality of DC power output ends, the AC input end is connected to the AC mains, and the plurality of DC output ends are respectively connected to each LED light strip.

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