CN214315695U

CN214315695U - LED dimming circuit and LED lamp

Info

Publication number: CN214315695U
Application number: CN202120116557.7U
Authority: CN
Inventors: 邓迅升; 吴浩明; 王前前
Original assignee: Shenzhen Sendis Semiconductor Co Ltd
Current assignee: Shenzhen Sendis Semiconductor Co Ltd
Priority date: 2021-01-15
Filing date: 2021-01-15
Publication date: 2021-09-28
Anticipated expiration: 2031-01-15

Abstract

The utility model discloses a LED dimming circuit and a LED lamp, wherein the LED dimming circuit is connected with a LED lamp string and comprises a comparison module, a filtering module and a constant current module which are connected in sequence; the comparison module is used for receiving the first dimming signal, comparing the voltage value of the first dimming signal with a preset reference voltage, and outputting a comparison signal which is related to the duty ratio of the dimming signal and is unrelated to the amplitude of the dimming signal to the filtering module; the filtering module is used for filtering the comparison signal and outputting a second dimming signal to the constant current module; the constant current module is used for adjusting the current flowing through the LED lamp string according to the second dimming signal; the utility model discloses a set up comparison module and combine the filtering module to realize the conversion of PWM signal of adjusting luminance to obtain DIM signal of adjusting luminance relevant, the irrelevant DIM signal of adjusting luminance of range of DIM signal of adjusting luminance and PWM signal of adjusting luminance after having ensured the conversion, and then effectively avoided the influence of the range of PWM signal of adjusting luminance to DIM signal of adjusting luminance.

Description

LED dimming circuit and LED lamp

Technical Field

The utility model relates to a LED technical field, in particular to LED dimmer circuit and LED lamps and lanterns.

Background

The dimming mode of the LED lamp is mainly two, one mode is a PWM dimming mode, and the PWM dimming mode is to realize dimming by controlling the on-off of the current of the LED lamp string by controlling the time width of the high level and the low level of a PWM dimming signal; the other mode is a DIM dimming mode, the DIM dimming mode is specifically to realize dimming by controlling the current flowing through the LED lamp string, the current of the LED lamp string is only related to the amplitude of a DIM dimming signal, and the problem of current distortion does not exist. The existing dimmer for the LED lamp generally adopts a PWM dimming mode, the PWM dimming mode causes wire mesh current distortion through the mode of switching on and off the current of the LED lamp string, the wire mesh current is interfered with a power grid, the problems of excessive conduction, radiation and the like exist, and the PWM dimming mode continuously switches on and off the current of the LED lamp string, so that the LED lamp has stroboflash with the same frequency as the PWM and damages the human eyes.

When the DIM dimming mode is used, in order to be compatible with a PWM (pulse-width modulation) dimmer, the PWM dimming signal is filtered by an RC (resistor-capacitor) filter circuit to obtain the DIM dimming signal, and then the DIM dimming signal is used for controlling the current of the LED lamp string, so that the problem of current distortion of the PWM dimming mode is solved. When the PWM dimming signal is converted into the DIM dimming signal, the amplitude of the DIM dimming signal is also affected by the amplitude of the PWM dimming signal, in addition to the high and low level times of the PWM dimming signal affecting the amplitude of the DIM dimming signal, so that the DIM dimming signal not only changes with the duty ratio signal of the PWM dimming signal, but also changes with the amplitude of the PWM dimming signal, and the DIM dimming signal cannot truly reflect the PWM dimming signal, as shown in fig. 1.

Because the amplitude of the PWM dimming signal influences the DIM dimming signal and further influences the power of the LED lamp, the deviation of the power supply of each dimmer is required to be very small, the amplitude difference of the PWM dimming signal output among the dimmers is small, the power supply of the dimmers is required to adopt a high-precision power supply circuit, the selection of the power supply of the dimmers is limited, and the power supply cost of the dimmers is increased.

Thus, the prior art has yet to be improved and enhanced.

SUMMERY OF THE UTILITY MODEL

In view of the foregoing prior art's weak point, an object of the utility model is to provide a LED dimming circuit and LED lamps and lanterns can effectively solve and after converting PWM dimming signal into DIM dimming signal, DIM dimming signal can not truly reflect PWM dimming signal, and leads to the problem of power deviation and cost increase.

In order to achieve the purpose, the utility model adopts the following technical proposal:

an LED dimming circuit is connected with an LED lamp string and comprises a comparison module, a filtering module and a constant current module which are sequentially connected; the comparison module is used for receiving a first dimming signal, comparing the voltage value of the first dimming signal with a preset reference voltage, and outputting a comparison signal which is related to the duty ratio of the dimming signal and is unrelated to the amplitude of the dimming signal to the filtering module; the filtering module is used for filtering the comparison signal and outputting a second dimming signal to the constant current module; the constant current module is used for adjusting the current flowing through the LED lamp string according to the second dimming signal.

In the LED dimming circuit, the comparison module comprises a comparator and a first voltage source, the positive phase input end of the comparator is connected with the first dimming signal input end, the negative phase input end of the comparator is connected with the anode of the first voltage source, the cathode of the first voltage source is connected with the Vin-signal end, the output end of the comparator is connected with the filtering module, the anode power source end of the comparator is connected with the compensation voltage input end, and the cathode power source end of the comparator is connected with the Vin-signal end.

The LED dimming circuit further comprises a sampling compensation module, and the sampling compensation module is connected with the comparison module; the sampling compensation module is used for sampling the line voltage to obtain a sampling voltage and outputting a compensation voltage to the comparison module according to the sampling voltage.

In the LED dimming circuit, the sampling compensation module comprises a sampling unit and a compensation unit, the sampling unit is connected with the compensation unit, and the compensation unit is connected with the comparison module; the sampling unit is used for outputting the sampling voltage to the compensation unit after sampling the line voltage; the compensation unit is used for outputting the compensation voltage to the comparison module according to the sampling voltage.

In the LED dimming circuit, the sampling unit comprises a first resistor and a second resistor; one end of the first resistor is connected with a Vin + signal end, the other end of the first resistor is connected with one end of the second resistor and the compensation unit, and the other end of the second resistor is connected with a Vin-signal end.

In the LED dimming circuit, the compensation unit comprises a second voltage source, a third voltage source, a first operational amplifier, a second operational amplifier, a first MOS (metal oxide semiconductor) tube, a second MOS tube, a third resistor, a fourth resistor and a fifth resistor;

the positive phase input end of the first operational amplifier is connected with one end of the first resistor and the other end of the second resistor, the negative phase input end of the first operational amplifier is connected with the source electrode of the first MOS tube and one end of the third resistor, the other end of the third resistor is connected with a Vin-signal end, the drain electrode of the first MOS tube is connected with one end of the fourth resistor and the positive phase input end of the second operational amplifier, the output end of the first operational amplifier is connected with the grid electrode of the first MOS tube, the other end of the fourth resistor is connected with the positive electrode of the second voltage source, the negative electrode of the second voltage source is connected with a Vin-signal end, the negative phase input end of the second operational amplifier is connected with one end of the fifth resistor, the source electrode of the second MOS tube and the comparison module, and the other end of the fifth resistor is connected with a Vin-signal end, the drain electrode of the second MOS tube is connected with the anode of a third voltage source, the cathode of the third voltage source is connected with a Vin-signal end, and the output end of the second operational amplifier is connected with the grid electrode of the second MOS tube.

In the LED dimming circuit, the filtering module comprises a sixth resistor and a capacitor; one end of the sixth resistor is connected with the output end of the comparator, the other end of the sixth resistor and one end of the capacitor are both connected with the constant current module, and the other end of the capacitor is connected with a Vin-signal end.

In the LED dimming circuit, the constant current module comprises a third operational amplifier, a third MOS (metal oxide semiconductor) tube and a seventh resistor; the positive phase input end of the third operational amplifier is connected with the other end of the sixth resistor and one end of the capacitor, the negative phase input end of the third operational amplifier is connected with one end of the seventh resistor and the source electrode of the third MOS tube, the drain electrode of the third MOS tube is connected with the negative electrode of the LED lamp string, the grid electrode of the third MOS tube is connected with the output end of the third operational amplifier, and the other end of the seventh resistor is connected with a Vin-signal end.

An LED lamp comprises an LED lamp string and the LED dimming circuit.

Compared with the prior art, the utility model provides a LED dimming circuit and LED lamps and lanterns, LED dimming circuit and LED lamp cluster are connected, including the comparison module, filtering module and the constant current module that connect gradually; the comparison module is used for receiving the first dimming signal, comparing the voltage value of the first dimming signal with a preset reference voltage, and outputting a comparison signal which is related to the duty ratio of the dimming signal and is unrelated to the amplitude of the dimming signal to the filtering module; the filtering module is used for filtering the comparison signal and outputting a second dimming signal to the constant current module; the constant current module is used for adjusting the current flowing through the LED lamp string according to the second dimming signal; the utility model discloses a set up comparison module and combine the filtering module to realize the conversion of PWM signal of adjusting luminance to obtain DIM signal of adjusting luminance relevant, the irrelevant DIM signal of adjusting luminance of range of DIM signal of adjusting luminance and PWM signal of adjusting luminance after having ensured the conversion, and then effectively avoided the influence of the range of PWM signal of adjusting luminance to DIM signal of adjusting luminance.

Drawings

Fig. 1 is a block diagram of a conventional LED dimming circuit;

fig. 2 is a block diagram of an LED dimming circuit provided by the present invention;

fig. 3 is a schematic circuit diagram of a sampling compensation module in the LED dimming circuit provided by the present invention;

fig. 4 is a schematic circuit diagram of a comparison module in the LED dimming circuit provided by the present invention.

Detailed Description

The utility model provides a pair of LED dimmer circuit and LED lamps and lanterns can effectively solve and after the signal conversion that adjusts luminance with PWM adjusts luminance to the DIM signal of adjusting luminance, the DIM signal of adjusting luminance can not truly reflect the PWM signal of adjusting luminance, and leads to the problem of power deviation and cost increase.

In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the following description of the present invention will refer to the accompanying drawings and illustrate embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.

Referring to fig. 2, the LED dimming circuit provided by the present invention is connected to the LED lamp string 100, and the LED dimming circuit includes a comparison module 200, a filtering module 300, and a constant current module 400, which are connected in sequence; the comparison module 200 is configured to receive a first dimming signal, compare a voltage value of the first dimming signal with a preset reference voltage, and output a comparison signal related to a duty ratio of the first dimming signal and unrelated to an amplitude of the first dimming signal to the filtering module 300; in this embodiment, the first dimming signal is a PWM dimming signal, and the PWM dimming signal is provided by the PWM dimmer, that is, the duty ratio and the amplitude of the first dimming signal refer to the duty ratio and the amplitude of the PWM dimming signal; the filtering module 300 is configured to filter the comparison signal and output a second dimming signal to the constant current module 400; constant current module 400 is used for the basis the second signal of adjusting luminance adjusts the flow through the electric current of LED lamp cluster 100, in this embodiment the second signal of adjusting luminance is DIM signal of adjusting luminance, the utility model discloses a set up comparison module 200 combines filter module 300 generate one with the duty cycle of PWM signal of adjusting luminance is relevant and with the irrelevant DIM signal of adjusting luminance of the range of PWM signal of adjusting luminance, effectively avoided the range of PWM signal of adjusting luminance to the influence of DIM signal of adjusting luminance, just so can avoid the influence to LED lamp cluster 100 power, when selecting the power supply of PWM light modulator, can choose for use power supply modes such as low-cost stabilivolt, reduce system cost.

Further, referring to fig. 3, the comparing module 200 includes a comparator CMP and a first voltage source V1, a positive phase input terminal of the comparator CMP is connected to a first dimming signal input terminal, an inverted phase input terminal of the comparator CMP is connected to a positive electrode of the first voltage source V1, a negative electrode of the first voltage source V1 is connected to a Vin-signal terminal, an output terminal of the comparator CMP is connected to the filtering module 300, a positive electrode power source terminal of the comparator CMP is connected to a compensation voltage input terminal, and a negative electrode power source terminal of the comparator CMP is connected to the Vin-signal terminal; the first voltage source V1 provides a preset reference voltage (VREF 1 in this embodiment) for the comparator CMP, the comparator CMP outputs a high level when comparing that the voltage value of the PWM dimming signal is greater than the preset reference voltage, and outputs a low level when comparing that the voltage value of the PWM dimming signal is less than the preset reference voltage, which is equivalent to that the PWM dimming signal passes through the comparator CMP and then outputs a duty ratio signal corresponding to the PWM dimming signal, i.e. a comparison signal, that is, the comparison signal is not related to the amplitude of the PWM dimming signal but related to the duty ratio of the PWM dimming signal, thereby realizing that the subsequent DIM dimming signal is not affected by the amplitude of the PWM dimming signal.

Further, please continue to refer to fig. 2, the LED dimming circuit further includes a sampling compensation module 500, wherein the sampling compensation module 500 is connected to the comparison module 200; the sampling compensation module 500 is configured to sample a line voltage to obtain a sampling voltage, and output a compensation voltage (VREF in this embodiment) to the comparison module 200 according to the sampling voltage, specifically, the sampling compensation module 500 is connected to a positive electrode power source terminal of the comparator CMP; in this embodiment, the line voltage is a difference voltage between a Vin + signal terminal and a Vin-signal terminal, that is, the line voltage is | Vin + -Vin- |, the sampling compensation module 500 provides a compensation voltage for the comparator CMP, when the PWM dimming signal passes through the comparator CMP, a duty ratio signal corresponding to the PWM dimming signal is output, and the amplitude of the duty ratio signal corresponds to the amplitude of the compensation voltage. Since the compensation voltage is obtained by sampling the line voltage, the compensation voltage has no relation with the PWM dimming signal, and even the amplitude of the PWM dimming signal, so that the amplitude of the duty ratio signal output by the comparator CMP has no relation with the amplitude of the PWM dimming signal, and it is ensured that the DIM dimming signal output by the filter module 300 is not affected by the amplitude of the PWM dimming signal.

Further, referring to fig. 4, the sampling compensation module 500 includes a sampling unit 510 and a compensation unit 520, the sampling unit 510 is connected to the compensation unit 520, and the compensation unit 520 is connected to the comparison module 200; the sampling unit 510 is configured to sample the line voltage and output the sampled voltage to the compensation unit 520; the compensation unit 520 is configured to output the compensation voltage to the comparison module 200 according to the sampling voltage; in this embodiment, the sampling unit 510 directly connects the Vin + signal terminal and the Vin-signal terminal, the sampling unit 510 samples voltages input by the Vin + signal terminal and the Vin-signal terminal, that is, line voltages to obtain a sampling voltage related to the line voltages, and then the compensation unit 520 outputs a compensation voltage related to the sampling voltage to the comparator CMP according to the sampling voltage, so that the amplitude of the comparison signal output by the comparator CMP is related to the amplitude of the compensation voltage, which is equivalent to the amplitude of the DIM dimming signal being related to the amplitude of the compensation voltage.

Further, the sampling unit 510 includes a first resistor R1 and a second resistor R2; one end of the first resistor R1 is connected to the Vin + signal end, the other end of the first resistor R1 is connected to one end of the second resistor R2 and the compensation unit 520, and the other end of the second resistor R2 is connected to the Vin-signal end, in this embodiment, the line voltage is divided and sampled through the first resistor R1 and the second resistor R2, and compared with a mode of directly sampling the voltage below the LED light string 100, the current of the LED light string 100 is not affected by the voltage of the LED light string 100. The LED lamp string 100 is formed by connecting a plurality of LED lamp beads in series, the voltage of the LED lamp string 100 is set according to the mains voltage, and the voltage required by the LED lamp string 100 is smaller than the line voltage; if the mode of sampling the voltage below the LED lamp string 100 is selected, in actual use, due to the voltage deviation of each LED lamp bead, the voltages of the LED lamp strings 100 in series with the same number of LED lamp beads are different, so that the compensation voltages obtained between different LED lamps of the same specification are different, and further, the currents of the LED lamp strings 100 are different, which causes a large deviation in power between different LED lamps of the same specification, therefore, the line voltage is directly sampled in this embodiment, the current of the LED lamp string 100 can be effectively prevented from being influenced by the voltage of the LED lamp string 100, and the power between different LED lamps of the same specification is prevented from having a deviation.

Further, the compensation unit 520 includes a second voltage source V2, a third voltage source V3, a first operational amplifier OP1, a second operational amplifier OP2, a first MOS transistor, a second MOS transistor M2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5; a positive input terminal of the first operational amplifier OP1 is connected to one end of the first resistor R1 and the other end of the second resistor R2, a negative input terminal of the first operational amplifier OP1 is connected to a source of the first MOS transistor and one end of the third resistor R3, the other end of the third resistor R3 is connected to a Vin-signal terminal, a drain of the first MOS transistor is connected to one end of the fourth resistor R4 and the positive input terminal of the second operational amplifier OP2, an output terminal of the first operational amplifier OP1 is connected to a gate of the first MOS transistor, the other end of the fourth resistor R4 is connected to a positive terminal of the second voltage source V2, a negative terminal of the second voltage source V2 is connected to the Vin-signal terminal, a negative input terminal of the second operational amplifier OP2 is connected to one end of the fifth resistor R5, a source of the second MOS transistor M2 and the comparison module 200, the other end of the fifth resistor R5 is connected to a Vin-signal terminal, the drain of the second MOS transistor M2 is connected to the anode of the third voltage source V3, the cathode of the third voltage source V3 is connected to the Vin-signal terminal, the output terminal of the second operational amplifier OP2 is connected to the gate of the second MOS transistor M2, in this embodiment, the first MOS transistor M1 and the second MOS transistor M2 are both N-channel MOS transistors, wherein the second voltage source V2 is configured to provide a reference voltage VREF2, and the third voltage source V3 is configured to provide a reference voltage VREF 3.

The sampling voltage obtained by voltage division and sampling through the first resistor R1 and the second resistor R2 is input to the non-inverting input terminal of the first operational amplifier OP1, wherein the first operational amplifier OP1, the first MOS transistor and the third resistor R3 form a constant current source, and the second operational amplifier OP2, the second MOS transistor M2 and the fifth resistor R5 form another constant current source. When the sampling voltage increases with the line voltage, the current flowing through the first MOS transistor and the third resistor R3 increases, then the reference voltage VREF0 input to the non-inverting input terminal of the second operational amplifier OP2 becomes smaller, and the current flowing through the second MOS transistor M2 and the fifth resistor R5 becomes smaller, then the compensation voltage becomes smaller; when the sampling voltage is reduced along with the line voltage, the current flowing through the first MOS transistor and the third resistor R3 is reduced, the reference voltage VREF0 input to the non-inverting input terminal of the second operational amplifier OP2 is increased, the current flowing through the second MOS transistor M2 and the fifth resistor R5 is increased, and then the compensation voltage is increased, that is, the compensation voltage is negatively correlated with the sampling voltage, and since the sampling voltage is positively correlated with the line voltage, then the compensation voltage is negatively correlated with the line voltage; in this embodiment, the sampling compensation module 500 outputs a compensation voltage negatively correlated to the line voltage to the comparator CMP, so that the amplitude of the DIM dimming signal output by the comparator CMP is positively correlated to the amplitude of the compensation voltage; when the line voltage is increased, the sampling voltage is increased, the compensation voltage is decreased, the DIM dimming signal is decreased, and the current of the LED light string 100 is decreased, and when the line voltage is decreased, the sampling voltage is decreased, the compensation voltage is increased, the DIM dimming signal is increased, and the current of the LED light string 100 is increased, so that the power of the LED light string 100 is kept relatively constant when the line voltage is changed.

Further, with continued reference to fig. 3, the filtering module 300 includes a sixth resistor R6 and a capacitor C1; one end of the sixth resistor R6 is connected to the output terminal of the comparator CMP, the other end of the sixth resistor R6 and one end of the capacitor C1 are both connected to the constant current module 400, the other end of the capacitor C1 is connected to a Vin-signal end, in this embodiment, the sixth resistor R6 and the capacitor C1 form an RC filter circuit, and the RC filter circuit filters the duty ratio signal output by the comparator CMP to obtain a DIM dimming signal, because the duty ratio signal corresponds to the duty ratio of the PWM dimming signal, the amplitude of the duty ratio signal corresponds to the amplitude of the compensation voltage, and since the compensation voltage is not related to the amplitude of the PWM dimming signal, the corresponding DIM dimming signal is only related to the duty ratio of the PWM dimming signal, and the amplitude of the PWM dimming signal is irrelevant, so that the influence of the amplitude of the PWM dimming signal on the DIM dimming signal is effectively avoided.

Further, the constant current module 400 includes a third operational amplifier OP3, a third MOS transistor M3, and a seventh resistor R7; a non-inverting input terminal of the third operational amplifier OP3 is connected to the other terminal of the sixth resistor R6 and one terminal of the capacitor C1, an inverting input terminal of the third operational amplifier OP3 is connected to one terminal of the seventh resistor R7 and a source of the third MOS transistor M3, a drain of the third MOS transistor M3 is connected to a cathode of the LED light string 100, a gate of the third MOS transistor M3 is connected to an output terminal of the third operational amplifier OP3, and the other terminal of the seventh resistor R7 is connected to a Vin-signal terminal; in this embodiment, the third MOS transistor M3 is an N-channel MOS transistor, the seventh resistor R7 is configured to set a current flowing through the LED light string 100, specifically, the current Iled flowing through the LED light string 100 is DIM/R7, DIM is a voltage corresponding to a DIM dimming signal, and R7 is a resistance of the seventh resistor R7; the non-inverting input end of the third operational amplifier OP3 is connected to a DIM dimming signal from the conversion module, the amplitude of the DIM dimming signal is the compensation voltage at the power input end of the operational amplifier, and the constant current module 400 controls the current flowing through the LED light string 100 through the amplitude of the DIM dimming signal; that is, when the DIM dimming signal has a high amplitude, the current flowing through the LED string 100 is large, and vice versa.

The utility model provides a LED dimming circuit, on one hand when the line voltage risees, sampling voltage increases, and offset voltage reduces, and the range of DIM dimming signal reduces, and the electric current of LED lamp cluster 100 reduces; when the line voltage is reduced, the sampling voltage is reduced, the compensation voltage is increased, and the amplitude of the DIM dimming signal is increased, so that when the power of the LED lamp string 100 is increased by the alternating-current voltage, the current of the LED lamp string 100 is reduced, and the power is kept relatively constant. On the other hand, when the amplitude of the PWM dimming signal varies in a range greater than VREF1 or more, the DIM dimming signal does not vary with the amplitude of the PWM dimming signal, the current of LED string 100 does not vary, and the power of the LED string does not vary. The DIM signal of adjusting luminance of comparator CMP output only changes along with the duty cycle value of PWM signal of adjusting luminance, and when the duty cycle value increase, the DIM signal of adjusting luminance increases, and LED lamp cluster 100 electric current grow, and when the duty cycle value reduces, the DIM signal of adjusting luminance reduces, and LED lamp cluster 100 electric current reduces, and then realizes that PWM adjusts luminance changes the DIM function of adjusting luminance, solves stroboscopic, conduction radiation scheduling problem that PWM adjusted luminance and arouse. Moreover, the power of the LED light string 100 is not affected by the amplitude of the PWM dimming signal, and when the power supply of the PWM dimmer is selected, power supply modes such as low-cost voltage regulator tubes can be selected, so as to reduce the system cost.

Based on foretell LED dimmer circuit, the utility model discloses still the correspondence provides a LED lamps and lanterns, LED lamps and lanterns include LED lamp cluster and as above LED dimmer circuit, because the above has carried out detailed description to this LED dimmer circuit, no longer gives unnecessary details here.

To sum up, the utility model provides a LED dimming circuit and LED lamp, the LED dimming circuit is connected with the LED lamp string, including the comparison module, the filtering module and the constant current module which are connected in sequence; the comparison module is used for receiving the first dimming signal, comparing the voltage value of the first dimming signal with a preset reference voltage, and outputting a comparison signal which is related to the duty ratio of the dimming signal and is unrelated to the amplitude of the dimming signal to the filtering module; the filtering module is used for filtering the comparison signal and outputting a second dimming signal to the constant current module; the constant current module is used for adjusting the current flowing through the LED lamp string according to the second dimming signal; the utility model discloses a set up comparison module and combine the filtering module to realize the conversion of PWM signal of adjusting luminance to obtain DIM signal of adjusting luminance relevant, the irrelevant DIM signal of adjusting luminance of range of DIM signal of adjusting luminance and PWM signal of adjusting luminance after having ensured the conversion, and then effectively avoided the influence of the range of PWM signal of adjusting luminance to DIM signal of adjusting luminance.

It should be understood that equivalent alterations and modifications can be made by those skilled in the art according to the technical solution of the present invention and the inventive concept thereof, and all such alterations and modifications should fall within the scope of the appended claims.

Claims

1. An LED dimming circuit is connected with an LED lamp string and is characterized by comprising a comparison module, a filtering module and a constant current module which are sequentially connected; the comparison module is used for receiving a first dimming signal, comparing the voltage value of the first dimming signal with a preset reference voltage, and outputting a comparison signal which is related to the duty ratio of the dimming signal and is unrelated to the amplitude of the dimming signal to the filtering module; the filtering module is used for filtering the comparison signal and outputting a second dimming signal to the constant current module; the constant current module is used for adjusting the current flowing through the LED lamp string according to the second dimming signal.

2. The LED dimming circuit of claim 1, wherein the comparison module comprises a comparator and a first voltage source, a positive input terminal of the comparator is connected to the first dimming signal input terminal, a negative input terminal of the comparator is connected to a positive terminal of the first voltage source, a negative terminal of the first voltage source is connected to the Vin-signal terminal, an output terminal of the comparator is connected to the filtering module, a positive power source terminal of the comparator is connected to the compensation voltage input terminal, and a negative power source terminal of the comparator is connected to the Vin-signal terminal.

3. The LED dimming circuit of claim 1, further comprising a sampling compensation module, the sampling compensation module being coupled to the comparison module; the sampling compensation module is used for sampling the line voltage to obtain a sampling voltage and outputting a compensation voltage to the comparison module according to the sampling voltage.

4. The LED dimming circuit of claim 3, wherein the sampling compensation module comprises a sampling unit and a compensation unit, the sampling unit is connected with the compensation unit, and the compensation unit is connected with the comparison module; the sampling unit is used for outputting the sampling voltage to the compensation unit after sampling the line voltage; the compensation unit is used for outputting the compensation voltage to the comparison module according to the sampling voltage.

5. The LED dimming circuit of claim 4, wherein the sampling unit comprises a first resistor and a second resistor; one end of the first resistor is connected with a Vin + signal end, the other end of the first resistor is connected with one end of the second resistor and the compensation unit, and the other end of the second resistor is connected with a Vin-signal end.

6. The LED dimming circuit of claim 5, wherein the compensation unit comprises a second voltage source, a third voltage source, a first operational amplifier, a second operational amplifier, a first MOS transistor, a second MOS transistor, a third resistor, a fourth resistor and a fifth resistor;

7. The LED dimming circuit of claim 2, wherein the filtering module comprises a sixth resistor and a capacitor; one end of the sixth resistor is connected with the output end of the comparator, the other end of the sixth resistor and one end of the capacitor are both connected with the constant current module, and the other end of the capacitor is connected with a Vin-signal end.

8. The LED dimming circuit of claim 7, wherein the constant current module comprises a third operational amplifier, a third MOS transistor and a seventh resistor; the positive phase input end of the third operational amplifier is connected with the other end of the sixth resistor and one end of the capacitor, the negative phase input end of the third operational amplifier is connected with one end of the seventh resistor and the source electrode of the third MOS tube, the drain electrode of the third MOS tube is connected with the negative electrode of the LED lamp string, the grid electrode of the third MOS tube is connected with the output end of the third operational amplifier, and the other end of the seventh resistor is connected with a Vin-signal end.

9. An LED lamp comprising an LED string, characterized by further comprising the LED dimming circuit of any one of claims 1-8.