LED dimming circuit, LED driving system and electronic equipment

Abstract

The present invention discloses an LED dimming circuit, an LED driving system and an electronic device. The dimming input voltage is judged by a first comparison module and a second comparison module, and a suitable signal output is selected by a selection module according to the judgment result. When the dimming input voltage is lower than the first threshold voltage, a relatively accurate dimming signal can be output through a voltage divider module, thereby avoiding the problem that the current flowing through the LED is not accurate when the input voltage Vref_Dim is low due to the existence of the offset voltage Vos of the operational amplifier of the existing LED dimming circuit and the LED lamp brightness cannot meet the index requirements of the dimming accuracy. The technical solution of the present invention can improve the LED dimming accuracy and meet the demand for high-precision dimming.

Description

Technical Field

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

[0002] LED lighting technology has gradually become popular and has become the mainstream lighting technology due to its low power consumption, long life and high luminous efficiency. At the same time, due to its fast response speed and the fact that the luminous intensity is proportional to the driving current, LED dimming technology has basic application conditions.

[0003] Please refer to Figure 1 An existing LED dimming circuit includes: an input resistor R0, a voltage stabilizing diode Z, an operational amplifier OPA, an offset voltage source Vos, a switch tube Mo (P type), a resistor R1, a resistor R2 and an error amplifier EA, wherein a dimming input voltage Vref_Dim is input into the LED dimming circuit from one end of the resistor R0, the other end of the resistor R0 is grounded via the cathode and anode of the voltage stabilizing diode Z in sequence, and the other end of the resistor R0 is also connected to the positive input end of the operational amplifier OPA, the output end of the operational amplifier OPA is connected to the gate of the switch tube M0, the switch tube M0, the resistor R1, and the resistor R2 are connected in series between the working voltage Vdd and the ground in sequence, one end of the offset voltage source Vos is connected to the reverse input end of the operational amplifier OPA, and the other end is connected to the series node of the switch tube M0 and the resistor R1, the series node of the resistor R1 and the resistor R2 is connected to the positive input end of the error amplifier EA and inputs a voltage Vp to the error amplifier EA, and a curve of the voltage Vp changing with the dimming input voltage Vref_Dim is as shown in FIG. Figure 2 As shown; the reverse input terminal of the error amplifier EA is connected to a feedback terminal FB, and the feedback voltage Vfb connected to the feedback terminal FB is related to the dimming input voltage Vref_Dim. The output terminal Out of the error amplifier EA transmits a dimming signal to the corresponding LED, and the LED is usually connected to the ground through an external resistor Rfb (not shown) in series. By adjusting the resistance value of the external resistor Rfb, the current flowing through the LED can be set. That is: I_Led=Vfb / Rfb, usually Vfb=0~0.4V, Vfb=K*Vref_Dim, Vref_Dim is usually in the range of 0~5V.

[0004] When Vref_Dim is greater than 2.5V, Vfb=Vp=0.4V, and the error of Vfb voltage is:

[0005] ;

[0006] When Vref_Dim is in the range of 0~Vk (where Vk<0.8V), Vfb=Vp, which is 0~0.4V; the error of Vfb voltage is:

[0007] ;

[0008] From the relationship between Accuracy1_Vfb and Accuracy2_Vfb, it can be seen that Accuracy2_Vfb determines the size of the final error.

[0009] If Vk=0.8V, assuming Vos=8mV, the final error is: ;

[0010] If Vk=0.1V, assuming Vos=8mV, the final error is: .

[0011] use Figure 1 When the LED dimming circuit structure shown is used to implement LED dimming, since the offset voltage Vos of its operational amplifier OPA always exists and its size is uncertain, when the input voltage Vref_Dim is low, the current flowing through the LED will be inaccurate, and the brightness of the LED lamp cannot meet the dimming accuracy index requirements, resulting in the failure to meet the needs of high-precision LED dimming. Summary of the invention

[0012] The present invention aims to provide an LED dimming circuit, an LED driving system and an electronic device using the same, which can avoid the problem that the offset voltage Vos of the operational amplifier of the existing LED dimming circuit is always present and has an uncertain size, resulting in inaccurate current flowing through the LED when the input voltage Vref_Dim is low and the brightness of the LED lamp cannot meet the dimming accuracy index requirements.

[0013] To achieve the above object, the present invention provides an LED dimming circuit, comprising:

[0014] A first comparison module for determining whether a dimming input voltage is less than a first threshold voltage;

[0015] A second comparison module for determining whether the dimming input voltage is greater than a second threshold voltage;

[0016] An effective input signal generating module for generating a corresponding effective input signal according to the judgment results of the first comparing module and the second comparing module;

[0017] An output module for outputting a dimming signal according to the valid input signal; wherein the second threshold voltage is greater than the first threshold voltage;

[0018] The input ends of the first comparison module and the second comparison module are both connected to the dimming voltage input end for receiving the dimming input voltage, the output ends of the first comparison module and the second comparison module are respectively connected to the corresponding input ends of the effective input signal generating module, and the output end of the effective input signal generating module is connected to the input end of the output module.

[0019] Optionally, the effective input signal generating module includes:

[0020] a voltage dividing module for dividing the output voltage of the first comparison module;

[0021] a buffer module for buffering an output voltage of the second comparison module;

[0022] a gating module for selecting the output of the voltage divider module as a valid input signal when the dimming input voltage is less than the first threshold voltage, and for selecting the output of the buffer module as a valid input signal when the dimming input voltage is greater than the second threshold voltage;

[0023] The voltage divider module and the buffer module are the front-stage circuit or the rear-stage circuit of the gating module, wherein, when the voltage divider module and the buffer module are the front-stage circuit of the gating module, the control end of the gating module is connected to the output end of the first comparison module, the input end of the voltage divider module is connected to the dimming voltage input end, the input end of the buffer module is connected to the output end of the second comparison module, the output end of the voltage divider module and the output end of the buffer module are both connected to the corresponding input end of the gating module, and the output end of the gating module is connected to the input end of the output module; when the voltage divider module and the buffer module are the rear-stage circuit of the gating module, the input end of the voltage divider module and the input end of the buffer module are both connected to the output end of the gating module, and the output end of the voltage divider module and the output end of the buffer module are both connected to the input end of the output module.

[0024] Optionally, the gating module includes an inverter, a first switch unit and a second switch unit;

[0025] The output end of the first comparison module is respectively connected to the input end of the inverter and the control end of the second switch unit, the output end of the second comparison module is connected to the input end of the second switch unit, the output end of the inverter is connected to the control end of the first switch unit, the input end of the first switch unit is connected to the dimming voltage input end, and the output end of the first switch unit and the output end of the second switch unit are the output end of the gating module; or,

[0026] The output end of the first comparison module is respectively connected to the input end of the inverter and the control end of the first switch unit, the output end of the second comparison module is connected to the input end of the buffer module, the output end of the buffer module is connected to the input end of the second switch unit, the input end of the voltage divider module is connected to the input end of the first switch unit, the output end of the inverter is connected to the control end of the second switch unit, and the output end of the first switch unit and the output end of the second switch unit are the output end of the selection module.

[0027] Optionally, the first switch unit is a MOS tube, a triode, a single-pole single-throw switch with a control end, or a transmission gate; the second switch unit is a MOS tube, a triode, a single-pole single-throw switch with a control end, or a transmission gate.

[0028] Optionally, the buffer module is a circuit separate from the voltage divider module, or reuses the same circuit as the voltage divider module; wherein the voltage divider module includes a first resistor and a second resistor connected in series, one end of the first resistor and the second resistor connected in series is the output end of the voltage divider module, and the other end of the first resistor is the input end of the voltage divider module; and / or, the buffer module includes a third resistor and a fourth resistor connected in series, one end of the third resistor and the fourth resistor connected in series is the output end of the buffer module, and the other end of the third resistor is the input end of the buffer module.

[0029] Optionally, the second comparison module includes an input resistor, a voltage stabilizing unit, a first operational amplifier, and a first switching tube; one end of the input resistor is connected to the dimming voltage input end, and the other end is connected to one end of the voltage stabilizing unit and the positive input end of the first operational amplifier; the other end of the voltage stabilizing unit is grounded; the output end of the first operational amplifier is connected to the control end of the first switching tube, one end of the conduction path of the first switching tube is connected to the working voltage, and the other end of the conduction path of the first switching tube is connected to the corresponding input end of the effective input signal generating module.

[0030] Optionally, the second comparison module also includes an offset voltage source, one end of the offset voltage source is connected to the inverting input end of the first operational amplifier, and the other end of the offset voltage source is connected to the corresponding input end of the effective input signal generating module or the other end of the conduction path of the first switch tube.

[0031] Optionally, the voltage stabilizing unit includes a voltage stabilizing diode, one end of the voltage stabilizing diode is connected to a connection node between the input resistor and the forward input end of the first operational amplifier, the other end of the voltage stabilizing diode is grounded, and a reverse breakdown voltage of the voltage stabilizing diode is the second threshold voltage; or,

[0032] The voltage stabilizing unit includes a second operational amplifier and a second switch tube, the inverting input terminal of the second operational amplifier and one end of the conduction circuit of the second switch tube are respectively connected to the connection node between the input resistor and the positive input terminal of the first operational amplifier, the positive input terminal of the second operational amplifier is connected to the second threshold voltage, the output terminal of the second operational amplifier is connected to the control terminal of the second switch tube, and the other end of the conduction circuit of the second switch tube is grounded.

[0033] Based on the same inventive concept, the present invention also provides an LED driving system, comprising a signal input circuit for generating a dimming input voltage and an LED dimming circuit as described in the present invention, wherein the output end of the signal input circuit is connected to the dimming voltage input end of the LED dimming circuit.

[0034] Based on the same inventive concept, the present invention further provides an electronic device, including an LED lamp and an LED driving system connected thereto as described in the present invention.

[0035] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0036] The technical solution of the present invention uses the first comparison module and the second comparison module to judge the size of the dimming input voltage, and uses the effective input signal generation module to generate a suitable effective input signal output according to the judgment result. When the dimming input voltage is lower than the first threshold voltage, the output module can output a relatively accurate dimming signal according to the generated effective input signal, thereby avoiding the problem that the current flowing through the LED is not accurate when the input voltage Vref_Dim is low due to the existence of the offset voltage Vos of the operational amplifier of the existing LED dimming circuit and the LED lamp brightness cannot meet the dimming accuracy index requirements. The technical solution of the present invention can improve the LED dimming accuracy and meet the needs of high-precision dimming. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a circuit schematic diagram of an existing LED dimming circuit;

[0039] Figure 2 for Figure 1 The curve showing the voltage Vp of the LED dimming circuit changes with the dimming input voltage Vref_Dim;

[0040] Figure 3 A schematic diagram of the functional modules of an LED dimming circuit according to an embodiment of the present invention;

[0041] Figure 4A for Figure 3 A specific circuit structure schematic diagram of the LED dimming circuit shown;

[0042] Figure 4B for Figure 4A The curve showing the voltage Vp of the LED dimming circuit changes with the dimming input voltage Vref_Dim;

[0043] Figure 5 for Figure 3 Another specific circuit structure schematic diagram of the LED dimming circuit shown;

[0044] Figure 6 for Figure 3 Another specific circuit structure schematic diagram of the LED dimming circuit shown;

[0045] Figure 7 A schematic diagram of functional modules of an LED dimming circuit according to another embodiment of the present invention;

[0046] Figure 8 for Figure 7 The specific circuit structure diagram of the LED dimming circuit is shown. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The meaning of "and / or" in this article is to choose one or both.

[0048] Please refer to Figure 3 An embodiment of the present invention provides an LED dimming circuit, comprising a first comparison module 11, a second comparison module 12, an effective input signal generation module 13 and an output module 14. The effective input signal generation module 13 is used to generate a corresponding effective input signal Vp according to the judgment results of the first comparison module 11 and the second comparison module 12, and specifically comprises a gating module 131, a voltage dividing module 132 and a buffer module 133.

[0049] The first comparison module 11 is used to determine whether a dimming input voltage Vref_Dim (usually in the range of 0~5V) is less than a first threshold voltage Vk (Vk is between 0~0.8V); the second comparison module 12 is used to determine whether the dimming input voltage Vref_Dim is greater than a second threshold voltage Vq (for example, 2.5V); the voltage divider module 132 is used to divide the output voltage of the first comparison module 11; the buffer module 133 is used to buffer the output voltage of the second comparison module 12; the selection module 131 is used to select the output of the voltage divider module 132 as the effective input signal Vp when the dimming input voltage Vref_Dim is less than the first threshold voltage Vk, and, when the dimming input voltage Vref_Dim is greater than the second threshold voltage Vq, select the output of the buffer module 133 as the effective input signal Vp; the output module 14 is used to output the dimming signal out according to the effective input signal Vp.

[0050] In this embodiment, the voltage divider module 132 and the buffer module 133 are both used as the post-stage circuit of the selection module 131, the input ends of the first comparison module 11 and the second comparison module 12 are both connected to the dimming voltage input end In for receiving the dimming input voltage Vref_Dim, the output ends of the first comparison module 11 and the second comparison module 12 are respectively connected to the corresponding input ends of the selection module 131, the voltage divider module 132 and the buffer module 133 can be two separate circuits, at this time, the corresponding output ends of the selection module 131 are respectively connected to the input end of the voltage divider module 132 and the input end of the buffer module 133, and the output end of the voltage divider module 132 and the output end of the buffer module 133 are both connected to the input end of the output module 14.

[0051] Please refer to Figure 4A and Figure 5 In the specific application of the LED dimming circuit of this embodiment, in order to simplify the circuit, the voltage divider module 132 and the buffer module 133 can reuse the same circuit. At this time, the output end of the selection module 131 is connected to the input end of the same circuit, and the output end of the same circuit is connected to the input end of the output module 14.

[0052] Specifically, in a specific application of this embodiment, please refer to Figure 4A, the first comparison module 11 includes a comparator Comp, the second comparison module 12 includes an input resistor R0, a voltage stabilizing diode Z (i.e., a voltage stabilizing unit), a first operational amplifier OPA1, a first switch tube M0, and an offset voltage source Vos, the selection module 131 includes a first switch K1, an inverter inv, and a second switch K2, the voltage divider module 132 and the buffer module 133 reuse the same circuit, the same circuit includes a first resistor R1 and a second resistor R2 connected in series, and the output module 14 includes an error amplifier EA. Among them, the first switch K1 and the second switch K2 are single-pole single-throw switches with control terminals, which can be closed or opened under the action of a signal received at their control terminals; the positive input terminal of the comparator Comp is connected to the dimming voltage input terminal In to access the dimming input voltage Vref_Dim, and the negative input terminal of the comparator Comp is connected to the first threshold voltage Vk, Figure 4AVk=0.8V, the output of the comparator Comp is connected to the input of the inverter inv and the control end of the second switch K2; one end of the input resistor R0 is connected to the dimming voltage input In to access the dimming input voltage Vref_Dim, and the other end of the input resistor R0 is connected to the forward input of the first operational amplifier OPA1 and the cathode of the Zener diode Z; the anode of the Zener diode Z is grounded, and the reverse breakdown voltage Vz=Vq of the Zener diode Z (Vq can be equal to 2.5V). The Zener diode Z is mainly used for voltage stabilization and voltage division with the input resistor R0 to generate the input voltage required by OPA1, thereby realizing OPA1's judgment on whether the dimming input voltage Vref_Dim is greater than Vq; the switch tube M0 is a PMOS tube, whose gate is the control end, connected to the output of the first operational amplifier OPA1, its drain is one end of the conduction path, used to access the working voltage Vdd, and its source is the other end of the conduction path, connected to the input end of the second switch K2; the positive electrode of the offset voltage source Vos is connected to the reverse input of the first operational amplifier OPA1 The negative electrode of the offset voltage source Vos is connected to the output end of the second switch K2. In other embodiments of the present invention, the negative electrode of the offset voltage source Vos can also be replaced by the source connected to M0; the output end of the inverter inv is connected to the control end of the first switch K1, the input end of the first switch K1 is connected to the dimming voltage input end In, the output end of the first switch K1 is connected to the output end of the second switch K2 and one end of the first resistor R1, and the node in which the first resistor R1 and the second resistor R2 are connected in series outputs an effective input signal Vp; the positive input end of the error amplifier EA is connected to the node in which the first resistor R1 and the second resistor R2 are connected in series to receive the effective input signal Vp, the reverse input end of the error amplifier EA is connected to a feedback end FB for feeding back the LED voltage, and is used to access the feedback voltage Vfb related to the LED light emission condition, and the output end of the error amplifier EA outputs the dimming signal out to an LED lamp, and the LED lamp is usually connected to ground through an external resistor Rfb (not shown) in series, and the current flowing through the LED can be set by adjusting the resistance value of the external resistor Rfb. That is: I_Led = Vfb / Rfb, usually Vfb = 0 ~ 0.4V, Vfb = K * Vref_Dim, Vref_Dim is usually in the range of 0 ~ 5V. The curve of Vp changing with Vref_Dim is as follows Figure 4B shown.

[0053] Please refer to Figure 4A and Figure 4B When Vref_Dim is greater than 2.5V, the first switch K1 is disconnected and the second switch K2 is closed. After the voltage is divided by the first resistor R1 and the second resistor R2, Vp=Vfb=2.5V*n2, where n2 is a proportional constant. The error of the Vfb voltage Accuracy1_Vfb is:

[0054] ;

[0055] Error Accuracy1_Vfb vs. Figure 1 The error Accuracy1_Vfb in the conventional LED dimming circuit shown is the same.

[0056] Please continue to refer to Figure 4A and Figure 4B , and when Vref_Dim is between 0 and 0.8V, the first switch K1 is closed and enabled, and the second switch K2 is opened. After the voltage is divided by the first resistor R1 and the second resistor R2, Vp=Vfb=Vref_Dim*n1; n1 is related to the ratio between the first resistor R1 and the second resistor R2. The error of the Vfb voltage is determined by the ratio between the first resistor R1 and the second resistor R2. The error of the Vfb voltage, it can be seen that when the dimming input voltage Vref_Dim is within the range of 0V to 0.8V, Accuracy2_Vfb is greatly reduced compared to Accuracy1_Vfb, that is, the error of the Vfb voltage (that is, Accuracy2_Vfb) is greatly reduced. In other words, Figure 4A The circuit design shown can make the total error (ie, Accuracy2_Vfb) less than 1% when Vref_Dim is in the range of 0V to 2.5V.

[0057] It can be seen that the LED dimming circuit of this embodiment uses the first comparison module and the second comparison module to judge the dimming input voltage, and uses the selection module to select the appropriate signal output according to the judgment result. When the dimming input voltage is lower than the first threshold voltage, it can output a relatively accurate dimming signal through the voltage divider module, avoiding the problem that the current flowing through the LED is not accurate when the dimming input voltage Vref_Dim is low due to the existence of the offset voltage Vos of the operational amplifier of the existing LED dimming circuit and the LED lamp brightness cannot meet the dimming accuracy index requirements. The technical solution of the present invention can improve the LED dimming accuracy and meet the needs of high-precision dimming.

[0058] It should be noted that the circuit structure of the gating module 131 is not limited to the above structure. Specifically, in other application embodiments of the present invention, the first switch K1 and the second switch K2 can be replaced by electronic components or circuits with equivalent functions. For example, please refer to Figure 5As shown, in another specific application embodiment of the present invention, the first switch K1 is replaced by a first transmission gate TG1 having a control end, and the second switch K2 is replaced by a second transmission gate TG2 having a control end. The first transmission gate TG1 and the second transmission gate TG2 can be closed or opened under the action of the signal received at their control ends. The input end of the first transmission gate TG1 is connected to the dimming voltage input end In, the control end of the first transmission gate TG1 is connected to the output end of the inverter inv, the output end of the first transmission gate TG1 is connected to one end of the first resistor R1 and the output end of the second transmission gate TG2, the input end of the second transmission gate TG2 is connected to the source of the switch tube M0, and the control end of the second transmission gate is connected to the output end of the comparator Comp; other circuit parts of the LED dimming circuit of this application embodiment are the same as Figure 4A The corresponding circuit parts of the LED dimming circuit in the application embodiment shown are the same, and can be referred to the above description, which will not be repeated here. For another example, in other specific application embodiments of the present invention, the single-pole single-throw switch (the first switch K1 and the second switch K2) with a control terminal can be replaced by a MOS tube or a triode.

[0059] It should be noted that the circuit structure of the second comparison module 12 is not limited to the above structure. In other embodiments of the present invention, the offset voltage source Vos can be omitted, and its voltage regulator diode Z can also be replaced by a circuit design of a voltage regulator unit with the same function. For example, please refer to Figure 5 In a specific application embodiment of the present invention, the voltage stabilizing unit of the second comparison module 12 includes a second operational amplifier OPA2 and a second switch tube M1, the second switch tube M1 is an NMOS tube, the inverting input terminal of the second operational amplifier OPA2 and the source of the second switch tube M1 (i.e., one end of the M1 conduction circuit) are respectively connected to the connection node of the input resistor R1 and the positive input terminal of the first operational amplifier OPA1, and the positive input terminal of the second operational amplifier OPA2 is connected to the second threshold voltage Vq ( Figure 5 In the example, Vq=2.5V), the output end of the second operational amplifier OPA2 is connected to the gate (i.e., the control end) of the second switch tube M1, and the drain of the second switch tube M1 (i.e., the other end of the M1 conduction circuit) is grounded; the other circuit parts of the LED dimming circuit of this application embodiment are the same as Figure 4AThe corresponding circuit parts of the LED dimming circuit in the application embodiment shown are the same, and can be referred to the above description, which will not be repeated here. When Vk=0.8V, Vq=2.5V, and Vref_Dim is in the range of 0.8V to 2.5V, the second operational amplifier OPA2 outputs a high level, so that M1 is turned on, and Vp increases with the increase of the dimming input voltage Vref_Dim. When Vref_Dim increases to 2.5, Vp=0.4V; when Vk=0.8V, Vq=2.5V, and Vref_Dim is greater than 2.5V, the second operational amplifier OPA2 outputs a low level, so that M1 is turned off, the first operational amplifier OPA1 outputs a high level, M0 is turned on, TG2 is turned on, and Vp=2.5V.

[0060] Figure 4A and Figure 5 In the embodiment shown, the buffer module 133 and the voltage divider module 132 reuse the same circuit, but in other embodiments of the present invention, the buffer module 133 and the voltage divider module 132 can be two separate circuits. Figure 6 As shown, in another specific embodiment of the LED dimming circuit of the present invention, the output end of the second switch K2 is connected to the input end of the buffer module 133, the output end of the first switch K1 is connected to the input end of the voltage divider module 132, the output ends of the buffer module 133 and the voltage divider module 132 are both connected to the positive input end of the error amplifier EA, and the voltage divider module 132 includes a first resistor R1 and a second resistor R2 connected in series; other circuit parts of the LED dimming circuit of this application embodiment are similar to Figure 4A The corresponding circuit parts of the LED dimming circuit in the application embodiment shown are the same, and reference may be made to the above description, which will not be repeated here.

[0061] In addition, in the above embodiment, the voltage divider module 132 and the buffer module 133 are used as the post-stage circuit of the gating module 131, so the first comparison module 11 and the second comparison module 12 are first connected to the gating module 131, and then the gating module 131 selects the corresponding branch and outputs the corresponding Vp, but the technical solution of the present invention is not limited to this, please refer to Figure 7 In another embodiment of the present invention, the voltage divider module 132 and the buffer module 133 can also be used as the front stage circuit of the selection module 131. At this time, the first comparison module 11 is first connected to the voltage divider module 132, the second comparison module 12 is first connected to the buffer module 133, and the selection module 131 is connected to the voltage divider module 132 and the buffer module 133 and selects the voltage divider module 132 or the buffer module 133 to output the corresponding Vp, which can also achieve the same Figure 3 The circuit shown has the same technical effect. Please refer to Figure 7The LED dimming circuit includes a first comparison module 11, a second comparison module 12, an effective input signal generation module 13 and an output module 14. The effective input signal generation module 13 includes a gating module 131, a voltage dividing module 132 and a buffer module 133. The input ends of the first comparison module 11 and the second comparison module 12 are both connected to a dimming voltage input end In for receiving the dimming input voltage Vref_Dim, the output end of the first comparison module 11 is connected to a control end of the gating module 131, the input end of the voltage dividing module 132 (i.e., one end of the first resistor R1) is connected to the dimming voltage input end In, the output end of the second comparison module 12 is connected to an input end of the buffer module 133 (i.e., one end of the third resistor R3), the output end of the voltage dividing module 132 and the output end of the buffer module 133 are both connected to the corresponding input end of the gating module 131, and the output end of the gating module 131 is connected to the input end of the output module 14.

[0062] Please refer to Figure 8In a specific embodiment of the present invention, the first comparison module 11 includes a comparator Comp, the second comparison module 12 includes an input resistor R0, a voltage stabilizing diode Z (i.e., a voltage stabilizing unit), a first operational amplifier OPA1, and a first switch tube M0, the selection module 131 includes a first transmission gate (i.e., a first switch unit) TG1, an inverter inv, and a second transmission gate (i.e., a second switch unit) TG2, the output module 14 includes an error amplifier EA, the voltage divider module 132 and the buffer module 133 are separate circuits, specifically, the voltage divider module 132 includes a first resistor R1 and a second resistor R2 connected in series, and the buffer module 133 includes a third resistor R3 and a fourth resistor R4 connected in series.Among them, the positive input terminal of the comparator Comp is connected to the dimming voltage input terminal In to access the dimming input voltage Vref_Dim, the negative input terminal of the comparator Comp is connected to the first threshold voltage Vk, Vk is between 0~0.8V, and the output terminal of the comparator Comp is connected to the input terminal of the inverter inv and the control terminal of the first transmission gate TG1; one end of the input resistor R0 is connected to the dimming voltage input terminal In to access the dimming input voltage Vref_Dim, and the other end of the input resistor R0 is connected to the positive input terminal of the first operational amplifier OPA1 and the cathode of the voltage regulator diode Z; The anode of the voltage-stabilizing diode Z is grounded, and the reverse breakdown voltage of the voltage-stabilizing diode Z is Vz=Vq (Vq can be equal to 2.5). The voltage-stabilizing diode Z is mainly used for voltage stabilization and voltage division with the input resistor R0 to generate the input voltage required by OPA1, thereby realizing OPA1's judgment on whether the dimming input voltage Vref_Dim is greater than Vq; the switch tube M0 is a PMOS tube, whose gate is the control end, connected to the output end of the first operational amplifier OPA1, whose drain is one end of the conduction path, used to access the working voltage Vdd, and whose source is the other end of the conduction path and one end of the third resistor R3 (as a buffer mode) The other end of the third resistor R3 is connected to one end of the fourth resistor R4, serving as the output end of the buffer module 133; one end of the first resistor R1 (serving as the input end of the voltage divider module 132) is connected to the dimming voltage input end In to access the dimming input voltage Vref_Dim; the other end of the first resistor R1 is connected to one end of the second resistor R2, serving as the output end of the voltage divider module 132; the other end of the second resistor R2 and the other end of the fourth resistor R4 are both grounded; the output end of the voltage divider module 132 (i.e., the series connection node of the first resistor R1 and the second resistor R2) is connected to the first resistor R2. The input end of the transmission gate TG1 and the output end of the buffer module 133 (i.e., the series node of the third resistor R3 and the fourth resistor R4) are connected to the input end of the second transmission gate TG2, and the output end of the first transmission gate TG1 and the output end of the second transmission gate TG2 are both connected to the positive input end of the error amplifier EA, so as to input the effective input signal Vp to the positive input end of the error amplifier EA; the reverse input end of the error amplifier EA is connected to a feedback end FB for feeding back the LED voltage, so as to access the feedback voltage Vfb related to the LED light emission condition, and the output end of the error amplifier EA outputs the dimming signal out.

[0063] Based on the same inventive concept, an embodiment of the present invention further provides an LED driving system, including a signal input circuit (not shown) for generating a dimming input voltage and an LED dimming circuit as described in the present invention, wherein an output end of the signal input circuit is connected to the dimming voltage input end of the LED dimming circuit, and is used to provide a dimming input voltage Vref_Dim to the dimming voltage input end of the LED dimming circuit. Another output end of the signal input circuit is a feedback end FB for feeding back the LED voltage, which is connected to the reverse input end of the error amplifier EA of the LED dimming circuit, and is used to provide a feedback voltage Vfb related to the LED light-emitting condition to the reverse input end of the error amplifier EA. The signal input circuit may include an AC source, a rectifier, and a control chip connected in sequence. The rectifier receives an AC signal from the AC source, and outputs a DC signal after rectification. The control chip generates a dimming input voltage Vref_Dim and a feedback voltage Vfb according to the DC signal.

[0064] Based on the same inventive concept, an embodiment of the present invention further provides an electronic device, including an LED lamp and an LED driving system as described in the present invention connected thereto. The electronic device may be a lighting device, a charger, a portable communication device, and the like.

[0065] The LED driving system and electronic device of the present invention have all the technical effects brought by the LED dimming circuit of the present invention because they have the LED dimming circuit of the present invention.

[0066] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED dimming circuit, characterized in that: include: A first comparison module for determining whether a dimming input voltage is less than a first threshold voltage; A second comparison module for determining whether the dimming input voltage is greater than a second threshold voltage; An effective input signal generating module for generating a corresponding effective input signal according to the judgment results of the first comparing module and the second comparing module; An output module for outputting a dimming signal according to the valid input signal; wherein the second threshold voltage is greater than the first threshold voltage; The input ends of the first comparison module and the second comparison module are both connected to the dimming voltage input end for receiving the dimming input voltage, the output ends of the first comparison module and the second comparison module are respectively connected to the corresponding input ends of the effective input signal generating module, the output end of the effective input signal generating module is connected to the input end of the output module, and the other input end of the output module is also connected to the feedback voltage related to the LED light emission condition.

2. The LED dimming circuit according to claim 1, characterized in that: The effective input signal generating module comprises: a voltage dividing module for dividing the output voltage of the first comparison module; a buffer module for buffering an output voltage of the second comparison module; a gating module for selecting the output of the voltage divider module as a valid input signal when the dimming input voltage is less than the first threshold voltage, and for selecting the output of the buffer module as a valid input signal when the dimming input voltage is greater than the second threshold voltage; The voltage divider module and the buffer module are the front-stage circuit or the rear-stage circuit of the gating module, wherein, when the voltage divider module and the buffer module are the front-stage circuit of the gating module, the control end of the gating module is connected to the output end of the first comparison module, the input end of the voltage divider module is connected to the dimming voltage input end, the input end of the buffer module is connected to the output end of the second comparison module, the output end of the voltage divider module and the output end of the buffer module are both connected to the corresponding input end of the gating module, and the output end of the gating module is connected to the input end of the output module; when the voltage divider module and the buffer module are the rear-stage circuit of the gating module, the input end of the voltage divider module and the input end of the buffer module are both connected to the output end of the gating module, and the output end of the voltage divider module and the output end of the buffer module are both connected to the input end of the output module.

3. The LED dimming circuit according to claim 2, characterized in that: The gating module includes an inverter, a first switch unit and a second switch unit; The output end of the first comparison module is respectively connected to the input end of the inverter and the control end of the second switch unit, the output end of the second comparison module is connected to the input end of the second switch unit, the output end of the inverter is connected to the control end of the first switch unit, the input end of the first switch unit is connected to the dimming voltage input end, and the output end of the first switch unit and the output end of the second switch unit are the output end of the gating module; or, The output end of the first comparison module is respectively connected to the input end of the inverter and the control end of the first switch unit, the output end of the second comparison module is connected to the input end of the buffer module, the output end of the buffer module is connected to the input end of the second switch unit, the input end of the voltage divider module is connected to the input end of the first switch unit, the output end of the inverter is connected to the control end of the second switch unit, and the output end of the first switch unit and the output end of the second switch unit are the output end of the selection module.

4. The LED dimming circuit according to claim 3, characterized in that: The first switch unit is a MOS tube, a triode, a single-pole single-throw switch with a control end, or a transmission gate; the second switch unit is a MOS tube, a triode, a single-pole single-throw switch with a control end, or a transmission gate.

5. The LED dimming circuit according to claim 2, characterized in that: The buffer module is a circuit separate from the voltage divider module, or reuses the same circuit as the voltage divider module; wherein the voltage divider module includes a first resistor and a second resistor connected in series, one end of the first resistor and the second resistor connected in series is the output end of the voltage divider module, and the other end of the first resistor is the input end of the voltage divider module; and / or, the buffer module includes a third resistor and a fourth resistor connected in series, one end of the third resistor and the fourth resistor connected in series is the output end of the buffer module, and the other end of the third resistor is the input end of the buffer module.

6. The LED dimming circuit according to any one of claims 1 to 5, characterized in that: The second comparison module includes an input resistor, a voltage stabilizing unit, a first operational amplifier, and a first switching tube; one end of the input resistor is connected to the dimming voltage input end, and the other end is connected to one end of the voltage stabilizing unit and the positive input end of the first operational amplifier; the other end of the voltage stabilizing unit is grounded; the output end of the first operational amplifier is connected to the control end of the first switching tube, one end of the conduction path of the first switching tube is connected to the working voltage, and the other end of the conduction path of the first switching tube is connected to the corresponding input end of the effective input signal generating module.

7. The LED dimming circuit according to claim 6, characterized in that: The second comparison module also includes an offset voltage source, one end of which is connected to the inverting input end of the first operational amplifier, and the other end of which is connected to the corresponding input end of the effective input signal generating module or the other end of the conduction path of the first switch tube.

8. The LED dimming circuit according to claim 6, characterized in that: The voltage stabilizing unit includes a voltage stabilizing diode, one end of the voltage stabilizing diode is connected to a connection node between the input resistor and the forward input end of the first operational amplifier, the other end of the voltage stabilizing diode is grounded, and the reverse breakdown voltage of the voltage stabilizing diode is the second threshold voltage; or, The voltage stabilizing unit includes a second operational amplifier and a second switch tube, the inverting input terminal of the second operational amplifier and one end of the conduction circuit of the second switch tube are respectively connected to the connection node between the input resistor and the positive input terminal of the first operational amplifier, the positive input terminal of the second operational amplifier is connected to the second threshold voltage, the output terminal of the second operational amplifier is connected to the control terminal of the second switch tube, and the other end of the conduction circuit of the second switch tube is grounded.

9. An LED driving system, characterized in that: It comprises a signal input circuit for generating a dimming input voltage and an LED dimming circuit as claimed in any one of claims 1 to 8, wherein the output end of the signal input circuit is connected to the dimming voltage input end of the LED dimming circuit.

10. An electronic device, characterized in that: An LED driving system as claimed in claim 9 comprising an LED lamp and a connected LED lamp.

Images