CN112654111A - LED dimming circuit, LED driving system and electronic equipment - Google Patents

Abstract

The invention discloses an LED dimming circuit, an LED driving system and an electronic device. A first comparison module and a second comparison module are used to judge the magnitude of a dimming input voltage, and a gating module is used to select the appropriate voltage 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 the voltage divider module, avoiding the existing LED dimming circuit because the offset voltage Vos of the operational amplifier always exists and is large Uncertainty leads to the problem that the current flowing through the LED is inaccurate when the input voltage Vref_Dim is low, and the brightness of the LED lamp cannot meet the requirements of the dimming accuracy. The technical scheme of the present invention can improve the LED dimming precision and meet the requirements of high-precision dimming.

Description

LED dimming circuit, LED driving system and electronic equipment

technical field

The invention relates to the technical field of LED driving, in particular to an LED dimming circuit, an LED driving system and an electronic device.

Background technique

LED lighting technology has gradually become popular due to its low power consumption, long life and high luminous efficiency, and has become the mainstream lighting technology. Basic application conditions.

Please refer to FIG. 1, an existing LED dimming circuit includes: an input resistor R0, a Zener diode Z, an operational amplifier OPA, an offset voltage source Vos, a switch Mo (P type), a resistor R1, a resistor R2 and an error amplifier EA, wherein the dimming input voltage Vref_Dim is input to the LED dimming circuit from one end of the resistor R0, the other end of the resistor R0 is grounded through the cathode and anode of the Zener diode Z in turn, and the other end of the resistor R0 is also connected to the operational amplifier OPA. The forward input terminal, the output terminal 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, and one end of the offset voltage source Vos is connected to the operational amplifier OPA. To the input end, 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 forward input end of the error amplifier EA and input the voltage Vp to the error amplifier EA, and the voltage Vp varies with the dimming input voltage The curve of Vref_Dim change is shown in Figure 2; the inverting input terminal of the error amplifier EA is connected to a feedback terminal FB, the feedback voltage Vfb connected to the feedback terminal FB is related to the dimming input voltage Vref_Dim, and the output terminal Out of the error amplifier EA is directed to The corresponding LED transmits a dimming signal, and the LED is usually grounded by connecting 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.

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

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:

It can be known from the relational expressions Accuracy1_Vfb and Accuracy2_Vfb that Accuracy2_Vfb determines the final error amount.

If Vk=0.8V, assuming Vos=8mV, the final error:

If Vk=0.1V, assuming Vos=8mV, the final error:

When the LED dimming circuit structure shown in Figure 1 is used to realize LED dimming, since the offset voltage Vos of the operational amplifier OPA always exists and its size is variable, when the input voltage Vref_Dim is low, the current flowing through the LED will be inconsistent. Accurate, the brightness of the LED light cannot meet the index requirements of dimming accuracy, resulting in the inability to meet the needs of high-precision LED dimming.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an LED dimming circuit, an LED driving system and electronic equipment using the same, which can avoid the existing LED dimming circuit due to the fact that the offset voltage Vos of the operational amplifier always exists and its size is not constant, which may cause when the input voltage Vref_Dim When the current is low, the current flowing through the LED is inaccurate, and the brightness of the LED light cannot meet the requirements of the dimming accuracy.

In order to achieve the above purpose, the present invention provides an LED dimming circuit, comprising:

a first comparison module for judging whether the dimming input voltage is less than the first threshold voltage;

a second comparison module for judging whether the dimming input voltage is greater than a second threshold voltage;

a valid input signal generating module for generating a corresponding valid input signal according to the judgment results of the first comparison module and the second comparison 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 terminals of the first comparison module and the second comparison module are both connected to the dimming voltage input terminal for receiving the dimming input voltage, and the outputs of the first comparison module and the second comparison module are The terminals are respectively connected to the corresponding input terminals of the valid input signal generating module, and the output terminal of the valid input signal generating module is connected to the input terminal of the output module.

Optionally, the effective input signal generating module includes:

a voltage dividing module for dividing the output voltage of the first comparison module;

a buffer module for buffering the output voltage of the second comparison module;

for selecting the output of the voltage divider module as an effective input signal when the dimming input voltage is less than the first threshold voltage, and selecting the buffer module when the dimming input voltage is greater than the second threshold voltage The output is used as the gating module of the valid input signal;

The voltage dividing module and the buffer module are the pre-stage circuit or the post-stage circuit of the gating module, wherein, when the voltage dividing module and the buffer module are the pre-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 dividing module is connected to the dimming voltage input end, and the input end of the buffer module is connected to the second comparison module The output end of the voltage dividing 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 dividing module and the buffer module are the post-stage circuits of the gating module, the input end of the voltage dividing module and the input end of the buffer module are both connected to the output end of the gating module, Both the output end of the voltage dividing module and the output end of the buffer module are connected to the input end of the output module.

Optionally, 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, and 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, the output end of the first switch unit and the The output end of the two switch units is 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, and the 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, and the output end of the inverter is connected to the second switch unit The control terminal of the first switch unit and the output terminal of the second switch unit are the output terminals of the gating module.

Optionally, the first switch unit is a MOS tube, a triode, a SPST switch with a control terminal, or a transmission gate; the second switch unit is a MOS tube, a triode, a SPST switch with a control terminal, or a transmission gate, respectively.

Optionally, the buffer module is a separate circuit from the voltage divider module, or multiplexes the same circuit with the voltage divider resistor; wherein the voltage divider module includes a first resistor and a second resistor connected in series A resistor, one end of the first resistor and the second resistor 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 The buffer module includes a third resistor and a fourth resistor connected in series, one end of the third resistor and the fourth resistor in series is the output end of the buffer module, and the other end of the third resistor is the output end of the buffer module. input.

Optionally, the second comparison module includes an input resistor, a voltage stabilization unit, a first operational amplifier, and a first switch tube; one end of the input resistor is connected to the input end of the dimming voltage, and the other end is connected to the voltage stabilization unit one end of the first operational amplifier and the forward input end of the first operational amplifier; the other end of the voltage regulator unit is grounded; the output end of the first operational amplifier is connected to the control end of the first switch tube, the first switch One end of the conduction path of the tube is connected to the working voltage, and the other end of the conduction path of the first switch tube is connected to the corresponding input terminal of the effective input signal generating module.

Optionally, the second comparison module further 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 valid input signal The corresponding input end of the generation module or the other end of the conduction path of the first switch tube.

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, and the other end of the voltage-stabilizing diode is connected. grounded, the reverse breakdown voltage of the Zener diode is the second threshold voltage; or,

The voltage-stabilizing unit includes a second operational amplifier and a second switch tube, and an inverting input end of the second operational amplifier and a conduction circuit end of the second switch tube are respectively connected to the input resistor and the first switch tube. A connection node of the forward input end of an operational amplifier, the forward input end of the second operational amplifier is connected to the second threshold voltage, and the output end of the second operational amplifier is connected to the control end of the second switch tube , and the other end of the conduction circuit of the second switch tube is grounded.

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 the LED dimming circuit according to the present invention, wherein the output end of the signal input circuit is connected to the The dimming voltage input terminal of the LED dimming circuit is connected.

Based on the same inventive concept, the present invention also provides an electronic device, including an LED lamp and the connected LED driving system according to the present invention.

Compared with the prior art, the technical scheme of the present invention has the following beneficial effects:

In the technical scheme of the present invention, the first comparison module and the second comparison module are used to determine the magnitude of the dimming input voltage, and the valid input signal generating module is used to generate an appropriate valid input signal output according to the judgment result. When the dimming input voltage is When the voltage is lower than the first threshold voltage, the output module can output a relatively accurate dimming signal according to the generated valid input signal, avoiding the existing LED dimming circuit due to the fact that the offset voltage Vos of the operational amplifier always exists and its size is not fixed. When the input voltage Vref_Dim is low, the current flowing through the LED is inaccurate, and the brightness of the LED lamp cannot meet the requirements of the dimming accuracy. The technical scheme of the present invention can improve the LED dimming precision and meet the requirements of high-precision dimming.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a circuit schematic diagram of an existing LED dimming circuit;

FIG. 2 is a curve showing the variation of the voltage Vp of the LED dimming circuit shown in FIG. 1 with the dimming input voltage Vref_Dim;

3 is a schematic diagram of functional modules of an LED dimming circuit according to an embodiment of the present invention;

4A is a schematic diagram of a specific circuit structure of the LED dimming circuit shown in FIG. 3;

FIG. 4B is a curve showing the variation of the voltage Vp of the LED dimming circuit shown in FIG. 4A with the dimming input voltage Vref_Dim;

FIG. 5 is a schematic diagram of another specific circuit structure of the LED dimming circuit shown in FIG. 3;

FIG. 6 is a schematic diagram of another specific circuit structure of the LED dimming circuit shown in FIG. 3;

7 is a schematic diagram of functional modules of an LED dimming circuit according to another embodiment of the present invention;

FIG. 8 is a schematic diagram of a specific circuit structure of the LED dimming circuit shown in FIG. 7 .

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The meaning of "and/or" in this document is to choose one or both.

Referring to FIG. 3 , an embodiment of the present invention provides an LED dimming circuit, including a first comparison module 11 , a second comparison module 12 , a valid input signal generating module 13 and an output module 14 . Wherein, the valid input signal generation module 13 is configured to generate the corresponding valid input signal Vp according to the judgment results of the first comparison module 11 and the second comparison module 12, which specifically includes a gating module 131, a voltage dividing module 132 and a Buffer module 133 .

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 the first threshold voltage Vk (Vk is between 0-0.8V); the second comparison module 12 is used to determine whether the Whether the dimming input voltage Vref_Dim is greater than the second threshold voltage Vq (eg 2.5V); the voltage dividing module 132 is used to divide the output voltage of the first comparison module 11; the buffer module 133 is used to divide the voltage of the first comparison module 11. The output voltage of the two comparison modules 12 is buffered; the gating module 131 is used to select the output of the voltage dividing module 132 as the valid 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, the output of the buffer module 133 is selected as the valid input signal Vp; the output module 14 is configured to output the dimming signal out according to the valid input signal Vp.

In this embodiment, the voltage dividing module 132 and the buffer module 133 are both used as the post-stage circuit of the gating module 131, and the input terminals of the first comparison module 11 and the second comparison module 12 are both connected to The dimming voltage input terminal In for receiving the dimming input voltage Vref_Dim, the output terminals of the first comparison module 11 and the second comparison module 12 are respectively connected to the corresponding input terminals of the gating module 131 , the voltage dividing module 132 and the buffering module 133 may be two separate circuits. In this case, the corresponding output terminals of the gating module 131 are respectively connected to the input terminals of the voltage dividing The input end of the buffer module 133 , the output end of the voltage dividing module 132 and the output end of the buffer module 133 are all connected to the input end of the output module 14 .

Please refer to FIG. 4A and FIG. 5 , in the specific application of the LED dimming circuit of this embodiment, in order to simplify the circuit, the voltage dividing module 132 and the buffer module 133 can be multiplexed with the same circuit. The output end of the gating module 131 is connected to the input end of the same segment of the circuit, and the output end of the same segment of the circuit is connected to the input end of the output module 14 .

Specifically, in a specific application of this embodiment, please refer to FIG. 4A , the first comparison module 11 includes a comparator Comp, and the second comparison module 12 includes an input resistor R0 , a Zener diode Z (ie a voltage regulator unit), a first operational amplifier OPA1, a first switch tube M0 and an offset voltage source Vos, the gating module 131 includes a first switch K1, an inverter inv and a second switch K2, a voltage divider module 132 and a buffer module 133 The same section of circuit is multiplexed, and the same section of 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 a control terminal, which can be turned on or open under the action of the signal received by the control terminal; the positive input terminal of the comparator Comp is connected to the regulator. The light voltage input terminal In is connected to the dimming input voltage Vref_Dim, the inverting input terminal of the comparator Comp is connected to the first threshold voltage Vk, Vk=0.8V in FIG. 4A, and the output terminal of the comparator Comp is connected to the inverter inv The input terminal and the control terminal of the second switch K2; 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 forward direction of the first operational amplifier OPA1 The input terminal and the cathode of the Zener diode Z; the anode of the Zener diode Z is grounded, the reverse breakdown voltage of the Zener diode Z is Vz=Vq (Vq can be equal to 2.5V), the Zener diode Z is mainly used for voltage regulation and Divide the voltage with the input resistor R0 to generate the input voltage required by the OPA1, thereby realizing the judgment of whether the dimming input voltage Vref_Dim is greater than Vq by the OPA1; the switch tube M0 is a PMOS tube, and its gate is the control terminal, which is connected to the first operational amplifier OPA1 Its drain is one end of the conduction path, which is used to connect to the working voltage Vdd, and its source is the other end of the conduction path, which is connected to the input end of the second switch K2; the positive pole of the offset voltage source Vos is connected to the The reverse input terminal of the first operational amplifier OPA1, and the negative terminal of the offset voltage source Vos is connected to the output terminal of the second switch K2. In other embodiments of the present invention, the negative terminal of the offset voltage source Vos can also be replaced with a terminal connected to M0. source; 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, and the output end of the first switch K1 is connected to the output of the second switch K2 terminal and one end of the first resistor R1, the node where the first resistor R1 and the second resistor R2 are connected in series outputs the valid input signal Vp; the positive input end of the error amplifier EA is connected to the node where the first resistor R1 and the second resistor R2 are connected in series, In order to receive the valid input signal Vp, the inverting input terminal of the error amplifier EA is connected to a feedback terminal FB for feedback LED voltage, which is used to access the feedback voltage Vfb related to the LED lighting condition, and the output terminal of the error amplifier EA outputs dimming The signal is out to an LED lamp, and the LED lamp is usually connected to 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. The curve where Vp varies with Vref_Dim is shown in FIG. 4B .

Please refer to FIG. 4A and FIG. 4B , when Vref_Dim is greater than 2.5V, the first switch K1 is turned off, the second switch K2 is turned on, and after voltage division by the first resistor R1 and the second resistor R2, Vp=Vfb=2.5V *n2, n2 is a proportional constant, the error of Vfb voltage Accuracy1_Vfb:

The error Accuracy1_Vfb is the same as the error Accuracy1_Vfb in the conventional LED dimming circuit shown in FIG. 1 .

Please continue to refer to FIG. 4A and FIG. 4B , when Vref_Dim is between 0 and 0.8V, the first switch K1 is turned on and the second switch K2 is turned on. After voltage division 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 Accuracy2_Vfb≤0.1% , it can be seen that when the dimming input voltage Vref_Dim is in the range of 0V~0.8V, the Accuracy2_Vfb is greatly reduced compared to the Accuracy1_Vfb, that is, the error of the Vfb voltage (that is, the Accuracy2_Vfb) is greatly reduced. That is to say, the circuit design shown in FIG. 4A can make the total error (ie Accuracy2_Vfb) less than 1% when Vref_Dim is in the range of 0V to 2.5V.

It can be seen that the LED dimming circuit of this embodiment uses the first comparison module and the second comparison module to determine the size of the dimming input voltage, and the gating module selects the appropriate signal output 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 the voltage divider module, so as to avoid the existing LED dimming circuit due to the fact that the offset voltage Vos of the operational amplifier is always present and its size is variable. When the optical input voltage Vref_Dim is low, the current flowing through the LED is inaccurate, and the brightness of the LED lamp cannot meet the index requirements of the dimming accuracy. The technical scheme of the present invention can improve the LED dimming precision and meet the requirements of high-precision dimming.

It should be noted that, the circuit structure of the above-mentioned gating module 131 is not limited to the above-mentioned structure. Specifically, in other application embodiments of the present invention, the first switch K1 and the second switch K2 may be respectively replaced by electronic components or circuits with equivalent functions. For example, please refer to FIG. 5 , in another specific application embodiment of the present invention, the first switch K1 is replaced by a first transmission gate TG1 with a control terminal, and the second switch K2 is replaced by a second transmission gate with a control terminal TG2, the first transmission gate TG1 and the second transmission gate TG2 can close the conduction or open the circuit under the action of the signal received by its control terminal. The input terminal of the first transmission gate TG1 is connected to the dimming voltage input terminal In, and the first transmission gate TG1 The control end of the 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, and the input end of the second transmission gate TG2 is connected to the switch tube The source of M0 and the control end of the second transmission gate are connected to the output end of the comparator Comp; other circuit parts of the LED dimming circuit of this application embodiment correspond to those of the LED dimming circuit in the application embodiment shown in FIG. 4 The circuit parts are the same, which can be referred to above, and will not be repeated here. For another example, in other specific application embodiments of the present invention, the single-pole single-throw switches (the first switch K1 and the second switch K2 ) with control terminals can be replaced by MOS transistors or triodes, respectively.

It should be noted that, the circuit structure of the above-mentioned second comparison module 12 is not limited to the above-mentioned structure. In other embodiments of the present invention, the offset voltage source Vos can be omitted, and the Zener diode Z thereof can also be replaced by a circuit design of a voltage regulator unit with the same function. For example, please refer to FIG. 5, in a specific application embodiment of the present invention, the voltage regulator unit of the second comparison module 12 includes a second operational amplifier OPA2 and a second switch M1, and the second switch M1 is an NMOS transistor , the inverting input terminal of the second operational amplifier OPA2 and the source of the second switch tube M1 (that is, one terminal of the M1 conducting circuit) are respectively connected to the input resistor R1 and the positive terminal of the first operational amplifier OPA1 To the connection node of the input terminal, the forward input terminal of the second operational amplifier OPA2 is connected to the second threshold voltage Vq (Vq=2.5V in FIG. 5 ), and the output terminal of the second operational amplifier OPA2 is connected to the The gate (ie, the control terminal) of the second switch tube M1, and the drain of the second switch tube M1 (ie, the other end of the M1 conduction circuit) is grounded; The corresponding circuit parts of the LED dimming circuit in the application embodiment shown in 4 are the same, and reference may be made 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~2.5V, the second operational amplifier OPA2 outputs a high level, which makes M1 turn on, and Vp increases with the increase of the dimming input voltage Vref_Dim , when Vref_Dim rises 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 Output high level, M0 is turned on, TG2 is turned on, Vp=2.5V.

In the embodiments shown in FIG. 4A and FIG. 5 , the buffer module 133 and the voltage divider module 132 multiplex the same section of circuit, but in other embodiments of the present invention, the buffer module 133 and the voltage divider module 132 may be separated into two sections circuit. Specifically, please refer to FIG. 6 , in the LED dimming circuit of another specific embodiment of the present invention, the output end of the second switch K2 is connected to the input end of the buffer module 133 , and the output end of the first switch K1 is connected to the input end of the buffer module 133 . The output terminal is connected to the input terminal of the voltage divider module 132, the output terminals of the buffer module 133 and the voltage divider module 132 are both connected to the positive input terminal of the error amplifier EA, and the voltage divider module 132 includes a series connected first resistor R1 and a second resistor R1. Two resistors R2; other circuit parts of the LED dimming circuit of this application embodiment are the same as the corresponding circuit parts of the LED dimming circuit in the application embodiment shown in FIG. .

In addition, in the above embodiment, the voltage dividing module 132 and the buffer module 133 are used as the post-stage circuits of the gating module 131 , so the first comparison module 11 and the second comparison module 12 are connected to the gating module 131 first, and then pass through the gating module 131 Gating the corresponding branch to output the corresponding Vp, but the technical solution of the present invention is not limited to this, please refer to FIG. 7 , in another embodiment of the present invention, the voltage dividing module 132 and the buffer module 133 may also be As the pre-stage circuit of the gating module 131, at this time, the first comparison module 11 is first connected to the voltage dividing module 132, the second comparison module 12 is first connected to the buffer module 133, and the gating module 131 is connected to the voltage dividing module 132 and the buffer module 133 and Gating the voltage dividing module 132 or the buffering module 133 to output the corresponding Vp can also achieve the same technical effect as the circuit shown in FIG. 3 . Please refer to FIG. 7 , the LED dimming circuit includes a first comparison module 11 , a second comparison module 12 , a valid input signal generating module 13 and an output module 14 , and the valid input signal generating module 13 includes a gating module 131 , a voltage dividing module 132 and buffer module 133. The input terminals of the first comparison module 11 and the second comparison module 12 are both connected to the dimming voltage input terminal In for receiving the dimming input voltage Vref_Dim, and the output terminal of the first comparison module 11 is connected to The control end of the gating module 131 , the input end of the voltage dividing module 132 (ie, one end of the first resistor R1 ) is connected to the dimming voltage input end In, and the output end of the second comparison module 12 is connected to the input end of the buffer module 133 (ie 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 ends of the gating module 131, and the output of the gating module 131 The terminal is connected to the input terminal of the output module 14 .

Referring to FIG. 8, in 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 Zener diode Z (ie, a voltage regulator unit), The first operational amplifier OPA1 and the first switch tube M0, the gating module 131 includes a first transmission gate (ie a first switch unit) TG1, an inverter inv and a second transmission gate (ie a second switch unit) TG2, The output module 14 includes an error amplifier EA, and the voltage dividing module 132 and the buffer module 133 are separate circuits. Specifically, the voltage dividing module 132 includes a first resistor R1 and a second resistor R2 connected in series. The buffer module 133 includes a third resistor R3 and a fourth resistor R4 connected in series. The forward input terminal of the comparator Comp is connected to the dimming voltage input terminal In to connect to the dimming input voltage Vref_Dim, and the reverse input terminal of the comparator Comp is connected to the first threshold voltage Vk, where Vk is between 0 and 0.8 V, the output end of the comparator Comp is connected to the input end of the inverter inv and the control end of the first transmission gate TG1; one end of the input resistor R0 is connected to the dimming voltage input end In to access the dimming input voltage Vref_Dim, The other end of the input resistor R0 is connected to the forward input end 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 of the Zener diode Z is Vz=Vq (Vq can be equal to 2.5), the Zener diode Z is mainly used for voltage regulation and voltage division with the input resistor R0 to generate the input voltage required by OPA1, thereby realizing the judgment of OPA1 on whether the dimming input voltage Vref_Dim is greater than Vq; the switch tube M0 is PMOS tube, whose gate is the control terminal, is connected to the output terminal of the first operational amplifier OPA1, its drain is one end of the conduction path, used to access the working voltage Vdd, its source is the other end of the conduction path, and one end of the third resistor R3 (as the input end of the buffer module 133); the other end of the third resistor R3 is connected to one end of the fourth resistor R4, as the output end of the buffer module 133, and one end of the first resistor R1 (as the input end of the voltage divider module 132) ) is connected to the dimming voltage input terminal In to access the dimming input voltage Vref_Dim, and the other end of the first resistor R1 is connected to one end of the second resistor R2 as the output end of the voltage divider module 132; The other end and the other end of the fourth resistor R4 are both grounded; the output end of the voltage divider module 132 (ie the series node of the first resistor R1 and the second resistor R2) is connected to the input end of the first transmission gate TG1, and the output end of the buffer module 133 The terminal (that is, the series node of the third resistor R3 and the fourth resistor R4) is connected to the input terminal of the second transmission gate TG2, and the output terminal of the first transmission gate TG1 and the output terminal of the second transmission gate TG2 are both connected to the error amplifier EA. The forward input terminal is used to input a valid input signal Vp to the forward input terminal of the error amplifier EA; the reverse input terminal of the error amplifier EA is connected to a feedback terminal FB for feedback of the LED voltage, which is used to connect with the LED lighting conditions. The feedback voltage Vfb, the output end of the error amplifier EA outputs the dimming signal out.

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 the LED dimming circuit according to the present invention, the signal An output end of the input circuit is connected to the dimming voltage input end of the LED dimming circuit, and is used for providing the dimming input voltage Vref_Dim to the dimming voltage input end of the LED dimming circuit. The other output end of the signal input circuit is a feedback end FB for feeding back the LED voltage, which is connected to the inverting input end of the error amplifier EA of the LED dimming circuit, and is used for the inverting input end of the error amplifier EA. Provides a feedback voltage Vfb related to LED lighting conditions. The signal input circuit may include an alternating current source, a rectifier and a control chip connected in sequence. The rectifier receives the AC signal from the AC source, and outputs the DC signal after rectification. The control chip generates the dimming input voltage Vref_Dim and the feedback voltage Vfb according to the DC signal.

Based on the same inventive concept, an embodiment of the present invention further provides an electronic device, including an LED lamp and the connected LED driving system according to the present invention. The electronic device may be a lighting device, a charger, a portable communication device, or the like.

Since the LED driving system and electronic device of the present invention have the LED dimming circuit of the present invention, they have all the technical effects brought by the LED dimming circuit of the present invention.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An LED dimming circuit, comprising:

the first comparison module is used for judging whether the dimming input voltage is smaller than a first threshold voltage or not;

the second comparison module is used for judging whether the dimming input voltage is larger than a second threshold voltage or not;

the effective input signal generating module is used for generating corresponding effective input signals according to the judgment results of the first comparing module and the second comparing module;

the output module is used for outputting a dimming signal according to the effective 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 connected to a 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 generation module, and the output end of the effective input signal generation module is connected to the input end of the output module.

2. The LED dimming circuit of claim 1, wherein the valid input signal generation module comprises:

the voltage division module is used for dividing the output voltage of the first comparison module;

the buffer module is used for buffering the output voltage of the second comparison module;

a gating module for selecting the output of the voltage dividing module as an active input signal when the dimming input voltage is less than the first threshold voltage and selecting the output of the buffering module as an active input signal when the dimming input voltage is greater than the second threshold voltage;

the voltage dividing module and the buffer module are a preceding stage circuit or a subsequent stage circuit of the gating module, wherein when the voltage dividing module and the buffer module are the preceding stage circuit of the gating module, a control end of the gating module is connected with an output end of the first comparison module, an input end of the voltage dividing module is connected with an input end of the dimming voltage, an input end of the buffer module is connected with an output end of the second comparison module, output ends of the voltage dividing module and the buffer module are both connected with corresponding input ends of the gating module, and an output end of the gating module is connected with an input end of the output module; when the voltage division module and the buffer module are the rear-stage circuit of the gating module, the input end of the voltage division module and the input end of the buffer module are both connected with the output end of the gating module, and the output end of the voltage division module and the output end of the buffer module are both connected with the input end of the output module.

3. The LED dimming circuit of claim 2, wherein the gating module comprises an inverter, a first switching unit, and a second switching unit;

the output end of the first comparison module is respectively connected with the input end of the phase inverter and the control end of the second switch unit, the output end of the second comparison module is connected with the input end of the second switch unit, the output end of the phase inverter is connected with the control end of the first switch unit, the input end of the first switch unit is connected with the dimming voltage input end, and the output ends of the first switch unit and the second switch unit are the output ends of the gating module; or,

the output of first comparison module connects respectively the input of phase inverter with the control end of first switch element, the output of second comparison module connects the input of buffering module, the output of buffering module connects the input of second switch element, the input of partial pressure module is connected the input of first switch element, the output of phase inverter connects the control end of second switch element, the output of first switch element with the output of second switch element does the output of gating module.

4. The LED dimming circuit of claim 3, wherein the first switching unit is a MOS transistor, a triode, a single-pole single-throw switch with a control terminal, or a transmission gate; the second switch unit is respectively an MOS tube, a triode, a single-pole single-throw switch with a control end or a transmission.

5. The LED dimming circuit of claim 2, wherein the buffer module is a circuit separate from the voltage divider module or a circuit multiplexed with the voltage divider resistor; the voltage division module comprises a first resistor and a second resistor which are connected in series, one end of the first resistor, which is connected in series with the second resistor, is an output end of the voltage division module, and the other end of the first resistor is an input end of the voltage division module; and/or, the buffer module comprises a third resistor and a fourth resistor which are connected in series, wherein one end of the third resistor, which is connected in series with the fourth resistor, 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, wherein the second comparing module comprises an input resistor, a voltage stabilizing unit, a first operational amplifier, a first switching tube; one end of the input resistor is connected with the dimming voltage input end, and the other end of the input resistor is connected with 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 with the control end of the first switch tube, one end of a conduction path of the first switch tube is connected with working voltage, and the other end of the conduction path of the first switch tube is connected with the corresponding input end of the effective input signal generation module.

7. The LED dimming circuit of claim 6, wherein the second comparison module further comprises an offset voltage source, one end of the offset voltage source is connected to the inverting input terminal of the first operational amplifier, and the other end of the offset voltage source is connected to the corresponding input terminal of the active input signal generation module or the other end of the conduction path of the first switch tube.

8. The LED dimming circuit of claim 6, wherein the voltage regulator unit comprises a zener diode, one end of the zener diode is connected to a connection node of the input resistor and the forward input end of the first operational amplifier, the other end of the zener diode is grounded, and a reverse breakdown voltage of the zener diode is the second threshold voltage; or,

the voltage stabilizing unit comprises a second operational amplifier and a second switching tube, wherein the reverse input end of the second operational amplifier and one end of a conducting circuit of the second switching tube are respectively connected to the connecting node of the input resistor and the forward input end of the first operational amplifier, the forward input end of the second operational amplifier is connected to the second threshold voltage, the output end of the second operational amplifier is connected with the control end of the second switching tube, and the other end of the conducting circuit of the second switching tube is grounded.

9. An LED driving system comprising 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, an output of the signal input circuit being connected to a dimming voltage input of the LED dimming circuit.

10. An electronic device comprising the LED lamp and the LED driving system according to claim 9 connected thereto.

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