Constant current driving circuit of LED assembly and camera shooting lamp

Abstract

The utility model discloses a constant current driving circuit of an LED assembly and a camera shooting lamp, and relates to the technical field of LED illumination. The dimming circuit mainly solves the technical problem that the dimming circuit is low in reliability due to the fact that the dimming circuit bears large voltage in the existing LED dimming process. The circuit adjusts the current of the to-be-driven LED component through the constant current control circuit according to the analog dimming control signal; the voltage of the constant-current control circuit is acquired through the overvoltage acquisition circuit, and the constant-current control circuit and the feedback control circuit are connected under the condition that the voltage of the constant-current control circuit reaches the break-over voltage of the overvoltage acquisition circuit. And the feedback voltage is input to the feedback end of the direct current voltage stabilizing circuit through the feedback control circuit and the feedback protection circuit, so that the direct current voltage stabilizing circuit adjusts the output direct current voltage according to the feedback voltage input by the feedback control circuit. When the voltage of the constant-current control circuit is too large, the reliability of the constant-current control circuit is improved, and the service life of the constant-current control circuit is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to LED lighting technical field especially is a kind of constant-current drive circuit and camera lamp of LED assembly. BACKGROUND

[0002] LED dimming technology, mainly by changing the current of LED lamp to realize the adjustment of LED luminous brightness. The existing dimming technology mainly includes digital signal dimming and analog signal dimming, in some special scenes, such as color adjustment camera scene, analog signal dimming has more significant advantages.

[0003] However, the existing analog signal dimming method, power supply mainly adopts constant voltage power supply to output a constant DC voltage, in the process of adjusting LED current, the voltage drop of LED will change with the change of dimming current, which leads to the excessive voltage drop on dimming circuit, causing the serious heating of internal components, affecting the reliability of dimming circuit. INVENTION CONTENTS

[0004] Therefore, the utility model provides a kind of constant-current drive circuit of LED assembly, main purpose is to solve the technical problems, such as the reliability of dimming circuit is lower in the existing LED dimming process, dimming circuit bears larger voltage.

[0005] To achieve the above-mentioned purpose, the utility model provides a kind of constant-current drive circuit of LED assembly first, including direct-current stabilizing circuit, constant-current control circuit, overvoltage acquisition circuit, feedback control circuit, feedback protection circuit and the LED assembly to be driven;

[0006] The input end of the direct-current stabilizing circuit is connected to the power supply, and the output end is connected to the positive electrode of the LED assembly to be driven, for inputting direct-current voltage to the LED assembly to be driven;

[0007] The negative electrode of the LED assembly to be driven is connected to the constant-current control circuit.

[0008] The constant-current control circuit is connected with analog dimming control signal, to adjust the current of the LED assembly to be driven according to the analog dimming control signal;

[0009] The input end and common end of the overvoltage acquisition circuit are connected to the two voltage acquisition ends of the constant-current control circuit respectively, and the output end is connected to the input end of the feedback control circuit, for connecting the constant-current control circuit and the feedback control circuit in the case that the voltage of the constant-current control circuit reaches the turn-on voltage of the overvoltage acquisition circuit;

[0010] The output end of the feedback control circuit is connected with the negative feedback end of the direct current stabilizing circuit, and the common end is connected with the feedback protection circuit, so that the direct current stabilizing circuit adjusts the output direct current voltage according to the feedback voltage input by the feedback control circuit.

[0011] Optionally, the constant current control circuit comprises a dimming transistor, a first sampling resistor, a second sampling resistor and a comparator.

[0012] The negative electrode of the comparator is connected with an analog dimming control signal, and the positive electrode is connected with the source electrode of the dimming transistor through the first sampling resistor.

[0013] The gate electrode of the dimming transistor is connected with the output end of the comparator, the drain electrode is connected with the negative electrode of the LED assembly to be driven, and the source electrode is connected with the ground through the second sampling resistor.

[0014] The drain electrode of the dimming transistor is used as the first voltage collection end of the constant current control circuit, and the source electrode is used as the second voltage collection end of the constant current control circuit and is connected with the overvoltage collection circuit, so as to collect the voltage of the constant current control circuit in the process of current control according to the analog dimming control signal.

[0015] Optionally, the overvoltage collection circuit comprises a first current limiting resistor and an overvoltage conducting transistor.

[0016] One end of the first current limiting resistor is connected with the first voltage collection end of the constant current control circuit, and the other end is connected with the base electrode of the overvoltage conducting transistor.

[0017] The emitter electrode of the overvoltage conducting transistor is used as the common end of the overvoltage collection circuit and is connected with the second voltage collection end of the constant current control circuit, and the collector electrode is used as the output end of the overvoltage collection circuit and is connected with the input end of the feedback control circuit.

[0018] The overvoltage conducting transistor is used for conducting the emitter electrode and the collector electrode to provide current to the feedback control circuit when the voltage provided by the constant current control circuit meets the conducting voltage.

[0019] Optionally, the feedback control circuit comprises a second current limiting resistor and a feedback control transistor.

[0020] One end of the second current limiting resistor is connected with the output end of the overvoltage collection circuit, and the other end is connected with the base electrode of the feedback control transistor.

[0021] The collector electrode of the feedback control transistor is connected with the negative feedback end of the direct current stabilizing circuit, and the emitter electrode is used as the common end of the feedback control transistor and is connected with the feedback protection circuit, so as to adjust the feedback voltage input of the direct current stabilizing circuit according to the feedback current output by the overvoltage collection circuit.

[0022] Optionally, the feedback protection circuit comprises a first protection resistor, a second protection resistor and a third protection resistor;

[0023] The first protection resistor, the second protection resistor and the third protection resistor are connected in series, the first non-common end of the series connection is connected to the output end of the DC voltage stabilizing circuit, and the second non-common end is grounded;

[0024] The common end of the second protection resistor and the third protection resistor is connected to the negative feedback end of the DC voltage stabilizing circuit and the collector of the feedback control transistor;

[0025] The common end of the first protection resistor and the second protection resistor is connected to the emitter of the feedback control transistor;

[0026] When the feedback control transistor is turned on but not saturated, the second protection resistor is used to shunt the feedback control transistor and adjust the voltage input to the negative feedback end of the DC voltage stabilizing circuit according to the change of the feedback current;

[0027] When the feedback control transistor is in a saturated conduction state, the first protection resistor and the third protection resistor are used to divide voltage to constrain the minimum voltage input to the negative feedback end;

[0028] When the feedback control transistor is in an off state, the first protection resistor, the second protection resistor and the third protection resistor are used to divide voltage to constrain the maximum voltage input to the negative feedback end.

[0029] Optionally, the circuit further comprises an integral filter circuit;

[0030] The integral filter circuit inputs a PWM pulse signal, and the output end is connected to the negative electrode of the comparator to convert the PWM pulse signal into a dimming control signal and input the comparator to perform dimming control on the LED in the LED assembly through the constant current control circuit.

[0031] Optionally, the dimming transistor is an N-type MOS transistor.

[0032] Optionally, the DC voltage stabilizing circuit comprises a switching power supply chip and an inductor;

[0033] The input end of the switching power supply chip is connected to a power supply, the switching pin is connected to the positive electrode of the LED assembly through the inductor, and the negative feedback pin is connected to the feedback control circuit;

[0034] The inductor is used to convert the switching voltage output by the switching pin into a direct current voltage.

[0035] Optionally, the LED assembly to be driven comprises a plurality of LEDs connected in series.

[0036] According to another aspect of the present application, a lamp for video recording is also provided, which comprises the constant current driving circuit of the LED assembly.

[0037] The constant current driving circuit of the LED assembly and the lamp for video recording provided by the present application can input a direct current voltage to the LED assembly to be driven through a direct current stabilizing circuit; adjust the current of the LED assembly to be driven according to an analog light modulation control signal through a constant current control circuit; collect the voltage of the constant current control circuit through an overvoltage collection circuit, and connect the constant current control circuit and the feedback control circuit when the voltage of the constant current control circuit reaches the turn-on voltage of the overvoltage collection circuit; input the feedback voltage to the feedback end of the direct current stabilizing circuit through the feedback control circuit and the feedback protection circuit, so that the direct current stabilizing circuit adjusts the output direct current voltage according to the feedback voltage input by the feedback control circuit. Through voltage feedback adjustment of the direct current stabilizing circuit, the voltage output of the direct current stabilizing circuit can be reduced when the voltage of the constant current control circuit is high, the voltage of the constant current control circuit is reduced, and the situation that the voltage of the constant current control circuit is too large and causes the heating of components during LED light modulation is avoided, thereby improving the reliability and service life of the constant current control circuit.

[0038] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0040] Figure 1 A circuit structure schematic diagram of the constant current driving circuit of the LED assembly provided by the embodiment of the present application is shown;

[0041] Figure 2 A circuit structure schematic diagram of another constant current driving circuit of the LED assembly provided by the embodiment of the present application is shown;

[0042] Figure 3 A circuit structure schematic diagram of still another constant current driving circuit of the LED assembly provided by the embodiment of the present application is shown. DETAILED DESCRIPTION

[0043] Hereinafter, the present application will be described in detail with reference to the drawings and embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0044] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined application purpose, the specific implementation, structure, features and effects according to the present application will be described in detail below with reference to the drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0045] The constant current driving circuit of the LED assembly according to some embodiments of the present application will be described below in combination with Figure 1 , Figure 2 and Figure 3 .

[0046] In one embodiment, as shown in Figure 1 , a constant current driving circuit of an LED assembly is provided, comprising a direct current stabilizing circuit 100, a constant current control circuit 200, an overvoltage acquisition circuit 300, a feedback control circuit 400, a feedback protection circuit 500 and a LED assembly to be driven 600.

[0047] In the above embodiment, the input end of the direct current stabilizing circuit 100 is connected to a power supply, and the output end is connected to the positive electrode of the LED assembly to be driven 600. The negative electrode of the LED assembly to be driven 600 is connected to the constant current control circuit 200. The constant current control circuit 200 is connected with an analog dimming control signal. The input end and the common end of the overvoltage acquisition circuit 300 are connected to two voltage acquisition ends of the constant current control circuit 200, respectively, to acquire the voltage of the constant current control circuit 200. The output end of the overvoltage acquisition circuit 300 is connected to the input end of the feedback control circuit 400. The output end of the feedback control circuit 400 is connected to the negative feedback end of the direct current stabilizing circuit 100, and the common end is connected to the feedback protection circuit 500, so that the direct current stabilizing circuit 100 realizes feedback regulation of the output voltage.

[0048] Working principle: the DC voltage stabilizing circuit 100 converts the power input from the power supply into a direct current voltage and supplies power to the LED assembly 600 to be driven. The constant current control circuit 200 serves as a dimming circuit, is connected to the other end of the LED assembly 600 to be driven, and adjusts the current of the LED assembly 600 to be driven according to the externally input analog dimming control signal, thereby realizing dimming of the LED assembly. The overvoltage acquisition circuit 300 acquires the voltage of the constant current control circuit 200, and when the voltage reaches a certain value, the transistor inside the overvoltage acquisition circuit 300 is turned on, thereby connecting the constant current control circuit 200 and the feedback control circuit 400. So that the feedback control circuit 400 adjusts the feedback voltage received by the negative feedback end of the DC voltage stabilizing circuit according to the feedback current output by the overvoltage acquisition circuit 300, so that the DC voltage stabilizing circuit 100 reduces the output direct current voltage according to the feedback voltage. Since the constant current control circuit 200 adjusts the current of the LED assembly 600 to be driven in a voltage division manner, when the direct current voltage output by the DC voltage stabilizing circuit 100 is reduced, the voltage across the constant current control circuit 200 is reduced, thereby avoiding the situation that the constant current control circuit 200 is heated due to high voltage.

[0049] It should be noted that the circuit function of the constant current driving circuit of the LED assembly provided in the embodiment is mainly realized through the circuit connection relationship between the various circuit modules, and does not depend on the program module in a certain circuit module for realization. In addition, each circuit module in the constant current driving circuit of the LED assembly can be realized by an analog circuit or a digital circuit, and for the circuit module which can implant a program module, the realization of the module function can be realized by the program module provided by the prior art.

[0050] The constant current driving circuit of the LED assembly provided by the utility model can input direct current voltage to the LED assembly to be driven through the DC voltage stabilizing circuit, adjust the current of the LED assembly to be driven through the constant current control circuit according to the analog dimming control signal, acquire the voltage of the constant current control circuit through the overvoltage acquisition circuit, and connect the constant current control circuit and the feedback control circuit when the voltage of the constant current control circuit reaches the turn-on voltage of the overvoltage acquisition circuit. The feedback control circuit and the feedback protection circuit input the feedback voltage to the feedback end of the DC voltage stabilizing circuit, so that the DC voltage stabilizing circuit adjusts the output direct current voltage according to the feedback voltage input by the feedback control circuit. Through voltage feedback regulation of the DC voltage stabilizing circuit, the voltage output of the DC voltage stabilizing circuit can be reduced when the voltage of the constant current control circuit is high, the voltage of the constant current control circuit is reduced, and the situation that the voltage of the constant current control circuit is too large and causes heating of components during LED dimming is avoided, thereby improving the reliability and service life of the constant current control circuit.

[0051] In one embodiment, asFigure 2 As shown, the constant current control circuit comprises a dimming transistor Q3, a first sampling resistor R4, a second sampling resistor R5 and a comparator U2. The negative electrode of the comparator U2 is connected to the analog dimming control signal (ADC_OUT), and the positive electrode is connected to the source electrode of the dimming transistor Q3 through the first sampling resistor R4. The gate electrode of the dimming transistor Q3 is connected to the output terminal of the comparator U2, the drain electrode is connected to the negative electrode of the LED assembly to be driven, and the source electrode is connected to the ground through the second sampling resistor R5. The drain electrode of the dimming transistor Q3 is used as the first voltage collection terminal of the constant current control circuit, and the source electrode is used as the second voltage collection terminal of the constant current control circuit and is connected to the overvoltage collection circuit, so as to collect the voltage of the constant current control circuit in the process of current control according to the analog dimming control signal.

[0052] Specifically, the comparator U2 comprises a positive electrode, a negative electrode and an output terminal. The negative electrode is connected to the external input for connecting the analog dimming control signal. The dimming transistor Q3 is a metal oxide semiconductor field effect transistor. Preferably, the dimming transistor Q3 is an N-type MOS tube, i.e. metal-oxide-semiconductor. The dimming transistor Q3 comprises a gate electrode, a source electrode and a drain electrode. The positive electrode of the comparator is connected to the source electrode of the dimming transistor Q3 through the first sampling resistor, and at the same time, the source electrode is connected to the ground through the second sampling resistor. The output terminal of the comparator is connected to the gate electrode of the dimming transistor Q3. The comparator provides a voltage to the gate electrode according to the analog dimming control signal, so that the dimming transistor Q3 is turned on with a corresponding current, and the voltage of the LED assembly to be driven is adjusted in a voltage dividing manner, thereby achieving the effect of current adjustment of the LED assembly to be driven. The first sampling resistor and the second sampling resistor are used for current collection in the constant current control circuit, thereby achieving precise current control.

[0053] The analog dimming control signal can be a direct analog signal or an analog signal converted from a digital signal (such as a pulse control signal). In the case where the analog dimming control signal is converted from a pulse control signal, the negative electrode of the comparator is also connected to an integral filter circuit. The integral filter circuit inputs a PWM (Pulse Width Modulation) pulse width modulation pulse signal to convert the PWM pulse signal into a dimming control signal, and inputs the constant current control circuit, so that the LED in the LED assembly to be driven can still be controlled in dimming mode in the case where the input control signal is a PWM pulse signal.

[0054] In one embodiment, as Figure 2As shown, the overvoltage acquisition circuit includes a first current-limiting resistor R7 and an overvoltage conducting transistor Q2; one end of the first current-limiting resistor R7 is connected to a first voltage acquisition end of the constant current control circuit, and the other end is connected to the base of the overvoltage conducting transistor Q2; the emitter of the overvoltage conducting transistor Q2 is connected to a second voltage acquisition end of the constant current control circuit as a common end of the overvoltage acquisition circuit, and the collector is connected to an input end of the feedback control circuit as an output end of the overvoltage acquisition circuit; the overvoltage conducting transistor Q2 is used to conduct the collector and the emitter to provide a current to the feedback control circuit when the voltage provided by the constant current control circuit meets the conduction voltage.

[0055] Specifically, the base and the emitter of the overvoltage conducting transistor Q2 are connected to the two voltage acquisition ends of the constant current control circuit. When the voltage of the constant current control circuit is too high and exceeds the conduction voltage (generally about 0.7V) of the base and the emitter of the overvoltage conducting transistor Q2, the overvoltage conducting transistor Q2 starts to conduct, and the collector current drives the feedback control circuit to conduct. The first current-limiting resistor R7 is used to limit the emitter current of the overvoltage conducting transistor Q2.

[0056] In one embodiment, as shown in Figure 2 The feedback control circuit includes a second current-limiting resistor R6 and a feedback control transistor Q1; one end of the second current-limiting resistor R6 is connected to the output end of the overvoltage acquisition circuit, and the other end is connected to the base of the feedback control transistor Q1; the collector of the feedback control transistor Q1 is connected to the negative feedback end of the DC voltage stabilizing circuit, and the emitter is connected to the feedback protection circuit as a common end of the feedback control transistor Q1, and is used to adjust the feedback voltage input of the DC voltage stabilizing circuit according to the feedback current output by the overvoltage acquisition circuit.

[0057] Specifically, after the overvoltage conducting transistor Q2 conducts and drives the feedback control transistor Q1 to conduct, the feedback control circuit adjusts the feedback voltage received by the negative feedback end of the DC voltage stabilizing circuit according to the feedback current output by the overvoltage acquisition circuit. The second current-limiting resistor R6 is used to limit the emitter current of the feedback control transistor Q1.

[0058] In one embodiment, as shown in Figure 2 The feedback protection circuit includes a first protection resistor R1, a second protection resistor R2, and a third protection resistor R3; the first protection resistor R1, the second protection resistor, and the third protection resistor R3 are connected in series, the first non-common end after the series connection is connected to the output end of the DC voltage stabilizing circuit, and the second non-common end is grounded; the common end of the second protection resistor R2 and the third protection resistor R3 is connected to the negative feedback end of the DC voltage stabilizing circuit and the collector of the feedback control transistor Q1; the common end of the first protection resistor R1 and the second protection resistor R2 is connected to the emitter of the feedback control transistor Q1.

[0059] Specifically, in the case that the feedback control transistor is turned on but not saturated, the second protective resistor R2 is shunted with the feedback control transistor Q1, and the voltage of the negative feedback end of the input DC voltage stabilizing circuit is adjusted according to the change of the current. In the case that the feedback control transistor Q1 is in the saturated on state, the voltage is divided by the first protective resistor R1 and the third protective resistor R3 to constrain the minimum voltage of the input negative feedback end. In the case that the feedback control transistor Q1 is in the off state, the voltage is divided by the first protective resistor R1, the second protective resistor R2 and the third protective resistor R3 to constrain the maximum voltage of the input negative feedback end.

[0060] In one embodiment, as shown in FIG. 1, the DC voltage stabilizing circuit comprises a switching power supply chip U1 and an inductor L1; the input end of the switching power supply chip U1 is connected with a power supply (Vin), the switching pin SW is connected with the positive pole of the LED assembly to be driven through the inductor U1, and the feedback control circuit is connected with the negative feedback pin FB; the inductor L1 is used to convert the switching voltage output by the switching pin into a DC voltage. Figure 2

[0061] Specifically, the ground pin of the switching power supply chip U1 is grounded. In the case that the voltage of the negative feedback pin FB is raised, the switching power supply chip U1 needs to adjust the duty cycle of the switching pin SW to keep the voltage of the negative feedback pin FB stable, thereby reducing the output voltage of the inductor L1 and the voltage output to the LED assembly to be driven, and the voltage can be regarded as unchanged, so the voltage across the constant current control circuit is reduced. When the voltage across the constant current control circuit is reduced to a certain extent and is lower than the on voltage of the overvoltage on transistor Q2, the on current of the overvoltage on transistor Q2 is reduced, the on current of the feedback control transistor Q1 is reduced accordingly, the voltage of the negative feedback pin FB is reduced, the DC output voltage of the switching power supply chip U1 is raised to maintain the voltage of the negative feedback pin FB, so that a negative feedback process is completed, and the voltage drop of the constant current control is always maintained near the on voltage of the overvoltage on transistor Q2, that is, the voltage across the constant current control circuit will not exceed 0.7V.

[0062] In the above embodiment, the LED assembly to be driven comprises a plurality of LEDs connected in series. The type of the LED can be a light scattering type or a light condensing type. The arrangement relationship between the LEDs can be linear (such as a lamp rod, a lamp strip, etc.), can be annular (such as an annular lamp strip), or can be matrix arrangement (such as a 2x2 array, a 3x3 array, etc.). The type and arrangement of the LED are not specifically limited in the present application.

[0063] In one embodiment, the LED assembly to be driven comprises six LEDs (LED1-LED6) connected in series. As shown in FIG. 2, the LED assembly to be driven comprises six LEDs (LED1-LED6) connected in series. Figure 3 Figure 3 ​As shown, the constant current control circuit includes: light modulation transistor Q3, first sampling resistor R4, second sampling resistor R5 and comparator U2, the overvoltage acquisition circuit includes: first current limiting resistor R7 and overvoltage conducting transistor Q2, the feedback control circuit includes: second current limiting resistor R6 and feedback control transistor Q1, the feedback protection circuit includes: first protection resistor R1, second protection resistor R2 and third protection resistor R3, switching power supply chip U1 and inductor L1.

[0064] Wherein, the negative electrode of comparator U2 is connected to the analog light modulation control signal, and the positive electrode is connected to the source electrode of light modulation transistor Q3 through first sampling resistor R4; the gate electrode of light modulation transistor Q3 is connected to the output end of comparator U2, the drain electrode is connected to the negative electrode of the LED assembly to be driven, and the source electrode is connected to the ground through second sampling resistor R5. The gate electrode of light modulation transistor Q3 is connected to one end of first current limiting resistor R7, and the source electrode is connected to the emitter electrode of overvoltage conducting transistor Q2. The other end of first current limiting resistor R7 is connected to the base electrode of overvoltage conducting transistor Q2. One end of second current limiting resistor R6 is connected to the collector electrode of overvoltage conducting transistor Q2, and the other end is connected to the base electrode of feedback control transistor Q1; the collector electrode of feedback control transistor Q1 is connected to the negative feedback pin FB of switching power supply chip U1, and the emitter electrode is connected to the common end of first protection resistor R1 and second protection resistor R2. First protection resistor R1, second protection resistor and third protection resistor R3 are connected in series, and the first non-common end connected in series is connected to the switching pin SW of switching power supply chip U1, and the second non-common end is connected to the ground. The common end of second protection resistor R2 and third protection resistor R3 is connected to the negative feedback pin FB of switching power supply chip U1, and is also connected to the collector electrode of feedback control transistor Q1.

[0065] Working principle: when the voltage of the source and drain of Q3 is high, and exceeds the on voltage of the base and emitter of Q2 (generally about 0.7V), Q2 starts to conduct, and the collector current of Q2 drives the base current of Q1, so that Q1 is turned on. After Q1 is turned on, R2 is shunted, the voltage drop of R2 is reduced, the voltage of FB pin of U1 is increased, U1 keeps the voltage of FB stable, adjusts the duty cycle of SW, and then reduces the output voltage of inductor L1, thereby reducing the positive voltage of the LED. Since the voltage drop of Q3 is equal to the difference between the output voltage of inductor L1 and the voltage of LED, and the voltage drop of LED is stable under a certain current, the voltage drop of Q3 is reduced. When the voltage drop of Q3 is reduced to a certain extent and is lower than the on voltage of the base and emitter of Q2, the conduction current of Q2 is reduced, the conduction current of Q1 is reduced, and the current of R2 starts to increase. The voltage of FB is reduced, and U1 controls the direct current output voltage to be increased in order to maintain the voltage of FB. Thus, a negative feedback process is completed, so that the voltage drop of Q3 is always maintained near the on voltage of the base and emitter of Q2, that is, the voltage drop of Q3 will not exceed 0.7V. When the voltage of the LED is too large or too small, causing the feedback current to exceed the standard, the protection resistors R1 and R2 start to work. If the feedback current is too large, Q1 is in a saturated conduction state, at this time the voltage drop of R2 is almost 0, the voltage of FB pin is determined by the voltage division of R1 and R3, and the direct current output voltage is maintained at a minimum value and cannot be too small to work. If the feedback current is too small, Q1 is cut off, at this time the voltage of FB pin is determined by the voltage division of R1+R2 and R3, and the direct current output voltage is maintained at a maximum value and cannot be too large to break the associated electronic components.

[0066] The constant current driving circuit of the LED assembly can input a direct current voltage to the LED assembly to be driven through a direct current stabilizing circuit; the current of the LED assembly to be driven is adjusted through a constant current control circuit according to an analog dimming control signal; the voltage of the constant current control circuit is collected through an overvoltage collection circuit, and the constant current control circuit and a feedback control circuit are connected in the case that the voltage of the dimming transistor exceeds the on voltage of the overvoltage on triode; the feedback voltage is input to the feedback end of the direct current stabilizing circuit through the feedback control circuit and the feedback protection circuit, so that the direct current stabilizing circuit adjusts the output direct current voltage according to the feedback voltage input by the feedback control circuit. The output direct current voltage of the direct current stabilizing circuit can be feedback adjusted according to the voltage condition of the dimming transistor through voltage feedback adjustment of the direct current stabilizing circuit, so that the dimming transistor is prevented from bearing too high voltage and causing components to heat. In addition, the overall heat and energy consumption of the LED driving circuit are reduced.

[0067] According to another aspect of the utility model, a lamp for camera shooting is also provided, the lamp for camera shooting includes the constant current driving circuit of LED assembly.

[0068] The above-described embodiments only express several implementation manners of the utility model, the description is more specific and detailed, but can not therefore be understood as the limitation of the utility model patent range. It should be pointed out that for ordinary skilled person in the art, without departing from the utility model concept, several modifications and improvements can be made, which belong to the protection range of the utility model. Therefore, the protection range of the utility model patent should be subject to the appended claims.

Claims

1. A constant current driving circuit for an LED assembly, characterized by, The LED driving device comprises a direct-current stabilizing circuit, a constant-current control circuit, an overvoltage acquisition circuit, a feedback control circuit, a feedback protection circuit and a LED component to be driven. An input end of the direct-current stabilizing circuit is connected with a power supply, and an output end thereof is connected with a positive electrode of the LED component to be driven, for inputting direct-current voltage to the LED component to be driven. A negative electrode of the LED component to be driven is connected with the constant-current control circuit. The constant-current control circuit is connected with an analog dimming control signal, for adjusting current of the LED component to be driven according to the analog dimming control signal. An input end and a common end of the overvoltage acquisition circuit are connected with two voltage acquisition ends of the constant-current control circuit respectively, and an output end thereof is connected with an input end of the feedback control circuit, for connecting the constant-current control circuit with the feedback control circuit when voltage of the constant-current control circuit reaches on voltage of the overvoltage acquisition circuit. An output end of the feedback control circuit is connected with a negative feedback end of the direct-current stabilizing circuit, and a common end thereof is connected with the feedback protection circuit, for adjusting output direct-current voltage of the direct-current stabilizing circuit according to feedback voltage inputted by the feedback control circuit.

2. The constant current driving circuit for LED assembly according to claim 1, wherein, The constant-current control circuit comprises a dimming transistor, a first sampling resistor, a second sampling resistor and a comparator. A negative electrode of the comparator is connected with the analog dimming control signal, and a positive electrode thereof is connected with a source electrode of the dimming transistor through the first sampling resistor. A gate electrode of the dimming transistor is connected with an output end of the comparator, a drain electrode thereof is connected with a negative electrode of the LED component to be driven, and the source electrode thereof is connected with ground through the second sampling resistor. The drain electrode of the dimming transistor is taken as a first voltage acquisition end of the constant-current control circuit, and the source electrode thereof is taken as a second voltage acquisition end of the constant-current control circuit and connected with the overvoltage acquisition circuit, for acquiring voltage of the constant-current control circuit in the process of current control according to the analog dimming control signal.

3. The constant current driving circuit for LED assembly according to claim 1 or 2, wherein The overvoltage acquisition circuit comprises a first current-limiting resistor and an overvoltage conduction transistor. One end of the first current-limiting resistor is connected with the first voltage acquisition end of the constant-current control circuit, and the other end thereof is connected with a base electrode of the overvoltage conduction transistor. An emitter electrode of the overvoltage conduction transistor is taken as a common end of the overvoltage acquisition circuit and connected with the second voltage acquisition end of the constant-current control circuit, and a collector electrode thereof is taken as an output end of the overvoltage acquisition circuit and connected with an input end of the feedback control circuit. The overvoltage conduction transistor is used for conducting the emitter electrode and the collector electrode when voltage provided by the constant-current control circuit meets on voltage, so as to provide current to the feedback control circuit.

4. The constant current driver circuit for LED assembly according to claim 3, wherein, The feedback control circuit comprises a second current-limiting resistor and a feedback control transistor. One end of the second current-limiting resistor is connected with the output end of the overvoltage acquisition circuit, and the other end thereof is connected with a base electrode of the feedback control transistor. A collector electrode of the feedback control transistor is connected with the negative feedback end of the direct-current stabilizing circuit, and an emitter electrode thereof is taken as a common end of the feedback control transistor and connected with the feedback protection circuit, for adjusting feedback voltage input of the direct-current stabilizing circuit according to feedback current outputted by the overvoltage acquisition circuit.

5. The constant current driver circuit for LED assemblies of claim 4, wherein, The feedback protection circuit comprises a first protection resistor, a second protection resistor and a third protection resistor; The first protection resistor, the second protection resistor and the third protection resistor are connected in series, and the first non-common end of the series connection is connected to the output end of the DC voltage stabilizing circuit, and the second non-common end is grounded; The common end of the second protection resistor and the third protection resistor is connected to the negative feedback end of the DC voltage stabilizing circuit and the collector of the feedback control triode; The common end of the first protection resistor and the second protection resistor is connected to the emitter of the feedback control triode; When the feedback control triode is turned on but not saturated, the second protection resistor is used to shunt the feedback control triode and adjust the voltage input to the negative feedback end of the DC voltage stabilizing circuit according to the change of the feedback current; When the feedback control triode is in a saturated conduction state, the first protection resistor and the third protection resistor are used to divide voltage to constrain the minimum voltage input to the negative feedback end; When the feedback control triode is in an off state, the first protection resistor, the second protection resistor and the third protection resistor are used to divide voltage to constrain the maximum voltage input to the negative feedback end.

6. The constant current driver circuit for LED assembly according to claim 2, wherein, The circuit further comprises an integral filter circuit; The integral filter circuit inputs a PWM pulse signal, and the output end is connected to the negative electrode of the comparator to convert the PWM pulse signal into a dimming control signal and input the comparator to perform dimming control on the LED in the LED assembly through the constant current control circuit.

7. The constant current driver circuit for LED assembly according to claim 2 or 6, wherein The dimming transistor is an N-type MOS transistor.

8. The constant current driver circuit for LED assemblies of claim 1, wherein, The DC voltage stabilizing circuit comprises a switching power supply chip and an inductor; The input end of the switching power supply chip is connected to a power supply, the switching pin is connected to the positive electrode of the LED assembly through the inductor, and the negative feedback pin is connected to the feedback control circuit; The inductor is used to convert the switching voltage output by the switching pin into a direct current voltage.

9. The constant current driver circuit for LED assemblies of any of claims 1-8, wherein, The LED assembly to be driven comprises a plurality of series-connected LEDs.

10. A camera lamp comprising the constant current driving circuit of the LED assembly according to any one of claims 1-9.

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