CN211509348U - LED lamp constant current output circuit with self-protection function - Google Patents

Abstract

The utility model discloses a constant current output circuit of an LED lamp with a self-protection function, comprising at least one matrix LED lamp, a matrix resistor having the same number as the matrix LED lamp, a feedback loop and a self-protection circuit, wherein the matrix resistor and the matrix LED lamp are connected in series to control the current balance of the matrix LED lamp by adjusting the voltage drop difference of the LED lamp, the feedback loop is connected to the matrix LED lamp, and the self-protection circuit is connected to the matrix LED lamp through the feedback loop to perform overvoltage protection and low-voltage automatic recovery on the LED lamp. The utility model abandons the traditional switching power supply, operational amplifier plus BJT circuit, reduces the use of chips such as EMI/switching voltage spikes/special switching power supply chips/high-frequency transformers, and thus reduces the hardware cost in the design process; and the utility model can achieve the control of current balance through simple resistors, has few components, and the process is simple and reliable, and is easy to promote.

Description

A LED lamp constant current output circuit with self-protection function

technical field

The utility model belongs to the technical field of LED constant current output circuits, in particular to an LED lamp constant current output circuit with a self-protection function.

Background technique

Household appliances, such as range hoods, steamers, ovens, etc., are often equipped with LED ambient lights on the display panels, and the lighting lamps used in daily life are generally driven by constant current power supplies; the existing constant current circuits are generally based on switching power supplies. The LED constant current circuit is used in high-power applications, and has the disadvantages of poor EMI effect, prominent switching spikes, and high circuit cost; there is also an LED constant current circuit based on operational amplifiers and transistors, which is used in low-power applications. , but its operating efficiency is low, less than 50%.

In addition, the main methods for the current balance control circuit of matrix LEDs on the market are generally: current control based on a dedicated LED constant current chip. This method is relatively simple in form and only requires a constant current chip; but the price of the dedicated chip is relatively simple. It is expensive, and in order to meet the function of the chip, more peripheral circuits and unit machines are required, which leads to high hardware cost, too many detection ports, and the LED current is greatly affected by temperature.

Utility model content

In order to solve the above problems, the present invention provides a constant current output circuit for LED lamps with self-protection function. Overvoltage protection and low voltage automatic recovery.

The technical scheme adopted by the utility model is:

A LED lamp constant current output circuit with self-protection function, which comprises at least one matrix LED lamp, the same number of matrix resistors as the matrix LED lamp, a feedback loop and a self-protection circuit, the matrix resistor and the matrix LED lamp The series connection is used to control the current balance of the matrix LED lamps by adjusting the voltage drop difference of the LED lamps, the feedback loop is connected with the matrix LED lamps, and the self-protection circuit is connected with the matrix LED lamps through the feedback loop for performing the LED lamps. Overvoltage protection and automatic recovery of low voltage.

Preferably, the feedback loop includes a third transistor Q3, the collector of the third transistor Q3 is connected to the matrix resistor, and the emitter of the third transistor Q3 is connected to the fourth resistor R4 , the other way is connected to the base of the seventh transistor Q7, the fourth resistor R4 is connected to the fourteenth resistor R14 and the eighth capacitor C8 in parallel and then grounded, and the emitter of the seventh transistor Q7 is grounded, so The base of the seventh transistor Q7 is connected to the base of the third transistor Q3 through the tenth resistor R10, one is connected to the self-protection circuit, the other is connected to the voltage dividing resistor unit, and the voltage dividing resistor unit is connected to the matrix. The LED lamp is connected, and the base of the seventh transistor Q7 is also grounded through the seventh capacitor C7.

Preferably, the voltage dividing resistor unit includes a sixth resistor R6 and a seventh resistor R7 connected in series, and the sixth resistor R6 and the seventh resistor R7 are connected in parallel with the eighth resistor R8 and the ninth resistor R9 respectively.

Preferably, the self-protection circuit includes a Zener diode D1, the cathode of the Zener diode D1 is connected to the input voltage VBAT, the anode is grounded through the first resistor R1, and the other is connected to the second transistor Q2 through the fifth resistor R5. The base of the first resistor R1 is connected in parallel with the fourth capacitor C4, the emitter of the second transistor Q2 is grounded with the first resistor R1, the collector of the second transistor Q2 is connected to the feedback loop connection.

Preferably, the matrix LED lamps include at least two parallel LED lamps, and the two LED lamps are located at the same ambient temperature to avoid different temperatures from affecting the accuracy of the current.

Preferably, the matrix resistors include at least two resistors, and the number of the resistors is the same as that of the LED lamps, and each of the resistors is connected in series with one LED lamp.

Preferably, any one of the LED lamps is connected in parallel with a capacitor for filtering the LED lamps.

Preferably, the resistor is a chip resistor.

Preferably, the ambient temperature is 24°C-26°C.

Compared with the prior art, the utility model has the following beneficial effects:

(1) Abandoning the traditional switching power supply, operational amplifier plus BJT circuit, reducing the use of EMI/switching voltage spikes/dedicated switching power supply chips/high-frequency transformers and other chips, thus reducing the hardware cost in the design process;

(2) The negative feedback linear LED constant current of double triode is adopted, which abandons the control port resources of the single-chip microcomputer, realizes the stable self-regulation of the LED lamp current, and reduces the development cost;

(3) By connecting a matrix resistor with a certain resistance and precision to the matrix LED lamp in series, the brightness, temperature and current accuracy of the LED lamp can be controlled; the current balance can be controlled through a simple resistor, with fewer components and less process. Simple and reliable, easy to promote;

(4) The working voltage of the negative feedback linear LED constant current circuit of the double triode is controlled by the self-protection circuit to realize the overvoltage protection function and the low voltage self-recovery function.

Description of drawings

1 is a system block diagram of an LED lamp constant current output circuit with self-protection function provided by an embodiment of the present invention;

2 is a circuit diagram of an LED lamp constant current output circuit with self-protection function provided by an embodiment of the present invention;

3 is a circuit diagram of a matrix LED lamp and a matrix resistor in an LED lamp constant current output circuit with self-protection function provided by an embodiment of the present invention;

4 is a temperature curve diagram of an LED lamp in an LED lamp constant current output circuit with a self-protection function provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model more clearly understood, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not intended to limit the present invention.

In the description of the present invention, it should be clear that the terms "vertical", "horizontal", "longitudinal", "front", "rear", "left", "right", "upper", "lower", The indicated orientation or positional relationship such as "horizontal" is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention, and does not mean that the referred device or element must have a specific orientation or position, so it cannot be It is understood as a limitation of the present invention.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it may be a fixed connection or a connectable connection. Removal connection, or integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

An embodiment of the present invention provides a constant current output circuit for an LED lamp with a self-protection function, as shown in FIG. 1 , which includes at least one matrix LED lamp 1 , a matrix resistor 2 with the same number as the matrix LED lamp 1 , a feedback Loop 3 and self-protection circuit 4, the matrix resistor 2 and the matrix LED lamp 1 are connected in series to control the current balance of the matrix LED lamp 1 by adjusting the voltage drop difference of the LED lamp, the feedback loop 3 and the matrix LED lamp 1 connection, the self-protection circuit 4 is connected to the matrix LED lamp 1 through the feedback loop 3 for overvoltage protection and low-voltage automatic recovery of the LED lamp;

In this way, using the above structure, the constant current output of the LED lamp is realized through the feedback loop 3;

By connecting a matrix resistor 2 with a certain resistance and precision in series with the matrix LED lamp 1, the brightness, temperature and current accuracy of the LED lamp can be controlled;

Through the setting of the self-protection circuit 4, overvoltage protection and low voltage automatic recovery of the LED lamp are realized.

Specifically, as shown in FIG. 2 , the feedback loop 3 includes a third transistor Q3, the collector of the third transistor Q3 is connected to the matrix resistor 2, and the emitter of the third transistor Q3 One of the poles is connected to the fourth resistor R4, and the other is connected to the base of the seventh transistor Q7. The fourth resistor R4 is connected to the fourteenth resistor R14 and the eighth capacitor C8 in parallel and then grounded. The emitter of the transistor Q7 is grounded, the base of the seventh transistor Q7 is connected to the base of the third transistor Q3 through the tenth resistor R10, one is connected to the self-protection circuit 4, and the other is connected to the voltage divider resistor. The unit 31 is connected, the voltage dividing resistor unit 31 is connected to the matrix LED lamp 1, and the base of the seventh transistor Q7 is also grounded through the seventh capacitor C7;

The matrix LED lamp 1 includes at least two parallel LED lamps 11, and the two LED lamps 11 are located at the same ambient temperature to prevent different temperatures from affecting the accuracy of the current;

The ambient temperature is 24°C-26°C, preferably 25°C;

In this way, according to the change of the LED "temperature-voltage offset" parameter (as shown in FIG. 4 ), the change of the ambient temperature will cause the voltage on the LED lamp 11 to change; Accuracy, the LED lamps 11 connected in parallel should be placed at the same heat source position; and the area of the heat dissipation copper foil should be as large as possible so that the position closest to 25°C is the optimal solution (such as the dotted line in Figure 4). In this way, the influence of temperature on the current accuracy is avoided.

As shown in FIG. 3 , the matrix resistor 2 includes at least two resistors 21 , and the number of the resistors 21 is the same as that of the LED lamps 11 , and each of the resistors 21 is connected in series with one LED lamp 11 ;

And, the LED lights 11 that make up the matrix LED lights 1 are of the same model;

The resistor 21 is a chip resistor.

In this embodiment, the matrix LED lamps 1 are provided with two groups, namely the first matrix LED lamps formed by the fourth diode D4 and the sixth diode D6 in parallel, and the third diode D3 and the fifth diode D6. The second matrix LED lamp formed by the diode D5 in parallel; in order to match the matrix LED lamp 1, the matrix resistor 2 in this embodiment is also provided with two groups, which are formed by a twelfth resistor R12 and a sixteenth resistor R16 in parallel. The first matrix resistor, and the second matrix resistor formed by the eleventh resistor R11 and the thirteenth resistor R13 in parallel, the fourth diode D4 and the twelfth resistor R12 are connected in series, the sixth diode D6 is connected in series with the sixteenth resistor R16, the third diode D3 is connected in series with the eleventh resistor R11, and the fifth diode D5 is connected in series with the thirteenth resistor R13.

Any one of the LED lights 11 is connected in parallel with a capacitor for filtering the LED lights 11;

In order to filter the LED lamp, in this embodiment, the fourth diode D4 is connected in parallel with the sixth capacitor C6, the sixth diode D6 is connected in parallel with the tenth capacitor C10, and the third diode D4 is connected in parallel with the tenth capacitor C10. The tube D3 is connected in parallel with the fifth capacitor C5, and the fifth diode D5 is connected in parallel with the ninth capacitor C9.

The principle of feedback loop 3 to realize negative feedback linear LED constant current output is:

The voltage dividing resistor unit 31 includes a sixth resistor R6 and a seventh resistor R7 connected in series, and the sixth resistor R6 and the seventh resistor R7 are connected in parallel with the eighth resistor R8 and the ninth resistor R9 respectively.

When the current of the set LED lamp 11 passes through the parallel resistance of the fourth resistor R4 and the fourteenth resistor R14, the voltage generated makes the seventh transistor Q7 turn on and is in an amplifying state; at this time, the collection through the seventh transistor Q7 After the electrode current is divided by the voltage dividing resistor unit 31 composed of R6, R7, R8 and R9, the collector-emitter voltage Vce_Q7 of the seventh transistor Q7 is obtained, and the third transistor Q3 is turned on through the tenth resistor R10; LED The currents of the lamps D3, D4, D5 and D6 continue to pass through the third transistor Q3, thereby establishing a normal negative feedback linear LED constant current output circuit.

The self-protection circuit 4 includes a Zener diode D1, the cathode of the Zener diode D1 is connected to the input voltage VBAT, the anode is grounded through the first resistor R1, and the other is through the fifth resistor R5 and the base of the second transistor Q2. The first resistor R1 is connected in parallel with the fourth capacitor C4, the emitter of the second transistor Q2 is grounded with the first resistor R1, and the collector of the second transistor Q2 is connected to the feedback loop 3 connections;

In this way, the principle of realizing overvoltage protection and low voltage automatic recovery through self-protection circuit 4 is:

Overvoltage self-protection principle:

When the input voltage VBAT is too high, the Zener diode D1 is reversely regulated and turned on; at this time, the voltage of the first resistor R1 is:

VR1=VBAT-VD1 (1)

In the formula, VBAT is the input voltage of the self-protection circuit 4; VR1 is the voltage of the first resistor R1; VD1 is the reverse conduction voltage drop of the Zener diode D1; The base voltage of the second transistor Q2 is Vbe_Q2=VR1 and it is turned on in saturation; the collector-emitter voltage of the second transistor Q2 is Vce_Q2=VBAT≈0V, so the third transistor Q3 is turned off and the fourth diode D4 is closed to realize overvoltage self-protection;

Low-voltage self-recovery principle:

After overvoltage protection, when the input voltage VBAT changes from high to low, the Zener diode D1 is reversely cut off; according to formula (1), it can be seen that VR1≈0V; the second transistor Q2 is turned off; the third transistor Q3 is turned on again , the fourth diode D4 is turned on to realize low-voltage automatic recovery.

In another embodiment, when one matrix LED light 1 and one matrix resistor 2 are provided, and two LED lights 11 are provided, the two LED lights 11 are the fourth diode D4 and the sixth diode D6 and the The fourth diode D4 and the sixth diode D6 are connected in series with a twelfth resistor R12 and a sixteenth resistor R12, respectively, and the twelfth resistor R12 and the sixteenth resistor R16 form a matrix resistor 2;

Under the same type of LED lamp 11, based on the same LED current, the forward voltage drop difference ΔV=|V _D4 -V _D6 |, where V _D4 and V _D4 are the fourth diode D4 and the sixth diode D4 respectively voltage at diode D6;

The fourth diode D4 is connected in series with the twelfth resistor R12, the sixth diode D6 is connected in series with the sixteenth resistor R16, and then D4&R12 and D6&R16 are connected in parallel, so the two parallel voltages are equal, and the maximum forward conduction of the matrix LED lamp 1 The voltage drop difference ΔV is equivalent to the voltage on the twelfth resistor R12 and the sixteenth resistor R16; therefore, the following formula is obtained:

V _D4 +I _D4 ×R12＝V _D6 +I _D6 ×R16

Wherein, I _D4 and I _D6 are the currents of the fourth diode D4 and the sixth diode D6, respectively;

Therefore, the unbalanced current of the matrix LED lamp 1 is ΔI=ΔV/R, wherein ΔI is the unbalanced current of the LED lamp 11 , and R is the resistance value of the twelfth resistor R12 and the sixteenth resistor R16 .

This embodiment abandons the traditional switching power supply, operational amplifier and BJT circuit, reduces the use of EMI/switching voltage spikes/dedicated switching power supply chips/high-frequency transformers and other chips, thus reducing the hardware cost in the design process; the use of double triodes The negative feedback linear LED constant current of the MCU eliminates the control port resources of the single-chip microcomputer, realizes the stable self-regulation of the LED lamp current, and reduces the development cost. Temperature and current accuracy; the current balance can be controlled by a simple resistor, with few components, the process is simple and reliable, and easy to popularize; the self-protection circuit is used to control the working voltage of the negative feedback linear LED constant current circuit of the double triode, Realize overvoltage protection function and low voltage self-recovery function.

There are two main factors that affect the current balance:

The first is temperature. In this embodiment, according to the change of the LED "temperature-voltage offset" parameter, the change of the ambient temperature will cause the voltage on the LED lamp to change; The LED lamps connected in parallel should be placed at the same heat source position; and the area of the heat dissipation copper foil should be as large as possible so that the position closest to 25°C is the optimal solution. In this way, the influence of temperature on the current accuracy is avoided;

The second is the voltage drop difference of the LED lamp itself. In this embodiment, a matrix resistor is connected in series with the matrix LED lamp, so that the forward voltage drop error of the matrix LED lamp itself can be solved;

Therefore, the present embodiment solves the problem of out-of-control current balance by limiting the ambient temperature of the LED lamps and connecting matrix resistors in series with the matrix LED lamps.

The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. The changes or replacements should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (9)

1. The utility model provides a LED lamp constant current output circuit with self preservation protects function, its characterized in that, its includes at least one matrix LED lamp (1), quantity with matrix resistance (2), feedback loop (3) and self preservation protection circuit (4) that matrix LED lamp (1) is the same, matrix resistance (2) and matrix LED lamp (1) are established ties and are used for the current balance through the poor control matrix LED lamp (1) of voltage drop who adjusts the LED lamp, feedback loop (3) and matrix LED lamp (1) are connected, self preservation protection circuit (4) are connected with matrix LED lamp (1) through feedback loop (3) and are used for carrying out overvoltage protection and low pressure automatic recovery to the LED lamp.

2. The constant current output circuit of claim 1, characterized in that the feedback loop (3) comprises a third transistor Q3, the collector of the third transistor Q3 being connected to a matrix resistor (2), one path of an emitting electrode of the third triode Q3 is connected with the fourth resistor R4, the other path of the emitting electrode is connected with the base electrode of the seventh triode Q7, the fourth resistor R4 is connected in parallel with the fourteenth resistor R14 and the eighth capacitor C8 and then grounded, the emitter of the seventh triode Q7 is grounded, one path of a base electrode of the seventh triode Q7 is connected with a base electrode of the third triode Q3 through a tenth resistor R10, one path of the base electrode is connected with the self-protection circuit (4), the other path of the base electrode is connected with the voltage-dividing resistor unit (31), the voltage-dividing resistor unit (31) is connected with the matrix LED lamp (1), and the base electrode of the seventh triode Q7 is grounded through a seventh capacitor C7.

3. The constant current output circuit of the LED lamp with the self-protection function as claimed in claim 2, wherein the voltage dividing resistor unit (31) comprises a sixth resistor R6 and a seventh resistor R7 connected in series, and the sixth resistor R6 and the seventh resistor R7 are respectively connected in parallel with an eighth resistor R8 and a ninth resistor R9.

4. The constant current output circuit of the LED lamp with the self-protection function of claim 3, wherein the self-protection circuit (4) comprises a Zener diode D1, the cathode of the Zener diode D1 is connected with the input voltage VBAT, the anode of the Zener diode D1 is connected with the ground through a first resistor R1, the other circuit of the Zener diode D1 is connected with the base of a second triode Q2 through a fifth resistor R5, the first resistor R1 is connected with a fourth capacitor C4 in parallel, the emitter of the second triode Q2 is connected with the first resistor R1 in common, and the collector of the second triode Q2 is connected with the feedback loop (3).

5. The LED lamp constant current output circuit with the self-protection function according to any one of claims 1 to 4, wherein the matrix LED lamp (1) comprises at least two LED lamps (11) connected in parallel, and the two LED lamps (11) are located at the same ambient temperature for avoiding different temperatures from influencing the accuracy of the current.

6. The LED lamp constant current output circuit with the self-protection function of claim 5, wherein the matrix resistor (2) comprises at least two resistors (21), the number of the resistors (21) is the same as that of the LED lamps (11), and each resistor (21) is connected with one LED lamp (11) in series.

7. The LED lamp constant current output circuit with the self-protection function of claim 6, wherein any one of the LED lamps (11) is connected with a capacitor in parallel for filtering the LED lamp (11).

8. The constant current output circuit of the LED lamp with the self-protection function as claimed in claim 7, wherein the resistor (21) is a chip resistor.

9. The constant current output circuit of the LED lamp with the self-protection function of claim 8, wherein the ambient temperature is 24-26 ℃.

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