Circuit for realizing constant current function based on linear voltage regulator

Abstract

The utility model discloses a circuit for realizing a constant current function based on a linear voltage regulator, which belongs to the technical field of light-emitting diode (LED) circuits, and comprises a voltage stabilizing module, a direct current power supply and an LED lamp string, the first end of the sampling resistor is connected with the output end of the linear voltage regulator and the voltage feedback end of the linear voltage regulator. A second end of the sampling resistor is connected with a ground pin of the linear voltage regulator; the direct-current power supply is directly connected with one end, with the same polarity, of the LED lamp string; and the direct-current power supply is connected with the other end, with the same polarity, of the LED lamp string through the voltage stabilizing module. In the working process of the circuit for realizing the constant current function based on the linear voltage regulator disclosed by the utility model, the purpose of stabilizing the current flowing through the LED lamp string can be realized.

Description

Technical Field

[0001] The utility model belongs to the technical field of LED circuits. Specifically, the utility model relates to a circuit for realizing a constant current function based on a linear voltage regulator. Background Art

[0002] Compared with traditional lighting lamps, LED lamps have the advantages of high luminous efficiency, long service life, low power consumption, safety and no pollution, etc. They have been widely used in many occasions and gradually replaced traditional lighting lamps such as incandescent lamps and fluorescent lamps. At the same time, with the wide application of LED lamps, LED driving technology has become increasingly mature.

[0003] A lighting control circuit for an LED is disclosed in Patent CN101835306B, which includes a control module, a driving module and a step-down voltage stabilizing module. The step-down voltage stabilizing module performs step-down processing on the DC voltage provided by a DC power supply to generate a DC low voltage, and the DC low voltage supplies power to the control module. The DC power supply also provides a working voltage for the driving module. It is characterized in that the control module samples the DC voltage provided by the DC power supply to obtain a power supply voltage sampling value. If the power supply voltage sampling value is less than a first preset voltage threshold set therein, a low power warning control signal is generated; when the driving module receives the low power warning control signal, it controls the LED light source to flash in a first state to generate a low power warning; the step-down voltage stabilizing module includes a linear voltage regulator, the input end of the linear voltage regulator is connected to the DC power supply, and the output end of the linear voltage regulator outputs the DC low voltage. A capacitor C1 and a capacitor C2 connected in parallel are connected between the input end of the linear voltage regulator and the ground, and a capacitor C4 and a capacitor C5 connected in parallel are connected between the output end of the linear voltage regulator and the ground. However, the technologies disclosed in the above patent and the prior art cannot achieve the purpose of stabilizing the current flowing through the LED lamp string. Summary of the Utility Model

[0004] The technical problem to be solved by the utility model is to provide a circuit for realizing a constant current function based on a linear voltage regulator aiming at the deficiencies of the prior art, so as to achieve the purpose of stabilizing the current flowing through the LED lamp string.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] The utility model provides a circuit for realizing a constant current function based on a linear voltage regulator, which includes a voltage regulation module, a DC power supply and an LED lamp string. Among them, the voltage regulation module includes a linear voltage regulator and a sampling resistor. The first end of the sampling resistor is respectively connected to the output end of the linear voltage regulator and the voltage feedback end of the linear voltage regulator; the second end of the sampling resistor is connected to the ground pin of the linear voltage regulator; one end of the DC power supply and the LED lamp string with the same polarity are directly connected; the other end of the DC power supply and the LED lamp string with the same polarity is connected through the voltage regulation module.

[0007] Further, the positive pole of the DC power supply is directly connected to the positive pole of the LED lamp string; the negative pole of the LED lamp string is connected to the input end of the linear voltage regulator; the negative pole of the DC power supply is connected to the second end of the sampling resistor and the ground pin of the linear voltage regulator, and is grounded.

[0008] Further, the negative pole of the DC power supply is directly connected to the negative pole of the LED lamp string and is grounded; the positive pole of the LED lamp string is connected to the second end of the sampling resistor; the positive pole of the DC power supply is connected to the input end of the linear voltage regulator.

[0009] Further, when the current flowing through the LED lamp string increases, the voltage across the sampling resistor increases. When the voltage across the sampling resistor is greater than the voltage at the voltage feedback end of the linear voltage regulator, the linear voltage regulator will control to increase the voltage between its input end and output end.

[0010] Further, when the current flowing through the LED lamp string decreases, the voltage across the sampling resistor decreases. When the voltage across the sampling resistor is less than the voltage at the voltage feedback end of the linear voltage regulator, the linear voltage regulator will control to decrease the voltage between its input end and output end.

[0011] Further, after the voltage between the input end and output end of the linear voltage regulator increases, the voltage across the LED lamp string decreases, and then the current flowing through the LED lamp string decreases.

[0012] Further, after the voltage between the input end and output end of the linear voltage regulator decreases, the voltage across the LED lamp string increases, and then the current flowing through the LED lamp string increases.

[0013] The circuit for realizing the constant current function based on the linear voltage regulator of the utility model has the following advantages:

[0014] (1) Through the circuit for realizing the constant current function based on the linear voltage regulator of the utility model, the current flowing through the LED lamp string can be stabilized.

[0015] (2) In the circuit for realizing the constant current function based on the linear voltage regulator of the utility model, overcurrent protection for the LED lamp string can be realized through the overcurrent protection function of the linear voltage regulator itself, without the need to additionally increase a circuit.

[0016] (3) In the circuit of the present utility model for realizing the constant current function based on a linear voltage regulator, high constant current accuracy of the circuit can be achieved through the high constant voltage accuracy of the linear voltage regulator itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] This specification includes the following drawings, and the shown contents are respectively:

[0018] Figure 1 The logic structure block diagram of the circuit of the present utility model for realizing the constant current function based on a linear voltage regulator;

[0019] Figure 2 is the circuit diagram of the first specific embodiment of the present utility model;

[0020] Figure 3 is the circuit diagram of the second specific embodiment of the present utility model.

[0021] Description of the reference numerals: 1, voltage regulation module; 2, DC power supply; 3, LED lamp string; 4, linear voltage regulator; 5, sampling resistor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following will further describe in detail the specific embodiments of the present utility model with reference to the drawings through the description of the embodiments, aiming to help those skilled in the art have a more complete, accurate and in-depth understanding of the concept and technical solution of the present utility model and contribute to its implementation.

[0023] Figure 1 The logic structure block diagram of the circuit of the present utility model for realizing the constant current function based on a linear voltage regulator 4 includes a voltage regulation module 1, a DC power supply 2 and an LED lamp string 3. Among them, the voltage regulation module 1 includes a linear voltage regulator 4 and a sampling resistor 5. The first end of the sampling resistor 5 is respectively connected to the output end of the linear voltage regulator 4 and the voltage feedback end of the linear voltage regulator 4; the second end of the sampling resistor 5 is connected to the ground pin of the linear voltage regulator 4; one end of the DC power supply 2 and the LED lamp string 3 with the same polarity are directly connected; the other end of the DC power supply 2 and the LED lamp string 3 with the same polarity are connected through the voltage regulation module 1.

[0024] Figure 2 is the circuit diagram of the first specific embodiment of the present utility model, Figure 2As can be seen, the first end of the sampling resistor 5 is respectively connected to the output end and the voltage feedback end of the linear voltage regulator 4; the second end of the sampling resistor 5 is connected to the ground pin of the linear voltage regulator 4; the positive pole of the DC power supply 2 is directly connected to the positive pole of the LED lamp string 3; the negative pole of the LED lamp string 3 is connected to the input end of the linear voltage regulator 4; the negative pole of the DC power supply 2 is connected to the second end of the sampling resistor 5 and the ground pin of the linear voltage regulator 4, and is grounded. In the first specific embodiment, the working principle and process of the circuit for realizing the constant current function based on the linear voltage regulator 4 of the present invention are as follows. In Figure 2 During the working process of the circuit, when the current flowing through the LED lamp string 3 increases, the voltage across the sampling resistor 5 increases. When the voltage across the sampling resistor 5 is greater than the voltage at the voltage feedback end of the linear voltage regulator 4, the linear voltage regulator 4 will control to increase the voltage between its input end and output end. After the voltage between the input end and output end of the linear voltage regulator 4 increases, the voltage across the LED lamp string 3 decreases, and then the current flowing through the LED lamp string 3 decreases, thereby realizing the stabilization of the current flowing through the LED lamp string 3. In Figure 2 During the working process of the circuit, when the current flowing through the LED lamp string 3 decreases, the voltage across the sampling resistor 5 decreases. When the voltage across the sampling resistor 5 is less than the voltage at the voltage feedback end of the linear voltage regulator 4, the linear voltage regulator 4 will control to decrease the voltage between its input end and output end. After the voltage between the input end and output end of the linear voltage regulator 4 decreases, the voltage across the LED lamp string 3 increases, and then the current flowing through the LED lamp string 3 increases, thereby realizing the stabilization of the current flowing through the LED lamp string 3. In Figure 2 During the working process of the circuit, when the voltage across the two ends of the sampling resistor 5 is equal to the voltage at the voltage feedback end of the linear voltage regulator 4, the linear voltage regulator 4 does not control to change the voltage between its input end and output end.

[0025] Figure 3 is the circuit diagram of the second specific embodiment of the present invention, Figure 3 As can be seen, the first end of the sampling resistor 5 is respectively connected to the output end and the voltage feedback end of the linear voltage regulator 4; the second end of the sampling resistor 5 is connected to the ground pin of the linear voltage regulator 4; the negative pole of the DC power supply 2 is directly connected to the negative pole of the LED lamp string 3 and is grounded; the positive pole of the LED lamp string 3 is connected to the second end of the sampling resistor 5; the positive pole of the DC power supply 2 is connected to the input end of the linear voltage regulator 4. In the second specific embodiment, the working principle and process of the circuit for realizing the constant current function based on the linear voltage regulator 4 of the present invention are as follows. In Figure 3During the operation of the circuit, when the current flowing through the LED string 3 increases, the voltage across the sampling resistor 5 increases. When the voltage across the sampling resistor 5 is greater than the voltage at the voltage feedback terminal of the linear voltage regulator 4, the linear voltage regulator 4 will control to increase the voltage between its input terminal and output terminal. After the voltage between the input terminal and output terminal of the linear voltage regulator 4 increases, the voltage across the LED string 3 decreases, and then the current flowing through the LED string 3 decreases, thereby achieving the stability of the current flowing through the LED string 3. In Figure 3 During the operation of the circuit, when the current flowing through the LED string 3 decreases, the voltage across the sampling resistor 5 decreases. When the voltage across the sampling resistor 5 is less than the voltage at the voltage feedback terminal of the linear voltage regulator 4, the linear voltage regulator 4 will control to decrease the voltage between its input terminal and output terminal. After the voltage between the input terminal and output terminal of the linear voltage regulator 4 decreases, the voltage across the LED string 3 increases, and then the current flowing through the LED string 3 increases, thereby achieving the stability of the current flowing through the LED string 3. In Figure 3 During the operation of the circuit, when the voltage across the sampling resistor 5 is equal to the voltage at the voltage feedback terminal of the linear voltage regulator 4, the linear voltage regulator 4 does not control to change the voltage between its input terminal and output terminal.

[0026] The above-mentioned in Figure 2 circuit, Figure 3 During the operation of the circuit, when the current flowing through the LED string 3 increases or decreases, it will cause Figure 2 circuit, Figure 3 an increase or decrease in the voltage across the sampling resistor 5 in the circuit. When the linear voltage regulator 4 detects that the voltage at its voltage feedback terminal is less than or greater than the voltage across the sampling resistor 5, the linear voltage regulator 4 will control to increase or decrease the voltage between its input terminal and output terminal until the voltage at the voltage feedback terminal of the linear voltage regulator 4 is equal to the voltage across the sampling resistor 5, so as to achieve the purpose of stabilizing the current flowing through the LED string 3.

[0027] The stability of the current flowing through the LED string 3 achieved by the circuit of the present utility model is a dynamic current stability, that is, during the operation of the circuit of the present utility model, as long as the linear voltage regulator 4 detects that the voltage at its voltage feedback terminal is less than or greater than the voltage across the sampling resistor 5, the linear voltage regulator 4 will adjust the current flowing through the LED string 3 by controlling to increase or decrease the voltage between its input terminal and output terminal. In addition, the circuit of the present utility model for realizing the constant current function based on the linear voltage regulator 4 is not only applicable to the LED string 3, but also equally applicable to LED lamps and LED backlight products, etc.

[0028] The above has made an exemplary description of the present utility model in conjunction with the accompanying drawings. Obviously, the specific implementation of the present utility model is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present utility model; or without improvement, the above concept and technical solution of the present utility model are directly applied to other occasions, they are all within the protection scope of the present utility model.

Claims

1. A circuit for realizing a constant current function based on a linear regulator, characterized in that: It includes a voltage stabilizing module, a DC power supply and an LED light string, wherein the voltage stabilizing module includes a linear voltage regulator and a sampling resistor, the first end of the sampling resistor is respectively connected to the output end of the linear voltage regulator and the voltage feedback end of the linear voltage regulator; the second end of the sampling resistor is connected to the ground pin of the linear voltage regulator; the DC power supply is directly connected to one end of the LED light string with the same polarity; the DC power supply is connected to the other end of the LED light string with the same polarity through the voltage stabilizing module.

2. A circuit for realizing a constant current function based on a linear regulator as claimed in claim 1, characterized in that: The positive electrode of the DC power supply is directly connected to the positive electrode of the LED light string; the negative electrode of the LED light string is connected to the input end of the linear regulator; the negative electrode of the DC power supply is connected to the second end of the sampling resistor and the ground pin of the linear regulator, and is grounded.

3. A circuit for realizing a constant current function based on a linear regulator as claimed in claim 1, characterized in that: The negative electrode of the DC power supply is directly connected to the negative electrode of the LED light string and is grounded; the positive electrode of the LED light string is connected to the second end of the sampling resistor; and the positive electrode of the DC power supply is connected to the input end of the linear regulator.

4. A circuit for realizing a constant current function based on a linear regulator as claimed in any one of claims 2 and 3, characterized in that: When the current flowing through the LED light string increases, the voltage across the sampling resistor increases. When the voltage across the sampling resistor is greater than the voltage at the voltage feedback end of the linear regulator, the linear regulator controls the voltage between its input and output ends to increase.

5. A circuit for realizing a constant current function based on a linear regulator as claimed in any one of claims 2 and 3, characterized in that: When the current flowing through the LED light string decreases, the voltage across the sampling resistor decreases. When the voltage across the sampling resistor is less than the voltage at the voltage feedback end of the linear regulator, the linear regulator controls the voltage between its input and output ends to decrease.

6. A circuit for realizing a constant current function based on a linear regulator as claimed in claim 4, characterized in that: When the voltage between the input end and the output end of the linear regulator increases, the voltage across the LED light string decreases, thereby reducing the current flowing through the LED light string.

7. A circuit for realizing a constant current function based on a linear regulator as claimed in claim 5, characterized in that: After the voltage between the input end and the output end of the linear regulator decreases, the voltage across the LED light string increases, and thus the current flowing through the LED light string increases.

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