Large-current constant current source circuit

Abstract

The embodiment of the utility model discloses a large-current constant current source circuit which comprises a DC-DC step-down circuit, an amplifying circuit, a current sampling resistor, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U2A, and the output end of the DC-DC step-down circuit is connected with one end of the current sampling resistor and is connected with the positive electrode of the input end of the amplifier U2A through the resistor R3. The negative electrode of the input end of the amplifier U2A is connected with the other end of the current sampling resistor through a resistor R2, the positive electrode of the input end of the amplifier U2A is grounded through a resistor R4, and the two ends of a resistor R5 are connected with the negative electrode and the output end of the input end of the amplifier U2A respectively. The positive electrode of the input end of the amplifying circuit is connected with the output end of the amplifier U2A, and the output end is connected with the feedback end of the DC-DC step-down circuit. According to the utility model, the DC-DC step-down chip is adopted to be converted into the constant current source circuit through the peripheral circuit, the circuit debugging is simple, and the size of the load can be adjusted by adjusting the input voltage of the step-down chip; the system is low in cost, high in efficiency and simple to debug.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a large current constant current source circuit. Background Art

[0002] In the prior art, there are generally two ways to implement a large current constant current source circuit:

[0003] 1. Linear constant current source: Generally used for small current. The linear constant current source for large current has low efficiency and high heat generation.

[0004] 2. Switching type constant current source: There are few switching type constant current source chips to choose from and they are expensive. Utility Model Content

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a large current constant current source circuit to realize a large current constant current source and reduce costs.

[0006] In order to solve the above technical problems, an embodiment of the present utility model proposes a large current constant current source circuit, including a DC-DC buck circuit, an amplifying circuit, a current sampling resistor, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U2A. The output end of the DC-DC buck circuit is connected to one end of the current sampling resistor and is connected to the positive input end of the amplifier U2A through the resistor R3. The negative input end of the amplifier U2A is connected to the other end of the current sampling resistor through the resistor R2. The positive input end of the amplifier U2A is grounded through the resistor R4. The two ends of the resistor R5 are respectively connected to the negative input end and the output end of the amplifier U2A. The positive input end of the amplifying circuit is connected to the output end of the amplifier U2A. The output end of the amplifying circuit is connected to the feedback end of the DC-DC buck circuit.

[0007] Furthermore, the resistance values ​​of the resistors R2 , R3 , R4 and R5 are the same.

[0008] Furthermore, the DC-DC buck circuit consists of a DC-DC buck chip, an inductor L1, and a diode D1. The output end of the DC-DC buck chip is connected to the current sampling resistor and the resistor R3 through the inductor L1. The positive and negative poles of the diode D1 are respectively connected to the ground and the output end of the DC-DC buck chip.

[0009] Furthermore, a capacitor C1 is included, one end of the capacitor C1 is connected to the output end of the DC-DC step-down circuit, and the other end is grounded.

[0010] Furthermore, the amplifying circuit includes resistors R7, R8 and amplifier U2B. The positive input terminal of amplifier U2B is connected to the output terminal of amplifier U2A, the output terminal of amplifier U2B is connected to the feedback terminal of the DC-DC buck circuit, and the negative input terminal of amplifier U2B is connected to the output terminal of amplifier U2B and ground through resistors R7 and R8 respectively.

[0011] Furthermore, a resistor R6 is included, and the positive electrode of the input end of the amplifier circuit is connected to the output end of the amplifier U2A through the resistor R6.

[0012] Furthermore, the amplifier U2A is a differential amplifier.

[0013] The beneficial effects of the utility model are as follows: the utility model adopts a DC-DC step-down chip to convert into a constant current source circuit through a peripheral circuit, the circuit debugging of the utility model is simple, and the load size can be adjusted by adjusting the input voltage size of the step-down chip; the utility model has low cost, high efficiency and simple debugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a circuit diagram of a large current constant current source circuit according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0015] It should be noted that, unless there is a conflict, the embodiments in this application and the features described in the embodiments can be combined with each other. The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship and movement status of the various components under a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0017] In addition, in this utility model, the terms "first," "second," etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0018] Please refer to Figure 1 The high current constant current source circuit of the embodiment of the present utility model includes a DC-DC buck circuit, an amplifier circuit, a current sampling resistor, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U2A.

[0019] The output of the DC-DC step-down circuit is connected to the load through a current sampling resistor. The output of the DC-DC step-down circuit is connected to one end of the current sampling resistor and to the positive input of the amplifier U2A through resistor R3. The negative input of the amplifier U2A is connected to the other end of the current sampling resistor through resistor R2. The positive input of the amplifier U2A is grounded through resistor R4. The two ends of resistor R5 are respectively connected to the negative input and output of the amplifier U2A. The positive input of the amplifier circuit is connected to the output of the amplifier U2A. The output of the amplifier circuit is connected to the feedback end of the DC-DC step-down circuit.

[0020] Figure 1 In the circuit, resistor R1 is a current sampling resistor, and resistors R2, R3, R4, R5 and U2A are fully differential amplifiers that convert differential voltage into single-ended voltage.

[0021] As an implementation manner, the resistance values ​​of the resistors R2 , R3 , R4 , and R5 are the same.

[0022] As an implementation method, Figure 1 In the figure, U1 is a DC-DC buck chip. U1, inductor L1, and diode D1 form a typical DC-DC buck circuit. The DC-DC buck circuit consists of the DC-DC buck chip, inductor L1, and diode D1. The output of the DC-DC buck chip is connected to the current sampling resistor and resistor R3 through inductor L1. The positive and negative poles of diode D1 are connected to ground and the output of the DC-DC buck chip, respectively.

[0023] As an implementation manner, the high-current constant current source circuit further includes a capacitor C1 , one end of the capacitor C1 is connected to the output end of the DC-DC step-down circuit, and the other end is grounded.

[0024] As one embodiment, the amplifier circuit includes resistors R7 and R8, and amplifier U2B. R7, R8, and U2B form a 3x amplifier circuit. The positive input terminal of amplifier U2B is connected to the output terminal of amplifier U2A. The output terminal of amplifier U2B is connected to the feedback terminal of the DC-DC buck circuit. The negative input terminal of amplifier U2B is connected to the output terminal of amplifier U2B and ground through resistors R7 and R8, respectively.

[0025] The current can be adjusted at will through resistors R7 and R8, and the load size can also be adjusted by adjusting the input voltage.

[0026] As an implementation method, the high-current constant current source circuit further includes a resistor R6, and the positive electrode of the input end of the amplifier circuit is connected to the output end of the amplifier U2A through the resistor R6.

[0027] As an embodiment, amplifier U2A is a differential amplifier.

[0028] The working principle of this utility model is as follows: When the voltage at the feedback pin FB of the step-down chip U1 is 1.2V, the voltage at pin 6 of the amplifier U2B equals the voltage at pin 5, which equals 0.4V. Because R2 = R3 = R4 = R5, the amplification factor of the fully differential amplifier circuit is 1. The voltage across the sampling circuit R2 is also 0.4V, and the output current is constant at this point: 0.4 / R1 = 2A.

[0029] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high current constant current source circuit, characterized in that: It includes a DC-DC buck circuit, an amplifying circuit, a current sampling resistor, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U2A. The output end of the DC-DC buck circuit is connected to one end of the current sampling resistor and is connected to the positive input end of the amplifier U2A through the resistor R3. The negative input end of the amplifier U2A is connected to the other end of the current sampling resistor through the resistor R2. The positive input end of the amplifier U2A is grounded through the resistor R4. The two ends of the resistor R5 are respectively connected to the negative input end and the output end of the amplifier U2A. The positive input end of the amplifying circuit is connected to the output end of the amplifier U2A. The output end of the amplifying circuit is connected to the feedback end of the DC-DC buck circuit.

2. The high current constant current source circuit according to claim 1, wherein: The resistance values ​​of the resistors R2, R3, R4, and R5 are the same.

3. The high current constant current source circuit according to claim 1, characterized in that: The DC-DC step-down circuit consists of a DC-DC step-down chip, an inductor L1, and a diode D1. The output end of the DC-DC step-down chip is connected to the current sampling resistor and the resistor R3 through the inductor L1. The positive and negative poles of the diode D1 are respectively connected to the ground and the output end of the DC-DC step-down chip.

4. The high current constant current source circuit according to claim 1, wherein: The circuit further includes a capacitor C1 , one end of which is connected to the output end of the DC-DC step-down circuit, and the other end is grounded.

5. The high current constant current source circuit according to claim 1, wherein: The amplifier circuit includes resistors R7, R8 and amplifier U2B. The positive input terminal of amplifier U2B is connected to the output terminal of amplifier U2A, the output terminal of amplifier U2B is connected to the feedback terminal of the DC-DC buck circuit, and the negative input terminal of amplifier U2B is connected to the output terminal of amplifier U2B and ground through resistors R7 and R8 respectively.

6. The high current constant current source circuit according to claim 1, wherein: It also includes a resistor R6, and the positive input terminal of the amplifier circuit is connected to the output terminal of the amplifier U2A through the resistor R6.

7. The high current constant current source circuit according to claim 1, wherein: Amplifier U2A is a differential amplifier.

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