Constant current drive circuit

Abstract

The application provides a constant current driving circuit, which outputs a first current and a second current with a constant sum of current values through a current output module, then the first current is received and copied by a mirror module, a driving current is output, a measurement and adjustment module measures the driving voltage of the mirror module, and when the driving voltage changes, the second current is adjusted in the same direction, so that the first current is adjusted in the opposite direction, and the driving current is finally realized to be constant output. The constant current driving circuit has the advantages of simple structure, small chip area and high cost performance.

Description

Technical Field

[0001] This application relates to the field of drive technology, and in particular to a constant current drive circuit. Background Technology

[0002] Constant current drive circuits have a wide range of applications, such as LED billboard lights and decorative LED lights on the market. These lights are powered by the constant current drive circuits within the chips. The commonly used constant current output circuits operate on the following principles: Figure 1 As shown, the bias current IBIAS serves as the reference current for the constant current output. The current ratios of M17 and M16 are equal. M16 consists of N MOSFETs connected in parallel, and M17 consists of M MOSFETs connected in parallel. Therefore, IB(M17) / M = IB(M16) / N. Since the current of M16 is IBIAS, IB(M17) = M * IB(M16) / N. Typically, M is much larger than N. This is because to achieve a precise replication circuit and a stable output current IOUT, the Vo of the MOSFETs is required. GS and V DS They are all equal, now the V of the M16 and M17 GS Since the voltages are equal, only V needs to be designed. DS This equals VDS_DRV. Operational amplifier OP2 and MOSFET M19 are used to achieve V... DS It is designed to be equal to VDS_DRV. A reference voltage VR is also required, which is made possible by operational amplifier OP1. DS =VR.

[0003] However, the above constant current drive circuit requires multiple operational amplifiers, making the circuit complex and consuming a large chip area. When we only need to achieve a simple constant current drive output, such as for application in some circuit indicator lights, the above circuit is not cost-effective. Summary of the Invention

[0004] This application relates to a constant current drive circuit with a simple circuit structure and high cost performance.

[0005] A constant current drive circuit, comprising:

[0006] A current output module, wherein a first output terminal of the current output module is used to output a first current, and a second output terminal of the current output module is used to output a second current; wherein the sum of the current values ​​of the first current and the second current is constant;

[0007] A mirror module, the input terminal of which is connected to the first output terminal of the current output module, is used to replicate the first current and output a drive current through the output terminal of the mirror module;

[0008] The measurement and adjustment module is connected to the second output terminal of the current output module and the output terminal of the mirror module, respectively, and is used to measure the driving voltage of the mirror module. If the driving voltage changes, the second current is adjusted; wherein the adjustment direction of the second current is the same as the change direction of the driving voltage.

[0009] In one embodiment, the third output terminal of the current output module is used to output a constant current;

[0010] The measurement and adjustment module includes switching transistors M1, M2, and M3. The control terminal and first terminal of switching transistor M1 are connected to the control terminal of switching transistor M2, and are also connected to the third output terminal of the current output module. The second terminal of switching transistor M1 is connected to the output terminal of the mirror module. The first terminal of switching transistor M2 is connected to the second output terminal of the current output module. The second terminal of switching transistor M2 is connected to the first terminal of switching transistor M3. The second terminal of switching transistor M3 is connected to the first power supply terminal. The control terminal of switching transistor M3 is used to receive the conduction voltage.

[0011] In one embodiment, the current output module includes switching transistors M4, M5, M6, M7, M8, M9, and M10.

[0012] The first ends of switching transistors M4, M5, M6, and M7 are connected together and connected to a second power supply terminal. The second end of switching transistor M7, the control terminal of switching transistor M7, the control terminal of switching transistor M8, the control terminal of switching transistor M9, and the control terminal of switching transistor M10 are connected together and connected to a first current source. The second end of switching transistor M4 is connected to the first end of switching transistor M8. The control terminals of switching transistors M4, M5, M6, and M8 are connected together and connected to a second current source. The second end of switching transistor M5 and the first end of switching transistor M9 are connected together and serve as the second output terminal of the current output module. The second end of switching transistor M9 serves as the first output terminal of the current output module. The first end of switching transistor M10 is connected to the second end of switching transistor M6 and serves as the third output terminal of the current output module.

[0013] In one embodiment, the mirror module includes a switching transistor M11 and a switching transistor M12. The first end and the control end of the switching transistor M11 are connected together with the control end of the switching transistor M12 and are connected to the first output end of the current output module. The second end of the switching transistor M11 and the second end of the switching transistor M12 are connected together and are connected to the first power supply end. The first end of the switching transistor M12 serves as the output end of the mirror module.

[0014] In one embodiment, the control terminal of the switching transistor M3 is also connected to the control terminal of the switching transistor M11 to obtain the voltage at the control terminal of the switching transistor M11 as the turn-on voltage.

[0015] In one embodiment, the switching transistors M1, M2, and M3 are N-type MOS transistors.

[0016] In one embodiment, the switching transistors M4, M5, M6, M7, M8, M9, and M10 are P-type MOS transistors.

[0017] In one embodiment, the switching transistors M11 and M12 are N-type MOS transistors.

[0018] The constant current drive circuit described above outputs a first current and a second current with a constant sum of current values ​​through a current output module. The first current is then received and mirrored by a mirror module, which outputs a drive current. A measurement and adjustment module measures the drive voltage of the mirror module. When the drive voltage changes, the second current is adjusted in the same direction, thereby achieving the purpose of adjusting the first current and then the drive current in the opposite direction. Ultimately, a constant output of drive current is achieved. This constant current drive circuit has a simple structure, occupies a small chip area, and has a high cost-performance ratio. Attached Figure Description

[0019] Figure 1 This is a circuit structure diagram of a constant current drive circuit in the prior art;

[0020] Figure 2 This is a structural block diagram of a constant current drive circuit according to an embodiment of this application;

[0021] Figure 3 This is a structural block diagram of a constant current drive circuit according to another embodiment of this application;

[0022] Figure 4 This is a structural block diagram of a constant current drive circuit according to another embodiment of this application;

[0023] Figure 5 This is a structural block diagram of a constant current drive circuit according to another embodiment of this application;

[0024] Figure 6 This is a structural block diagram of a constant current drive circuit according to another embodiment of this application;

[0025] Figure 7 This is a structural block diagram of a constant current drive circuit according to another embodiment of this application;

[0026] Figure 8 This is a comparison graph showing the change of drive current with drive voltage when there is feedback regulation and no feedback regulation in this application. Detailed Implementation

[0027] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly. The connection can be a direct connection or an indirect connection.

[0030] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0031] Figure 2This is a block diagram of a constant current driving circuit according to an embodiment. The constant current driving circuit includes a current output module 111, a mirror module 112, and a measurement and adjustment module 113. The first output terminal (port a in the figure) of the current output module 111 is used to output a first current, and the second output terminal (port b in the figure) of the current output module 111 is used to output a second current; wherein the sum of the current values ​​of the first current and the second current is constant; the input terminal of the mirror module 112 is connected to the first output terminal of the current output module 111, and the mirror module 112 is used to replicate the first current and output the driving current Iout through the output terminal of the mirror module; the measurement and adjustment module 113 is connected to the second output terminal of the current output module 111 and the output terminal of the mirror module 112 respectively, and is used to measure the driving voltage of the mirror module 112. If the driving voltage changes, the second current is adjusted; wherein the adjustment direction of the second current is the same as the change direction of the output voltage.

[0032] It is understood that the current output module 111 can output a first current, and the mirror module 112 can copy the first current and output the copied drive current (represented by Iout in the figure) through its output terminal. The drive current copied and output by the mirror module 112 is related not only to the first current, but also to the drive voltage at the output terminal (represented by VDS_DRV in the figure). In order to avoid the influence of the drive voltage fluctuation on the copied output current, the measurement adjustment module 113 can be used to adjust the first current by feedback.

[0033] Specifically, the current output module 111 can also output a second current, and the measurement and adjustment module 113 can measure the driving voltage of the mirror module 112. When the driving voltage changes, the second current is adjusted. Since the sum of the first current and the second current is constant, the direction of change of the first current is opposite to the direction of adjustment of the second current, and thus opposite to the direction of change of the driving voltage. Therefore, when the driving voltage increases, the measurement and adjustment module 113 can increase the second current, thereby decreasing the first current, that is, decreasing the driving current copied and output by the mirror module 112; when the driving voltage decreases, the measurement and adjustment module 113 can decrease the second current, thereby increasing the first current, that is, increasing the driving current copied and output by the mirror module 112. In this way, the measurement and adjustment module 113 can suppress the influence of driving voltage fluctuations on the driving current, realize feedback regulation of the driving current copied and output by the mirror module 112, and ultimately achieve a constant output of driving current.

[0034] The constant current drive circuit of this embodiment outputs a first current and a second current with a constant sum of current values ​​through the current output module 111. Then, the mirror module 112 receives and mirrors the first current to output the drive current. The measurement and adjustment module 113 measures the drive voltage of the mirror module 112. When the drive voltage changes, the second current is adjusted in the same direction, thereby achieving the purpose of adjusting the first current and then the drive current in the opposite direction, and finally realizing the constant output of the drive current. The constant current drive circuit of this embodiment has a simple structure and occupies a small chip area. Compared with conventional constant current drive output circuits, it greatly reduces the production cost and has a high cost performance.

[0035] In one embodiment, such as Figure 3 As shown, the third output terminal of the current output module 111 is used to output a constant current; the measurement and adjustment module 113 includes switching transistors M1, M2, and M3. The control terminal and first terminal of switching transistor M1 are connected together with the control terminal of switching transistor M2 and are connected to the third output terminal of the current output module 111; the second terminal of switching transistor M1 is connected to the output terminal of the mirror module 112; the first terminal of switching transistor M2 is connected to the second output terminal of the current output module 111; the second terminal of switching transistor M2 is connected to the first terminal of switching transistor M3; the second terminal of switching transistor M3 is connected to the first power supply terminal VSS; the control terminal of switching transistor M3 is used to receive the conduction voltage U1.

[0036] The conduction voltage U1 can be provided by an external circuit or by the constant current drive circuit, and is used to turn on the switching transistor M3.

[0037] The drive current Iout is the current in the conductive path between the mirror module 112 and the switching transistor M1. It can be understood that the third output terminal of the current output module 111 is used to provide a constant current. The switching transistor M1 is connected to both this third output terminal and the output terminal of the mirror module 112. When the drive voltage at the output terminal fluctuates, since the current of the switching transistor M1 remains constant, the gate-source voltage of the switching transistor M1 also remains constant. Furthermore, since the source voltage of the switching transistor M1 is equal to the drive voltage, fluctuations in the drive voltage will affect the gate voltage V of the switching transistor M1. FB Fluctuations will also occur, affecting the gate voltage of switch M2. Since the gate-source voltage of switch M2 changes very little, the source voltage of switch M2, which is also the drain voltage Vds of switch M3, will also change, ultimately altering the current flowing through switch M3, i.e., the second current.

[0038] Specifically, since the current flowing through the switching transistor M1 remains constant, when the drive voltage VDS_DRV at the output of the mirror module 112 increases, the gate voltage V of the switching transistor M1... FBThe voltage will also increase. Since the gate-source voltage of switch M2 remains unchanged, the drain voltage Vds of switch M3 will increase, thus increasing the second current and decreasing the first current. Therefore, the drive current output after replicating the first current will also decrease. Similarly, when the drive voltage VDS_DRV at the output of mirror module 112 decreases, the gate voltage Vds of switch M1 will also increase. FB As the voltage decreases, the drain voltage Vds of the switching transistor M3 also decreases, ultimately reducing the drive current. This suppresses the impact of drive voltage fluctuations on the drive current, ultimately achieving a constant drive current output. The measurement and adjustment module 113 has a simple structure, requires few components, and occupies a small area.

[0039] In one embodiment, such as Figure 4 As shown, the current output module 111 includes switching transistors M4, M5, M6, M7, M8, M9, and M10; the first terminals of switching transistors M4, M5, M6, and M7 are connected together and connected to the second power supply terminal VDD; the second terminal of switching transistor M7, the control terminal of switching transistor M7, the control terminal of switching transistor M8, the control terminal of switching transistor M9, and the control terminal of switching transistor M10 are connected together and connected to the first current source I1; the first terminal of switching transistor M4... The second terminal of switch M8 is connected to the first terminal of switch M4, the control terminals of switch M5 and M6 and the second terminal of switch M8 are connected together and connected to the second current source; the second terminal of switch M5 and the first terminal of switch M9 are connected together and serve as the second output terminal of current output module 111; the second terminal of switch M9 serves as the first output terminal of current output module 111; the first terminal of switch M10 is connected to the second terminal of switch M6 and the second terminal of switch M10 serves as the third output terminal of current output module 111.

[0040] It can be understood that switching transistors M5 and M6, together with switching transistor M4, form current mirrors to replicate the current flowing through switching transistor M4 and output a constant current. Switches M7, M8, M9, and M10 form a cascode current mirror to achieve accurate replication of the current of switching transistor M4 by switching transistors M5 and M6.

[0041] In one embodiment, such as Figure 5 As shown, the mirror module 112 includes a switching transistor M11 and a switching transistor M12. The first end and the control end of the switching transistor M11 are connected together with the control end of the switching transistor M12 and are connected to the first output end of the current output module 111. The second end of the switching transistor M11 and the second end of the switching transistor M12 are connected together and are connected to the first power supply terminal VSS. The first end of the switching transistor M12 serves as the output end of the mirror module 112.

[0042] It can be understood that switching transistors M11 and M12 form a pair of current mirrors, and switching transistor M12 can replicate the current flowing through switching transistor M11, which is the first current. The circuit structure of this mirror module 112 is simple and the chip occupies a small area.

[0043] In one embodiment, such as Figure 6 As shown, the control terminal of switch M3 is also connected to the control terminal of switch M11 to obtain the voltage at the control terminal of switch M11 as the turn-on voltage.

[0044] It is understandable that the control terminal of the switching transistor M3 can be connected to the control terminal of the switching transistor M11, so that the voltage of the control terminal of the switching transistor M11 can drive the switching transistor M3. There is no need to set an additional power supply to provide the turn-on voltage, which not only ensures the normal operation of the circuit, but also simplifies the circuit structure and makes it more practical.

[0045] In one embodiment, switching transistors M1, M2, and M3 can be N-type MOS transistors.

[0046] In one embodiment, switching transistors M4, M5, M6, M7, M8, M9, and M10 may be P-type MOSFETs.

[0047] In one embodiment, switching transistors M11 and M12 can be N-type MOS transistors.

[0048] Figure 7 This application provides another embodiment of a constant current drive circuit, which includes a current output module, a mirror module, and a measurement and adjustment module. The measurement and adjustment module includes switching transistors M1, M2, and M3; the current output module includes switching transistors M4, M5, M6, M7, M8, M9, and M10; and the mirror module includes switching transistors M11 and M12. The connection relationships and operating principles between the components can be found in the above embodiments. Figure 6 This will not be elaborated upon here.

[0049] The constant current drive circuit in this embodiment utilizes switching transistors M1, M2, and M3 to achieve feedback regulation of the drive current, realizing a stable output of the drive current. A comparison of the drive current with that without feedback regulation can be found by referring to [reference needed]. Figure 8 As shown; where L1 is the curve of drive current versus VDS_DRV with feedback regulation, and L2 is the curve of drive current versus VDS_DRV without feedback regulation. Figure 8 It can be seen that when there is feedback regulation, the change of VDS_DRV voltage has almost no effect on the drive current, and a stable output of drive current can be achieved.

[0050] The constant current drive circuit in this embodiment has a simple structure, low cost, and high constant current output accuracy. It still achieves a relatively ideal constant current drive output effect while greatly simplifying the circuit design, making it cost-effective.

[0051] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A constant current drive circuit, characterized in that, include: A current output module, wherein the first output terminal of the current output module is used to output a first current, and the second output terminal of the current output module is used to output a second current; The sum of the values ​​of the first current and the second current is constant; A mirror module, wherein the input terminal of the mirror module is connected to the first output terminal of the current output module, the mirror module is used to replicate the first current and output a drive current through the output terminal of the mirror module; The measurement and adjustment module is connected to the second output terminal of the current output module and the output terminal of the mirror module, respectively, and is used to measure the driving voltage of the mirror module. If the driving voltage changes, the second current is adjusted; wherein the adjustment direction of the second current is the same as the change direction of the driving voltage. The third output terminal of the current output module is used to output a constant current; the measurement and adjustment module includes switching transistors M1, M2, and M3. The control terminal and first terminal of switching transistor M1 are connected to the control terminal of switching transistor M2 and are connected to the third output terminal of the current output module; the second terminal of switching transistor M1 is connected to the output terminal of the mirror module; the first terminal of switching transistor M2 is connected to the second output terminal of the current output module; the second terminal of switching transistor M2 is connected to the first terminal of switching transistor M3; the second terminal of switching transistor M3 is connected to the first power supply terminal; the control terminal of switching transistor M3 is used to receive the conduction voltage.

2. The constant current drive circuit according to claim 1, characterized in that, The current output module includes switching transistors M4, M5, M6, M7, M8, M9 and M10. The first ends of switching transistors M4, M5, M6, and M7 are connected together and connected to a second power supply terminal. The second end of switching transistor M7, the control terminal of switching transistor M7, the control terminal of switching transistor M8, the control terminal of switching transistor M9, and the control terminal of switching transistor M10 are connected together and connected to a first current source. The second end of switching transistor M4 is connected to the first end of switching transistor M8. The control terminals of switching transistors M4, M5, M6, and M8 are connected together and connected to a second current source. The second end of switching transistor M5 and the first end of switching transistor M9 are connected together and serve as the second output terminal of the current output module. The second end of switching transistor M9 serves as the first output terminal of the current output module. The first end of switching transistor M10 is connected to the second end of switching transistor M6 and serves as the third output terminal of the current output module.

3. The constant current drive circuit according to claim 1, characterized in that, The mirror module includes a switching transistor M11 and a switching transistor M12. The first end and the control end of the switching transistor M11 are connected together with the control end of the switching transistor M12 and are connected to the first output end of the current output module. The second end of the switching transistor M11 and the second end of the switching transistor M12 are connected together and are connected to the first power supply end. The first end of the switching transistor M12 serves as the output end of the mirror module.

4. The constant current drive circuit according to claim 3, characterized in that, The control terminal of the switching transistor M3 is also connected to the control terminal of the switching transistor M11, for obtaining the voltage of the control terminal of the switching transistor M11 as the turn-on voltage.

5. The constant current drive circuit according to claim 1, characterized in that, The switching transistors M1, M2, and M3 are N-type MOS transistors.

6. The constant current drive circuit according to claim 1, characterized in that, The switching transistors M4, M5, M6, M7, M8, M9, and M10 are P-type MOS transistors.

7. The constant current drive circuit according to claim 3, characterized in that, The switching transistors M11 and M12 are N-type MOS transistors.

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