High-precision current copying circuit

Abstract

The invention relates to a high-precision current copying circuit, and aims to solve the problem of current mirror copying precision caused by a channel modulation effect in a large-proportion current mirror copying process. The circuit comprises a current mirror copy tube, a negative feedback module and an adjusting tube. The grid voltage of the current mirror copying tube is externally input, and the negative feedback module is used for controlling the grid control voltage of the adjusting tube, so that the voltages at the Vsens end and the VBAT end in the circuit are kept the same, and the current copying precision is improved. And the negative feedback module samples and compares the voltages at the VBAT end and the VSENS end to generate a control signal to adjust the grid voltage of the adjusting tube, so that the drain-source voltage of the current mirror copy tube is controlled. In addition, the circuit also comprises a voltage stabilizing structure which is used for preventing the influence of power supply voltage fluctuation on the control node. The test result shows that the circuit can realize high-precision current copying when the current mirror proportion is 1: 1000, and the voltage at the VBAT end and the VSENS end is approximately the same in the change process, so that the circuit is suitable for application occasions with higher requirements on the current copying precision.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a high-precision current replication circuit. Background Art

[0002] Traditional current mirror circuits are mostly based on simple current mirror structures using bipolar junction transistors (BJTs) or field-effect transistors (MOSFETs). Their basic operating principle is to leverage the characteristics of transistors to replicate a reference current at the input to the output at a specific ratio. However, this simple current mirror structure has many limitations in practical applications.

[0003] When the current replication ratio increases, the channel modulation effect of the transistor becomes more pronounced, leading to replication errors. Taking a MOSFET as an example, during operation, when the drain current increases, the electric field between the drain and source increases, shortening the effective length of the channel on the drain side, thereby causing the channel modulation effect. This effect causes the actual transconductance of the transistor to change, deviating from the ideal value, making it impossible for the replicated current to accurately follow the reference current at the expected ratio, resulting in a large replication error. This error can significantly affect the performance and measurement accuracy of the entire system, severely limiting the application range of traditional current replication circuits.

[0004] In addition, the characteristic parameters of transistors are discrete and temperature-sensitive. These factors will further aggravate the deviation between the copied current and the reference current, making it difficult for traditional current replication circuits to meet the requirements of modern electronic systems for high-precision current replication in terms of accuracy and stability.

[0005] To improve the accuracy of current replication, several improvements have emerged in the prior art. One common approach involves clamping the circuit's two terminals using an error amplifier. This error amplifier monitors the voltage or current difference between the two terminals in real time and generates a corresponding control signal based on this difference. This adjusts the replicated current to keep it as close to the reference current as possible, thus improving the accuracy of current replication to a certain extent.

[0006] However, this approach of introducing an error amplifier also presents numerous problems. First, the additional op amp increases circuit complexity. Circuit design requires designing appropriate bias circuits, stabilization networks, and input / output interface circuits for the error amplifier. This increases the number of components in the overall circuit, complicates layout and routing, and increases the difficulty of circuit debugging and optimization. Second, the introduction of an op amp can negatively impact circuit performance. For example, op amps inherently have limited gain-bandwidth product, input offset voltage, and noise, all of which can interfere with the accuracy and stability of current replication, especially in high-frequency or high-precision applications. Furthermore, the additional op amp increases circuit power consumption, which is extremely disadvantageous for power-sensitive portable devices or battery-powered systems, limiting the application of this solution in these areas.

[0007] With the rapid development of electronic technology, the demand for high-precision current replication circuits is becoming increasingly urgent. This is especially true in emerging high-tech fields, such as biomedical electronic devices (e.g., implantable medical devices, biosensors, etc.), which place extremely high demands on the accuracy of current signals. Minor current errors can significantly degrade device performance or even cause functional failure. In high-precision analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), precise current replication is crucial to ensuring the accuracy and resolution of signal conversion. In advanced communication systems, high-precision current replication circuits are also widely used in signal modulation and power amplification to ensure signal transmission quality and system reliability.

[0008] Given the limitations of traditional current replication circuits and existing improvement schemes in terms of accuracy and performance, a new type of high-precision current replication circuit has been developed that can achieve high-precision and high-stability current replication under various working conditions while having low power consumption and cost. This has extremely important practical significance for promoting the development of electronic technology and meeting the needs of many high-precision application fields. Summary of the Invention

[0009] The main purpose of the present invention is to provide a high-precision current replication circuit to solve the current mirror replication accuracy problem caused by the different drain-source voltage differences of transistors due to the channel modulation effect during the large-scale current mirror replication process.

[0010] To achieve the above object, the present invention proposes a high-precision current replication circuit, which clamps the drain-source voltage of the circuit through negative feedback, thereby improving the current replication accuracy of the circuit.

[0011] The overall system structure proposed by the present invention is as follows Figure 1 As shown in the figure, the circuit consists of three parts: current mirror replica tube, negative feedback module and adjustment tube. The specific circuit of the negative feedback module is Figure 2 Given, the overall circuit details are given by Figure 3 given.

[0012] The working process of the overall circuit is as follows: the gate voltage VCTRL of the current mirror replica tube is input from the outside. Under the operation of the negative feedback module circuit, the gate control voltage CTRL of the Mc adjustment tube is controlled to make the voltages at both ends of Vsens and VBAT the same, thereby improving the current replication accuracy.

[0013] The theoretical guidance of the present invention is as follows:

[0014]

[0015] Formula [1] is the current formula of the MOSFET in the saturation region, where λ is the channel length modulation factor; Formula [2] is the general current expression of the MOSFET. From the formula, it can be seen that when the Vgs of the circuit is the same, assuming the device parameters are the same, the current flowing through the transistor depends on whether the drain-source voltage Vds of the transistor is the same. Therefore, if the Vds of the current mirror circuit can be controlled so that the Vds of the two are the same, the current consistency can be approximately guaranteed.

[0016] The working principle of the submodule circuit of the present invention is as follows:

[0017] like Figure 2 The negative feedback circuit differs from the typical op amp design. It uses a current op amp and comparison circuit for circuit regulation. The main structure of the negative feedback circuit consists of MN0-MN3, MP1-MP3, and R1-R3. MN0 and MN1 form a basic current mirror circuit. MP1 and MP2 sample the voltages across VBAT and VSENS, generating two comparison currents, I1 and I2. MP1 and MP3, and MN2 and MN3, form two current mirrors to compare the sampled currents, generating the gate voltage of the adjustment transistor at node CTRL. By controlling the adjustment transistor, negative feedback is used to align the voltages across VBAT and VSENS. MP4-MP6 are three diode-connected MOS transistors, and MP7 forms a MOS capacitor structure. This stabilizes the CTRL node, preventing the node voltage from being immediately affected by power supply voltage fluctuations, thus protecting subsequent circuits.

[0018] Figure 3The overall circuit structure for high-precision current replication is demonstrated. The following analyzes the circuit's operation in detail when the VBAT voltage fluctuates. When the Vbat voltage fluctuates and exceeds the VSENS voltage, the gate voltages of MP1 and MP2 remain approximately unchanged, while the source voltage of MP1 increases. This increases MP1's Vgs, increasing the current I1 flowing through it. Similarly, the current flowing through MP3 increases, while the current flowing through MN3 remains unchanged. At this point, the voltage at the output terminal CTRL is pulled higher. At the same time, when the CTRL voltage increases, the vgs of the MOS tube M_c becomes smaller, which makes I_c smaller and Vsens larger, until the voltages at both ends of Vsens and Vbat are equal; when the voltage at the Vbat end fluctuates and is less than the VSENS voltage, the gate voltages of MP1 and MP2 are approximately unchanged, and the source voltage of MP1 rises and falls. For MP1, its Vgs becomes smaller, and the current I1 flowing through MP1 decreases. Similarly, the current flowing through MP3 becomes smaller, and the current flowing through MN3 remains unchanged. At this time, the output terminal CTRL voltage will be pulled down. At the same time, when the CTRL voltage decreases, the vgs of the MOS tube M_c becomes larger, which makes I_c larger and Vsens smaller, until the voltages at both ends of Vsens and Vbat are equal.

[0019] From the above analysis, it can be seen that in the present invention, the drain-source voltage at both ends of the current mirror replica tube is controlled by a negative feedback circuit to make the two equal, thereby further controlling the replication accuracy of the current mirror.

[0020] Figure 5 and Figure 6 What is shown is a common current replication circuit. Figure 6 For example, by ensuring that the Vgs voltage of the circuit MOSFET is the same, its current can be copied. However, in this case, as mentioned above, the channel length modulation effect caused by the Vds change is ignored, and the accuracy of current copying will be greatly reduced. Figure 5 The figure shows another current replica circuit. By adding an error amplifier (EA), a negative feedback structure is formed in the circuit. The virtual short characteristic of the amplifier under deep negative feedback conditions is used to make the two drain terminals of the current mirror MOS the same, thereby improving the current replication accuracy. Figure 5 The circuit shown in the figure has the same starting point as this article, both of which use the same Vds to control the current mirror MOS. Figure 5 The circuit shown in the figure requires design of loop stability and the error amplifier itself due to the addition of an additional error amplifier, which greatly increases the complexity of the design process. At the same time, the additional modules will further increase the circuit area and increase the cost of the chip.

[0021] The test circuit of the present invention is as follows Figure 4As shown in FIG, the ratio of the current mirror is set to 1:1000. By applying a varying voltage to the gate Vctrl control terminal of the current mirror, the two currents I_c and I_p, as well as the VBAT and VSENS voltages are measured respectively. Figure 7 and Figure 8 The test results are shown separately. The results show that when the I_P current changes from 49.4mA to 497mA, the copied current I_c can change from 49.4uA to 497uA. At the same time, the voltages at the VBAT and VSENS terminals remain approximately the same during the change, which is consistent with expectations.

[0022] In summary, the present invention has the following advantages: 1. The circuit utilizes negative feedback combined with a MOS capacitor voltage stabilization structure to effectively suppress the influence of power supply voltage fluctuations on the circuit and ensure the stability of current replication. No error amplifier is required, thus avoiding the loop stability problem caused by it and making the system more stable; 2. High-precision current replication, the negative feedback mechanism controls the drain-source voltage of the current mirror replica tube in real time to make them the same, thus overcoming the accuracy problem caused by the channel modulation effect. Tests show that high-precision replication can still be maintained when the current ratio reaches 1:1000. 3. No complex error amplifier and compensation circuit are required, the design is simplified, the chip area and cost are reduced, the resource utilization rate is high, and large-scale applications have more cost advantages; 4. Fast response capability, the circuit can quickly respond to changes in the VBAT terminal voltage, and timely adjust the drain-source voltage of the current mirror replica tube to ensure that the voltages at both ends of Vsens and VBAT quickly return to balance, ensuring that the current replication accuracy is not affected, and the performance is more reliable in dynamic environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. The present invention is further explained below in conjunction with the drawings and embodiments.

[0024] Figure 1 It is the overall structure of the present invention;

[0025] Figure 2 is the specific structure of the negative feedback module;

[0026] Figure 3 The specific structure of the overall current replication circuit;

[0027] Figure 4 This is a test circuit diagram;

[0028] Figure 5 This is a schematic diagram of an existing current replication circuit;

[0029] Figure 6 This is a schematic diagram of a conventional current replication circuit;

[0030] Figure 7 This is the simulation diagram of the test circuit current replication result;

[0031] Figure 8 VBAT and VSENS terminal voltage clamp simulation diagram DETAILED DESCRIPTION

[0032] [Example 1]

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present disclosure.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal manner unless otherwise explicitly defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together either directly or through one or more intermediate components.

[0035] In all embodiments of the present disclosure, since the source and drain of a metal oxide semiconductor (MOS) transistor are symmetrical, and the directions of the conduction current between the source and drain of an N-type transistor and a P-type transistor are opposite, in the embodiments of the present disclosure, the controlled middle terminal of the MOS transistor is referred to as the control terminal, and the remaining two terminals of the MOS transistor are referred to as the first terminal and the second terminal, respectively. In addition, terms such as "first" and "second" are only used to distinguish one component (or a portion of a component) from another component (or another portion of a component).

[0036] The specific implementation of the high-precision current replication circuit of the present invention will be further described in detail below with reference to the accompanying drawings. Figure 1 The overall system structure of the high-precision current replication circuit proposed by the present invention is shown. Figure 2 For the specific circuit of the negative feedback module, Figure 3 The detailed diagram of the overall circuit is shown below. Figure 4 To test the circuit, Figure 5 and Figure 6 This is a common current replication circuit.

[0037] The high-precision current replication circuit of the present invention primarily consists of a current mirror replica tube, a negative feedback module, and a regulator tube. The gate voltage VCTRL of the current mirror replica tube is externally supplied. The negative feedback module controls the gate control voltage CTRL of the regulator tube, ensuring that the voltages at Vsens and VBAT are the same, thereby improving current replication accuracy.

[0038] The specific circuit of the negative feedback module is as follows Figure 2 As shown, its main structure consists of M0-MN3, MP1-MP3, and R1-R3. MN0 and MN1 form a basic current mirror circuit; MP1 and MP2 sample the voltages across VBAT and VSENS, generating two comparison currents, I1 and I2. MP1 and MP3, and MN2 and MN3 form two sets of current mirrors, comparing the sampled currents and generating the gate voltage of the adjustment transistor at node CTRL. By controlling the adjustment transistor, negative feedback can be used to align the voltages across VBAT and VSENS. Furthermore, MP4-MP6 are diode-connected MOS transistors. Together with MP7, they form a MOS capacitor structure that stabilizes the CTRL node, preventing it from being affected by power supply voltage fluctuations and thus protecting subsequent circuits.

[0039] Figure 3 The overall circuit structure of high-precision current replication is shown. Taking the VBAT voltage fluctuation as an example, the circuit operation details are analyzed as follows:

[0040] When the voltage at Vbat fluctuates and exceeds the voltage at VSENS, the gate voltages of MP1 and MP2 remain approximately unchanged, but the source voltage of MP1 increases, causing Vgs of MP1 to increase and the current I1 flowing through MP1 to increase. Similarly, the current flowing through MP3 also increases, while the current flowing through MN3 remains unchanged. At this time, the voltage at the output terminal CTRL is pulled up. As the CTRL voltage increases, the Vgs of the MOS transistor M_c decreases, causing I_c to decrease and Vsens to increase, until Vsens and the voltage at Vbat are equal.

[0041] Conversely, when the Vbat voltage fluctuates and becomes less than the VSENS voltage, the gate voltages of MP1 and MP2 remain approximately unchanged, MP1's source voltage decreases, MP1's Vgs decreases, the current I1 flowing through MP1 decreases, and the current in MP3 also decreases, while the current in MN3 remains unchanged. At this time, the output CTRL voltage is pulled down. When the CTRL voltage decreases, Mc's Vgs increases, Ic increases, and Vsens decreases until Vsens and the voltage across Vbat are equal.

[0042] Through the above-mentioned negative feedback regulation mechanism, the circuit of the present invention can ensure that the drain-source voltages at both ends of the current mirror replica tube are the same, thereby effectively controlling the replication accuracy of the current mirror and solving the accuracy problem caused by the channel modulation effect during the large-scale current mirror replication process.

[0043] The test circuit of the present invention is as follows Figure 4 As shown in the figure, the current mirror ratio is set to 1:1000. During the test, the two currents I_c and I_p, as well as the VBAT and VSENS voltages, were measured by varying the input Vctrl voltage. The test results show that when the I_P current changes from 49.4mA to 497mA, the replicated current I_c can also change from 49.4uA to 497uA. The voltages at the VBAT and VSENS terminals remain approximately the same during this change, consistent with the intended design and verifying the high-precision current replication performance of the circuit of the present invention.

[0044] In summary, the high-precision current replication circuit of the present invention realizes high-precision replication of current in a large-scale current mirror replication process through reasonable circuit design, combined with negative feedback regulation and voltage stabilization protection measures. It has good stability and reliability and can be used in various application scenarios with high requirements for current replication accuracy.

[0045] Advantages of the present invention include:

[0046] 1. The circuit uses negative feedback combined with a MOS capacitor voltage stabilization structure to effectively suppress the impact of power supply voltage fluctuations on the circuit and ensure the stability of current replication. It does not require an error amplifier, avoiding the loop stability issues it brings, and the system is more stable.

[0047] 2. High-precision current replication: A negative feedback mechanism controls the drain-source voltage of the current mirror replicator in real time, ensuring that it is equal, overcoming the accuracy issues caused by the channel modulation effect. Tests have shown that high-precision replication can be maintained even at a current ratio of 1:1000.

[0048] 3. No need for complex error amplifiers and compensation circuits, simplified design, reduced chip area and cost, high resource utilization, and more cost-effective for large-scale applications;

[0049] 4. Fast response capability. The circuit can quickly respond to changes in the VBAT terminal voltage and adjust the drain-source voltage of the current mirror replica tube in time to ensure that the voltages at both ends of Vsens and VBAT quickly return to balance, ensuring that the current replication accuracy is not affected and the performance is more reliable in dynamic environments.

[0050] It should also be noted that the terms "include," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the product or system comprising the element. "Substantially" means that within an acceptable error range, a person skilled in the art can solve the technical problem within a certain error range and substantially achieve the technical effect.

[0051] Unless the context clearly indicates otherwise, as used herein and in the appended claims, the singular includes the plural, and vice versa. Thus, when referring to the singular, the plural of the corresponding term is generally included. Similarly, the words "include" and "comprising" are to be interpreted as inclusive rather than exclusive. Likewise, the terms "include" and "or" should be interpreted as inclusive unless such interpretation is expressly prohibited herein. Where the term "example" is used herein, particularly when it follows a group of terms, the "example" is merely exemplary and illustrative and should not be considered exclusive or comprehensive.

Claims

1. A high-precision current replication circuit, characterized in that: The system includes a current mirror replica tube, a negative feedback module, and an adjustment tube. The gate voltage of the current mirror replica tube is input from the outside. The negative feedback module is used to control the gate control voltage of the adjustment tube so that the voltages at both ends of Vsens and VBAT in the circuit are the same, thereby improving the current replication accuracy.

2. The high-precision current replication circuit according to claim 1, characterized in that: The negative feedback module includes MN0-MN3, MP1-MP3 and R1-R3, wherein MN0 and MN1 constitute a basic current mirror circuit, MP1 and MP2 are used to sample the voltages at both ends of VBAT and VSENS and generate two comparison currents I1 and I2, MP1 and MP3, MN2 and MN3 constitute two groups of current mirrors to compare the sampled currents and generate the gate control voltage of the adjustment tube at the node CTRL.

3. The high-precision current replication circuit according to claim 2, characterized in that: It also includes three diode-connected MOSs MP4-MP6 and a MOS capacitor structure composed of MP7, which are used to stabilize the ctrl node and prevent the influence of power supply voltage fluctuations on the circuit.

4. The high-precision current replication circuit according to claim 1, wherein: When the voltage fluctuation at the VBAT terminal is greater than the VSENS voltage, the source voltage of MP1 increases, the current flowing through MP1 and MP3 increases, the voltage at the output terminal CTRL is pulled up, and the vgs of the adjustment tube Mc decreases, causing Ic to decrease and Vsens to increase until the voltages at both ends of Vsens and Vbat are equal.

5. The high-precision current replication circuit according to claim 1, characterized in that: When the voltage fluctuation at the VBAT terminal is less than the VSENS voltage, the source voltage of MP1 decreases, the current flowing through MP1 and MP3 decreases, the voltage at the output terminal CTRL is pulled down, the VGS of the adjustment tube Mc increases, which increases Ic and reduces Vsens until the voltages at both ends of Vsens and Vbat are equal.

6. The high-precision current replication circuit according to claim 1, characterized in that: During the circuit test, the current mirror ratio is set to 1:1000. By changing the input Vctrl voltage, the copied current I_c can be proportionally changed with the primary current I_P, and the voltages at the VBAT and VSENS terminals are approximately the same during the change process.

7. The high-precision current replication circuit according to any one of claims 1 to 6, characterized in that: The circuit is applied to electronic equipment or systems requiring high current replication accuracy.

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