Constant current source circuit and electronic equipment

Abstract

The present application is applicable to the technical field of constant current source circuit, and provides a constant current source circuit and electronic device. The constant current source circuit includes a first operational amplifier module, a current mirror module, a resistor module, a switch module and a second operational amplifier module, the first operational amplifier module is electrically connected to the current mirror module and the resistor module respectively, the switch module is connected between the current mirror module and the resistor module, and the second operational amplifier module is electrically connected to the current mirror module and the switch module respectively. The constant current source circuit provided in the embodiment of the present application adopts a first feedback loop and a second feedback loop, firstly adjusts the resistor module to ensure that the temperature coefficient of the second current output by the constant current source circuit is zero, thereby avoiding the influence of temperature change on the output accuracy of the constant current source circuit, and then adjusts the second current output by the constant current source circuit at room temperature, thereby eliminating the mirror error, and further improving the output accuracy of the constant current source circuit.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic equipment, and in particular, relates to a constant current source circuit and electronic equipment. Background Art

[0002] As a key technology in analog circuits, constant current source circuits are widely used in fields such as resistance detection and LED driving. The accuracy of their output current directly affects the accuracy of resistance detection and the brightness and efficiency of LED lamps. The output of the constant current source circuit usually generates a reference current from a voltage-current conversion circuit, and is mirrored through an amplification ratio to obtain the required constant current. Among them, voltage, resistance, and amplification ratio all have an important influence on the accuracy of the constant current source circuit. At the same time, in practical applications, due to the limitations of semiconductor processes and temperature changes, there will be errors in both resistance and mirror ratio, resulting in low output accuracy of the constant current source circuit. Summary of the invention

[0003] The embodiments of the present application provide a constant current source circuit and an electronic device, which can solve the problem that in practical applications, due to the limitations of semiconductor processes and temperature changes, errors in resistance and mirror ratios occur in existing constant current source circuits, resulting in low output accuracy of the constant current source circuit.

[0004] In a first aspect, an embodiment of the present application provides a constant current source circuit, including a first operational amplifier module, a current mirror module, a resistor module, a switch module, and a second operational amplifier module, wherein the first operational amplifier module is electrically connected to the current mirror module and the resistor module, respectively, the switch module is connected between the current mirror module and the resistor module, the second operational amplifier module is electrically connected to the current mirror module and the switch module, respectively, the current mirror module is used to be electrically connected to a load, and the temperature coefficient of the resistor module is zero;

[0005] When the switch module is in the on state, the resistor module is used to output a feedback voltage, and the feedback voltage is equal to the product of the resistance value of the resistor module and the first current flowing through the resistor module; the first operational amplifier module is used to output a first voltage signal to the current mirror module according to the feedback voltage and the reference voltage; the current mirror module is used to output a second current according to the first voltage signal and the first current; the second operational amplifier module is used to output a second voltage signal to the switch module according to a node voltage and an output voltage, the node voltage is the voltage of the common end of the current mirror module and the switch module, and the output voltage is equal to the product of the second current and the resistance value of the load.

[0006] In a possible implementation of the first aspect, the first operational amplifier module includes a first operational amplifier, a first input terminal of the first operational amplifier is used to receive the reference voltage, a second input terminal of the first operational amplifier is electrically connected to the resistance module, and an output terminal of the first operational amplifier is electrically connected to the current mirror module.

[0007] In a possible implementation of the first aspect, the current mirror module includes a first switch tube and a second switch tube, the gate of the first switch tube is electrically connected to the gate of the second switch tube and the first operational amplifier module, respectively, the source of the first switch tube is electrically connected to the source of the second switch tube, and is used to be electrically connected to a first power supply, the drain of the first switch tube is electrically connected to the switch module and the second operational amplifier module, respectively, and the drain of the second switch tube serves as the output end of the constant current source circuit, and is electrically connected to the second operational amplifier module and the load, respectively.

[0008] In a possible implementation manner of the first aspect, the resistance module includes a first resistance unit and a second resistance unit, the second resistance unit is connected in series between the first resistance unit and the switch module, the second resistance unit is also electrically connected to the first operational amplifier module, and the first resistance unit is grounded;

[0009] The temperature coefficient of the first resistance unit is opposite to the temperature coefficient of the second resistance unit.

[0010] In a possible implementation manner of the first aspect, the first resistance unit includes a first resistor, a first end of the first resistor is electrically connected to the second resistance unit, and a second end of the first resistor is grounded.

[0011] In a possible implementation manner of the first aspect, the second resistance unit includes N second resistors and N first switches, the N second resistors are connected in series in sequence, the second end of the first second resistor is electrically connected to the first resistance unit, the first end of the Nth second resistor is electrically connected to the switch module, the second resistors and the first switches correspond one-to-one, the first end of each second resistor is electrically connected to the first end of the corresponding first switch, the second ends of all the first switches are electrically connected to each other and to the first operational amplifier module, and the control ends of all the first switches are used to receive a first control signal, wherein N is an integer greater than or equal to 1.

[0012] In a possible implementation of the first aspect, the switch module includes a third switch tube, a gate of the third switch tube is electrically connected to the second operational amplifier module, a source of the third switch tube is electrically connected to the current mirror module and the second operational amplifier module respectively, and a drain of the third switch tube is electrically connected to the resistance module.

[0013] In a possible implementation of the first aspect, the second operational amplifier module includes a second operational amplifier, a first input end of the second operational amplifier is electrically connected to the current mirror module and the switch module, respectively, a second input end of the second operational amplifier is electrically connected to the current mirror module and the load, respectively, and an output end of the second operational amplifier is electrically connected to the switch module.

[0014] In a possible implementation manner of the first aspect, the constant current source circuit further includes a reference selection module, the reference selection module is electrically connected to the first operational amplifier module, and the reference selection module is used to output a corresponding reference voltage according to a second control signal.

[0015] In a second aspect, an embodiment of the present application provides an electronic device, comprising the constant current source circuit described in any one of the first aspects.

[0016] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0017] The constant current source circuit provided by the embodiment of the present application includes a first operational amplifier module, a current mirror module, a resistor module, a switch module and a second operational amplifier module. When the switch module is in the on state, the resistor module can output a feedback voltage, and the feedback voltage is equal to the product of the resistance value of the resistor module and the first current flowing through the resistor module. At this time, since the switch module is in the on state, the first current is the current input to the current mirror module. The first operational amplifier module is used to receive the feedback voltage and the reference voltage, and output the first voltage signal according to the feedback voltage and the reference voltage, so that the current mirror module outputs the second current according to the first voltage signal and the first current. Since the first operational amplifier module, the current mirror module, the resistor module and the switch module can constitute a first feedback loop, it is ensured that the feedback voltage is equal to the reference voltage. In addition, since the temperature coefficient of the resistor module is zero, the temperature coefficient of the first current is zero, thereby ensuring that the second current output by the current mirror module is stable and is not affected by temperature changes. The second operational amplifier module and the switch module jointly constitute a second feedback loop, thereby ensuring that the output voltage is equal to the node voltage, so that the mirror error caused by the mirror ratio of the current mirror module can be eliminated. It can be seen that the constant current source circuit provided in the embodiment of the present application adopts a first feedback loop and a second feedback loop. First, the resistance module is trimmed to ensure that the temperature coefficient of the second current output by the constant current source circuit is zero, thereby avoiding the influence of temperature changes on the output accuracy of the constant current source circuit. Then, the second current output by the constant current source circuit is trimmed at room temperature, thereby eliminating the mirror error and further improving the output accuracy of the constant current source circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 It is a principle block diagram of a constant current source circuit provided in one embodiment of the present application;

[0020] Figure 2 1 is a circuit connection diagram of a constant current source circuit provided in one embodiment of the present application;

[0021] Figure 3 is a principle block diagram of a constant current source circuit provided by another embodiment of the present application;

[0022] Figure 4 This is a second current-temperature characteristic curve provided in an embodiment of the present application.

[0023] In the figure, 10, constant current source circuit; 101, first operational amplifier module; 102, current mirror module; 103, resistance module; 1031, first resistance unit; 1032, second resistance unit; 104, switch module; 105, second operational amplifier module; 106, reference selection module; 20, load. DETAILED DESCRIPTION

[0024] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0025] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0026] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0027] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0028] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0029] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0030] As a key technology in analog circuits, constant current source circuits are widely used in fields such as resistance detection and LED driving. The accuracy of their output current directly affects the accuracy of resistance detection and the brightness and efficiency of LED lamps. The output of the constant current source circuit usually generates a reference current from a voltage-current conversion circuit, and is mirrored through an amplification ratio to obtain the required constant current. Among them, voltage, resistance, and amplification ratio all have an important influence on the accuracy of the constant current source circuit. At the same time, in practical applications, due to the limitations of semiconductor processes and temperature changes, there will be errors in both resistance and mirror ratio, resulting in low output accuracy of the constant current source circuit.

[0031] Based on the above problems, the constant current source circuit provided by the embodiment of the present application includes a first operational amplifier module, a current mirror module, a resistor module, a switch module and a second operational amplifier module. When the switch module is in the on state, the resistor module can output a feedback voltage, and the feedback voltage is equal to the product of the resistance value of the resistor module and the first current flowing through the resistor module. At this time, since the switch module is in the on state, the first current is the current input to the current mirror module. The first operational amplifier module is used to receive the feedback voltage and the reference voltage, and output the first voltage signal according to the feedback voltage and the reference voltage, so that the current mirror module outputs the second current according to the first voltage signal and the first current. Since the first operational amplifier module, the current mirror module, the resistor module and the switch module can constitute a first feedback loop, it is ensured that the feedback voltage is equal to the reference voltage. In addition, since the temperature coefficient of the resistor module is zero, the temperature coefficient of the first current is zero, thereby ensuring that the second current output by the current mirror module is stable and is not affected by temperature changes. The second operational amplifier module and the switch module jointly constitute a second feedback loop, thereby ensuring that the output voltage is equal to the node voltage, so that the mirror error caused by the mirror ratio of the current mirror module can be eliminated. It can be seen that the constant current source circuit provided in the embodiment of the present application adopts a first feedback loop and a second feedback loop. First, the resistance module is trimmed to ensure that the temperature coefficient of the second current output by the constant current source circuit is zero, thereby avoiding the influence of temperature changes on the output accuracy of the constant current source circuit. Then, the second current output by the constant current source circuit is trimmed at room temperature, thereby eliminating the mirror error and further improving the output accuracy of the constant current source circuit.

[0032] In order to illustrate the technical solution described in this application, a specific embodiment is provided below for illustration.

[0033] Figure 1 FIG. 1 shows a principle block diagram of a constant current source circuit 10 provided in an embodiment of the present application. Figure 1 As shown, the constant current source circuit 10 includes a first operational amplifier module 101, a current mirror module 102, a resistor module 103, a switch module 104 and a second operational amplifier module 105. The first operational amplifier module 101 is electrically connected to the current mirror module 102 and the resistor module 103, respectively. The switch module 104 is connected between the current mirror module 102 and the resistor module 103. The second operational amplifier module 105 is electrically connected to the current mirror module 102 and the switch module 104, respectively. The current mirror module 102 is used to be electrically connected to the load 20, and the temperature coefficient of the resistor module 103 is zero.

[0034] Specifically, when the switch module 104 is in the on state, the resistor module 103 can output a feedback voltage Vfb, and the feedback voltage Vfb is equal to the product of the resistance value of the resistor module 103 and the first current Iref flowing through the resistor module 103. At this time, since the switch module 104 is in the on state, the first current Iref is the current input to the current mirror module 102. The first operational amplifier module 101 is used to receive the feedback voltage Vfb and the reference voltage VREF, and output a first voltage signal according to the feedback voltage Vfb and the reference voltage VREF, so that the current mirror module 102 outputs the second current ICC according to the first voltage signal and the first current Iref. Since the first operational amplifier module 101, the current mirror module 102, the resistor module 103 and the switch module 104 can form a first feedback loop, it is ensured that the feedback voltage Vfb is equal to the reference voltage VREF. In addition, since the temperature coefficient of the resistor module 103 is zero, the temperature coefficient of the first current Iref is zero, thereby ensuring that the second current ICC output by the current mirror module 102 is stable and is not affected by temperature changes. The second operational amplifier module 105 and the switch module 104 together constitute a second feedback loop, thereby ensuring that the output voltage V2 is equal to the node voltage V1, so that the mirror error caused by the mirror ratio of the current mirror module 102 can be eliminated. It can be seen that the constant current source circuit 10 provided in the embodiment of the present application adopts the first feedback loop and the second feedback loop, firstly, the resistor module 103 is adjusted to ensure that the temperature coefficient of the second current ICC output by the constant current source circuit 10 is zero, thereby avoiding the influence of temperature changes on the output accuracy of the constant current source circuit 10, and then the second current ICC output by the constant current source circuit 10 is adjusted at room temperature, thereby eliminating the mirror error and further improving the output accuracy of the constant current source circuit 10.

[0035] It should be noted that the reference voltage VREF can be a reference voltage source provided by a bandgap reference circuit and has a small change with temperature. The reference voltage VREF can also be provided by other reference circuits or reference voltage VREF sources, which are not limited here. The first current Iref is equal to the feedback voltage Vfb divided by the resistance value of the resistor module 103. Since the feedback voltage Vfb is equal to the reference voltage VREF, the first current Iref is the reference voltage VREF divided by the resistance value of the resistor module 103. Since the value of the reference voltage VREF changes very little with temperature, it can be considered that the temperature coefficient of the reference voltage VREF is zero. Therefore, the value of the first current Iref changes very little with temperature, that is, it can be considered that the temperature coefficient of the first current Iref is zero, thereby ensuring that the second current ICC output by the current mirror module 102 is stable and not affected by temperature changes.

[0036] It should be noted that the constant current source circuit 10 includes two types of adjustments: first, the resistor module 103 is adjusted to ensure that the temperature coefficient of the second current ICC output by the constant current source circuit 10 is zero, and then the second current ICC output by the constant current source circuit 10 is adjusted again at room temperature. The two adjustment steps cannot be reversed.

[0037] In one embodiment of the present application, Figure 2 As shown, the first operational amplifier module 101 includes a first operational amplifier AMP1, a first input terminal of the first operational amplifier AMP1 is used to receive a reference voltage VREF, a second input terminal of the first operational amplifier AMP1 is electrically connected to the resistance module 103, and an output terminal of the first operational amplifier AMP1 is electrically connected to the current mirror module 102.

[0038] Specifically, the positive input terminal of the first operational amplifier AMP1 is used as the second input terminal of the first operational amplifier AMP1 to receive the feedback voltage Vfb output by the resistor module 103, and the negative input terminal of the first operational amplifier AMP1 is used as the first input terminal of the first operational amplifier AMP1 to receive the reference voltage VREF. The output terminal of the first operational amplifier AMP1 is connected to the current mirror module 102, which is used to output a first voltage signal to drive the current mirror module 102. When the switch module 104 is turned on, the current mirror module 102 and the resistor module 103 are connected, and the resistor module 103 can output the feedback voltage Vfb to the positive input terminal of the first operational amplifier AMP1. Thus, the first operational amplifier AMP1, the current mirror module 102, the switch module 104 and the resistor module 103 together constitute a first feedback loop. That is, the first voltage signal output by the first operational amplifier AMP1 will change with the change of the feedback voltage Vfb at the positive input terminal of the first operational amplifier AMP1.

[0039] It should be noted that the first feedback loop formed by the first operational amplifier AMP1, the current mirror module 102, the switch module 104 and the resistor module 103 may be a high-gain negative feedback loop. Therefore, when the system is stable, the feedback voltage Vfb is equal to the reference voltage VREF.

[0040] In one embodiment of the present application, Figure 2 As shown, the current mirror module 102 includes a first switch tube Q1 and a second switch tube Q2, the gate of the first switch tube Q1 is electrically connected to the gate of the second switch tube Q2 and the first operational amplifier module 101, the source of the first switch tube Q1 is electrically connected to the source of the second switch tube Q2, and is used to be electrically connected to the first power supply VBAT, the drain of the first switch tube Q1 is electrically connected to the switch module 104 and the second operational amplifier module 105, and the drain of the second switch tube Q2 serves as the output end of the constant current source circuit 10, and is electrically connected to the second operational amplifier module 105 and the load 20, respectively.

[0041] Specifically, the gate of the first switch tube Q1 is connected to the gate of the second switch tube Q2, and the source of the first switch tube Q1 is connected to the source of the second switch tube Q2, which indicates that the first switch tube Q1 and the second switch tube Q2 form a current mirror, and the mirror ratio between the first switch tube Q1 and the second switch tube Q2 can be set to 1:K. The gate of the first switch tube Q1 and the gate of the second switch tube Q2 are both used to receive the first voltage signal, and are turned on and off according to the first voltage signal. When the first voltage signal is a low-level signal, that is, when the feedback voltage Vfb is less than or equal to the reference voltage VREF, the first switch tube Q1 is turned on, and the current flowing through the first switch tube Q1 is the first current Iref. It can be seen that the current flowing through the second switch tube Q2 is K times the first current Iref, that is, the target current is K times the first current Iref.

[0042] It should be noted that the on-resistance of the first switch tube Q1 and the second switch tube Q2 can be changed by changing the sizes of the first switch tube Q1 and the second switch tube Q2, thereby changing the mirror ratio between the first switch tube Q1 and the second switch tube Q2, thereby widening the range of the second current ICC.

[0043] For example, the designer can select the type of the first switch tube Q1 and the second switch tube Q2 according to the actual situation, that is, a fully controlled power device such as a metal oxide field effect transistor or an insulated gate bipolar transistor can be used. For example, the first switch tube Q1 and the second switch tube Q2 can be selected as PMOS tubes.

[0044] In one embodiment of the present application, Figure 2 As shown, the resistance module 103 includes a first resistance unit 1031 and a second resistance unit 1032. The second resistance unit 1032 is connected in series between the first resistance unit 1031 and the switch module 104. The second resistance unit 1032 is also electrically connected to the first operational amplifier module 101. The first resistance unit 1031 is grounded.

[0045] Specifically, the sum of the resistance of the first resistance unit 1031 and the resistance of the second resistance unit 1032 is the resistance of the resistance module 103, and the resistance of the resistance module 103 is multiplied by the first current Iref to obtain the feedback voltage transmitted to the first operational amplifier module 101. At the same time, the temperature coefficient of the first resistance unit 1031 and the temperature coefficient of the second resistance unit 1032 are opposite, that is, if the temperature coefficient of the first resistance unit 1031 is positive, the temperature coefficient of the second resistance unit 1032 is negative, and if the temperature coefficient of the first resistance unit 1031 is negative, the temperature coefficient of the second resistance unit 1032 is positive. The temperature coefficients of the two resistance units are set opposite to each other, so as to ensure that the temperature coefficient of the resistance module 103 is zero.

[0046] In one embodiment of the present application, Figure 2 As shown, the first resistance unit 1031 includes a first resistor R1, a first end of the first resistor R1 is electrically connected to the second resistance unit 1032, and a second end of the first resistor R1 is grounded.

[0047] Specifically, the resistance of the first resistor R1 is the resistance of the first resistor unit 1031. The first resistor R1 is connected in series with the second resistor unit 1032. The current flowing through the first resistor R1 is the first current Iref. The voltage drop generated by the first current Iref flowing through the first resistor R1 is the product of the first current Iref and the resistance of the first resistor R1.

[0048] In one embodiment of the present application, Figure 2 As shown, the second resistance unit 1032 includes N second resistors and N first switches, the N second resistors are connected in series in sequence, the second end of the first second resistor is electrically connected to the first resistance unit 1031, the first end of the Nth second resistor is electrically connected to the switch module 104, the first end of each second resistor is electrically connected to the first end of the corresponding first switch, the second ends of all the first switches are electrically connected to each other and to the first operational amplifier module 101, and the control ends of all the first switches are used to receive the first control signal, wherein N is an integer greater than or equal to 1.

[0049] Specifically, Figure 2 R2_1, R2_2, ..., R2_N-1, R2_N in the figure are all second resistors, S1, ..., S N-1 , S N All are first switches. A decoder may be used to output a first control signal to a control terminal of the first switch to control the on and off of the first switch, thereby determining the number of second resistors working in series in the second resistor unit 1032, wherein the sum of the resistance values ​​of the second resistors working in series is the resistance value of the second resistor unit 1032. When all first switches are in the off state, all second resistors in the second resistor unit 1032 work in series, and the voltage drop generated by the first current Iref flowing through all second resistors is the product of the first current Iref and the sum of the resistance values ​​of all second resistors.

[0050] It should be noted that, during the design, the types of the first resistor R1 and the second resistor are different, and a combination of a positive temperature coefficient resistor and a negative temperature coefficient resistor can be selected to form a zero temperature coefficient resistor module 103. If the resistor that changes less with temperature is a negative temperature coefficient resistor, the negative temperature coefficient resistor is set at the low end and is set to the first resistor R1. The temperature coefficient of the resistor module 103 is adjusted by adjusting the positive temperature coefficient resistor so that the temperature coefficient of the resistor module 103 is zero. If the resistor that changes less with temperature is a positive temperature coefficient resistor, the positive temperature coefficient resistor is set at the low end and is set to the first resistor R1. The temperature coefficient of the resistor module 103 is adjusted by adjusting the negative temperature coefficient resistor so that the temperature coefficient of the resistor module 103 is zero. Designing the resistor module 103 in this way can reduce the impact of the reduction in voltage margin caused by adding the resistor module 103. In addition, the temperature coefficients of all second resistors are the same.

[0051] It should be noted that, since two different types of first resistors R1 and second resistors are used, it is not possible to ensure that the process consistency of the two types of resistors changes in the same direction, and sufficient positive and negative adjustment ranges need to be reserved. In addition, designers can reasonably design the adjusted fabric length according to actual needs or temperature accuracy requirements, which is not limited here.

[0052] It should be noted that the designer can adjust the number of the second resistors working in series by controlling the on and off of the first switch according to temperature requirements. If the temperature changes, the resistance value of the first resistor R1 changes. In order to ensure that the temperature coefficient of the resistor module 103 is zero, the number of the second resistors working in series can be adjusted by controlling the first switch.

[0053] For example, the negative temperature coefficient resistor may be a poly resistor, and the positive temperature coefficient resistor may be a diffusion resistor.

[0054] In one embodiment of the present application, Figure 2 As shown, the switch module 104 includes a third switch tube Q3, the gate of the third switch tube Q3 is electrically connected to the second operational amplifier module 105, the source of the third switch tube Q3 is electrically connected to the current mirror module 102 and the second operational amplifier module 105 respectively, and the drain of the third switch tube Q3 is electrically connected to the resistance module 103.

[0055] Specifically, the third switch tube Q3 is turned on and off according to the second voltage signal output by the second operational amplifier module 105. When the second voltage signal is a high level signal, the third switch tube Q3 is turned off, and when the second voltage signal is a low level signal, the third switch tube Q3 is turned on. When the second operational amplifier module 105 controls the third switch tube Q3 to be turned on, the current flowing through the third switch tube Q3 is the first current Iref.

[0056] For example, the designer can select the type of the third switch tube Q3 according to the actual situation, that is, a fully controlled power device such as a metal oxide field effect transistor or an insulated gate bipolar transistor can be used. For example, the third switch tube Q3 can be selected as a PMOS tube.

[0057] In one embodiment of the present application, Figure 2 As shown, the second operational amplifier module 105 includes a second operational amplifier AMP2, a first input terminal of the second operational amplifier AMP2 is electrically connected to the current mirror module 102 and the switch module 104 respectively, a second input terminal of the second operational amplifier AMP2 is electrically connected to the current mirror module 102 and the load 20, and an output terminal of the second operational amplifier AMP2 is electrically connected to the switch module 104.

[0058] Specifically, the positive input terminal of the second operational amplifier AMP2 serves as the second input terminal of the first operational amplifier AMP1, and is used to receive the output voltage V2. The negative input terminal of the second operational amplifier AMP2 serves as the first input terminal of the first operational amplifier AMP1, and is used to receive the node voltage V1. The output terminal of the second operational amplifier AMP2 is connected to the third switch tube Q3, and is used to output a second voltage signal to drive the third switch tube Q3. When the third switch tube Q3 is turned on, the negative input terminal of the second operational amplifier AMP2 is connected to the resistor module 103. Thus, the second operational amplifier AMP2 and the third switch tube Q3 together constitute a second feedback loop. That is, the second voltage signal output by the second operational amplifier AMP2 will change with the change of the node voltage V1 at the negative input terminal of the second operational amplifier AMP2.

[0059] It should be noted that the second feedback loop formed by the second operational amplifier AMP2 and the third switch tube Q3 can be a high-gain negative feedback loop. Therefore, when the system is stable, the output voltage V2 is equal to the node voltage V1, thereby eliminating the current mirror error caused by the channel length modulation effect of the first switch tube Q1 and the second switch tube Q2.

[0060] In one embodiment of the present application, Figure 3 As shown, the constant current source circuit 10 further includes a reference selection module 106 , which is electrically connected to the first operational amplifier module 101 , and is used to output a corresponding reference voltage VREF according to the second control signal.

[0061] Specifically, the reference selection module 106 has the function of selecting the reference voltage VREF, and can output the corresponding reference voltage VREF according to the second control signal, thereby avoiding the deviation of the resistance module 103 caused by the process deviation.

[0062] It should be noted that the selection reference module 106 may include a selection path composed of a decoder and a switch, and the specific adjustment range and adjustment compensation are determined according to parameters such as different processes and the accuracy requirements of the constant current source circuit 10 at room temperature.

[0063] It should be noted that in practical applications, other non-ideal factors are often encountered, such as inconsistent resistance process deviations of different types of resistors, deviations in temperature coefficients, etc. The existing constant current source circuit cannot correct the deviations caused by non-ideal factors, or can only correct one of the deviations, resulting in low output accuracy of the constant current source circuit 10. The constant current source circuit 10 in the present application can correct all deviations caused by non-ideal factors (such as process, temperature and mirror image), greatly improving the output accuracy of the constant current source circuit 10.

[0064] It should be noted that the temperature coefficient of the final output current of the constant current source circuit 10 will also be affected by the reference voltage VREF. When the reference voltage VREF takes an ideal value, the constant current source circuit 10 is configured to output a current of 100mA, and the resistor module 103 is reasonably designed, the target temperature characteristic curve of the zero temperature coefficient is as follows: Figure 4 If the temperature coefficient of the reference voltage VREF and Figure 4 If the temperature coefficient of the second current ICC is the same as that of the reference voltage VREF, the temperature coefficient of the second current ICC will deteriorate. Figure 4 If the reference voltage VREF has the opposite curvature (opening upward), the temperature coefficient of the second current ICC will be further optimized after using the actual reference voltage VREF. Therefore, the reference voltage VREF can be reasonably designed with the temperature variation trend and the resistance module 103 under different processes to obtain the constant current source circuit 10 that is less affected by the process and temperature.

[0065] The present application also discloses an electronic device, including the above-mentioned constant current source circuit 10. The above-mentioned constant current source circuit 10 can improve the output accuracy of the electronic device, thereby improving the working efficiency and reliability of the electronic device.

[0066] Since the processing and functions implemented by the electronic device in this embodiment basically correspond to the embodiments, principles and examples of the aforementioned constant current source circuit, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0067] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A constant current source circuit, characterized in that: It includes a first operational amplifier module, a current mirror module, a resistor module, a switch module and a second operational amplifier module, wherein the first operational amplifier module is electrically connected to the current mirror module and the resistor module respectively, the switch module is connected between the current mirror module and the resistor module, the second operational amplifier module is electrically connected to the current mirror module and the switch module respectively, the current mirror module is used to be electrically connected to a load, and the temperature coefficient of the resistor module is zero; When the switch module is in the on state, the resistor module is used to output a feedback voltage, and the feedback voltage is equal to the product of the resistance value of the resistor module and the first current flowing through the resistor module; the first operational amplifier module is used to output a first voltage signal to the current mirror module according to the feedback voltage and the reference voltage; the current mirror module is used to output a second current according to the first voltage signal and the first current; the second operational amplifier module is used to output a second voltage signal to the switch module according to the node voltage and the output voltage, the node voltage is the voltage of the common end of the current mirror module and the switch module, and the output voltage is equal to the product of the second current and the resistance value of the load; The first operational amplifier module includes a first operational amplifier, a first input terminal of the first operational amplifier is used to receive the reference voltage, a second input terminal of the first operational amplifier is electrically connected to the resistance module, and an output terminal of the first operational amplifier is electrically connected to the current mirror module; The resistance module includes a first resistance unit and a second resistance unit, the second resistance unit is connected in series between the first resistance unit and the switch module, the second resistance unit is also electrically connected to the first operational amplifier module, and the first resistance unit is grounded; The temperature coefficient of the first resistance unit is opposite to the temperature coefficient of the second resistance unit; The first resistor unit includes a first resistor, a first end of the first resistor is electrically connected to the second resistor unit, and a second end of the first resistor is grounded; The second resistor unit includes N second resistors and N first switches, the N second resistors are connected in series in sequence, the second end of the first second resistor is electrically connected to the first resistor unit, the first end of the Nth second resistor is electrically connected to the switch module, the first end of each second resistor is electrically connected to the first end of the corresponding first switch, the second ends of all the first switches are electrically connected to each other and to the first operational amplifier module, and the control ends of all the first switches are used to receive a first control signal, wherein N is an integer greater than or equal to 1; A temperature coefficient of the first resistor is smaller than a temperature coefficient of the second resistor.

2. The constant current source circuit according to claim 1, characterized in that: The current mirror module includes a first switch tube and a second switch tube, the gate of the first switch tube is electrically connected to the gate of the second switch tube and the first operational amplifier module respectively, the source of the first switch tube is electrically connected to the source of the second switch tube, and is used to be electrically connected to a first power supply, the drain of the first switch tube is electrically connected to the switch module and the second operational amplifier module respectively, and the drain of the second switch tube serves as the output end of the constant current source circuit, and is electrically connected to the second operational amplifier module and the load respectively.

3. The constant current source circuit according to claim 1, characterized in that: The switch module includes a third switch tube, a gate of the third switch tube is electrically connected to the second operational amplifier module, a source of the third switch tube is electrically connected to the current mirror module and the second operational amplifier module respectively, and a drain of the third switch tube is electrically connected to the resistance module.

4. The constant current source circuit according to claim 1, characterized in that: The second operational amplifier module includes a second operational amplifier, a first input end of the second operational amplifier is electrically connected to the current mirror module and the switch module respectively, a second input end of the second operational amplifier is electrically connected to the current mirror module and the load respectively, and an output end of the second operational amplifier is electrically connected to the switch module.

5. The constant current source circuit according to any one of claims 1 to 4, characterized in that: The constant current source circuit further includes a reference selection module, the reference selection module is electrically connected to the first operational amplifier module, and the reference selection module is used to output a corresponding reference voltage according to a second control signal.

6. An electronic device, characterized in that: The invention comprises the constant current source circuit as described in any one of claims 1 to 5.

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