Current sensing circuits and integrated circuits for monitoring current sources

Abstract

The present invention relates to a current detection circuit and an integrated circuit for monitoring a current source, wherein the current detection circuit comprises: a sensing resistor connected to one end of the current source; and a shunt unit connected in parallel with the sensing resistor, wherein when the sensing voltage of the sensing resistor exceeds a first predetermined voltage, the shunt unit is turned on to keep the sensing voltage constant. The current detection circuit of the present invention can effectively and accurately detect the current of the current source, can detect relatively small currents, and can also reduce the voltage drop when a large current flows through. In addition, it has the beneficial effects of being simple in structure and easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a current detection circuit and an integrated circuit for monitoring a current source. Background Art

[0002] Functional safety is a key consideration in many automotive applications. Circuit functions often need to be monitored while they are in operation. If improper operation is detected, it needs to be reported to the controller circuit so that the controller circuit can take action to control or correct the fault.

[0003] To keep the battery balanced, the current source of new energy vehicles has a wide operating range, ranging from about a few mA to hundreds of mA. In order to monitor the battery system of new energy vehicles, a current detection circuit is required that can detect relatively small currents while conducting very large currents.

[0004] Figure 1 It is a schematic diagram of a current detection circuit using a sensing resistor. Among them, the current source 110 and the sensing resistor Rsense are connected in series, and the sensing resistor Rsense is connected in parallel with the current detector 120. Assuming that we need the output current Iout of the current source to be 5mA, the voltage drop Vsense on the sensing resistor Rsense needs to be 100mV to obtain a reliable detection result, which can be achieved by setting the sensing resistor Rsense to 20Ω. However, when the output current of the current source is Iout=200mA, the voltage drop on the sensing resistor Rsense will become 4V. In many applications, the current detection circuit is not allowed to generate such a large voltage drop because it will limit the voltage space allowed by the detection circuit.

[0005] Another simple current sensing circuit uses a diode. A diode has the desired nonlinear characteristic, that is, its impedance is low when the current flowing through it is high. However, the voltage drop across the diode is usually fixed at a high level, such as around 0.6V.

[0006] Figure 2 is a schematic diagram of another current sensing circuit using a sense resistor. Figure 2 As shown, the current detection circuit decomposes a large current source into multiple small current sources 211-214. For each current source 211-214, a similar Figure 1 As shown in the current detectors 221-224, each current source 211-214 has a corresponding sensing resistor 231-234 to obtain the required voltage drop. Figure 2 The circuit shown requires a large number of independent current sensors, which increases the complexity and power consumption of the circuit. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a current detection circuit for accurately monitoring the current of a current source.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is a current detection circuit for monitoring a current source, characterized in that it includes: a sensing resistor connected to one end of the current source; and a shunt unit connected in parallel with the sensing resistor, when the sensing voltage of the sensing resistor exceeds a first predetermined voltage, the shunt unit is turned on to keep the sensing voltage constant.

[0009] In an embodiment of the present invention, the output current of the current source has a first current range, and the ratio of the first predetermined voltage to the sensing resistor is within the first current range.

[0010] In one embodiment of the present invention, the shunt unit includes a semiconductor switch element and a first comparator, wherein the semiconductor switch element includes a control end, an input end and an output end, the input end is connected to one end of the current source, the input end is also connected to the first end of the sensing resistor, the output end is connected to the second end of the sensing resistor, and the control end is connected to the first output end of the first comparator; and the first comparator includes a first positive input end, a first negative input end and a first output end, the first positive input end is connected to the first end of the sensing resistor, the first negative input end is connected to the first predetermined voltage, and the first output end is connected to the control end.

[0011] In one embodiment of the present invention, a second comparator is further included, the second comparator includes a second positive input terminal, a second negative input terminal and a second output terminal, the second positive input terminal is connected to the control terminal, the second negative input terminal is connected to a second predetermined voltage, wherein when the control terminal voltage of the control terminal exceeds the second predetermined voltage, the second output terminal outputs a first indication signal.

[0012] In one embodiment of the present invention, it also includes: an overcurrent detection unit connected to the shunt unit, the shunt unit has a maximum current threshold allowed to pass, when the current passing through the shunt unit is greater than the maximum current threshold, the overcurrent detection unit outputs an overcurrent indication signal.

[0013] In one embodiment of the present invention, it also includes: an overcurrent detection unit, the overcurrent detection unit includes a third comparator, the third comparator includes a third positive input terminal, a third negative input terminal and a third output terminal, the third positive input terminal is connected to the control terminal, the third negative input terminal is connected to a third predetermined voltage, wherein when the control terminal voltage of the control terminal exceeds the third predetermined voltage, the third output terminal outputs an overcurrent indication signal.

[0014] In one embodiment of the present invention, the third predetermined voltage is greater than the second predetermined voltage.

[0015] In one embodiment of the present invention, the sensing resistor comprises a variable resistor.

[0016] To solve the above technical problem, the present invention also provides an integrated circuit for monitoring a current source, comprising the above-mentioned current detection circuit.

[0017] According to the current detection circuit and integrated circuit of the present invention, the output current of the current source is shunted by a shunt unit connected in parallel with the sensing resistor, so that the sensing voltage on the sensing resistor does not increase continuously with the output current, but is maintained at a certain voltage level. The current detection circuit of the present invention can monitor a relatively small current in the current source, and when the current is large, the voltage drop of the current detection circuit is still small, so that the current source can be effectively and accurately detected. At the same time, the current detection circuit of the present invention also has the beneficial effects of simple structure and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein:

[0019] Figure 1 is a schematic diagram of a current sensing circuit using a sense resistor;

[0020] Figure 2 is a schematic diagram of another current sensing circuit using a sense resistor;

[0021] Figure 3 is a structural schematic diagram of a current detection circuit according to an embodiment of the present invention;

[0022] Figure 4 is a structural schematic diagram of a current detection circuit according to another embodiment of the present invention;

[0023] Figure 5 is a structural schematic diagram of a current detection circuit according to another embodiment of the present invention;

[0024] Figure 6 yes Figure 5 The signal waveform diagram of the current detection circuit of the embodiment shown in the working state. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0028] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0029] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0030] It should be understood that when a component is referred to as being "on another component," "connected to another component," "coupled to another component," or "contacting another component," it may be directly on, connected to, coupled to, or contacting the other component, or there may be intervening components. In contrast, when a component is referred to as being "directly on another component," "directly connected to," "directly coupled to," or "directly contacting" another component, there are no intervening components. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0031] Figure 3 Schematic diagram of the structure of a current detection circuit according to an embodiment of the present invention. Figure 3 As shown, the current detection circuit 300 of this embodiment includes a sensing resistor Rsense and a shunt unit 310. The sensing resistor Rsense is connected to one end of the current source 301. The shunt unit 310 is connected in parallel with the sensing resistor Rsense. When the sensing voltage Vsense of the sensing resistor Rsense exceeds the first predetermined voltage Vth1, the shunt unit 310 is turned on to keep the sensing voltage Vsense constant.

[0032] It should be noted that in the present invention, "exceed" may mean greater than or greater than or equal to. The sense voltage Vsense exceeding the first predetermined voltage Vth1 includes two situations: Vsense>Vth1 and Vsense≥Vth1, both of which are within the scope of protection of the present invention.

[0033] According to the current detection circuit of the present invention, a relatively small current can be accurately measured, and a large current can also be passed through the circuit without generating a large voltage drop in the circuit.

[0034] In some embodiments, the output current of the current source 301 has a first current range. When the first predetermined voltage Vth1 is set, the ratio of the first predetermined voltage Vth1 to the sensing resistor Rsense is within the first current range.

[0035] refer to Figure 3 As shown, the shunt unit 310 of this embodiment includes a semiconductor switch element 320 and a first comparator 330, wherein the semiconductor switch element 320 includes a control terminal 321, an input terminal 322 and an output terminal 323, the input terminal 322 is connected to one end of the current source 301, the input terminal 322 is also connected to the first end 311 of the sensing resistor Rsense, the output terminal 323 is connected to the second end 312 of the sensing resistor Rsense, the control terminal 321 is connected to the first output terminal 333 of the first comparator 330. The first comparator 330 includes a first positive input terminal 331, a first negative input terminal 332 and a first output terminal 333, the first positive input terminal 331 is connected to the first end 311 of the sensing resistor Rsense, the first negative input terminal 332 is connected to the first predetermined voltage Vth1, and the first output terminal 333 is connected to the control terminal 321.

[0036] The present invention does not limit the specific implementation of the semiconductor switch element 320, which may be a semiconductor switch element having three terminals, namely, a control terminal, an input terminal, and an output terminal, or an electronic component network composed of electronic components. Common semiconductor switch elements may include transistors and field effect transistors, including but not limited to PMOS, NMOS, DMOS, BJT, etc.

[0037] The sense resistor Rsense and the first predetermined voltage Vth1 together can set the magnitude of the detection current Idetect to be detected by the current detection circuit, that is, Idetect = Vth1 / Rsense.

[0038] When the output current Iout of the current source 301 > Idetect, the voltage Vgate at the control terminal 321 of the semiconductor switching element 320 will rise rapidly, causing the semiconductor switching element 320 to be in the on state. Since the semiconductor switching element 320 is turned on, a shunting effect is produced on the output current Iout of the current source 301, so that the voltage drop across the sense resistor Rsense can be kept constant, that is, the sense voltage Vsense is almost maintained constant.

[0039] Figure 4 It is a schematic structural diagram of a current detection circuit according to another embodiment of the present invention. Refer to Figure 4 As shown, the current detection circuit 400 of this embodiment is Figure 3 Compared with the current detection circuit 300 shown, a second comparator 410 is added to the shunt unit 310. The second comparator 410 includes a second positive input terminal 411, a second negative input terminal 412, and a second output terminal 413. The second positive input terminal 411 is connected to the control terminal 321, and the second negative input terminal 412 is connected to the second predetermined voltage Vth2. Among them, when the control terminal voltage Vgate at the control terminal 321 exceeds the second predetermined voltage Vth2, the second output terminal 413 outputs a first indication signal OUT.

[0040] According to Figure 4 As shown in the embodiment, the second comparator 410 compares the control terminal voltage Vgate with the second predetermined voltage Vth2. When the output current Iout of the current source 301 exceeds the predetermined detection current Idetect, the second comparator 410 outputs a first prompt signal OUT to give a prompt.

[0041] In some embodiments, the second comparator 410 outputs a high level or a low level. Assuming that when Iout < Idetect, the second output terminal 413 of the second comparator 410 outputs a low level; then when Iout > Idetect, the second output terminal 413 of the second comparator 410 outputs a high level.

[0042] Figure 5 It is a schematic structural diagram of a current detection circuit according to another embodiment of the present invention. Refer to Figure 5 As shown, the current detection circuit 500 of this embodiment is Figure 4Compared with the current detection circuit 400 shown in the figure, an overcurrent detection unit 510 is added. The shunt unit 310 has a maximum current threshold Imax allowed to pass through, and the overcurrent detection unit 510 is connected to the shunt unit 310. When the current passing through the shunt unit 310 is greater than the maximum current threshold Imax, the overcurrent detection unit 510 outputs an overcurrent indication signal OC.

[0043] although Figure 3 and Figure 4 The current detection circuit shown can keep the sensing voltage Vsense on the sensing resistor Rsense almost constant through the shunt unit 310. However, when the output current Iout of the current source 301 increases to a certain extent, the shunt unit 310 can no longer function normally, and the sensing voltage Vsense may continue to increase.

[0044] The present invention does not limit the specific implementation of the overcurrent detection unit 510.

[0045] refer to Figure 5 As shown, in some embodiments, the overcurrent detection unit 510 includes a third comparator 520, the third comparator 520 includes a third positive input terminal 521, a third negative input terminal 522 and a third output terminal 523, the third positive input terminal 521 is connected to the control terminal 321, the third negative input terminal 522 is connected to the third predetermined voltage Vth3, wherein when the control terminal voltage Vgate of the control terminal 321 exceeds the third predetermined voltage Vth3, the third output terminal 523 outputs an overcurrent indication signal OC (Over Current).

[0046] according to Figure 5 In the embodiment shown, when the control terminal voltage Vgate exceeds the third predetermined voltage Vth3, the current passing through the shunt unit 310 is greater than the maximum current threshold Imax that it can withstand. Therefore, the setting of the third predetermined voltage Vth3 is related to the maximum current threshold Imax of the shunt unit 310. Specifically, the maximum current threshold Imax can be obtained according to the performance of the components used in the shunt unit 310, and then the third predetermined voltage Vth3 can be set. In some embodiments, the third predetermined voltage Vth3 is set according to the performance of the semiconductor switch element 320.

[0047] In some embodiments, the third predetermined voltage Vth3 is greater than the second predetermined voltage Vth2.

[0048] Figure 3-4 The current detection circuit shown can not only detect the current source effectively and accurately, but also has the beneficial effects of simple structure and easy implementation.

[0049] Figure 6 yes Figure 5Signal waveform diagram of the current detection circuit of the illustrated embodiment in the working state. Refer to Figure 6 As shown, it includes three coordinate systems, and the horizontal axis of each coordinate system is the output current Iout of the current source 301. It should be noted that Figure 6 As shown, it is only for illustration, and the horizontal axis Iout does not represent a linear coordinate, but may be a non-linear coordinate such as a logarithmic coordinate.

[0050] Refer to Figure 6 As shown, the vertical axis of the coordinate system 610 is the sense voltage Vsense, and the coordinate system 610 is used to represent the relationship between the sense voltage Vsense and the output current Iout. The vertical axis of the coordinate system 620 is the control terminal voltage Vgate, and the coordinate system 620 is used to represent the relationship between the control terminal voltage Vgate and the output current Iout. The vertical axis of the coordinate system 630 is the first prompt signal OUT, and the coordinate system 630 is used to represent the relationship between the first prompt signal OUT and the output current Iout. Among them, the dotted line 640 that vertically passes through the three coordinate systems represents the position of the detection current Idetect to be detected by the current detection circuit on the horizontal axis Iout.

[0051] Refer to Figure 6 As shown, when Iout < Idetect, there is a linear relationship between the sense voltage Vsense and the output current Iout, and the sense voltage Vsense increases as the output current Iout increases. In this stage, the output current Iout can be accurately detected. When the sense voltage Vsense exceeds the first predetermined voltage Vth1, since the shunt unit 310 is turned on, a part of the output current Iout passes through the shunt unit 310, so that the sense voltage Vsense remains unchanged. As Figure 6 As shown, the sense voltage Vsense has a slight increase in the first segment 611 as the output current Iout increases, and it can be considered that it remains basically stable.

[0052] Refer to Figure 6 As shown, when Iout < Idetect, the control terminal voltage Vgate is 0, indicating that the shunt unit 310 is in the off state, the semiconductor switch element 320 is not conducting, and its shunt function has not been activated yet. When Iout > Idetect, the control terminal voltage Vgate gradually increases, the shunt unit 310 is turned on, the semiconductor switch element 320 conducts, and the shunt function starts to work.

[0053] Refer to Figure 6As shown, when Iout < Idetect, the first prompt signal OUT is 0. When the control terminal voltage Vgate exceeds the second predetermined voltage Vth2, the first prompt signal OUT is switched to 1, indicating that the output current Iout of the current source 301 exceeds the predetermined detection current Idetect. It can be understood that there is a certain delay between the moment when the first prompt signal OUT becomes 1 and the actual moment when the output current Iout reaches the detection current Idetect. Since the semiconductor switching element 320 is still within the normal dynamic range at this time, the sense voltage Vsense remains unchanged. This delay does not affect the normal operation of the current detection circuit.

[0054] Reference Figure 6 As shown, as the output current Iout continues to increase, when the control terminal voltage Vgate exceeds the third predetermined voltage Vth3, it indicates that the passing current of the shunt unit 310 is greater than the maximum current threshold Imax that it can withstand, and then the third output terminal 523 outputs an overcurrent indication signal OC. Reference Figure 6 As shown, when the control terminal voltage Vgate exceeds the third predetermined voltage Vth3, the sense voltage Vsense significantly starts to rise in the second section 612, indicating that the output current Iout of the current source 301 that is conducting in this current detection circuit is extremely large, indicating that an error may have occurred in the current source 301. In some cases, the error of the current source 301 includes a short circuit.

[0055] In some embodiments, the sense resistor Rsense includes a variable resistor. In these embodiments, the size of the sense resistor Rsense can be adjusted according to the size of the current source to be detected, so that the sense resistor Rsense matches the current source to be detected, so that the current detection circuit of the present invention can be applicable to current sources with different ranges.

[0056] The present invention also includes an integrated circuit for monitoring a current source, and the integrated circuit includes Figure 3-5 any one of the current detection circuits shown in

[0057] According to the current detection circuit of the present invention and the integrated circuit including the current detection circuit, a current source with a large dynamic range can be accurately monitored.

[0058] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only an example and does not constitute a limitation to this application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are proposed in this application, so such modifications, improvements, and corrections still belong to the spirit and scope of the exemplary embodiments of this application.

[0059] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0060] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

Claims

1. A current detection circuit for monitoring a current source, characterized in that: include: A sensing resistor connected to one end of the current source; as well as A shunt unit connected in parallel with the sensing resistor, when the sensing voltage of the sensing resistor exceeds a first predetermined voltage, the shunt unit is turned on to keep the sensing voltage constant; The shunt unit includes a semiconductor switch element and a first comparator, wherein the semiconductor switch element includes a control end, an input end and an output end, the input end is connected to one end of the current source, the input end is also connected to the first end of the sensing resistor, the output end is connected to the second end of the sensing resistor, and the control end is connected to the first output end of the first comparator; and the first comparator includes a first positive input end, a first negative input end and a first output end, the first positive input end is connected to the first end of the sensing resistor, the first negative input end is connected to the first predetermined voltage, and the first output end is connected to the control end.

2. The current detection circuit according to claim 1, characterized in that: The output current of the current source has a first current range, and a ratio of the first predetermined voltage to the sensing resistor is within the first current range.

3. The current detection circuit according to claim 1, characterized in that: It also includes a second comparator, which includes a second positive input terminal, a second negative input terminal and a second output terminal, the second positive input terminal is connected to the control terminal, and the second negative input terminal is connected to a second predetermined voltage, wherein when the control terminal voltage of the control terminal exceeds the second predetermined voltage, the second output terminal outputs a first indication signal.

4. The current detection circuit according to claim 1, characterized in that: Also includes: An overcurrent detection unit is connected to the shunt unit, the shunt unit has a maximum current threshold allowed to pass, and when the current passing through the shunt unit is greater than the maximum current threshold, the overcurrent detection unit outputs an overcurrent indication signal.

5. The current detection circuit according to claim 1 or 3, characterized in that: Also includes: An overcurrent detection unit, the overcurrent detection unit includes a third comparator, the third comparator includes a third positive input terminal, a third negative input terminal and a third output terminal, the third positive input terminal is connected to the control terminal, the third negative input terminal is connected to a third predetermined voltage, wherein when the control terminal voltage of the control terminal exceeds the third predetermined voltage, the third output terminal outputs an overcurrent indication signal.

6. The current detection circuit according to claim 3, characterized in that: The second predetermined voltage is greater than or equal to the first predetermined voltage.

7. The current detection circuit according to claim 1, characterized in that: The sensing resistor includes a variable resistor.

8. An integrated circuit for monitoring a current source, characterized in that: The invention comprises a current detection circuit as described in any one of claims 1 to 7.

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