Current detection circuit and switching power supply converter comprising same

By setting up a shunt branch in parallel on the shunt parallel branch of the current detection circuit, and using the computing resistor and signal conversion unit for signal processing, the detection accuracy problem caused by the resistance deviation and stray impedance during large current detection is solved, and high-precision current detection and low loss are achieved.

CN222913744UActive Publication Date: 2025-05-27HANGZHOU EV TECH CO LTD
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Patent Information

Application Number
CN202421320012.8
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-06-11
Publication Date
2025-05-27
Estimated Expiration
2034-06-11

AI Technical Summary

Technical Problem

When the existing current detection circuit detects a large current, due to the resistance deviation and stray impedance deviation between the current sensing resistors, the current values ​​flowing through each shunt branch are different, which in turn affects the detection accuracy and loss.

Method used

A current sensing circuit is designed, by setting up multiple shunt branches connected in parallel on the shunt parallel branch, setting up a current sensing resistor on each branch, and connecting to the signal conversion unit through the first and second sets of operational resistors, converting the input signal into a voltage output signal using an operational amplifier and a voltage divider resistor to detect the total current flowing through the shunt parallel branch.

Benefits of technology

This current detection circuit can detect the total current flowing through the shunt parallel branch with high accuracy when the resistance difference between the shunt branches is large, thereby reducing detection loss and improving detection accuracy.

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Abstract

The utility model provides a current detection circuit and a switching power supply converter comprising the same, and relates to the field of power supplies, and the current detection circuit comprises a shunt parallel branch which comprises a plurality of shunt branches connected in parallel, and each shunt branch is provided with a current detection resistor; the first end of each current detection resistor is connected to the first node through one operation resistor in the first group of operation resistors; the second end of each current detection resistor is connected to a second node through one operation resistor in the second group of operation resistors; and the signal conversion unit comprises a first input end connected with a first node, a second input end connected with a second node and an output end, and is used for converting an input signal between the first input end and the second input end into a voltage output signal so as to detect the total current flowing through the shunt parallel branch.
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Description

Technical Field

[0001] The present application relates to the field of power supplies, and particularly to a current detection circuit and a switching power converter including the same. Background Art

[0002] A switching power converter is a commonly used converter in the field of power supplies, and is widely used in various application scenarios, such as an on-vehicle charger.

[0003] In practical applications, it is necessary to sample the parameters of the switching power converter, such as obtaining signals such as its voltage, current or frequency, and feeding these sampled signals back to the control system of the switching power converter itself or reporting them to the system to control the switching power converter.

[0004] Therefore, the level of sampling accuracy directly affects the control accuracy of the switching power converter and the accuracy of reporting to the system, and thus directly affects the performance of the switching power converter. At present, the market has increasingly strict requirements for the electrical performance of the switching power converter. Therefore, in the design process of the switching power converter, it is necessary to strive to improve the sampling accuracy of its signals.

[0005] In addition, with the progress of technology, the requirements for the efficiency of the switching power converter are also becoming increasingly strict. Therefore, how to reduce the sampling loss is also a key concern. Summary of the Utility Model

[0006] An embodiment of the present application provides a current detection circuit, including: a shunt parallel branch, including a plurality of shunt branches connected in parallel, and a current detection resistor is disposed on each shunt branch; a first group of operational resistors, the first ends of the respective current detection resistors are respectively connected to a first node through an operational resistor in the first group of operational resistors; a second group of operational resistors, the second ends of the respective current detection resistors are respectively connected to a second node through an operational resistor in the second group of operational resistors; a signal conversion unit, including a first input end connected to the first node, a second input end connected to the second node, and an output end, for converting an input signal between the first input end and the second input end into a voltage output signal to detect the total current flowing through the shunt parallel branch.

[0007] Furthermore, the resistance values of the respective current detection resistors are equal.

[0008] Furthermore, the resistance values of the operational resistors in the first group of operational resistors and the resistance values of the operational resistors in the second group of operational resistors are both much larger than the resistance values of the respective current detection resistors.

[0009] Furthermore, the resistance values of the operational resistors in each of the first group of operational resistors and the resistance values of the operational resistors in each of the second group of operational resistors are between 1 milliohm and 10 milliohms, and the resistance values of the respective current detection resistors are between 1 ohm and 20 ohms.

[0010] Further, the resistance values of the operational resistors in each of the first groups of operational resistors are equal; the resistance values of the operational resistors in each of the second groups of operational resistors are equal.

[0011] Further, the resistance values of the operational resistors in each of the first groups of operational resistors are equal to the resistance values of the operational resistors in each of the second groups of operational resistors.

[0012] Further, the signal conversion unit includes: an operational amplifier, where the first input terminal is the non-inverting input terminal of the operational amplifier, and the second input terminal is the inverting input terminal of the operational amplifier.

[0013] Further, a voltage-dividing resistor is further included, and the voltage-dividing resistor is connected between the first input terminal and the second input terminal.

[0014] The present application further provides a switching power supply converter, including: the above-mentioned current detection circuit, and the shunt parallel branches are connected in parallel and then connected in series in the switching power supply converter.

[0015] Further, the switching power supply converter is an AC / DC converter, an AC / AC converter, a DC / AC converter, or a DC / DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 Shows a schematic diagram of a typical current detection circuit.

[0018] Figure 2 Shows a schematic diagram of the current detection circuit according to an embodiment of the present application.

[0019] Figure 3 Shows a schematic diagram of the current detection circuit according to another embodiment of the present application.

[0020] Figure 4 Shows a schematic diagram of the switching power supply converter according to an embodiment of the present application.

[0021] Unless otherwise specified, the corresponding numbers and symbols in different drawings generally refer to the corresponding parts. These drawings are drawn to clearly illustrate the relevant aspects of various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0023] It should be understood that the terms "first", "second", etc. in the claims, the description and the drawings of the present application are used to distinguish different objects, rather than to describe a specific order. The terms "comprising" and "including" used in the description and claims of the present application indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0024] In practical applications, there is often a large current flowing through the switching power supply converter. For example, the output current of the in-vehicle DC / DC converter is generally between 100A and 300A. And in practical applications, the current value is often sampled through a detection circuit formed by a sampling resistor and its peripheral circuit.

[0025] In practical applications, in order to achieve low-power consumption detection for the large-current detection circuit, multiple current detection resistors with the same resistance value are often connected in parallel for detection. The detection point is usually selected at the root of one of the current detection resistors to detect the current value flowing through the current detection resistor, and then the detected current value is multiplied by the number of current detection resistors to obtain the total current flowing through the detection circuit.

[0026] Specifically, reference can be made to Figure 1 the schematic diagram of the typical current detection circuit shown, as Figure 1 shown, n shunt branches are connected in parallel to form a shunt parallel branch 110, and a current detection resistor is provided on each shunt branch, such as current detection resistors R1, R2,... Rn. As Figure 1 shown, an operational resistor Rs is respectively led out from the root of the current detection resistor Rn, and then the current In flowing through the current detection resistor Rn is obtained through the operational amplifier 141, that is, the root of the current detection resistor Rn is selected as the detection point, and then the total large current Ia flowing through the shunt parallel branch 110 is obtained through the formula Ia = n * In. This current detection circuit has the advantage of small detection loss.

[0027] However, through the research of the inventor, it is found that Figure 1To achieve high-precision detection of the current detection circuit shown, it is necessary to ensure that the current flowing through each shunt branch is equal. However, this is impossible to achieve in actual engineering applications. The resistance deviation between current detection resistors and the stray impedance deviation of each shunt branch caused by PCB traces are inevitable. At the same time, the resistance values of each shunt branch may not be exactly the same due to other reasons, which results in unequal current values flowing through each shunt branch. Especially in the case of high-current applications, the difference in current values between each shunt branch will be even greater. Therefore, the method of calculating the total current Ia by detecting the current through one of the shunt branches results in a relatively large measurement current error.

[0028] Therefore, how to design a current detection circuit that can accurately detect the total current flowing through the shunt parallel branches regardless of the resistance difference of each shunt branch has become a technical problem faced by the switching power supply converter, especially for the switching power supply converter with a large circuit.

[0029] Based on this, in an embodiment of the present application, a current detection circuit is proposed. Specifically, reference can be made to Figure 2 the schematic diagram of the current detection circuit according to an embodiment of the present application shown in Figure 2 As shown, the present application proposes a current detection circuit, including:

[0030] A shunt parallel branch 110, including multiple shunt branches connected in parallel, and a current detection resistor (such as R1, R2, to Rn, where n is a natural number) is provided on each shunt branch;

[0031] A first group of operational resistors 120, the first ends of each current detection resistor are respectively connected to the first node 301 through an operational resistor (such as Rs11, Rs12, to Rs1n) in the first group of operational resistors 120;

[0032] A second group of operational resistors 130, the second ends of each current detection resistor are respectively connected to the second node 302 through an operational resistor (such as Rs21, Rs22, to Rs2n) in the second group of operational resistors 130;

[0033] A signal conversion unit 140, including a first input terminal connected to the first node 301, a second input terminal connected to the second node 302, and an output terminal, for converting the input signal between the first input terminal and the second input terminal into a voltage output signal to detect the total current Ia flowing through the shunt parallel branch 110.

[0034] In an embodiment, the resistance values of each current detection resistor R1, R2,... Rn are equal. Denote its resistance value as R.

[0035] In one embodiment, the resistance values of the operational resistors in the first group of operational resistors 120 and the resistance values of the operational resistors in the second group of operational resistors 130 are both much greater than the resistance values of the respective current detection resistors.

[0036] Specifically, for example, the resistance values of the operational resistors in each of the first group of operational resistors 120 and the resistance values of the operational resistors in each of the second group of operational resistors 130 are between 1 milliohm and 10 milliohms, and the resistance values of the respective current detection resistors are between 1 ohm and 20 ohms.

[0037] In one embodiment, the resistance values of the operational resistors in each of the first group of operational resistors 120 are equal; the resistance values of the operational resistors in each of the second group of operational resistors 130 are equal.

[0038] In one embodiment, the resistance values of the operational resistors in each of the first group of operational resistors 120 are equal to the resistance values of the operational resistors in each of the second group of operational resistors 130, denoted as Rs.

[0039] In one embodiment, as Figure 2 shown, the signal conversion unit 140 is implemented as an operational amplifier 141, the first input terminal is the non-inverting input terminal of the operational amplifier 141, the second input terminal is the inverting input terminal of the operational amplifier 141, and the voltage between the first input terminal 208 and the second input terminal 209 is denoted as Vin.

[0040] Please refer to Figure 3 the schematic diagram of the current detection circuit according to another embodiment of the present application shown. A voltage-dividing resistor Rin is also connected between the first input terminal and the second input terminal of the operational amplifier 141. Of course, as Figure 2 shown, if the voltage-dividing resistor Rin is not included, then the resistance between the first input terminal and the second input terminal of the operational amplifier 141 approaches infinity.

[0041] Of course, the signal conversion unit 140 can also be implemented as other signal conversion circuits to convert the voltage Vin between the first input terminal 208 and the second input terminal 209 into a signal that can be processed by the subsequent circuit and can reflect the magnitude of the voltage Vin.

[0042] As Figure 3 shown, it can also be referred to Figure 2, mark the detected current (i.e., the current flowing through the shunt parallel branch 110, or the branch current of the switching power supply converter) as Ia, and mark the currents flowing into the n current detection resistors R1, R2, …, Rn as I1, I2, …, In respectively. Then the voltages across the current detection resistors on the n shunt branches are In*Rn. Since the resistance values of the operational resistors in the first group of operational resistors 120 and the second group of operational resistors 130 are much larger than the resistance value R of each current detection resistor, the current detection resistor can be regarded as a voltage source. According to the voltage superposition principle, it can be deduced that:

[0043]

[0044] It can be understood that the first half of formula (1) is the series voltage division ratio of n Rs in parallel and Rin, and the second half of formula (1) is the voltage formed by the total current Ia across the n parallel current detection resistors. From formula (1), it can be seen that even if I1, I2…In are not equal, the detection value formed according to the input voltage Vin of the operational amplifier 141 can still reflect the magnitude of the total current Ia. Therefore, the detection accuracy can be improved and the loss is small.

[0045] Furthermore, for Figure 3 where Rin is equal to infinity, according to the first half of formula (1) which is approximately 1, the calculation formula for the voltage Vin obtained from formula (1) is:

[0046]

[0047] It can be seen that the detection accuracy is higher.

[0048] Furthermore, the present application also provides a switching power supply converter. Please refer to Figure 4 the schematic diagram of the switching power supply converter according to an embodiment of the present application shown in. The switching power supply converter provided by the present application includes the aforementioned current detection circuit to detect the current in a branch circuit within the switching power supply converter. As Figure 4 shown, the shunt parallel branches 110 are connected in parallel and then in series within the switching power supply converter.

[0049] In an embodiment, the switching power supply converter can be an AC / DC converter, an AC / AC converter, a DC / AC converter or a DC / DC converter. That is, it can be applied to any type of switching power supply converter as long as a current, especially a large current, flows through a certain branch within it and the current needs to be detected.

[0050] In a specific embodiment, the switching power supply converter is a vehicle-mounted DC / DC converter, and the aforementioned current detection circuit is used to detect the output current of the vehicle-mounted DC / DC converter.

[0051] The above specific embodiments and the accompanying drawings are only illustrative of the technical solutions and their technical effects of the present utility model, rather than limiting the present utility model. Any person skilled in the art who is familiar with this technology can modify or change the above embodiments within the scope of protection of the claims without departing from the technical principle and spirit of the present utility model, and all belong to the scope of protection of the rights of the present utility model.

Claims

1. A current detection circuit, characterized in that: include: The shunt parallel branch includes a plurality of shunt branches connected in parallel, each shunt branch is provided with a current detection resistor; A first group of operational resistors, wherein the first end of each current detection resistor is connected to the first node through an operational resistor in the first group of operational resistors; A second group of operational resistors, wherein the second end of each current detection resistor is connected to the second node through an operational resistor in the second group of operational resistors; The signal conversion unit includes a first input terminal connected to the first node, a second input terminal connected to the second node, and an output terminal, and is used to convert the input signal between the first input terminal and the second input terminal into a voltage output signal to detect the total current flowing through the shunt parallel branch.

2. The current detection circuit according to claim 1, characterized in that: The resistance values ​​of each current sensing resistor are equal.

3. The current detection circuit according to claim 1, characterized in that: The resistance values ​​of the operational resistors in the first group of operational resistors and the operational resistors in the second group of operational resistors are both much greater than the resistance values ​​of the current detection resistors.

4. The current detection circuit according to claim 3, characterized in that: The resistance value of each operational resistor in the first group of operational resistors and the resistance value of each operational resistor in the second group of operational resistors are between 1 milliohm and 10 milliohms, and the resistance value of each current detection resistor is between 1 ohm and 20 ohms.

5. The current detection circuit according to claim 1, characterized in that: The resistance values ​​of the operational resistors in each of the first operational resistor groups are equal; The resistance values ​​of the operational resistors in each of the second operational resistor groups are equal.

6. The current detection circuit according to claim 1, characterized in that: The resistance value of each operational resistor in the first operational resistor group is equal to the resistance value of each operational resistor in the second operational resistor group.

7. The current detection circuit according to claim 1, characterized in that: The signal conversion unit comprises: an operational amplifier, the first input end is a non-inverting input end of the operational amplifier, and the second input end is a reverse input end of the operational amplifier.

8. The current detection circuit according to claim 1 or 7, characterized in that: The device further comprises a voltage dividing resistor connected between the first input terminal and the second input terminal.

9. A switching power converter, characterized in that: include: The current detection circuit described in any one of claims 1-8, wherein the shunt parallel branches are connected in parallel and then connected in series in the switching power converter.

10. The switching power converter according to claim 9, characterized in that: The switching power converter is an AC / DC converter, an AC / AC converter, a DC / AC converter or a DC / DC converter.