An overcurrent detection circuit suitable for a high current power supply

Abstract

The utility model relates to the technical field of relay protection, especially a kind of overcurrent detection circuit suitable for large-current power supply, including current mutual inductance module and overcurrent threshold sampling module;Current mutual inductance module and fire line electric connection, overcurrent threshold sampling module is electrically connected with fire line and zero line respectively;Current mutual inductance module is used to convert the current signal of fire line into real-time voltage signal by electromagnetic induction;Overcurrent threshold sampling module is used to sample the voltage signal between fire line and zero line, generates real-time overcurrent threshold;Solve the problem that fixed preset overcurrent threshold cannot adapt to the overcurrent detection of large-current power supply, resulting in low detection accuracy.

Description

Technical Field

[0001] This utility model relates to the field of relay protection technology, and in particular to an overcurrent detection circuit suitable for high current power supplies. Background Technology

[0002] Currently, critical scenarios such as high-end medical care, precision instruments, and industrial production have high requirements for power supply safety. They usually adopt a dual power supply method with main and backup power. Under normal circumstances, the main power supply (mains power) provides power. When the main power supply experiences a voltage drop or other fault, it switches to the backup power supply (independent energy storage, etc.) to provide power supply protection until the main power supply is restored and switched back, thereby ensuring the reliability of the user's power supply.

[0003] To prevent excessive current from burning out the dual power supply switching controller or damaging the power electronic switches, overcurrent protection design is typically required for both the main and backup power lines. Existing overcurrent protection circuits can be built using fuses, overcurrent protection chips, discrete components, microcontrollers (such as MCUs), etc. Among them, the overcurrent detection part mainly uses a microcontroller to program and preset an overcurrent threshold, which is then compared with the detected current value to determine whether there is an overcurrent fault in the main power supply (or backup power supply).

[0004] However, while overcurrent detection with a preset overcurrent threshold can meet the overcurrent detection requirements under low-current power supply conditions, under high-load, high-current power supply conditions (dual power supply scenarios are usually high current), especially when it is an AC power supply, the dynamic changes in current and voltage are relatively large. Judging whether there is an overcurrent solely by the preset overcurrent threshold has certain errors in detection accuracy and cannot adapt to real-time overcurrent detection of dynamic changes and fluctuations. Utility Model Content

[0005] To address the aforementioned shortcomings, the purpose of this invention is to propose an overcurrent detection circuit suitable for high-current power supplies, which solves the problem that a fixed preset overcurrent threshold cannot be adapted to the overcurrent detection of high-current power supplies, resulting in low detection accuracy.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] An overcurrent detection circuit suitable for high-current power supplies includes a current transformer module and an overcurrent threshold sampling module; the current transformer module is electrically connected to the live wire, and the overcurrent threshold sampling module is electrically connected to both the live wire and the neutral wire.

[0008] The current transformer module is used to convert the current signal of the live wire into a real-time voltage signal through electromagnetic induction.

[0009] The overcurrent threshold sampling module is used to sample the voltage signal between the live wire and the neutral wire to generate a real-time overcurrent threshold.

[0010] Furthermore, the overcurrent threshold sampling module includes resistor R3, resistor R4, and current detection amplifier U3; one end of resistor R3 is electrically connected to the live wire, the other end of resistor R3 and one end of resistor R4 are both electrically connected to the positive input terminal of current detection amplifier U3, the other end of resistor R4 and the neutral wire are both electrically connected to the negative input terminal of current detection amplifier U3, and the output terminal of current detection amplifier U3 is used to output the real-time overcurrent threshold.

[0011] Furthermore, the current sensing amplifier U3 is composed of an INA240 chip and its peripheral circuitry.

[0012] Furthermore, the current transformer module includes a current transformer U1 and a sampling resistor R1; the live wire passes through the busbar through hole of the current transformer U1, one end of the secondary winding terminal of the current transformer U1 is grounded, and the other end of the secondary winding terminal of the current transformer U1 is used to output the real-time voltage signal; the sampling resistor R1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

[0013] Furthermore, the current transformer module also includes a bidirectional TVS diode D1; the bidirectional TVS diode D1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

[0014] The technical solution provided by this utility model can include the following beneficial effects: the current transformer module converts the current signal of the live wire (i.e., the power bus) into a real-time voltage signal through electromagnetic induction; the overcurrent threshold sampling module obtains the real-time overcurrent threshold (also a voltage signal) through the voltage between the live and neutral wires of the power bus; the subsequent circuit system can realize overcurrent detection by comparing the real-time voltage signal and the real-time overcurrent threshold. The advantage of this detection circuit is that the overcurrent threshold signal is not a preset value in the circuit system, but a real-time response based on the voltage between the live and neutral wires. It can not only be used for DC overcurrent detection, but also adapt to the dynamic changes of AC, thus improving the detection accuracy. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of an overcurrent detection circuit suitable for high-current power supplies, which is one embodiment of this utility model.

[0016] The components include: current transformer module 1, overcurrent threshold sampling module 2, resistor R3, resistor R4, current detection amplifier U3, current transformer U1, sampling resistor R1, and bidirectional TVS diode D1. Detailed Implementation

[0017] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0018] In the description of embodiments of this utility model, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0019] In the description of the embodiments of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model according to the specific circumstances.

[0020] The following is combined with Figure 1 This invention describes an overcurrent detection circuit suitable for high-current power supplies according to an embodiment of the present invention.

[0021] An overcurrent detection circuit suitable for high-current power supplies includes a current transformer module 1 and an overcurrent threshold sampling module 2; the current transformer module 1 is electrically connected to the live wire, and the overcurrent threshold sampling module 2 is electrically connected to both the live wire and the neutral wire.

[0022] Current transformer module 1 is used to convert the current signal of the live wire into a real-time voltage signal through electromagnetic induction.

[0023] The overcurrent threshold sampling module 2 is used to sample the voltage signal between the live wire and the neutral wire to generate a real-time overcurrent threshold.

[0024] This utility model proposes a preferred embodiment of an overcurrent detection circuit suitable for high-current power supplies, such as... Figure 1As shown, the current transformer module 1 converts the current signal of the live wire (i.e., the power bus) into a real-time voltage signal through electromagnetic induction. The overcurrent threshold sampling module 2 obtains the real-time overcurrent threshold (also a voltage signal) through the voltage between the live and neutral wires of the power bus. The subsequent circuit system can realize overcurrent detection by comparing the real-time voltage signal and the real-time overcurrent threshold. The advantage of this detection circuit is that the overcurrent threshold signal is not a preset value in the circuit system, but a real-time response based on the voltage between the live and neutral wires. It can be used not only for DC overcurrent detection, but also adapt to the dynamic changes of AC, thus improving the detection accuracy.

[0025] It should be noted that the current transformer module 1 and the overcurrent threshold sampling module 2 are used as a group to detect one phase of the live wire. When it is necessary to detect three phases of the live wire, three groups need to be added. When it is necessary to detect the main and backup power supplies, one group or three groups can be set up respectively. This overcurrent detection circuit can be expanded to have more usage methods according to the actual situation.

[0026] Furthermore, the overcurrent threshold sampling module 2 includes resistors R3 and R4 and a current sensing amplifier U3; one end of resistor R3 is electrically connected to the live wire, the other end of resistor R3 and one end of resistor R4 are both electrically connected to the positive input terminal of the current sensing amplifier U3, the other end of resistor R4 and the neutral wire are both electrically connected to the negative input terminal of the current sensing amplifier U3, and the output terminal of the current sensing amplifier U3 is used to output the real-time overcurrent threshold.

[0027] In this embodiment, the overcurrent threshold sampling module 2 is composed of a voltage divider circuit consisting of resistors R3 and R4 in order to sample the voltage between the live and neutral lines. The voltage signal is amplified by the current detection amplifier U3 to finally obtain the real-time overcurrent threshold.

[0028] Furthermore, the current sensing amplifier U3 is composed of an INA240 chip and its peripheral circuitry.

[0029] In this embodiment, the current sense amplifier U3 is preferably composed of an INA240 chip and its peripheral circuitry. The INA240 chip is a voltage-output current sense amplifier that can be used to detect the voltage drop across the shunt resistor (i.e., resistor R4) within a voltage range of -4V to 80V independent of the power supply voltage, thereby accurately measuring the current without causing large transients or corresponding recovery ripples in the output voltage. More importantly, various gain specifications are available, such as the INA240A2 model with a gain of 50V / V, allowing for coarse adjustment of the real-time overcurrent threshold. Simultaneously, the real-time overcurrent threshold can be finely adjusted by changing the reference voltage of the INA240 chip.

[0030] Taking the INA240A2 model as an example, resistors R3 and R4 are shunt resistors, providing input current to the chip; the chip's REF1 pin is connected to 5V, and the chip's REF2 pin is grounded. The chip is set to bidirectional current measurement mode (it has both unidirectional and bidirectional current detection modes; unidirectional is suitable for DC systems, and bidirectional is suitable for AC systems). The formula for calculating the output reference voltage is:

[0031] Output reference voltage = (V_REF1 + V_REF2) / 2;

[0032] A 100nF capacitor is connected in parallel between the chip's VS pin and GND pin as a power supply decoupling capacitor. MAIN_OUT is the voltage output by the chip (i.e., the real-time overcurrent threshold), and the formula for calculating this voltage is:

[0033] Output voltage = Output reference voltage + 50 (gain) * I_Shunt resistor * R_Shunt resistor;

[0034] Taking the AC system as an example, since the REF1 pin and REF2 pin of the chip are connected to 5V and ground respectively, the output reference voltage is 2.5V. In the voltage divider circuit, the current is 0.1mA at 220V, the voltage on the shunt resistor is 10mV, and the output voltage after passing through the chip is 2.5V±0.5V.

[0035] Furthermore, the current transformer module 1 includes a current transformer U1 and a sampling resistor R1; the live wire passes through the busbar through hole of the current transformer U1, one end of the secondary winding terminal of the current transformer U1 is grounded, and the other end of the secondary winding terminal of the current transformer U1 is used to output a real-time voltage signal; the sampling resistor R1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

[0036] In this embodiment, the current transformer module 1, in order to convert the live wire current signal into a real-time voltage signal for detection through electromagnetic induction, is preferably composed of a current transformer U1 and a sampling resistor R1. For example, the current transformer U1 is a ZMCT103C model, with a rated input current of 5A and a transformation ratio of 1000:1. The live wire passes through the current transformer U1 as the live wire current input. The value of the sampling resistor R1 can be freely set according to the required sampling voltage. Its calculation formula is as follows:

[0037] Sampling resistor = 1000 / input current * sampling voltage;

[0038] Once the sampling voltage is set, the AC current will cause the real-time voltage signal to fluctuate within a certain range. Only when there is an overcurrent will the real-time voltage signal change abruptly, thus identifying the live wire overcurrent.

[0039] Furthermore, the current transformer module 1 also includes a bidirectional TVS diode D1; the bidirectional TVS diode D1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

[0040] In this embodiment, a bidirectional TVS diode D1 is added to the current transformer module 1 as circuit protection to prevent voltage transients from affecting the detection circuit.

[0041] Other configurations and operations of an overcurrent detection circuit suitable for high-current power supplies according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0042] In this specification, the terms "embodiment," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An overcurrent detection circuit suitable for high-current power supplies, characterized in that: It includes a current transformer module and an overcurrent threshold sampling module; the current transformer module is electrically connected to the live wire, and the overcurrent threshold sampling module is electrically connected to both the live wire and the neutral wire. The current transformer module is used to convert the current signal of the live wire into a real-time voltage signal through electromagnetic induction. The overcurrent threshold sampling module is used to sample the voltage signal between the live wire and the neutral wire to generate a real-time overcurrent threshold.

2. The overcurrent detection circuit suitable for high-current power supplies according to claim 1, characterized in that: The overcurrent threshold sampling module includes resistor R3, resistor R4, and current detection amplifier U3; one end of resistor R3 is electrically connected to the live wire, the other end of resistor R3 and one end of resistor R4 are both electrically connected to the positive input terminal of current detection amplifier U3, the other end of resistor R4 and the neutral wire are both electrically connected to the negative input terminal of current detection amplifier U3, and the output terminal of current detection amplifier U3 is used to output the real-time overcurrent threshold.

3. The overcurrent detection circuit suitable for high-current power supplies according to claim 2, characterized in that: The current sensing amplifier U3 is composed of an INA240 chip and its peripheral circuitry.

4. The overcurrent detection circuit suitable for high-current power supplies according to claim 1, characterized in that: The current transformer module includes a current transformer U1 and a sampling resistor R1; the live wire passes through the busbar through hole of the current transformer U1, one end of the secondary winding terminal of the current transformer U1 is grounded, and the other end of the secondary winding terminal of the current transformer U1 is used to output the real-time voltage signal; the sampling resistor R1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

5. An overcurrent detection circuit suitable for high-current power supplies according to claim 4, characterized in that: The current transformer module also includes a bidirectional TVS diode D1; the bidirectional TVS diode D1 is connected in parallel between one end and the other end of the secondary winding terminal of the current transformer U1.

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