Constant current protection circuit and system

Abstract

The invention discloses a constant current protection circuit and system, and belongs to the technical field of electronics, the constant current protection circuit comprises a constant current sub-circuit, an input sampling sub-circuit, a power supply sub-circuit, a control sub-circuit and a power transmission sub-circuit; wherein the constant-current sub-circuit is used for detecting a sampling voltage output by the input sampling sub-circuit, setting a constant-current voltage threshold through the power supply sub-circuit, and comparing the sampling voltage with the constant-current voltage threshold: when the sampling voltage exceeds the constant-current voltage threshold, the constant-current sub-circuit sends a constant-current protection control signal to the control sub-circuit; therefore, the power transmission sub-circuit is controlled to carry out constant-current protection until the sampling voltage is within the constant-current voltage threshold value. According to the method disclosed by the invention, the constant-current sub-circuit is combined with the control sub-circuit located at the front-stage input end, so that the defect that the circuit structure is too complex when the constant-current protection circuit is placed at the rear end is avoided, and the circuit structure complexity of the constant-current protection circuit is reduced.

Description

Technical Field

[0001] This invention belongs to the field of electronic technology, and in particular relates to a constant current protection circuit and system. Background Technology

[0002] Currently, modular power supplies mainly consist of an input circuit, a power transmission circuit, an output circuit, an input control circuit, an output feedback circuit, and a constant current circuit. During normal operation, the constant current circuit is not triggered, and the modular power supply operates in constant voltage mode. When the output load current continuously increases and reaches the constant current operating point, the constant current circuit is triggered, processing the output operating state and feeding it back to the input control circuit. This causes the control circuit to adjust the operating mode and power transmission state, and the modular power supply enters constant current mode. In this mode, the output current remains constant while the output voltage decreases with load changes, thus achieving constant current protection. This is crucial for improving power supply reliability and effectively protects the modular power supply and load equipment from overcurrent damage.

[0003] However, existing constant current protection circuits generally employ a scheme where a high-precision, low-temperature-drift power resistor is connected in series on the output ground line of the subsequent stage. When the output load current changes, the voltage across the power resistor changes accordingly. The constant current function is then achieved by acquiring, processing, and feeding this voltage back to the control circuit. This traditional architecture is overly complex for systems where the control circuit is located at the front end and the constant current function needs to be implemented at the rear end. It requires an additional independent power supply system, increasing design difficulty and production costs, and hindering the development of modular power supplies towards miniaturization and high integration. Therefore, the current implementation of constant current protection in modular power supplies suffers from a complex circuit structure. Summary of the Invention

[0004] The present invention aims to provide a constant current protection circuit and system to solve the above-mentioned technical problems and reduce the circuit structure complexity of the constant current protection circuit.

[0005] To address the aforementioned technical problems, the first aspect of the present invention provides a constant current protection circuit, comprising a constant current sub-circuit, an input sampling sub-circuit, a power supply circuit, a control sub-circuit, and a power transmission sub-circuit; wherein: The first input terminal of the constant current sub-circuit is electrically connected to the output terminal of the input sampling sub-circuit; The second input terminal of the constant current sub-circuit is electrically connected to the output terminal of the power supply circuit; The output terminal of the constant current sub-circuit is electrically connected to the first input terminal of the control sub-circuit. The first output terminal of the control sub-circuit is electrically connected to the first input terminal of the power transmission sub-circuit. The control sub-circuit is electrically connected to the power supply circuit, and the power transmission sub-circuit is electrically connected to the power supply circuit; The constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and to set a constant current voltage threshold through the power supply circuit, comparing the sampling voltage with the constant current voltage threshold. When the sampled voltage exceeds the constant current voltage threshold, the constant current sub-circuit sends a constant current protection control signal to the control sub-circuit to control the power transmission sub-circuit to perform constant current protection until the sampled voltage is within the constant current voltage threshold.

[0006] In the above scheme, the constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit and sets a constant current voltage threshold through the power supply circuit. When the sampling voltage output by the input sampling sub-circuit exceeds the constant current voltage threshold, a constant current protection control signal is sent to the control sub-circuit to control the power transmission sub-circuit for constant current protection. By detecting the sampling voltage at the input terminal and comparing it with the set constant current voltage threshold, the power transmission process can be controlled, thereby achieving constant current protection for the output current. This scheme combines the constant current sub-circuit with the control sub-circuit located at the front-end input, avoiding the drawback of overly complex circuit structure when the constant current protection circuit is placed at the back end, and reducing the circuit structure complexity of the constant current protection circuit. At the same time, by electrically connecting the constant current sub-circuit and the power transmission sub-circuit to the same power supply circuit, the power supply interface of the circuit can be unified, eliminating the need for an additional power supply system, thereby reducing the circuit structure complexity of the constant current protection circuit.

[0007] Further, the constant current sub-circuit includes an NMOS transistor, an operational amplifier, a diode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor; the third input terminal of the constant current sub-circuit is electrically connected to the second output terminal of the control sub-circuit; wherein: The source of the NMOS transistor serves as the first input terminal of the constant current sub-circuit, and the drain of the NMOS transistor is electrically connected to one end of the first resistor; the gate of the NMOS transistor serves as the third input terminal of the constant current sub-circuit, and is electrically connected to one end of the second resistor and one end of the third resistor. The non-inverting input terminal of the operational amplifier is electrically connected to the other end of the third resistor, one end of the fourth resistor, one end of the sixth resistor, and one end of the third capacitor; the inverting input terminal of the operational amplifier is electrically connected to the other end of the first resistor, the other end of the second resistor, one end of the fifth resistor, one end of the second capacitor, and one end of the seventh resistor; the output terminal of the operational amplifier is electrically connected to the negative terminal of the diode and one end of the fourth capacitor; the positive power input terminal of the operational amplifier serves as the second input terminal of the constant current sub-circuit, is electrically connected to one end of the first capacitor, and the other end of the fourth resistor; the negative power input terminal of the operational amplifier is grounded. The positive terminal of the diode serves as the second input terminal of the constant current sub-circuit; the other end of the fifth resistor is grounded; the other end of the sixth resistor is grounded; the other end of the seventh resistor is electrically connected to the other end of the fourth capacitor; the other end of the first capacitor is grounded; the other end of the second capacitor is grounded; and the other end of the third capacitor is grounded.

[0008] In the above scheme, the sampling voltage input through the first input terminal of the constant current sub-circuit can be rectified and filtered internally by the constant current sub-circuit and then connected to the inverting input terminal of the operational amplifier. Specifically, the NMOS transistor acts as a rectifier and anti-reverse current transistor, the circuit composed of the first resistor, the fifth resistor, and the second capacitor acts as a filter, and the fourth resistor and the sixth resistor form a voltage divider circuit to convert the standard voltage provided by the electronic circuit into a constant current voltage threshold, thereby realizing the voltage threshold comparison process. The components required for this constant current sub-circuit have a simple structure, and the circuit transmission is closely integrated with the input terminal of the previous stage, reducing the circuit structure complexity of the constant current protection circuit.

[0009] Furthermore, it also includes: an input sub-circuit and an output sub-circuit; wherein: the first output terminal of the input sub-circuit is electrically connected to the second input terminal of the power transmission sub-circuit; the second output terminal of the input sub-circuit is electrically connected to the input terminal of the input sampling sub-circuit; the input terminal of the output sub-circuit is electrically connected to the output terminal of the power transmission sub-circuit; wherein, the input sub-circuit is used to transmit electrical energy to the output sub-circuit through the power transmission sub-circuit and to provide sampling current for the input sampling sub-circuit.

[0010] Further, the constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and to set a constant current voltage threshold through the power supply circuit, and to compare the sampling voltage with the constant current voltage threshold, including: the input sampling sub-circuit samples the current output by the input sub-circuit to obtain the sampling current, and converts the sampling current into the sampling voltage to output the sampling voltage to the constant current sub-circuit; the power supply circuit outputs a standard voltage to the constant current sub-circuit so that the constant current sub-circuit sets the constant current voltage threshold through voltage division; and the sampling voltage is compared with the constant current voltage threshold.

[0011] It should be noted that the source of the NMOS transistor serves as the first input terminal of the constant current sub-circuit and is electrically connected to the output terminal of the input sampling sub-circuit. When the input sampling sub-circuit samples the current of the input sub-circuit and converts it into a sampling voltage, the sampling voltage flows in through the source of the NMOS transistor, flows out through the drain, and is then rectified and filtered to form the voltage to be measured, which is then fed into the inverting input terminal of the operational amplifier. The positive power input terminal of the operational amplifier serves as the second input terminal of the constant current sub-circuit. In addition to providing a standard voltage, it is also connected to the non-inverting input terminal of the operational amplifier through a voltage divider network formed by the fourth and sixth resistors to provide a constant current voltage threshold. The operational amplifier acts as a comparator, comparing the processed sampled voltage with the constant current voltage threshold. When the sampled voltage exceeds the constant current voltage threshold, i.e., the inverting input of the operational amplifier is greater than the non-inverting input, the output of the operational amplifier will turn low, turning on the diode connected to it. This sends a constant current protection control signal to the first input of the control sub-circuit through the output of the constant current sub-circuit, i.e., pulling down its voltage, so that the control sub-circuit controls the power transmission sub-circuit to change its operating state to complete the constant current protection.

[0012] In the above scheme, the architecture of the constant current sub-circuit is designed for the front-end input of the module power supply. Its signal transmission process with the control sub-circuit and input sampling sub-circuit avoids the drawbacks of overly complex circuitry and slow signal transmission when the constant current protection circuit is placed at the back end, thus reducing the circuit complexity of the constant current protection circuit. The power supply circuit serves simultaneously as the positive power input of the operational amplifier and the standard power input of the entire constant current sub-circuit, as well as the power input of the control sub-circuit and the power transmission sub-circuit. This structural design allows it to operate directly through a unified power input, eliminating the need for an additional independent power supply for the constant current protection circuit and further simplifying the circuit structure.

[0013] Furthermore, the power supply circuit outputs a standard voltage to the constant current sub-circuit so that the constant current sub-circuit sets a constant current voltage threshold through voltage division, including: the power supply circuit outputs a standard voltage to the constant current sub-circuit; the second input terminal of the constant current sub-circuit receives the standard voltage, uses the standard voltage as the positive power input of the operational amplifier, and sets the constant current voltage threshold through voltage division between the fourth resistor and the sixth resistor.

[0014] It should be noted that the setting of the constant current voltage threshold by the voltage divider between the fourth resistor and the sixth resistor specifically involves: in, R6 is the constant current voltage threshold, R4 is the sixth resistor, and VCC is the standard voltage received at the second input terminal of the constant current sub-circuit.

[0015] In the above scheme, the constant current voltage threshold is set based on the voltage divider principle and determined by the ratio of the fourth and sixth resistors, eliminating the need for an additional reference voltage source and simplifying circuit design. Comparing the rectified and filtered sampled voltage with this threshold accurately determines whether constant current protection is required.

[0016] Furthermore, the second and third resistors are adjustable resistors used to adjust the output constant current value required for constant current protection; wherein: when the resistance value of the second resistor increases, the output constant current value decreases relatively; when the resistance value of the third resistor increases, the output constant current value increases relatively.

[0017] In the above scheme, the second resistor is connected to the inverting input of the operational amplifier, and the third resistor is connected to the non-inverting input. When the actual output constant current value is greater than the required design value, the constant current circuit has not yet entered the constant current protection state. This indicates that the voltage at the inverting input is still lower than the threshold voltage at the non-inverting input. In this case, the resistance of the second resistor needs to be increased to raise the voltage at the inverting input, causing the operational amplifier to output a low level earlier, allowing the module to enter the constant current mode sooner, thereby reducing the output constant current value. Conversely, when the actual output constant current value is less than the required design value, it indicates that the voltage at the inverting input has exceeded the threshold voltage at the non-inverting input before the designed output current is reached. In this case, the resistance of the third resistor needs to be increased to raise the voltage at the non-inverting input, delaying the timing of the operational amplifier outputting a low level, allowing the module to delay entering the constant current protection mode, thereby increasing the output constant current value. This adjustment mechanism allows the constant current protection circuit to accurately match the design requirements without replacing core components, improving the flexibility and applicability of the circuit and simplifying the circuit structure.

[0018] Furthermore, after the constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit and sets a constant current voltage threshold by the power supply circuit, and compares the sampling voltage with the constant current voltage threshold, the method further includes: when the sampling voltage is within the constant current voltage threshold, the constant current sub-circuit sends a normal operation signal to the control sub-circuit to control the power transmission sub-circuit to keep the output voltage constant.

[0019] In the above scheme, when the sampling voltage is lower than the constant current voltage threshold, the operational amplifier output remains high, causing the diode to be in the cutoff state. This keeps the output of the constant current sub-circuit high, sending a normal operation signal to the control sub-circuit to maintain its normal operation and ensuring the power transmission sub-circuit maintains a constant voltage output. This design achieves both constant voltage and constant current protection functions, ensuring the module power supply provides a stable output voltage under normal load conditions. Constant current protection is only activated in cases of abnormal changes in input current, thus guaranteeing the module power supply's performance while reducing the complexity of the constant current protection circuit.

[0020] Furthermore, it also includes an output sampling feedback sub-circuit; wherein: the input terminal of the output sampling feedback sub-circuit is electrically connected to the output terminal of the output sub-circuit; the output terminal of the output sampling feedback sub-circuit is electrically connected to the second input terminal of the control sub-circuit; the output sampling feedback sub-circuit is used to sample the voltage output by the output sub-circuit to obtain a feedback compensation voltage, and output the feedback compensation voltage to the control sub-circuit to control the power transmission sub-circuit to perform constant current protection.

[0021] In the above scheme, the output sampling feedback sub-circuit and the constant current sub-circuit can jointly function as the error compensation terminal of the control sub-circuit. That is, the first input terminal and the second input terminal of the control sub-circuit are electrically connected, serving as the error compensation terminal. Under normal operating conditions, the diode is in the off state, not affecting the control of the control sub-circuit by the output sampling feedback sub-circuit. At this time, the output sampling feedback sub-circuit dominates the control process, maintaining the output voltage stable at the set value by monitoring the output voltage and generating a corresponding feedback compensation voltage. When entering constant current protection mode, the constant current sub-circuit outputs a low voltage through the output terminal of the operational amplifier, overriding the control function of the output sampling feedback sub-circuit, thus switching the control sub-circuit from constant voltage mode to constant current mode. Since the constant current sub-circuit and the output sampling feedback sub-circuit share the error compensation terminal of the control sub-circuit, no additional control circuitry is required. This design retains the excellent voltage regulation characteristics of traditional switching power supplies, while simultaneously achieving a simplified constant current protection circuit through pre-stage current detection.

[0022] Furthermore, the output of the control sub-circuit generates a periodic square wave signal to control the conduction time of the power transmission sub-circuit; wherein: when the constant current sub-circuit issues a constant current protection control signal, the control sub-circuit controls the power transmission sub-circuit to reduce the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to perform constant current protection; when the constant current sub-circuit issues a normal operation signal, the control sub-circuit controls the power transmission sub-circuit not to change the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to keep the output voltage constant.

[0023] In the above scheme, constant current protection is achieved by sampling the input current of the front stage and controlling the conduction time of the periodic square wave signal. This avoids the complex structure of connecting a high-precision power resistor in series on the output ground line in the traditional scheme, and significantly simplifies the circuit design.

[0024] A second aspect of the present invention provides a constant current protection system, comprising a DC input power supply, a load, and a constant current protection circuit as described in any embodiment of the first aspect of the present invention; wherein: the DC input power supply is electrically connected to the input sub-circuit of the constant current protection circuit; and the load is electrically connected to the output sub-circuit of the constant current protection circuit.

[0025] In the above scheme, the external DC input power supply provides power to the power transmission sub-circuit through the input sub-circuit, so that the input sub-circuit provides sampling current to the input sampling sub-circuit; the input sampling sub-circuit samples the current of the corresponding input sub-circuit at the input terminal of the previous stage, converts it into a sampling voltage and outputs it to the constant current sub-circuit. The constant current sub-circuit utilizes the standard voltage provided by the power supply circuit to set a constant current voltage threshold through voltage division. It then compares the sampled voltage with this threshold. When the sampled voltage does not exceed the threshold, it indicates that the downstream load current is normal. The constant current sub-circuit does not interfere with the control process and sends a normal operation signal. The control sub-circuit maintains the normal conduction time of the square wave signal of the power transmission sub-circuit based on the voltage of the output sampling feedback sub-circuit, and the system maintains a constant voltage output. When the sampled voltage exceeds the threshold, it indicates that the downstream load is overcurrent. The constant current sub-circuit sends a constant current protection control signal to the control sub-circuit, lowering the voltage at the first input terminal of the control sub-circuit to send the constant current protection signal. The control sub-circuit then reduces the conduction time of the square wave signal of the power transmission sub-circuit, reducing the energy transfer of the power transmission sub-circuit, causing the output voltage to drop while the output current remains constant, thus achieving constant current protection. This system avoids the complex structure of connecting a high-precision power resistor in series on the output ground line by detecting the corresponding current at the input terminal of the front-end stage instead of directly detecting the output current. The constant current sub-circuit does not require an independent power supply and can operate directly using the existing power supply of the system. It is particularly suitable for modular power supply designs with multiple independent outputs and each requiring a different constant current value. Each output only needs to be configured with a simple constant current sub-circuit, without the need to add complex current detection and dedicated control circuits for each output, which significantly simplifies the overall circuit structure and reduces cost and size. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a constant current protection circuit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a constant current sub-circuit provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the architecture of a constant current protection system provided in an embodiment of the present invention; Wherein: 100, constant current sub-circuit; 200, input sampling sub-circuit; 300, power supply circuit; 400, control sub-circuit; 500, power transmission sub-circuit; 600, input sub-circuit; 700, output sub-circuit; 800, output sampling feedback sub-circuit; 900, DC input power supply; 1000, load. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0028] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0029] like Figure 1 The diagram shown is a schematic representation of a constant current protection circuit according to a first aspect of the present invention. The circuit includes a constant current sub-circuit 100, an input sampling sub-circuit 200, a power supply circuit 300, a control sub-circuit 400, and a power transmission sub-circuit 500; wherein: The first input terminal of the constant current sub-circuit 100 is electrically connected to the output terminal of the input sampling sub-circuit 200; The second input terminal of the constant current sub-circuit 100 is electrically connected to the output terminal of the power supply circuit 300; The output terminal of the constant current sub-circuit 100 is electrically connected to the first input terminal of the control sub-circuit 400; The first output terminal of the control sub-circuit 400 is electrically connected to the first input terminal of the power transmission sub-circuit 500. The control sub-circuit 400 is electrically connected to the power supply circuit 300, and the power transmission sub-circuit 500 is electrically connected to the power supply circuit 300; The constant current sub-circuit 100 is used to detect the sampling voltage output by the input sampling sub-circuit 200, and sets a constant current voltage threshold through the power supply circuit 300, comparing the sampling voltage with the constant current voltage threshold. When the sampling voltage exceeds the constant current voltage threshold, the constant current sub-circuit 100 sends a constant current protection control signal to the control sub-circuit 400, so that it controls the power transmission sub-circuit 500 to perform constant current protection until the sampling voltage is within the constant current voltage threshold.

[0030] In this embodiment, the constant current sub-circuit 100 is used to detect the sampling voltage output by the input sampling sub-circuit 200, and sets a constant current voltage threshold through the power supply circuit 300. When the sampling voltage output by the input sampling sub-circuit exceeds the constant current voltage threshold, a constant current protection control signal is sent to the control sub-circuit 400 to control the power transmission sub-circuit 500 for constant current protection. By detecting the sampling voltage at the input terminal and comparing it with the set constant current voltage threshold, the power transmission process can be controlled, thereby achieving constant current protection for the output current. The circuit of this embodiment combines the constant current sub-circuit with the control sub-circuit located at the front-end input terminal, avoiding the disadvantage of overly complex circuit structure when the constant current protection circuit is placed at the back end, and reducing the circuit structure complexity of the constant current protection circuit. At the same time, by electrically connecting the constant current sub-circuit and the power transmission sub-circuit to the same power supply circuit, the power supply interface of the circuit can be unified, eliminating the need for an additional power supply system, thereby reducing the circuit structure complexity of the constant current protection circuit.

[0031] Furthermore, such as Figure 2 The diagram shown is a schematic representation of a constant current sub-circuit provided in an embodiment of the present invention. The constant current sub-circuit includes an NMOS transistor T1, an operational amplifier IC1, a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4. The third input terminal of the constant current sub-circuit is electrically connected to the second output terminal of the control sub-circuit. The source of the NMOS transistor T1 serves as the first input terminal of the constant current sub-circuit, and the drain of the NMOS transistor T1 is electrically connected to one end of the first resistor R1; the gate of the NMOS transistor T1 serves as the third input terminal of the constant current sub-circuit, and is electrically connected to one end of the second resistor R2 and one end of the third resistor R3. The non-inverting input terminal of operational amplifier IC1 is electrically connected to the other end of the third resistor R3, one end of the fourth resistor R4, one end of the sixth resistor R6, and one end of the third capacitor C3; the inverting input terminal of operational amplifier IC1 is electrically connected to the other end of the first resistor, the other end of the second resistor R2, one end of the fifth resistor R5, one end of the second capacitor C2, and one end of the seventh resistor R7; the output terminal of operational amplifier IC1 is electrically connected to the negative terminal of diode D1 and one end of the fourth capacitor C4; the positive power input terminal of operational amplifier IC1 serves as the second input terminal of the constant current sub-circuit, is electrically connected to one end of the first capacitor C1, and the other end of the fourth resistor R4; the negative power input terminal of operational amplifier IC1 is grounded. The positive terminal of diode D1 serves as the second input terminal of the constant current sub-circuit; the other end of the fifth resistor R5 is grounded; the other end of the sixth resistor R6 is grounded; the other end of the seventh resistor R7 is electrically connected to the other end of the fourth capacitor C4; the other end of the first capacitor C1 is grounded; the other end of the second capacitor C2 is grounded; and the other end of the third capacitor C3 is grounded. Wherein, IN is the first input terminal of the constant current sub-circuit 100, which is electrically connected to the output terminal of the input sampling sub-circuit 200; VCC is the second input terminal of the constant current sub-circuit 100, which is electrically connected to the output terminal of the power supply circuit 300; OUT is the third input terminal of the constant current sub-circuit 100, which is electrically connected to the second output terminal of the control sub-circuit and serves as the control port for the control sub-circuit to control the constant current sub-circuit; COMP is the output terminal of the constant current sub-circuit 100, which is electrically connected to the first input terminal of the control sub-circuit 400.

[0032] In this embodiment, the sampling voltage input through the first input terminal of the constant current sub-circuit can be rectified and filtered internally by the constant current sub-circuit and then connected to the inverting input terminal of the operational amplifier. Specifically, the NMOS transistor acts as a rectifier and anti-reverse current transistor, the circuit composed of the first resistor, the fifth resistor, and the second capacitor acts as a filter, and the fourth resistor and the sixth resistor form a voltage divider circuit to convert the standard voltage input from the second input terminal of the power supply circuit into a constant current voltage threshold, thereby realizing the voltage threshold comparison process. The components required for this constant current sub-circuit have a simple structure, and the circuit transmission is closely integrated with the input terminal of the previous stage, reducing the circuit structure complexity of the constant current protection circuit.

[0033] Furthermore, it also includes: an input sub-circuit and an output sub-circuit; wherein: the first output terminal of the input sub-circuit is electrically connected to the second input terminal of the power transmission sub-circuit; the second output terminal of the input sub-circuit is electrically connected to the input terminal of the input sampling sub-circuit; the input terminal of the output sub-circuit is electrically connected to the output terminal of the power transmission sub-circuit; wherein, the input sub-circuit is used to transmit electrical energy to the output sub-circuit through the power transmission sub-circuit and to provide sampling current for the input sampling sub-circuit.

[0034] Further, the constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and to set a constant current voltage threshold through the power supply circuit, and to compare the sampling voltage with the constant current voltage threshold, including: the input sampling sub-circuit samples the current output by the input sub-circuit to obtain the sampling current, and converts the sampling current into the sampling voltage to output the sampling voltage to the constant current sub-circuit; the power supply circuit outputs a standard voltage to the constant current sub-circuit so that the constant current sub-circuit sets the constant current voltage threshold through voltage division; and the sampling voltage is compared with the constant current voltage threshold.

[0035] It should be noted that the source of the NMOS transistor T1 serves as the first input terminal of the constant current sub-circuit 100 and is electrically connected to the output terminal of the input sampling sub-circuit 200. When the input sampling sub-circuit 200 samples the current of the input sub-circuit and converts it into a sampling voltage, the sampling voltage flows in through the source (IN terminal) of the NMOS transistor T1, flows out through the drain, and is then rectified and filtered to form the voltage to be measured, which is then fed into the inverting input terminal of the operational amplifier IC1. The positive power input terminal of the operational amplifier IC1 serves as the second input terminal (VCC terminal) of the constant current sub-circuit. In addition to providing a standard voltage, it also forms a voltage divider network through the fourth resistor R4 and the sixth resistor R6, which is input to the non-inverting input terminal of the operational amplifier IC1 to provide a constant current voltage threshold. Operational amplifier IC1 acts as a comparator, comparing the processed sampled voltage with the constant current voltage threshold. When the sampled voltage exceeds the constant current voltage threshold, i.e., the inverting input of operational amplifier IC1 is greater than the non-inverting input, the output of operational amplifier IC1 will turn low, turning on the diode D1 connected to it. This sends a constant current protection control signal to the first input of control sub-circuit 400 through the output (COMP terminal) of constant current sub-circuit 100, i.e., pulling down its voltage, so that control sub-circuit 400 controls power transmission sub-circuit 500 to change its operating state to complete constant current protection.

[0036] In this embodiment, the architecture of the constant current sub-circuit is designed for the front-end input of the module power supply. Its signal transmission process with the control sub-circuit and input sampling sub-circuit avoids the drawbacks of overly complex circuitry and slow signal transmission when the constant current protection circuit is placed at the back end, thus reducing the complexity of the constant current protection circuit. The power supply circuit serves simultaneously as the positive power input of the operational amplifier and the standard power input for the entire constant current sub-circuit, as well as the power input for the control sub-circuit and the power transmission sub-circuit. This structural design allows it to operate directly through a unified power input, eliminating the need for an additional independent power supply for the constant current protection circuit and further simplifying the circuit structure.

[0037] Furthermore, the power supply circuit outputs a standard voltage to the constant current sub-circuit so that the constant current sub-circuit sets a constant current voltage threshold through voltage division, including: the power supply circuit outputs a standard voltage to the constant current sub-circuit; the second input terminal of the constant current sub-circuit receives the standard voltage, uses the standard voltage as the positive power input of the operational amplifier, and sets the constant current voltage threshold through voltage division between the fourth resistor and the sixth resistor.

[0038] It should be noted that the setting of the constant current voltage threshold by the voltage divider between the fourth resistor and the sixth resistor specifically involves: in, R6 is the constant current voltage threshold, R4 is the sixth resistor, and VCC is the standard voltage received at the second input terminal of the constant current sub-circuit.

[0039] In this embodiment, the constant current voltage threshold is set based on the voltage divider principle and determined by the ratio of the fourth and sixth resistors, eliminating the need for an additional reference voltage source and simplifying circuit design. The sampled voltage after rectification and filtering is compared with this threshold to accurately determine whether constant current protection is required.

[0040] Furthermore, the second resistor R2 and the third resistor R3 are adjustable resistors used to adjust the output constant current value required for constant current protection; wherein: when the resistance value of the second resistor R2 increases, the output constant current value decreases relatively; when the resistance value of the third resistor R3 increases, the output constant current value increases relatively.

[0041] In this embodiment, the second resistor R2 is connected to the inverting input of the operational amplifier, and the third resistor R3 is connected to the non-inverting input. When the actual output constant current value is greater than the required design value, the constant current circuit has not yet entered the constant current protection state, indicating that the voltage at the inverting input is still lower than the threshold voltage at the non-inverting input. In this case, the resistance of the second resistor R2 needs to be increased to raise the voltage at the inverting input, causing the operational amplifier to output a low level earlier, allowing the module to enter the constant current mode sooner, thereby reducing the output constant current value. Conversely, when the actual output constant current value is less than the required design value, it indicates that the voltage at the inverting input has exceeded the threshold voltage at the non-inverting input before the designed output current is reached. In this case, the resistance of the third resistor R3 needs to be increased to raise the voltage at the non-inverting input, delaying the timing of the operational amplifier IC1 outputting a low level, allowing the module to delay entering the constant current protection mode, thereby increasing the output constant current value. This adjustment mechanism allows the constant current protection circuit to accurately match the design requirements without replacing core components, improving the circuit's flexibility and applicability, and simplifying the circuit structure.

[0042] Furthermore, after the constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit and sets a constant current voltage threshold by the power supply circuit, and compares the sampling voltage with the constant current voltage threshold, the method further includes: when the sampling voltage is within the constant current voltage threshold, the constant current sub-circuit sends a normal operation signal to the control sub-circuit to control the power transmission sub-circuit to keep the output voltage constant.

[0043] In this embodiment, when the sampling voltage is lower than the constant current voltage threshold, the operational amplifier output remains high, causing the diode to be in the off state. This keeps the output of the constant current sub-circuit high, sending a normal operation signal to the control sub-circuit to maintain its normal operation and ensuring the power transmission sub-circuit maintains a constant voltage output. This design achieves both constant voltage and constant current protection functions, ensuring the module power supply provides a stable output voltage under normal load conditions. Constant current protection is only activated in cases of abnormal changes in input current, thus guaranteeing the module power supply's performance while reducing the complexity of the constant current protection circuit.

[0044] Furthermore, it also includes an output sampling feedback sub-circuit; wherein: the input terminal of the output sampling feedback sub-circuit is electrically connected to the output terminal of the output sub-circuit; the output terminal of the output sampling feedback sub-circuit is electrically connected to the second input terminal of the control sub-circuit; the output sampling feedback sub-circuit is used to sample the voltage output by the output sub-circuit to obtain a feedback compensation voltage, and output the feedback compensation voltage to the control sub-circuit to control the power transmission sub-circuit to perform constant current protection.

[0045] In one embodiment, the output sampling feedback sub-circuit can work together with the constant current sub-circuit on the error compensation terminal (COMP terminal) of the control sub-circuit. That is, the first input terminal and the second input terminal of the control sub-circuit are electrically connected, serving as the error compensation terminal. Under normal operating conditions, the diode is in the off state, not affecting the control of the control sub-circuit by the output sampling feedback sub-circuit. At this time, the output sampling feedback sub-circuit dominates the control process, maintaining the output voltage stable at the set value by monitoring the output voltage and generating a corresponding feedback compensation voltage. When entering constant current protection mode, the constant current sub-circuit outputs a low voltage through the output terminal of the operational amplifier, overriding the control function of the output sampling feedback sub-circuit, thus switching the control sub-circuit from constant voltage mode to constant current mode. Since the constant current sub-circuit and the output sampling feedback sub-circuit share the error compensation terminal of the control sub-circuit, no additional control lines are required. This design retains the excellent voltage regulation characteristics of traditional switching power supplies, while achieving a simplified constant current protection circuit through front-end current detection.

[0046] Furthermore, the output of the control sub-circuit generates a periodic square wave signal to control the conduction time of the power transmission sub-circuit; wherein: when the constant current sub-circuit issues a constant current protection control signal, the control sub-circuit controls the power transmission sub-circuit to reduce the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to perform constant current protection; when the constant current sub-circuit issues a normal operation signal, the control sub-circuit controls the power transmission sub-circuit not to change the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to keep the output voltage constant.

[0047] In this embodiment, constant current protection is achieved by sampling the input current of the pre-amplifier and controlling the conduction time of the periodic square wave signal. This avoids the complex structure of connecting a high-precision power resistor in series on the output ground line in traditional solutions, and significantly simplifies the circuit design.

[0048] like Figure 3 As shown, a second aspect of the present invention provides a constant current protection system, which includes a DC input power supply, a load, and a constant current protection circuit as described in any embodiment of the first aspect of the present invention; wherein: the DC input power supply is electrically connected to the input sub-circuit of the constant current protection circuit; and the load is electrically connected to the output sub-circuit of the constant current protection circuit.

[0049] In this embodiment, an external DC input power supply provides power to the power transmission sub-circuit through the input sub-circuit, enabling the input sub-circuit to provide sampling current to the input sampling sub-circuit; the input sampling sub-circuit samples the current of the corresponding input sub-circuit at the input terminal of the previous stage, converts it into a sampling voltage, and outputs it to the constant current sub-circuit. The constant current sub-circuit utilizes the standard voltage provided by the power supply circuit to set a constant current voltage threshold through voltage division. It then compares the sampled voltage with this threshold. When the sampled voltage does not exceed the threshold, it indicates that the downstream load current is normal. The constant current sub-circuit does not interfere with the control process and sends a normal operation signal. The control sub-circuit maintains the normal conduction time of the square wave signal of the power transmission sub-circuit based on the voltage of the output sampling feedback sub-circuit, and the system maintains a constant voltage output. When the sampled voltage exceeds the threshold, it indicates that the downstream load is overcurrent. The constant current sub-circuit sends a constant current protection control signal to the control sub-circuit, lowering the voltage at the first input terminal of the control sub-circuit to send the constant current protection signal. The control sub-circuit then reduces the conduction time of the square wave signal of the power transmission sub-circuit, reducing the energy transfer of the power transmission sub-circuit, causing the output voltage to drop while the output current remains constant, thus achieving constant current protection. This system avoids the complex structure of connecting a high-precision power resistor in series on the output ground line by detecting the corresponding current at the input terminal of the front-end stage instead of directly detecting the output current. The constant current sub-circuit does not require an independent power supply and can operate directly using the existing power supply of the system. It is particularly suitable for modular power supply designs with multiple independent outputs and each requiring a different constant current value. Each output only needs to be configured with a simple constant current sub-circuit, without the need to add complex current detection and dedicated control circuits for each output, which significantly simplifies the overall circuit structure and reduces cost and size.

[0050] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A constant current protection circuit, characterized in that, It includes a constant current sub-circuit, an input sampling sub-circuit, a power supply circuit, a control sub-circuit, and a power transfer sub-circuit; among which: The first input terminal of the constant current sub-circuit is electrically connected to the output terminal of the input sampling sub-circuit; The second input terminal of the constant current sub-circuit is electrically connected to the output terminal of the power supply circuit; The output terminal of the constant current sub-circuit is electrically connected to the first input terminal of the control sub-circuit. The first output terminal of the control sub-circuit is electrically connected to the first input terminal of the power transmission sub-circuit. The control sub-circuit is electrically connected to the power supply circuit, and the power transmission sub-circuit is electrically connected to the power supply circuit; The constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and to set a constant current voltage threshold through the power supply circuit, comparing the sampling voltage with the constant current voltage threshold. When the sampled voltage exceeds the constant current voltage threshold, the constant current sub-circuit sends a constant current protection control signal to the control sub-circuit to control the power transmission sub-circuit to perform constant current protection until the sampled voltage is within the constant current voltage threshold.

2. The constant current protection circuit according to claim 1, characterized in that, The constant current sub-circuit includes an NMOS transistor, an operational amplifier, a diode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor; the third input terminal of the constant current sub-circuit is electrically connected to the second output terminal of the control sub-circuit; wherein: The source of the NMOS transistor serves as the first input terminal of the constant current sub-circuit, and the drain of the NMOS transistor is electrically connected to one end of the first resistor. The gate of the NMOS transistor serves as the third input terminal of the constant current sub-circuit, and is electrically connected to one end of the second resistor and one end of the third resistor. The non-inverting input terminal of the operational amplifier is electrically connected to the other end of the third resistor, and to one end of the fourth resistor, and to one end of the sixth resistor, and to one end of the third capacitor; The inverting input terminal of the operational amplifier is electrically connected to the other end of the first resistor, and to the other end of the second resistor, and to one end of the fifth resistor, and to one end of the second capacitor, and to one end of the seventh resistor. The output terminal of the operational amplifier is electrically connected to the negative terminal of the diode and to one end of the fourth capacitor; The positive power input terminal of the operational amplifier serves as the second input terminal of the constant current sub-circuit, and is electrically connected to one end of the first capacitor and the other end of the fourth resistor. The negative input terminal of the operational amplifier is grounded; The positive terminal of the diode serves as the second input terminal of the constant current sub-circuit; The other end of the fifth resistor is grounded; The other end of the sixth resistor is grounded; The other end of the seventh resistor is electrically connected to the other end of the fourth capacitor; The other end of the first capacitor is grounded; The other end of the second capacitor is grounded; The other end of the third capacitor is grounded.

3. A constant current protection circuit according to claim 2, characterized in that, Also includes: Input sub-circuit and output sub-circuit; where: The first output terminal of the input sub-circuit is electrically connected to the second input terminal of the power transmission sub-circuit. The second output terminal of the input sub-circuit is electrically connected to the input terminal of the input sampling sub-circuit; The input terminal of the output sub-circuit is electrically connected to the output terminal of the power transmission sub-circuit; The input sub-circuit is used to transmit electrical energy to the output sub-circuit through the power transmission sub-circuit and to provide sampling current for the input sampling sub-circuit.

4. A constant current protection circuit according to claim 3, characterized in that, The constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and to set a constant current voltage threshold through the power supply circuit, comparing the sampling voltage with the constant current voltage threshold, including: The input sampling sub-circuit samples the current output by the input sub-circuit to obtain the sampling current, and converts the sampling current into the sampling voltage to output the sampling voltage to the constant current sub-circuit; The power supply circuit outputs a standard voltage to the constant current sub-circuit, so that the constant current sub-circuit sets the constant current voltage threshold by voltage division; The sampled voltage is compared with the constant current voltage threshold.

5. A constant current protection circuit according to claim 4, characterized in that, The power supply circuit outputs a standard voltage to the constant current sub-circuit, so that the constant current sub-circuit sets the constant current voltage threshold through voltage division, including: The power supply circuit outputs a standard voltage to the constant current sub-circuit; The second input terminal of the constant current sub-circuit receives the standard voltage, uses the standard voltage as the positive power input of the operational amplifier, and sets the constant current voltage threshold through the voltage division of the fourth resistor and the sixth resistor.

6. A constant current protection circuit according to claim 3, characterized in that, The second and third resistors are adjustable resistors used to adjust the output constant current value required for constant current protection; wherein: When the resistance value of the second resistor increases, the output constant current value decreases relatively. When the resistance value of the third resistor increases, the output constant current value increases relatively.

7. A constant current protection circuit according to claim 3, characterized in that, The constant current sub-circuit is used to detect the sampling voltage output by the input sampling sub-circuit, and a constant current voltage threshold is set by the power supply circuit. After comparing the sampling voltage with the constant current voltage threshold, the method further includes: When the sampled voltage is within the constant current voltage threshold, the constant current sub-circuit sends a normal operation signal to the control sub-circuit to control the power transmission sub-circuit to keep the output voltage constant.

8. A constant current protection circuit according to claim 7, characterized in that, It also includes an output sampling feedback sub-circuit; wherein: The input terminal of the output sampling feedback sub-circuit is electrically connected to the output terminal of the output sub-circuit; The output terminal of the output sampling feedback sub-circuit is electrically connected to the second input terminal of the control sub-circuit. The output sampling feedback sub-circuit is used to sample the voltage output by the output sub-circuit to obtain a feedback compensation voltage, and output the feedback compensation voltage to the control sub-circuit to control the power transmission sub-circuit to perform constant current protection.

9. A constant current protection circuit according to claim 8, characterized in that, The output of the control sub-circuit generates a periodic square wave signal to control the conduction time of the power transmission sub-circuit; wherein: When the constant current sub-circuit issues a constant current protection control signal, the control sub-circuit controls the power transmission sub-circuit to reduce the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to perform constant current protection; When the constant current sub-circuit issues a normal operation signal, the control sub-circuit controls the power transmission sub-circuit to maintain the conduction time of the periodic square wave signal based on the feedback compensation voltage, so as to keep the output voltage constant.

10. A constant current protection system, characterized in that, Includes a DC input power supply, a load, and a constant current protection circuit as described in any one of claims 1 to 9; wherein: The DC input power supply is electrically connected to the input sub-circuit of the constant current protection circuit; The load is electrically connected to the output sub-circuit of the constant current protection circuit.

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