Overcurrent protection circuit and device

Abstract

The invention discloses an overcurrent protection circuit and device, the circuit comprises a detection circuit, an amplification circuit, a comparison circuit, a drive circuit and an on-off circuit, the on-off circuit is connected with a power supply and a load, the detection circuit is connected with the load and the amplification circuit, the amplification circuit is connected with the detection circuit and the comparison circuit, and the drive circuit is connected with the detection circuit. The comparison circuit is respectively connected with the amplification circuit and the driving circuit, the driving circuit is connected with the comparison circuit and the driving circuit, and the driving circuit is respectively connected with the detection circuit and the on-off circuit. The detection circuit detects a detection current flowing through a load and converts the detection current into a detection voltage, the amplification circuit amplifies the detection voltage to obtain an amplified voltage, the comparison circuit compares the amplified voltage with a threshold voltage, and when the amplified voltage is higher than the threshold voltage, the driving circuit transmits a cut-off signal to the driving circuit; according to the invention, the amplifying circuit, the comparison circuit and the driving circuit are used for replacing a fuse, so that the cost is saved.

Description

Technical Field

[0001] This invention relates to the field of circuit protection technology, and in particular to an overcurrent protection circuit and device. Background Technology

[0002] Currently, overcurrent protection (OCP) primarily uses resettable fuses (Positive Temperature Coefficient, PTC) devices. For low-current loads, PTC devices can be selected due to their small size and low cost. However, for high-current loads, the PTCs used are not only large but also expensive. For example, high-power brushed or brushless motors, such as fans and water pumps, typically have a normal operating current exceeding 3A. In such cases, selecting a PTC as the overcurrent protection device requires at least 4A of normal non-triggered current and 6A of overcurrent triggered protection current. Furthermore, the trigger protection time becomes longer because the PTC relies on its own temperature rise to increase its resistance and thus reduce the current. However, temperature rise takes time, placing higher demands on the current and voltage withstand capabilities of the power supply components. Additionally, PTCs are susceptible to ambient temperature, which affects their trigger current threshold. The threshold decreases as ambient temperature rises and increases as ambient temperature falls. Summary of the Invention

[0003] The main objective of this invention is to provide an overcurrent protection circuit and device that can quickly disconnect the load from the power supply when the load experiences an overcurrent.

[0004] To achieve the above objectives, the present invention proposes an overcurrent protection circuit, which includes: a detection circuit, an amplification circuit, a comparison circuit, a driving circuit, and a switching circuit, wherein...

[0005] The on / off circuit is connected to the power supply and the load respectively; the detection circuit is connected to the load and the amplification circuit respectively; the amplification circuit is connected to the detection circuit and the comparison circuit respectively; the comparison circuit is connected to the amplification circuit and the driving circuit respectively; the driving circuit is connected to the comparison circuit and the driving circuit respectively; and the driving circuit is connected to the detection circuit and the on / off circuit respectively.

[0006] The detection circuit is used to detect the current of the load as a detection current and convert the detection current into a detection voltage, which is then transmitted to the amplification circuit.

[0007] The amplification circuit is used to receive the detection voltage, amplify the detection voltage to obtain an amplified voltage, and transmit the amplified voltage to the comparison circuit.

[0008] The comparison circuit is used to receive the amplified voltage, and when the amplified voltage is higher than the threshold voltage, generate and send an overcurrent signal to the drive circuit.

[0009] The driving circuit is used to generate and send a cut-off signal to the on / off circuit when the overcurrent signal is received.

[0010] The on / off circuit is used to disconnect the connection between the load and the power supply when the cut-off signal is received.

[0011] In one embodiment, the overcurrent protection circuit further includes a threshold circuit;

[0012] The threshold circuit is connected to the comparison circuit.

[0013] The threshold circuit is used to generate and send the threshold voltage to the comparison circuit. When the comparison circuit detects an overcurrent signal, the threshold voltage changes from a first preset voltage to a second preset voltage.

[0014] The comparison circuit is also used to receive the threshold voltage.

[0015] In one embodiment, the overcurrent protection circuit further includes: an MCU controller;

[0016] The MCU controller is connected to the drive circuit, the amplification circuit and the threshold circuit respectively;

[0017] The MCU controller is used to acquire the amplified voltage output by the amplification circuit, calculate the actual current based on the amplified voltage, and determine the power supply status of the load based on the actual current.

[0018] The MCU controller is also configured to generate and send an overcurrent signal to the drive circuit when the load is not powered, thereby controlling the threshold voltage of the threshold circuit to change from the second preset voltage to the first preset voltage.

[0019] In one embodiment, the power-on / off switch includes: a MOSFET;

[0020] The source of the MOS transistor is connected to the power supply and the driving circuit, the drain of the MOS transistor is connected to the input terminal of the load, and the gate of the MOS transistor is connected to the driving circuit.

[0021] In one embodiment, the driving circuit includes: a first transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor;

[0022] The source of the MOS transistor is connected to the power supply, the first resistor, and the first capacitor, respectively. The drain of the MOS transistor is connected to the input terminal of the load. The gate of the MOS transistor is connected to the other end of the first resistor, the other end of the first capacitor, and the second resistor, respectively. The other end of the second resistor is connected to the collector of the first transistor. The base of the first transistor is connected to the comparator circuit, the third resistor, and the fourth resistor, respectively. The emitter of the first transistor and the other end of the third resistor are grounded. The other end of the fourth resistor is connected to the MCU controller.

[0023] In one embodiment, the detection circuit includes: a fifth resistor and a second capacitor;

[0024] One end of the fifth resistor is connected to the amplifier circuit, the output terminal of the load, and the second capacitor, respectively, and the other end of the fifth resistor and the other end of the second capacitor are grounded.

[0025] In one embodiment, the amplification circuit includes: a first operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, a fourth capacitor, and a fifth capacitor;

[0026] One end of the sixth resistor is connected to the first power supply, and the other end of the sixth resistor is connected to the seventh resistor, the third capacitor, and the eighth resistor. The other end of the seventh resistor is connected to the output terminal of the fifth resistor and the load. The other end of the eighth resistor is connected to the positive input terminal of the first operational amplifier. The negative input terminal of the first operational amplifier is connected to the ninth resistor, the tenth resistor, and the fourth capacitor. The output terminal of the first operational amplifier is connected to the other end of the tenth resistor, the other end of the fourth capacitor, and the eleventh resistor. The other end of the eleventh resistor is connected to the fifth capacitor, the comparator circuit, and the MCU controller. The other ends of the fifth capacitor, the third capacitor, and the ninth resistor are all grounded.

[0027] In one embodiment, the comparator circuit includes: a twelfth resistor, a second operational amplifier, a sixth capacitor, and a second transistor;

[0028] The positive input terminal of the second operational amplifier is connected to the eleventh resistor and the fifth capacitor, respectively. The negative input terminal of the second operational amplifier is connected to the threshold circuit. The power input terminal of the second operational amplifier is connected to the first power supply and the sixth capacitor, respectively. The output terminal of the second operational amplifier is connected to the twelfth resistor and the threshold circuit, respectively. The other end of the twelfth resistor is connected to the base of the second transistor. The source of the second transistor is connected to the base of the first transistor, the third resistor, and the fourth resistor, respectively. The emitter of the second transistor, the other end of the sixth capacitor, and the negative input terminal of the power supply of the second operational amplifier are grounded.

[0029] In one embodiment, the threshold circuit includes: a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third transistor, and a fourth transistor;

[0030] One end of the thirteenth resistor is connected to the first power supply, and the other end of the thirteenth resistor is connected to the fourteenth resistor, the negative input terminal of the second operational amplifier, and the collector of the third transistor. The base of the third transistor is connected to the fifteenth resistor, and the emitter of the third transistor is connected to the collector of the fourth transistor and the sixteenth resistor. The other end of the fifteenth resistor is connected to the output terminal of the second operational amplifier and the twelfth resistor. The base of the fourth transistor is connected to the seventeenth resistor, and the other end of the seventeenth resistor is connected to the MCU controller. The other ends of the fourteenth resistor, the sixteenth resistor, and the emitter of the fourth transistor are grounded.

[0031] The present invention also proposes an overcurrent protection device, which includes the overcurrent protection circuit described above.

[0032] The technical solution of this invention employs an overcurrent protection circuit that can quickly disconnect the load from the power supply in case of overcurrent. The overcurrent protection circuit includes: a detection circuit, an amplification circuit, a comparator circuit, a drive circuit, and a switching circuit. The switching circuit is connected to the power supply and the load, respectively. The detection circuit is connected to both the load and the amplification circuit. The amplification circuit is connected to both the detection circuit and the comparator circuit. The comparator circuit is connected to both the amplification circuit and the drive circuit. The drive circuit is connected to both the comparator circuit and the drive circuit. The drive circuit is also connected to both the detection circuit and the switching circuit. The detection circuit detects the current flowing through the load and converts it into a detection voltage. The amplification circuit amplifies the detection voltage to obtain an amplified voltage. The comparator circuit compares the amplified voltage with a threshold voltage. When the amplified voltage is higher than the threshold voltage, the drive circuit sends a cutoff signal to the drive circuit, which then disconnects the power supply and the load via the switching circuit. This invention replaces a PTC (Power Transmitter) circuit with an amplification circuit, a comparator circuit, and a drive circuit, saving costs. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0034] Figure 1 A schematic diagram of a module of a first embodiment of the overcurrent protection circuit provided by the present invention;

[0035] Figure 2 A circuit diagram of the first embodiment of the overcurrent protection circuit provided by the present invention;

[0036] Figure 3 A circuit diagram of a second embodiment of the overcurrent protection circuit provided by the present invention;

[0037] Figure 4 This is a circuit diagram of an embodiment of the overcurrent protection circuit provided by the present invention.

[0038] Explanation of icon numbers:

[0039] label name label name 100 On / off circuit 200 Amplifier circuit VCC1 First power supply 900 Comparator circuit 300 power supply VCC power supply 400 load M1 MOSFET 500 Detection circuit Q1~Q5 Transistors 1 to 5 600 drive circuit C1~C6 Capacitors 1 through 6 700 MCU controller R1~R19 Resistors 1 to 19 800 Threshold circuit A, B First and second operational amplifiers

[0040] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0043] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0044] Currently, overcurrent protection (OCP) primarily uses resettable fuses (Positive Temperature Coefficient, PTC) devices. For low-current loads, PTC devices can be selected due to their small size and low cost. However, for high-current loads, the PTCs used are not only large but also expensive. For example, high-power brushed or brushless motors, such as fans and water pumps, typically have a normal operating current exceeding 3A. In such cases, selecting a PTC as the overcurrent protection device requires at least 4A of normal non-triggered current and 6A of overcurrent triggered protection current. Furthermore, the trigger protection time becomes longer because the PTC relies on its own temperature rise to increase its resistance and thus reduce the current. However, temperature rise takes time, placing higher demands on the current and voltage withstand capabilities of the power supply components. Additionally, PTCs are susceptible to ambient temperature, which affects their trigger current threshold. The threshold decreases as ambient temperature rises and increases as ambient temperature falls.

[0045] This invention proposes an overcurrent protection circuit.

[0046] Please see Figure 1 , Figure 1 This is a schematic diagram of a module of an embodiment of the overcurrent protection circuit proposed in this invention.

[0047] In this embodiment, the overcurrent protection circuit includes: a detection circuit, an amplification circuit, a comparator circuit, a drive circuit, and a switching circuit. The switching circuit is connected to the power supply and the load, respectively. The detection circuit is connected to the load and the amplification circuit, respectively. The amplification circuit is connected to the detection circuit and the comparator circuit, respectively. The comparator circuit is connected to the amplification circuit and the drive circuit, respectively. The drive circuit is connected to the detection circuit and the switching circuit, respectively. The detection circuit is used to detect the current of the load as a detection current and convert the detection current into a detection voltage, which is then transmitted to the amplification circuit. The amplification circuit is used to receive the detection voltage, amplify the detection voltage to obtain an amplified voltage, and transmit the amplified voltage to the comparator circuit. The comparator circuit is used to receive the amplified voltage and, when the amplified voltage is higher than a threshold voltage, generate and send an overcurrent signal to the drive circuit. The drive circuit is used to generate and send a cutoff signal to the switching circuit when it receives the overcurrent signal. The switching circuit is used to disconnect the connection between the load and the power supply when it receives the cutoff signal.

[0048] It should be noted that the overcurrent protection circuit of the present invention has the following advantages over existing PTC technology:

[0049] (1) This invention uses two operational amplifiers and several transistors. Although the number of components has increased, the cost is much cheaper than that of a single PTC device, giving it a cost advantage.

[0050] (2) The hardware of the present invention has the function of directly and instantly shutting off the power and locking the device when the current exceeds the set threshold, with a time not exceeding 20us. The protection time is extremely short and software is required to unlock it, providing double protection.

[0051] (3) The overcurrent threshold of the present invention can be set according to the requirements and the circuit consistency is high, unlike the wide range of current threshold values ​​of PTC and the inconsistent protection threshold.

[0052] This invention targets high-power DC devices or components, such as brushed and brushless motors, water pumps, etc. In case of overcurrent or short circuit, this circuit can respond quickly and can unlock overcurrent protection by software and issue an alarm after multiple determinations that there is indeed an overcurrent.

[0053] In this embodiment, when the load is overcurrent, the detection circuit detects the current flowing through the load and converts the current into a detection voltage. The amplifier circuit amplifies the detection voltage to obtain an amplified voltage. The comparator circuit compares the amplified voltage with a threshold voltage. If the amplified voltage is higher than the threshold voltage, the drive circuit sends a cutoff signal to the drive circuit. The drive circuit disconnects the power supply and the load. This invention replaces the PTC with an amplifier circuit, a comparator circuit, and a drive circuit, saving costs.

[0054] Figure 2 This is a circuit diagram of the first embodiment of the overcurrent protection circuit proposed in this invention.

[0055] The power on / off process includes: a MOSFET M1; the source of the MOSFET is connected to the power supply and the driving circuit, the drain of the MOSFET is connected to the input terminal of the load, and the gate of the MOSFET is connected to the driving circuit.

[0056] Optionally, the MOS transistor can be replaced by a PNP transistor, with the gate of the MOS transistor M being the base of the transistor, the drain of the MOS transistor M being the collector of the transistor, and the source of the MOS transistor M being the emitter of the transistor. Alternatively, an integrated chip with the same working principle can be used instead.

[0057] The driving circuit includes: a first transistor Q1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first capacitor C1; the source of the MOSFET M1 is connected to the power supply 300, the first resistor R1, and the first capacitor C1, respectively; the drain of the MOSFET M1 is connected to the input terminal of the load; the gate of the MOSFET is connected to the other end of the first resistor R1, the other end of the first capacitor C1, and the second resistor, respectively; the other end of the second resistor R2 is connected to the collector of the first transistor Q1; the base of the first transistor is connected to the comparator circuit, the third resistor R3, and the fourth resistor R4, respectively; the emitter of the first transistor Q1 and the other end of the third resistor R3 are grounded; and the other end of the fourth resistor R4 is connected to the MCU controller.

[0058] It should be noted that the driving circuit 600 is connected to the comparator circuit and the switching circuit 100 respectively; the driving circuit 600 is used to generate and send a cut-off signal to the switching circuit 100 when it receives the overcurrent signal transmitted by the comparator circuit.

[0059] It is understandable that a resistor and capacitor connected in parallel form an RC step-down circuit: This is a common, low-cost voltage reduction method suitable for low-power devices. This circuit uses the cooperation of the resistor and capacitor to gradually reduce the voltage, while the resistor also acts as a discharge mechanism to ensure safety.

[0060] The detection circuit includes a fifth resistor R5 and a second capacitor C2; one end of the fifth resistor R5 is connected to the amplifier circuit 200, the output terminal of the load and the second capacitor respectively, and the other end of the fifth resistor and the other end of the second capacitor are grounded.

[0061] It should be noted that the detection circuit is used to detect the current flowing through the load. The detection method involves connecting a small resistor, R5 (a fifth resistor), to the output terminal of the load. The resistance of R5 can be 0.1Ω. The current flowing through R5 is the current flowing through the load. When the load experiences overcurrent, the load current increases, and the voltage across R5 also increases, converting the current detection signal into a voltage detection signal. Whether the load is overcurrent can be determined based on whether the voltage across the fifth resistor is excessive.

[0062] Specifically, the MCU controls the power supply of the load to turn on and off. The MCU outputs a high level PUNP_EN, the first transistor Q1 is turned on, the voltage difference between the gate and source of the MOSFET is negative, the MOSFET is turned on, the load is connected to the power supply, and the current through the fifth resistor R5 is the load current. By acquiring the voltage PUMP_OUT of the fifth resistor R5, PUMP_OUT is the output voltage, and the corresponding current I = U / R can be indirectly calculated. The amplifier circuit amplifies PUMP_OUT to obtain the amplified voltage. If the amplified voltage is lower than the preset voltage, the comparator circuit sends a conduction signal to the drive circuit. The conduction signal is the high level of the OCP voltage. When the load is short-circuited or overcurrent, the current through the fifth resistor increases, and the voltage PUMP_OUT also increases. The amplified voltage after the output voltage is amplified by the amplifier circuit increases. When the amplified voltage is greater than the threshold voltage, the comparator circuit sends a cutoff signal to the driver circuit. The cutoff signal is when OCP is low. When OCP is low, the first transistor Q1 is cut off, and there is no voltage difference between the gate and source of the MOSFET M1. The MOSFET Q1 is cut off, disconnecting the connection between the power supply and the load. The load is not powered, and the PUMP_OUT voltage is 0V.

[0063] Furthermore, this embodiment also includes an eighteenth resistor R18, a nineteenth resistor R19, and a fifth transistor Q5. Because the current is very large and the time is very fast when the load is short-circuited—reaching hundreds of amperes within a few microseconds—and the drive circuit and the switching circuit 100 fail to react in time, the fifth transistor Q5 is used to conduct, temporarily cutting off the first transistor Q1, creating a state where the first transistor Q1 is continuously on and off. After the comparator circuit reacts, the OCP voltage of the first transistor Q1 is forcibly turned off. This is equivalent to the eighteenth resistor R18, the nineteenth resistor R19, and the fifth transistor Q5 forming a first-level protection.

[0064] Specifically, during normal operation, the resistance of the fifth resistor R5 is too low, the PUMP_OUT voltage is low, the fifth transistor is cut off, and the OCP voltage is not grounded, resulting in a high output voltage for the comparator circuit. During overcurrent, the PUMP_OUT voltage changes from low to high, the fifth transistor Q5 turns on, the OCP voltage is grounded and becomes low, the first transistor Q1 turns off, the MOSFET M1 turns off, the load has no power supply, the current becomes 0V, the PUMP_OUT voltage also becomes 0V, the fifth transistor Q5 turns off again, the OCP voltage is not grounded, resulting in a high output voltage for the comparator circuit, the first transistor Q1 turns on, the MOSFET M1 turns on, and because of the overcurrent, the PUMP_OUT voltage is high, creating a continuous cycle where the first transistor Q1 is constantly on and off until the comparator circuit directly outputs a low voltage, ending this cycle.

[0065] like Figure 3 The diagram shown is a circuit diagram of the second embodiment of the overcurrent protection circuit proposed in this invention.

[0066] Based on the first embodiment described above, a second embodiment of the overcurrent protection circuit of the present invention is proposed.

[0067] The amplifier circuit amplifies the load output voltage to obtain an amplified voltage. The comparator circuit compares the amplified voltage with a preset voltage. When the load is overloaded or short-circuited, the amplified voltage is greater than the preset voltage. The comparator circuit generates an overcurrent signal and transmits the overcurrent signal to the drive circuit. The drive circuit 600 sends a cutoff signal to the on / off circuit 100.

[0068] It should be noted that the output voltage is PUMP_OUT, the amplification voltage is OUT1, the preset voltage is VREF, the overcurrent signal is OCP at a low level, and the cutoff signal is the first transistor Q1 cutoff.

[0069] The amplifier circuit 200 includes: a first operational amplifier A, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5; one end of the sixth resistor R6 is connected to a first power supply, and the other end of the sixth resistor R6 is connected to the seventh resistor R7, the third capacitor C3, and the eighth resistor R8 respectively; the other end of the seventh resistor R7 is connected to the fifth resistor R5 and the output terminal of the load; and the other end of the eighth resistor R8 is connected to the first operational amplifier. The positive input terminal of the first operational amplifier A is connected to the ninth resistor R9, the tenth resistor R10, and the fourth capacitor C4, respectively. The output terminal of the first operational amplifier A is connected to the other end of the tenth resistor R10, the other end of the fourth capacitor C4, and the eleventh resistor R11, respectively. The other end of the eleventh resistor R11 is connected to the fifth capacitor C5, the comparator circuit 900, and the MCU controller 700, respectively. The other ends of the fifth capacitor C5, the third capacitor C3, and the ninth resistor R9 are all grounded.

[0070] It should be noted that, Figure 2 The fifth resistor R5 has a small resistance value. Even if the current is large, the voltage obtained is only in the mV range, which needs to be amplified. Therefore, an amplifier circuit needs to be added.

[0071] Specifically, such as Figure 3 A small voltage can be amplified to obtain a larger voltage. The output voltage is determined by the amplification factor, and the calculation formula is U=(PUMP_OUT+0.0326)*(1+R10 / R9). The output voltage PUMP_MCU is acquired by the MCU, which calculates the actual current of Ipump.

[0072] Optionally, the first operational amplifier can be replaced by an integrated chip with the same operating principle.

[0073] like Figure 4The comparator circuit 900 shown includes: a twelfth resistor R12, a second operational amplifier B, a sixth capacitor C6, and a second transistor Q2; the positive input terminal of the second operational amplifier B is connected to the eleventh resistor R11 and the fifth capacitor C5, the negative input terminal of the second operational amplifier B is connected to the threshold circuit, the power input terminal of the second operational amplifier B is connected to the first power supply VCC1 and the sixth capacitor C6, the output terminal of the second operational amplifier B is connected to the twelfth resistor R12 and the threshold circuit, the other end of the twelfth resistor R12 is connected to the base of the second transistor Q2, the source of the second transistor is connected to the base of the first transistor Q1, the third resistor R3, and the fourth resistor R4, and the emitter of the second transistor Q2, the other end of the sixth capacitor C6, and the negative input terminal of the power supply of the second operational amplifier B are grounded.

[0074] Specifically, the amplified voltage needs to be compared with a voltage threshold to determine the power-off operation after overcurrent. In amplifier circuit 200, the output OUT1 of the first operational amplifier A is compared with VREF. VREF is an adjustable parameter used to set a suitable threshold voltage. When OUT1 is less than VREF, OUT2 outputs a low level, the second transistor Q2 is not turned on, and OCP does not affect the conduction state of the first transistor Q1 in the drive circuit. When OUT1 is greater than VREF, OUT2 outputs a high level, the second transistor Q2 is turned on, OCP is grounded (low level), the first transistor Q1 in the drive circuit is turned off, and thus the MOSFET M1 is turned off.

[0075] It should be noted that when the circuit is operating normally, the VREF voltage output is the first preset voltage. Under normal operating conditions, OUT1 is less than VREF. When the load is short-circuited or overcurrent occurs, the PUMP_OUT output voltage increases, and the amplified voltage OUT1 also increases. At this time, the amplified voltage OUT1 is greater than the threshold voltage VREF, OUT2 outputs a high level, the second transistor Q2 is turned on, OCP is grounded and at a low level, and the comparator circuit sends an overcurrent signal to the drive circuit.

[0076] Optionally, the second operational amplifier can be replaced by an integrated chip with the same operating principle.

[0077] The overcurrent protection circuit further includes an MCU controller 700; wherein the MCU controller is connected to the drive circuit, the amplification circuit, and the threshold circuit respectively; the MCU controller is used to acquire the amplified voltage output by the amplification circuit, calculate the actual current based on the amplified voltage, determine the power supply status of the load based on the actual current, and when the load is not powered, generate and send an overcurrent signal to the drive circuit to control the threshold voltage of the threshold circuit to change from the second preset voltage to the first preset voltage.

[0078] Specifically, when the load power is turned on, the MCU sets PUMP_EN to a high level. At this time, the first transistor Q1 in the drive circuit turns on, thereby turning on the MOSFET M1, powering on the load, and the current flows through the fifth resistor R5. The voltage across R5 then flows through... Figure 4 The amplifier circuit amplifies the voltage, and the amplified voltage PUMP_MCU can be collected by the MCU controller to calculate the current Ipump.

[0079] Optionally, the MCU controller is a software-controlled circuit and can be replaced by a computer, chip, and controller.

[0080] When the circuit is working normally, the MCU outputs PUMP_EN at a high level to start the load power supply. The first transistor Q1 is turned on, the MOSFET M1 is turned on, and the load is powered on. PUMP_OUT is the voltage of the fifth resistor R5, which is also the output voltage of the load. PUMP_OUT is amplified by the first operational amplifier A to obtain the amplified voltage OUT1. At the same time, the MCU controller obtains PUMP_OUT and calculates the actual current. The amplified voltage OUT1 is transmitted to the second operational amplifier B and compared with the threshold voltage VREF. The amplified voltage OUT1 is less than VREF, so the output OUT2 of the second operational amplifier is low. The second transistor Q2 is turned off, and OCP is the MCU output PUMP_EN at a high level, and the load is continuously powered on.

[0081] When the load experiences overcurrent or a short circuit, the current in the circuit increases, the PUMP_OUT voltage increases, and the amplified voltage OUT1 after being amplified by the first operational amplifier A also increases. At this time, the amplified voltage OUT1 is greater than the threshold voltage VREF, the second operational amplifier B outputs a high level, the second transistor Q2 and the third transistor Q3 are turned on, the voltage at VREF becomes the second preset voltage, for example, 0V, OCP is grounded and at a low level, the first transistor Q1 is turned off, the MOSFET M1 is also turned off, and the load is de-energized. At this time, the load output voltage PUMP_OUT is 0V, the voltage OUT1 after being amplified by the first operational amplifier is 0.0326*(1+R10 / R9), that is, OUT1 will have a small non-zero voltage. The amplified voltage OUT1 is transmitted to the second operational amplifier B and compared with the threshold voltage VREF. At this time, VREF = 0V, the amplified voltage OUT1 is greater than VERF, the output OUT2 of the second operational amplifier is high level, the second transistor Q2 is turned on, OCP is grounded and at a low level, the first transistor Q1 is turned off, the MOSFET M1 is also turned off, and the load remains de-energized.

[0082] like Figure 4 The threshold circuit 800 shown is a circuit diagram of the third embodiment of the overcurrent protection circuit proposed in this invention.

[0083] Based on the first and / or second embodiments described above, a third embodiment of the overcurrent protection circuit of the present invention is proposed.

[0084] The overcurrent protection circuit further includes a threshold circuit 800; wherein the threshold circuit is connected to the comparator circuit 900; the threshold circuit 800 is used to generate and send the threshold voltage to the comparator circuit 900, and when the comparator circuit detects an overcurrent signal, the threshold voltage changes from a first preset voltage to a second preset voltage; the comparator circuit 900 is also used to receive the threshold voltage.

[0085] It should be noted that the threshold voltage is the first preset voltage at VREF, determined by the designer and determined by the voltage divider of R13 and R14. The second preset voltage is 0V, and the magnitude of the threshold voltage is controlled by the MCU controller and the output of the comparator circuit.

[0086] Understandably, VREF is an adjustable parameter used to set a suitable overcurrent threshold. When the circuit is working normally, the first preset voltage is output at the preset voltage VREF. When the circuit experiences an overcurrent, the preset voltage VREF becomes the second preset voltage, for example, 0V. At this time, OUT1 will be greater than VREF = 0V, OUT2 will output a high level, the second transistor Q2 will be turned on, and the OCP will be low, causing the power supply to turn off. This enters a cycle where the power supply is always locked off. That is, when the overcurrent exceeds the set threshold, the power supply will be self-locked, and the load will no longer be powered on.

[0087] The threshold circuit includes: a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a third transistor Q3, and a fourth transistor Q4; one end of the thirteenth resistor is connected to the first power supply, and the other end of the thirteenth resistor is connected to the fourteenth resistor R14, the negative input terminal of the second operational amplifier B, and the collector of the third transistor Q3; the base of the third transistor Q3 is connected to the fifteenth resistor R15; the emitter of the third transistor Q3 is connected to the collector of the fourth transistor Q4 and the sixteenth resistor R16; the other end of the fifteenth resistor R15 is connected to the output terminal of the second operational amplifier B and the twelfth resistor R12; the base of the fourth transistor Q4 is connected to the seventeenth resistor R17; the other end of the seventeenth resistor R17 is connected to the MCU controller; and the other ends of the fourteenth resistor R14, the sixteenth resistor R16, and the emitter of the fourth transistor Q4 are grounded.

[0088] Under normal operation, the MCU controls OCP_EN to output a high level, turning on the fourth transistor Q4. However, the base of the third transistor connected to OUT2 is at a low level, turning off the third transistor Q3. The threshold voltage VREF is close to the first preset voltage of the first power supply. When there is an overcurrent or short circuit, OUT1 is greater than the first preset voltage of VREF, OUT2 outputs a high level, turning on the third transistor Q3. The fourth transistor Q4 is continuously turned on by the MCU, and the threshold voltage VREF changes from the first preset voltage to the second preset voltage 0V. The second transistor Q2 turns on, and the first transistor Q1 is turned off. When MOSFET M1 is turned off, the load output voltage PUMP_OUT is 0V. After being amplified by the first operational amplifier, the voltage OUT1 is 0.0326*(1+R10 / R9), meaning OUT1 will have a small non-zero voltage. The amplified voltage OUT1 is transmitted to the second operational amplifier B and compared with the threshold voltage VREF. At this time, VREF = 0V, and the amplified voltage OUT1 is greater than VERF. The output OUT2 of the second operational amplifier is high, the second transistor Q2 is turned on, OCP is grounded and is low, the first transistor Q1 is turned off, and MOSFET M1 is also turned off, so the load is continuously de-energized.

[0089] Furthermore, when the load is overcurrent or short-circuited, the MCU's PUMP_EN enable is set to a high level. If the MCU detects that the collected voltage is 0.0326*(1+R10 / R9), then the MCU can assume that the load is open or short-circuited. That is, the load may be loose or short-circuited. In both cases, the device needs to be disassembled for inspection.

[0090] It should be noted that the MCU can repeatedly check whether there is a true open circuit or short circuit. In this case, a certain logic is required: the MCU must first... Figure 2 Setting PUMP_EN low ensures the power is off. Then, OCP_EN of the threshold circuit is pulled low, cutting off the fourth transistor Q4. The sixteenth resistor R16 is connected to the emitter terminal of the third transistor Q3, causing VREF to become close to 3.3V. At this point, VREF is greater than OUT1, resulting in OUT2 outputting a low level. The second transistor Q2 is cut off, and OCP no longer affects the first transistor Q1. Since OUT2 outputs a low level, the third transistor Q3 is cut off, and VREF returns to the first preset voltage of the overcurrent threshold, effectively unlocking the overcurrent circuit.

[0091] Before setting PUMP_EN high again, OCP_EN needs to be pulled high first to restore the OCP protection system to its normal state. After 100ms, set PUMP_EN high again and turn on the power. If the voltage collected by the MCU is still 0.0326*(1+R10 / R9), it means that either the load is open and no current is flowing, or an overcurrent has caused the protection system to activate and forcibly shut down the power, thus preventing the MCU from collecting current.

[0092] The system can be operated three times consecutively to confirm. If the result is the same after three attempts, it can be determined that the load is open or short-circuited. The MCU will then notify the host computer to issue an alarm and inform the user to check the relevant internal devices.

[0093] Specifically, before unlocking the OCP pin OCP_EN by pulling it low, the MCU's power control pin PUMP_EN must be set to low. Otherwise, if OCP_EN is set to low first, and the load is in a short-circuit state, PUMP_EN will still be high, turning on the power and damaging the MOSFET due to the short circuit.

[0094] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0095] The present invention also proposes an overcurrent protection device, which includes an overcurrent protection circuit. The specific structure of the overcurrent protection circuit is as described in the above embodiments. Since the overcurrent protection device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0096] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An overcurrent protection circuit, characterized by comprising: The overcurrent protection circuit includes: a detection circuit, an amplification circuit, a comparison circuit, a drive circuit, and a switching circuit, wherein, The on / off circuit is connected to the power supply and the load respectively; the detection circuit is connected to the load and the amplification circuit respectively; the amplification circuit is connected to the detection circuit and the comparison circuit respectively; the comparison circuit is connected to the amplification circuit and the driving circuit respectively; the driving circuit is connected to the comparison circuit and the driving circuit respectively; and the driving circuit is connected to the detection circuit and the on / off circuit respectively. The detection circuit is used to detect the current of the load as a detection current and convert the detection current into a detection voltage, which is then transmitted to the amplification circuit. The amplification circuit is used to receive the detection voltage, amplify the detection voltage to obtain an amplified voltage, and transmit the amplified voltage to the comparison circuit. The comparison circuit is used to receive the amplified voltage, and when the amplified voltage is higher than the threshold voltage, generate and send an overcurrent signal to the drive circuit. The driving circuit is used to generate and send a cut-off signal to the on / off circuit when the overcurrent signal is received. The on / off circuit is used to disconnect the connection between the load and the power supply when the cut-off signal is received.

2. The overcurrent protection circuit of claim 1, wherein, The overcurrent protection circuit further includes: a threshold circuit; The threshold circuit is connected to the comparison circuit. The threshold circuit is used to generate and send the threshold voltage to the comparison circuit. When the comparison circuit detects an overcurrent signal, the threshold voltage changes from a first preset voltage to a second preset voltage. The comparison circuit is also used to receive the threshold voltage.

3. The overcurrent protection circuit of claim 2, wherein, The overcurrent protection circuit also includes: an MCU controller; The MCU controller is connected to the drive circuit, the amplification circuit and the threshold circuit respectively; The MCU controller is used to acquire the amplified voltage output by the amplification circuit, calculate the actual current based on the amplified voltage, and determine the power supply status of the load based on the actual current. The MCU controller is also configured to generate and send an overcurrent signal to the drive circuit when the load is not powered, thereby controlling the threshold voltage of the threshold circuit to change from the second preset voltage to the first preset voltage.

4. The overcurrent protection circuit of claim 3, wherein, The switching circuit includes: a MOSFET; The source of the MOS transistor is connected to the power supply and the driving circuit, the drain of the MOS transistor is connected to the input terminal of the load, and the gate of the MOS transistor is connected to the driving circuit.

5. The overcurrent protection circuit of claim 4, wherein, The driving circuit includes: a first transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor; The source of the MOS transistor is connected to the power supply, the first resistor, and the first capacitor, respectively. The drain of the MOS transistor is connected to the input terminal of the load. The gate of the MOS transistor is connected to the other end of the first resistor, the other end of the first capacitor, and the second resistor, respectively. The other end of the second resistor is connected to the collector of the first transistor. The base of the first transistor is connected to the comparator circuit, the third resistor, and the fourth resistor, respectively. The emitter of the first transistor and the other end of the third resistor are grounded. The other end of the fourth resistor is connected to the MCU controller.

6. The overcurrent protection circuit of claim 5, wherein, The detection circuit includes: a fifth resistor and a second capacitor; One end of the fifth resistor is connected to the amplifier circuit, the output terminal of the load, and the second capacitor, respectively, and the other end of the fifth resistor and the other end of the second capacitor are grounded.

7. The overcurrent protection circuit of claim 6, wherein, The amplifier circuit includes: a first operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third capacitor, a fourth capacitor, and a fifth capacitor; One end of the sixth resistor is connected to the first power supply, and the other end of the sixth resistor is connected to the seventh resistor, the third capacitor, and the eighth resistor. The other end of the seventh resistor is connected to the output terminal of the fifth resistor and the load. The other end of the eighth resistor is connected to the positive input terminal of the first operational amplifier. The negative input terminal of the first operational amplifier is connected to the ninth resistor, the tenth resistor, and the fourth capacitor. The output terminal of the first operational amplifier is connected to the other end of the tenth resistor, the other end of the fourth capacitor, and the eleventh resistor. The other end of the eleventh resistor is connected to the fifth capacitor, the comparator circuit, and the MCU controller. The other ends of the fifth capacitor, the third capacitor, and the ninth resistor are all grounded.

8. The overcurrent protection circuit of claim 7, wherein, The comparator circuit includes: a twelfth resistor, a second operational amplifier, a sixth capacitor, and a second transistor; The positive input terminal of the second operational amplifier is connected to the eleventh resistor and the fifth capacitor, respectively. The negative input terminal of the second operational amplifier is connected to the threshold circuit. The power input terminal of the second operational amplifier is connected to the first power supply and the sixth capacitor, respectively. The output terminal of the second operational amplifier is connected to the twelfth resistor and the threshold circuit, respectively. The other end of the twelfth resistor is connected to the base of the second transistor. The source of the second transistor is connected to the base of the first transistor, the third resistor, and the fourth resistor, respectively. The emitter of the second transistor, the other end of the sixth capacitor, and the negative input terminal of the power supply of the second operational amplifier are grounded.

9. The overcurrent protection circuit of claim 8, wherein, The threshold circuit includes: a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third transistor, and a fourth transistor; One end of the thirteenth resistor is connected to the first power supply, and the other end of the thirteenth resistor is connected to the fourteenth resistor, the negative input terminal of the second operational amplifier, and the collector of the third transistor. The base of the third transistor is connected to the fifteenth resistor, and the emitter of the third transistor is connected to the collector of the fourth transistor and the sixteenth resistor. The other end of the fifteenth resistor is connected to the output terminal of the second operational amplifier and the twelfth resistor. The base of the fourth transistor is connected to the seventeenth resistor, and the other end of the seventeenth resistor is connected to the MCU controller. The other ends of the fourteenth resistor, the sixteenth resistor, and the emitter of the fourth transistor are grounded.

10. An overcurrent protection device, characterized in that, The overcurrent protection device includes the overcurrent protection circuit as described in any one of claims 1 to 9.

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