Overcurrent protection circuit

Abstract

The utility model discloses an overcurrent protection circuit which comprises a response module, a comparison module and an MCU, the input end of the response module receives input current, the output end of the response module is connected with the input end of the comparison module, the output end of the comparison module is connected with the MCU, and the response module comprises a first optocoupler module, a resistor R6 and a resistor R7; the first optocoupler module is provided with a first input end, a second input end, a first output end and a second output end, one end of the resistor R6 is connected with input current, the other end of the resistor R6 is connected with the first input end of the first optocoupler module, one end of the resistor R7 is connected with the input current, and the other end of the resistor R7 is connected with the second input end of the first optocoupler module. The first output end of the first optocoupler module is connected with the input end of the comparison module, and the second output end of the first optocoupler module is grounded. The input current is isolated and sampled by adopting the first optocoupler module, so that the circuit runs stably, quick response is realized, the circuit structure can be effectively simplified, and the purpose of reducing the cost is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit overcurrent protection, in particular to an overcurrent protection circuit. Background Art

[0002] In order to ensure the stable operation of the power supply equipment, the circuit needs to be protected from overcurrent. The overcurrent protection circuit needs to sample the current. There are two schemes for sampling circuits in overcurrent protection circuits on the market. One is to use the Hall principle for sampling. Please refer to Figure 1 , Figure 1 It is an overcurrent protection circuit that uses Hall principle sampling. The current is generated by induction through the magnetic core and the Hall element, and then sent to the MCU detection port through the isolation amplifier. The MCU then compares the current with the reference value. If the current is greater than the reference value, the MCU triggers the overcurrent protection function and shuts down the power supply device.

[0003] Another method is to use sampling resistor sampling, please refer to Figure 2 , Figure 2 This is an overcurrent protection circuit that uses a sampling resistor for sampling. The current passes through the sampling resistor and then through the isolation amplifier to form a sampling current, which is then sent to the MCU detection port. The MCU will compare the current with the reference value. If the value of the sampling current is greater than the reference value, the MCU will shut down the power supply device to achieve the overcurrent protection function.

[0004] Among them, the former solution has a higher cost, while the latter solution has a lower cost compared to Solution 1. However, due to the unstable sampling current, an additional peripheral voltage stabilization circuit is required, which makes the overall circuit structure complex and the protection response time is long, affecting the stability of the system. Utility Model Content

[0005] In view of the deficiencies in the prior art, an overcurrent protection circuit is provided.

[0006] To achieve the above-mentioned purpose, the utility model provides an overcurrent protection circuit, including a response module, a comparison module and an MCU, the input end of the response module receives an input current, the output end of the response module is connected to the input end of the comparison module, the output end of the comparison module is connected to the MCU, the response module includes a first optocoupler module, a resistor R6 and a resistor R7; the first optocoupler module has a first input end, a second input end, a first output end and a second output end, one end of the resistor R6 is connected to the input current, and the other end thereof is connected to the first input end of the first optocoupler module, one end of the resistor R7 is connected to the input current, and the other end thereof is connected to the second input end of the first optocoupler module, the first output end of the first optocoupler module is connected to the input end of the comparison module, and the second output end of the first optocoupler module is grounded.

[0007] According to one embodiment of the utility model, a differential amplifier module is also included, which includes a first voltage divider unit, an amplifier U20 and a negative feedback unit. The first voltage divider unit is connected to the input end of the amplifier U20, the negative feedback unit is connected between the input end and the output end of the amplifier U20, and the output end of the amplifier U20 is connected to the input end of the response module.

[0008] According to one embodiment of the utility model, the response module also includes a second optocoupler module and a resistor R8, the second optocoupler module has a first input end, a second input end, a first output end and a second output end, one end of the resistor R8 is respectively connected to the resistor R7 and the second input end of the first optocoupler module, and the other end is connected to the first input end of the second optocoupler module, the second input end of the second optocoupler module receives the input current, the first output end of the second optocoupler module is connected to the input end of the comparison module, and the second output end of the second optocoupler module is grounded.

[0009] According to an embodiment of the present invention, a voltage-dropping resistor R1 is further included, and two ends of the voltage-dropping resistor R1 are respectively connected to the resistor R2 and the resistor R3 , and the voltage-dropping resistor R1 collects input current.

[0010] According to an embodiment of the present invention, the first optical coupling module and the second optical coupling module are both optical couplers.

[0011] According to one embodiment of the utility model, the comparison module includes a comparator U10, a first CR unit, a second voltage divider unit and a reverse protection unit; the positive input terminal of the comparator U10 is connected to the output terminal of the differential amplifier module, the reverse input terminal thereof is connected to the reference voltage, and the output terminal of the comparator U10 is connected to the MCU; the first CR unit is connected between the reverse input terminal and the output terminal of the comparator U10; one end of the second voltage divider unit is respectively connected to the output terminal of the comparator U10 and the first CR unit, and the other end thereof is connected to one end of the reverse protection unit, and the other end of the reverse protection unit is connected to the MCU.

[0012] According to an embodiment of the present invention, the comparison module further includes a first filtering unit, and the first filtering unit is connected between the comparator U10 and the response module.

[0013] According to one embodiment of the utility model, the first filtering unit includes a resistor R186, a capacitor C105 and a resistor R184; the resistor R186 is connected between the positive input terminal of the comparator U10 and the output terminal of the response module; one end of the capacitor C105 is respectively connected to the positive input terminal of the comparator U10 and the resistor R186, and the other end thereof is grounded; one end of the resistor R184 is respectively connected to the comparator U10, the capacitor C105 and the resistor R186, and the other end thereof is connected to the working voltage.

[0014] According to an embodiment of the present invention, the comparison module further includes a second CR unit; one end of the second CR unit is connected to the output end of the comparator U10, and the other end thereof is connected to the first CR unit.

[0015] According to one embodiment of the utility model, the comparison module also includes a comparator U10, an anti-interference unit and a second filtering unit. The anti-interference unit is connected between the positive input terminal and the reverse input terminal of the comparator U10. One end of the second filtering unit is connected to the output terminal of the comparator U10, and the other end thereof is connected to the reverse input terminal of the comparator U10.

[0016] The beneficial effect of the utility model is that by using the first optical coupling module to isolate and sample the input current, the circuit operation is stable and a fast response is achieved. In addition, by using the first optical coupling module, the circuit structure can be effectively simplified to achieve the purpose of cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0018] Figure 1 It is an over-current protection circuit that adopts Hall principle sampling;

[0019] Figure 2 It is an overcurrent protection circuit using sampling resistor sampling;

[0020] Figure 3 is a schematic diagram of an overcurrent protection circuit in an embodiment;

[0021] Figure 4 is a circuit diagram of a response module in an embodiment;

[0022] Figure 5 is a circuit diagram of a comparison module in an embodiment.

[0023] Description of Reference Numerals

[0024] 1-response module; 11-first optical coupling module; 12-second optical coupling module; 2-comparison module; 21-first CR unit; 22-second voltage divider unit; 23-reverse protection unit; 24-first filter unit; 25-second CR unit; 26-anti-interference unit; 27-second filter unit; 3-differential amplifier module; 31-first voltage divider unit; 32-negative feedback unit. DETAILED DESCRIPTION

[0025] The following will disclose multiple embodiments of the present invention with drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not necessary. In addition, in order to simplify the drawings, some conventional structures and components will be depicted in a simple schematic manner in the drawings.

[0026] In addition, in the present utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present utility model. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0027] Please refer to Figure 3 , Figure 3 It is a schematic diagram of an overcurrent protection circuit. The utility model provides an overcurrent protection circuit, which includes a response module 1, a comparison module 2 and an MCU. The input end of the response module 1 receives the input current, the output end of the response module 1 is connected to the input end of the comparison module 2, and the output end of the comparison module 2 is connected to the MCU. In the actual application scenario, the response module 1 is used to receive the input current and sample the input current, and then output the sampled current to the comparison module 2, and the comparison module 2 compares the sampled current with the reference current value. When the sampled current value is greater than the reference current value, the comparison module 2 sends a high-level signal to the MCU, and then the MCU sends a drive signal to shut down the power supply device to prevent the large current from damaging the power supply device, thereby playing an overcurrent protection role.

[0028] Please refer to Figure 4 , Figure 4 is a circuit diagram of the response module. Specifically, the response module 1 includes a resistor R6, a resistor R7 and a first optical coupling module 11, wherein the first optical coupling module 11 has a first input terminal, a second input terminal, a first output terminal and a second output terminal. One end of the resistor R6 receives the input current, and the other end thereof is connected to the first input terminal of the first optical coupling module 11. One end of the resistor R7 is respectively connected to the input current and the resistor R6, and the other end thereof is connected to the second input terminal of the first optical coupling module 11. The first output terminal of the first optical coupling module 11 is connected to the input terminal of the comparison module 2, and the second input terminal of the first optical coupling module 11 is grounded.

[0029] In this embodiment, the first optical coupling module 11 is an optical coupler, which has a primary light emitting diode and a secondary light receiver. When the DC input current is input into the response module 1, the DC input current is stepped down through the resistor R6, and enters the primary light emitting diode of the first optical coupling module 11 from the first input end of the first optical coupling module 11. At the same time, the input current is stepped down through the resistor R7. When the voltage drop generated by the resistor R7 is greater than the voltage drop of the primary light emitting diode of the first optical coupling module 11, the primary light emitting diode is turned on and lights up, so that the secondary light receiver is turned on. In this way, the first optical coupling module 11 is turned on. At this time, the first output end of the first optical coupling module 11 sends the sampling current to the input end of the comparison module 2, and then the comparison module 2 compares the sampling current with the reference current value. When the sampling current is greater than the reference current value, the comparison module 2 sends a high-level signal to the MCU, and the MCU sends a driving signal to turn off the power supply device after receiving the high-level signal. Therefore, by adopting the fast response of the first optical coupling module 11 to the DC input current, when the current is overcurrent, the MCU is quickly triggered to protect the power supply device, shortening the protection reaction time. At the same time, the input current is isolated and sampled by the first optical coupling module 11 to realize unidirectional transmission of the electrical signal, so that the circuit operates stably. In addition, there is no need to set up an additional voltage stabilizing circuit, which effectively simplifies the circuit structure.

[0030] In order to realize the sampling of the alternating current of the response module 1, the response module 1 further includes a second optical coupling module 12 and a resistor R8. The second optical coupling module 12 has a first input end, a second input end, a first output end and a second output end. One end of the resistor R8 is connected to the resistor R7 and the second input end of the first optical coupling module 11 respectively, and the other end thereof is connected to the first input end of the second optical coupling module 12. The second input end of the second optical coupling module 12 receives the input current, the first output end of the second optical coupling module 12 is connected to the input end of the comparison module 2, and the second output end of the second optical coupling module 12 is grounded.

[0031] The second optocoupler module 12 is used to receive and detect the reverse current in the AC input current. When the input current is AC, when the current is in the positive half-wave cycle, the forward current is input from the input end of the response module 1, the first optocoupler module 11 is turned on, the second optocoupler module 12 is turned off, and the first output end of the first optocoupler module 11 outputs a current signal to the comparison module 2; when the current is in the negative half-wave cycle, the reverse current is input from the input end of the response module 1, the first optocoupler module 11 is turned off, the second optocoupler module 12 is turned on, and the first output end of the second optocoupler module 12 outputs a current signal to the comparison module 2. Therefore, by adding the second optocoupler module 12, the response to the reverse input current is achieved, so that the response module 1 can collect AC. Therefore, when the input current is either DC or AC, the response module 1 is turned on, which effectively increases the application scenarios of the overcurrent protection circuit.

[0032] It should be noted that the second optical coupling module 12 and the first optical coupling module 11 are both optical couplers. Optical couplers have the characteristics of fast response speed and low cost. Optical couplers can achieve fast response to input current and effectively reduce costs.

[0033] Please continue to refer to Figure 4 , further, it also includes a differential amplifier module 3, which includes a first voltage divider unit 31, an amplifier U20 and a negative feedback unit 32. The first voltage divider unit 31 is connected to the input end of the amplifier U20, and is used to divide the input current. The negative feedback unit 32 is connected between the input end and the output end of the amplifier U20, and is used for negative feedback of the amplifier U20. The output end of the amplifier U20 is connected to the input end of the response module 1. The differential amplifier module 3 is used to amplify the differential mode signal and suppress the common mode signal. After the input current passes through the differential amplifier module 3, the interference signal is reduced and then output to the response module 1.

[0034] In this embodiment, the first voltage divider unit 31 includes a resistor R2 and a resistor R3, and the negative feedback unit 32 includes a resistor R4. The resistor R2 is connected to the reverse input terminal of the amplifier U20, and the resistor R3 is connected to the forward input terminal of the amplifier U20. The resistor R2 and the resistor R3 are used to limit the input current to prevent the amplifier U20 from being burned out due to excessive current. The resistor R4 is connected between the reverse input terminal and the output terminal of the amplifier U20, and the resistor R4 is used for negative feedback of the amplifier U20. In this example, a resistor R5 is also included, one end of the resistor R5 is connected to the resistor R3 and the forward input terminal of the amplifier U20 respectively, and the other end thereof is grounded.

[0035] In addition, the overcurrent protection circuit also includes a voltage-dropping resistor R1, the two ends of which are connected to resistors R2 and R3 respectively, and the two ends of the voltage-dropping resistor R1 collect input current. The input current enters the differential amplifier module 3 after being stepped down by the voltage-dropping resistor R1, so as to avoid large current from damaging the differential amplifier module 3.

[0036] Please refer to Figure 5 , Figure 5: is a circuit diagram of the comparison module. The comparison module 2 includes a comparator U10, a first CR unit 21, a second voltage divider unit 22 and a reverse protection unit 23. Among them, the positive input end of the comparator U10 is connected to the output end of the differential amplifier module 3, and its reverse input end is connected to the reference voltage. The reference voltage can be set according to the actual use situation. In this example, the reference voltage value is 1.5V. The output end of the comparator U10 is connected to the MCU. The first CR unit 21 is connected between the reverse input end and the output end of the comparator U10, and the first CR unit 21 is used for filtering. One end of the second voltage divider unit 22 is respectively connected to the output end of the comparator U10 and the first CR unit 21, and the other end is connected to one end of the reverse protection unit 23. The other end of the reverse protection unit 23 is connected to the MCU.

[0037] In this embodiment, the first CR unit 21 includes a resistor R189 and a capacitor C109, the second voltage divider unit 22 includes a resistor R185, and the reverse protection unit 23 includes a diode D27. One end of the resistor R189 is connected to the resistor R185 and the output end of the comparator U10 respectively, and the other end thereof is connected to the capacitor C109, and the other end of the capacitor is connected to the reverse input end of the comparator U10. The capacitor C109 and the resistor R189 are used to filter high-frequency signals. One end of the resistor R185 is connected to the cathode of the diode D27, and the other end thereof is connected to the output end of the comparator U10. The anode of the diode D27 is connected to the MCU, and the cathode of the diode D27 is connected to the output end of the comparator U10. The diode D27 is used to protect the reverse input voltage of the comparator U10 and the MCU.

[0038] Furthermore, the comparison module 2 further includes a first filtering unit 24. The first filtering unit 24 is connected between the comparator U10 and the response module 1. The first filtering unit 24 is used to filter the sampled current output by the response module 1.

[0039] In this embodiment, the first filtering unit 24 includes a resistor R186, a capacitor C105 and a resistor R184. One end of the resistor R186 is connected to the positive input end of the comparator U10, and the other end thereof is connected to the output end of the response module 1. One end of the capacitor C105 is respectively connected to the positive input end of the comparator U10 and the resistor R186, and the other end thereof is grounded. One end of the resistor R184 is connected to the positive input end of the comparator U10, and the other end thereof is connected to the 3.3V working voltage.

[0040] In addition, the comparison module 2 also includes a second CR unit 25, one end of the second CR unit 25 is connected to the output end of the comparator U10, and the other end thereof is connected to the first CR unit 21. In this example, the second CR unit 25 includes a resistor R188 and a capacitor C107, one end of the resistor R188 is respectively connected to the diode D7 and the resistor R185, and the other end thereof is connected to the capacitor C107, and the other end of the capacitor C107 is respectively connected to the input end of the comparator U10 and the resistor R189. The resistor R188 and the capacitor C107 are used for filtering to reduce high-frequency interference signals.

[0041] The comparison module 2 further includes a comparator U10, an anti-interference unit 26 and a second filtering unit 27. The anti-interference unit 26 is connected between the positive input terminal and the negative input terminal of the comparator U10. One end of the second filtering unit 27 is connected to the output terminal of the comparator U10, and the other end thereof is connected to the negative input terminal of the comparator U10.

[0042] In this embodiment, the anti-interference unit 26 includes a capacitor C97, and the second filtering unit 27 includes a bypass capacitor C106. The capacitor C97 is connected between the reverse input terminal and the forward input terminal of the comparator U10, and is used for anti-interference and preventing signal mutation. One end of the bypass capacitor C106 is connected to the output terminal of the comparator U10, and the other end is connected to the reverse input terminal of the comparator U10.

[0043] In summary, by using the first optical coupling module 11 to isolate and sample the input current, the circuit operates stably and achieves a fast response. In addition, by using the first optical coupling module 11, the circuit structure can be effectively simplified to achieve the purpose of cost reduction. In addition, by using the second optical coupling module 12 in parallel with the first optical coupling module 11, the overcurrent protection circuit can be applied to both AC and DC, effectively increasing its application range.

[0044] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. An overcurrent protection circuit, characterized in that: include: A response module (1), a comparison module (2) and an MCU, wherein the input end of the response module (1) receives an input current, the output end of the response module (1) is connected to the input end of the comparison module (2), and the output end of the comparison module (2) is connected to the MCU, the response module (1) comprises a first optical coupling module (11), a resistor R6 and a resistor R7; the first optical coupling module (11) has a first input end, a second input end, a first output end and a second output end, one end of the resistor R6 is connected to the input current, and the other end thereof is connected to the first input end of the first optical coupling module (11), one end of the resistor R7 is connected to the input current, and the other end thereof is connected to the second input end of the first optical coupling module (11), the first output end of the first optical coupling module (11) is connected to the input end of the comparison module (2), and the second output end of the first optical coupling module (11) is grounded.

2. The overcurrent protection circuit according to claim 1, characterized in that: The invention also comprises a differential amplification module (3), wherein the differential amplification module (3) comprises a first voltage dividing unit (31), an amplifier U20 and a negative feedback unit (32), wherein the first voltage dividing unit (31) is connected to the input end of the amplifier U20, the negative feedback unit (32) is connected between the input end and the output end of the amplifier U20, and the output end of the amplifier U20 is connected to the input end of the response module (1).

3. The overcurrent protection circuit according to claim 1, characterized in that: The response module (1) further comprises a second optical coupling module (12) and a resistor R8, wherein the second optical coupling module (12) has a first input end, a second input end, a first output end and a second output end, one end of the resistor R8 is respectively connected to the resistor R7 and the second input end of the first optical coupling module (11), and the other end is connected to the first input end of the second optical coupling module (12), the second input end of the second optical coupling module (12) receives an input current, the first output end of the second optical coupling module (12) is connected to the input end of the comparison module (2), and the second output end of the second optical coupling module (12) is grounded.

4. The overcurrent protection circuit according to claim 1, characterized in that: It also includes a voltage-dropping resistor R1 , the two ends of which are connected to the resistor R2 and the resistor R3 , respectively, and the voltage-dropping resistor R1 collects input current.

5. The overcurrent protection circuit according to claim 3, characterized in that: The first optical coupling module (11) and the second optical coupling module (12) are both optical couplers.

6. The overcurrent protection circuit according to claim 2, characterized in that: The comparison module (2) comprises a comparator U10, a first CR unit (21), a second voltage divider unit (22) and a reverse protection unit (23); the positive input end of the comparator U10 is connected to the output end of the differential amplifier module (3), the reverse input end is connected to a reference voltage, and the output end of the comparator U10 is connected to an MCU; the first CR unit (21) is connected between the reverse input end and the output end of the comparator U10; one end of the second voltage divider unit (22) is respectively connected to the output end of the comparator U10 and the first CR unit (21), and the other end is connected to one end of the reverse protection unit (23), and the other end of the reverse protection unit (23) is connected to the MCU.

7. The overcurrent protection circuit according to claim 6, characterized in that: The comparison module (2) further comprises a first filtering unit (24), wherein the first filtering unit (24) is connected between the comparator U10 and the response module (1).

8. The overcurrent protection circuit according to claim 7, characterized in that: The first filtering unit (24) comprises a resistor R186, a capacitor C105 and a resistor R184; the resistor R186 is connected between the positive input terminal of the comparator U10 and the output terminal of the response module (1); one end of the capacitor C105 is respectively connected to the positive input terminal of the comparator U10 and the resistor R186, and the other end thereof is grounded; one end of the resistor R184 is respectively connected to the comparator U10, the capacitor C105 and the resistor R186, and the other end thereof is connected to the working voltage.

9. The overcurrent protection circuit according to claim 6, characterized in that: The comparison module (2) further comprises a second CR unit (25); one end of the second CR unit (25) is connected to the output end of the comparator U10, and the other end of the second CR unit (25) is connected to the first CR unit (21).

10. The overcurrent protection circuit according to claim 6, characterized in that: The comparison module (2) further comprises a comparator U10, an anti-interference unit (26) and a second filtering unit (27); the anti-interference unit (26) is connected between the positive input terminal and the negative input terminal of the comparator U10; one end of the second filtering unit (27) is connected to the output terminal of the comparator U10, and the other end thereof is connected to the negative input terminal of the comparator U10.

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