A practical output overcurrent protection circuit

Abstract

The utility model relates to a practical output overcurrent protection circuit, including a current detection unit, a protection control unit, a protection execution unit, an electronic device and a load. The practical output overcurrent protection circuit has the characteristics of simplicity, reliability and high efficiency, can effectively protect electronic equipment and users from the harm of output current overcurrent, and has a certain sensitivity and adjustability. It has a wide range of applications and also provides more reliable technical support for the development of electronic equipment.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, in particular to a practical output overcurrent protection circuit. Background Art

[0002] With the increasing popularity of electronic products and the continuous expansion of application scenarios, the application of DC power supplies has become more and more extensive. DC power supplies have the characteristics of high efficiency and reliability, which makes them widely used in electronic equipment. However, in DC power output applications, overcurrent phenomena often occur due to changes in load or other reasons. This phenomenon causes system crashes and damage to electronic devices. While causing damage to electronic equipment, it also reduces the service life of the DC power supply and may even cause danger to users. Therefore, it is very important to implement overcurrent protection in DC power supply output. Today, output overcurrent protection circuits have become an important component in electronic equipment.

[0003] At present, there are many output overcurrent protection circuits on the market, among which the traditional overcurrent protection circuit is mainly completed through the interaction of current transformers and power devices, but this solution has the disadvantages of complexity, high cost, poor effect, etc., which limits its application in DC power supply output. In the prior art, common output overcurrent protection circuits include current limiting circuits and current detection circuits. The current limiting circuit protects the system by limiting the output current, but its disadvantage is that it cannot automatically restore the output after a fault. The current detection circuit can monitor the output current and take corresponding measures, but its disadvantage is that it is not sensitive enough and it is easy to misjudge normal load as overcurrent. Utility Model Content

[0004] In order to overcome the shortcomings of traditional output overcurrent protection circuits, this paper proposes a practical output overcurrent protection circuit, which aims to effectively detect and protect electronic equipment and users from the harm of output overcurrent.

[0005] A practical output overcurrent protection circuit comprises a current detection unit, a protection control unit, a protection execution unit, an electronic device and a load. The current detection unit is respectively connected to the protection control unit, the protection execution unit and the load. The current detection unit comprises an overcurrent detection resistor, which detects the output current output from a power supply to the load, and obtains a current overcurrent signal by detecting the current on the load. The current overcurrent signal is sent to the protection control unit. The protection control unit is connected to the protection execution unit, which is connected to the electronic device. The protection control unit is used to make an output control signal according to the value of the output current. When the value of the output current exceeds the overcurrent protection threshold, the protection control unit outputs a control signal to the protection execution unit, and the protection execution unit outputs an execution signal to the electronic device, thereby reducing the current output from the electronic device to the load and protecting the electronic device.

[0006] Further, the protection control unit includes a power shutdown circuit and a current comparison circuit. The power shutdown circuit includes a switch tube Q25, a resistor, and a capacitor. The current comparison circuit includes a differential amplifier and a comparator. The input of the differential amplifier is connected to the overcurrent detection resistor of the current detection unit to receive the current overcurrent signal. The output of the differential amplifier is connected to the comparison input of the comparator. The output of the comparator is connected to the power shutdown circuit input. The differential amplifier includes an operational amplifier unit U28-A, a resistor R135, a resistor R48, a resistor R46, a resistor R115, and a resistor R116. One end of the resistor R135 is connected to the detection resistor. One end of resistor R135 is connected to the positive input terminal of operational amplifier unit U28-A, and one end of resistor R135 is also connected to one end of resistor R116, and the other end of resistor R116 is grounded. One end of resistor R115 is connected to the negative input terminal of operational amplifier unit U28-A, and one end of resistor R115 is also connected to one end of resistor R48, and the other end of resistor R48 is grounded. The other end of resistor R115 is connected to the output terminal of operational amplifier unit U28-A, and the other end of resistor R115 is also connected to one end of resistor R46, and the other end of resistor R46 is connected to the positive input terminal of operational amplifier unit U28-B, so as to output the differential amplified signal to the comparison input terminal of the comparator.

[0007] The comparator includes an operational amplifier unit U28-B, a resistor R134, a capacitor C47, and a reference power supply. The positive input terminal of the operational amplifier unit U28-B is connected to the signal output of the differential amplifier, the negative input terminal of the operational amplifier unit U28-B is connected to the reference power supply, the negative input terminal of the operational amplifier unit U28-B is also connected to one end of the capacitor C47, the other end of the capacitor C47 is connected to one end of the resistor R134, and the other end of the resistor R134 is connected to the output terminal of the operational amplifier unit U28-B. The operational amplifier unit U28-B compares the input signal with the reference power supply voltage and outputs a control signal to the power switch. The reference power supply includes a resistor R137, a resistor R138, a Zener diode U16, and a capacitor C75. The positive electrode of the Zener diode U16 is grounded, and the negative electrode of the Zener diode U16 is connected to the resistor R138. The negative electrode of the Zener diode U16 is simultaneously connected to one end of the resistor R137, one end of the resistor R138, and one end of the capacitor C47. The other end of the resistor R137 is connected to the negative input end of the operational amplifier unit U28-B and provides a reference power supply for the operational amplifier unit U28-B. The other end of the resistor R138 is connected to the power supply VCCS, and the other end of the capacitor C47 is connected to the ground.

[0008] Furthermore, the power shutdown circuit includes a power tube Q25, a transistor Q26, a resistor R199, a resistor R200, a resistor R198, a resistor R215, a resistor R139, a resistor R148, a capacitor C76, a capacitor C77, a capacitor C78, ​​a capacitor C79, a voltage stabilizing diode U23, an optocoupler OT1-B, a resistor R90, and a resistor R188. One end of the resistor R199 is connected to the output of the comparator, the other end of the resistor R199 is connected to the base of the transistor Q26, the other end of the resistor R199 is simultaneously connected to one end of the capacitor C78, ​​one end of the capacitor C79, and one end of the resistor R200, the other end of the capacitor C79, and the other end of the resistor R200 are grounded to the emitter of the transistor Q26, the other end of the capacitor C78 is simultaneously connected to one end of the resistor R215, the resistor R148, the capacitor C76, and one end of the capacitor C77, and the other end of the resistor R215 Connected to pin 2 of the power tube, the other end of the resistor R148 is connected to one end of the resistor R139, the other end of the resistor R148 is also connected to the adjustment pin of the voltage-stabilizing diode U23, the other end of the resistor R139, the other end of the capacitor C79, and the other end of the resistor R200 are grounded, the collector of the transistor Q26 is connected to pin 1 of the power tube Q25, the collector of the transistor Q26 is also connected to one end of the resistor R198, the other end of the resistor R198 is connected to the power supply VCCS, and the transistor Q26 is powered, the other end of the resistor R198 is also connected to pin 3 of the power tube Q25, pin 1 of the optical coupler OT1-B is connected to resistor R90, pin 2 of the optical coupler OT1-B is connected to one end of the resistor R188, pin 2 of the optical coupler OT1-B is also connected to the negative electrode of the voltage-stabilizing diode U23, the other end of the resistor R90 and the other end of the resistor R188 are connected to the power supply VCCS, and the positive electrode of the voltage-stabilizing diode U23 is grounded.

[0009] The current signal detected by the overcurrent detection resistor of the current detection unit is amplified by the differential amplifier and output to the positive input terminal of the comparator for comparison with the overcurrent reference level of the negative input terminal. When the output current of the power supply is normal, the operational amplifier unit U28-B outputs a low level to turn off the transistor Q26. After the transistor Q26 is turned off, it outputs a high level to pin 1 of the power tube Q25 to turn off the power tube Q25. Pins 2 and 3 of the power tube Q25 are disconnected. The voltage of the power supply VCCS cannot be connected to the three series-connected resistors R215, R148, and R139 through pins 2 and 3 of the power tube Q25, resulting in the voltage of the resistor R139 being zero. When the voltage on the resistor R139 is lower than the reference voltage of the Zener diode U23, the Zener diode U23 is turned on, and current flows through the optocoupler and outputs a control signal To the protection execution unit, the protection execution unit turns on the power of the electronic device; when the output current of the power supply is overcurrent, the operational amplifier unit U28-B outputs a high level to turn on the triode Q26, and after the triode Q26 is turned on, it outputs a low level to the 1st pin of the power tube Q25 to turn on the power tube Q25, and the 2nd and 3rd pins of the power tube Q25 are connected, and the voltage of the power supply VCCS is connected to the three series-connected resistors R215, R148, and R139 through the 2nd and 3rd pins of the power tube Q25, so that the voltage of the resistor R139 increases. When the voltage on the resistor R139 is higher than the reference voltage of the voltage-stabilizing diode U23, the voltage-stabilizing diode U23 is cut off, and no current flows through the optocoupler and stops outputting the control signal to the protection execution unit, and the protection execution unit reduces the current output by the electronic device to the load to protect the electronic device.

[0010] In the above practical output overcurrent protection circuit, a simple, reliable and efficient output overcurrent protection circuit can effectively protect electronic equipment and users from the harm of output current overcurrent, and has certain sensitivity and adjustability. It has a wide range of applications and also provides more reliable technical support for the development of electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a principle block diagram of a practical output overcurrent protection circuit according to an embodiment of the utility model.

[0012] Figure 2 It is a partial circuit schematic diagram of a protection control unit of a practical output overcurrent protection circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0013] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0014] See also Figure 1 and Figure 2, showing a practical output overcurrent protection circuit provided by an embodiment of the utility model, including a current detection unit, a protection control unit, a protection execution unit, an electronic device and a load, the current detection unit is respectively connected to the protection control unit, the protection execution unit, and the electronic device load, the current detection unit includes an overcurrent detection resistor, detects the output current output by the power supply to the load, obtains a current overcurrent signal by detecting the current on the load, the current overcurrent signal is sent to the protection control unit, the protection control unit is connected to the protection execution unit, the protection execution unit is connected to the electronic device, the protection control unit is used to make an output control signal according to the value of the output current obtained by the detection, when the value of the output current exceeds the overcurrent protection threshold, the protection control unit outputs a control signal to the protection execution unit, the protection execution unit outputs an execution signal to the electronic device, reduces the current output by the electronic device to the load, and protects the electronic device.

[0015] Furthermore, the protection control unit includes a power shutdown circuit and a current comparison circuit. The current comparison circuit includes a differential amplifier and a comparator. The input of the differential amplifier is connected to the overcurrent detection resistor of the current detection unit to receive the current overcurrent signal. The output of the differential amplifier is connected to the comparison input of the comparator. The output of the comparator is connected to the power shutdown circuit input. The differential amplifier includes an operational amplifier unit U28-A, a resistor R135, a resistor R48, a resistor R46, a resistor R115, and a resistor R116. One end of the resistor R135 is connected to the detection resistor, and one end of the resistor R135 is connected to the operational amplifier. The positive input terminal of the amplifier unit U28-A, one end of the resistor R135 is simultaneously connected to one end of the resistor R116, the other end of the resistor R116 is grounded, one end of the resistor R115 is connected to the negative input terminal of the amplifier U28-A, one end of the resistor R115 is simultaneously connected to one end of the resistor R48, the other end of the resistor R48 is grounded, the other end of the resistor R115 is connected to the output terminal of the amplifier unit U28-A, the other end of the resistor R115 is simultaneously connected to one end of the resistor R46, the other end of the resistor R46 is connected to the positive input terminal of the amplifier unit U28-B, and the differential amplified signal is output to the comparison input terminal of the comparator;

[0016] The comparator includes an operational amplifier unit U28-B, a resistor R134, a capacitor C47, and a reference power supply. The positive input terminal of the operational amplifier unit U28-B is connected to the signal output of the differential amplifier, the negative input terminal of the operational amplifier unit U28-B is connected to the reference power supply, the negative input terminal of the operational amplifier unit U28-B is also connected to one end of the capacitor C47, the other end of the capacitor C47 is connected to one end of the resistor R134, and the other end of the resistor R134 is connected to the output terminal of the operational amplifier unit U28-B. The operational amplifier unit U28-B compares the input overcurrent signal with the voltage of the reference power supply, and outputs a control signal to the power shutdown circuit after comparison. The reference power supply includes resistor R137, resistor R138, Zener diode U16, and capacitor C75. The positive electrode of the Zener diode U16 is grounded, and the negative electrode of the Zener diode U16 is connected to resistor R138. The negative electrode of the Zener diode U16 is simultaneously connected to one end of the resistor R137, one end of the resistor R138, and one end of the capacitor C47. The other end of the resistor R137 and the negative input end of the operational amplifier unit U28-B provide a reference power supply for the operational amplifier unit U28-B. The other end of the resistor R138 is connected to the power supply VCCS, and the other end of the capacitor C47 is connected to the ground. The voltage of the reference power supply can be set by selecting the zener voltage of the Zener diode U16.

[0017] Further, the power shutdown circuit includes a power tube Q25, a transistor Q26, a resistor R199, a resistor R200, a resistor R198, a resistor R215, a resistor R139, a resistor R148, a capacitor C76, a capacitor C77, a capacitor C78, ​​a capacitor C79, a voltage regulator diode U23, an optocoupler OT1-B, a resistor R90, and a resistor R188. One end of the resistor R199 is connected to the output of the comparator, and the other end of the resistor R199 is connected to the base of the transistor Q26, and one end of the capacitor C78, ​​one end of the capacitor C79, and one end of the resistor R200 are connected at the same time. The other end of the capacitor C79 and the other end of the resistor R200 are grounded to the emitter of the transistor Q26. The other end of the capacitor C78 is simultaneously connected to one end of the resistor R215, the resistor R148, the capacitor C76, and the capacitor C77. The other end of the resistor R215 is connected to the base of the power tube Q25. 2nd pin, the other end of the resistor R148 is connected to one end of the resistor R139, and the other end of the resistor R148 is also connected to the adjustment pin of the voltage-stabilizing diode U23. The other end of the resistor R139, the other end of the capacitor C79, and the other end of the resistor R200 are grounded. The collector of the transistor Q26 is connected to the 1st pin of the power tube Q25. The collector of the transistor Q26 is also connected to one end of the resistor R198, and the other end of the resistor R198 is connected to the power supply VCCS to supply power to the transistor Q26. The other end of the resistor R198 is also connected to the 3rd pin of the power tube Q25. The 1st pin of the optical coupler OT1-B is connected to one end of the resistor R90, and the 2nd pin of the optical coupler OT1-B is connected to one end of the resistor R188. The 2nd pin of the optical coupler OT1-B is also connected to the negative electrode of the voltage-stabilizing diode U23. The other end of the resistor R90 and the other end of the resistor R188 are both connected to the power supply VCCS, and the positive electrode of the voltage-stabilizing diode U23 is grounded.

[0018] When the current signal detected by the overcurrent detection resistor of the current detection unit is amplified by the differential amplifier, it is output to the positive input terminal of the comparator for comparison with the overcurrent reference level of the negative input terminal. When the output current of the power supply is normal, the operational amplifier unit U28-B outputs a low level to turn off the transistor Q26. After the transistor Q26 is turned off, it outputs a high level to pin 1 of the power tube Q25 to turn off the power tube Q25. Pins 2 and 3 of the power tube Q25 are disconnected. The voltage of the power supply VCCS cannot be connected to the three series-connected resistors R215, R148, and R139 through pins 2 and 3 of the power tube Q25, resulting in the voltage of resistor R139 being zero. When the voltage on resistor R139 is lower than the reference voltage of the Zener diode U23, the Zener diode U23 is turned on, and current flows through the optocoupler and outputs a control signal to The protection execution unit is used to connect the power supply of the electronic device; when the output current of the power supply is overcurrent, the operational amplifier unit U28-B outputs a high level to turn on the transistor Q26, and after the transistor Q26 is turned on, it outputs a low level to the 1st pin of the power tube Q25 to turn on the power tube Q25, and the 2nd and 3rd pins of the power tube Q25 are connected, and the voltage of the power supply VCCS is connected to the three series-connected resistors R215, R148, and R139 through the 2nd and 3rd pins of the power tube Q25, resulting in an increase in the voltage of the resistor R139. When the voltage on the resistor R139 is higher than the reference voltage of the voltage-stabilizing diode U23, the voltage-stabilizing diode U23 is cut off, and no current flows through the optocoupler and stops outputting the control signal to the protection execution unit. The protection execution unit limits the current output by the electronic device to the load to protect the electronic device.

[0019] The above practical output overcurrent protection circuit is simple, reliable and efficient, can effectively protect electronic equipment and users from the harm of output current overcurrent, and has certain sensitivity and adjustability. It has a wide range of applications and also provides more reliable technical support for the development of electronic equipment.

[0020] It should be noted that the present invention is not limited to the above-mentioned embodiments. According to the creative spirit of the present invention, those skilled in the art may also make other changes. These changes made according to the creative spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. A practical output overcurrent protection circuit, characterized in that: The invention comprises a current detection unit, a protection control unit, a protection execution unit, an electronic device and a load. The current detection unit is respectively connected to the protection control unit, the protection execution unit and the load of the electronic device. The current detection unit comprises an overcurrent detection resistor, which detects the output current of the power supply to the load. A current overcurrent signal is obtained by detecting the current on the load. The current overcurrent signal is sent to the protection control unit. The protection control unit is connected to the protection execution unit. The protection execution unit is connected to the electronic device. The protection control unit is used to make an output control signal according to the value of the output current. When the value of the output current exceeds the overcurrent protection threshold, the protection control unit outputs a control signal to the protection execution unit. The protection execution unit outputs an execution signal to the electronic device to reduce the current output from the electronic device to the load.

2. The practical output overcurrent protection circuit according to claim 1, characterized in that: The protection control unit includes a power shutdown circuit and a current comparison circuit. The current comparison circuit includes a differential amplifier and a comparator. The input of the differential amplifier is connected to the overcurrent detection resistor of the current detection unit to receive the current overcurrent signal. The output of the differential amplifier is connected to the comparison input of the comparator. The output of the comparator is connected to the power shutdown circuit input. The differential amplifier includes an operational amplifier unit U28-A, a resistor R135, a resistor R48, a resistor R46, a resistor R115, and a resistor R116. One end of the resistor R135 is connected to the detection resistor, and one end of the resistor R135 is connected to the operational amplifier unit U28-A. The positive input terminal of the operational amplifier unit U28-A, one end of the resistor R135 is simultaneously connected to one end of the resistor R116, the other end of the resistor R116 is grounded, one end of the resistor R115 is connected to the negative input terminal of the operational amplifier unit U28-A, one end of the resistor R115 is simultaneously connected to one end of the resistor R48, the other end of the resistor R48 is grounded, the other end of the resistor R115 is connected to the output terminal of the operational amplifier unit U28-A, the other end of the resistor R115 is simultaneously connected to one end of the resistor R46, the other end of the resistor R46 is connected to the positive input terminal of the operational amplifier unit U28-B, and the differential amplified signal is output to the comparison input terminal of the comparator.

3. The practical output overcurrent protection circuit according to claim 2, characterized in that: The comparator includes an operational amplifier unit U28-B, a resistor R134, a capacitor C47, and a reference power supply. The positive input terminal of the operational amplifier unit U28-B is connected to the signal output of the differential amplifier, the negative input terminal of the operational amplifier unit U28-B is connected to the reference power supply, the negative input terminal of the operational amplifier unit U28-B is also connected to one end of the capacitor C47, the other end of the capacitor C47 is connected to one end of the resistor R134, and the other end of the resistor R134 is connected to the output terminal of the operational amplifier unit U28-B. The operational amplifier unit U28-B compares the input signal with the reference power supply voltage and outputs a control signal to the power shutdown part. The reference power supply includes It includes resistor R137, resistor R138, Zener diode U16, and capacitor C75. The positive electrode of the Zener diode U16 is grounded, and the negative electrode of the Zener diode U16 is connected to one end of the resistor R138. The negative electrode of the Zener diode U16 is simultaneously connected to one end of the resistor R137 and one end of the capacitor C47. The other end of the resistor R137 and the negative input end of the operational amplifier unit U28-B provide a reference power supply for the operational amplifier unit U28-B. The other end of the resistor R138 is connected to the power supply VCCS, and the other end of the capacitor C47 is connected to the ground. The voltage of the reference power supply can be set by selecting the voltage regulator voltage parameter of the Zener diode U16.

4. The practical output overcurrent protection circuit according to claim 2, characterized in that: The power shutdown circuit includes a power tube Q25, a transistor Q26, a resistor R199, a resistor R200, a resistor R198, a resistor R215, a resistor R139, a resistor R148, a capacitor C76, a capacitor C77, a capacitor C78, ​​a capacitor C79, a voltage stabilizing diode U23, an optocoupler OT1-B, a resistor R90, and a resistor R188. One end of the resistor R199 is connected to the output of the comparator, the other end of the resistor R199 is connected to the base of the transistor Q26, the other end of the resistor R199 is simultaneously connected to one end of the capacitor C78, ​​one end of the capacitor C79, and one end of the resistor R200, the other end of the capacitor C79, the other end of the resistor R200 and the emitter of the transistor Q26 are simultaneously grounded, the other end of the capacitor C78 is simultaneously connected to one end of the resistor R215, the resistor R148, the capacitor C76, and the capacitor C77, the other end of the resistor R215 is connected to the power tube Pin 2 of Q25, the other end of resistor R148 is connected to one end of resistor R139, the other end of resistor R148 is also connected to the adjustment pin of voltage-stabilizing diode U23, the other end of resistor R139, the other end of capacitor C79, and the other end of resistor R200 are grounded, the collector of transistor Q26 is connected to pin 1 of power tube Q25, the collector of transistor Q26 is also connected to one end of resistor R198, the other end of resistor R198 is connected to power supply VCCS, powering transistor Q26, the other end of resistor R198 is also connected to pin 3 of power tube Q25, pin 1 of the optical coupler OT1-B is connected to one end of resistor R90, pin 2 of the optical coupler OT1-B is connected to one end of resistor R188, pin 2 of the optical coupler OT1-B is also connected to the negative electrode of voltage-stabilizing diode U23, the other end of resistor R90 and the other end of resistor R188 are connected to power supply VCCS, and the positive electrode of voltage-stabilizing diode U23 is grounded.

5. The practical output overcurrent protection circuit according to claim 2, characterized in that: The overcurrent current signal detected by the overcurrent detection resistor of the current detection unit is output to the current comparison circuit for comparison. When the output current of the power supply is normal, the current comparison circuit outputs a trigger signal to drive the power shutdown circuit, and the optocoupler OT1-B of the power shutdown circuit outputs a control signal to the protection execution unit, and the protection execution unit turns on the power of the electronic device; when the output current of the power supply of the electronic device is overcurrent, the current comparison circuit outputs a trigger signal to drive the power shutdown circuit, and the optocoupler of the power shutdown circuit stops outputting the control signal to the protection execution unit, and the protection execution unit reduces the current output by the electronic device to the load.

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