Current limiting circuit with adjustable current

Abstract

The utility model provides a current-limiting circuit with adjustable current magnitude, which comprises a current-limiting adjustment activation circuit, a current-limiting magnitude adjusting circuit and a current-limiting output circuit, the input end of the current-limiting adjustment activation circuit can receive a current-limiting circuit activation signal EN, and the output end of the current-limiting adjustment activation circuit is connected with the input end of the current-limiting magnitude adjusting circuit. The output end of the current-limiting size adjusting circuit is in control connection with the input end of the current-limiting output circuit, the input end of the current-limiting output circuit is further connected with a power supply, the output end of the current-limiting output circuit is in power supply connection with electric equipment, a three-end voltage-regulator tube Q2 is arranged in the current-limiting size adjusting circuit, and a field-effect tube Q1 is arranged in the current-limiting output circuit. The current-limiting size adjusting circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum value of the current finally output by the current-limiting output circuit. The current limiting circuit has the beneficial effects that the current limiting value in the current limiting circuit can be freely adjusted, and the production cost is low.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, and particularly relates to a current-limiting circuit with adjustable current magnitude. Background Art

[0002] A circuit refers to a conductive loop composed of metal wires and electronic components, which is called a circuit. The simplest circuit consists of a power source, a load, wires, switches and other components, which are connected in a certain way to provide a path for the flow of electric charges as a whole. There are also many common functional circuits, such as voltage-dividing circuits and current-limiting circuits. A voltage-dividing circuit is a circuit that uses resistor voltage division to achieve voltage reduction or voltage distribution of electrical signals. It consists of at least two resistors, usually including a larger resistor and a smaller resistor. The input signal passes through resistors with different resistance values in the resistor network, thereby realizing the adjustment of the output voltage. By correctly selecting the resistance value, the signal can be reduced to the required level, or the signal can be distributed to different receiving ports. A current-limiting circuit is a circuit that limits the magnitude of the current in a conductive loop to protect electronic components or the conductive loop from being burned out. It is usually connected in series between a rectifier bridge and a filter capacitor. A parallel circuit composed of a current-limiting resistor and a short-circuit switch is called a current-limiting circuit.

[0003] At present, current-limiting circuits are widely used in electronic products. For example, in the most typical battery charging circuit, the output power of the circuit is limited, which is generally achieved by using a current-limiting circuit. The most common current-limiting circuits are diode current-limiting circuits and current-limiting chip current-limiting circuits. The current-limiting value of the diode current-limiting circuit is generally very small, basically only a few milliamperes, and the current-limiting magnitude cannot be adjusted. Therefore, it is usually used in current-limiting circuits with very low output power, and the applicable range is very limited. Although the current-limiting value range of the current-limiting circuit using a current-limiting chip is relatively wide, the current-limiting chip has high requirements for the working voltage. It is usually used in current-limiting circuits with lower voltages and is not suitable for current-limiting circuits with higher voltages. The limitations are relatively large, and the cost is relatively high, bringing a not-so-good user experience. Summary of the Utility Model

[0004] To solve the problems in the prior art, the utility model provides a current-limiting circuit with adjustable current magnitude. By setting a mutually cooperating current-limiting adjustment activation circuit, a current-limiting magnitude adjustment circuit and a current-limiting output circuit in the current-limiting circuit with adjustable current magnitude, the current-limiting magnitude adjustment circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum value of the current finally output by the current-limiting output circuit, enabling free adjustment of the current-limiting value in the current-limiting circuit, with low production cost, greatly improving the user experience, and solving the problems in the prior art that the diode current-limiting in the current-limiting circuit has a very limited applicable range, the current-limiting chip current-limiting has high working voltage limitations and high costs, and the user experience is not good.

[0005] A current-limiting circuit with adjustable current magnitude provided by the present utility model includes a current-limiting adjustment activation circuit, a current-limiting magnitude adjustment circuit, and a current-limiting output circuit. The input end of the current-limiting adjustment activation circuit can receive a current-limiting circuit activation signal EN. The output end of the current-limiting adjustment activation circuit is connected to the input end of the current-limiting magnitude adjustment circuit. The output end of the current-limiting magnitude adjustment circuit is controllably connected to the input end of the current-limiting output circuit. A power supply is also connected to the input end of the current-limiting output circuit. The output end of the current-limiting output circuit is connected to supply power to an electrical device. A three-terminal voltage regulator Q2 is provided in the current-limiting magnitude adjustment circuit. A field-effect transistor Q1 is provided in the current-limiting output circuit. The current-limiting magnitude adjustment circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum value of the current finally output by the current-limiting output circuit.

[0006] The present utility model is further improved. The current-limiting adjustment activation circuit is provided with a triode Q3, a resistor R4, and a resistor R5. Among them, the base of the triode Q3 is connected to one end of the resistor R5 and one end of the resistor R4. The other end of the resistor R4 can receive the current-limiting circuit activation signal EN. The collector of the triode Q3 is connected to the input end of the current-limiting magnitude adjustment circuit. The other end of the resistor R5 and the emitter of the triode Q3 are grounded.

[0007] The present utility model is further improved. The current-limiting magnitude adjustment circuit is further provided with a variable resistor R2 and a resistor R3. Among them, the three-terminal voltage regulator Q2 has 3 pins. The first pin of the three-terminal voltage regulator Q2 is connected to one end of the variable resistor R2 and one end of the resistor R3. The third pin of the three-terminal voltage regulator Q2 is connected to the collector of the triode Q3 and the other end of the resistor R3. The second pin of the three-terminal voltage regulator Q2 is controllably connected to the other end of the variable resistor R2 and the input end of the current-limiting output circuit.

[0008] The present utility model is further improved. The current-limiting output circuit is further provided with a resistor R1. The gate of the field-effect transistor Q1 is connected to one end of the resistor R1, the second pin of the three-terminal voltage regulator Q2, and the other end of the variable resistor R2. The source of the field-effect transistor Q1 is connected to the other end of the resistor R1 and the power supply. The drain of the field-effect transistor Q1 is connected to supply power to the electrical device.

[0009] The present utility model is further improved. The model of the three-terminal voltage regulator Q2 is TL431. The voltages at the first and third pins of the three-terminal voltage regulator Q2 are constantly 2.5V.

[0010] The present utility model is further improved. The variable resistor R2 is a sliding rheostat. The resistance value of the resistor R3 is 10KΩ.

[0011] The present utility model is further improved. The field effect transistor Q1 is a PMOS, and the model of the field effect transistor Q1 is CJU40P04A.

[0012] The present utility model is further improved. The resistance value of the resistor R1 is 1KΩ.

[0013] The present utility model is further improved. The model of the triode Q3 is PMBT3904.

[0014] The present utility model is further improved. The resistance values of the resistor R4 and the resistor R5 are both 10KΩ.

[0015] Compared with the prior art, the beneficial effects of the present utility model are as follows: A current-limiting circuit with adjustable current magnitude is provided. By arranging a mutually cooperating current-limiting adjustment activation circuit, a current-limiting magnitude adjustment circuit, and a current-limiting output circuit in the current-limiting circuit with adjustable current magnitude, the current-limiting magnitude adjustment circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum current value finally output by the current-limiting output circuit, enabling free adjustment of the current-limiting value in the current-limiting circuit. Using a field effect transistor Q1 with a high withstand voltage range as a component of the current-limiting part, the current-limiting circuit can be applicable to all voltage ranges within the withstand voltage range of the field effect transistor Q1. At the same time, by adjusting the resistance value of the adjustable resistor R2, the maximum current value between the drain and source of the field effect transistor Q1, that is, the current-limiting value of the current-limiting circuit, can be adjusted, making the application scenario of the current-limiting circuit more extensive, with low production cost, greatly improving the user experience, and solving the problems in the prior art that the current-limiting circuit using a diode for current-limiting has a very limited applicable range, the current-limiting chip for current-limiting has a high working voltage limit and high cost, and the user experience is poor. Description of the Drawings

[0016] In order to more clearly illustrate the solutions in the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a principle block diagram of a current-limiting circuit with adjustable current magnitude of the present utility model;

[0018] Figure 2 It is a circuit diagram of a current-limiting circuit with adjustable current magnitude of the present utility model;

[0019] Figure 3 It is a relationship diagram among the Id, Vgs, and Vds of the field effect transistor Q1 of the present utility model. Detailed Embodiments

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this utility model belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this utility model; the terms "comprising" and "having" and any variations thereof in the specification and claims of this utility model and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this utility model or the above drawings are used to distinguish different objects and not to describe a specific order.

[0021] Referring to "embodiments" herein means that a specific feature, structure, or characteristic described in connection with the embodiments can be included in at least one embodiment of this utility model. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0022] In order to enable those skilled in the art of this technology to better understand the solution of this utility model, the technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0023] As Figures 1-3 shown, a current-limiting circuit with adjustable current magnitude provided by this utility model includes a current-limiting adjustment activation circuit, a current-limiting magnitude adjustment circuit, and a current-limiting output circuit. The input end of the current-limiting adjustment activation circuit can receive a current-limiting circuit activation signal EN. The output end of the current-limiting adjustment activation circuit is connected to the input end of the current-limiting magnitude adjustment circuit. The output end of the current-limiting magnitude adjustment circuit is controllably connected to the input end of the current-limiting output circuit. A power supply is also connected to the input end of the current-limiting output circuit. The output end of the current-limiting output circuit is connected to supply power to the electrical device. A three-terminal voltage regulator Q2 is provided in the current-limiting magnitude adjustment circuit, and a field-effect transistor Q1 is provided in the current-limiting output circuit. In this embodiment, the current-limiting magnitude adjustment circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum value of the current finally output by the current-limiting output circuit, and can realize free adjustment of the current-limiting value in the current-limiting circuit. Using a field-effect transistor Q1 with a high withstand voltage range as the current-limiting component can make the current-limiting circuit applicable to all voltage ranges within the withstand voltage range of the field-effect transistor Q1. At the same time, by adjusting the resistance value of the adjustable resistor R2, the maximum current value between the drain and source of the field-effect transistor Q1 can be adjusted, that is, the current-limiting value of the current-limiting circuit, making the application scenario of the current-limiting circuit more extensive, the production cost lower, and greatly improving the user experience.

[0024] As Figure 1As shown in the figure, the current-limiting adjustment activation circuit is provided with a triode Q3, a resistor R4 and a resistor R5. The model of the triode Q3 is PMBT3904. The base of the triode Q3 is connected to one end of the resistor R5 and one end of the resistor R4. The other end of the resistor R4 can receive the current-limiting circuit activation signal EN. The collector of the triode Q3 is connected to the input end of the current-limiting magnitude adjustment circuit. The other end of the resistor R5 and the emitter of the triode Q3 are grounded. The resistance values of the resistor R4 and the resistor R5 are both 10KΩ. The current-limiting magnitude adjustment circuit is also provided with a variable resistor R2 and a resistor R3. The model of the three-terminal voltage regulator Q2 is TL431. The three-terminal voltage regulator Q2 has 3 pins. The voltages at the 1st and 3rd pins of the three-terminal voltage regulator Q2 are constantly 2.5V. The 1st pin of the three-terminal voltage regulator Q2 is connected to one end of the variable resistor R2 and one end of the resistor R3. The 3rd pin of the three-terminal voltage regulator Q2 is connected to the collector of the triode Q3 and the other end of the resistor R3. The 2nd pin of the three-terminal voltage regulator Q2 is connected to the other end of the variable resistor R2 and the input end of the current-limiting output circuit for control connection. The variable resistor R2 is a slide rheostat. The resistance value of the resistor R3 is 10KΩ. The current-limiting output circuit is also provided with a resistor R1. The gate of the field-effect transistor Q1 is connected to one end of the resistor R1, the 2nd pin of the three-terminal voltage regulator Q2 and the other end of the variable resistor R2. The source of the field-effect transistor Q1 is connected to the other end of the resistor R1 and the power supply. The drain of the field-effect transistor Q1 is connected to supply power to the electrical equipment. The field-effect transistor Q1 is a PMOS, and the model of the field-effect transistor Q1 is CJU40P04A. The resistance value of the resistor R1 is 1KΩ.

[0025] In this embodiment, when the other end of the resistor R4 receives the current-limiting circuit activation signal EN as a high level, due to the existence of the resistor R4, the emitter and collector of the NPN-type triode Q3 are conducted, and the triode Q3 is in the amplification state. At this time, the collector of the triode Q3 is equivalent to being grounded, and then the current-limiting magnitude adjustment circuit composed of the resistor R2, the resistor R3 and the three-terminal voltage regulator Q2 starts to work normally. Since the characteristics of the three-terminal voltage regulator Q2 determine that the voltages at its 1st and 3rd pins are constantly 2.5V, and at this time, due to the existence of the resistor R2 and the resistor R3, there will be a fixed value at V1, that is, the gate voltage of the field-effect transistor Q1, i.e., V1 = 2.5V*(R2 + R3) / R3. Then the voltage Vgs between the gate and source of the field-effect transistor Q1 is Vgs = 24V – V1, and Vgs is also a fixed value.

[0026] As Figure 3As shown, according to the PMOS characteristics of the field-effect transistor Q1, when the voltage of Vgs is small, the field-effect transistor Q1 easily operates in the saturation region. That is, no matter how much the voltage Vds between the source and drain of the field-effect transistor Q1 increases, the corresponding current Id (the current between the source and drain of the field-effect transistor Q1) will not increase any more, achieving the current-limiting effect. In the corresponding circuit diagram, when the Vgs voltage of the field-effect transistor Q1 is constant, the maximum current between 24V and 24V_VOUT can be limited to a fixed value, achieving the current-limiting effect. By adjusting the value of the adjustable resistor R2, the voltage of V1 can be changed, and then the Vgs voltage of the field-effect transistor Q1 can be changed. As Figure 3 shown, different Vgs values will correspondingly change the maximum value of the Id current, that is, the adjustment of the current-limiting magnitude can be achieved. The circuit current limiting is completed independently by the field-effect transistor Q1. In this embodiment, the working voltage of the field-effect transistor Q1 can reach 40V. Then, the working voltage of the current-limiting circuit with adjustable current magnitude of the present utility model can also reach 40V. The type selection of the field-effect transistor Q1 can also be changed to achieve different working voltage limits. Among them, PMOS refers to an n-type substrate and a p-channel MOS transistor that transports current by the flow of holes. The working principle of PMOS is similar to that of NMOS. Since PMOS is an N-type silicon substrate, the majority carriers in it are electrons and the minority carriers are holes, and the doping type of the source and drain regions is P-type. Therefore, the working condition of PMOS is to apply a negative voltage to the gate relative to the source. That is, negative charge electrons are applied to the gate of PMOS, and movable positive charge holes and a depletion layer with fixed positive charges are induced in the substrate. Without considering the influence of the charges existing in the silicon dioxide, the number of positive charges induced in the substrate is equal to the number of negative charges on the PMOS gate. When strong inversion is reached, under the action of a drain-source voltage that is negative relative to the source terminal, the positive charge holes at the source terminal reach the drain terminal through the conducting P-type channel, forming a source-drain current from the source to the drain. Similarly, the more negative (the larger the absolute value) VGS is, the smaller the on-resistance of the channel is, and the larger the value of the current is.

[0027] As can be seen from the above, the present utility model provides a current-limiting circuit with adjustable current magnitude. By providing a current-limiting adjustment activation circuit, a current-limiting magnitude adjustment circuit, and a current-limiting output circuit that cooperate with each other in the current-limiting circuit with adjustable current magnitude, the current-limiting magnitude adjustment circuit can be activated by the current-limiting adjustment activation circuit and adjust the maximum current value finally output by the current-limiting output circuit, enabling free adjustment of the current-limiting value in the current-limiting circuit. Using the field-effect transistor Q1 with a high withstand voltage range as the current-limiting component can make the current-limiting circuit applicable to all voltage ranges within the withstand voltage range of the field-effect transistor Q1. At the same time, by adjusting the resistance value of the adjustable resistor R2, the maximum current value between the drain and source of the field-effect transistor Q1 can be adjusted, that is, the current-limiting value of the current-limiting circuit, making the application scenario of the current-limiting circuit more extensive, with low production costs, greatly improving the user experience, and solving the problems in the prior art that the current-limiting circuit using a diode for current limiting has a very limited applicable range, the current-limiting chip for current limiting has a high working voltage limit and high costs, and the user experience is poor.

[0028] The specific embodiments described above are the preferred embodiments of the present utility model, and do not limit the specific implementation scope of the present utility model. The scope of the present utility model includes but is not limited to this specific embodiment. All equivalent changes made in accordance with the present utility model are within the protection scope of the present utility model.

Claims

1. A current limiting circuit with adjustable current size, characterized in that: It includes a current limiting regulation activation circuit, a current limiting size adjustment circuit and a current limiting output circuit. The input end of the current limiting regulation activation circuit can receive a current limiting circuit activation signal EN, the output end of the current limiting regulation activation circuit is connected to the input end of the current limiting size adjustment circuit, the output end of the current limiting size adjustment circuit is control-connected to the input end of the current limiting output circuit, the input end of the current limiting output circuit is also connected to a power supply, the output end of the current limiting output circuit is connected to the power supply of an electrical device, a three-terminal voltage regulator Q2 is provided in the current limiting size adjustment circuit, a field effect transistor Q1 is provided in the current limiting output circuit, and the current limiting size adjustment circuit can be activated by the current limiting regulation activation circuit and adjust the maximum current value finally output by the current limiting output circuit.

2. The current limiting circuit with adjustable current size according to claim 1, characterized in that: The current limiting regulation activation circuit is provided with a transistor Q3, a resistor R4 and a resistor R5, wherein the base of the transistor Q3 is connected to one end of the resistor R5 and one end of the resistor R4, the other end of the resistor R4 can receive a current limiting circuit activation signal EN, the collector of the transistor Q3 is connected to the input end of the current limiting size adjustment circuit, and the other end of the resistor R5 and the emitter of the transistor Q3 are grounded.

3. The current limiting circuit with adjustable current size according to claim 2, characterized in that: The current limiting size adjustment circuit is also provided with an adjustable resistor R2 and a resistor R3, wherein the three-terminal voltage regulator Q2 is provided with 3 pins, the first pin of the three-terminal voltage regulator Q2 is connected to one end of the adjustable resistor R2 and one end of the resistor R3, the third pin of the three-terminal voltage regulator Q2 is connected to the collector of the transistor Q3 and the other end of the resistor R3, and the second pin of the three-terminal voltage regulator Q2 is controlled and connected to the other end of the adjustable resistor R2 and the input end of the current limiting output circuit.

4. The current limiting circuit with adjustable current size according to claim 3, characterized in that: The current limiting output circuit is also provided with a resistor R1, the gate of the field effect tube Q1 is connected to one end of the resistor R1, the second pin of the three-terminal voltage regulator Q2, and the other end of the adjustable resistor R2, the source of the field effect tube Q1 is connected to the other end of the resistor R1 and the power supply, and the drain of the field effect tube Q1 is connected to the power supply of the electrical equipment.

5. The current limiting circuit with adjustable current size according to claim 4, characterized in that: The model of the three-terminal voltage regulator Q2 is TL431, and the voltage at the first and third pins of the three-terminal voltage regulator Q2 is constant at 2.5V.

6. The current-limiting circuit with adjustable current size according to claim 5, characterized in that: The adjustable resistor R2 is a sliding resistor, and the resistance of the resistor R3 is 10KΩ.

7. The current limiting circuit with adjustable current size according to claim 6, characterized in that: The field effect transistor Q1 is a PMOS, and the model of the field effect transistor Q1 is CJU40P04A.

8. The current limiting circuit with adjustable current size according to claim 7, characterized in that: The resistance value of the resistor R1 is 1KΩ.

9. The current limiting circuit with adjustable current size according to claim 8, characterized in that: The model of the transistor Q3 is PMBT3904.

10. The current limiting circuit with adjustable current size according to claim 7, characterized in that: The resistance value of the resistor R4 and the resistance value of the resistor R5 are both 10KΩ.

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