Current-limiting retraction protection circuit and output short-circuit protection device

Abstract

The utility model discloses a current-limiting retraction protection circuit, which relates to the field of switching power supply current-limiting protection and comprises a current detection circuit, a current reference setting circuit and an error amplification circuit, the current reference setting circuit comprises a first operational amplifier, a first diode, a voltage detection circuit and a maximum output current setting circuit; the input end of the error amplification circuit, the output end of the voltage detection circuit and the anode of the first diode are connected with the inverted input end of the first operational amplifier, and the cathode of the first diode is connected with the output end of the first operational amplifier; the in-phase input end of the first operational amplifier is connected with the output end of the maximum output current setting circuit; the error amplification circuit is used for comparing the output end voltage of the current detection circuit with the output end voltage of the current reference setting circuit. A high-precision resistor and a low-offset-voltage operational amplifier are used, so that an output current retraction point and a maximum current limiting point can be accurately set.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of switching power supply current -limiting protection, especially relates to a current -limiting retraction protection circuit and output short -circuit protection device. BACKGROUND

[0002] Reliability is an important index of switching power supply, whether can prevent the power tube current in switching power supply from being excessive and even damaging when the switching power supply occurs output short -circuit, is one of the important standards of judging reliability. When the switching power supply occurs output short -circuit, utilize current -limiting compensation loop to limit output current according to the drop of output voltage, and the specific control method is: when output voltage reaches the retraction point, output current starts to reduce with the drop of output voltage, and until output voltage is zero. After the adjustment of output current by current -limiting compensation loop, namely when the output short -circuit fault of switching power supply is removed, output current will also immediately increase with the increase of output voltage, until the retraction point, when output voltage and output current restore normal.

[0003] In the existing system, the current reference setting circuit that determines the retraction point adopts the output voltage sampling control triode to form the emitter follower to limit the output current, but due to the characteristics of triode being easily affected by temperature, the accuracy of the retraction point is affected.

[0004] In the process of realizing the present application, the inventor found that at least the following problems exist in the prior art:

[0005] Although the retraction point can be set by adjusting the elements in the current reference setting circuit at present, the setting of the retraction point is not accurate enough due to the existence of triode.

[0006] Therefore, how to accurately set the retraction point is a problem to be solved at present. INVENTION CONTENTS

[0007] Therefore, the purpose of the utility model is to provide a current -limiting retraction protection circuit and output short -circuit protection device, which can effectively solve the problem of inaccurate setting of the retraction point in the prior art. The specific scheme is as follows:

[0008] In order to effectively solve the above technical problems, the application provides a current -limiting retraction protection circuit, which comprises a current detection circuit, a current reference setting circuit and an error amplifier circuit, wherein the current reference setting circuit comprises a first operational amplifier, a first diode, a voltage detection circuit and a maximum output current setting circuit.

[0009] An anode of the first diode is connected with an inverting input terminal of the first operational amplifier, a common terminal thereof is as an output terminal of the current reference setting circuit, for outputting a current reference signal to the error amplifier circuit, a cathode of the first diode is connected with an output terminal of the first operational amplifier; a non-inverting input terminal of the first operational amplifier is connected with an output terminal of the maximum output current setting circuit, for inputting a voltage reference signal; an input terminal of the voltage detection circuit is connected with an output terminal of the switching power supply, for dividing the output voltage of the switching power supply, an output terminal of the voltage detection circuit is connected with the inverting input terminal of the first operational amplifier;

[0010] An input terminal of the current detection circuit is connected with an output current signal terminal of the switching power supply, for converting the output current of the switching power supply into a corresponding voltage signal and outputting to the error amplifier circuit;

[0011] Input terminals of the error amplifier circuit are connected with the output terminal of the current detection circuit and the output terminal of the current reference setting circuit, for outputting an error signal.

[0012] As an optional solution, in the current limiting and retracting protection circuit, the voltage detection circuit comprises a first resistor and a second resistor;

[0013] A first end of the first resistor is as the input terminal of the voltage detection circuit and is connected with the output terminal of the switching power supply; a second end of the first resistor is connected with a first end of the second resistor;

[0014] A second end of the second resistor is grounded.

[0015] As an optional solution, in the current limiting and retracting protection circuit, the voltage detection circuit further comprises a third resistor and a first capacitor;

[0016] A second end of the third resistor and a first end of the first capacitor are connected with the first end of the second resistor;

[0017] A first end of the third resistor is connected with a power supply; a second end of the first capacitor is grounded.

[0018] As an optional solution, in the current limiting and retracting protection circuit, the maximum output current setting circuit comprises a fourth resistor, a fifth resistor and a second capacitor;

[0019] A first end of the fifth resistor and a first end of the second capacitor are connected with a second end of the fourth resistor, a common terminal thereof is as the output terminal of the maximum output current setting circuit;

[0020] A first end of the fourth resistor is connected with the power supply; a second end of the fifth resistor and a second end of the second capacitor are grounded.

[0021] As an optional solution, in the current limiting retraction protection circuit, the error amplifier circuit is a current loop error amplifier, and the current loop error amplifier comprises a second operational amplifier, a sixth resistor, a seventh resistor, a third capacitor and a fourth capacitor.

[0022] The second end of the sixth resistor and the first end of the seventh resistor are connected with the inverting input end of the second operational amplifier; the first end of the third capacitor is connected with the output end of the second operational amplifier, and the common end thereof serves as the output end of the error amplifier circuit; the non-inverting input end of the second operational amplifier serves as the second end of the error amplifier circuit and is connected with the output end of the current reference setting circuit; the second end of the fourth capacitor is connected with the positive power supply end of the second operational amplifier.

[0023] The first end of the fourth capacitor is grounded.

[0024] The second end of the third capacitor is connected with the first end of the sixth resistor.

[0025] The second end of the seventh resistor serves as the first end of the error amplifier circuit and is connected with the output end of the current detection circuit; the input end of the error amplifier circuit comprises the first end of the error amplifier circuit and the second end of the error amplifier circuit.

[0026] As an optional solution, in the current limiting retraction protection circuit, further comprising a second diode and a light emitting diode.

[0027] The cathode of the second diode is connected with the output end of the error amplifier circuit, for controlling the output of the error signal.

[0028] The anode of the second diode is connected with the cathode of the light emitting diode.

[0029] As an optional solution, in the current limiting retraction protection circuit, the current detection circuit comprises a Hall current sensor.

[0030] The input end of the Hall current sensor serves as the input end of the current detection circuit and is connected with the output current signal end of the switching power supply, and the output end of the Hall current sensor serves as the output end of the current reference setting circuit and is connected with the first end of the error amplifier circuit.

[0031] As an optional solution, in the current limiting retraction protection circuit, the current reference setting circuit further comprises a fifth capacitor.

[0032] The first end of the fifth capacitor is grounded, and the second end of the fifth capacitor is connected with the positive power supply end of the first operational amplifier.

[0033] As an alternative, in the current limiting retraction protection circuit, the current reference setting circuit further comprises an eighth resistor.

[0034] The first end of the eighth resistor is connected with the inverting input end of the first operational amplifier, and the second end of the eighth resistor is connected with the output end of the voltage detection circuit.

[0035] To effectively solve the above technical problems, the application further provides an output short circuit protection device comprising the current limiting retraction protection circuit.

[0036] Compared with the prior art, the technical scheme provided by the application has at least the following beneficial effects:

[0037] The current limiting retracting protection circuit provided in the application comprises a current detection circuit, a current reference setting circuit and an error amplification circuit; wherein the current reference setting circuit comprises a first operational amplifier, a first diode, a voltage detection circuit and a maximum output current setting circuit; the output end of the voltage detection circuit and the output end of the maximum output current setting circuit are connected with the inverting input end and the non-inverting input end of the first operational amplifier respectively, the output end of the first operational amplifier is connected with the inverting input end of the first operational amplifier through the first diode, forming a negative feedback loop, wherein the cathode of the first diode is connected with the output end of the first operational amplifier, clamping the voltage of the inverting input end of the first operational amplifier not to exceed the voltage of the output end of the maximum output current setting circuit, the anode of the first diode is taken as the output end of the current reference setting circuit to output a current reference signal, connected with the error amplification circuit, and compare the current reference signal with the voltage signal corresponding to the actual output current, outputting the amplified error value. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0039] Figure 1 A circuit diagram of a current limiting retracting circuit provided for the embodiment;

[0040] Figure 2 A current limiting trajectory diagram provided for the embodiment;

[0041] Figure 3 A waveform diagram showing that the voltage value of the output end of a specific current reference setting circuit varies with the voltage division value of a voltage detection circuit provided for the embodiment;

[0042] The reference signs are as follows: 10 is a current reference setting circuit, 20 is an error amplifier circuit, 101 is a voltage detection circuit, and 102 is a maximum output current setting circuit. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0044] In order to enable personnel in the technical field to better understand the scheme of the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0045] Reliability is an important indicator of a switching power supply, and whether it can prevent the current of the power tube in the switching power supply from exceeding the standard or even being damaged when the switching power supply has an output short circuit is one of the important standards for judging reliability. When the switching power supply has an output short circuit, the current limiting compensation loop can limit the output current according to the drop of the output voltage, and the specific control method is as follows: when the output voltage reaches the retracting point, the output current starts to decrease with the decrease of the output voltage until the output voltage is zero. After the adjustment of the output current by the current limiting compensation loop, that is, when the output short circuit fault of the switching power supply is removed, the output current will immediately increase with the increase of the output voltage until the retracting point, at which time the output voltage and the output current return to normal.

[0046] In the existing system, the current reference setting circuit that determines the retracting point uses an output voltage sampling control transistor to form an emitter follower to limit the output current. However, due to the characteristics of the transistor being easily affected by temperature, the accuracy of the retracting point is affected. As can be seen, although the retracting point can be set by adjusting the elements in the current reference setting circuit at present, the setting of the retracting point is not accurate enough due to the presence of the transistor.

[0047] Therefore, how to accurately set the retracting point is a problem to be solved at present.

[0048] To effectively solve the above problems, such as Figure 1 As shown, this utility model embodiment discloses a current limiting and retraction protection circuit, including: a current detection circuit, a current reference setting circuit 10, and an error amplifier circuit 20; wherein, the current reference setting circuit 10 includes a first operational amplifier U1, a first diode D1, a voltage detection circuit 101, and a maximum output current setting circuit 102.

[0049] The input terminal of the current detection circuit is connected to the output current signal terminal of the switching power supply to convert the output current of the switching power supply into a corresponding voltage signal; however, it is understandable that... Figure 1 This is just one specific implementation method and does not mean that there can only be this one implementation method.

[0050] The anode of the first diode D1 is connected to the inverting input of the first operational amplifier U1, and its common terminal serves as the output of the current reference setting circuit 10, used to output a current reference signal. The cathode of the first diode D1 is connected to the output of the first operational amplifier U1. The non-inverting input of the first operational amplifier U1 is connected to the output of the maximum output current setting circuit 102, used to input a voltage reference signal. The inverting input of the first operational amplifier U1 is also connected to the output of the voltage detection circuit 101. The voltage detection circuit 101 is connected to the output of the switching power supply and is used to divide the output voltage of the switching power supply. However, it is understood that the voltage detection circuit 101 can be any circuit capable of dividing the output voltage, and the maximum output current setting circuit 102 can also be any circuit capable of outputting a set voltage value. Figure 1 This is just one specific implementation method and does not mean that there can only be this one implementation method.

[0051] The input terminal of the error amplifier circuit 20 is connected to the output terminal of the current detection circuit and the output terminal of the current reference setting circuit 10, and is used to output an error signal. However, it can be understood that any circuit that can perform error detection and error amplification between the voltage signal corresponding to the output current and the current reference signal can be the error amplifier circuit 20. Figure 1 This is just one specific implementation method and does not mean that there can only be this one implementation method.

[0052] In this embodiment, due to the presence of the current-limiting and feedback protection circuit, the relationship between the output voltage and output current of the switching power supply is as follows: Figure 2As shown, the vertical axis is the value of the output voltage, and the horizontal axis is the value of the output current. At this time, the voltage corresponding to the retraction point is V1, and the current corresponding to the retraction point is I2. I2 is the current limit point, and I1 is the current limit point when the output voltage is zero. Therefore, as the load increases, when the output current is less than I2, the output voltage remains at V2, in the non-current limiting section; when the load continues to increase, the output current reaches I2, and the output voltage begins to drop, in the constant-current limiting section; when the output voltage drops to V1, the output current will decrease with the decrease of the output voltage until the output voltage is zero, in the retraction limiting section. Among them, I1, I2, V1, V2 are the current values and voltage values set in the actual situation.

[0053] It can be understood that current is the flow of electric charge, and it is difficult to directly compare the size of the current, so the current detection circuit needs to convert the output current into a corresponding voltage signal. In a specific embodiment, a sampling resistor can be connected in series at the output end of the switching power supply, and the current detection circuit is connected to both ends of the sampling resistor and detects the voltage value on the sampling resistor as the voltage signal corresponding to the output current. At this time, the voltage signal is proportional to the output current, and the proportion is determined by the resistance value of the sampling resistor. Due to the low cost, fast response speed and other advantages of the sampling resistor, using the sampling resistor to convert the output current is the most commonly used method at present. When the sampling signal obtained directly through the sampling resistor is too weak, the quality and stability of the signal can be improved through amplification, filtering and other methods before being output as a voltage signal to the error amplifier circuit 20; in another specific embodiment, the current detection circuit includes a Hall current sensor connected to the output end of the switching power supply, which converts the output current into a voltage signal through the Hall current sensor. At this time, the output end of the Hall current sensor is the output end of the current detection circuit.

[0054] The output voltage of the current reference setting circuit 10 depends on the voltage of the inverting input of the first operational amplifier U1. When the output voltage of the voltage detection circuit 101 is less than the output voltage of the maximum output current setting circuit 102, the feedback loop is not turned on, and there is no resistance in the negative feedback loop of the first operational amplifier U1, so the first operational amplifier U1 does not amplify the voltage at the input, and thus the output voltage of the current reference setting circuit 10 is equal to the voltage at the inverting input of the first operational amplifier U1 and changes with the output voltage. When the output voltage of the voltage detection circuit 101 is greater than the output voltage of the maximum output current setting circuit 102, the feedback loop is turned on, clamping the voltage at the non-inverting input of the first operational amplifier U1 to be equal to the voltage at the inverting input, so when the output voltage is higher than the foldback point, as the output voltage rises, the output voltage of the current reference setting circuit 10 remains unchanged and is equal to the output voltage of the maximum output current setting circuit 102. It can be understood that by adjusting the voltage value output by the maximum output current setting circuit 102, the maximum current reference signal of the current reference setting circuit 10 can be determined, i.e. the current value corresponding to the foldback point can be accurately adjusted. In addition, adjusting the voltage detection circuit 101 can also adjust the position of the foldback point, the greater the voltage detection value, the smaller the voltage value corresponding to the foldback point at the same output voltage, i.e. adjusting the voltage detection value of the voltage detection circuit 101 and the voltage value output by the maximum output current setting circuit 102 can accurately adjust the foldback point.

[0055] In this embodiment, the current reference setting circuit 10 sets the current limit point of the switching power supply, and the current reference signal and the voltage signal output by the current detection circuit are input to the error amplification circuit 20 for comparison. In a specific embodiment, the error amplification circuit 20 is a current loop error amplifier, the output IOUT-OP of the current detection circuit and the output voltage of the current reference setting circuit 10 are compared through the current loop error amplifier, and the error is amplified and output to the switching power supply chip as an error signal to limit the output current of the switching power supply to be less than the current corresponding to the current reference signal.

[0056] It can be understood that the switching power supply chip can receive the error signal output by the error amplification circuit 20 and limit the output current by adjusting the output voltage of the switching power supply based on the error signal. In a specific embodiment, as shown in Figure 1 the FB-CTRL controls the duty cycle of the PWM (Pulse-Width Modulation) signal, controls the on-off ratio of the switching tube, and adjusts the size of the output current, and the error signal can adjust the duty cycle of the PWM signal to achieve control of the output current.

[0057] In this embodiment, adjusting the output voltage of the maximum output current setting circuit 102 can change the maximum current reference signal of the current reference setting circuit 10 to set the maximum current limiting point of the switching power supply. In a specific embodiment, the maximum output current setting circuit 102 can be a voltage dividing circuit composed of two resistors, the common terminal of the resistors being the output terminal of the maximum output current setting circuit 102, and the voltage dividing value being changed by adjusting the ratio of the two resistors to set the maximum current reference point. It can be understood that in order to make the adjustment of the maximum current reference point more simple, the above two resistors can be selected as adjustable resistors. In another specific embodiment, the maximum output current setting circuit 102 can be directly composed of a slide rheostat, the two fixed terminals of the slide rheostat being connected to the power supply and the ground respectively, and the sliding terminal being the output terminal of the maximum output current setting circuit 102, at this time, only the position of the sliding terminal needs to be adjusted to adjust the maximum current reference point.

[0058] It can be understood that the voltage at the output terminal of the voltage detection circuit 101 is not directly equal to the output voltage of the switching power supply, but is a voltage value proportional to the output voltage as a voltage value reflecting the output voltage, as the output of the voltage detection circuit 101. In a specific embodiment, the voltage detection circuit 101 is composed of two resistors in series, and the voltage value corresponding to the pinch point can be changed by adjusting the ratio of the two resistors, and the pinch point can be arbitrarily set by reasonably selecting the resistance value.

[0059] In a specific embodiment, as shown in Figure 3 the voltage dividing value of the maximum output current setting circuit 102 is set to 2.5V, and the voltage dividing value of the voltage detection circuit 101 when the output voltage is zero is 1V. As the output voltage rises, the voltage dividing value of the voltage detection circuit 101 is shown as line A in the figure, and the output voltage of the current reference setting circuit 10 is shown as line B in the figure. It is not difficult to see that as the output voltage rises, the output voltage of the current reference setting circuit 10 rises, and when the output voltage of the current reference setting circuit 10 reaches 2.5V, the output voltage of the current reference setting circuit 10 will no longer rise with the continuous rise of the output voltage.

[0060] In the embodiment, the current limiting retracting protection circuit comprises a current detection circuit, a current reference setting circuit 10 and an error amplification circuit 20; wherein the current reference setting circuit 10 comprises a first operational amplifier U1, a first diode D1, a voltage detection circuit 101 and a maximum output current setting circuit 102; the input end of the current detection circuit is connected with the output current signal end of the switching power supply, for converting the output current of the switching power supply into a corresponding voltage signal; the anode of the first diode D1 is connected with the inverting input end of the first operational amplifier U1, and the common end thereof serves as the output end of the current reference setting circuit 10, for outputting a current reference signal, and the cathode of the first diode D1 is connected with the output end of the first operational amplifier U1; the non-inverting input end of the first operational amplifier U1 is connected with the output end of the maximum output current setting circuit 102, for inputting a voltage reference signal, and the inverting input end of the first operational amplifier U1 is also connected with the output end of the voltage detection circuit 101; the voltage detection circuit 101 is connected with the output end of the switching power supply, for dividing the output voltage of the switching power supply; the input end of the error amplification circuit 20 is connected with the output end of the current detection circuit and the output end of the current reference setting circuit 10. As can be seen from the above, the output end of the maximum output current setting circuit 102 and the output end of the voltage detection circuit 101 are connected to the first operational amplifier U1, the first operational amplifier U1 is a closed-loop structure, and due to the existence of the first diode D1, when the output end voltage of the voltage detection circuit 101 is less than the output end voltage of the maximum output current setting circuit 102, the diode is cut off, and the output end voltage of the current reference setting circuit 10 changes with the output end voltage of the voltage detection circuit 101; when the output end voltage of the voltage detection circuit 101 is greater than the output end voltage of the maximum output current setting circuit 102, the diode is turned on, and the voltages at both ends of the first operational amplification circuit are clamped to be equal, at this time, the output end voltage of the current reference setting circuit 10 is equal to the output end voltage of the maximum output current setting circuit 102. The output end of the current reference setting circuit 10 and the output end of the current detection circuit are connected to the error amplification circuit 20, and after comparing the voltage sizes of the two input ends, the error amplification circuit 20 outputs a current difference signal to the switching power supply chip to adjust the size of the output current. At this time, the maximum output current is determined by the maximum output current setting circuit 102, that is, adjusting the voltage division ratio of the maximum output current circuit can set the current value corresponding to the retracting point, and the voltage value of the retracting point is related to the voltage division ratio of the voltage detection circuit 101, and by adjusting the voltage division ratio of the voltage detection circuit 101, the voltage value corresponding to the retracting point can be accurately set. Therefore, the current reference setting circuit 10 does not contain a triode, but uses the first operational amplifier U1 and the first diode D1 to realize accurate setting of the retracting point, effectively avoiding the influence of temperature on the retracting point.

[0061] In order to adjust the voltage value corresponding to the retraction point, the utility model discloses a specific current -limiting retraction protection circuit, relative to the last embodiment, this embodiment has made further description and optimization to technical scheme. Specifically,

[0062] The voltage detection circuit 101 comprises a first resistor R1 and a second resistor R2.

[0063] The first end of the first resistor R1 is connected with the output voltage signal end of the switching power supply as the input end of the voltage detection circuit 101.

[0064] The second end of the second resistor R2 is grounded.

[0065] In the embodiment, the voltage detection circuit 101 is formed by the first resistor R1 and the second resistor R2 in series, wherein the common end of the first resistor R1 and the second resistor R2 is the output end of the voltage detection circuit 101, and the first resistor R1 and the second resistor R2 can divide the output voltage of the switching power supply; by adjusting the resistance value of the first resistor R1 and the second resistor R2, the voltage value corresponding to the retraction point can be adjusted.

[0066] As can be seen from the above, by adjusting the resistance value of the first resistor R1 and the second resistor R2, the voltage value corresponding to the retraction point can be adjusted.

[0067] In order to accurately set the current limiting value when the output voltage is zero, the utility model discloses a specific current -limiting retraction protection circuit, relative to the last embodiment, this embodiment has made further description and optimization to technical scheme. Specifically,

[0068] The voltage detection circuit 101 further comprises a third resistor R3 and a first capacitor C1.

[0069] The second end of the third resistor R3 and the first end of the first capacitor C1 are connected with the first end of the second resistor R2.

[0070] The first end of the third resistor R3 is connected with the power supply, and the second end of the first capacitor C1 is grounded.

[0071] It should be noted that when the voltage detection circuit 101 is composed of only the first resistor R1 and the second resistor R2, the current limiting value is very small when the output voltage is zero, which is not conducive to the start of the power supply.

[0072] In the embodiment of the present application, when the output voltage is 0, the first resistor R1 and the second resistor R2 are equivalent to be connected in parallel, one end of the third resistor R3 is connected to the power supply, and the other end is connected to the second resistor R2. Therefore, the output voltage of the voltage detection circuit 101 at this time is determined by the resistance values of the first resistor R1, the second resistor R2 and the third resistor R3. By adjusting the resistance values, the voltage division value can be adjusted to accurately set the current limiting value when the output voltage is zero. It can be understood that a 15V power supply can be selected. At this time, the power supply can not only supply power to the voltage detection circuit 101, but also connect the positive power supply end of the first operational amplifier U1 to provide power for the first operational amplifier U1. It should be noted that the first capacitor C1 can stabilize the output voltage value of the voltage detection circuit 101 and increase the anti-interference capability.

[0073] As can be seen from the above, when the output voltage is zero in the voltage detection circuit 101, the voltage division value of the voltage detection circuit 101, i.e. the output voltage value of the voltage detection circuit 101, can be accurately adjusted by adjusting the resistance values of the first resistor R1, the second resistor R2 and the third resistor R3 due to the existence of the power supply. Therefore, the current limiting value when the output voltage is zero can be accurately set.

[0074] In order to accurately set the maximum output current, the utility model discloses a specific current limiting retraction protection circuit, which is further described and optimized compared with the previous embodiment. Specifically:

[0075] The maximum output current setting circuit 102 comprises a fourth resistor R4, a fifth resistor R5 and a second capacitor C2.

[0076] The first end of the fifth resistor R5 and the first end of the second capacitor C2 are connected to the second end of the fourth resistor R4, and the common end thereof is used as the output end of the maximum output current setting circuit 102.

[0077] The first end of the fourth resistor R4 is connected to the power supply, and the second end of the fifth resistor R5 and the second end of the second capacitor C2 are grounded.

[0078] In the embodiment, the maximum output current setting circuit 102 is composed of the fourth resistor R4 and the fifth resistor R5 in series, and the above-mentioned power supply can still provide power for the maximum output current setting circuit 102. It can be understood that the fourth resistor R4 and the fifth resistor R5 form a voltage division circuit, and the resistance value of the resistor can change the voltage division value. The voltage division value is the output value of the maximum output current setting circuit 102. At this time, the maximum current reference signal that can be output by the current reference setting circuit 10 is determined by the voltage division value, that is, the resistance value of the resistor can accurately control the maximum current limiting point.

[0079] From the above, the fourth resistor R4 and the fifth resistor R5 constitute a voltage dividing circuit, and the voltage dividing value can be accurately set by adjusting the resistance value of the resistor. Since the maximum output terminal voltage of the current reference setting circuit 10 is determined by the output terminal voltage of the maximum output current setting circuit 102, the maximum output current can be accurately adjusted by accurately adjusting the voltage dividing value of the resistor.

[0080] In order to detect the error between the output terminal voltage of the current detection circuit and the output terminal voltage of the current reference setting circuit 10, the utility model embodiment discloses a specific current limiting retraction protection circuit, which is further described and optimized compared with the previous embodiment. Specifically:

[0081] The error amplifier circuit 20 is a current loop error amplifier, which comprises a second operational amplifier U2, a sixth resistor R6, a seventh resistor R7, a third capacitor C3 and a fourth capacitor C4.

[0082] The second end of the sixth resistor R6 and the first end of the seventh resistor R7 are connected with the inverting output end of the second operational amplifier U2; the first end of the third capacitor C3 is connected with the output end of the second operational amplifier U2, and the common end thereof serves as the output end of the error amplifier circuit 20; the non-inverting input end of the second operational amplifier U2 serves as the second end of the error amplifier circuit 20 and is connected with the output end of the current reference setting circuit 10; the second end of the fourth capacitor C4 is connected with the positive power supply end of the second operational amplifier U2.

[0083] The first end of the fourth capacitor C4 is grounded.

[0084] The second end of the third capacitor C3 is connected with the first end of the sixth resistor R6.

[0085] The second end of the seventh resistor R7 serves as the first end of the error amplifier circuit 20 and is connected with the output end of the current detection circuit; the input end of the error amplifier circuit 20 comprises the first end of the error amplifier circuit 20 and the second end of the error amplifier circuit 20.

[0086] In the embodiment, the error amplifier circuit 20 is a current loop error amplifier composed of an operational amplifier. The current loop error amplifier is an amplifier used in power management and control circuit, which can amplify the direct error between the feedback signal and the target signal in the current control loop, so as to realize accurate control of the output current. It can be understood that the above-mentioned feedback signal is the corresponding voltage signal converted from the output current by the current detection circuit, and the target signal is the output terminal voltage of the current reference setting circuit 10.

[0087] In this embodiment, the inverting input terminal and the non-inverting input terminal of the second operational amplifier U2 are connected with the output terminal of the current detection circuit and the output terminal of the current reference setting circuit 10 respectively, the second operational amplifier U2 can compare the voltage values of the inverting input terminal and the non-inverting input terminal to the error signal, and amplify it, and the gain effect is determined by the impedance ratio of the sixth resistor R6 and the seventh resistor R7, higher gain effect can make the control module more sensitive to the error signal, and can quickly respond.

[0088] It should be noted that the current loop error amplifier is a closed loop system, the voltage signal corresponding to the output current can be returned to the input terminal of the second operational amplifier U2 and compared with the output voltage of the current reference setting circuit 10, which ensures the self-regulating mechanism of the system and makes the output current stable. At the same time, the third capacitor C3 in the second operational amplifier U2 can be used as a phase compensation element to avoid high frequency oscillation.

[0089] As can be seen from the above, the current error amplifier can compare the output voltage of the current detection circuit with the output voltage of the current reference setting circuit 10 through the second operational amplifier U2, obtain the error signal between the two, and output the amplified error signal to the control module.

[0090] In order to determine whether the current limiting retracting circuit outputs the amplified error signal to the switching power supply, the utility model discloses a specific current limiting retracting protection circuit, compared with the last embodiment, the technical scheme is further explained and optimized. Specifically:

[0091] Further comprising: a second diode D2 and a light emitting diode;

[0092] The cathode of the second diode D2 is connected with the output terminal of the error amplifier circuit 20, for controlling the output of the error signal;

[0093] The anode of the second diode D2 is connected with the cathode of the light emitting diode.

[0094] It can be understood that the output voltage of the current reference setting circuit 10 can determine the current limiting point of the switching power supply, so the value of the current limiting point is related to the size of the output voltage of the switching power supply, and because the current limiting retracting protection circuit is used to reduce the output current when the output short circuit of the switching power supply occurs, that is, when the output current of the switching power supply is greater than the current limiting point, so as to protect the elements in the switching power supply from being damaged, therefore, the error amplifier circuit 20 only needs to output the error signal to the switching power supply when the output current is greater than the current limiting point. Figure 1As shown, the output end of the second operational amplifier U2 is connected with the cathode of the second diode D2, when the output current is less than the current limiting point, the potential of the output end of the error amplifier is pulled up, the second diode D2 is not conducted, when the output current is greater than the maximum output current, the potential of the output end of the error amplifier is pulled down, the second diode D2 is conducted, therefore, only when the output current is greater than the current limiting point, the error signal output by the error amplification circuit 20 is output to the switching power supply.

[0095] It should be noted that the regulation of the switching power supply may not only include the current limiting retracting protection circuit for regulating the output current, but also include the circuit for regulating the output voltage, in order to clarify which circuit plays a role in regulating the switching power supply, an LED is added, the cathode of the LED is connected with the anode of the second diode D2, therefore, the LED emits light only when the second diode D2 is conducted.

[0096] As can be seen from the above, only when the output current is greater than the current limiting point, that is, the output current needs to be regulated, the second diode D2 is conducted, the amplified error signal is output, at this time the LED emits light; when the output current is less than the current limiting point, the second diode D2 is not conducted, the LED does not emit light, therefore, whether the LED emits light can determine whether the current limiting retracting circuit outputs the amplified error signal to the switching power supply.

[0097] In order to convert the output current into a corresponding voltage signal, the utility model discloses a specific current limiting retracting protection circuit, relative to the last embodiment, the embodiment has made further explanation and optimization to the technical scheme.Specifically:

[0098] The current detection circuit includes a Hall current sensor;

[0099] The input end of the Hall current sensor is connected with the output current signal end of the switching power supply as the input end of the current detection circuit, and the output end of the Hall current sensor is connected with the first end of the error amplification circuit 20 as the output end of the current reference setting circuit 10.

[0100] In the embodiment, the Hall current sensor is connected with the output current signal end of the switching power supply as the current detection circuit and the first end of the error amplification circuit 20.In the Hall current sensor, the output current generates a magnetic field in the magnetic core, the magnetic field is inducted by the Hall device, a Hall voltage proportional to the output current is generated, and finally a voltage signal related to the output current is output through the amplification circuit and the like.

[0101] As can be seen from the above, based on the Hall effect, the Hall current sensor can convert the output current into a Hall voltage proportional to the output current, so that the current detection circuit can convert the output current into a corresponding voltage signal.

[0102] In order to ensure the stable output of the first operational amplifier U1, the utility model discloses a specific current -limiting retraction protection circuit, relative to the last embodiment, the embodiment has made further description and optimization to the technical scheme.

[0103] The current reference setting circuit 10 further comprises a fifth capacitor C5.

[0104] The first end of the fifth capacitor C5 is grounded, and the second end of the fifth capacitor C5 is connected with the positive power supply end of the first operational amplifier U1.

[0105] In the embodiment, the fifth capacitor C5 is connected with the positive power supply end of the first operational amplifier U1 and can be used as a decoupling resistor to form a low impedance path between the power supply and the ground, so that high-frequency noise and interference signals are more likely to flow to the ground rather than entering the power input of the operational amplifier. This is particularly important in high-frequency or noise-sensitive circuits and can effectively improve the anti-interference ability of the circuit. In addition, the fifth capacitor C5 can also be used as a shielding element to reduce electromagnetic interference on the power line from entering the operational amplifier circuit and enhance the anti-electromagnetic interference ability of the circuit.

[0106] As can be seen from the above, the fifth capacitor C5 can be used as a decoupling resistor and a shielding element to improve the anti-interference ability of the first operational amplifier U1 and ensure the stable output of the first operational amplifier U1.

[0107] In order to ensure the normal work of the first operational amplifier U1, the utility model discloses a specific current -limiting retraction protection circuit, relative to the last embodiment, the embodiment has made further description and optimization to the technical scheme.

[0108] The current reference setting circuit 10 further comprises an eighth resistor R8.

[0109] The first end of the eighth resistor R8 is connected with the inverting input end of the first operational amplifier U1, and the second end of the eighth resistor R8 is connected with the output end of the voltage detection circuit 101.

[0110] In the embodiment, connecting the eighth resistor R8 with the inverting input end of the first operational amplifier U1 can limit the current entering the first operational amplifier U1, and in addition, the eighth resistor R8 can also work together with the parasitic capacitor in the first operational amplifier U1 to form a low-pass filtering effect to suppress high-frequency signals.

[0111] As can be seen from the above, the eighth resistor R8 limits the current and realizes the low-pass filtering effect with the parasitic capacitor, which avoids circuit damage caused by excessive input current and suppresses high-frequency signals to improve the stability of the circuit and ensure the normal work of the first operational amplifier U1.

[0112] Based on the above embodiment, the utility model discloses an output short circuit protection device, including the current -limiting retracting protection circuit of above. Because output short circuit protection device contains the current -limiting retracting protection circuit of above, therefore it also has with the same technical effect of current -limiting retracting protection circuit of above.

[0113] The above description of disclosed embodiments enables one skilled in the art to make or use the utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the utility model. Thus, the utility model is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A current-limiting feedback protection circuit, characterized in that, include: The system includes a current detection circuit, a current reference setting circuit, and an error amplifier circuit; wherein the current reference setting circuit includes a first operational amplifier, a first diode, a voltage detection circuit, and a maximum output current setting circuit. The anode of the first diode is connected to the inverting input of the first operational amplifier, and its common terminal serves as the output of the current reference setting circuit, used to output a current reference signal to the error amplifier circuit. The cathode of the first diode is connected to the output of the first operational amplifier. The non-inverting input of the first operational amplifier is connected to the output of the maximum output current setting circuit, used to input a voltage reference signal. The input of the voltage detection circuit is connected to the output of the switching power supply, used to divide the output voltage of the switching power supply. The output of the voltage detection circuit is connected to the inverting input of the first operational amplifier. The input terminal of the current detection circuit is connected to the output current signal terminal of the switching power supply, and is used to convert the output current of the switching power supply into a corresponding voltage signal and output it to the error amplifier circuit. The input terminal of the error amplifier circuit is connected to the output terminal of the current detection circuit and the output terminal of the current reference setting circuit, and is used to output an error signal.

2. The current-limiting and feedback protection circuit according to claim 1, characterized in that, The voltage detection circuit includes: a first resistor and a second resistor; The first end of the first resistor is connected to the output end of the switching power supply as the input end of the voltage detection circuit; the second end of the first resistor is connected to the first end of the second resistor. The second terminal of the second resistor is grounded.

3. The current-limiting and feedback protection circuit according to claim 2, characterized in that, The voltage detection circuit further includes: a third resistor and a first capacitor; The second end of the third resistor and the first end of the first capacitor are connected to the first end of the second resistor; The first terminal of the third resistor is connected to the power supply; the second terminal of the first capacitor is grounded.

4. The current-limiting and feedback protection circuit according to claim 3, characterized in that, The maximum output current setting circuit includes: a fourth resistor, a fifth resistor, and a second capacitor; The first end of the fifth resistor, the first end of the second capacitor, and the second end of the fourth resistor are connected, and their common end is used as the output end of the maximum output current setting circuit. The first end of the fourth resistor is connected to the power supply; the second end of the fifth resistor is grounded to the second end of the second capacitor.

5. The current-limiting and feedback protection circuit according to claim 1, characterized in that, The error amplifier circuit is a current loop error amplifier, which includes: a second operational amplifier, a sixth resistor, a seventh resistor, a third capacitor, and a fourth capacitor; The second end of the sixth resistor and the first end of the seventh resistor are connected to the inverting input of the second operational amplifier; the first end of the third capacitor is connected to the output of the second operational amplifier, and its common end serves as the output of the error amplifier circuit; the non-inverting input of the second operational amplifier serves as the second end of the error amplifier circuit and is connected to the output of the current reference setting circuit; the second end of the fourth capacitor is connected to the positive power supply of the second operational amplifier. The first terminal of the fourth capacitor is grounded. The second terminal of the third capacitor is connected to the first terminal of the sixth resistor; The second end of the seventh resistor is connected to the output end of the current detection circuit as the first end of the error amplifier circuit; the input end of the error amplifier circuit includes the first end and the second end of the error amplifier circuit.

6. The current-limiting and feedback protection circuit according to claim 5, characterized in that, Also includes: Second diode and light-emitting diode; The cathode of the second diode is connected to the output terminal of the error amplifier circuit to control the output of the error signal; The anode of the second diode is connected to the cathode of the light-emitting diode.

7. The current-limiting and feedback protection circuit according to claim 1, characterized in that, The current detection circuit includes a Hall current sensor; The input terminal of the Hall current sensor is connected to the output current signal terminal of the switching power supply as the input terminal of the current detection circuit, and the output terminal of the Hall current sensor is connected to the first terminal of the error amplifier circuit as the output terminal of the current reference setting circuit.

8. The current-limiting and feedback protection circuit according to claim 1, characterized in that, The current reference setting circuit also includes a fifth capacitor; The first terminal of the fifth capacitor is grounded, and the second terminal of the fifth capacitor is connected to the positive power supply terminal of the first operational amplifier.

9. The current-limiting and feedback protection circuit according to claim 1, characterized in that, The current reference setting circuit also includes an eighth resistor; The first end of the eighth resistor is connected to the inverting input of the first operational amplifier, and the second end of the eighth resistor is connected to the output of the voltage detection circuit.

10. An output short-circuit protection device, characterized in that, Includes the current limiting and retraction protection circuit as described in any one of claims 1 to 9.

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