Short circuit protection circuit and switching power supply

Abstract

The application discloses a short-circuit protection circuit and a switching power supply. The short-circuit protection circuit comprises a first resistor and a detection circuit. One end of the first resistor is used for connecting one end of an output capacitor, and the other end of the first resistor is used for connecting an output ground of the switching power supply. An input end of the detection circuit is connected with one end of the first resistor, and an output end of the detection circuit is used for connecting a short-circuit protection trigger end of a control circuit. The detection circuit is used for detecting a first voltage signal generated at two ends of the first resistor, and outputting a second voltage signal after processing the first voltage signal. The second voltage signal is used for being sent to the control circuit, and the power converter is controlled by the control circuit to stop working when the second voltage signal is less than a set value. The application can realize quick and lossless detection of short-circuit protection, and improve the short-circuit protection speed of the switching power supply and the whole machine efficiency.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a short-circuit protection circuit and a switching power supply. Background Technology

[0002] With the increasing maturity of technology, switching power supplies, as voltage conversion circuits, have been widely used in military and civilian electronic equipment. When the output of a switching power supply exceeds its rated load or is short-circuited, it can be damaged, causing the power system to malfunction. Therefore, when designing switching power supplies, we must incorporate short-circuit protection to prevent damage caused by overload or short circuits.

[0003] like Figure 1 The diagram described is a conventional switching power supply schematic with short-circuit protection. It illustrates a scheme for triggering short-circuit protection by detecting a drop in output voltage to a threshold voltage. The circuit includes a power converter 101, an output capacitor C1, a control circuit 102, and a short-circuit protection circuit composed of resistors R1 and R2 and a detection circuit 103. The power converter 101 performs input-output power conversion; the output capacitor C1 is connected between the output terminal of the switching power supply and the output ground for output filtering; the control circuit 102 is connected to the power converter 101 and controls the switching transistors within the power converter 101; the short-circuit protection circuit is connected to the output terminal of the switching power supply to provide output short-circuit (including overload) protection.

[0004] Figure 1 The working principle of the short-circuit protection is as follows: the output voltage of the switching power supply is sampled through the voltage divider resistors R1 and R2 connected in series with ground at the output terminal. The voltage signal UR1 at the connection point of resistors R1 and R2 can represent the magnitude of the output voltage of the switching power supply. This voltage signal is processed by the detection circuit 103 and then sent to the control circuit 102. The control circuit 102 controls the operation of the power converter 101 based on this signal, thereby realizing the short-circuit protection of the switching power supply. The drawback of this scheme is that as the output voltage increases, the value of the voltage divider resistors becomes larger, resulting in an excessive RC delay of the voltage signal UR1 after passing through the detection circuit 103. This causes the short-circuit protection to fail to respond in time, resulting in saturation of the inductor current in the transformer of the power converter 101 at the moment of short circuit.

[0005] like Figure 2The above is a schematic diagram of another conventional switching power supply with short-circuit protection function. It is a scheme that directly detects the output current to trigger short-circuit protection. The sampling resistor R1 is connected in series in the line where the output terminal of the switching power supply is located. Its working principle is that the voltage across the sampling resistor R1 is sampled by the detection circuit 103. This voltage signal can directly represent the magnitude of the output current. After the voltage signal is processed by the detection circuit 103, it is sent to the control circuit 102. The control circuit 102 controls the operation of the power converter 101 according to this signal to realize the short-circuit protection of the switching power supply. This scheme adds an extra sampling resistor in the power circuit, thus increasing the converter's own losses and reducing the converter efficiency. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a short-circuit protection circuit and a switching power supply, so as to realize rapid and non-destructive testing of short-circuit protection, thereby improving the short-circuit protection speed and overall efficiency of the switching power supply.

[0007] As a first aspect of the present invention, the technical solution of the short-circuit protection circuit is as follows:

[0008] A short-circuit protection circuit is applied to a switching power supply, the switching power supply including a power converter, an output capacitor, and a control circuit. The short-circuit protection circuit includes: a first resistor and a detection circuit; one end of the first resistor is connected to one end of the output capacitor, and the other end of the first resistor is connected to the output ground of the switching power supply; the input terminal of the detection circuit is connected to one end of the first resistor, and the output terminal of the detection circuit is connected to the short-circuit protection trigger terminal of the control circuit; the detection circuit is used to detect a first voltage signal generated across the first resistor, and after processing the first voltage signal, outputs a second voltage signal; the second voltage signal is sent to the control circuit, which controls the power converter to stop working when the second voltage signal is less than a set value.

[0009] As a first specific implementation of the detection circuit, it includes: resistors R2, R3, R4, and R5, a differential sampling circuit U1, and a comparator circuit U2; one end of resistor R2 and one end of resistor R3 are connected together to connect to the output ground of the switching power supply; the other ends of resistors R2 and R3 are simultaneously connected to the positive input terminal of the differential sampling circuit U1; one end of resistor R4 is the input terminal of the detection circuit; the other end of resistor R4 is simultaneously connected to the negative input terminal of the differential sampling circuit U1 and one end of resistor R5; the output terminal of the differential sampling circuit U1 is simultaneously connected to the other end of resistor R5 and the negative input terminal of the comparator circuit U2; the positive input terminal of the comparator circuit U2 is used to input a first reference voltage; and the output terminal of the comparator circuit U2 is the output terminal of the detection circuit.

[0010] Furthermore, the detection circuit also includes a diode D1, the output terminal of the comparator circuit U2 is connected to the cathode of the diode D1, and the anode of the diode D1 is the output terminal of the detection circuit.

[0011] As a second specific implementation of the detection circuit, it includes: a first switching transistor and a resistor R6. The control terminal of the first switching transistor is the input terminal of the detection circuit. One end of the first switching transistor is used to connect to the output ground of the switching power supply. The other end of the first switching transistor and one end of the resistor R6 are connected together to form the output terminal of the detection circuit. The other end of the resistor R6 is used to input the power supply voltage. The first switching transistor is turned on when its control terminal is negative and turned off when its control terminal is zero.

[0012] Furthermore, the detection circuit also includes a diode D1, the cathode of which is connected to the connection point between the other end of the first switching transistor and one end of the resistor R6, and the anode of the diode D1 is the output terminal of the detection circuit.

[0013] Preferably, the first switch S1 is an enhancement-mode P-MOS transistor, the gate of the enhancement-mode P-MOS transistor is the control terminal of the first switch S1, the drain of the enhancement-mode P-MOS transistor is one end of the first switch S1, and the source of the enhancement-mode P-MOS transistor is the other end of the first switch S1.

[0014] Preferably, the first switching transistor is a PNP transistor S2, the base of the PNP transistor S2 is the control terminal of the first switching transistor, the emitter of the PNP transistor S2 is one end of the first switching transistor, and the collector of the PNP transistor S2 is the other end of the first switching transistor.

[0015] A third specific implementation of the detection circuit includes: a first switching transistor, a resistor R6, and an inverter U5. The control terminal of the first switching transistor is the input terminal of the detection circuit. One end of the first switching transistor is connected to the output ground of the switching power supply. The other end of the first switching transistor is connected to one end of the resistor R6 and the input terminal of the inverter U5. The other end of the resistor R6 is used to input the power supply voltage. The output terminal of the inverter U5 is the output terminal of the detection circuit. The first switching transistor is turned on when its control terminal is at zero voltage and turned off when its control terminal is at negative voltage.

[0016] Furthermore, the detection circuit also includes a diode D1, the output terminal of the inverter U5 is connected to the cathode of the diode D1, and the anode of the diode D1 is the output terminal of the detection circuit.

[0017] Preferably, the first switch S1 is a depletion-type N-MOS transistor, the gate of the depletion-type N-MOS transistor is the control terminal of the first switch S1, the drain of the depletion-type P-MOS transistor is one end of the first switch S1, and the source of the depletion-type P-MOS transistor is the other end of the first switch S1.

[0018] As a second aspect of the present invention, the technical solution of the provided switching power supply is as follows:

[0019] A switching power supply includes a power converter, an output capacitor, a control circuit, and a short-circuit protection circuit as described in any of the first aspects above. A first resistor is connected in series in the line where the output capacitor and the output ground of the switching power supply are located. The input terminal of the detection circuit is connected to one end of the first resistor, and the output terminal of the detection circuit is connected to the short-circuit protection trigger terminal of the control circuit.

[0020] Preferably, the control circuit includes: resistors R7, R8, and R9, capacitors C2 and C3, an error amplifier U3, and a comparator circuit U4; one end of resistor R7 is connected to the output terminal of the switching power supply, and the other end of resistor R7 is simultaneously connected to one end of resistor R8, one end of resistor R9, one end of capacitor C3, and the negative input terminal of the error amplifier U3; the other end of resistor R9 is connected to one end of capacitor C2; the positive first input terminal of the error amplifier U3 is used to input a second reference voltage; the positive second input terminal of the error amplifier U3 is the SS port of the control circuit 102; the output terminal of the error amplifier U3, the other end of capacitor C2, the other end of capacitor C3, and the negative input terminal of the comparator circuit U4 are connected together to form the Comp port of the control circuit 102; the positive input terminal of the comparator circuit U4 is used to input a triangular wave signal; the enable terminal of the comparator circuit U4 is the EN port of the control circuit 102; and the output terminal of the comparator circuit U4 is the GATE port of the control circuit 102.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention connects a first resistor in series in the line between the output capacitor and the output ground of the switching power supply to achieve short-circuit protection detection. At the moment of short circuit, the output capacitor discharges instantaneously, the short-circuit current flows through the first resistor, and a first voltage signal is generated across the first resistor. Compared with the existing technology that samples the output voltage or output current, this invention achieves fast and non-destructive detection, improving the short-circuit protection speed and overall efficiency of the switching power supply. Attached Figure Description

[0023] Figure 1 The schematic diagram of a conventional switching power supply with short-circuit protection function in existing technology;

[0024] Figure 2 This is a schematic diagram of another conventional switching power supply with short-circuit protection function in the existing technology;

[0025] Figure 3 This is a block diagram of a switching power supply using the short-circuit protection circuit of the present invention;

[0026] Figure 4 for Figure 3 A schematic diagram of the ports of the control circuit 102 in the diagram;

[0027] Figure 5 for Figure 3 The first circuit diagram of the detection circuit in the image;

[0028] Figure 6 In order to be in Figure 5 Based on this, a circuit diagram of a control circuit has been added;

[0029] Figure 7 for Figure 3 The second circuit diagram of the detection circuit in the image;

[0030] Figure 8 In order to be in Figure 7 Based on this, a circuit diagram of a control circuit has been added;

[0031] Figure 9 for Figure 3 The third circuit diagram of the detection circuit in the middle;

[0032] Figure 10 for Figure 3 The fourth circuit diagram of the detection circuit in the middle;

[0033] Figure 11 for Figure 3 The fifth circuit diagram of the detection circuit in the image. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0035] It should be noted that the terms "comprising" and "having" and any variations thereof described in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, including a series of components, unit circuits or control timings is not necessarily limited to those components, unit circuits or control timings that are explicitly listed, but may include components, unit circuits or control timings that are not explicitly listed or that are inherent to these circuits.

[0036] Furthermore, unless otherwise specified, the embodiments and features described in this application may be combined with each other.

[0037] It should be understood that, in the specification and claims, when an element is described as being "connected" to another element, that element may be "directly connected" to that other element or "connected" to that other element through a third element; when a step is described as being connected to another step, that step may be connected directly to that other step or connected to that other step through a third step.

[0038] The inventive concept of this application is to connect a first resistor in series between the output capacitor and the output ground of the switching power supply. When the switching power supply output is short-circuited (including overload), the output capacitor discharges instantaneously, the short-circuit current flows through the first resistor, and a first voltage signal is generated across the first resistor. After the first voltage signal is processed by the detection circuit, a second voltage signal is output and sent to the control circuit to control the power converter to stop working when the second voltage signal is less than a set value, thus completing the short-circuit protection.

[0039] Figure 3 The diagram shows a switching power supply using the short-circuit protection circuit of the present invention. The switching power supply includes a power converter 101, an output capacitor C1, and a control circuit 102. The short-circuit protection circuit includes a first resistor R1 and a detection circuit 103. One end of the first resistor R1 is connected to one end of the output capacitor C1, and the other end of the first resistor R1 is connected to the output ground of the switching power supply. The input terminal of the detection circuit 103 is connected to one end of the first resistor R1, and the output terminal of the detection circuit 103 is connected to the short-circuit protection trigger terminal of the control circuit 102. The detection circuit 103 is used to detect a first voltage signal generated across the first resistor R1, and after processing the first voltage signal, outputs a second voltage signal. The second voltage signal is sent to the control circuit 102, which controls the power converter 101 to stop working when the second voltage signal is less than a set value.

[0040] Figure 3In the circuit shown, when the switching power supply output is short-circuited (including overload), the output capacitor C1 will discharge, and a reverse voltage difference (i.e., the first voltage signal) will be generated across the first resistor R1. The detection circuit 103 detects and processes this signal and sends it to the control circuit 102 for short-circuit protection control. When the switching power supply is working normally, no current flows through the first resistor R1. Only at the moment of output short circuit (including overload), the short-circuit current generates a reverse voltage difference across the first resistor R1, thereby realizing fast and non-destructive detection of short circuits and improving the overall efficiency of the switching power supply.

[0041] In this circuit, the short-circuit protection trigger terminal of the control circuit 102 compares the second voltage signal after receiving it. When the second voltage signal is less than a set value, the control circuit 102 stops outputting the drive wave, and the switching transistors in the power converter 101 cannot switch between on and off, thus the power converter 101 stops working. Figure 4 for Figure 3 The port diagram of the control circuit 102 is shown below. The functional ports related to this invention are as follows:

[0042] GATE port: This is the control signal output port, used to output a drive wave to drive the switching transistor to switch between on and off. There can be multiple such ports, each driving a different switching transistor.

[0043] EN port: Even if the signal on this port is valid (either high or low), the GATE port will output a drive wave. Otherwise, the GATE port will not output a drive wave. Therefore, a second voltage signal can be input into this port to control whether the GATE port outputs a drive wave, thereby achieving short-circuit protection. Thus, this port can be used as a short-circuit protection trigger terminal for the control circuit.

[0044] Comp port: This is the current compensation control port, which is connected to the output of the error amplifier inside the control circuit 102. Through this port, external compensation components can be connected to perform loop compensation, thereby improving the stability of the switching power supply output voltage. Since this port is also connected to one input of the comparator inside the control circuit 102, a second voltage signal can be input to this port to control whether the GATE port outputs a drive wave to achieve short-circuit protection. Thus, this port can also be used as the short-circuit protection trigger terminal of the control circuit.

[0045] SS port: This is the startup delay control port. By connecting a capacitor between this port and ground, the soft-start time of the switching power supply can be controlled. Specifically, when the switching power supply is powered on, the capacitor can be charged through a current source, thereby obtaining a slowly rising signal at the SS port. This slowly rising signal serves as a reference voltage for the error amplifier inside the control circuit 102, which can control the duty cycle of the drive wave output by the GATE port, thus controlling the soft-start time of the switching power supply. Since the signal at the SS port serves as a reference voltage for the error amplifier inside the control circuit 102, a second voltage signal can also be input to this port to control whether the GATE port outputs a drive wave, achieving short-circuit protection. Therefore, this port can also be used as the short-circuit protection trigger terminal of the control circuit.

[0046] It should be noted that the control circuit 102 described above can have three ports as short-circuit protection trigger terminals. Those skilled in the art can design and select which port to use as the short-circuit protection trigger terminal of the control circuit 102 according to the actual situation. Some specific configuration schemes will also be given below for reference.

[0047] Furthermore, the control circuit 102 can be implemented using discrete components or by designing a dedicated integrated circuit. For example, the LM5118 control chip from TI can be used as the control circuit 102 of this invention, where the EN port corresponds to the EN port described above, the SS port corresponds to the SS port described above, the Comp port corresponds to the Comp port described above, and the HO / LI port corresponds to the GATE port described above. Similarly, the RT6190 control chip from RICHTEK can also be used as the control circuit 102 of this invention, where the EN port corresponds to the EN port described above, the SS port corresponds to the SS port described above, the CompV / CompI port corresponds to the Comp port described above, and the LDRVI / LDRV2 / HDRV1 / HDRV2 ports correspond to the GATE port described above. It should be noted that those skilled in the art can choose the specific implementation method of the control circuit 102 according to the actual situation, and this invention does not impose any limitations.

[0048] Figure 5 for Figure 3The first circuit diagram of the detection circuit includes resistors R2, R3, R4, and R5, a differential sampling circuit U1, a comparator circuit U2, and a diode D1. One end of resistor R2 and one end of resistor R3 are connected together to connect to the output ground of the switching power supply. The other ends of resistors R2 and R3 are connected to the positive input terminal of the differential sampling circuit U1. One end of resistor R4 is the input terminal of the detection circuit. The other end of resistor R4 is connected to the negative input terminal of the differential sampling circuit U1 and one end of resistor R5. The output terminal of the differential sampling circuit U1 is connected to the other end of resistor R5 and the negative input terminal of the comparator circuit U2. The positive input terminal of the comparator circuit U2 is used to input the first reference voltage. The output terminal of the comparator circuit U2 is connected to the cathode of diode D1. The anode of diode D1 is the output terminal of the detection circuit.

[0049] Figure 6 In order to be in Figure 5 Based on the above, a control circuit diagram is added. The control circuit 102 includes resistors R7, R8, and R9, capacitors C2 and C3, an error amplifier U3, and a comparator U4. One end of resistor R7 is connected to the output terminal of the switching power supply. The other end of resistor R7 is connected to one end of resistor R8, one end of resistor R9, one end of capacitor C3, and the negative input terminal of error amplifier U3. The other end of resistor R9 is connected to one end of capacitor C2. The first positive input terminal of error amplifier U3 is used to input the second reference voltage. The second positive input terminal of error amplifier U3 is the SS port of control circuit 102. The output terminal of error amplifier U3, the other end of capacitor C2, the other end of capacitor C3, and the negative input terminal of comparator U4 are connected together to form the Comp port of control circuit 102. The positive input terminal of comparator U4 is used to input a triangular wave signal. The enable terminal of comparator U4 is the EN port of control circuit 102. The output terminal of comparator U4 is the GATE port of control circuit 102.

[0050] Figure 6 When the switching power supply is working normally, the voltage across the first resistor R1 is UR1=0, meaning the first voltage signal is 0. Figure 6When the cathode of diode D1 is at a high level, i.e., the second voltage signal is at a high level, diode D1 is reverse clamped. The output signal of error amplifier U3 in control circuit 102 is compared with the triangular wave signal in comparator circuit U4, and comparator circuit U4 outputs a PWM signal. When a short circuit (including overload) occurs at the output of the switching power supply, output capacitor C1 discharges instantaneously, and a negative voltage is generated across the first resistor R1. This negative voltage is the first voltage signal. Detection circuit 103 detects this signal, causing the negative terminal of diode D1 to be pulled low, i.e., the second voltage signal is at a low level. Diode D1 conducts, thereby pulling low the output terminal of error amplifier U3 in control circuit 102. Comparator circuit U4 in control circuit 102 outputs a low level, and the power switch in power converter 101 is turned off, thus power converter 101 stops working, achieving short circuit protection.

[0051] It should be noted that, Figure 6 The Comp port of the control circuit 102 serves as its short-circuit protection trigger terminal. The voltage signal output by the voltage detection circuit 103 is sent to the Comp port of the control circuit 102. Short-circuit protection is achieved through the voltage signal input to the negative input terminal of the interference comparator circuit U4. Figure 6 Equivalent substitution of the circuit can remove Figure 6 In the voltage detection circuit 103, diode D1 directly outputs a second voltage signal from the comparator circuit U2. At this time, the second voltage signal needs to be sent to the EN port or SS port of the control circuit 102. That is, the EN port or SS port of the control circuit 102 is its short-circuit protection trigger terminal, which can also realize the short-circuit protection function.

[0052] Figure 7 for Figure 3 The second circuit diagram of the detection circuit 103 includes: a first switch S1 and a resistor R6. The control terminal of the first switch S1 is the input terminal of the detection circuit. One end of the first switch S1 is used to connect to the output ground of the switching power supply. The other end of the first switch S1 and one end of the resistor R6 are connected together to serve as the output terminal of the detection circuit 103. The other end of the resistor R6 is used to input the power supply voltage.

[0053] In this circuit, the first switch S1 is an enhancement-mode P-MOS transistor. The gate of the enhancement-mode P-MOS transistor is the control terminal of the first switch S1. The drain of the enhancement-mode P-MOS transistor is one end of the first switch S1, and the source of the enhancement-mode P-MOS transistor is the other end of the first switch S1.

[0054] Figure 8 In order to be in Figure 7 Based on this, a circuit diagram of a control circuit has been added, wherein the internal structure of the control circuit 102 is similar to... Figure 6 The internal structure of the control circuits in them is the same. Figure 8The EN port of the control circuit 102 in the circuit is its short-circuit protection trigger terminal, and the output terminal of the detection circuit 103 needs to be connected to the EN port of the control circuit 102.

[0055] Figure 8 The logic AND of the second voltage signal output by the detection circuit 103 in the circuit Figure 5 Similarly, when the voltage UR1 across the first resistor R1 is 0, the comparator circuit U4 outputs a PWM signal; when a negative voltage is generated across the first resistor R1, the comparator circuit U4 outputs a low level. Specifically, Figure 8 When the switching power supply is working normally, the voltage across the first resistor R1 is UR1=0, meaning the first voltage signal is 0. Figure 7 When the drain of the enhancement-mode P-MOS is high, i.e., the second voltage signal is high, the enable terminal of the comparator circuit U4 in the control circuit 102 is high, the output signal of the error amplifier U3 in the control circuit 102 is compared with the triangular wave signal in the comparator circuit U4, and the comparator circuit U4 outputs a PWM signal. When a short circuit (including overload) occurs at the output of the switching power supply, the output capacitor C1 discharges instantaneously, and a negative voltage is generated across the first resistor R1. This negative voltage is the first voltage signal. The detection circuit 103 detects this signal, which pulls the drain of the enhancement-mode P-MOS low, i.e., the second voltage signal is low, thereby pulling down the enable terminal of the comparator circuit U4 in the control circuit 102. The comparator circuit U4 in the control circuit 102 outputs a low level, the power switch in the power converter 101 is turned off, and the power converter 101 stops working, thus achieving short circuit protection.

[0056] It should be noted that, Figure 8 The EN port of the control circuit 102 is its short-circuit protection trigger terminal. The voltage signal output by the voltage detection circuit 103 is sent to the EN port of the control circuit 102. The short-circuit protection is achieved by using the voltage signal input to the enable terminal of the interference comparator circuit U4. Figure 6 Equivalent replacement of circuit: Alternatively, one can choose... Figure 8 The SS port of the control circuit 102 is its short-circuit protection trigger terminal. At this time, the voltage signal output by the voltage detection circuit 103 needs to be sent to the SS port of the control circuit 102; or in Figure 8 A diode D1 is connected at the connection point between the other end of the switching transistor S1 and one end of the resistor R6 in the voltage detection circuit 103. For details, please refer to... Figure 9 The anode of diode D1 is connected to the junction of the other end of switch S1 and one end of resistor R6. The cathode of diode D1 serves as the output terminal of detection circuit 103, and a second voltage signal is output from diode D1. At this time, the logic AND of the second voltage signal... Figure 7The logic of the second signal is the same, that is, when a negative voltage is generated across the first resistor R1, the comparator circuit U4 outputs a PWM signal; when the voltage across the first resistor R1 UR1=0, the comparator circuit U4 outputs a low level. At this time, the second voltage signal needs to be sent to the Comp port of the control circuit 102. The Comp port of the control circuit 102 is its short-circuit protection trigger terminal. Such a circuit modification can also achieve the short-circuit protection function.

[0057] Figure 10 for Figure 3 The fourth circuit diagram of the detection circuit in the middle, and Figure 9 The difference is that the first switching transistor is a PNP transistor S2, the base of the PNP transistor S2 is the control terminal of the first switching transistor, the emitter of the PNP transistor S2 is one end of the first switching transistor, and the collector of the PNP transistor S2 is the other end of the first switching transistor. Figure 10 The output of the detection circuit needs to be connected to the Comp port of the control circuit 102, meaning the Comp port of the control circuit 102 is its short-circuit protection trigger terminal. When removed... Figure 10 When diode D1 is in the middle, Figure 10 The output of the detection circuit needs to be connected to the EN port or SS port of the control circuit 102, that is, the EN port or SS port of the control circuit 102 is its short-circuit protection trigger terminal.

[0058] Figure 11 for Figure 3 The fourth circuit diagram of the detection circuit in the middle, and Figure 9 The difference lies in that the first switch S1 is a depletion-type N-MOS transistor, and the detection circuit also includes an inverter U5. The input terminal of the inverter U5 is connected to the connection point between the other end of the switch S1 and one end of the resistor R6. The output terminal of the inverter U5 is connected to the anode of the diode D1. The gate of the depletion-type N-MOS transistor is the control terminal of the first switch S1. The drain of the depletion-type N-MOS transistor is one end of the first switch S1, and the source of the depletion-type N-MOS transistor is the other end of the first switch S1. Figure 11 The output of the detection circuit needs to be connected to the Comp port of the control circuit 102, meaning the Comp port of the control circuit 102 is its short-circuit protection trigger terminal. When removed... Figure 11 When diode D1 is in the middle, Figure 11 The output of the detection circuit needs to be connected to the EN port or SS port of the control circuit 102, that is, the EN port or SS port of the control circuit 102 is its short-circuit protection trigger terminal.

[0059] It should be noted that the above are merely preferred embodiments of the present invention. It should be pointed out that the above preferred embodiments should not be considered as limitations on the present invention, and it should be understood that the present invention can be applied to other, more extensive areas. Based on the above description of the present invention, and utilizing ordinary technical knowledge and conventional methods in the art, the present invention can be modified, substituted, or altered in various other forms without departing from the basic technical concept described above. All such modifications, substitutions, or alterations fall within the scope of protection of the present invention.

Claims

1. A short-circuit protection circuit applied to a switching power supply, the switching power supply comprising a power converter, an output capacitor, and a control circuit, characterized in that, The short-circuit protection circuit includes: a first resistor and a detection circuit. One end of the first resistor is connected to one end of the output capacitor, and the other end of the first resistor is connected to the output ground of the switching power supply. The input end of the detection circuit is connected to one end of the first resistor, and the output end of the detection circuit is connected to the short-circuit protection trigger end of the control circuit. The detection circuit detects a first voltage signal generated across the first resistor and processes the first voltage signal to output a second voltage signal. The second voltage signal is sent to the control circuit, which controls the power converter to stop working when the second voltage signal is less than a set value. The detection circuit includes one of the following structures: Structure 1: The detection circuit includes: resistors R2, R3, R4, and R5; a differential sampling circuit U1; and a comparator circuit U2. One end of resistor R2 and one end of resistor R3 are connected together to the output ground of the switching power supply. The other ends of resistors R2 and R3 are simultaneously connected to the positive input terminal of the differential sampling circuit U1. One end of resistor R4 is the input terminal of the detection circuit. The other end of resistor R4 is simultaneously connected to the negative input terminal of the differential sampling circuit U1 and one end of resistor R5. The output terminal of the differential sampling circuit U1 is simultaneously connected to the other end of resistor R5 and the negative input terminal of the comparator circuit U2. The positive input terminal of the comparator circuit U2 is used to input a first reference voltage. The output terminal of the comparator circuit U2 is the output terminal of the detection circuit. Structure 2, the detection circuit includes: a first switching transistor and a resistor R6. The control terminal of the first switching transistor is the input terminal of the detection circuit. One end of the first switching transistor is used to connect to the output ground of the switching power supply. The other end of the first switching transistor and one end of the resistor R6 are connected together to form the output terminal of the detection circuit. The other end of the resistor R6 is used to input the power supply voltage. The first switching transistor is turned on when its control terminal is negative and turned off when its control terminal is zero. Structure 3, the detection circuit includes: a first switching transistor, a resistor R6, and an inverter U5. The control terminal of the first switching transistor is the input terminal of the detection circuit. One end of the first switching transistor is connected to the output ground of the switching power supply. The other end of the first switching transistor is connected to one end of the resistor R6 and the input terminal of the inverter U5. The other end of the resistor R6 is used to input the power supply voltage. The output terminal of the inverter U5 is the output terminal of the detection circuit. The first switching transistor is turned on when its control terminal is at zero voltage and turned off when its control terminal is at negative voltage.

2. The short-circuit protection circuit according to claim 1, characterized in that, When the detection circuit is structure one, the detection circuit further includes a diode D1, the output terminal of the comparator circuit U2 is connected to the cathode of the diode D1, and the anode of the diode D1 is the output terminal of the detection circuit.

3. The short-circuit protection circuit according to claim 1, characterized in that, When the detection circuit is structure two, the detection circuit further includes: a diode D1, the cathode of the diode D1 is connected to the connection point between the other end of the first switching transistor and one end of the resistor R6, and the anode of the diode D1 is the output terminal of the detection circuit.

4. The short-circuit protection circuit according to claim 1, characterized in that: When the detection circuit is structure two, the first switch S1 is an enhancement-mode P-MOS transistor, the gate of the enhancement-mode P-MOS transistor is the control terminal of the first switch S1, the drain of the enhancement-mode P-MOS transistor is one end of the first switch S1, and the source of the enhancement-mode P-MOS transistor is the other end of the first switch S1.

5. The short-circuit protection circuit according to claim 1, characterized in that: When the detection circuit is structure two, the first switching transistor is a PNP transistor S2, the base of the PNP transistor S2 is the control terminal of the first switching transistor, the emitter of the PNP transistor S2 is one end of the first switching transistor, and the collector of the PNP transistor S2 is the other end of the first switching transistor.

6. The short-circuit protection circuit according to claim 1, characterized in that, When the detection circuit is structure three, the detection circuit further includes: diode D1, the output terminal of inverter U5 is connected to the cathode of diode D1, and the anode of diode D1 is the output terminal of the detection circuit.

7. The short-circuit protection circuit according to claim 1, characterized in that: When the detection circuit is structure three, the first switch S1 is a depletion-type N-MOS transistor, the gate of the depletion-type N-MOS transistor is the control terminal of the first switch S1, the drain of the depletion-type P-MOS transistor is one end of the first switch S1, and the source of the depletion-type P-MOS transistor is the other end of the first switch S1.

8. A switching power supply, characterized in that, The device includes a power converter, an output capacitor, a control circuit, and a short-circuit protection circuit as described in any one of claims 1 to 7. The first resistor is connected in series in the line where the output capacitor and the output ground of the switching power supply are located. The input terminal of the detection circuit is connected to one end of the first resistor, and the output terminal of the detection circuit is connected to the short-circuit protection trigger terminal of the control circuit.

9. The switching power supply according to claim 8, characterized in that, The control circuit includes: resistors R7, R8, and R9; capacitors C2 and C3; an error amplifier U3; and a comparator circuit U4. One end of resistor R7 is connected to the output terminal of the switching power supply. The other end of resistor R7 is connected to one end of resistor R8, one end of resistor R9, one end of capacitor C3, and the negative input terminal of error amplifier U3. The other end of resistor R9 is connected to one end of capacitor C2. The positive first input terminal of error amplifier U3 is used to input a second reference voltage. The positive second input terminal is the SS port of the control circuit (102). The output terminal of the error amplifier U3, the other end of the capacitor C2, the other end of the capacitor C3 and the negative input terminal of the comparator circuit U4 are connected together to form the Comp port of the control circuit (102). The positive input terminal of the comparator circuit U4 is used to input a triangular wave signal. The enable terminal of the comparator circuit U4 is the EN port of the control circuit (102). The output terminal of the comparator circuit U4 is the GATE port of the control circuit (102).

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