Overcurrent protection circuit and switching power supply

Abstract

The utility model relates to an overcurrent protection circuit and a switching power supply, and the overcurrent protection circuit comprises a sampling circuit which is connected with a power switch tube of the switching power supply; a first end of the overcurrent point control circuit is connected with a detection node of the switching power supply; wherein the over-current point control circuit is used for adjusting an over-current point threshold value of the switching power supply under the condition that the detection voltage of the detection node is greater than a starting threshold value of the over-current point control circuit; the control port of the controller is used for being connected with the control end of the power switch tube, the sampling port of the controller is connected with the second end of the overcurrent point control circuit and the sampling circuit, and the controller is used for controlling the on-off state of the power switch tube according to a sampling signal of the sampling circuit and a target threshold value. The over-current point threshold value of the switching power supply can be dynamically adjusted based on the magnitude of the detection voltage, so that the reliability and the protection capability of the over-current protection circuit are improved.

Description

Technical Field

[0001] The present application relates to the technical field of power supply, and in particular to an overcurrent protection circuit and a switching power supply. Background Art

[0002] Switching power supply, also known as switching power supply or switching converter, is a high-frequency power conversion device. Its function is to convert a standard voltage into the voltage or current required by the user through different forms of architecture. Switching power supply is widely used in almost all electronic devices due to its small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of today's electronic information industry.

[0003] As a power supply device for electronic products, the switching power supply must not only meet the requirements of electronic products, but also has its own protection functions, such as overcurrent protection. Once an electronic product fails, such as a short circuit on the input side or an open circuit on the output side, the switching power supply must turn off its output to protect the power switch tube and the electronic products on the output side from damage. The power management integrated circuit of a general switching power supply performs overcurrent and short-circuit protection on the power switch tube by detecting the electrical signal collected by the sampling resistor to avoid damage to the power switch tube. In related technologies, when the switching power supply inputs a high voltage, the current flowing through the sampling resistor is small, and it is difficult to reach the overcurrent protection threshold, which poses a safety hazard. Utility Model Content

[0004] Based on this, it is necessary to provide an overcurrent protection circuit and a switching power supply, which can dynamically adjust the overcurrent point threshold of the switching power supply based on the size of the detection voltage to improve the reliability and protection capability of the overcurrent protection circuit.

[0005] The present application provides an overcurrent protection circuit, comprising:

[0006] A sampling circuit, the sampling circuit is connected to a power switch tube of a switching power supply;

[0007] A current point control circuit, wherein a first end of the current point control circuit is connected to a detection node of the switching power supply; wherein the current point control circuit is used to adjust the current point threshold of the switching power supply when a detection voltage at the detection node is greater than a start threshold of the current point control circuit; wherein the detection voltage varies with an input voltage of the switching power supply;

[0008] A controller, wherein the control port of the controller is used to connect to the control end of the power switch tube, and the sampling port of the controller is respectively connected to the second end of the overcurrent point control circuit and the sampling circuit, and the controller is used to control the on-off state of the power switch tube according to the sampling signal of the sampling circuit and the target threshold; wherein the target threshold is the overcurrent point threshold or the adjusted overcurrent point threshold.

[0009] In one embodiment, the overcurrent point control circuit includes a regulating component and a switching device, wherein the first end of the regulating component is connected to the detection node of the switching power supply, the second end of the regulating component is connected to the first pole of the switching device, and the second pole of the switching device is respectively connected to the sampling port of the controller and the sampling circuit; wherein,

[0010] The switch device is used to turn on the path between the first electrode and the second electrode of the switch device when the detection voltage is greater than a turn-on threshold, wherein the turn-on threshold is related to the device type of the switch device.

[0011] In one embodiment, the adjustment component includes an adjustable resistor.

[0012] In one of the embodiments, the switching device is a Zener diode, wherein the cathode of the Zener diode is the first end of the switching device, and the anode of the Zener diode is the second end of the switching device.

[0013] In one embodiment, the switch device includes one of a triode, a MOS tube and a relay;

[0014] The overcurrent point control circuit also includes a control component and a sampling component. The sampling component is connected to the detection node and is used to collect the detection voltage of the detection node. The control component is respectively connected to the sampling component and the switching device and is used to turn on the path between the first pole and the second pole of the switching device when the detection voltage is greater than the turn-on threshold.

[0015] In one of the embodiments, the overcurrent point control circuit further includes a diode, wherein an anode of the diode is connected to the second end of the regulating component, and a cathode of the diode is connected to the first end of the switching device.

[0016] The present application also provides a switching power supply, comprising: an input circuit, a power switch tube, a first primary winding, a secondary winding and the above-mentioned overcurrent protection circuit, wherein:

[0017] The first end of the input circuit is connected to the first input end of the switching power supply, and the second end of the input circuit is connected to the second input end of the switching power supply; the input circuit includes at least one detection node, and the detection voltage of each detection node varies with the input voltage, wherein the first end of the overcurrent point control circuit in the overcurrent protection current is connected to any of the detection nodes;

[0018] The first primary winding is respectively connected to the first input end of the switching power supply and the first end of the power switch tube;

[0019] The secondary winding is connected to the output end of the switching power supply.

[0020] In one embodiment, the input circuit comprises:

[0021] A first current limiting unit, wherein a first end of the first current limiting unit serves as the detection node and is respectively connected to a first input end of the switching power supply and a first end of the overcurrent point control circuit;

[0022] A voltage stabilizing unit, wherein the first end of the voltage stabilizing unit is respectively connected to the second end of the first current limiting unit and the power port of the controller, and the second end of the voltage stabilizing unit is connected to the second input end of the switching power supply; wherein the first end of the first current limiting unit is a detection node.

[0023] In one of the embodiments, a first current limiting unit, a first end of the first current limiting unit serves as the detection node and is respectively connected to a first input end of the switching power supply and a first end of the overcurrent point control circuit;

[0024] A second current limiting unit, wherein the first end of the second current limiting unit is respectively connected to the second end of the first current limiting unit and the enable port of the controller, and the second end of the second current limiting unit is connected to the second input end of the switching power supply; the first end of the first current limiting unit is a detection node, the second end of the first current limiting unit is another detection node, and the enable port of the controller is another detection node.

[0025] In one embodiment, the first current limiting unit includes a first resistor and a second resistor, wherein the first end of the first resistor is the first end of the first current limiting unit, the second end of the first resistor is connected to the first end of the second resistor, and the second end of the second resistor is the second end of the first current limiting unit; and the second end of the first resistor is another detection node.

[0026] In one of the embodiments, the voltage stabilizing unit includes a voltage stabilizing diode, a cathode of the voltage stabilizing diode is a first end of the voltage stabilizing unit, and an anode of the voltage stabilizing diode is a second end of the voltage stabilizing unit.

[0027] In one embodiment, the second current limiting unit includes a third resistor, a first end of the third resistor is the first end of the second current limiting unit, and a second end of the third resistor is the second end of the second current limiting unit.

[0028] The overcurrent protection circuit and the switching power supply provided in this embodiment include a sampling circuit, a current point control circuit and a controller, wherein the sampling circuit is connected to the power switch tube, the first end of the current point control circuit is connected to the detection node of the switching power supply, the control port of the controller is connected to the control end of the power switch tube, the sampling port of the controller is respectively connected to the second end of the current point control circuit and the sampling circuit, the current point control circuit is used to adjust the current point threshold of the switching power supply when the detection voltage of the detection node is greater than the opening threshold of the current point control circuit, and the controller is used to control the on-off state of the power switch tube according to the sampling signal of the sampling circuit and the target threshold. On this basis, the current point control circuit can start working and adjust the current point threshold of the switching power supply when the detection voltage meets the corresponding conditions, the controller can control the power switch tube based on the adjusted current point threshold, and the controller can also control the power switch tube based on the current point threshold when the current point control circuit is not working. The overcurrent protection circuit provided in the embodiment of the present application can realize overcurrent point control within a set part of the detection voltage range rather than overcurrent point control of the full range of input voltage, thereby achieving the overcurrent point threshold value of the full voltage range as consistent as possible, thereby improving the reliability and protection capability of the overcurrent protection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is one of the structural block diagrams of an overcurrent protection circuit according to an embodiment;

[0031] Figure 2 This is a second structural block diagram of an overcurrent protection circuit according to an embodiment;

[0032] Figure 3 This is a third structural block diagram of an overcurrent protection circuit according to an embodiment;

[0033] Figure 4 This is a fourth structural block diagram of an overcurrent protection circuit according to an embodiment;

[0034] Figure 5This is a fifth structural block diagram of an overcurrent protection circuit according to an embodiment;

[0035] Figure 6 One of the structural block diagrams of a switching power supply according to an embodiment;

[0036] Figure 7 This is a second structural block diagram of a switching power supply according to an embodiment;

[0037] Figure 8 The third structural block diagram of a switching power supply according to an embodiment;

[0038] Fig. 9 This is a fourth structural block diagram of a switching power supply according to an embodiment;

[0039] Fig.10 This is a fifth structural block diagram of a switching power supply according to an embodiment. DETAILED DESCRIPTION

[0040] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] It is understood that the terms "first", "second", etc. used in this application can be used to describe various elements in this article, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. It is understood that the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have transmission of electrical signals or data with each other.

[0043] It is understood that "at least one" means one or more, and "plurality" means two or more. "At least part of an element" means part or all of an element. When used herein, the singular forms "one", "an" and " / the" may also include plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0044] In related technology 1, the overcurrent protection threshold current of the switching power supply is closely related to the resistance value of the sampling resistor. When the input voltage range of the switching power supply is too wide, under the same input power, the current peak at the lowest input voltage is much larger than the current peak at the highest input voltage. This will cause the overcurrent protection current threshold to be too high when the input voltage is high, resulting in an overpower output problem and the overcurrent protection cannot be reliably triggered. When the input side of the electronic product is short-circuited, the overcurrent protection current threshold is too large, the stress of the switch tube soars, and the switching power supply is damaged.

[0045] In related technology 2, the sampling circuit of the switching power supply includes a sampling resistor and a voltage divider resistor connected in parallel with the sampling resistor. The overcurrent protection threshold current of the switching power supply is closely related to the resistance values ​​of the sampling resistor and the voltage divider resistor. When the input voltage range is too wide, the difference between the overcurrent protection threshold current at the lowest input voltage and the overcurrent protection threshold current at the highest input voltage will be very large. Adding a voltage divider resistor can achieve voltage division, but the resistance value is generally a fixed value. When the input voltage of the switching power supply is high voltage, if the voltage divider resistor has too much voltage division, it will also cause the current flowing through the sampling resistor to be small, resulting in a low overcurrent protection threshold, posing a safety hazard.

[0046] like Figure 1 As shown, an overcurrent protection circuit is provided in the embodiment of the application. It can be understood that the overcurrent protection circuit provided in the embodiment of the application can be applied to the switching power supply to realize overcurrent protection of the power switch tube of the switching power supply. The overcurrent protection circuit provided in the embodiment of the application can adjust the overcurrent protection threshold, is suitable for the working scenario of the switching power supply inputting high voltage, and has high safety performance.

[0047] In the embodiment of the present application, the overcurrent protection circuit 10 includes: a sampling circuit 110, an overcurrent point control circuit 120 and a controller 130. The sampling circuit 110 is connected to the power switch tube, and the sampling circuit 110 can be used to collect the current signal flowing through the power switch tube Q1.

[0048] When the overcurrent protection circuit 10 is applied to a switching power supply, the sampling circuit 110 is connected to the second electrode of the power switch tube Q1. The first electrode of the power switch tube Q1 is respectively connected to the first input terminal VIN+ (for example, the positive input terminal) of the switching power supply and the first end of the first primary winding 20, the second end of the first primary winding 20 of the switching power supply is connected to the second input terminal VIN- (for example, the negative input terminal or the common ground terminal) of the switching power supply, and the secondary winding Ns of the switching power supply is connected to the power supply device.

[0049] Specifically, a first terminal of the sampling circuit 110 is connected to the second electrode of the power switch tube Q1 , and a second terminal of the sampling circuit 110 is connected to the second input terminal VIN of the switching power supply.

[0050] Optionally, the sampling circuit 110 may include a sampling resistor R1, wherein a first end of the sampling resistor R1 is connected to a second electrode of the power switch tube Q1, and a second end of the sampling circuit 110 may be connected to a second input terminal VIN- of the switching power supply for collecting a current signal flowing through the power switch tube Q1.

[0051] Optionally, the sampling circuit 110 may also include a leading edge blanking (filtering) unit, which may include a blanking resistor R2 and a filter capacitor C, wherein the first end of the blanking resistor R2 is respectively connected to the sampling port of the controller 130, the second end of the overcurrent point control circuit 120, and the first end of the filter capacitor C, the second end of the blanking resistor R2 is respectively connected to the first end of the sampling resistor R1, and the second end of the filter capacitor C is connected to the second input terminal VIN- of the switching power supply.

[0052] The first end of the overcurrent point control circuit 120 is connected to the detection node of the switching power supply. The second end of the overcurrent point control circuit 120 is connected to the sampling port of the controller 130. In the embodiment of the present application, the detection voltage of the detection node of the switching power supply varies with the input voltage of the switching power supply. The detection node may be located at the input side of the switching power supply. The overcurrent point control circuit 120 is used to adjust the overcurrent point threshold (also referred to as the overcurrent protection threshold) of the power switch tube Q1 when the detection voltage of the detection node is greater than the turn-on threshold of the overcurrent point control circuit 120. It can be understood that the overcurrent point control circuit 120 may be in a working state and a non-working state. If it is in a working state, it can adjust the overcurrent point threshold of the switching power supply. In a non-working state, the branch where the overcurrent point control circuit 120 is located is in a disconnected state, that is, the branch between the detection node and the sampling port of the controller 130 is in a disconnected state.

[0053] The controller 130 has a control port Gate and a sampling port CS, wherein the control port Gate is connected to the control port Gate of the power switch tube Q1, and the sampling port CS is also connected to the sampling circuit 110. In the embodiment of the present application, the controller 130 can be a power management integrated circuit (also referred to as a power management chip) of a switching power supply. The controller 130 can pre-store the overcurrent point threshold and obtain the overcurrent point threshold adjusted by the overcurrent point control circuit 120. The overcurrent point threshold refers to the overcurrent protection threshold pre-stored inside the controller 130. The controller 130 is used to control the on-off state of the power switch tube Q1 according to the sampling signal of the sampling circuit 110 and the target threshold; wherein the target threshold is the overcurrent point threshold or the adjusted overcurrent threshold.

[0054] Exemplarily, when the detection voltage of the detection node is greater than the turn-on threshold of the overcurrent point control circuit 120, the overcurrent point control circuit 120 starts to work and adjusts the overcurrent point threshold of the switching power supply, and the controller 130 controls the on-off state of the power switch tube Q1 based on the adjusted overcurrent point threshold and the sampling signal of the sampling circuit 110. For example, when the power switch tube Q1 is turned on, the current on the sampling resistor R1 rises linearly, and the voltage generated on the sampling resistor R1 also rises linearly. When the sampling signal reaches the adjusted overcurrent point threshold, the PWM generator inside the controller 130 flips and controls the power switch tube Q1 to turn off.

[0055] Correspondingly, when the detection voltage of the detection node is less than or equal to the turn-on threshold of the overcurrent point control circuit 120, the overcurrent point control circuit 120 does not work, and the overcurrent point threshold is determined by the preset overcurrent threshold inside the controller 130. The controller 130 controls the on-off state of the power switch tube Q1 based on the preset overcurrent threshold and the sampling signal of the sampling circuit 110. For example, when the sampling signal reaches the preset overcurrent threshold of the controller 130, the PWM generator inside the controller 130 flips to control the power switch tube Q1 to turn off.

[0056] In an embodiment of the present application, the overcurrent protection circuit includes a sampling circuit, an overcurrent point control circuit and a controller, wherein the first pole of the power switch tube is used to be connected to the first primary winding of the switching power supply, the sampling circuit is connected to the second pole of the power switch tube, the first end of the overcurrent point control circuit is connected to the detection node of the switching power supply, the control port of the controller is connected to the control end of the power switch tube, the sampling port of the controller is respectively connected to the second end of the overcurrent point control circuit and the sampling circuit, the overcurrent point control circuit is used to adjust the overcurrent point threshold of the switching power supply when the detection voltage of the detection node is greater than the opening threshold of the overcurrent point control circuit, and the controller is used to control the on-off state of the power switch tube according to the sampling signal of the sampling circuit and the target threshold. On this basis, the overcurrent point control circuit can start working and adjust the overcurrent point threshold of the switching power supply when the detection voltage meets the corresponding conditions, the controller can control the power switch tube based on the adjusted overcurrent point threshold, and the controller can also control the power switch tube based on the overcurrent point threshold when the overcurrent point control circuit is not working. Compared with the related technologies 1 and 2 introduced above, the overcurrent protection circuit provided in the embodiment of the present application starts working and adjusts the overcurrent point threshold of the switching power supply when the detection voltage meets the corresponding conditions, and can realize overcurrent point control within a set part of the detection voltage range rather than overcurrent point control of the full range of input voltage; when the overcurrent point control circuit is not working, the power switch is controlled based on the overcurrent point threshold, and is independent of the current flowing through the sampling circuit (for example, the current value is very small), so as to achieve the overcurrent point threshold of the full voltage range as consistent as possible, thereby improving the reliability and protection capability of the overcurrent protection circuit.

[0057] like Figure 2 As shown, in one embodiment, the overcurrent point control circuit 120 includes a regulating component 121 and a switching device 122, wherein a first end of the regulating component 121 is connected to a detection node of the switching power supply, a second end of the regulating component 121 is connected to a first pole of the switching device 122, and a second pole of the switching device 122 is respectively connected to a sampling port CS of a controller 130 and a sampling circuit 110.

[0058] Specifically, the regulating component 121 can be used to limit the current flowing through the switch device 122, and can also be used to adjust the overcurrent point threshold. Exemplarily, the resistance of the regulating component 121 is different, and the corresponding overcurrent point threshold is also different. Generally speaking, the resistance of the regulating component 121 is positively correlated with the overcurrent point threshold. The larger the resistance of the regulating component 121, the larger the corresponding overcurrent point threshold; correspondingly, the smaller the resistance of the regulating component 121, the smaller the corresponding overcurrent point threshold.

[0059] The switch device 122 is used to turn on the path between the first pole and the second pole of the switch device 122 when the input voltage at the input end of the switching power supply is greater than the turn-on threshold. The turn-on threshold of the switch device 122 may be an inherent property of the switch device 122. The turn-on threshold is related to the device type of the switch device 122. Different types of switch devices 122 have different corresponding turn-on thresholds. In an embodiment of the present application, the on-off control of the switch device 122 may be determined by an electrical signal on the branch where the switch device 122 is located, or may be controlled by a control component. The control component may be another controller 130 that is independent of the aforementioned controller 130.

[0060] In an embodiment of the present application, the overcurrent point control circuit includes an adjustment component and a switching device. If the switching device is turned on, the overcurrent point control circuit is in a working state, and the overcurrent point threshold can be adjusted by setting the resistance value of the adjustment component; if the switching device is disconnected, the overcurrent point control circuit is in a non-working state, and the overcurrent protection circuit can control the power switch based on the overcurrent point threshold. The overcurrent protection circuit can control whether the overcurrent point control circuit is working by using a low-cost switching device, and the overcurrent point threshold can be adjusted by sampling an adjustment component with a simple structure. In this way, the overcurrent protection circuit can sample a simple and low-cost adjustment component and a switching device to ensure that the overcurrent point threshold in the entire voltage range is as consistent as possible, thereby improving the reliability and protection capability of the overcurrent protection circuit.

[0061] like Figure 3 As shown, in one embodiment, the adjustment component 121 includes an adjustable resistor R OCP The regulating component 121 may include one adjustable resistor or multiple adjustable resistors. When there are multiple adjustable resistors, the multiple adjustable resistors may be connected in at least one of parallel and series. Optionally, the regulating component may also include one adjustable resistor and at least one current limiting resistor, wherein the adjustable resistor and the at least one current limiting resistor may be connected in at least one of parallel and series.

[0062] In the embodiment of the present application, the specific components of the regulating component 121 are not further limited, nor are they limited to the above examples. For example, the current limiting resistor can also be other electronic components that can play a current limiting role.

[0063] In this embodiment, by setting an adjustable resistor and a current point control circuit of a switch device, when the switch device is turned off, the current point control circuit does not work; when the switch device is turned on, the current point control circuit works, and the current point threshold of the switch power supply can be adjusted based on the adjustable resistor; the controller can also control the power switch based on the current point threshold when the current point control circuit is not working. In this way, the current point threshold can be adjusted by using an adjustable resistor with a simple structure and easy to adjust and control. In this way, the overcurrent protection circuit can sample an adjustable resistor with a simple structure and low cost to ensure that the current point threshold of the full voltage range is as consistent as possible, thereby improving the reliability and protection capability of the overcurrent protection circuit.

[0064] In one embodiment, the switch device 122 includes one of a triode, a MOS tube and a relay. For the sake of convenience, the switch device 122 is a triode, the detection node is the first input terminal VIN+ of the switching power supply, that is, the detection voltage is the input voltage. Among them, the overcurrent point control circuit 120 also includes a detection component (not shown in the figure) and a control component (not shown in the figure), wherein the detection component is connected to the detection node for detecting the corresponding detection voltage, and the control component is respectively connected to the detection component and the switch device 122 for turning on the path between the first pole and the second pole of the switch device 122 when the detection voltage is greater than the turn-on threshold. Specifically, the input voltage of the switching power supply is set to VIN. When the switching power supply works normally, the range of the input voltage VIN is VINmin~VINmax, wherein VINmin is the first threshold and VINmax is the fourth threshold. The turn-on threshold (called the second threshold) of the switch device 122 is VINmid1, and the turn-off threshold (called the third threshold) of the switch device 122 is Vinmin2, wherein VINmin<VINmid1<VINmid2<VINmax.

[0065] When the input voltage (i.e., the detection voltage) VIN is greater than the first threshold and less than the second threshold, the control component controls the switch device 122 to be disconnected, and the overcurrent point control circuit 120 does not work. At this time, the overcurrent point threshold is only controlled by the overcurrent threshold preset inside the controller 130; when the input voltage VIN is greater than the second threshold and less than the third threshold, the control component controls the switch device 122 to be turned on, and the overcurrent point control circuit 120 starts to work to adjust the overcurrent point threshold; when the input voltage VIN is greater than the third threshold and less than the fourth threshold, the control component controls the switch device 122 to be disconnected, and the overcurrent point control circuit 120 does not work. At this time, the overcurrent point threshold is only controlled by the overcurrent threshold preset inside the controller 130.

[0066] In this embodiment, the overcurrent control circuit may include an adjustment component (for example, an adjustable resistor), a switch device, a detection component, and a control component. By setting the connection relationship between each component and the switch device and the connection relationship with the switch power supply, the control component can realize the on-off control of the switch device according to the size of the detection voltage detected by the detection component and the turn-on voltage threshold of the turn-on device. Among them, the switch device can be one of a triode, a MOS tube, and a relay. In this way, the on-off control of one of the triode, the MOS tube, and the relay can be realized based on the comparison result of the detection voltage and the turn-on threshold of different types of switch devices. It has a simple structure and a simple control logic, and can also realize the precise control of the working state of the overcurrent point control circuit. When the switch device is in the on state, it can be combined with the adjustment component to realize the adjustment of the overcurrent point threshold, thereby improving the reliability and protection capability of the overcurrent protection circuit.

[0067] like Figure 4 As shown, in one embodiment, the switch device 122 can also be a first voltage stabilizing diode D OCP , where the first Zener diode D OCP The cathode of the switch device 122 is the first end, and the first voltage stabilizing diode D OCP The anode of the first voltage regulator diode D is the second end of the switch device 122. Different from the above-mentioned embodiment, the on-off state of the first voltage regulator diode does not need to be controlled by the control component. OCP When the turn-on voltage of the first Zener diode D OCP The breakdown voltage cannot be reached, the overcurrent point control circuit 120 is in the disconnected state, and the overcurrent point control circuit 120 does not work. At this time, the overcurrent point threshold is only controlled by the overcurrent threshold preset inside the controller 130; when the detection voltage is higher than the first voltage regulator diode D OCP When the turn-on voltage of the first Zener diode D OCP When the breakdown voltage is reached, the overcurrent point control circuit 120 is in the on state, that is, in the working state, to achieve the adjustment of the overcurrent point threshold.

[0068] In this embodiment, the overcurrent control circuit may include an adjustable resistor and a first voltage-stabilizing diode. Compared with the previous embodiment, the overcurrent point threshold can be adjusted without the detection component and the control component, thereby improving the reliability and protection capability of the overcurrent protection circuit, further simplifying the circuit structure of the overcurrent protection circuit, and reducing costs.

[0069] like Figure 5 As shown, in one embodiment, the overcurrent point control circuit 120 further includes a diode D1 , wherein an anode of the diode D1 is connected to the second end of the regulating component 121 , and a cathode of the diode D1 is connected to the first end of the switching device 122 .

[0070] Optionally, the number of the diodes may be one or more. When the number of the diodes is more than one, the multiple diodes may be connected in at least one of series connection and parallel connection.

[0071] In this embodiment, by adding a diode connected in series with the regulating component in the overcurrent point control circuit, the current flowing through the switch device 122 can be prevented from reversing.

[0072] like Figure 6-7 As shown, the present application also provides a switching power supply, including: a power switch tube Q1, a first primary winding Np (or 20 in other figures), a secondary winding Ns, an input circuit 40, and the aforementioned overcurrent protection circuit 10. The first end of the input circuit 40 is connected to the first input terminal VIN+ of the switching power supply, and the second end of the input circuit 40 is connected to the second input terminal VIN- of the switching power supply; the input circuit 40 includes at least one detection node, and the detection voltage of each detection node varies with the input voltage. Among them, the first end of the overcurrent point control circuit 120 in the overcurrent protection current is connected to any detection node. The first primary winding Np is respectively connected to the first input terminal VIN+ of the switching power supply and the first end of the power switch tube Q1; the secondary winding Ns is connected to the output end of the switching power supply to connect the power supply equipment of the switching power supply. It can be understood that the first input terminal VIN+ of the switching power supply is connected to the power supply equipment on the output side through the first primary winding Np and the secondary winding Ns. The input circuit 40 is connected between the first input terminal VIN+ and the second input terminal VIN- of the switching power supply.

[0073] The overcurrent point control circuit in the above-mentioned switching power supply can start working and adjust the overcurrent point threshold of the switching power supply when the detection voltage meets the corresponding conditions, and the controller can control the power switch based on the adjusted overcurrent point threshold. The controller can also control the power switch based on the overcurrent point threshold when the overcurrent point control circuit is not working. Compared with the related technology 1 and related technology 2 introduced above, the overcurrent protection circuit provided in the embodiment of the present application starts working and adjusts the overcurrent point threshold of the switching power supply when the detection voltage meets the corresponding conditions, and can realize the overcurrent point control within the set part of the detection voltage range instead of the overcurrent point control of the full range input voltage; when the overcurrent point control circuit is not working, the power switch is controlled based on the overcurrent point threshold, and it has nothing to do with the current flowing through the sampling circuit (for example, the current value is very small), so that the overcurrent point threshold of the full voltage range is as consistent as possible, and the reliability and protection capability of the switching power supply of the overcurrent protection circuit are improved.

[0074] Please continue to refer to Figure 6 and Figure 7In one embodiment, the input circuit 40 includes: a first current limiting unit 410 and a voltage stabilizing unit 420, wherein the first end of the first current limiting unit 410 can be used as a detection node, and is respectively connected to the first input terminal VIN+ of the switching power supply and the first end of the overcurrent point control circuit 120; the second end of the first current limiting unit 410 is connected to the first end of the voltage stabilizing unit 420, the first end of the voltage stabilizing unit 420 is also connected to the power port of the controller 130, and the second end of the voltage stabilizing unit 420 is connected to the second input terminal VIN- (for example, the negative input terminal or the common ground terminal) of the switching power supply. It can be understood that the first input terminal VIN+ of the switching power supply is connected to the power port of the controller 130 through the first current limiting unit 410 to provide a power supply voltage for the controller 130. At the same time, a voltage stabilizing unit 420 is also provided between the power port of the controller 130 and the second input terminal VIN-, which can stably provide the power supply voltage to the controller 130.

[0075] In this embodiment, the input circuit in the switching power supply includes a first current limiting unit and a voltage stabilizing power supply. The first current limiting unit can limit the current input to the power port of the controller, and the voltage stabilizing unit can also stabilize the power supply voltage provided to the controller. The input circuit can provide the controller with a safe and reliable power supply voltage, thereby improving the reliability and safety of the controller.

[0076] In one embodiment, the first current limiting unit 410 may include a first resistor Rstart1 and a second resistor, wherein the first end of the first resistor Rstart1 is the first end of the first current limiting unit 410, the second end of the first resistor Rstart1 is connected to the first end of the second resistor Rstart2, and the second end of the second resistor Rstart2 is the second end of the first current limiting unit 410.

[0077] In this embodiment, the first end of the first resistor Rstart1 and the second end of the first resistor Rstart1 can both be used as detection nodes of the switching power supply. That is, in this embodiment, the first end of the overcurrent point control circuit 120 can be connected to the first end of the first resistor Rstart1, or can be connected to the second end of the first resistor Rstart1, so that the voltage of the corresponding detection node is used as the detection voltage.

[0078] In one embodiment, the voltage stabilizing unit 420 includes a second voltage stabilizing diode Dz, the cathode of the second voltage stabilizing diode Dz is the first end of the voltage stabilizing unit 420, and the anode of the second voltage stabilizing diode Dz is the second end of the voltage stabilizing unit 420. The second voltage stabilizing diode is used to stabilize the power supply voltage provided to the controller, and the structure is simple and the cost is low.

[0079] like Figure 8 As shown, for the convenience of explanation, the overcurrent point control circuit 120 includes an adjustable resistor R OCPand the first Zener diode D OCP , and the adjustable resistor R OCP The example of connecting the first end of the first resistor Rstart1 to the second end (detection node) of the first resistor Rstart1 is used for explanation. The voltage of the detection node can be recorded as VDocp; the voltage of the second end of the second resistor Rstart2 can be recorded as VDz. The turn-on threshold of the first voltage stabilizing diode DOCP can be recorded as Vin_threshold.

[0080] Vin_threshold=VDz+(VDocp-VDz)*(Rstart1+Rstart2) / Rstart2

[0081] In the formula, Rstart1 is the resistance value of the first resistor Rstart1, and Rstart2 is the resistance value of the second resistor Rstart2.

[0082] When the detection voltage VIN is less than the turn-on threshold Vin_threshold, the first voltage regulator diode D OCP The breakdown voltage cannot be reached, and the overcurrent point control circuit 120 does not work. At this time, the overcurrent point threshold is only controlled by the overcurrent threshold preset inside the controller 130; when the detection voltage VIN is greater than the turn-on threshold Vin_threshold, the first voltage regulator diode D OCP When the breakdown voltage is reached and the circuit is in the on state, the overcurrent point control circuit 120 works and the adjustable resistor R OCP Can be used to adjust the overcurrent point threshold.

[0083] like Fig. 9 As shown, different from the above-mentioned embodiment, the voltage stabilizing unit in the input circuit 40 can also be replaced by the second current limiting unit 430. When the voltage stabilizing unit 420 in the above-mentioned embodiment is replaced by the second current limiting unit 430, the voltage at the second end of the first current limiting unit 410 can follow the input voltage change of the first input end VIN+, which can also be used as a detection node.

[0084] The first end of the second current limiting unit 430 is connected to the second end of the first current limiting unit 410 and the enable port of the controller 130 respectively, and the second end of the second current limiting unit 430 is connected to the second input terminal VIN- of the switching power supply; the first end of the first current limiting unit 410 is a detection node, the second end of the first current limiting unit 410 is another detection node, and the enable port of the controller 130 is another detection node. In this embodiment, the first end and the second end of the first current limiting unit 410 can both be used as detection nodes.

[0085] Specifically, when the first current limiting unit 410 includes a first resistor Rstart1 and a second resistor Rstart2, the first end of the first resistor Rstart1, the second end of the first resistor Rstart1, and the second end of the second resistor Rstart2 can all serve as detection nodes of the switching power supply.

[0086] Specifically, the second current limiting unit 430 may include a third resistor R EN , the third resistor R EN The first end of the second current limiting unit 430 is the first end of the third resistor R EN The second end of the third resistor R EN The first end of is connected to the second end of the second resistor Rstart2, and the second end of the third resistor REN is connected to the second input terminal VIN-.

[0087] In this embodiment, the first end and the second end of the first current limiting unit can both be used as detection nodes. Different detection nodes have different corresponding turn-on thresholds of the switching device 122. By setting different detection nodes, the flexibility of the switching power supply in adjusting the overcurrent point threshold can be improved.

[0088] Optionally, if the input circuit 40 includes a first resistor Rstart1, a second resistor Rstart2 and a third resistor R EN , the second resistor Rstart2 and the third resistor R EN The common connection point of the overcurrent point control circuit 120 can be connected to the enable port of the controller 130. In this case, the enable port of the controller 130 can also be used as a detection node of the switching power supply. Optionally, the first end of the overcurrent point control circuit 120 can be directly connected to the enable port EN of the controller 130. In this way, in this embodiment, the detection node can be connected to the enable port EN of the controller 130, and the enabling work of the controller 130 can be realized within a certain range, and the operation space is also more flexible.

[0089] Optionally, please continue to refer to Figure 6-Figure 9 The input circuit 40 further includes an energy storage unit connected in parallel with the voltage stabilizing unit 420 or the second current limiting unit 430. For example, the energy storage unit may include an energy storage capacitor C EN and at least one of an energy storage inductor.

[0090] Optionally, based on any of the foregoing embodiments, Fig.10 As shown, the switching power supply also includes a second primary winding N A and a charging protection circuit, wherein the first end of the second primary winding is connected to the power port VIN of the controller 130 via the charging protection circuit, and the second end of the second primary winding is connected to the second input terminal VIN- of the switching power supply.

[0091] Exemplarily, the charging protection circuit includes a power supply resistor R VDD and a diode Dbias, wherein the anode of the diode Dbias is connected to the first end of the second primary winding, and the cathode of the diode Dbias is connected to the first end of the second primary winding via the power supply resistor R VDD Connected to the power port of the controller 130. Optionally, the power resistor R VDD The positions of diode Dbias can be interchanged.

[0092] In this embodiment, the charging protection circuit can provide a corresponding power supply voltage to the power port VIN of the controller 130 based on the switching power supply, so as to expand the power supply path of the controller to improve the power supply diversity and stability of the controller.

[0093] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0094] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An overcurrent protection circuit, characterized in that: include: A sampling circuit, the sampling circuit is connected to a power switch tube of a switching power supply; A current point control circuit, wherein a first end of the current point control circuit is connected to a detection node of the switching power supply; wherein the current point control circuit is used to adjust the current point threshold of the switching power supply when a detection voltage at the detection node is greater than a start threshold of the current point control circuit; wherein the detection voltage varies with an input voltage of the switching power supply; A controller, wherein the control port of the controller is used to connect to the control end of the power switch tube, and the sampling port of the controller is respectively connected to the second end of the overcurrent point control circuit and the sampling circuit, and the controller is used to control the on-off state of the power switch tube according to the sampling signal of the sampling circuit and the target threshold; wherein the target threshold is the overcurrent point threshold or the adjusted overcurrent point threshold.

2. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent point control circuit includes a regulating component and a switch device, wherein the first end of the regulating component is connected to the detection node of the switching power supply, the second end of the regulating component is connected to the first pole of the switch device, and the second pole of the switch device is respectively connected to the sampling port of the controller and the sampling circuit; wherein, The switch device is used to turn on the path between the first electrode and the second electrode of the switch device when the detection voltage is greater than a turn-on threshold, wherein the turn-on threshold is related to the device type of the switch device.

3. The overcurrent protection circuit according to claim 2, characterized in that: The adjustment component includes an adjustable resistor.

4. The overcurrent protection circuit according to claim 2, characterized in that: The switching device is a first voltage-stabilizing diode, wherein the cathode of the first voltage-stabilizing diode is the first end of the switching device, and the anode of the first voltage-stabilizing diode is the second end of the switching device.

5. The overcurrent protection circuit according to claim 2, characterized in that: The switch device includes one of a triode, a MOS tube and a relay; The overcurrent point control circuit also includes a control component and a sampling component. The sampling component is connected to the detection node and is used to collect the detection voltage of the detection node. The control component is respectively connected to the sampling component and the switching device and is used to turn on the path between the first pole and the second pole of the switching device when the detection voltage is greater than the turn-on threshold.

6. The overcurrent protection circuit according to claim 2, characterized in that: The overcurrent point control circuit further comprises a diode, wherein an anode of the diode is connected to the second end of the regulating component, and a cathode of the diode is connected to the first end of the switching device.

7. A switching power supply, characterized in that: include: An input circuit, a power switch tube, a first primary winding, a secondary winding, and an overcurrent protection circuit as claimed in any one of claims 1 to 6, wherein: The first end of the input circuit is connected to the first input end of the switching power supply, and the second end of the input circuit is connected to the second input end of the switching power supply; the input circuit includes at least one detection node, and the detection voltage of each detection node varies with the input voltage, wherein the first end of the overcurrent point control circuit in the overcurrent protection current is connected to any of the detection nodes; The first primary winding is respectively connected to the first input end of the switching power supply and the first end of the power switch tube; The secondary winding is connected to the output end of the switching power supply.

8. The switching power supply according to claim 7, characterized in that: The input circuit comprises: A first current limiting unit is connected to the first input terminal of the switching power supply and the first terminal of the overcurrent point control circuit respectively; A voltage stabilizing unit, wherein the first end of the voltage stabilizing unit is respectively connected to the second end of the first current limiting unit and the power port of the controller, and the second end of the voltage stabilizing unit is connected to the second input end of the switching power supply; wherein the first end of the first current limiting unit is a detection node.

9. The switching power supply according to claim 7, characterized in that: The input circuit comprises: A first current limiting unit is connected to the first input terminal of the switching power supply and the first terminal of the overcurrent point control circuit respectively; A second current limiting unit, wherein the first end of the second current limiting unit is respectively connected to the second end of the first current limiting unit and the enable port of the controller, and the second end of the second current limiting unit is connected to the second input end of the switching power supply; the first end of the first current limiting unit is a detection node, the second end of the first current limiting unit is another detection node, and the enable port of the controller is another detection node.

10. The switching power supply according to claim 8 or 9, characterized in that: The first current limiting unit comprises a first resistor and a second resistor, wherein the first end of the first resistor is the first end of the first current limiting unit, the second end of the first resistor is connected to the first end of the second resistor, and the second end of the second resistor is the second end of the first current limiting unit; and the second end of the first resistor is another detection node.

11. The switching power supply according to claim 8, characterized in that: The voltage stabilizing unit includes a second voltage stabilizing diode, a cathode of the second voltage stabilizing diode is a first end of the voltage stabilizing unit, and an anode of the second voltage stabilizing diode is a second end of the voltage stabilizing unit.

12. The switching power supply according to claim 9, characterized in that: The second current limiting unit includes a third resistor, a first end of the third resistor is the first end of the second current limiting unit, and a second end of the third resistor is the second end of the second current limiting unit.

Images