Adjustable protection circuit, overcurrent protection method, power supply chip and switching power supply circuit

Abstract

The invention discloses an adjustable protection circuit, an overcurrent protection method, a power supply chip and a switching power supply circuit, and belongs to the technical field of integrated circuits. The adjustable protection circuit includes a reference current circuit configured to provide a reference current; the first end of the impedance unit is electrically connected with the reference current circuit, and the second end is connected with a power supply and provides threshold voltage; the at least one first adjustable current circuit is connected with the second end of the impedance unit and is configured to respond to the temperature feedback signal of the power tube to adjust the self impedance so as to adjust the circulating first current; the voltage clamping circuit is configured to clamp the voltage of the first end of the impedance unit to a reference voltage; and the overcurrent protection circuit is configured to protect the power tube when the working feedback voltage of the power tube is greater than the threshold voltage. The temperature change of the power tube is introduced as the compensation of the over-current threshold value, so that the power tube at different temperatures can be matched with different over-current threshold values, and the over-current protection accuracy is improved.

Description

Technical Field

[0001] The present application belongs to the field of integrated circuit technology, and in particular relates to an adjustable protection circuit, an overcurrent protection method, a power chip and a switching power circuit. Background Art

[0002] In order to improve power efficiency, common power management chips are usually compatible with multiple working modes such as PFM (Pulse Frequency Modulation) and PWM (Pulse Width Modulation), and can achieve wide frequency (such as 22K~120K Hz) switch control. These chips usually contain various protection component function modules, such as overvoltage protection (OVP), over temperature protection (OTP), over current protection (OCP) and over power protection (OPP). These protections can prevent the power converter and the connected circuits from permanent damage.

[0003] In OCP protection, the overcurrent point of the power tube is different at different temperatures, which leads to the mismatch between the overcurrent threshold voltage and the actual application, which poses a hidden danger to the safety of the device. The current OCP protection cannot protect the power tube more accurately. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes an adjustable protection circuit, an overcurrent protection method, a power chip and a switching power supply circuit, which can achieve multi-level adjustable matching threshold voltage of the power tube by introducing the temperature change of the power tube as compensation for the overcurrent threshold; or introducing the working mode as compensation for the overcurrent threshold, thereby improving the accuracy of the overcurrent protection.

[0005] In a first aspect, the present application provides an adjustable protection circuit for a power tube, comprising:

[0006] a reference current circuit configured to provide a reference current;

[0007] An impedance unit, wherein a first end of the impedance unit is electrically connected to the reference current circuit, and a second end of the impedance unit is used to connect to a power supply and provide a threshold voltage;

[0008] at least one first adjustable current circuit, a first end of the first adjustable current circuit is electrically connected to the first end of the impedance unit, a second end of the first adjustable current circuit is electrically connected to the ground node, and the first adjustable current circuit is configured to adjust its own impedance in response to a temperature feedback signal of the power tube to adjust the first current flowing;

[0009] a voltage clamping circuit electrically connected to the first end of the impedance unit and configured to clamp the voltage of the first end of the impedance unit at a reference voltage;

[0010] The overcurrent protection circuit is electrically connected to the second end of the impedance unit and is configured to obtain the working feedback voltage of the power tube and protect the power tube when the working feedback voltage is greater than the threshold voltage.

[0011] According to the adjustable protection circuit of the power tube of the present application, the threshold voltage is converted by a reference current and a first current adjusted by a temperature signal of the power tube. By introducing the temperature change of the power tube as compensation for the overcurrent threshold, power tubes at different temperatures can match different overcurrent thresholds, thereby improving the accuracy of overcurrent protection.

[0012] According to an embodiment of the present application, the first adjustable current circuit is provided with a switch, and the switch is used to control the connection between the first adjustable current circuit and the impedance unit.

[0013] According to an embodiment of the present application, there are multiple first adjustable current circuits, and the signal input ends of the first adjustable current circuits are electrically connected to each other to access the temperature feedback signal of the power tube.

[0014] According to an embodiment of the present application, the corresponding relationship between the amplitude of the first current of each first adjustable current circuit and the amplitude of the temperature feedback signal is different.

[0015] According to one embodiment of the present application, the first adjustable current circuit includes a first MOS tube, the gate of the first MOS tube is used to access the temperature feedback signal, one end of the source and the drain of the first MOS tube is electrically connected to the ground node, and the other end is electrically connected to the first end of the impedance unit.

[0016] According to an embodiment of the present application, the first adjustable current circuit further includes a first switch tube, a first end of the first switch tube is electrically connected to a first end of the impedance unit, and a second end of the first switch tube is electrically connected to the first MOS tube.

[0017] According to an embodiment of the present application, there are multiple first adjustable current circuits, and the corresponding relationship between the gate voltage and the conduction current of the first MOS transistor in each first adjustable current circuit is different.

[0018] According to an embodiment of the present application, the reference current circuit includes a current mirror structure, a reference current end of the current mirror structure is connected to the reference current, and a replica current end of the current mirror structure is electrically connected to the first end of the impedance unit.

[0019] According to an embodiment of the present application, the reference current is a PTAT current with a configurable amplitude.

[0020] According to one embodiment of the present application, the voltage clamping circuit includes a voltage comparator, a first input terminal of the voltage comparator is connected to a reference voltage, a second input terminal of the voltage comparator is electrically connected to a first terminal of an impedance unit, and an output terminal of the voltage comparator is electrically connected to a second input terminal of the voltage comparator.

[0021] According to one embodiment of the present application, the adjustable protection circuit further includes:

[0022] A voltage divider circuit is electrically connected to the first adjustable current circuit and is configured to divide the temperature feedback signal of the connected power tube, provide a first signal after voltage division, and enable the first adjustable current circuit to provide a first current in response to the first signal;

[0023] The voltage divider circuit has an adjustable voltage divider ratio.

[0024] According to an embodiment of the present application, the voltage divider circuit includes a plurality of voltage divider resistors connected in series, one end of the voltage divider resistor string is connected to the temperature feedback signal of the power tube, and the other end is electrically connected to the ground node, and the connection node between the voltage divider resistors is used to provide the first signal;

[0025] Part of the voltage-dividing resistors is connected in parallel with the second switch tube; or, two ends of part of the voltage-dividing resistors are provided with welding points, and the welding points are used to weld the fuse.

[0026] According to one embodiment of the present application, the voltage divider circuit further includes:

[0027] A diode, wherein the anode of the diode is connected to the temperature feedback signal of the power tube, and the cathode of the diode is electrically connected to the voltage dividing resistor string;

[0028] The third switch tube is connected in series between the voltage-dividing resistor string and the ground node.

[0029] According to one embodiment of the present application, the overcurrent protection circuit includes:

[0030] A comparison circuit is configured to compare the threshold voltage with the working feedback voltage of the power tube to obtain a comparison result;

[0031] The driving circuit is electrically connected to the comparison circuit and is configured to perform over-current protection on the power tube according to the comparison result.

[0032] In a second aspect, the present application provides an adjustable protection circuit for a power tube, the power tube is applied to a switching power supply system, and the adjustable protection circuit includes:

[0033] a reference current circuit configured to provide a reference current;

[0034] An impedance unit, wherein a first end of the impedance unit is electrically connected to the reference current circuit, and a second end of the impedance unit is used to connect to a power supply and provide a threshold voltage;

[0035] at least one first adjustable current circuit, a first end of the first adjustable current circuit is electrically connected to the first end of the impedance unit, a second end of the first adjustable current circuit is electrically connected to the ground node, and the first adjustable current circuit is configured to adjust its own impedance in response to a temperature feedback signal of the power tube to adjust the first current flowing;

[0036] at least one second adjustable current circuit, a first end of the second adjustable current circuit is electrically connected to the first end of the impedance unit, a second end of the second adjustable current circuit is electrically connected to the ground node, and the second adjustable current circuit is configured to adjust its own impedance in response to the working mode signal of the switching power supply system to adjust the second current flowing;

[0037] a voltage clamping circuit, electrically connected to the first end of the impedance unit and configured to clamp the voltage of the first end of the impedance unit at a reference voltage;

[0038] The overcurrent protection circuit is electrically connected to the second end of the impedance unit and is configured to obtain the working feedback voltage of the power tube and protect the power tube when the working feedback voltage is greater than the threshold voltage.

[0039] According to the adjustable protection circuit of the power tube of the present application, the threshold voltage is converted by a reference current, a first current adjusted by a temperature signal of the power tube, and a second current adjusted by an operating mode signal of a switching power supply system. By introducing the temperature change and the operating mode of the power tube as compensation for the overcurrent threshold, power tubes at different temperatures can match different overcurrent thresholds, and overcurrent potentials of different operating frequencies and modes can be adjusted and matched in multiple gears, thereby improving the accuracy of overcurrent protection.

[0040] According to an embodiment of the present application, the first adjustable current circuit is provided with a first switch, and the first switch is used to control the connection between the first adjustable current circuit and the impedance unit;

[0041] The second adjustable current circuit is provided with a second switch, and the second switch is used to control the connection between the second adjustable current circuit and the impedance unit.

[0042] According to an embodiment of the present application, there are multiple first adjustable current circuits, and the signal input ends of the first adjustable current circuits are electrically connected to each other to access the temperature feedback signal of the power tube;

[0043] There are multiple second adjustable current circuits, and the signal input ends of the second adjustable current circuits are electrically connected to each other to receive the working mode signal.

[0044] According to an embodiment of the present application, the corresponding relationship between the amplitude of the first current of each first adjustable current circuit and the amplitude of the temperature feedback signal is different;

[0045] The corresponding relationship between the amplitude of the second current of each second adjustable current circuit and the mode represented by the working mode signal is different.

[0046] According to one embodiment of the present application, the first adjustable current circuit includes a first MOS tube, and the second adjustable current circuit includes a second MOS tube. The gate of the first MOS tube is used to access a temperature feedback signal, and the gate of the second MOS tube is used to access an operating mode signal. One end of the source and drain of the first MOS tube and the second MOS tube is electrically connected to a ground node, and the other end is electrically connected to a first end of the impedance unit.

[0047] According to one embodiment of the present application, there are multiple first adjustable current circuits, and there are multiple second adjustable current circuits. The corresponding relationship between the gate voltage and the on-current of the first MOS tube in each first adjustable current circuit is different, and the corresponding relationship between the gate voltage and the on-current of the second MOS tube in each second adjustable current circuit is different.

[0048] According to one embodiment of the present application, the adjustable protection circuit further includes:

[0049] A first voltage divider circuit is electrically connected to the first adjustable current circuit and is configured to divide the temperature feedback signal of the connected power tube, provide a first signal after voltage division, and enable the first adjustable current circuit to provide a first current in response to the first signal;

[0050] A second voltage divider circuit is electrically connected to the second adjustable current circuit and is configured to divide the working mode signal of the connected switching power supply system, provide a second signal after voltage division, and make the second adjustable current circuit provide a second current in response to the second signal;

[0051] Wherein, both the first voltage-dividing circuit and the second voltage-dividing circuit have an adjustable voltage-dividing ratio.

[0052] According to an embodiment of the present application, the mode represented by the working mode signal includes a pulse frequency modulation mode, a discontinuous conduction mode or a continuous conduction mode.

[0053] In a third aspect, the present application provides an overcurrent protection method for a power tube, which is applied to the above-mentioned adjustable protection circuit. The overcurrent protection method includes:

[0054] Obtain the working feedback voltage and temperature feedback signal of the power tube;

[0055] Adjust the first current flowing through the first adjustable current circuit according to the temperature feedback signal so that the sum of the first current and the reference current is converted into a threshold voltage;

[0056] When the working feedback voltage is greater than the threshold voltage, the power tube is protected from overcurrent.

[0057] According to the overcurrent protection method of the power tube of the present application, a threshold voltage is generated according to a reference current and a first current adjusted by a temperature signal of the power tube. By introducing the temperature change of the power tube as compensation for the overcurrent threshold, power tubes at different temperatures can match different overcurrent thresholds, thereby improving the accuracy of overcurrent protection.

[0058] According to an embodiment of the present application, adjusting a first current flowing through a first adjustable current circuit according to a temperature feedback signal includes:

[0059] Determine the correction gear position according to the device information of the power tube;

[0060] The number of the first adjustable current circuits opened is adjusted according to the correction gear position;

[0061] The temperature feedback signal is used to adjust the first current flowing through the opened first adjustable current circuit.

[0062] According to one embodiment of the present application, obtaining the temperature feedback signal includes:

[0063] Receive a detection signal of the power tube fed back by a temperature detection unit;

[0064] Determine the voltage division position according to the device information of the power tube;

[0065] The voltage of the detection signal is divided according to the voltage division gear to obtain a temperature feedback signal.

[0066] In a fourth aspect, the present application provides an overcurrent protection method for a power tube, which is applied to the above-mentioned adjustable protection circuit, and the power tube is applied to a switching power supply system. The overcurrent protection method includes:

[0067] Obtain the working feedback voltage and temperature feedback signal of the power tube;

[0068] Obtaining an operating mode signal of a switching power supply system;

[0069] adjusting a first current flowing through a first adjustable current circuit according to a temperature feedback signal, and adjusting a second current flowing through a second adjustable current circuit according to an operation mode signal, so that a sum of the first current, the second current and a reference current is converted into a threshold voltage;

[0070] When the working feedback voltage is greater than the threshold voltage, the power tube is protected from overcurrent.

[0071] According to the overcurrent protection method of the power tube of the present application, a threshold voltage is generated according to a reference current, a first current adjusted by a temperature signal of the power tube, and a second current adjusted by an operating mode signal of a switching power supply system. By introducing the temperature change and the operating mode of the power tube as compensation for the overcurrent threshold, power tubes at different temperatures can match different overcurrent thresholds, and overcurrent potentials of different operating frequencies and modes can be adjusted and matched in multiple gears, thereby improving the accuracy of overcurrent protection.

[0072] According to an embodiment of the present application, adjusting a first current flowing through a first adjustable current circuit according to a temperature feedback signal, and adjusting a second current flowing through a second adjustable current circuit according to an operating mode signal, includes:

[0073] Determine the correction gear position according to the device information of the power tube;

[0074] Determine the number of first adjustable current circuits to be opened and the number of second adjustable current circuits to be opened according to the correction gear position;

[0075] The temperature feedback signal is used to adjust the first current flowing through the first adjustable current circuit, and the working mode signal is used to adjust the second current flowing through the second adjustable current circuit.

[0076] According to one embodiment of the present application, the acquisition of the temperature feedback signal and the working mode signal includes:

[0077] Receive a detection signal of the power tube fed back by a temperature detection unit;

[0078] receiving a mode signal of the switching power supply system fed back by a mode control unit;

[0079] Determine a first voltage division position and a second voltage division position according to device information of the power tube;

[0080] Performing voltage division processing on the detection signal according to the first voltage division gear to obtain a temperature feedback signal;

[0081] The voltage of the mode signal is divided according to the second voltage division gear to obtain the working mode signal.

[0082] In a fifth aspect, the present application provides a power management chip, comprising an adjustable protection circuit according to the aforementioned method.

[0083] According to the power management chip of the present application, a protection circuit with an adjustable threshold is usually used to implement overcurrent protection, which can more accurately protect the driven power tube and avoid damage to the power tube.

[0084] In a sixth aspect, the present application provides a switching power supply circuit, comprising an adjustable protection circuit and a power conversion circuit according to the aforementioned method, wherein the power conversion circuit comprises a power tube, and the power tube is electrically connected to the adjustable protection circuit.

[0085] According to the switching power supply circuit of the present application, a protection circuit with an adjustable threshold is usually used to implement overcurrent protection, which can more accurately protect the driven power tube and avoid damage to the power tube.

[0086] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0088] Figure 1 It is one of the circuit block diagrams of the adjustable protection circuit provided in the embodiment of the present application;

[0089] Figure 2 is a circuit block diagram of an overcurrent protection circuit provided in an embodiment of the present application;

[0090] Figure 3 It is one of the circuit principle diagrams of the adjustable protection circuit provided in the embodiment of the present application;

[0091] Figure 4 This is the second circuit block diagram of the adjustable protection circuit provided in the embodiment of the present application;

[0092] Figure 5 is a circuit schematic diagram of a voltage divider circuit provided in an embodiment of the present application;

[0093] Figure 6 This is the third circuit block diagram of the adjustable protection circuit provided in the embodiment of the present application;

[0094] Figure 7 This is the second circuit schematic diagram of the adjustable protection circuit provided in the embodiment of the present application;

[0095] Figure 8 This is the fourth circuit block diagram of the adjustable protection circuit provided in the embodiment of the present application;

[0096] Fig. 9 This is one of the flow charts of the overcurrent protection method provided in the embodiment of the present application;

[0097] Fig.10 This is the second flow chart of the overcurrent protection method provided in the embodiment of the present application;

[0098] Fig.11A circuit diagram of a flyback power supply provided in an embodiment of the present application.

[0099] Reference numerals:

[0100] Adjustable protection circuit 10, reference current circuit 11, first adjustable current circuit 12, impedance unit 131, voltage clamping circuit 132, overcurrent protection circuit 14, comparison circuit 141, drive circuit 142, voltage divider circuit 15, first voltage divider circuit 151, second voltage divider circuit 152, second adjustable current circuit 16, power tube 20, power management chip 30, voltage comparators A1, A2, first to second MOS tubes Q1~Q2, first to fourth switch tubes K1~K4, first to fourth resistors R1~R4, diode D. DETAILED DESCRIPTION

[0101] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0102] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0103] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0104] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean 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 representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0105] Reference Figure 1 , Figure 1 The circuit framework of an adjustable protection circuit is shown. In this embodiment, the adjustable protection circuit 10 is used to drive the power tube 20. The adjustable protection circuit 10 includes a reference current circuit 11, at least one first adjustable current circuit 12, an impedance unit 131, a voltage clamp circuit 132 and an overcurrent protection circuit 14. The reference current circuit 11 is configured to provide a reference current; the first end of the impedance unit 131 is electrically connected to the reference current circuit 11, and the second end of the impedance unit 131 is used to connect to a power supply and provide a threshold voltage; the first end of the first adjustable current circuit 12 is electrically connected to the first end of the impedance unit 131, and the second end of the impedance unit 131 is used to connect to a power supply and provide a threshold voltage. A second end of an adjustable current circuit 12 is electrically connected to a ground node. The first adjustable current circuit 12 is configured to adjust its own impedance in response to a temperature feedback signal of the power tube 20 to adjust the first current flowing therethrough. A voltage clamping circuit 132 is electrically connected to a first end of an impedance unit 131 and is configured to clamp the voltage of the first end of the impedance unit 131 at a reference voltage. An overcurrent protection circuit 14 is electrically connected to a second end of the impedance unit 131 and is configured to obtain an operating feedback voltage of the power tube 20 and protect the power tube 20 when the operating feedback voltage is greater than a threshold voltage.

[0106] The power tube 20 may be a MOSFET tube (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET for short) or an IGBT tube (Insulated Gate Bipolar Transistor).

[0107] The internal resistance of the power tube 20 is significantly affected by temperature. At different temperatures, the overcurrent point of the power tube 20 is different due to the change of internal resistance. In order to eliminate or reduce the interference of temperature on overcurrent protection, the temperature signal of the power tube 20 is introduced to correct the overcurrent protection threshold.

[0108] The power tube 20 may be provided with a working voltage detection circuit and a temperature detection device (such as a temperature sensor, etc.). The temperature detection device detects the temperature of the power tube 20 itself, or detects the temperature of the environment in which the power tube 20 is located, generates a temperature detection signal, and transmits it to the controller as a temperature feedback signal. The working voltage detection circuit detects the actual working voltage of the power tube 20, and transmits the detection signal to the controller.

[0109] As an example, the temperature feedback signal may be a voltage signal, and its voltage value is positively correlated or negatively correlated with the temperature of the power tube 20. That is, the higher the temperature of the power tube 20, the higher or lower the voltage value of the temperature feedback signal. The first adjustable current circuit 12 adjusts the current value of the first current provided according to the voltage of the temperature feedback signal.

[0110] It can be understood that the value of the threshold voltage is equal to the sum of the reference voltage and the voltage across the impedance unit 131. The sum of the reference current provided by the reference current circuit 11 and the current flowing through the first adjustable current circuit 12 is the total current flowing through the impedance unit 131. Therefore, when the reference current remains unchanged, the greater the first current flowing through the first adjustable current circuit 12, the greater the voltage across the impedance unit 131, and the greater the threshold voltage.

[0111] In this embodiment, the power source connected to the second end of the impedance unit 131 can be a voltage regulator, and the impedance of the first adjustable current circuit 12 changes with the temperature feedback signal. For example, the higher the voltage of the temperature feedback signal, the lower the impedance of the first adjustable current circuit 12, the larger the first current flowing, and the larger the threshold voltage; or the lower the voltage of the temperature feedback signal, the lower the impedance of the first adjustable current circuit 12, the larger the first current flowing, and the larger the threshold voltage. In this way, the temperature of the power tube 20 can achieve the modulation of the threshold voltage.

[0112] The overcurrent protection circuit 14 is used to determine whether overcurrent protection is required. It determines whether there is overcurrent by comparing the actual working voltage of the power tube 20 with the threshold voltage. The overcurrent protection circuit 14 determines that there is overcurrent when the actual working voltage is greater than or equal to the threshold voltage; and determines that there is no overcurrent when the actual working voltage is less than the threshold voltage.

[0113] The protection action performed by the overcurrent protection circuit 14 may be to shut down the power tube 20 or to reduce the actual working voltage of the power tube 20 , which may be specifically set according to requirements, and this embodiment does not impose any limitation on this.

[0114] Reference Figure 2 , Figure 2The circuit structure of an overcurrent protection circuit is shown. In some embodiments, the overcurrent protection circuit 14 may include a comparison circuit 141 and a drive circuit 142, wherein the comparison circuit 141 is configured to compare the threshold voltage with the working feedback voltage of the power tube 20 to obtain a comparison result; and the drive circuit 142 is electrically connected to the comparison circuit 141 and configured to perform overcurrent protection on the power tube 20 according to the comparison result.

[0115] exist Figure 2 In the figure, V_CS represents the working feedback voltage, Vth_OC represents the threshold voltage, and V_PWM represents the driving reference voltage used to modulate the driving signal of the power tube 20. The comparison circuit 141 may include a voltage comparator A1, and the input end of the voltage comparator A1 is used to access the threshold voltage and the working feedback voltage of the power tube 20; wherein the working feedback voltage represents the actual working voltage of the power tube 20. The output end of the voltage comparator A1 may be electrically connected to the driving circuit 142, and its output signal is used to indicate whether the driving circuit 142 turns on the overcurrent protection.

[0116] As an example, when the positive input terminal of the voltage comparator A1 is connected to the working feedback voltage and the negative input terminal is connected to the threshold voltage, when the output terminal of the voltage comparator A1 is at a high level, the drive circuit 142 turns on the overcurrent protection; or when the positive input terminal of the voltage comparator A1 is connected to the threshold voltage and the negative input terminal is connected to the working feedback voltage, when the output terminal of the voltage comparator A1 is at a low level, the drive circuit 142 turns on the overcurrent protection.

[0117] The driving circuit 142 is used to generate a driving signal according to the driving reference voltage, and apply the driving signal to the power tube 20 to control the opening or closing of the power tube 20. The driving signal may be a PWM signal. The driving circuit 142 may perform an overcurrent protection action when the overcurrent protection is turned on according to the output signal of the comparison circuit 141.

[0118] As an example, the increase in the temperature of the power tube 20 will cause the internal resistance to increase, thereby causing the required threshold voltage to decrease. For example, the higher the temperature of the power tube 20, the lower the voltage value of the temperature feedback signal, and the lower the current value of the current flowing through the first adjustable current circuit 12. When the temperature of the power tube 20 increases, the threshold voltage is also lower, thereby achieving compensation for the threshold voltage.

[0119] According to the adjustable protection circuit 10 of the power tube 20 of the present application, the threshold voltage is converted by a reference current and a circulating current adjusted by a temperature signal of the power tube 20. By introducing the temperature change of the power tube 20 as compensation for the overcurrent threshold, the power tube 20 at different temperatures can match different overcurrent thresholds, thereby improving the accuracy of overcurrent protection.

[0120] In some embodiments, the first adjustable current circuit 12 is provided with a switch, and the switch is used to control the connection between the first adjustable current circuit 12 and the impedance unit 131 .

[0121] In this embodiment, the switch can realize the turning on or off of the temperature compensation function. When the switch is closed, the first current flowing through the first adjustable current circuit 12 is superimposed on the impedance unit 131, and the impedance unit 131 generates a threshold voltage based on the adjustable first current and the reference current to achieve temperature compensation. When the switch is open, the first current of the first adjustable current circuit 12 cannot be superimposed on the impedance unit 131, and the impedance unit 131 generates a threshold voltage based on the reference current, and temperature compensation is not achieved.

[0122] In some embodiments, there are multiple first adjustable current circuits 12 , and signal input terminals of the first adjustable current circuits 12 are electrically connected to each other to receive the temperature feedback signal of the power tube 20 .

[0123] In this embodiment, multiple first adjustable current circuits 12 are provided to achieve multi-level regulation and adapt different power tubes 20. As required, switches in a specific number of first adjustable current circuits 12 can be controlled to close, so that the temperature feedback signal controls a specific number of first currents.

[0124] As an example, in the first gear, the switch in one first adjustable current circuit 12 is closed, and the switches in the other first adjustable current circuits 12 are disconnected, then the temperature feedback signal adjusts one first current. In the second gear, the switches in two first adjustable current circuits 12 are closed, and the switches in the other first adjustable current circuits 12 are disconnected, then the temperature feedback signal adjusts the two first currents. In the first gear and the second gear, the temperature of the power tube 20 is the same, but the compensation degree of the threshold voltage is different.

[0125] In some embodiments, the corresponding relationship between the amplitude of the first current of each first adjustable current circuit 12 and the amplitude of the temperature feedback signal is different.

[0126] The corresponding relationship between the amplitude of the first current and the amplitude of the temperature feedback signal refers to the adjustment amplitude of the first adjustable current circuit 12, which affects the amplitude of the corresponding first current when the temperature feedback signal is at a certain value, or affects the amplitude of the change of the first current when the amplitude of the temperature feedback signal changes. In this way, more gear selections can be achieved.

[0127] As an example, under two different corresponding relationships, when the amplitude of the temperature feedback signal is V1, the first current of one first adjustable current circuit 12 is I1, and the first current of the other first adjustable current circuit 12 is I2. Among them, I1 and I2 are not equal. Or when the amplitude of the temperature feedback signal changes to △V1, the amplitude of the first current of one first adjustable current circuit 12 changes to △I1, and the amplitude of the first current of the other first adjustable current circuit 12 changes to △I2. Among them, △I1 and △I2 are not equal.

[0128] In the third gear, a switch in the first adjustable current circuit 12 is closed, and the switches in the other first adjustable current circuits 12 are opened, the amplitude of the temperature feedback signal is V1, the first current of the first adjustable current circuit 12 is I1, and the impedance unit 131 generates a threshold voltage based on the reference current and the current I1. In the fourth gear, a switch in the first adjustable current circuit 12 is closed, and the switches in the other first adjustable current circuits 12 are opened, the amplitude of the temperature feedback signal is V1, the first current of the first adjustable current circuit 12 is I2, and the impedance unit 131 generates a threshold voltage based on the reference current and the current I2.

[0129] In the fifth gear, the switches in two first adjustable current circuits 12 are closed, and the switches in the other first adjustable current circuits 12 are opened, the amplitude of the temperature feedback signal is V1, the first currents of the two first adjustable current circuits 12 are I3 and I4, respectively, and the impedance unit 131 generates a threshold voltage according to the currents I3, I4 and the reference current. In the sixth gear, the switches in two first adjustable current circuits 12 are closed, and the switches in the other first adjustable current circuits 12 are opened, the amplitude of the temperature feedback signal is V1, the first currents of the two first adjustable current circuits 12 are I5 ​​and I6, respectively, and the impedance unit 131 generates a threshold voltage according to the currents I5, I6 and the reference current.

[0130] Reference Figure 3 , Figure 3 A circuit schematic diagram of an adjustable protection circuit is shown. In some embodiments, the voltage clamping circuit 132 includes a voltage comparator A2, a first input terminal of the voltage comparator A2 is connected to a reference voltage, a second input terminal of the voltage comparator A1 is electrically connected to a first terminal of the impedance unit 131, and an output terminal of the voltage comparator A2 is electrically connected to a second input terminal of the voltage comparator A1.

[0131] In this embodiment, the impedance unit 131 includes a first resistor R1 . Figure 3Where Vref represents the reference voltage, and the first input terminal of the voltage comparator A2 can be a positive input terminal or a negative input terminal. The voltage comparator A2 acts as a clamp to keep the voltage at one end of the first resistor R1 constant at the reference voltage. The threshold voltage Vth_OC = Vref + R1 × I. Where I is the current flowing through the first resistor R1.

[0132] In some embodiments, the first adjustable current circuit 12 includes a first MOS transistor Q1, a gate of the first MOS transistor Q1 is used to access a temperature feedback signal, one end of a source and a drain of the first MOS transistor Q1 is electrically connected to a ground node, and the other end is electrically connected to a first end of a first resistor R1.

[0133] As an example, the source of the first MOS transistor Q1 may be electrically connected to the ground node, and the drain of the first MOS transistor Q1 may be electrically connected to the first end of the first resistor R1.

[0134] It should be noted that the first MOS tube Q1 in this embodiment is used to control the current on the branch. The first MOS tube Q1 operates in an unsaturated region, and the temperature feedback signal acting on the gate controls the current flowing through the first MOS tube Q1 using its voltage. The current flowing through the first MOS tube Q1 is the first current, and there is a positive correlation between the voltage value of the temperature feedback signal and the current value of the first current.

[0135] In some embodiments, the first adjustable current circuit 12 further includes a first switch tube K1 , a first end of the first switch tube K1 is electrically connected to a first end of the impedance unit 131 , and a second end of the first switch tube K1 is electrically connected to the first MOS tube Q1 .

[0136] The first switch tube K1 may also be a MOS tube or an IGBT tube. As an example, the first switch tube K1 is a MOS tube, the source of the first switch tube K1 is electrically connected to the drain of the first MOS tube Q1, and the drain of the first switch tube K1 is electrically connected to the first end of the first resistor R1.

[0137] The gate of the first switch tube K1 is used to access the switch signal, and the switch signal can be provided by the overcurrent protection circuit 14. The first switch tube K1 is arranged between the first MOS tube Q1 and the first resistor R1, and its closing or opening can control whether the branch is used to achieve temperature compensation. When the first switch tube K1 is closed, the first MOS tube Q1 can adjust the current flowing through the first resistor R1, thereby achieving temperature compensation for the threshold voltage; when the first switch tube K1 is turned off, the first MOS tube Q1 has no effect on the first resistor R1.

[0138] In some embodiments, there are multiple first adjustable current circuits 12 , and the corresponding relationship between the gate voltage and the conduction current of the first MOS transistor Q1 in each first adjustable current circuit 12 is different.

[0139] In this embodiment, a plurality of first MOS tubes Q1 connected in parallel can achieve multi-level adjustment to adapt to different power tubes 20. As needed, the first switch tube K1 corresponding to the first MOS tube Q1 can be controlled to be closed or turned off, so that the temperature feedback signal controls a specific number of first MOS tubes Q1, thereby adjusting the total current flowing through the first resistor R1.

[0140] The corresponding relationship between the gate voltage of the first MOS tube Q1 and the conduction current refers to the adjustment amplitude of the first MOS tube Q1, which affects the amplitude of the first current flowing through the gate voltage of the first MOS tube Q1 when the gate voltage of the first MOS tube Q1 is at a certain value, or affects the amplitude of the change of the first current flowing through the first MOS tube Q1 when the amplitude of the gate voltage of the first MOS tube Q1 changes. In this way, more gear selections can be achieved. For the control of multiple gears, please refer to the above, and this embodiment will not be repeated here.

[0141] In some embodiments, the reference current circuit 11 includes a current mirror structure, a reference current terminal of the current mirror structure is connected to the reference current, and a replica current terminal of the current mirror structure is electrically connected to the first terminal of the impedance unit 131 .

[0142] exist Figure 3 In FIG. 1 , Iref represents a reference current, which is copied to the branch connected to the first resistor R1 through a current mirror structure. The current mirror structure can be a MOS tube with two gates connected to each other. Thus, the reference current circuit 11 can be guaranteed to provide a stable reference current.

[0143] In some embodiments, the reference current is a PTAT current with a configurable amplitude.

[0144] The adjustable protection circuit 10 may also include a reference current generating circuit (not shown in the figure), which is used to generate a PTAT (Proportional to Absolute Temperature) current. The PTAT current is a current that is proportional to the absolute temperature, which itself has a certain degree of temperature compensation effect, realizes compensation for the overcurrent threshold, and improves the accuracy of overcurrent protection. And the reference current generating circuit can adjust the reference current by adjusting the duty cycle. Thus, the special needs of some application scenarios can be met.

[0145] Reference Figure 4 , Figure 4The circuit structure of an adjustable protection circuit 10 is shown. In some embodiments, the adjustable protection circuit 10 further includes a voltage divider circuit 15, which is electrically connected to the first adjustable current circuit 12 and configured to divide the temperature feedback signal of the connected power tube 20, provide a first signal after voltage division, and enable the first adjustable current circuit 12 to provide a first current in response to the first signal; wherein the voltage divider circuit 15 has an adjustable voltage division ratio.

[0146] It can be understood that when the voltage of the temperature feedback signal is the same, the voltage dividing ratio of the voltage dividing circuit 15 is different, and the voltage of the first signal transmitted to the first adjustable current circuit 12 is different, thereby causing the first current to be different. By setting the voltage dividing circuit 15 to pre-process the temperature feedback signal, on the one hand, its voltage is adapted to the working range of the first MOS tube Q1, and on the other hand, multiple gear adjustments are achieved through the adjustable voltage dividing ratio.

[0147] Reference Figure 5 , Figure 5 The circuit structure of a voltage divider circuit is shown. In some embodiments, the voltage divider circuit 15 includes a plurality of voltage divider resistors connected in series, one end of the voltage divider resistor string is connected to the temperature feedback signal of the power tube 20, and the other end is electrically connected to the ground node, and the connection node between the voltage divider resistors is used to provide a first signal; wherein, some of the voltage divider resistors are connected in parallel with the second switch tube K2; or, some of the voltage divider resistors are provided with welding points at both ends, and the welding points are used to weld fuses.

[0148] As an example, the voltage-dividing resistor may include a second resistor R2, a third resistor R3 and a fourth resistor R4 connected in series to form a voltage-dividing resistor string. The connection node between the third resistor R3 and the fourth resistor R4 is used to provide the first signal to the first MOS transistor Q1. Figure 5 In FIG. 1 , V_fb represents the temperature feedback signal, and V_fb1 represents the first signal.

[0149] In the first example, a second switch tube K2 is connected in parallel across the second resistor R2 and the fourth resistor R4. The second switch tube K2 may be a MOS tube or an IGBT tube. When the second switch tube K2 is closed, the corresponding resistors are short-circuited, thereby changing the voltage division ratio. Figure 5 In the structure shown, a total of 4 voltage divider ratios can be configured.

[0150] In another example, solder joints are provided at both ends of the second resistor R2 and the fourth resistor R4. When the voltage divider circuit 15 is used, a fuse can be welded between the solder joints to directly short-circuit the corresponding resistors to adjust the voltage divider ratio. This example can select a suitable voltage divider ratio for different scenarios and keep the voltage divider ratio unchanged.

[0151] In some embodiments, the voltage divider circuit 15 further includes a diode D and a third switch tube K3, the anode of the diode D is connected to the temperature feedback signal of the power tube 20, and the cathode of the diode D is electrically connected to the voltage divider resistor string; the third switch tube K3 is connected in series between the voltage divider resistor string and the ground node.

[0152] As an example, the cathode of the diode D can be electrically connected to a section of the second resistor R2, the first end of the third switch tube K3 can be electrically connected to one end of the fourth resistor, and the second end of the third switch tube K3 can be electrically connected to the ground node. The third switch tube K3 can be used to control the function of the voltage divider circuit 15. When the third switch tube K3 is closed, the voltage divider circuit 15 can use different voltage divider ratios to adjust the temperature feedback signal; when the third switch tube K3 is turned off, the voltage divider circuit 15 operates at a constant voltage divider ratio. The control signals of the second switch tube K2 and the third switch tube K3 can also be provided by the overcurrent protection circuit 14.

[0153] Reference Figure 6 , Figure 6 The circuit framework of an adjustable protection circuit 10 is shown. In this embodiment, the power tube 20 is applied to a switching power supply system, and the adjustable protection circuit 10 includes a reference current circuit 11, at least one first adjustable current circuit 12, at least one second adjustable current circuit 16, an impedance unit 131 and an overcurrent protection circuit 14. The reference current circuit 11 is configured to provide a reference current; the first end of the impedance unit 131 is electrically connected to the reference current circuit 11, and the second end of the impedance unit 131 is used to connect to the power supply and provide a threshold voltage; the first end of the first adjustable current circuit 12 is electrically connected to the first end of the impedance unit 131, and the second end of the first adjustable current circuit 12 is electrically connected to the ground node, and the first adjustable current circuit 12 is configured to adjust its own impedance in response to the temperature feedback signal of the power tube 20 to adjust the flow current; the first end of the second adjustable current circuit 16 is electrically connected to the first end of the impedance unit 131, and the second end of the second adjustable current circuit 16 is electrically connected to the ground node, and the second adjustable current circuit 16 is configured to adjust its own impedance in response to the working mode signal of the switching power supply system to adjust the flow current; the voltage clamping circuit 132 is electrically connected to the first end of the impedance unit 131, and is configured to clamp the voltage of the first end of the impedance unit 131 at the reference voltage; the overcurrent protection circuit 14 is electrically connected to the second end of the impedance unit 131, and is configured to obtain the working feedback voltage of the power tube 20, and protect the power tube 20 when the working feedback voltage is greater than the threshold voltage.

[0154] and Figure 1 The difference of the adjustable protection circuit 10 shown is that the adjustable protection circuit 10 in this embodiment is further provided with a second adjustable current circuit 16. The second adjustable current circuit 16 realizes the correction of the threshold voltage according to the working mode of the switching power supply system.

[0155] It is understandable that in actual applications, the system may be in different modes, and the corresponding operating frequencies may also be significantly different, resulting in significantly different requirements for overcurrent protection. In related technologies, the compensation method is to sample the bus to compensate for the CS peak, which requires the addition of additional devices, making the circuit more complex and increasing the difficulty of peripheral design.

[0156] In some embodiments, the mode represented by the working mode signal includes a pulse frequency modulation mode (PFM), a discontinuous conduction mode (DCM), or a continuous conduction mode (CCM). For example, when the mode is the pulse frequency modulation mode, the current value of the second current is IB1; when the mode is the discontinuous conduction mode, the current value of the second current is IB2; when the mode is the continuous conduction mode, the current value of the second current is IB3. Among them, IB1, IB2 and IB3 are different.

[0157] In this embodiment, since the current value of the first current is affected by the temperature of the power tube 20 and the current value of the second current is affected by the system operating mode, the temperature of the power tube 20 and the system operating mode can simultaneously adjust the correction amplitude of the reference current.

[0158] The relevant descriptions about the reference current circuit 11 , the first adjustable current circuit 12 and the overcurrent protection circuit 14 may refer to the aforementioned embodiments, and will not be described in detail in this embodiment.

[0159] According to the adjustable protection circuit 10 of the power tube 20 of the present application, the threshold voltage is converted by a reference current, a first current adjusted by a temperature signal of the power tube 20, and a second current adjusted by an operating mode signal of the switching power supply system. By introducing the temperature change and the operating mode of the power tube 20 as compensation for the overcurrent threshold, power tubes at different temperatures can match different overcurrent thresholds, and overcurrent potentials of different operating frequencies and modes can be adjusted and matched in multiple gears, thereby improving the accuracy of overcurrent protection.

[0160] In some embodiments, the first adjustable current circuit 12 is provided with a first switch, and the first switch is used to control the connection between the first adjustable current circuit 12 and the impedance unit 113. The second adjustable current circuit 16 is provided with a second switch, and the second switch is used to control the connection between the second adjustable current circuit 16 and the impedance unit 131.

[0161] In this embodiment, the first switch can realize the turning on or off of the temperature compensation function. The second switch can realize the turning on or off of the mode compensation function. When the first switch and / or the second switch are closed, the corresponding compensation function is turned on; when the first switch and / or the second switch are turned off, the corresponding compensation function is turned off. The first switch and the second switch can be closed or turned off separately or simultaneously.

[0162] In some embodiments, there are multiple first adjustable current circuits 12, and the signal input ends of each first adjustable current circuit 12 are electrically connected to each other to access the temperature feedback signal of the power tube 20; there are multiple second adjustable current circuits 16, and the signal input ends of each second adjustable current circuit 16 are electrically connected to each other to access the working mode signal.

[0163] In this embodiment, multiple first adjustable current circuits 12 are provided to achieve multi-level adjustment of temperature compensation, and multiple second adjustable current circuits 16 are provided to achieve multi-level adjustment of mode compensation, thereby adapting different power tubes 20. In different levels, the corresponding opening and closing of different numbers of first adjustable current circuits 12 and / or second adjustable current circuits 16 can be controlled.

[0164] In some embodiments, the corresponding relationship between the amplitude of the first current of each first adjustable current circuit 12 and the amplitude of the temperature feedback signal is different; the corresponding relationship between the amplitude of the second current of each second adjustable current circuit 16 and the mode represented by the working mode signal is different.

[0165] It should be noted that both the temperature feedback signal and the operating mode signal can be voltage signals. The relationship between the first current and the temperature feedback signal and the relationship between the second current and the operating mode signal can achieve more gear selections. For details, please refer to the aforementioned gear description of the first adjustable current circuit 12, and the gear setting of the second adjustable current circuit 16 can refer to the gear setting of the first adjustable current circuit 12.

[0166] Reference Figure 7 , Figure 7 A circuit schematic diagram of an adjustable protection circuit 10 is shown. In some embodiments, the first end of the impedance unit 131 is electrically connected to the reference current circuit 11, the first adjustable current circuit 12, and the second adjustable current circuit 16, respectively, and the second end of the impedance unit 131 is used to connect the power supply VCC and provide a threshold voltage; the voltage clamping circuit 132 is electrically connected to the first end of the impedance unit 131, and is configured to clamp the voltage of the first end of the impedance unit 131 at the reference voltage.

[0167] The value of the threshold voltage is equal to the sum of the reference voltage and the voltage across the impedance unit 131. The sum of the reference current provided by the reference current circuit 11, the first current provided by the first adjustable current circuit 12, and the second current provided by the second adjustable current circuit 16 is the total current flowing through the impedance unit 131. The larger the first current and / or the second current, the larger the voltage across the impedance unit 131, and the larger the threshold voltage.

[0168] In some embodiments, the first adjustable current circuit 12 includes a first MOS transistor Q1, and the second adjustable current circuit 16 includes a second MOS transistor Q2. The gate of the first MOS transistor Q1 is used to access a temperature feedback signal, and the gate of the second MOS transistor Q2 is used to access an operating mode signal. One end of the source and drain of the first MOS transistor Q1 and the second MOS transistor Q2 is electrically connected to the ground node, and the other end is electrically connected to the first end of the impedance unit 131.

[0169] As an example, the sources of the first MOS transistor Q1 and the second MOS transistor Q2 are both electrically connected to the ground node, and the drains of the first MOS transistor Q1 and the second MOS transistor Q2 are electrically connected to the first end of the first resistor R1. The first MOS transistor Q1 and the second MOS transistor Q2 operate in an unsaturated region to control the current flowing through the MOS transistors using the voltage of their respective gates to adjust the first current and / or the second current.

[0170] The first MOS transistor Q1 can be connected in series with the first switch transistor K1, and the second MOS transistor Q2 can be connected in series with the fourth switch transistor K4. The closing or opening of the first switch transistor K1 can control whether the branch is used to achieve temperature compensation, and the closing or opening of the fourth switch transistor K4 can control whether the branch is used to achieve mode compensation.

[0171] In some embodiments, there are multiple first adjustable current circuits 12, and there are multiple second adjustable current circuits 16. The corresponding relationship between the gate voltage and the conduction current of the first MOS tube Q1 in each first adjustable current circuit 12 is different, and the corresponding relationship between the gate voltage and the conduction current of the second MOS tube Q2 in each second adjustable current circuit 16 is different.

[0172] In this embodiment, multiple first MOS tubes Q1 connected in parallel can achieve multi-speed adjustment of temperature compensation, and multiple second MOS tubes Q2 connected in parallel can achieve multi-speed adjustment of mode compensation, so as to adapt to different power tubes 20. As needed, the first switch tube K1 corresponding to the first MOS tube Q1 and / or the fourth switch tube K4 corresponding to the second MOS tube Q2 can be controlled to be closed or turned off, so that the temperature feedback signal controls a specific number of first MOS tubes Q1, and the working mode signal controls a specific number of second MOS tubes Q2, thereby adjusting the total current flowing through the first resistor R1. For the control of multiple gears, please refer to the above, and this embodiment will not be repeated here.

[0173] Reference Figure 8 , Figure 8The circuit structure of an adjustable protection circuit 10 is shown. In some embodiments, the adjustable protection circuit 10 further includes a first voltage divider circuit 151 and a second voltage divider circuit 152, wherein the first voltage divider circuit 151 is electrically connected to the first adjustable current circuit 12, and is configured to divide the temperature feedback signal of the connected power tube 20, provide a divided first signal, and enable the first adjustable current circuit 12 to provide a first current in response to the first signal; the second voltage divider circuit 152 is electrically connected to the second adjustable current circuit 16, and is configured to divide the working mode signal of the connected switching power supply system, provide a divided second signal, and enable the second adjustable current circuit 16 to provide a second current in response to the second signal; wherein the first voltage divider circuit 151 and the second voltage divider circuit 152 both have an adjustable voltage divider ratio.

[0174] exist Figure 8 In FIG. 1 , V_fbt represents the temperature feedback signal, and V_fbm represents the working mode signal. It can be understood that when the voltage of the temperature feedback signal is the same, the voltage division ratio of the first voltage divider circuit 151 is different, and the voltage of the first signal transmitted to the first adjustable current circuit 12 is different, thereby causing the first current to be different. When the voltage of the working mode signal is the same, the voltage division ratio of the second voltage divider circuit 152 is different, and the voltage of the second signal transmitted to the second adjustable current circuit 16 is different, thereby causing the second current to be different.

[0175] In this embodiment, the first voltage divider circuit 151 and the second voltage divider circuit 152 can both adopt Figure 5 The specific principle of the circuit structure shown can be referred to above, and this embodiment will not be described in detail here.

[0176] Reference Fig. 9 , Fig. 9 A method for overcurrent protection of a power tube is shown. In this embodiment, the overcurrent protection method is applied to the above-mentioned adjustable protection circuit and includes step 10, step 20 and step 30.

[0177] Step 10, obtaining the working feedback voltage and temperature feedback signal of the power tube 20;

[0178] Step 20, adjusting the first current flowing through the first adjustable current circuit according to the temperature feedback signal, so that the sum of the first current and the reference current is converted into a threshold voltage;

[0179] Step 30: When the working feedback voltage is greater than the threshold voltage, the power tube is protected from overcurrent.

[0180] It should be noted that the execution subject of the overcurrent protection method in this embodiment is a controller, which can be electrically connected to the first adjustable current circuit 12 in the aforementioned adjustable protection circuit 10. Of course, the execution subject can also be other subjects that can control the first adjustable current circuit 12.

[0181] The power tube 20 may be provided with a working voltage detection circuit and a temperature detection device (such as a temperature sensor, etc.). The temperature detection device detects the temperature of the power tube 20 itself, or detects the temperature of the environment in which the power tube 20 is located, generates a temperature detection signal, and transmits it to the controller as a temperature feedback signal. The working voltage detection circuit detects the actual working voltage of the power tube 20, and transmits the detection signal to the controller.

[0182] In the above embodiment Figure 3 Taking the circuit structure shown as an example, the gate voltage of the first MOS transistor Q1 in the first adjustable current circuit 12 is controlled by the controller, and the controller adjusts the first current flowing through the first MOS transistor Q1 by adjusting the driving voltage transmitted to the gate of the first MOS transistor Q1.

[0183] The temperature increase of the power tube 20 will increase the internal resistance, thereby reducing the required threshold voltage. When the temperature represented by the temperature feedback signal increases, the controller reduces the first current flowing through the first MOS tube Q1 to compensate for the threshold voltage reduction requirement.

[0184] The controller compares the threshold voltage with the working feedback voltage, and performs overcurrent protection when the working feedback voltage is greater than the threshold voltage, wherein the overcurrent protection may be to shut down the power tube 20 or reduce the actual working voltage of the power tube.

[0185] According to the overcurrent protection method of the power tube 20 of the present application, a threshold voltage is generated according to a reference current and a first current adjusted by a temperature signal of the power tube. By introducing the temperature change of the power tube 20 as compensation for the overcurrent threshold, the power tube 20 at different temperatures can match different overcurrent thresholds, thereby improving the accuracy of overcurrent protection.

[0186] In some embodiments, adjusting the first current flowing through the first adjustable current circuit according to the temperature feedback signal may include: determining a correction gear according to device information of the power tube 20; adjusting the number of opened first adjustable current circuits according to the correction gear, and using the temperature feedback signal to adjust the first current flowing through the opened first adjustable current circuit.

[0187] The device information may include the withstand voltage or current carrying capacity of the power tube 20 itself. When the temperature feedback signal remains unchanged, the threshold voltage corresponding to the first correction gear may be Vth_OC1, and the threshold voltage corresponding to the second correction gear may be Vth_OC2, and Vth_OC1 and Vth_OC2 are different. Since different types of power tubes 20 have different requirements for temperature compensation, different power tubes 20 can be adapted by setting different correction gears. Among them, the relationship between the device information and the correction gear can be set according to the requirements.

[0188] In the above embodiment Figure 3 Taking the circuit structure shown as an example, the controller can control the closing and closing of the first switch K1 connected in series with each first MOS tube Q1 to adjust the correction gear. The temperature feedback signal is applied to the gate of the turned-on first MOS tube Q1 to adjust the first current flowing through each turned-on first MOS tube Q1.

[0189] In some embodiments, obtaining the temperature feedback signal may include: receiving a detection signal of the power tube fed back by a temperature detection unit; determining a voltage division position according to device information of the power tube; and performing voltage division processing on the voltage of the detection signal according to the voltage division position to obtain a temperature feedback signal.

[0190] In this embodiment, the voltage division gear is set to further adapt different power tubes 20. When the detection signal remains unchanged, the voltage division gear may include a first gear and a second gear, the temperature feedback signal corresponding to the first gear may be Va, and the temperature feedback signal corresponding to the second gear may be Vb, and Va and Vb are different.

[0191] In the above embodiment Figure 5 Taking the circuit structure shown as an example, the controller can control the closing and closing of the second switch tube K2 connected in parallel with each voltage-dividing resistor to adjust the voltage-dividing gear.

[0192] Reference Fig.10 , Fig.10 A method for overcurrent protection of a power tube is shown. In this embodiment, the overcurrent protection method is applied to the above-mentioned adjustable protection circuit and includes step 10, step 21, step 22 and step 30.

[0193] Step 10, obtaining the working feedback voltage and temperature feedback signal of the power tube;

[0194] Step 21, obtaining a working mode signal of the switching power supply system;

[0195] Step 22, adjusting the first current flowing through the first adjustable current circuit according to the temperature feedback signal, and adjusting the second current flowing through the second adjustable current circuit according to the working mode signal, so that the sum of the first current, the second current and the reference current is converted into a threshold voltage;

[0196] Step 30: When the working feedback voltage is greater than the threshold voltage, the power tube is protected from overcurrent.

[0197] It should be noted that the execution subject of the overcurrent protection method in this embodiment may also be a controller, which may be electrically connected to the first adjustable current circuit 12 and the second adjustable current circuit 16 in the aforementioned adjustable protection circuit 10. Of course, the execution subject may also be other subjects capable of controlling the first adjustable current circuit 12 and the second adjustable current circuit 16.

[0198] The difference from the above-mentioned overcurrent protection method is that this embodiment not only performs temperature compensation, but also adds a correction of the threshold voltage based on the working mode of the switching power supply system. The working mode signal represents a pulse frequency modulation mode (PFM), a discontinuous conduction mode (DCM), or a continuous conduction mode (CCM).

[0199] In the above embodiment Figure 7 Taking the circuit structure shown as an example, the gate voltages of the first MOS transistor Q1 in the first adjustable current circuit 12 and the second MOS transistor Q2 in the second adjustable current circuit 16 are both controlled by a controller. The controller adjusts the driving voltage transmitted to the gates of the first MOS transistor Q1 and the second MOS transistor Q2, thereby adjusting the first current flowing through the first MOS transistor Q1 and the second current flowing through the second MOS transistor Q2.

[0200] According to the overcurrent protection method of the power tube 200 of the present application, a threshold voltage is generated according to a reference current, a first current adjusted by a temperature signal of the power tube 200, and a second current adjusted by an operating mode signal of a switching power supply system. By introducing the temperature change and the operating mode of the power tube 200 as compensation for the overcurrent threshold, the power tube 200 at different temperatures can match different overcurrent thresholds, and the overcurrent potentials of different operating frequencies and modes can be adjusted and matched in multiple gears, thereby improving the accuracy of overcurrent protection.

[0201] In some embodiments, adjusting the first current flowing through the first adjustable current circuit 12 according to the temperature feedback signal and adjusting the second current flowing through the second adjustable current circuit according to the working mode signal may include: determining a correction gear according to device information of the power tube; adjusting the number of opened first adjustable current circuits 12 and the number of opened second adjustable current circuits according to the correction gear; adjusting the first current flowing through the opened first adjustable current circuit 12 using the temperature feedback signal, and adjusting the second current flowing through the opened second adjustable current circuit using the working mode signal.

[0202] The device information may include the withstand voltage or current carrying capacity of the power tube 20 itself. When the temperature feedback signal remains unchanged, the first correction amplitude corresponding to the first correction gear is X1, and the second correction amplitude is Y1. The threshold voltage at this time may be Vth_OC3. The first correction amplitude corresponding to the second correction gear is X2, and the second correction amplitude is Y2. The threshold voltage at this time may be Vth_OC4, and Vth_OC3 and Vth_OC4 are different. Since different types of power tubes 20 have different requirements for temperature compensation, different power tubes 20 can be adapted by setting different correction gears. Among them, the relationship between the device information and the correction gear can be set according to the requirements.

[0203] In the above embodiment Figure 7 Taking the circuit structure shown as an example, the controller can control the closing and closing of the first switch K1 connected in series with each first MOS tube Q1 and the fourth switch K4 connected in series with each second MOS tube Q2 to adjust the correction gear. The temperature feedback signal is applied to the gate of the first MOS tube Q1 that is turned on to adjust the first current flowing through each first MOS tube Q1 that is turned on. The working mode signal is applied to the gate of the second MOS tube Q2 that is turned on to adjust the second current flowing through each second MOS tube Q2 that is turned on.

[0204] In some embodiments, the acquisition of the temperature feedback signal and the operating mode signal includes: receiving a detection signal of the power tube fed back by a temperature detection unit; receiving a mode signal of the switching power supply system fed back by a mode control unit; determining a first voltage division position and a second voltage division position according to device information of the power tube; performing voltage division processing on the voltage of the detection signal according to the first voltage division position to obtain a temperature feedback signal; performing voltage division processing on the voltage of the mode signal according to the second voltage division position to obtain an operating mode signal.

[0205] In this embodiment, different power tubes 20 are further adapted by setting the voltage division gear. When the detection signal remains unchanged, the voltage division conditions may include two types. In the first voltage division condition, the temperature feedback signal corresponding to the first voltage division gear may be V1a, and the temperature feedback signal corresponding to the second voltage division gear may be V2a; in the second voltage division condition, the temperature feedback signal corresponding to the first voltage division gear may be V1b, and the temperature feedback signal corresponding to the second voltage division gear may be V2b, V1a and V1b are different, and V2a and V2b are different.

[0206] In the above embodiment Figure 5 Taking the circuit structure shown as an example, the temperature feedback signal and the working mode signal are respectively input into two voltage divider circuits 15. The controller can control the closing and closing of the second switch tube K2 in parallel with each voltage divider resistor in the two voltage divider circuits 15 to adjust the voltage divider gear.

[0207] An embodiment of the present application further provides a power management chip 30, including the adjustable protection circuit according to the above. The adjustable protection circuit is integrated inside the power management chip 30. The specific structure and principle of the adjustable protection circuit 10 can refer to the above embodiments, and this embodiment will not be repeated here.

[0208] Reference Fig.11 , Fig.11 An application of a power management chip 30 is shown. The power management chip 30 is connected to a flyback switch power supply circuit. The AC source is sequentially input to the primary side of the transformer after passing through the filter unit and the rectifier unit. The primary side of the transformer is provided with a power tube 20, and the power management chip 30 is connected to the power tube 20. The secondary side of the transformer outputs DC, and the secondary side of the transformer is also provided with an output detection unit.

[0209] According to the power management chip 30 of the present application, a protection circuit with an adjustable threshold is usually used to implement overcurrent protection, which can more accurately protect the driven power tube and avoid damage to the power tube.

[0210] An embodiment of the present application provides a switching power supply circuit, including the aforementioned adjustable protection circuit 10 and a power conversion circuit, wherein the power conversion circuit includes a power tube 20, and the power tube 20 is electrically connected to the adjustable protection circuit 10. The specific structure and principle of the adjustable protection circuit 10 can refer to the aforementioned embodiments, and this embodiment will not be repeated here.

[0211] According to the switching power supply circuit of the present application, a protection circuit with an adjustable threshold is usually used to implement overcurrent protection, which can more accurately protect the driven power tube and avoid damage to the power tube.

[0212] In this article, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be noted that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0213] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An adjustable protection circuit for a power tube, characterized in that: include: a reference current circuit configured to provide a reference current; An impedance unit, wherein a first end of the impedance unit is electrically connected to the reference current circuit, and a second end of the impedance unit is used to connect to a power supply and provide a threshold voltage; at least one first adjustable current circuit, wherein a first end of the first adjustable current circuit is electrically connected to a first end of the impedance unit, a second end of the first adjustable current circuit is electrically connected to a ground node, and the first adjustable current circuit is configured to adjust its own impedance in response to a temperature feedback signal of the power tube to adjust a first current flowing; a voltage clamping circuit, electrically connected to the first end of the impedance unit and configured to clamp the voltage of the first end of the impedance unit at a reference voltage; The overcurrent protection circuit is electrically connected to the second end of the impedance unit and is configured to obtain the working feedback voltage of the power tube and protect the power tube when the working feedback voltage is greater than the threshold voltage.

2. The adjustable protection circuit according to claim 1, characterized in that: The first adjustable current circuit is provided with a switch, and the switch is used to control the connection between the first adjustable current circuit and the impedance unit.

3. The adjustable protection circuit according to claim 2, characterized in that: There are multiple first adjustable current circuits, and signal input ends of the first adjustable current circuits are electrically connected to each other to receive the temperature feedback signal of the power tube.

4. The adjustable protection circuit according to claim 3, characterized in that: The corresponding relationship between the amplitude of the first current of each of the first adjustable current circuits and the amplitude of the temperature feedback signal is different.

5. The adjustable protection circuit according to any one of claims 1 to 4, characterized in that: The first adjustable current circuit includes a first MOS tube, a gate of the first MOS tube is used to access the temperature feedback signal, one end of the source and the drain of the first MOS tube is electrically connected to the ground node, and the other end is electrically connected to the first end of the impedance unit.

6. The adjustable protection circuit according to claim 5, characterized in that: The first adjustable current circuit further includes a first switch tube, a first end of the first switch tube is electrically connected to a first end of the impedance unit, and a second end of the first switch tube is electrically connected to the first MOS tube.

7. The adjustable protection circuit according to claim 6, characterized in that: There are multiple first adjustable current circuits, and the corresponding relationship between the gate voltage and the conduction current of the first MOS transistor in each of the first adjustable current circuits is different.

8. The adjustable protection circuit according to any one of claims 1 to 4, characterized in that: The reference current circuit comprises a current mirror structure, a reference current terminal of the current mirror structure is connected to a reference current, and a replica current terminal of the current mirror structure is electrically connected to a first terminal of the impedance unit.

9. The adjustable protection circuit according to claim 8, characterized in that: The reference current is a PTAT current with a configurable amplitude.

10. The adjustable protection circuit according to any one of claims 1 to 4, characterized in that: The voltage clamp circuit includes a voltage comparator, a first input terminal of the voltage comparator is connected to a reference voltage, a second input terminal of the voltage comparator is electrically connected to a first terminal of the impedance unit, and an output terminal of the voltage comparator is electrically connected to a second input terminal of the voltage comparator.

11. The adjustable protection circuit according to any one of claims 1 to 4, characterized in that: The adjustable protection circuit also includes: a voltage divider circuit, electrically connected to the first adjustable current circuit, and configured to divide the temperature feedback signal of the connected power tube, provide a first signal after voltage division, and enable the first adjustable current circuit to provide the first current in response to the first signal; Wherein, the voltage divider circuit has an adjustable voltage divider ratio.

12. The adjustable protection circuit according to claim 11, characterized in that: The voltage divider circuit includes a plurality of voltage divider resistors connected in series, one end of the voltage divider resistor string is connected to the temperature feedback signal of the power tube, and the other end is electrically connected to the ground node, and the connection node between the voltage divider resistors is used to provide the first signal; Part of the voltage-dividing resistors is connected in parallel with a second switch tube; or, two ends of part of the voltage-dividing resistors are provided with welding points, and the welding points are used to weld fuses.

13. The adjustable protection circuit according to claim 12, characterized in that: The voltage divider circuit further includes: A diode, wherein the anode of the diode is connected to the temperature feedback signal of the power tube, and the cathode of the diode is electrically connected to the voltage-dividing resistor string; The third switch tube is connected in series between the voltage-dividing resistor string and the ground node.

14. The adjustable protection circuit according to any one of claims 1 to 4, characterized in that: The overcurrent protection circuit comprises: A comparison circuit, configured to compare the threshold voltage with the working feedback voltage of the power tube to obtain a comparison result; The driving circuit is electrically connected to the comparison circuit and is configured to perform over-current protection on the power tube according to the comparison result.

15. An adjustable protection circuit for a power tube, characterized in that: The power tube is applied to a switching power supply system, and the adjustable protection circuit includes: a reference current circuit configured to provide a reference current; An impedance unit, wherein a first end of the impedance unit is electrically connected to the reference current circuit, and a second end of the impedance unit is used to connect to a power supply and provide a threshold voltage; at least one first adjustable current circuit, wherein a first end of the first adjustable current circuit is electrically connected to a first end of the impedance unit, a second end of the first adjustable current circuit is electrically connected to a ground node, and the first adjustable current circuit is configured to adjust its own impedance in response to a temperature feedback signal of the power tube to adjust a first current flowing; at least one second adjustable current circuit, wherein a first end of the second adjustable current circuit is electrically connected to a first end of the impedance unit, a second end of the second adjustable current circuit is electrically connected to a ground node, and the second adjustable current circuit is configured to adjust its own impedance in response to an operation mode signal of the switching power supply system to adjust a second current flowing; a voltage clamping circuit, electrically connected to the first end of the impedance unit and configured to clamp the voltage of the first end of the impedance unit at a reference voltage; The overcurrent protection circuit is electrically connected to the second end of the impedance unit and is configured to obtain the working feedback voltage of the power tube and protect the power tube when the working feedback voltage is greater than the threshold voltage.

16. The adjustable protection circuit according to claim 15, characterized in that: The first adjustable current circuit is provided with a first switch, and the first switch is used to control the connection between the first adjustable current circuit and the impedance unit; The second adjustable current circuit is provided with a second switch, and the second switch is used to control the connection between the second adjustable current circuit and the impedance unit.

17. The adjustable protection circuit according to claim 16, characterized in that: There are multiple first adjustable current circuits, and signal input ends of the first adjustable current circuits are electrically connected to each other to receive the temperature feedback signal of the power tube; There are multiple second adjustable current circuits, and signal input ends of the second adjustable current circuits are electrically connected to each other to receive the working mode signal.

18. The adjustable protection circuit according to claim 17, characterized in that: The corresponding relationship between the amplitude of the first current of each of the first adjustable current circuits and the amplitude of the temperature feedback signal is different; The corresponding relationship between the amplitude of the second current of each second adjustable current circuit and the mode represented by the working mode signal is different.

19. The adjustable protection circuit according to claims 15-18, characterized in that: The first adjustable current circuit includes a first MOS tube, and the second adjustable current circuit includes a second MOS tube. The gate of the first MOS tube is used to access the temperature feedback signal, and the gate of the second MOS tube is used to access the working mode signal. One end of the source and the drain of the first MOS tube and the second MOS tube is electrically connected to the ground node, and the other end is electrically connected to the first end of the impedance unit.

20. The adjustable protection circuit according to claim 19, characterized in that: There are multiple first adjustable current circuits, and there are multiple second adjustable current circuits. The corresponding relationship between the gate voltage and the on-current of the first MOS tube in each of the first adjustable current circuits is different, and the corresponding relationship between the gate voltage and the on-current of the second MOS tube in each of the second adjustable current circuits is different.

21. The adjustable protection circuit according to any one of claims 15 to 18, characterized in that: The adjustable protection circuit also includes: a first voltage divider circuit, electrically connected to the first adjustable current circuit, and configured to divide the temperature feedback signal of the connected power tube, provide a first signal after voltage division, and enable the first adjustable current circuit to provide the first current in response to the first signal; a second voltage-dividing circuit, electrically connected to the second adjustable current circuit, and configured to divide the working mode signal of the connected switching power supply system, provide a second signal after voltage division, and enable the second adjustable current circuit to provide the second current in response to the second signal; Wherein, the first voltage-dividing circuit and the second voltage-dividing circuit both have an adjustable voltage-dividing ratio.

22. The adjustable protection circuit according to any one of claims 15 to 18, characterized in that: The mode represented by the working mode signal includes a pulse frequency modulation mode, a discontinuous conduction mode or a continuous conduction mode.

23. A method for overcurrent protection of a power tube, characterized in that: Applied to the adjustable protection circuit according to any one of claims 1 to 14, the overcurrent protection method comprises: Obtain the working feedback voltage and temperature feedback signal of the power tube; adjusting a first current flowing through a first adjustable current circuit according to the temperature feedback signal so that a sum of the first current and a reference current is converted into a threshold voltage; When the working feedback voltage is greater than the threshold voltage, overcurrent protection is performed on the power tube.

24. The overcurrent protection method according to claim 23, characterized in that: The step of adjusting the first current flowing through the first adjustable current circuit according to the temperature feedback signal comprises: Determining a correction gear position according to the device information of the power tube; adjusting the number of the first adjustable current circuits opened according to the correction gear; The temperature feedback signal is used to adjust a first current flowing through the first adjustable current circuit.

25. The overcurrent protection method according to claim 23 or 24, characterized in that: The acquisition of the temperature feedback signal includes: Receive a detection signal of the power tube fed back by a temperature detection unit; Determining a voltage division gear according to device information of the power tube; The voltage of the detection signal is divided according to the voltage division gear to obtain a temperature feedback signal.

26. A method for overcurrent protection of a power tube, characterized in that: Applied to the adjustable protection circuit according to any one of claims 15 to 22, the power tube is applied to a switching power supply system, and the overcurrent protection method comprises: Obtain the working feedback voltage and temperature feedback signal of the power tube; Obtaining an operating mode signal of a switching power supply system; adjusting a first current flowing through a first adjustable current circuit according to the temperature feedback signal, and adjusting a second current flowing through a second adjustable current circuit according to the operating mode signal, so that a sum of the first current, the second current and a reference current is converted into a threshold voltage; When the working feedback voltage is greater than the threshold voltage, overcurrent protection is performed on the power tube.

27. The overcurrent protection method according to claim 26, characterized in that: The step of adjusting the first current flowing through the first adjustable current circuit according to the temperature feedback signal, and adjusting the second current flowing through the second adjustable current circuit according to the working mode signal, comprises: Determining a correction gear position according to the device information of the power tube; adjusting the number of opened first adjustable current circuits and the number of opened second adjustable current circuits according to the correction gear; The temperature feedback signal is used to adjust a first current flowing through the first adjustable current circuit that is turned on, and the operating mode signal is used to adjust a second current flowing through the second adjustable current circuit that is turned on.

28. The overcurrent protection method according to claim 26 or 27, characterized in that: The acquisition of the temperature feedback signal and the working mode signal includes: Receive a detection signal of the power tube fed back by a temperature detection unit; receiving a mode signal of the switching power supply system fed back by a mode control unit; Determine a first voltage division position and a second voltage division position according to the device information of the power tube; Performing voltage division processing on the voltage of the detection signal according to the first voltage division gear to obtain a temperature feedback signal; The voltage of the mode signal is divided according to the second voltage division gear to obtain a working mode signal.

29. A power chip, characterized in that: The method comprises an adjustable protection circuit according to any one of claims 1 to 14, or comprises an adjustable protection circuit according to any one of claims 15 to 22.

30. A switching power supply circuit, characterized in that: It comprises an adjustable protection circuit according to any one of claims 1-14 or comprises an adjustable protection circuit and a power conversion circuit according to any one of claims 15-22, wherein the power conversion circuit comprises a power tube, and the power tube is electrically connected to the adjustable protection circuit.

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