Short circuit detection circuit and step-up / down converter

Abstract

The application discloses a short circuit detection circuit and a buck-boost converter, and belongs to the technical field of integrated circuits. The short circuit detection circuit comprises a first pull-up circuit, a second pull-up circuit, a pull-down circuit and a detection circuit. The first pull-up circuit is connected with the positive electrode of a voltage output end, is used for being turned on when four switch tubes are all turned off, and is used for increasing the voltage of the voltage output end. The second pull-up circuit is connected with two switch nodes respectively, is used for being turned on when the voltage of the voltage output end is increased to a target voltage, and is used for providing the same voltage to the two switch nodes. The pull-down circuit is connected with the two switch nodes and the detection circuit respectively, is used for being turned on when the voltage of the voltage output end is increased to the target voltage, and is used for providing a node voltage to the detection circuit. The detection circuit is used for outputting a detection result of whether the four switch tubes are short-circuited according to the node voltage. The application can perform short circuit detection on the switch tubes, improves the reliability and safety of a converter system, and has a simple circuit structure.

Description

Technical Field

[0001] This application belongs to the field of integrated circuit technology, and in particular relates to a short-circuit detection circuit and a buck-boost converter. Background Technology

[0002] The four-switch buck-boost converter, with its wide input voltage range adaptability and high efficiency, has become a key topology developed by the industry in recent years. However, the alternating conduction characteristic of the four power switches in this topology means that when any one of the switches is short-circuited, a low-resistance DC path will be formed, causing the inductor current or switch current to rise sharply to several times the safety threshold. This abnormally large current will lead to irreversible burn-out of the converter system (such as the power supply system and power devices), seriously threatening the safety and reliability of the converter system. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a short-circuit detection circuit and a buck-boost converter, which can detect short circuits in the switching transistors, improve the reliability and safety of the converter system, and has a simple circuit structure.

[0004] In a first aspect, this application provides a short-circuit detection circuit applied in a buck-boost converter. The buck-boost converter includes a voltage input terminal, a voltage output terminal, four switching transistors, a first switching node, and a second switching node. The first switching node is connected to one of the switching transistors between the positive and negative terminals of the voltage input terminal, and the second switching node is connected to one of the switching transistors between the positive and negative terminals of the voltage output terminal.

[0005] The short-circuit detection circuit includes a first pull-up circuit, a second pull-up circuit, a pull-down circuit, and a detection circuit.

[0006] The first pull-up circuit is connected to the positive terminal of the voltage output terminal and is used to be in a conducting state when all four switching transistors are turned off and the voltage input terminal is connected to a voltage, thereby increasing the voltage of the voltage output terminal.

[0007] The second pull-up circuit is connected to the first switch node and the second switch node respectively, and is used to be in the conducting state when the voltage at the voltage output terminal rises to the target voltage, so as to provide the same voltage to the first switch node and the second switch node;

[0008] The pull-down circuit is connected to the first switch node, the second switch node, and the detection circuit respectively, and is used to be in the on state when the voltage at the voltage output terminal rises to the target voltage, and to provide the node voltage to the detection circuit. The node voltage includes the voltage of the first switch node or the voltage of the second switch node.

[0009] The detection circuit is used to output the detection result of whether the four switching transistors are short-circuited based on the node voltage.

[0010] According to the short-circuit detection circuit of this application, the voltage of the converter's output terminal is increased by a first pull-up circuit, the voltage of the two switching nodes of the converter is provided by a second pull-up circuit, and the voltage of the switching nodes is provided to the detection circuit by a pull-down circuit. The detection circuit outputs the detection result of whether the switching transistor is short-circuited based on the voltage of the switching node, thereby realizing the short-circuit detection of the switching transistor. This prevents the converter from starting when the switching transistor is short-circuited, improving the reliability and safety of the converter system, and the circuit structure is simple.

[0011] According to one embodiment of this application, the second pull-up circuit includes a bootstrap circuit, a first current source, a second current source, a first switching element, and a second switching element;

[0012] The first output terminal of the bootstrap circuit is connected to the first switching node via the first current source and the first switching element connected in series; the second output terminal of the bootstrap circuit is connected to the second switching node via the second current source and the second switching element connected in series.

[0013] According to one embodiment of this application, the pull-down circuit includes a third switching element, a fourth switching element, a first pull-down resistor, and a second pull-down resistor;

[0014] The third switching element and the first pull-down resistor are connected in series between the first switching node and ground, and the fourth switching element and the second pull-down resistor are connected in series between the second switching node and ground.

[0015] The detection circuit is connected to the common connection point of the third switching element and the first pull-down resistor, or the detection circuit is connected to the common connection point of the fourth switching element and the second pull-down resistor.

[0016] According to one embodiment of this application, the third switching element and the fourth switching element respectively include back-to-back transmission gates;

[0017] The input terminal of the back-to-back transmission gate in the third switching element is connected to the first switching node, and the output terminal of the back-to-back transmission gate in the third switching element is grounded through the first pull-down resistor.

[0018] The input terminal of the back-to-back transmission gate in the fourth switching element is connected to the second switching node, and the output terminal of the back-to-back transmission gate in the fourth switching element is grounded through the second pull-down resistor.

[0019] According to one embodiment of this application, the back-to-back transmission gate includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a third current source, a filter capacitor, and a resistor;

[0020] The first transistor and the second transistor are connected in series between the input terminal and the output terminal of the back-to-back transmission gate, and the third transistor and the fourth transistor are connected in series between the input terminal and the output terminal of the back-to-back transmission gate. The control terminals of the first transistor and the second transistor are respectively connected to the first terminal of the fifth transistor. The second terminal of the fifth transistor is grounded through the third current source. The control terminals of the fifth transistor, the third transistor, and the fourth transistor are respectively connected to the enable voltage.

[0021] The filter capacitor is connected between the input terminal of the back-to-back transmission gate and the control terminal of the first transistor, and the resistor is connected in parallel with the filter capacitor.

[0022] The body diode of the first transistor has the opposite conduction direction to the body diode of the second transistor, and the body diode of the third transistor has the opposite conduction direction to the body diode of the fourth transistor.

[0023] According to one embodiment of this application, the short-circuit detection circuit further includes a power generation circuit, which includes a power supply voltage terminal, a first reference voltage terminal, and a second reference voltage terminal.

[0024] The power supply voltage terminal of the power generation circuit is connected to the first pull-up circuit to provide power supply voltage to the first pull-up circuit.

[0025] The first reference voltage terminal and the second reference voltage terminal of the power generation circuit are respectively connected to the detection circuit, and are used to provide the detection circuit with a first reference voltage and a second reference voltage, wherein the first reference voltage is greater than the second reference voltage.

[0026] The detection circuit is also used to compare the node voltage with the first reference voltage and the second reference voltage respectively; if the node voltage is greater than the second reference voltage and less than the first reference voltage, the output detection result is that none of the four switching transistors are short-circuited; otherwise, the output detection result is that at least one of the switching transistors is short-circuited.

[0027] According to one embodiment of this application, the detection circuit includes a comparator, a clamping circuit, a fifth switching element, and a sixth switching element;

[0028] The positive input terminal of the comparator is connected to the pull-down circuit via the clamping circuit, the inverting input terminal of the comparator is connected to the first reference voltage terminal via the fifth switching element, the inverting input terminal of the comparator is also connected to the second reference voltage terminal via the sixth switching element, and the output terminal of the comparator outputs the detection result.

[0029] According to one embodiment of this application, the first pull-up circuit includes a fourth current source and a seventh switching element;

[0030] The input terminal of the fourth current source is connected to the power supply voltage, and the output terminal of the fourth current source is connected to the positive terminal of the voltage output terminal via the seventh switching element.

[0031] Secondly, this application provides a buck-boost converter, including a voltage input terminal, a voltage output terminal, four switching transistors, a first switching node, a second switching node, an inductor, and a short-circuit detection circuit as described above.

[0032] A switching transistor is connected between the first switching node and the positive and negative terminals of the voltage input terminal, and a switching transistor is connected between the second switching node and the positive and negative terminals of the voltage output terminal, and the inductor is connected between the first switching node and the second switching node;

[0033] The first pull-up circuit in the short-circuit detection circuit is connected to the positive terminal of the voltage output terminal, the second pull-up circuit is connected to the first switch node and the second switch node respectively, and the pull-down circuit is connected to the first switch node, the second switch node and the detection circuit respectively.

[0034] According to one embodiment of this application, the buck-boost converter further includes a controller;

[0035] The controller is connected to the four switching transistors, the first pull-up circuit, the second pull-up circuit, the pull-down circuit, and the detection circuit, respectively, and is used to control the four switching transistors, the first pull-up circuit, the second pull-up circuit, the pull-down circuit, and the detection circuit to be in a conducting state or a turning-off state, respectively.

[0036] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects:

[0037] The voltage at the output terminal of the converter is increased by the first pull-up circuit, the voltage is supplied to the two switching nodes of the converter by the second pull-up circuit, and the voltage of the switching nodes is supplied to the detection circuit by the pull-down circuit. The detection circuit outputs the detection result of whether the switching transistor is short-circuited based on the voltage of the switching node, so as to realize the short-circuit detection of the switching transistor and prevent the converter from starting when the switching transistor is short-circuited, thereby improving the reliability and safety of the converter system and the circuit structure is simple.

[0038] Furthermore, by setting back-to-back transmission gates in the pull-down circuit, the conduction directions of the body diodes of the first transistor and the second transistor are opposite, and the conduction directions of the body diodes of the third transistor and the fourth transistor are opposite. When the voltage of the switching node is negative, large transient currents to ground are avoided, thereby avoiding large glitches and improving the reliability of the circuit.

[0039] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0040] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0041] Figure 1 This is a schematic diagram of the buck-boost converter provided in the embodiments of this application;

[0042] Figure 2 This is one of the partial structural schematic diagrams of the short-circuit detection circuit provided in the embodiments of this application;

[0043] Figure 3 This is a second partial structural schematic diagram of the short-circuit detection circuit provided in the embodiments of this application;

[0044] Figure 4 This is a schematic diagram of the back-to-back transmission gate in the short-circuit detection circuit provided in the embodiments of this application. Detailed Implementation

[0045] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0046] The short-circuit detection circuit and buck-boost converter provided in the embodiments of this application are described below with reference to the accompanying drawings.

[0047] This application provides a short-circuit detection circuit that can be applied to a buck-boost converter, specifically a four-switch buck-boost converter. This buck-boost converter can be used in converter systems, such as power supply systems and power devices.

[0048] like Figure 1 As shown, the buck-boost converter includes a voltage input terminal VIN, a voltage output terminal VOUT, four switching transistors, a first switching node SW1, and a second switching node SW2. A switching transistor is connected between the positive and negative terminals of the first switching node SW1 and the voltage input terminal VIN, respectively. Similarly, a switching transistor is connected between the positive and negative terminals of the second switching node SW2 and the voltage output terminal VOUT, respectively.

[0049] The four switching transistors include a first switching transistor M1, a second switching transistor M2, a third switching transistor M3, and a fourth switching transistor M4. The first switching transistor M1 is connected between the first switching node SW1 and the positive terminal of the voltage input VIN. Specifically, the first end of the first switching transistor M1 is connected to the positive terminal of VIN, and the second end is connected to the first switching node SW1. The control terminal of the first switching transistor M1 is connected to the first voltage HS1. The second switching transistor M2 is connected between the first switching node SW1 and the negative terminal of VIN. Specifically, the first end of the second switching transistor M2 is connected to the first switching node SW1, and the second end is connected to the negative terminal of VIN. The control terminal of the second switching transistor M2 is connected to the second voltage LS1. The third switching transistor M3 is connected between the second switching node SW2 and the negative terminal of the voltage output VOUT. Specifically, the first end of the third switching transistor M3 is connected to the second switching node SW2, and the second end is connected to the negative terminal of VOUT. The control terminal of the third switching transistor M3 is connected to the third voltage LS2. The fourth switch M4 is connected between the second switch node SW2 and the positive terminal of the voltage output terminal VOUT. Specifically, the first terminal of the fourth switch M4 is connected to the positive terminal of the voltage output terminal VOUT, and the second terminal of the fourth switch M4 is connected to the second switch node SW2. The control terminal of the fourth switch M4 is connected to the fourth voltage HS2. The negative terminals of the voltage input terminal VIN and the negative terminal of the voltage output terminal VOUT are grounded.

[0050] By controlling the gate voltages (i.e., the first voltage HS1, the second voltage LS1, the third voltage LS2, and the fourth voltage HS2) of the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4, the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4 can be controlled to be in the on or off state respectively.

[0051] In this configuration, the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4 can all be field-effect transistors (FETs). The first terminal of each switch can be the drain of the transistor, the second terminal can be the source of the transistor, and the control terminal can be the gate of the transistor. Each switch can be a P-type FET or an N-type FET. For example, the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4 can all be N-type FETs.

[0052] The buck-boost converter may also include an inductor L, which is connected between the first switching node SW1 and the second switching node SW2.

[0053] The buck-boost converter may also include an input capacitor C. IN and output capacitor C OUT Input capacitor C IN The output capacitor C is connected between the positive and negative terminals of the voltage input terminal VIN. OUT It is connected between the positive and negative terminals of the voltage output terminal VOUT.

[0054] like Figure 1 As shown, the short-circuit detection circuit provided in this application embodiment includes a first pull-up circuit 1, a second pull-up circuit 2, a pull-down circuit 3, and a detection circuit 4.

[0055] The first pull-up circuit 1 is connected to the positive terminal of the voltage output terminal VOUT. It is used to be in the conducting state when all four switching transistors are turned off and the voltage input terminal VIN is connected to a voltage, thereby increasing the voltage of the voltage output terminal VOUT.

[0056] When the buck-boost converter is in standby mode, a short-circuit detection circuit can be used to detect short circuits in the four switching transistors of the buck-boost converter. At this time, all four switching transistors are in the off state. After the voltage input voltage is applied to the voltage input terminal VIN of the buck-boost converter, the first pull-up circuit 1 switches from the off state to the on state, supplying power to the output capacitor C. OUT The system charges the voltage output terminal VOUT until it reaches the target voltage, which can be 3V.

[0057] The second pull-up circuit 2 is connected to the first switch node SW1 and the second switch node SW2 respectively, and is used to be in the conducting state when the voltage at the voltage output terminal VOUT rises to the target voltage, so as to provide the same voltage to the first switch node SW1 and the second switch node SW2.

[0058] When the voltage at the voltage output terminal VOUT reaches the target voltage, the second pull-up circuit 2 switches from the off state to the on state, providing voltage to the first switch node SW1 and the second switch node SW2 respectively, and the voltage provided to the two switch nodes is the same.

[0059] The pull-down circuit 3 is connected to the first switch node SW1, the second switch node SW2 and the detection circuit 4 respectively. It is used to be in the conducting state when the voltage at the voltage output terminal VOUT rises to the target voltage, and to provide the node voltage to the detection circuit 4. The node voltage includes the voltage of the first switch node SW1 or the voltage of the second switch node SW2.

[0060] In this circuit, the voltage of the first switching node SW1 is the same as the voltage of the second switching node SW2. When the voltage at the voltage output terminal VOUT reaches the target voltage, the pull-down circuit 3 switches from the off state to the on state, providing the voltage of either switching node (i.e., the node voltage) to the detection circuit 4.

[0061] The detection circuit 4 is used to output the detection result of whether the four switching transistors are short-circuited based on the node voltage.

[0062] When none of the four switches are short-circuited, the node voltage is a fixed voltage. When any one of the switches is short-circuited, the node voltage changes and is no longer a fixed voltage. Therefore, detection circuit 4 can detect whether the four switches are short-circuited based on the magnitude of the node voltage and output the detection result, thus realizing short-circuit detection of the switches.

[0063] If the test results show that none of the four switching transistors are short-circuited, the buck-boost converter is allowed to be started; if the test results show that any of the switching transistors is short-circuited, the buck-boost converter is prohibited from being started. This is to prevent short-circuit current from damaging the components and causing irreversible burn-out of the transformer system, thereby improving the safety and reliability of the converter system.

[0064] Related technologies achieve short-circuit detection of switching transistors by connecting a resistor in series in the power circuit and employing a combination strategy of multi-node voltage comparison and state logic determination. However, this method has complex detection logic, resulting in a complex circuit structure. It is also highly sensitive to parasitic parameters, requiring complex threshold calibration for specific application scenarios, and has poor versatility and portability.

[0065] In this embodiment, short-circuit detection of the switching transistor can be achieved by comparing node voltages (i.e., single-point voltages), greatly simplifying the detection logic and circuit structure. Moreover, the short-circuit detection circuit in this embodiment can be integrated into the buck-boost converter, reducing the number of external discrete components, shrinking the circuit board area, reducing the size and weight of the device, and avoiding the influence of parasitic capacitance or inductance of external traces and interfaces on the detection results, reducing sensitivity to parasitic parameters, and improving versatility and portability.

[0066] In some embodiments, such as Figure 2 As shown, the first pull-up circuit 1 includes a fourth current source I. VOUT And the seventh switching element S7. The fourth current source I VOUT The input terminal is connected to the power supply voltage, and the fourth current source I VOUT The output terminal is connected to the positive terminal of the voltage output terminal VOUT via the seventh switching element S7.

[0067] When the buck-boost converter is in standby mode, all four switching transistors are off. After the voltage input voltage VIN of the buck-boost converter is applied, the seventh switching element S7 is closed, switching the first pull-up circuit 1 from the off state to the on state. The fourth current source I... VOUT Give the output capacitor C OUT Charge the circuit to increase the voltage at the output terminal VOUT until the voltage at the output terminal VOUT reaches the target voltage.

[0068] In some embodiments, such as Figure 3 As shown, the short-circuit detection circuit also includes a power generation circuit 5, which includes a power supply voltage terminal V. DD The power supply voltage terminal V of power generation circuit 5 DD It is connected to the first pull-up circuit 1 and is used to provide power supply voltage to the first pull-up circuit 1.

[0069] Among them, the power supply voltage terminal V of the power generation circuit 5 DD With the fourth current source I VOUT The input terminal is connected to supply power to the fourth current source I. VOUT The input terminal provides the power supply voltage.

[0070] In some embodiments, such as Figure 2 As shown, the second pull-up circuit 2 includes a bootstrap circuit 21 and a first current source I. SW1 Second current source I SW2 First switching element S1 and second switching element S2.

[0071] The first output terminal BST1 of the bootstrap circuit 21 is connected in series with the first current source I. SW1 The first switching element S1 is connected to the first switching node SW1. The first current source I... SW1 The input terminal is connected to the first output terminal BST1 of the bootstrap circuit 21, and the first current source I SW1 The output terminal of the bootstrap circuit 21 is connected to the first switching node SW1 via the first switching element S1. The second output terminal BST2 of the bootstrap circuit 21 is connected to the second current source I in series. SW2 The second switching element S2 is connected to the second switching node SW2. The second current source I... SW2The input terminal is connected to the second output terminal BST2 of the bootstrap circuit 21, and the second current source I SW2 The output terminal is connected to the second switch node SW2 via the second switch element S2.

[0072] When the voltage at the voltage output terminal VOUT reaches the target voltage, the first switching element S1 and the second switching element S2 are closed, switching the second pull-up circuit 2 from the off state to the on state. The first output terminal BST1 and the second output terminal BST2 of the bootstrap circuit 21 provide voltage; the voltages provided by the first output terminal BST1 and the second output terminal BST2 can be the same or different. The first current source I... SW1 Second current source I SW2 Provide the same current, i.e., I SW1 =I SW2 This is to provide the same voltage to the first switching node SW1 and the second switching node SW1.

[0073] In some embodiments, the pull-down circuit 3 includes a third switching element S3, a fourth switching element S4, and a first pull-down resistor R. A1 Second pull-down resistor R B1 .

[0074] The third switching element S3 and the first pull-down resistor R A1 The fourth switching element S4 and the second pull-down resistor R are connected in series between the first switching node SW1 and ground. B1 It is connected in series between the second switch node SW2 and ground.

[0075] Detection circuit 4, third switching element S3, and first pull-down resistor R A1 Public connection point V S1 The connection, or detection circuit 4, is connected to the fourth switching element S4 and the second pull-down resistor R. B1 Public connection point V S2 connect.

[0076] When the voltage at the voltage output terminal VOUT reaches the target voltage, the third switching element S3 and the fourth switching element S4 are closed, so that the pull-down circuit 3 is switched from the off state to the on state.

[0077] With all four switching transistors not short-circuited, the first current source I SW1 The supplied current flows through the first pull-down resistor R A1 Second current source I SW2 The supplied current flows through the second pull-down resistor R B1 First pull-down resistor R A1 Second pull-down resistor R B1 The resistance values ​​are the same, that is, R A1 =R A2 In addition, ISW1 =I SW2 This ensures that the voltage at the first switching node SW1 is the same as the voltage at the second switching node SW2, both being a fixed voltage I. SW1 *R A1 =I SW2 *R A2 .

[0078] If the first switch M1 or the fourth switch M4 is short-circuited, the voltage at the first switch node SW1 and the voltage at the second switch node SW2 are both equal to the voltage at the voltage input terminal VIN or the voltage at the voltage output terminal VOUT.

[0079] If the second switch M2 or the third switch M3 is short-circuited, the voltage at the first switch node SW1 and the voltage at the second switch node SW2 will both be 0.

[0080] With the third switching element S3 and the fourth switching element S4 closed, the common connection point V S1 The voltage is the voltage at the first switching node SW1, and the voltage at the common connection point V. S2 The voltage at the second switching node SW2 is the same as the voltage at the detection circuit 4 and the common connection point V. S1 Or common connection point V S2 By connecting, the node voltage (i.e., the voltage of the first switching node SW1 or the voltage of the second switching node SW2) can be obtained, and the node voltage can be used to detect whether the four switching transistors are short-circuited.

[0081] In some embodiments, the short-circuit detection circuit further includes a power generation circuit 5, which includes a first reference voltage terminal V. REF1 Second reference voltage terminal V REF2 .

[0082] The first reference voltage terminal V of the power generation circuit 5 REF1 Second reference voltage terminal V REF2 These are connected to the detection circuit 4 respectively, and are used to provide the detection circuit 4 with a first reference voltage and a second reference voltage, wherein the first reference voltage is greater than the second reference voltage. The first reference voltage terminal V... REF1 The provided voltage is the first reference voltage, and the second reference voltage terminal V REF2 The provided voltage is the second reference voltage. The first reference voltage terminal V... REF1 Second reference voltage terminal V REF2 The supplied voltage must satisfy: 0 < V REF2 <I SW1 *R A1 <V REF1 <min{VIN, VOUT}, meaning the first reference voltage is greater than the fixed voltage I. SW1 *R A1And less than the minimum of the voltage at the voltage input terminal VIN and the voltage at the voltage output terminal VOUT; the second reference voltage is greater than 0 and less than the fixed voltage I. SW1 *R A1 .

[0083] The detection circuit 4 is also used to compare the node voltage with the first reference voltage and the second reference voltage respectively; if the node voltage is greater than the second reference voltage and less than the first reference voltage, the output detection result is that none of the four switching transistors are short-circuited; otherwise, the output detection result is that at least one switching transistor is short-circuited.

[0084] If the node voltage is greater than the second reference voltage and less than the first reference voltage, it indicates that the node voltage is a fixed voltage I. SW1 *R A1 None of the four switching transistors are short-circuited. If the node voltage is greater than the first reference voltage, it indicates that the node voltage is equal to the voltage at the voltage input terminal VIN or the voltage at the voltage output terminal VOUT, and the first switching transistor M1 or the fourth switching transistor M4 has a short-circuit fault. If the node voltage is less than the second reference voltage, it indicates that the node voltage is 0, and the second switching transistor M2 or the third switching transistor M3 is short-circuited.

[0085] In some embodiments, the detection circuit 4 includes a comparator comp1, a clamping circuit 41, a fifth switching element S5, and a sixth switching element S6.

[0086] The positive input terminal of comparator comp1 is connected to pull-down circuit 3 via clamping circuit 41, and the inverting input terminal of comparator comp1 is connected to the first reference voltage terminal V via the fifth switching element S5. REF1 The inverting input of comparator comp1 is also connected to the second reference voltage terminal V via the sixth switching element S6. REF2 The output V of comparator comp1 DET Output the detection results.

[0087] The positive input terminal of comparator comp1 is connected to the common connection point V via clamping circuit 41. S1 Or common connection point V S2 The input node voltage is used when pull-down circuit 3 is in the on state. The inverting input of comparator comp1 can be either a first reference voltage or a second reference voltage.

[0088] Comparator comp1 compares the node voltage sequentially with a first reference voltage and a second reference voltage. For example, first closing the fifth switch element S5 and opening the sixth switch element S6, the first reference voltage is input to the inverting input of comparator comp1, and the node voltage is compared with the first reference voltage. If the node voltage is greater than the first reference voltage, the output V of comparator comp1 is then calculated. DETThe output shows the detection result of a short circuit in either the first switch M1 or the fourth switch M4. If the node voltage is less than the first reference voltage, the fifth switch S5 is opened, the sixth switch S6 is closed, and the second reference voltage is input to the inverting input of comparator comp1. The node voltage is compared with the second reference voltage. If the node voltage is less than the second reference voltage, the output of comparator comp1 is V. DET The output shows the detection result of a short circuit in the second switch M2 or the third switch M3; if the node voltage is greater than the second reference voltage, the output of comparator comp1 will be V. DET The output shows that none of the four switching transistors are short-circuited.

[0089] If the test results show that none of the four switching transistors are short-circuited, disconnect the first switching element S1 to the seventh switching element S7, so that the first pull-up circuit 1, the second pull-up circuit 2, the pull-down circuit 3 and the detection circuit are all in the off state. The short circuit test ends and the buck-boost converter can be started, so as to avoid the short circuit detection circuit from affecting the normal operation of the buck-boost converter.

[0090] If the test result shows a short circuit in any of the switching transistors, the buck-boost converter must not be started to avoid damage to the components from the short-circuit current and to improve the safety and reliability of the transformer system.

[0091] In some embodiments, such as Figure 4 As shown, the third switching element S3 and the fourth switching element S4 each include a back-to-back transmission gate.

[0092] The input terminal Sin of the back-to-back transmission gate in the third switching element S3 is connected to the first switching node SW1, and the output terminal Sout of the back-to-back transmission gate in the third switching element S3 is connected to the first pull-down resistor R. A1 Grounding.

[0093] The input terminal Sin of the back-to-back transmission gate in the fourth switching element S4 is connected to the second switching node SW2, and the output terminal Sout of the back-to-back transmission gate in the fourth switching element S4 is connected to the second pull-down resistor R. B1 Grounding.

[0094] When the back-to-back transmission gate in the third switching element S3 is in the ON state, the third switching element S3 is closed; when the back-to-back transmission gate in the third switching element S3 is in the OFF state, the third switching element S3 is turned off. When the back-to-back transmission gate in the fourth switching element S4 is in the ON state, the fourth switching element S4 is closed; when the back-to-back transmission gate in the fourth switching element S4 is in the OFF state, the fourth switching element S4 is turned off.

[0095] This embodiment, by setting a back-to-back transmission gate, can avoid the short-circuit detection circuit from affecting the normal operation of the buck-boost converter.

[0096] In some embodiments, such as Figure 4 As shown, the back-to-back transmission gate includes a first transistor M. A1 Second transistor M A2 Third transistor M A3 Fourth transistor M A4 Fifth transistor M A5 Third current source I A1 Filter capacitor C A1 and resistance R A2 .

[0097] First transistor M A1 Second transistor M A2 The first transistor M is connected in series between the input terminal Sin of the back-to-back transmission gate and the output terminal Sout of the back-to-back transmission gate. A1 The first terminal is connected to the input terminal Sin of the back-to-back transmission gate, and the first transistor M A1 The second terminal is connected to the second transistor M A2 The second terminal, the second transistor M A2 The first terminal is connected to the output terminal Sout of the back-to-back transmission gate. The third transistor M A3 and the fourth transistor M A4 The third transistor M is connected in series between the input terminal Sin and the output terminal Sout of the back-to-back transmission gate. A3 The first terminal is connected to the input terminal Sin of the back-to-back transmission gate, and the third transistor M... A3 The second terminal is connected to the fourth transistor M A4 The second terminal, the fourth transistor M A4 The first end is connected to the output end Sout of the back-to-back transmission gate.

[0098] First transistor M A1 The control terminal and the second transistor M A2 The control terminals are respectively connected to the fifth transistor M A5 The first terminal, the fifth transistor M A5 The second terminal is grounded via the third current source, and the fifth transistor M A5 Control terminal, third transistor M A3 The control terminal and the fourth transistor M A4 The control terminals are connected to the enable voltage EN.

[0099] Among them, the first transistor M A1 Second transistor M A2 Third transistor M A3 Fourth transistor M A4 Fifth transistor M A5All can be field-effect transistors (FETs). The first terminal of each transistor can be the drain, the second terminal can be the source, and the control terminal can be the gate. Each transistor can be a P-type or N-type FET. For example, the first transistor M... A1 Second transistor M A2 All are P-type field-effect transistors, with the third transistor M. A3 Fourth transistor M A4 Fifth transistor M A5 All are N-type field-effect transistors.

[0100] First transistor M A1 The body diode and the second transistor M A2 The conduction direction of the body diode is opposite, and the third transistor M A3 The body diode and the fourth transistor M A4 The conduction direction of the body diode is opposite.

[0101] When the buck-boost converter operates in the dead time of buck mode (the first switch M1, the second switch M2, and the third switch M3 are off, and the fourth switch M4 is on), the inductor current of the buck-boost converter freewheels through the body diode of the second switch M2 and the fourth switch M4. At this time, the voltage of the first switching node SW1 is negative, and the current from ground will flow back to the first switching node SW1, affecting the normal operation of the buck-boost converter.

[0102] This embodiment sets up a back-to-back transmission gate, enabling the first transistor M to... A1 The body diode and the second transistor M A2 The conduction direction of the body diode is opposite, and the third transistor M A3 The body diode and the fourth transistor M A4 The conduction direction of the body diodes is opposite, so even if the voltage of the switching node is negative, a large transient current will not be generated to ground, thus avoiding large glitches and preventing them from affecting the normal operation of the buck-boost converter, thereby improving the reliability of the circuit.

[0103] Filter capacitor C A1 The input terminal Sin of the back-to-back transmission gate is connected to the first transistor M. A1 Between the control terminals, resistor R A2 With filter capacitor C A1 in parallel.

[0104] Among them, the fifth transistor M A5 Third current source I A1 and resistance R A2 Used to bias the first transistor M A1 Second transistor M A2 Filter capacitor CA1 Used for filtering to prevent rapid changes in the first switching node SW1 and the second switching node SW2 when the buck-boost converter performs switching actions, which could lead to false signaling in the back-to-back transmission gate.

[0105] When the enable voltage EN is high (e.g., 5V), the back-to-back transmission gate is turned on, that is, the third switching element S3 and the fourth switching element S4 are closed; when the enable voltage EN is low, the back-to-back transmission gate is turned off, that is, the third switching element S3 and the fourth switching element S4 are turned off.

[0106] The working principle of the back-to-back transmission gate is described in detail below using the back-to-back transmission gate in the third switching element S3 as an example. The first transistor M... A1 Second transistor M A2 The threshold voltages are all V THP The third transistor M A3 and the fourth transistor M A4 The threshold voltages are all V THN The enable voltage EN is set to high.

[0107] When 0 ≤ SW1 < |V THP |At that time, the first transistor M A1 Second transistor M A2 The voltage difference between the source and gate is less than its threshold voltage |V THP | and the third transistor M A3 and the fourth transistor M A4 The voltage difference between the gate and source is greater than its threshold voltage |V THN |, First transistor M A1 Second transistor M A2 Turn off, third transistor M A3 and the fourth transistor M A4 When the back-to-back transmission gate is activated, the third switching element S3 is activated.

[0108] When SW1 > 5V-V THN At that time, the third transistor M A3 and the fourth transistor M A4 The voltage difference between the gate and source is less than its threshold voltage |V THN | and the first transistor M A1 Second transistor M A2 The voltage difference between the source and gate is greater than its threshold voltage |V THP |, First transistor M A1 Second transistor M A2 Turn on, third transistor M A3 and the fourth transistor M A4 When the gate is turned off, the back-to-back transmission gate is turned on, and the third switching element S3 is turned on.

[0109] When |V THP |≤SW1≤5V-V THN At that time, the first transistor M A1 Second transistor M A2 The voltage difference between the source and gate is greater than its threshold voltage |V THP |, third transistor M A3 and the fourth transistor M A4 The voltage difference between the gate and source is greater than its threshold voltage |V THN |, First transistor M A1 Second transistor M A2 Turn on, third transistor M A3 and the fourth transistor M A4 When the back-to-back transmission gate is activated, the third switching element S3 is activated.

[0110] Therefore, when the enable voltage EN is high, the back-to-back transmission gate is turned on regardless of the voltage of the first switching node SW1, and the third switching element S3 is turned on, realizing the transmission of high and low voltages.

[0111] In summary, the short-circuit detection circuit provided in this application raises the voltage at the converter's output terminal through a first pull-up circuit, provides voltage to the two switching nodes of the converter through a second pull-up circuit, and provides the switching node voltage to the detection circuit through a pull-down circuit. This allows the detection circuit to output a detection result indicating whether the switching transistor is short-circuited based on the voltage of the switching node, thereby achieving short-circuit detection of the switching transistor. This prevents the converter from starting when the switching transistor is short-circuited, improving the reliability and safety of the converter system, and the circuit structure is simple.

[0112] Accordingly, this application also provides a buck-boost converter. This buck-boost converter can be applied to converter systems, such as power supply systems and power devices.

[0113] like Figure 1 As shown, the buck-boost converter provided in this application includes a voltage input terminal VIN, a voltage output terminal VOUT, four switching transistors, a first switching node SW1, a second switching node SW2, an inductor L, and a short-circuit detection circuit.

[0114] A switching transistor is connected between the first switching node SW1 and the positive and negative terminals of the voltage input terminal VIN, respectively. Similarly, a switching transistor is connected between the second switching node SW2 and the positive and negative terminals of the voltage output terminal VOUT, respectively. The four switching transistors are: M1, M2, M3, and M4. Switch M1 is connected between the first switching node SW1 and the positive terminal of VIN; switch M2 is connected between the first switching node SW1 and the negative terminal of VIN; switch M3 is connected between the second switching node SW2 and the negative terminal of VOUT; and switch M4 is connected between the second switching node SW2 and the positive terminal of VOUT. The negative terminals of VIN and VOUT are grounded.

[0115] Inductor L is connected between the first switching node SW1 and the second switching node SW2.

[0116] The short-circuit detection circuit includes a first pull-up circuit 1, a second pull-up circuit 2, a pull-down circuit 3, and a detection circuit 4. The first pull-up circuit 1 is connected to the positive terminal of the voltage output VOUT. The second pull-up circuit 2 is connected to the first switching node SW1 and the second switching node SW2, respectively. The pull-down circuit 3 is connected to the first switching node SW1, the second switching node SW2, and the detection circuit 4, respectively. The short-circuit detection circuit is the same as that in the above embodiment, and will not be described in detail here.

[0117] In some embodiments, the buck-boost converter may further include an input capacitor C. IN and output capacitor C OUT Input capacitor C IN The output capacitor C is connected between the positive and negative terminals of the voltage input terminal VIN. OUT It is connected between the positive and negative terminals of the voltage output terminal VOUT.

[0118] In some embodiments, the buck-boost converter further includes a controller (not shown in the figure). The controller is connected to four switching transistors, a first pull-up circuit 1, a second pull-up circuit 2, a pull-down circuit 3, and a detection circuit 4, respectively, and is used to control the four switching transistors, the first pull-up circuit 1, the second pull-up circuit 2, the pull-down circuit 3, and the detection circuit 4 to be in an on or off state, respectively.

[0119] The controller is connected to the control terminals (i.e., gates) of the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4, respectively. By controlling the gate voltages (i.e., the first voltage HS1, the second voltage LS1, the third voltage LS2, and the fourth voltage HS2) of the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4, the controller can control the first switch M1, the second switch M2, the third switch M3, and the fourth switch M4 to be in the on or off state.

[0120] The controller is also connected to the seventh switch element S7 in the first pull-up circuit 1. By controlling the seventh switch element S7 to close or close, the first pull-up circuit 1 can be controlled to be in the on or off state respectively.

[0121] The controller is also connected to the first switching element S1 and the second switching element S2 in the second pull-up circuit 2. By controlling the first switching element S1 and the second switching element S2 to close or close, the second pull-up circuit 2 can be controlled to be in the on or off state respectively.

[0122] The controller is also connected to the third switch element S3 and the fourth switch element S4 in the pull-down circuit 3. By controlling the third switch element S3 and the fourth switch element S4 to close or close, the pull-down circuit 3 can be controlled to be in the on or off state respectively.

[0123] When the third switching element S3 and the fourth switching element S4 each include a back-to-back transmission gate, the controller is respectively connected to the third transistor M A3 Fourth transistor M A4 and the fifth transistor M A5 The control terminal (i.e., the gate) is connected, and the enable voltage EN is controlled, which controls the third transistor M. A3 Fourth transistor M A4 and the fifth transistor M A5 The gate voltage can control the back-to-back transmission gate to be in the on or off state, thereby controlling the pull-down circuit 3 to be in the on or off state.

[0124] The controller is also connected to the fifth switching element S5 and the sixth switching element S6 in the detection circuit 4. By controlling the fifth switching element S5 and the sixth switching element S6 to close or close, the detection circuit 4 can be controlled to be in a conducting state or a turning state. In addition, the controller can also control the fifth switching element S5 and the sixth switching element S6 to close sequentially, so that the detection circuit 4 compares the node voltage with the first reference voltage and the second reference voltage sequentially.

[0125] The controller also connects to the output V of comparator comp1 in detection circuit 4. DETConnect to obtain the detection results output by detection circuit 4, and control each switching tube, each switching element and each transistor according to the detection results.

[0126] According to the buck-boost converter provided in the embodiments of this application, the voltage at the output terminal of the converter is increased by a first pull-up circuit, the voltage is provided to the two switching nodes of the converter by a second pull-up circuit, and the voltage of the switching nodes is provided to the detection circuit by a pull-down circuit. The detection circuit outputs the detection result of whether the switching transistor is short-circuited based on the voltage of the switching node, thereby realizing the short-circuit detection of the switching transistor. When the switching transistor is short-circuited, the converter is prohibited from starting, improving the reliability and safety of the converter system, and the circuit structure is simple.

[0127] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more.

[0128] In the description of this application, "multiple" means two or more.

[0129] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0130] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A short-circuit detection circuit, characterized in that, This is applied in a buck-boost converter, which includes a voltage input terminal, a voltage output terminal, four switching transistors, a first switching node, and a second switching node. The first switching node is connected to one of the switching transistors between the positive and negative terminals of the voltage input terminal, and the second switching node is connected to one of the switching transistors between the positive and negative terminals of the voltage output terminal. The short-circuit detection circuit includes a first pull-up circuit, a second pull-up circuit, a pull-down circuit, and a detection circuit. The first pull-up circuit is connected to the positive terminal of the voltage output terminal and is used to be in a conducting state when all four switching transistors are turned off and the voltage input terminal is connected to a voltage, thereby increasing the voltage of the voltage output terminal. The second pull-up circuit is connected to the first switch node and the second switch node respectively, and is used to be in the conducting state when the voltage at the voltage output terminal rises to the target voltage, so as to provide the same voltage to the first switch node and the second switch node; The pull-down circuit is connected to the first switch node, the second switch node, and the detection circuit respectively, and is used to be in the on state when the voltage at the voltage output terminal rises to the target voltage, and to provide the node voltage to the detection circuit. The node voltage includes the voltage of the first switch node or the voltage of the second switch node. The detection circuit is used to output the detection result of whether the four switching transistors are short-circuited based on the node voltage.

2. The short-circuit detection circuit according to claim 1, characterized in that, The second pull-up circuit includes a bootstrap circuit, a first current source, a second current source, a first switching element, and a second switching element; The first output terminal of the bootstrap circuit is connected to the first switching node via the first current source and the first switching element connected in series. The second output terminal of the bootstrap circuit is connected to the second switching node via the second current source and the second switching element connected in series.

3. The short-circuit detection circuit according to claim 1, characterized in that, The pull-down circuit includes a third switching element, a fourth switching element, a first pull-down resistor, and a second pull-down resistor; The third switching element and the first pull-down resistor are connected in series between the first switching node and ground, and the fourth switching element and the second pull-down resistor are connected in series between the second switching node and ground. The detection circuit is connected to the common connection point of the third switching element and the first pull-down resistor, or the detection circuit is connected to the common connection point of the fourth switching element and the second pull-down resistor.

4. The short-circuit detection circuit according to claim 3, characterized in that, The third switching element and the fourth switching element each include a back-to-back transmission door; The input terminal of the back-to-back transmission gate in the third switching element is connected to the first switching node, and the output terminal of the back-to-back transmission gate in the third switching element is grounded through the first pull-down resistor. The input terminal of the back-to-back transmission gate in the fourth switching element is connected to the second switching node, and the output terminal of the back-to-back transmission gate in the fourth switching element is grounded through the second pull-down resistor.

5. The short-circuit detection circuit according to claim 4, characterized in that, The back-to-back transmission gate includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a third current source, a filter capacitor, and a resistor; The first transistor and the second transistor are connected in series between the input terminal and the output terminal of the back-to-back transmission gate, and the third transistor and the fourth transistor are connected in series between the input terminal and the output terminal of the back-to-back transmission gate. The control terminals of the first transistor and the second transistor are respectively connected to the first terminal of the fifth transistor. The second terminal of the fifth transistor is grounded through the third current source. The control terminals of the fifth transistor, the third transistor, and the fourth transistor are respectively connected to the enable voltage. The filter capacitor is connected between the input terminal of the back-to-back transmission gate and the control terminal of the first transistor, and the resistor is connected in parallel with the filter capacitor. The body diode of the first transistor has the opposite conduction direction to the body diode of the second transistor, and the body diode of the third transistor has the opposite conduction direction to the body diode of the fourth transistor.

6. The short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit also includes a power generation circuit, which includes a power supply voltage terminal, a first reference voltage terminal, and a second reference voltage terminal. The power supply voltage terminal of the power generation circuit is connected to the first pull-up circuit to provide power supply voltage to the first pull-up circuit. The first reference voltage terminal and the second reference voltage terminal of the power generation circuit are respectively connected to the detection circuit, and are used to provide the detection circuit with a first reference voltage and a second reference voltage, wherein the first reference voltage is greater than the second reference voltage. The detection circuit is also used to compare the node voltage with the first reference voltage and the second reference voltage, respectively. If the node voltage is greater than the second reference voltage and less than the first reference voltage, the output detection result is that none of the four switching transistors are short-circuited; otherwise, the output detection result is that at least one of the switching transistors is short-circuited.

7. The short-circuit detection circuit according to claim 6, characterized in that, The detection circuit includes a comparator, a clamping circuit, a fifth switching element, and a sixth switching element; The positive input terminal of the comparator is connected to the pull-down circuit via the clamping circuit, the inverting input terminal of the comparator is connected to the first reference voltage terminal via the fifth switching element, the inverting input terminal of the comparator is also connected to the second reference voltage terminal via the sixth switching element, and the output terminal of the comparator outputs the detection result.

8. The short-circuit detection circuit according to any one of claims 1-7, characterized in that, The first pull-up circuit includes a fourth current source and a seventh switching element; The input terminal of the fourth current source is connected to the power supply voltage, and the output terminal of the fourth current source is connected to the positive terminal of the voltage output terminal via the seventh switching element.

9. A buck-boost converter, characterized in that, It includes a voltage input terminal, a voltage output terminal, four switching transistors, a first switching node, a second switching node, an inductor, and a short-circuit detection circuit as described in any one of claims 1-8; A switching transistor is connected between the first switching node and the positive and negative terminals of the voltage input terminal, and a switching transistor is connected between the second switching node and the positive and negative terminals of the voltage output terminal, and the inductor is connected between the first switching node and the second switching node; The first pull-up circuit in the short-circuit detection circuit is connected to the positive terminal of the voltage output terminal, the second pull-up circuit is connected to the first switch node and the second switch node respectively, and the pull-down circuit is connected to the first switch node, the second switch node and the detection circuit respectively.

10. The buck-boost converter according to claim 9, characterized in that, The buck-boost converter also includes a controller; The controller is connected to the four switching transistors, the first pull-up circuit, the second pull-up circuit, the pull-down circuit, and the detection circuit, respectively, and is used to control the four switching transistors, the first pull-up circuit, the second pull-up circuit, the pull-down circuit, and the detection circuit to be in a conducting state or a turning-off state, respectively.

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