Short circuit detection circuit of switching tube, switching converter and chip

Abstract

The utility model discloses a short circuit detection circuit of a switching tube, a switching converter and a chip, before the circuit is started or enters formal work from a stop state, a lower switching tube is turned on in a preset time period and then turned off, and the frequency of a voltage signal of a common node of an upper bridge type switching tube and a lower bridge type switching tube is detected at the turn-off moment; and when the detected frequency is greater than the frequency threshold, judging that the common node of the upper and lower bridge type switching tubes is short-circuited. The short-circuit detection method for the switching tube is simple and reliable, whether the switching node is short-circuited or not can be accurately judged, the switching tube does not need to be switched on, and the failure risk does not exist.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and more specifically, to a short-circuit detection circuit for a switching transistor, a switching converter, and a chip. Background Technology

[0002] In switching circuits, two bridge switching transistors are often connected together as a switching device, such as... Figure 1 As shown, the bridge switching transistors include an upper switch transistor Q1 and a lower switch transistor Q2. The upper switch transistor is connected to a high potential terminal such as the input voltage terminal Vin, and the lower switch transistor is connected to a low potential terminal such as the ground terminal GND. By controlling the on and off of the two bridge switching transistors, the input power can be converted into output power.

[0003] During the operation of the upper and lower switches in a bridge circuit, if a short circuit occurs in the lower switch or in the line from the node SW of the two switches to ground before the upper switch is turned on, a large instantaneous current will be generated if the upper switch is turned on, causing the switch to overheat and be damaged. Current technology detects the voltage of SW at the moment the upper switch is turned on to check for a short circuit; however, if the short circuit is severe, it can easily cause the switch to fail. Utility Model Content

[0004] In view of this, the purpose of this utility model is to provide a short-circuit detection circuit, a switching converter and chip for a switching transistor, so as to solve the technical problem of inaccurate short-circuit detection of the switching transistor in the prior art.

[0005] According to this application, a short-circuit detection circuit for a switching transistor is applied to a bridge switching transistor circuit system. It includes a switch control circuit and a short-circuit detection circuit. The bridge switching transistor includes an upper switching transistor and a lower switching transistor. One end of the upper switching transistor is connected to a high-potential terminal, and one end of the lower switching transistor is connected to a low-potential terminal. Before the circuit system transitions from a stopped state to normal operation, the switch control circuit controls the lower switching transistor to conduct for a preset time period and then turns it off. The short-circuit detection circuit detects the frequency of the voltage signal at the common node of the bridge switching transistors at the moment the lower switching transistor is turned off. If the detected frequency is greater than a frequency threshold, it determines that a short circuit has occurred at the common node of the bridge switching transistors.

[0006] Preferably, the duration of the preset time period is set to any value between 50ns and 150ns.

[0007] Preferably, the circuit system includes an inductor connected between the common node of the bridge switching transistors and the output terminal of the circuit system. When the common node of the bridge switching transistors is not short-circuited, the parasitic capacitance of the lower switching transistor resonates with the inductor, and the resonant frequency is denoted as the first frequency. When the common node of the bridge switching transistors is short-circuited, the parasitic capacitance of the lower switching transistor resonates with the short-circuited inductor, and the resonant frequency is denoted as the second frequency. The first frequency is less than the second frequency.

[0008] Preferably, the short-circuit detection circuit includes a frequency detection circuit and a frequency comparison circuit. The frequency detection circuit is used to detect the frequency of the voltage signal of the common node of the bridge switch to obtain a frequency detection result. The frequency comparison circuit compares the frequency detection result with a preset frequency threshold to determine that a short circuit has occurred at the common node of the bridge switch based on the comparison result.

[0009] Preferably, entering normal operation from a stopped state includes the circuit system power-on startup state or entering a restart state from a fault state.

[0010] Secondly, a chip is provided, including a bridge switch and the aforementioned short-circuit detection circuit, wherein the bridge switch and the short-circuit detection circuit are integrated into a single chip, or one of the bridge switches and the short-circuit detection circuit are integrated into a single chip.

[0011] Thirdly, a switching converter includes a bridge switch and the aforementioned short-circuit detection circuit. The switching control circuit controls the switching action of the bridge switch to convert input power into output power. The short-circuit detection circuit is used to detect whether a short circuit occurs at the intermediate node of the bridge switch. When a short circuit occurs, the switching control circuit controls the upper switch of the bridge switch to be de-energized.

[0012] Preferably, the switching converter is a buck switching converter.

[0013] Preferably, the switching converter is a multiphase buck switching converter.

[0014] The short-circuit detection circuit, switching converter, and chip of this invention, before the circuit starts up or enters formal operation from a certain stopped state, first turns on the lower switching transistor for a preset time period and then turns it off. At the turn-off moment, the frequency of the voltage signal at the common node of the upper and lower bridge switching transistors is detected. If the detected frequency is greater than a frequency threshold, it is determined that a short circuit has occurred at the common node of the upper and lower bridge switching transistors. The short-circuit detection method of this application is simple and reliable, can accurately determine whether a short circuit has occurred at the switching node, does not require turning on the upper switching transistor, and has no risk of failure. Attached Figure Description

[0015] Figure 1 A circuit block diagram of a prior art switching converter;

[0016] Figure 2 Here is a circuit block diagram of a switching converter according to this utility model;

[0017] Figure 3 This is a circuit block diagram of a first embodiment of the short-circuit detection circuit according to the present invention. Detailed Implementation

[0018] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0019] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these details.

[0020] The present invention will be described in more detail below by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0021] refer to Figure 2 A circuit block diagram of a switching converter according to this utility model and Figure 3 This is a circuit block diagram of a first embodiment of the short-circuit detection circuit according to the present invention. (Reference) Figure 2 As shown, taking a Buck step-down switching converter as an example, the bridge switching transistors include an upper switching transistor Q1 and a lower switching transistor Q2. One end of the upper switching transistor Q1 is connected to a high potential terminal, such as the input voltage terminal VIN, and one end of the lower switching transistor is connected to a low potential terminal, such as ground GND. In this example, the switching converter also includes an inductor Lout, which is connected between the common node SW of the bridge switching transistors and the output terminal of the circuit system. Figure 2As shown, the short-circuit detection circuit according to this application includes a switch control circuit and a short-circuit judgment circuit. Before the circuit system enters normal operation from a stopped state, the switch control circuit controls the lower switch transistor to conduct for a preset time period and then turns it off. Entering normal operation from a stopped state can include the circuit system transitioning from a power-on stop state to a start state, from a fault state to a restart state, or from a standby stop state to the start state of the next switching cycle. Afterwards, the short-circuit judgment circuit detects the frequency of the voltage signal at the common node of the bridge switch transistors at the moment the lower switch transistor is turned off. If the detected frequency is greater than a frequency threshold, it determines that a short circuit has occurred at the common node of the bridge switch transistors. Here, the preset time period is set to any value between 50ns and 150ns. The preset time setting allows a certain current to be generated in the system loop, but it cannot be too long to avoid energy waste. According to the circuit's operating principle, when the common node of the bridge switching transistors is not short-circuited, the parasitic capacitance of the lower switching transistor resonates with the inductor Lout, and the resonant frequency is denoted as the first frequency. When the common node of the bridge switching transistors is short-circuited, the parasitic capacitance of the lower switching transistor resonates with the short-circuited inductor Lshort, and the resonant frequency is denoted as the second frequency. The first frequency is lower than the second frequency. Since the resistance between node SW and ground is very small after a short circuit, the resonant frequency will be much larger.

[0022] Specifically, refer to Figure 3 As shown, the short-circuit detection circuit includes a frequency detection circuit and a frequency comparison circuit. The frequency detection circuit detects the frequency of the voltage signal at the common node of the bridge switching transistor to obtain a frequency detection result. The frequency comparison circuit compares the frequency detection result with a preset frequency threshold to determine whether a short circuit has occurred at the common node of the bridge switching transistor. According to the above description, since the frequency of the voltage signal at the common node differs depending on whether a short circuit has occurred, it can be determined whether a short circuit has occurred at the common node by detecting whether the frequency reaches the frequency threshold. If the short-circuit detection circuit detects a short circuit at the intermediate node of the bridge switching transistor, it generates a comparison result signal VD. The switch control circuit controls the upper switching transistor of the bridge switching transistor to remain off-circuited based on the comparison result VD. The solution implemented in this application will not be turned on before the upper switching transistor is officially turned on, and it will only be turned on after confirming that there is no short circuit, resulting in excellent safety.

[0023] This application also provides a chip including a bridge switch and the aforementioned short-circuit detection circuit, wherein the bridge switch and the short-circuit detection circuit are integrated into a single chip, or one of the bridge switches and the short-circuit detection circuit are integrated into a single chip. Integration can improve the system's size and integration density.

[0024] The above implementation uses a single-phase switching converter as an example, but this application is not limited to this; the switching converter is a multi-phase step-down switching converter. Through the short-circuit test scheme of this application, if a short circuit occurs in one phase of the switching converter, the other phase switching converters can still operate normally, improving working efficiency and the overall safety performance of the system.

[0025] It should be noted that the specific implementation and corresponding illustrations provided are merely one way of describing the implementation method of this utility model, and are not intended to limit the specific structure of the implementation scheme of this utility model. Various changes or modifications can be made to these implementation methods without departing from the principles and essence of this utility model, but all such changes and modifications fall within the protection scope of this utility model.

[0026] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0027] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A short-circuit detection circuit for a switching transistor, applied in a bridge switching transistor circuit system, characterized in that, Includes switch control circuit and short-circuit detection circuit. The bridge switch includes an upper switch and a lower switch, with one end of the upper switch connected to a high potential and one end of the lower switch connected to a low potential. Before the circuit system transitions from a stopped state to full operation, the switch control circuit controls the lower switch transistor to conduct for a preset time period, and then turns it off. The short-circuit detection circuit detects the frequency of the voltage signal at the common node of the bridge switch when the lower switch is turned off. If the detected frequency is greater than the frequency threshold, it determines that a short circuit has occurred at the common node of the bridge switch.

2. The short-circuit detection circuit according to claim 1, characterized in that, The duration of the preset time period is set to any value between 50ns and 150ns.

3. The short-circuit detection circuit according to claim 1, characterized in that, The circuit system includes an inductor connected between the common node of the bridge switch and the output of the circuit system. When the common node of the bridge switch is not short-circuited, the parasitic capacitance of the lower switch resonates with the inductor, and the resonant frequency is denoted as the first frequency. When the common node of the bridge switch is short-circuited, the parasitic capacitance of the lower switch resonates with the short-circuit inductance, and the resonant frequency is denoted as the second frequency. Wherein, the first frequency is less than the second frequency.

4. The short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit includes a frequency detection circuit and a frequency comparison circuit. The frequency detection circuit is used to detect the frequency of the voltage signal at the common node of the bridge switching transistors to obtain the frequency detection result. The frequency comparison circuit compares the frequency detection result with a preset frequency threshold to determine whether a short circuit has occurred at the common node of the bridge switch based on the comparison result.

5. The short-circuit detection circuit according to claim 1, characterized in that, Entering normal operation from a stopped state includes the circuit system starting up or entering a restart state from a fault state.

6. A chip, characterized in that, Includes a bridge-type switching transistor and a short-circuit detection circuit as described in any one of claims 1-5. The bridge switch and the short-circuit detection circuit are integrated into a single chip, or one of the bridge switches and the short-circuit detection circuit are integrated into a single chip.

7. A switching converter, characterized in that, Includes a bridge-type switching transistor and a short-circuit detection circuit as described in any one of claims 1-5. The switching control circuit controls the switching action of the bridge switching transistor to convert the input power into the output power; The short-circuit detection circuit is used to detect whether a short circuit has occurred at the intermediate node of the bridge switch. When a short circuit occurs, the switch control circuit controls the upper switch of the bridge switch to not be turned on.

8. The switching converter according to claim 7, characterized in that, The switching converter is a buck switching converter.

9. The switching converter according to claim 7, characterized in that, The switching converter is a multiphase step-down switching converter.

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