Short circuit detection method, flyback power supply circuit and switching power supply

Abstract

The invention provides a short circuit detection method, a flyback power supply circuit and a switching power supply, and relates to the technical field of switching power supplies. The method comprises the following steps: detecting whether a power tube in a primary side control chip of the flyback power supply circuit meets a preset conduction triggering condition or not; controlling the power tube to be switched off after being switched on for a preset time length, and obtaining a first detection electrical parameter of a preset detection point in a primary circuit of the flyback power supply circuit within the preset time length or a second detection electrical parameter after the power tube is switched off; and according to the first detection electrical parameter or the second detection electrical parameter, determining whether a primary side circuit of the flyback power supply circuit is short-circuited or not. According to the invention, short circuit detection is carried out before the flyback power supply starts working, the reliability is high, and the flyback power supply can be better protected.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to a short circuit detection method, a flyback power supply circuit, and a switching power supply. Background Art

[0002] Flyback power supplies utilize transformers to store energy and release it to the secondary side during the switching cycle. These power supplies are widely used in low-power switching power supplies. The transformer is a key component in flyback power supplies. A short circuit in the transformer can cause the power supply to malfunction at best, or even burn out at worst, seriously impacting equipment operation and personal safety. Therefore, it is necessary to monitor the transformer's function in flyback power supplies to improve system stability.

[0003] The essence of existing transformer short-circuit protection is "work first, judge later." This means it assumes the transformer is functioning normally, then determines if there are any abnormalities, and then decides whether to initiate protection. This logic severely challenges the device hardware's response speed and the current handling capabilities of the flyback power supply's power components. When the input voltage is high, extremely high currents may flow through the transformer during the protection delay, damaging the power supply and endangering personal safety, resulting in poor reliability. Summary of the Invention

[0004] The purpose of this application is to address the deficiencies in the above-mentioned prior art and provide a short-circuit detection method, a flyback power supply circuit and a switching power supply, so that short-circuit detection can be performed before the flyback power supply starts working, which has high reliability and can better protect the flyback power supply.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows: In a first aspect, an embodiment of the present application provides a short circuit detection method, which is applied to a flyback power supply circuit. The method includes: Detecting whether the power tube in the primary side control chip of the flyback power supply circuit meets a preset conduction trigger condition; Controlling the power tube to be turned on for a preset time and then turned off, and obtaining a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within the preset time or a second detection electrical parameter after the power tube is turned off; Determine whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detection electrical parameter or the second detection electrical parameter.

[0006] Optionally, obtaining a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within the preset time period or a second detection electrical parameter after disconnection includes: obtain a first charging current parameter or a second charging current parameter after being disconnected of a high-voltage starting module in the primary side control chip within the preset time length.

[0007] Optionally, the determining whether the primary side circuit of the flyback power supply circuit is short-circuited according to the first detection electrical parameter comprises: if the variation state of the first charging current parameter meets a first variation curve or the first charging current parameter meets a preset current threshold, it is determined that the primary side circuit of the flyback power supply circuit is not short-circuited; if the variation state of the first charging current parameter does not meet the first variation curve or the first charging current parameter does not meet the preset current threshold, it is determined that the primary side circuit of the flyback power supply circuit is short-circuited.

[0008] Optionally, the determining whether the primary side circuit of the flyback power supply circuit is short-circuited according to the second detection electrical parameter comprises: if the second charging current parameter meets a preset current threshold, it is determined that the primary side circuit of the flyback power supply circuit is not short-circuited; if the second charging current parameter does not meet the preset current threshold, it is determined that the primary side circuit of the flyback power supply circuit is short-circuited.

[0009] Optionally, the obtaining the first detection electrical parameter or the second detection electrical parameter after being disconnected of a preset detection point in the primary side circuit of the flyback power supply circuit within the preset time length comprises: obtaining a first induced voltage parameter or a second induced voltage parameter after being disconnected of the primary side auxiliary winding within the preset time length.

[0010] Optionally, the determining whether the primary side circuit of the flyback power supply circuit is short-circuited according to the first detection electrical parameter comprises: if the variation state of the first induced voltage parameter meets a second variation curve or the first induced voltage parameter meets a preset voltage threshold, it is determined that the primary side circuit of the flyback power supply circuit is not short-circuited; if the variation state of the first induced voltage parameter does not meet the second variation curve or the first induced voltage parameter does not meet the preset voltage threshold, it is determined that the primary side circuit of the flyback power supply circuit is short-circuited.

[0011] Optionally, the determining whether the primary side circuit of the flyback power supply circuit is short-circuited according to the second detection electrical parameter comprises: if the second induced voltage parameter meets a preset voltage threshold, it is determined that the primary side circuit of the flyback power supply circuit is not short-circuited; If the second induced voltage parameter does not meet the preset voltage threshold, it is determined that a short circuit occurs in the primary circuit of the flyback power supply circuit.

[0012] In a second aspect, an embodiment of the present application further provides a flyback power supply circuit, the flyback power supply circuit comprising: a transformer and a primary side control chip, the primary side control chip comprising: a high voltage startup module, a power supply module, a control module and a power tube; The primary main winding of the transformer is connected to the input end of the high-voltage startup module and the drain of the power tube respectively, and the primary auxiliary winding of the transformer is connected to the power supply end of the power supply module; The output end of the high-voltage startup module is connected to the input end of the power supply module, the output end of the power supply module is connected to the input end of the control module, the output end of the control module is connected to the gate of the power tube, and the source of the power tube is grounded; The control module is also connected to a preset detection point of the primary circuit, and the control module is used to execute the short-circuit detection method as described in any one of the first aspects to determine whether a short circuit occurs in the primary circuit.

[0013] Optionally, the flyback power supply circuit further includes: a voltage detection module; the voltage detection module is connected to the primary auxiliary winding of the transformer, and the voltage detection module is also connected to the control module.

[0014] In a third aspect, an embodiment of the present application further provides a switching power supply, which includes the flyback power supply circuit as described in the second aspect.

[0015] The beneficial effects of this application are: The present application provides a short-circuit detection method, a flyback power supply circuit, and a switching power supply. When a primary power tube meets a preset conduction trigger condition, the power tube is controlled to be turned on for a preset period of time and then turned off. A first detection electrical parameter at a preset sampling point in the flyback power supply circuit within a preset period of time or a second detection electrical parameter after the power tube is turned off is used to determine whether a short circuit occurs in the primary main winding. If it is determined that a short circuit occurs in the primary main winding, the flyback power supply circuit directly stops working. If it is determined that a short circuit occurs in the primary main winding, the flyback power supply circuit is controlled to start working. In this way, a short-circuit judgment is performed before the flyback power supply circuit starts working, and the flyback power supply circuit can be protected without relying on the response speed of each hardware in the flyback power supply circuit, thereby improving reliability. In addition, this method does not require adding additional components or pins to the flyback power supply circuit, and does not increase the cost of the flyback power supply circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 The principle of the flyback power supply circuit provided in the embodiment of the present application Figure 1 ; Figure 2 The principle of the flyback power supply circuit provided in the embodiment of the present application Figure 2 ; Figure 3 A schematic diagram of a short circuit detection method according to an embodiment of the present invention; Figure 4 A waveform diagram of the primary circuit state provided in an embodiment of the present application; Figure 5 A logic block diagram of current detection provided in an embodiment of the present application; Figure 6 This is a voltage detection logic block diagram provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0019] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0020] In addition, the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0021] It should be noted that, in the absence of conflict, the features in the embodiments of this application can be combined with each other.

[0022] Flyback power supplies utilize transformers to store energy and release it to the secondary side during the switching cycle. These power supplies are widely used in low-power switching power supplies. The transformer is a key component in flyback power supplies. A short circuit in the transformer can cause the power supply to malfunction at best, or even burn out at worst, seriously impacting equipment operation and personal safety. Therefore, it is necessary to monitor the transformer's function in flyback power supplies to improve system stability.

[0023] Currently, transformer short-circuit protection for flyback power supplies primarily relies on primary current detection. This involves using a sampling resistor or current transformer to measure the current flowing through the primary power tube. When the current exceeds the rated peak value, the flyback power supply is judged to be abnormal and the primary power tube is shut down. Alternatively, the slope of the primary current can be detected. If the slope is too high, the flyback power supply is judged to be abnormal and the protection state is triggered.

[0024] The essence of existing transformer short-circuit protection is "work first, judge later." This means it assumes the transformer is functioning normally, then determines if there are any abnormalities, and then decides whether to initiate protection. This logic severely challenges the device hardware's response speed and the current handling capabilities of the flyback power supply's power components. When the input voltage is high, extremely high currents may flow through the transformer during the protection delay, damaging the power supply and endangering personal safety, resulting in poor reliability.

[0025] Based on the above prior art, the present application provides a short circuit detection method, a flyback power supply circuit and a switching power supply. When the primary power tube meets the preset conduction trigger condition, the power tube is controlled to be turned on for a preset time length and then turned off. The first detection electrical parameter in the preset time length at the preset sampling point in the flyback power supply circuit or the second detection electrical parameter after the power tube is turned off is used to determine whether the primary main winding has a short circuit. If it is determined that the primary main winding has a short circuit, the flyback power supply circuit is directly not operated. If it is determined that the primary main winding does not have a short circuit, the flyback power supply circuit is controlled to start operating. In this way, the short circuit is determined before the flyback power supply circuit starts operating, and the flyback power supply circuit can be protected without depending on the response speed of each hardware in the flyback power supply circuit, so that the reliability is higher. In addition, the method does not need to increase additional components or pins in the flyback power supply circuit, and the cost of the flyback power supply circuit is not increased.

[0026] In order to better understand the short circuit detection method provided by the present application, the flyback power supply circuit applied by the present application is introduced.

[0027] Figure 1 Principle of the flyback power supply circuit provided by the embodiment of the present application Figure 1 As shown in Figure 1 , the flyback power supply circuit can include a transformer and a primary control chip U1.

[0028] The transformer includes a primary main winding Np, a primary auxiliary winding Na and a secondary winding Ns. The primary control circuit is packaged as a chip. The pins of the chip include a power supply end pin VDD, a switching end pin SW, a feedback end pin FB, a ground end pin GND, a voltage dividing end pin DMG and a current end CS. Vbulk is the bus voltage. The primary main winding Np is used to store the energy of the primary circuit and release it to the primary auxiliary winding Na and the secondary winding Ns. The primary auxiliary winding Na is responsible for supplying the sensed energy to the chip for operation. The auxiliary winding Ns is responsible for transmitting the sensed energy to the secondary circuit for output.

[0029] Figure 2 Principle of the flyback power supply circuit provided by the embodiment of the present application Figure 2 As shown in Figure 2 , the primary control chip U1 includes a high-voltage starting module, a power supply module, a control module and a power tube.

[0030] The primary main winding of the transformer is connected to the input end of the high-voltage starting module and the drain of the power tube, the primary auxiliary winding of the transformer is connected to the power supply end of the power supply module; the output end of the high-voltage starting module is connected to the input end of the power supply module, the output end of the power supply module is connected to the input end of the control module, the output end of the control module is connected to the gate of the power tube, and the source of the power tube is grounded; the control module is also connected to the preset detection point of the primary circuit, and the control module is used to execute the short-circuit detection method to determine whether the primary circuit is short-circuited.

[0031] In the embodiment, after the flyback power supply circuit starts, the rectifier module in the flyback power supply circuit converts alternating current into direct current, the bus voltage Vbulk is high, the high-voltage starting module starts to work, and the high-voltage starting module starts to charge with the charging current I DD To start charging the power supply module, the voltage of the power supply end pin VDD will continuously increase, and when the voltage of the power supply end pin VDD continuously charges to V DDon After that, the control module generates a gate drive signal to control the power tube to change from the off state to the on state, and turns off after being on for a preset time length.

[0032] The control module can include an abnormality detection unit, a PWM logic unit and a gate drive unit, the abnormality detection unit is used to generate a gate drive signal through the PWM logic unit after the voltage of the power supply end pin VDD continuously charges to V DDon After that, the control module generates a gate drive signal to control the power tube to change from the off state to the on state, and turns off after being on for a preset time length.

[0033] The abnormality detection unit is also used to connect a preset sampling point, obtain a detection electrical parameter, and determine whether the primary circuit of the flyback power supply circuit, i.e. the primary main winding, is short-circuited according to the detection electrical parameter. If it is determined that the primary main winding is not short-circuited, the power tube is controlled to be periodically turned on through the PWM logic unit and the gate drive unit, the flyback power supply circuit formally starts to work, the primary main winding stores energy when the power tube is turned on, and energy is transmitted to the primary auxiliary winding and the secondary winding. If it is determined that the primary main winding is short-circuited, the PWM logic unit no longer generates a gate drive signal, and the flyback power supply circuit stops working.

[0034] In some embodiments, the power supply module can include an energy storage capacitor and an overvoltage and undervoltage detection unit, the overvoltage and undervoltage detection unit determines whether to control the high-voltage starting module to end high-voltage starting according to the voltage value of the energy storage capacitor. When the voltage value of the energy storage capacitor reaches V DDon , the high-voltage starting module can be controlled to end high-voltage starting, and the control module is powered at the same time.

[0035] The charging current I DD of the high-voltage starting module can be determined according to the voltage change rate of the power supply end pin VDD and the capacitance value of the energy storage capacitor.

[0036] Further, such as Figure 2 As shown, the flyback power supply circuit may further include: a voltage detection module, the voltage detection module is connected to the primary auxiliary winding Na of the transformer, and the voltage detection module is connected to the control module.

[0037] Specifically, the voltage detection module includes a resistor R1 and a resistor R2. The connection point of the resistor R1 and the resistor R2 is connected to the control module. The control module can determine the induced voltage of the primary auxiliary winding Na through the resistor R1 and the resistor R2.

[0038] The specific implementation of the short-circuit detection method applied to the above-mentioned flyback power supply circuit is described below in conjunction with embodiments.

[0039] Figure 3 A flow chart of a short circuit detection method provided in an embodiment of the present application is shown in FIG. Figure 3 As shown, the method may include: S101 , detecting whether a power tube in a primary-side control chip in a flyback power supply circuit meets a preset conduction trigger condition.

[0040] In this embodiment, after the flyback power supply circuit is started, the rectifier module in the flyback power supply circuit converts the AC power into DC power, the bus voltage Vbulk is high, and the high-voltage startup module in the primary side control chip starts to work. The high-voltage startup module uses the charging current I DD The power supply module in the primary side control chip starts to charge, and the voltage of the power supply pin VDD will continue to increase.

[0041] The control module in the primary control chip determines whether the voltage of the power supply pin VDD reaches V DDon , when the voltage of the power supply pin VDD reaches V DDon When the power tube meets the preset conduction trigger condition, it is determined that the power tube meets the preset conduction trigger condition.

[0042] S102 , controlling the power tube to be turned on for a preset time and then turned off, and obtaining a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within a preset time or a second detection electrical parameter after the disconnection.

[0043] In this embodiment, when the power tube meets the preset conduction trigger condition, the PWM logic unit in the control module generates a PWM pulse signal, and drives the power tube from the off state to the on state through the gate drive unit in the control module, and controls the power tube to turn off after the preset conduction time, that is, the high level maintenance time of the PWM pulse signal is the preset time.

[0044] The abnormality detection unit in the control module obtains the detection electrical parameter of the preset sampling point. The detection electrical parameter can be the first detection electrical parameter of the preset detection point within the preset time length, or the second detection electrical parameter of the preset detection point after the power tube is disconnected. The first detection electrical parameter is an electrical parameter that changes continuously within the preset time length, and the second detection electrical parameter is a single electrical parameter after the power tube is disconnected.

[0045] It should be noted that the second detected electrical parameter after disconnection should be the detected electrical parameter during the period from when the power tube is disconnected to when the high-voltage starting module ends, rather than the electrical parameter after the high-voltage starting ends.

[0046] S103: Determine whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detected electrical parameter or the second detected electrical parameter.

[0047] In some embodiments, the abnormality detection unit in the control module can determine whether the primary main winding of the flyback power supply circuit is short-circuited based on the change state of the first detection electrical parameter. If the change state of the first detection electrical parameter within the preset time length meets the preset change condition, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited. If the change state of the first detection electrical parameter within the preset time length does not meet the preset change condition, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0048] In other embodiments, the abnormality detection unit in the control module can determine whether the primary main winding of the flyback power supply circuit is short-circuited based on whether the second detection electrical parameter meets the preset parameter threshold. If the second detection electrical parameter meets the preset parameter threshold, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited; if the second detection electrical parameter does not meet the preset parameter threshold, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0049] Furthermore, if it is determined that the primary main winding of the flyback power supply circuit is not short-circuited, the flyback power supply circuit can be controlled to officially enter the operating state. The abnormality detection unit controls the power tube to periodically turn on through the PWM logic unit and the gate drive unit, and the flyback power supply circuit officially begins operation. The primary main winding stores energy when the power tube is turned on, and transfers energy to the primary auxiliary winding and the secondary winding when the power tube is turned off. If it is determined that the primary main winding of the flyback power supply circuit is short-circuited, the PWM logic unit is no longer controlled to generate the gate-level drive signal, and the flyback power supply circuit does not operate.

[0050] The short circuit detection method provided by the above embodiment controls the power tube to be turned on for a preset time length and then turned off, determines whether the primary main winding occurs short circuit by detecting the electrical parameters of the preset sampling point in the flyback power supply circuit, and if it is determined that the primary main winding occurs short circuit, the flyback power supply circuit directly does not work. In this way, the short circuit is determined before the flyback power supply circuit starts to work, the flyback power supply circuit can be protected without relying on the response speed of hardware, and the reliability is higher. Moreover, the method does not need to increase additional components or pins in the flyback power supply circuit, and the cost of the flyback power supply circuit is not increased.

[0051] In a possible implementation, the step of S102 of acquiring the first detection electrical parameter of the preset detection point in the primary circuit of the flyback power supply circuit within a preset time length or the second detection electrical parameter after the power tube is turned off can include: acquiring the first charging current parameter of the high-voltage starting module in the primary control chip within the preset time length or the second charging current parameter after the power tube is turned off.

[0052] In this embodiment, the preset sampling point can be the power supply end of the power supply module, that is, the power supply end pin of the primary control chip. By collecting the current value of the power supply end of the power supply module, the charging current I DD .

[0053] of the high-voltage starting module for charging the power supply module is determined according to the voltage change rate of the power supply end pin VDD and the capacitance value of the energy storage capacitor in the power supply module. DD .

[0054] Specifically, the continuously changing charging current within the preset time length can be collected as the first charging current parameter, and whether the primary main winding of the flyback power supply circuit occurs short circuit is determined according to the first charging current parameter. The charging current after the power tube is turned off can also be collected as the second charging current parameter, and whether the primary main winding of the flyback power supply circuit occurs short circuit is determined according to the second charging current parameter.

[0055] In some embodiments, the process of S103 of determining whether the primary circuit of the flyback power supply circuit occurs short circuit according to the first detection electrical parameter can include: If the change state of the first charging current parameter meets the first change curve or the first charging current parameter meets the preset current threshold, it is determined that the primary circuit of the flyback power supply circuit does not occur short circuit. If the change state of the first charging current parameter does not meet the first change curve or the first charging current parameter meets the preset current threshold, it is determined that the primary circuit of the flyback power supply circuit occurs short circuit.

[0056] In this embodiment, as Figure 2As shown, when the primary main winding is not short-circuited, when the power tube is turned on, the primary main winding is grounded through the power tube, and the charging current I DD Will drop to the preset current threshold I DDth The following is the charging current I of the high-voltage startup module within the preset time period of the power tube being turned on and off. DD Therefore, it is possible to determine whether the primary main winding of the flyback power supply circuit is short-circuited according to the change state of the first charging current parameter, or to determine whether the first charging current parameter drops to a preset current threshold value I within a preset time period. DDth Next, determine whether the primary main winding of the flyback power supply circuit is short-circuited.

[0057] Among them, the first change curve is a descending curve. If the change state of the first charging current parameter satisfies the first change curve, that is, the first charging current parameter is in a descending state within the preset time length, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited. If the change state of the first charging current parameter does not satisfy the first change curve, that is, the first charging current parameter remains unchanged within the preset time length, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0058] If the first charging current parameter within the first preset time period drops to the preset current threshold value I DDth Next, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited. If the first charging current parameter within the preset time period does not drop to the preset current threshold value I DDth Next, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0059] For example, Figure 4 The waveform diagram of the primary circuit state provided in the embodiment of the present application is as follows: Figure 4 As shown, GATE is the driving signal of the power tube, V SW is the voltage of the switching pin SW, V DD is the voltage of the power supply pin VDD, I DD is the charging current of the high voltage startup module, I DDth is the preset current threshold. When the power tube is turned on based on the PWM pulse signal, Figure 4 As shown in (a), if the charging current I DD Drops to the preset current threshold I DDth Next, make sure that the primary main winding of the flyback power supply circuit is not short-circuited, such as Figure 4 As shown in (b), if the charging current I DD Continuously higher than the preset current threshold I DDth , determine that the primary main winding of the flyback power supply circuit is short-circuited.

[0060] In other embodiments, the process of determining whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detected electrical parameter in S103 may include: If the second charging current parameter meets the preset current threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; if the second charging current parameter does not meet the preset current threshold, it is determined that the primary circuit of the flyback power supply circuit is short-circuited.

[0061] In this embodiment, if Figure 2 As shown, when the primary main winding is not short-circuited, when the power tube is turned on, the primary main winding is grounded through the power tube, and the charging current I DD Will drop to the preset current threshold I DDth Therefore, the second charging current parameter can be calculated based on whether it is less than the preset current threshold value I DDth , determine whether the primary main winding of the flyback power supply circuit is short-circuited.

[0062] If the second charging current parameter is less than the preset current threshold I DDth , determine that the primary main winding of the flyback power supply circuit is not short-circuited, if the second charging current parameter is continuously higher than the preset current threshold I DDth , determine that the primary main winding of the flyback power supply circuit is short-circuited.

[0063] For example, after the power tube is turned off based on the PWM pulse signal, Figure 4 As shown in (a), if the charging current I DD Drops to the preset current threshold I DDth Next, make sure that the primary main winding of the flyback power supply circuit is not short-circuited, such as Figure 4 As shown in (b), if the charging current I DD Continuously higher than the preset current threshold I DDth , determine that the primary main winding of the flyback power supply circuit is short-circuited.

[0064] It should be noted that the second charging current parameter after the power tube is turned off should be obtained within a period of time after the power tube is turned off.

[0065] For example, Figure 5 The current detection logic block diagram provided in the embodiment of the present application is as follows: Figure 5 As shown, after the detection starts, the high voltage startup module works with a charging current I DD Charge the power supply module and determine whether the charging voltage at the power supply end reaches V DDon , if the charging voltage at the power supply end reaches V DDon , control the power tube to turn on for a preset time and then turn it off, and judge the charging current I DD Is it down to I DDthIf so, it is determined that the primary circuit state is normal; if not, it is determined that the primary circuit state is abnormal, and then the high-voltage starting module stops working, and the detection ends.

[0066] The short-circuit detection method provided in the above embodiment controls the power tube to be turned on and then disconnected after a preset period of time, and determines whether a short circuit occurs in the primary main winding through the charging current parameter of the high-voltage startup module in the flyback power supply circuit. If it is determined that a short circuit occurs in the primary main winding, the flyback power supply circuit directly stops working. In this way, a short-circuit judgment is performed before the flyback power supply circuit starts working, and the flyback power supply circuit can be protected without relying on the response speed of the hardware, thereby improving reliability. In addition, this method does not require the addition of additional components or pins in the flyback power supply circuit, and does not increase the cost of the flyback power supply circuit.

[0067] In another possible implementation, the step of obtaining the first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within a preset time period or the second detection electrical parameter after disconnection in S102 may include: Obtain a first induced voltage parameter of the primary auxiliary winding within a preset time period or a second induced voltage parameter after disconnection.

[0068] In this embodiment, the charging voltage V DD Reach V DDon After that, the control module generates a gate drive signal to control the power tube to switch from the off state to the on state, and then turn it off after the preset conduction time. During the on-time of the power tube, a current will flow through the primary main winding Np, thereby inducing a negative voltage on the primary auxiliary winding Na.

[0069] The preset sampling point may be a sampling point of a voltage detection module of the primary auxiliary winding. The induced voltage of the primary auxiliary winding is determined by collecting the voltage value of the sampling point of the voltage detection module.

[0070] Specifically, a first induced voltage parameter can be collected as a continuously changing induced voltage over a preset time period, and based on the first induced voltage parameter, whether a short circuit has occurred in the primary main winding of the flyback power supply circuit is determined. Alternatively, a second induced voltage parameter can be collected as a second induced voltage parameter, and based on the second induced voltage parameter, whether a short circuit has occurred in the primary main winding of the flyback power supply circuit is determined.

[0071] In some embodiments, the above S103 determines whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detected electrical parameter, including: If the change state of the first induced voltage parameter satisfies the second change curve, or the first induced voltage parameter satisfies the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; if the change state of the first induced voltage parameter does not satisfy the second change curve, or the first induced voltage parameter does not meet the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is short-circuited.

[0072] In this embodiment, if Figure 2 As shown, when the primary main winding is not short-circuited, after the power tube is turned on, the primary main winding is grounded through the power tube, and a negative voltage is induced on the primary auxiliary winding Na. Then, the induced voltage collected by the voltage sampling module should drop to a negative value, that is, within the preset time period when the power tube is turned on and then turned off, the induced voltage collected by the voltage sampling module is in a downward trend. Therefore, whether the primary main winding of the flyback power supply circuit is short-circuited can be determined based on the change state of the first induced voltage parameter, or it can be determined based on whether the first induced voltage parameter drops to a preset voltage threshold value V within the preset time period. NAth Next, determine whether the primary main winding of the flyback power supply circuit is short-circuited.

[0073] Among them, the second change curve is a descending curve. If the change state of the first induced voltage parameter satisfies the second change curve, that is, the first induced voltage parameter is in a descending state within the preset time length, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited. If the change state of the first induced voltage parameter does not satisfy the second change curve, that is, the first induced voltage parameter remains unchanged within the preset time length, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0074] If the first sensing voltage parameter within the preset time period drops to the preset voltage threshold V NAth Next, it is determined that the primary main winding of the flyback power supply circuit is not short-circuited. If the first induced voltage parameter within the preset time period does not drop to the preset voltage threshold V NAth Next, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0075] For example, Figure 4 As shown in (a), V NA is the induced voltage collected by the voltage sampling module, V NAth is the preset voltage threshold. If the induced voltage V NA drops to the preset voltage threshold V NAth Next, make sure that the primary main winding of the flyback power supply circuit is not short-circuited, such as Figure 4 As shown in (b), if the induced voltage V collected by the voltage sampling module NA Does not drop to the preset voltage threshold V NAth Next, it is determined that the primary main winding of the flyback power supply circuit is short-circuited.

[0076] In some other embodiments, the above S103 of determining whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detected electrical parameter may include: If the second induced voltage parameter meets the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; if the second induced voltage parameter does not meet the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is short-circuited.

[0077] In this embodiment, if Figure 2 As shown, when the primary main winding is not short-circuited, when the power tube is turned on, the primary main winding is grounded through the power tube, and a negative voltage is induced on the primary auxiliary winding Na. The induced voltage collected by the voltage sampling module should drop to a negative value. Therefore, the second induced voltage parameter can be determined based on whether it is less than the preset voltage threshold V NAth , determine whether the primary main winding of the flyback power supply circuit is short-circuited.

[0078] If the second induced voltage parameter is less than the preset voltage threshold V NAth , determine that the primary main winding of the flyback power supply circuit is not short-circuited, if the second induced voltage parameter is continuously higher than the preset voltage threshold V NAth , determine that the primary main winding of the flyback power supply circuit is short-circuited.

[0079] For example, after the power tube is turned off based on the PWM pulse signal, Figure 4 As shown in (a), if the induced voltage V collected by the voltage sampling module NA drops to the preset voltage threshold V NAth Next, make sure that the primary main winding of the flyback power supply circuit is not short-circuited, such as Figure 4 As shown in (b), if the induced voltage V collected by the voltage sampling module NA Maintain the preset voltage threshold V NAth , determine that the primary main winding of the flyback power supply circuit is short-circuited.

[0080] It should be noted that the second induced voltage parameter after the power tube is turned off should be obtained within a period of time after the power tube is turned off.

[0081] For example, Figure 6 The voltage detection logic block diagram provided in the embodiment of the present application is as follows: Figure 6 As shown, after the detection starts, the high voltage startup module works with a charging current I DD Charge the power supply module and determine whether the charging voltage at the power supply end reaches V DDon , if the charging voltage at the power supply end reaches V DDon , control the power tube to turn on for a preset time and then turn it off, and judge the induced voltage V NAWhether it drops to the preset voltage threshold V NAth If so, it is determined that the primary circuit state is normal; if not, it is determined that the primary circuit state is abnormal, and then the high-voltage starting module stops working, and the detection ends.

[0082] The short-circuit detection method provided in the above embodiment controls the power tube to be turned on and then turned off after a preset period of time, and determines whether a short circuit occurs in the primary main winding through the sensing parameters of the voltage sampling module in the flyback power supply circuit. If it is determined that a short circuit occurs in the primary main winding, the flyback power supply circuit directly stops working. In this way, a short-circuit judgment is performed before the flyback power supply circuit starts working, and the flyback power supply circuit can be protected without relying on the response speed of the hardware, thereby improving reliability. In addition, this method does not require the addition of additional components or pins in the flyback power supply circuit, and does not increase the cost of the flyback power supply circuit.

[0083] Based on the short-circuit detection method provided in the above embodiment and the flyback power supply circuit using the short-circuit detection method, this embodiment also provides a switching power supply, which includes the flyback power supply circuit of the above embodiment. The flyback power supply circuit executes the above short-circuit detection method, performs short-circuit detection on the primary circuit, and does not operate if it is determined that the primary circuit is short-circuited.

[0084] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited to them. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A short circuit detection method, characterized in that: Applied to a flyback power supply circuit, the method includes: Detecting whether the power tube in the primary side control chip of the flyback power supply circuit meets a preset conduction trigger condition; Controlling the power tube to be turned on for a preset time and then turned off, and obtaining a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within the preset time or a second detection electrical parameter after the power tube is turned off; Determine whether a short circuit occurs in the primary circuit of the flyback power supply circuit according to the first detection electrical parameter or the second detection electrical parameter.

2. The method according to claim 1, wherein The obtaining of a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within the preset time period or a second detection electrical parameter after disconnection includes: The first charging current parameter of the high-voltage startup module in the primary-side control chip within the preset time period or the second charging current parameter after disconnection is obtained.

3. The method according to claim 2, wherein The determining, based on the first detected electrical parameter, whether a short circuit occurs in the primary circuit of the flyback power supply circuit includes: If the change state of the first charging current parameter satisfies a first change curve, or the first charging current parameter satisfies a preset current threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; If the change state of the first charging current parameter does not satisfy the first change curve, or the first charging current parameter does not satisfy the preset current threshold, it is determined that a short circuit occurs in the primary circuit of the flyback power supply circuit.

4. The method according to claim 2, wherein The determining, based on the second detected electrical parameter, whether a short circuit occurs in the primary circuit of the flyback power supply circuit includes: If the second charging current parameter meets the preset current threshold, determining that the primary circuit of the flyback power supply circuit is not short-circuited; If the second charging current parameter does not meet the preset current threshold, it is determined that a short circuit occurs in the primary circuit of the flyback power supply circuit.

5. The method according to claim 1, wherein The obtaining of a first detection electrical parameter of a preset detection point in the primary circuit of the flyback power supply circuit within the preset time period or a second detection electrical parameter after disconnection includes: A first induced voltage parameter of the primary auxiliary winding within the preset time period or a second induced voltage parameter after disconnection is obtained.

6. The method according to claim 5, wherein The determining, based on the first detected electrical parameter, whether a short circuit occurs in the primary circuit of the flyback power supply circuit includes: If the change state of the first induced voltage parameter satisfies the second change curve, or the first induced voltage parameter satisfies the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; If the change state of the first induced voltage parameter does not satisfy the second change curve, or the first induced voltage parameter does not satisfy the preset voltage threshold, it is determined that a short circuit occurs in the primary circuit of the flyback power supply circuit.

7. The method according to claim 5, wherein The determining, based on the second detected electrical parameter, whether a short circuit occurs in the primary circuit of the flyback power supply circuit includes: If the second induced voltage parameter meets the preset voltage threshold, it is determined that the primary circuit of the flyback power supply circuit is not short-circuited; If the second induced voltage parameter does not meet the preset voltage threshold, it is determined that a short circuit occurs in the primary circuit of the flyback power supply circuit.

8. A flyback power supply circuit, characterized in that: The flyback power supply circuit includes: a transformer and a primary side control chip, and the primary side control chip includes: a high voltage startup module, a power supply module, a control module and a power tube; The primary main winding of the transformer is connected to the input end of the high-voltage startup module and the drain of the power tube respectively, and the primary auxiliary winding of the transformer is connected to the power supply end of the power supply module; The output end of the high-voltage startup module is connected to the input end of the power supply module, the output end of the power supply module is connected to the input end of the control module, the output end of the control module is connected to the gate of the power tube, and the source of the power tube is grounded; The control module is further connected to a preset detection point of the primary circuit, and is configured to execute the short-circuit detection method according to any one of claims 1 to 7 to determine whether a short circuit occurs in the primary circuit.

9. The flyback power supply circuit according to claim 8, wherein: The flyback power supply circuit further includes: a voltage detection module; the voltage detection module is connected to the primary auxiliary winding of the transformer, and the voltage detection module is also connected to the control module.

10. A switching power supply, characterized in that: The switching power supply includes the flyback power supply circuit according to claim 8 or 9.

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