Magnetic element short-circuit protection device in flyback system, flyback conversion system and chip

Abstract

The invention discloses a magnetic element short-circuit protection device in a flyback system, a flyback conversion system and a chip. The device comprises a current sampling module and a detection protection module, the detection protection module comprises a sampling signal processing circuit, a logic control circuit, a driving circuit and a voltage following circuit; the current sampling module samples primary side current of the transformer to obtain sampling current; the sampling signal processing circuit outputs a control signal to the logic control circuit according to the magnitude of the sampling current; the logic control circuit inputs a PWM signal, outputs a switch control signal to the driving circuit, and outputs segmented time to the voltage following circuit; the voltage following circuit outputs a following control signal to the driving circuit according to the segmented time; the drive circuit generates a gate drive voltage of the primary switch tube according to the switch control signal and controls the size of the drive voltage through the following control signal. According to the scheme, short-circuit protection of the primary side current of the transformer in the flyback system can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of switching power supply, in particular to a magnetic element short circuit protection device in flyback system, a flyback conversion system and a chip. BACKGROUND

[0002] The flyback converter is a key component in the flyback system, which has the functions of energy storage, energy transmission, voltage conversion and electrical isolation, realizes the conversion and isolation between alternating current (AC) and direct current (DC), and stabilizes the direct current voltage. The traditional flyback converter usually does not have the function of magnetic element short circuit protection. In the application of smart meters, if the magnetic element is short-circuited, the chip will be broken down because the primary input voltage of the flyback converter is as high as 1100Vdc. Since the modern smart meter power supply system has higher requirements for reliability, the magnetic element protection function is more important.

[0003] In the application of smart meters, there are usually two types of flyback converter systems, one is a CS (Current Sense, current detection) resistance external system, and the other is a CS resistance integrated system.

[0004] In the CS resistance external system, the CS resistance is usually connected between the source of the primary switch tube (usually a MOSFET) and the ground. The main technical solution for transformer protection at present is to determine the primary current size by sampling the voltage drop on the CS resistance, so as to judge whether the system is in normal working state. This scheme mainly has the following defects: (1) the CS resistance is determined by the system, that is, the CS resistance is adjustable, so the protection threshold ( , wherein is the CS pin voltage, is the current on the CS resistance) is affected by the CS resistance; when the CS resistance is small, the protection current is large, which is easy to break down the primary switch tube; when the CS resistance is large, the protection current is small, but it is easy to be triggered by the opening peak. When the magnetic element is short-circuited, the primary switch tube will immediately enter the saturation state, and the saturation current will reach tens of amperes (A) in an instant, so the CS pin voltage is easy to exceed the CS pin voltage, thereby breaking down the CS pin.

[0005] For the CS resistance integrated system, the main technical solution for magnetic element short circuit protection at present is to sample the primary current through the sampling tube of the primary switch tube, so as to judge whether the system is in normal working state. This scheme also has the following defects: (1) in the CS resistance integrated system, the source of the primary switch tube is connected to the ground, so the gate-source voltage of the primary switch tube When the primary side of the transformer is short-circuited, the saturation current of the primary switch tube is larger, so the primary switch tube is easily broken down when high voltage is input. When the primary side of the transformer is short-circuited, the main tube (i.e. the primary switch tube) and the sampling tube both work in a saturation state, and the source end of the main tube is grounded, while the source end of the sampling tube is connected to a sampling resistor, so the gate-source voltage of the main tube and the sampling tube There is a difference, which causes the sampling ratio to change greatly at this time, so that the primary side current of the transformer cannot be accurately sampled, thereby causing the protection to be unable to be accurately triggered. SUMMARY

[0006] The embodiment of the present application provides a magnetic element short-circuit protection device in a flyback system, a flyback conversion system and a chip, so as to accurately detect the primary side current of the transformer in the flyback system and realize effective short-circuit protection.

[0007] In one aspect, the embodiment of the present application provides a magnetic element short-circuit protection device in a flyback system, the flyback system comprising an oscillator, a primary switch tube and a transformer; the device comprising a current sampling module and a detection protection module; the detection protection module comprising a sampling signal processing circuit, a logic control circuit, a driving circuit and a voltage follower circuit;

[0008] The current sampling module comprises a sampling tube coupled with the primary side of the transformer and the primary switch tube, for sampling the primary side current of the transformer to obtain a sampling current;

[0009] The sampling signal processing circuit is configured to output a control signal to the logic control circuit according to the size of the sampling current, so as to control the logic control circuit to be turned on or turned off;

[0010] The logic control circuit is configured to input a PWM signal generated by the oscillator, output a switch control signal to the driving circuit, and output a segmented time to the voltage follower circuit;

[0011] The voltage follower circuit is configured to output a follow-up control signal to the driving circuit according to the segmented time;

[0012] The driving circuit is configured to generate a gate driving voltage of the primary switch tube according to the switch control signal, so as to drive the primary switch tube to be turned on or turned off, and control the size of the driving voltage through the follow-up control signal.

[0013] Optionally, the sampling tube is a MOS tube, the gate of the MOS tube is connected with the gate of the primary switch tube, the drain of the MOS tube is connected with the primary side of the transformer, and the source of the MOS tube is connected with the sampling signal processing circuit.

[0014] Optionally, the voltage follower circuit adjusts the gate-source voltage of the primary switch to a first voltage during a first time period and a second voltage during a second time period, based on the segmented time; the second voltage is greater than the first voltage.

[0015] Optionally, the sampling signal processing circuit includes:

[0016] A voltage generation unit is used to generate a detection voltage based on the sampled current;

[0017] A comparator is used to compare the detected voltage with a reference voltage. When the detected voltage is greater than the reference voltage, a control signal is output to the logic control circuit to turn off the logic control circuit.

[0018] Optionally, the sampling signal processing circuit includes:

[0019] A current mirror is used to replicate the sampled current proportionally to obtain a replicated current.

[0020] The comparison unit is used to compare the replicated current with the reference current. When the replicated current is greater than the reference current, it outputs a control signal to the logic control circuit to turn off the logic control circuit.

[0021] Optionally, the current sampling circuit further includes a sampling resistor connected between the source of the primary switching transistor and ground to generate a sampling voltage;

[0022] The voltage follower circuit includes: a first-stage follower unit and a second-stage follower unit;

[0023] The first-stage following unit is used to perform voltage following within the first time period based on the sampled voltage within the segmented time period;

[0024] The second-stage following unit is used to perform voltage following within the second time period based on the sampled voltage after the segmented time ends.

[0025] Optionally, the source of the primary switching transistor is grounded;

[0026] The voltage follower circuit includes: a segmented clamping unit;

[0027] The segmented clamping unit is used to output a follow control signal according to the segmented time, so as to clamp the driving voltage output by the driving circuit to the first voltage and the second voltage respectively during the first time period and the second time period.

[0028] Optionally, the segmentation time is determined based on the switching speed of the primary switching transistor.

[0029] Optionally, the segmented time is the time it takes for the gate voltage of the primary switch to rise from 0 to its threshold voltage.

[0030] Optionally, the driving circuit includes: a driving logic unit, an upper driving transistor, and a lower driving transistor.

[0031] On the other hand, embodiments of this application also provide a flyback converter system, including a short-circuit protection device for magnetic components in the flyback system.

[0032] On the other hand, embodiments of this application also provide a chip, including a sampling signal processing circuit, a logic control circuit, a driving circuit, and a voltage follower circuit;

[0033] The sampling signal processing circuit is used to output a control signal to the logic control circuit according to the magnitude of the sampling current, so as to control the logic control circuit to turn on or off.

[0034] The logic control circuit is used to input PWM signals, output switching control signals to the drive circuit, and output segmented time signals to the voltage follower circuit.

[0035] The voltage follower circuit is used to output a follower control signal to the drive circuit according to the segmented time.

[0036] The driving circuit is used to generate a gate driving voltage for the primary switch transistor according to the switch control signal, so as to drive the primary switch transistor to turn on or off, and to control the magnitude of the driving voltage through the follower control signal.

[0037] The short-circuit protection device for magnetic components in the flyback system provided in this application uses a MOSFET to sample the current of the primary switch on the primary side of the transformer to obtain the sampled current. This solves the problem in traditional methods where the protection threshold is affected by the CS resistor when sampling the transformer primary current. Simultaneously, a voltage follower circuit clamps the gate-source voltage of the primary switch to reduce the saturation current of the primary switch within segmented time periods. For example, during the first sampling time period, the gate-source voltage of the primary switch is... ( This reduces the saturation current of the primary switch when a short circuit occurs in the magnetic components, ensuring that the primary switch is not damaged. After the first time period, if no short circuit condition is detected, the second time period begins, at which point the gate-source voltage of the primary switch is... This voltage ensures that the primary switch is fully turned on, reducing conduction losses. Through voltage following, the gate-source voltages of both the sampling transistor and the primary switch are kept constant when the primary switch is turned on. This ensures that the sampling ratio remains constant during magnetic component short-circuit conditions, allowing the sampling transistor to accurately sample the transformer's primary current and achieving effective short-circuit protection. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a short-circuit protection device for magnetic components in a flyback system provided in an embodiment of this application;

[0040] Figure 2 This is a schematic diagram of a specific structure of a short-circuit protection device for magnetic components in a flyback system provided in this application embodiment;

[0041] Figure 3 yes Figure 2 The waveform diagram shown is of the short-circuit protection device for magnetic components in the flyback system protecting the transformer from short circuit.

[0042] Figure 4 This is another specific structural schematic diagram of the short-circuit protection device for magnetic components in the flyback system provided in the embodiments of this application;

[0043] Figure 5 yes Figure 4 The waveform diagram shown is of the short-circuit protection device for magnetic components in the flyback system protecting the transformer from short circuit.

[0044] Figure 6 This is another specific structural schematic diagram of the short-circuit protection device for magnetic components in the flyback system provided in the embodiments of this application. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] In a flyback converter, an oscillator generates a fixed-frequency PWM (Pulse Width Modulation) signal to drive the primary switch to turn on and off. Through the switching of the primary switch, the DC voltage is converted into a high-frequency square wave voltage, which is applied to the primary winding of the transformer. The transformer not only performs voltage transformation and isolation but also has an energy storage function. Specifically, when the primary switch is on, the input voltage is applied to the primary winding of the transformer, and the transformer stores energy; when the primary switch is off, the energy stored in the transformer is released to the load.

[0047] To address the problems of existing CS detection schemes in flyback converter systems, this invention provides a short-circuit protection device for magnetic components in a flyback system. It uses a MOSFET to sample the current of the primary switch on the primary side of the transformer to obtain the sampled current, ensuring that the protection threshold is not affected by the CS resistor. Simultaneously, a voltage follower circuit clamps the following voltage, reducing the saturation current of the primary switch when a magnetic component short circuit occurs, ensuring that the primary switch is not damaged. Furthermore, the sampling ratio remains constant during magnetic component short circuit conditions, enabling the sampling transistor to accurately sample the primary current of the transformer.

[0048] like Figure 1 The diagram shown is a structural schematic of a short-circuit protection device for magnetic components in a flyback system provided in an embodiment of this application.

[0049] The short-circuit protection device for magnetic components in this flyback system includes a current sampling module 10 and a detection and protection module 20. The detection and protection module 20 includes a sampling signal processing circuit 21, a logic control circuit 22, a drive circuit 23, and a voltage follower circuit 24.

[0050] In practical implementation, the aforementioned detection and protection module 20 and current sampling module 10 can be integrated into the same chip. For example... Figure 1 As shown in the diagram, for ease of description, the connection point between the current sampling module 10 and the sampling signal processing circuit 21 is referred to as node A, the connection point between the current sampling module 10 and the drive circuit 23 is referred to as node B, and the connection point between the current sampling module 10 and the voltage follower circuit 24 is referred to as node C. The sampling signal processing circuit 21 receives the sampled current output by the current sampling module 10 through node A. The driving circuit 23 outputs a driving voltage to the current sampling module 10 through node B. The voltage follower circuit 24 receives the sampled voltage output by the current sampling module 10 through node C. The logic control circuit 22 can integrate feedback control logic and protection logic.

[0051] The current sampling module 10 includes a sampling transistor coupled to the primary side of the transformer and the primary switching transistor, used to sample the primary current of the transformer to obtain the sampled current. ;

[0052] The sampling signal processing circuit 21 is used to process the sampling current. The output control signal CMP_OUT is sent to the logic control circuit 22 to control the logic control circuit 22 to turn it on or off;

[0053] The logic control circuit 22 is used to input the PWM signal generated by the oscillator, output the switching control signal to the drive circuit 23, and output the segmented time. To voltage follower circuit 24;

[0054] Voltage follower circuit 24 is used to follow the time intervals. Output follow control signal To drive circuit 23;

[0055] The drive circuit 23 is used to generate the gate drive voltage of the primary switch transistor according to the switch control signal. To drive the primary switch to turn on or off, and by following the control signal Control drive voltage The size of the voltage. Specifically, the driving voltage can be controlled. The gate-source voltage of the primary switch varies with the source voltage of the primary switch, keeping the gate-source voltage of the primary switch constant during the primary switch's conduction period; or the drive voltage is controlled. Clamped at different voltage values ​​in different voltage follower stages.

[0056] During the conduction period of the primary switch, due to the drive voltage The gate-source voltage of the primary switch varies with the source voltage of the primary switch, keeping the gate-source voltage of the primary switch constant during the primary switch's conduction period, or the drive voltage varies accordingly. The clamping is maintained at a certain size, preventing an increase in the saturation current of the primary switching transistor when the magnetic component is short-circuited, thus ensuring the safety of the primary switching transistor. Furthermore, upon detecting a short circuit on the primary side of the transformer, the logic control circuit is immediately shut down, causing the drive circuit to stop outputting the drive voltage. This effectively achieves short-circuit protection and ensures the safety of the flyback system.

[0057] like Figure 2 The diagram shown is a specific structural schematic of a short-circuit protection device for magnetic components in a flyback system provided in an embodiment of this application.

[0058] In this embodiment, the primary winding of the transformer in the flyback system The primary switching transistor Q1 and the sampling transistor Q2 are connected. The sampling transistor Q2 is a MOSFET, and its gate is connected to the gate of the primary switching transistor Q1. The drain of the sampling transistor Q2 is connected to the primary side of the transformer. The source of sampling transistor Q2 is connected to the sampling signal processing circuit 21, and a primary current sampling resistor is also connected between the source of primary switching transistor Q1 and ground. This is used to sample the source voltage of the primary switch Q1 to obtain the sampled voltage. , sample voltage Output to voltage follower circuit 24.

[0059] The system input voltage, The operating voltage is 100 ohms. Resistor R1, capacitor C1 and diode D1 form an RCD (Resistor Capacitor Diode) absorption network to limit the drain spike voltage of the primary switch Q1 in the switching state.

[0060] In this embodiment, the primary switch Q1 and the sampling resistor The first sampling branch is formed, and sampling tube Q2 is the second sampling branch. Assume the sampling ratio of the first and second sampling branches is... The current flowing through the primary switch Q1 is... With sampling current The relationship is: .

[0061] In this embodiment, the sampling signal processing circuit 21 includes: a voltage generation unit (such as...) Figure 2 The sampling resistor in ) and comparator CMP. Where:

[0062] The voltage generation unit is used to generate voltage based on the sampled current. Generate detection voltage Imminent sampling current Converted into detection voltage , .

[0063] The comparator CMP receives the detected voltage at its positive input terminal. The negative input terminal receives the reference voltage. In detecting voltage Greater than the reference voltage When this occurs, the output control signal CMP_OUT is sent to the logic control circuit 22 to shut down the logic control circuit 22, causing it to stop outputting the switch control signal. Figure 2 In the embodiment shown, when CMP_OUT is 1, the logic control circuit 22 is in a disabled state, the output of the drive circuit 23 is 0, and the primary switch Q1 and the sampling tube Q2 are turned off.

[0064] Reference voltage Based on the saturation current of the primary switch Q1 Chip overcurrent point Sampling ratio K and sampling resistor The decision is made if the following conditions are met:

[0065] .

[0066] During normal operation, the voltage is detected. Less than the reference voltage Then the minimum gate-source voltage of sampling transistor Q2 is Therefore, the maximum difference between the gate-source voltages of the primary switch Q1 and the sampling transistor Q2 is _____. Reference voltage Magnitude and sampling resistor Related, for example, can generally be set This ensures that the sampling ratio remains constant.

[0067] In this embodiment, the voltage follower circuit 24 operates according to the segmented time. Output follow control signal To drive circuit 23, and by following control signal Control drive voltage It varies with the source voltage of the primary switch.

[0068] The voltage follower circuit 24 includes: a first-stage follower unit 241 and a second-stage follower unit 242. Wherein:

[0069] The first-level follower unit 241 is used for segmented time. Internally based on sampling voltage Voltage tracking is performed during the first time period;

[0070] The second-level follower unit 242 is used for segmented time... After completion, based on the sampled voltage Voltage tracking is performed during the second time period.

[0071] The first-stage follower unit 241 and the second-stage follower unit 242 have the same function, except that they provide voltage following functionality at different stages and output corresponding following control signals. The voltage following the second segment is higher than the voltage following the first segment.

[0072] In this embodiment, the driving circuit 23 includes: a driving logic unit 231, an upper driving transistor N1, and a lower driving transistor N2. The drain of the upper driving transistor N1 is connected to the operating voltage. The source of the lower driving transistor N2 is grounded. The source of the upper driving transistor N1 is connected to the drain of the lower driving transistor N2, outputting a driving voltage to the gate of the primary switching transistor Q1. The drive logic unit 231 generates a logic control signal based on the switch control signal. This logic control signal acts on the upper drive transistor N1 and the lower drive transistor N2, thereby outputting a drive voltage. To the gate of the primary switch Q1.

[0073] When the primary switch Q1 is turned on, the current in the primary switch Q1 is... Flow through the sampling resistor Generate sampling voltage This sampling voltage Entering the voltage follower circuit 24, in segmented time Internally, the voltage follower circuit 24 will raise the gate voltage of the upper driving transistor N1 to... , The gate-source voltage of the upper driving transistor N1; the gate voltage of the primary switching transistor Q1. It will also rise to Therefore, the gate-source voltage of the primary switch Q1 is... Similarly, in segmented time... After the turn-on process, the gate-source voltage of the primary switch Q1 will remain constant at V2, thus the gate-source voltage of the primary switch Q1 remains constant during the turn-on process.

[0074] like Figure 2 As shown, after the primary switch Q1 is turned on, the first-stage follower unit 241 initiates voltage following and clamping within the first time period. Specifically, during the segmented time... During the first time period, the voltage is V1. Simultaneously, the sampling signal processing circuit 21 detects whether the primary transformer is short-circuited. If a short circuit occurs, the detected voltage... Greater than the reference voltage The output control signal CMP_OUT is used to shut down the logic control circuit 22 and enter the protection state. Since the driving voltage is V1 during the first time period, the lower this value, the smaller the saturation current of the primary switch Q1, and the less likely it is to be damaged. Generally, the value of V1 is set slightly higher than the threshold voltage of the primary switch Q1. If in segmented time If no short circuit condition is detected, the voltage follow-up in the second time period will begin. At this time, the follow-up voltage will rise to V2, which is the highest drive voltage. This can quickly turn on the primary switch Q1 and reduce switching losses. The value of V2 can be determined by the characteristics of the primary switch Q1, and is generally 12V.

[0075] It should be noted that the time is divided into segments. The value can be determined based on the switching speed of the primary switch Q1, and is generally taken as the gate drive voltage of the primary switch Q1. From 0 to above its threshold voltage The time. In this embodiment, the time is segmented. The value can be around 300ns.

[0076] Reference Figure 3 , Figure 3 It shows Figure 2 The waveform diagram shown is of the short-circuit protection device for magnetic components in the flyback system protecting the transformer from short circuit.

[0077] Wherein, PWM is the frequency signal generated by the oscillator. The time is divided into segments, namely the first time segment mentioned above. This refers to the gate drive voltage of the primary switch Q1 and the sampling transistor Q2. CMP_OUT is the sampling current of the sampling switch Q2, and CMP_OUT is the output of the sampling signal processing module 21.

[0078] Figure 3 The solid lines in the diagram represent the waveform under normal operating conditions, while the dashed lines represent the waveform under short-circuit conditions of the primary transformer.

[0079] Under normal operating conditions, after the PWM signal is high, the gate-source voltage of the primary switch Q1 is... The current begins to rise, at which point the primary switch Q1 and the sampling transistor Q2 are turned on, and the sampling current... It has begun to rise.

[0080] If in Within a time period, the sampling current Always less than the current threshold Then in After a certain time, the gate-source voltage of the primary switch Q1 Upon entering the second stage following voltage V2, all modules operate normally; among them, the current threshold... It is the drain current that causes the primary switch Q1 to enter the effective conduction state (usually referring to the critical conduction point);

[0081] If in Within a time period, the sampling current greater than the current threshold If CMP_OUT is high, the gate-source voltage of the primary switch Q1 will immediately be reduced. The turn-off value is 0, which can effectively protect the primary switch Q1 from being broken down.

[0082] Reference Figure 4 , Figure 4This is another specific structural schematic diagram of the short-circuit protection device for magnetic components in the flyback system provided in the embodiments of this application.

[0083] and Figure 2 The difference in the illustrated embodiment is that, Figure 4 In the illustrated embodiment, the CS resistor is integrated inside the chip in the flyback system, the source terminal of the primary switch Q1 is grounded, and the gate-source voltage of the primary switch Q1 is... Equal to the source voltage of the upper driving transistor N1 .

[0084] Accordingly, in this embodiment, the voltage follower circuit 24 may include a segmented clamping unit 243.

[0085] The segmentation clamping unit 243 is used to determine the segmentation time. Output follow control signal To drive the voltage output by the drive circuit 23 The voltage is clamped to the first voltage V1 and the second voltage V2 during the first time period and the second time period, respectively.

[0086] In some embodiments, the segmented clamping unit 243 may be implemented by a clamping diode.

[0087] Reference Figure 5 , Figure 5 yes Figure 4 The waveform diagram shown is of the short-circuit protection device for magnetic components in the flyback system protecting the transformer from short circuit.

[0088] Figure 5 The solid lines in the diagram represent the waveform under normal operating conditions, while the dashed lines represent the waveform under short-circuit conditions of the primary transformer.

[0089] Simultaneously refer to Figure 4 and Figure 5 Under normal operating conditions, after the PWM signal goes high, it will be active in segments. Internally, the driving voltage is controlled by the segmented clamping unit 243. The clamp is set to V1. During this period, the sampling signal processing circuit 21 determines the value based on the sampling current. sampling voltage Is it greater than the reference voltage? If the sampling voltage Greater than the reference voltage If the signal is high, it is determined that the system has entered a protection state, and CMP_OUT will be high. The drive voltage will then be immediately reduced. When the voltage is turned off to 0, the primary switch Q1 is effectively protected from breakdown. Otherwise, it enters the second clamping stage, reducing the drive voltage. The clamp is set to V2, which quickly turns on the primary switching transistor Q1.

[0090] like Figure 6 The diagram shown is another specific structural schematic of the short-circuit protection device for magnetic components in the flyback system provided in this application embodiment.

[0091] and Figure 2 The difference in the illustrated embodiment is that, Figure 6 In the embodiment shown, the sampling signal processing circuit 21 includes a current mirror and a comparison unit.

[0092] The current mirror is used to replicate the sampled current proportionally. The replication current is obtained;

[0093] The comparison unit is used to compare the replicated current with the reference current. When the replication current is greater than the reference current When the time is right, output control signal CMP_OUT to logic control circuit 22 to turn off logic control circuit 22.

[0094] In this embodiment, the current mirror is composed of NMOS transistors mn1 and mn2, and the comparator unit is composed of PMOS transistors mp1 and mp2.

[0095] The gate and drain of mn1 are connected to the source of sampling transistor Q2, and the replication current is the same as the reference current. The ratio is m:1, the gate and drain of mp1 are connected to the drain of mn2, and the current ratio of mp1 to mp2 is n:1. This allows the sampling current of sampling transistor Q2 to be converted into... and with reference current Comparison. If If the condition is met, it is determined that the protection has been triggered, and the output control signal CMP_OUT will be high.

[0096] This method allows the source voltage of sampling transistor Q2 to be the threshold voltage of transistor mn1, which is approximately 0.7V. This keeps the gate-source voltage difference between primary switch transistor Q1 and sampling transistor Q2 within the threshold voltage of mn1, thereby reducing the sampling ratio variation caused by the voltage difference between the gate-source voltages of primary switch transistor Q1 and sampling transistor Q2.

[0097] Figure 6 The structure of the sampling signal processing circuit 21 in the illustrated embodiment can also be applied to systems where the CS resistor is integrated inside the chip to reduce the variation in the sampling ratio between the primary switch Q1 and the sampling transistor Q2.

[0098] The short-circuit protection device for magnetic components in the flyback system provided in this application embodiment can reduce the saturation current during a short circuit, effectively protecting the MOSFET from breakdown. In systems with an external CS resistor, it can also protect the CS pin from breakdown. Furthermore, the solution in this application can effectively control the sampling ratio to remain constant, thereby making the detection threshold during a short circuit more accurate and reducing the likelihood of false triggering.

[0099] The proposed solution is applicable to all flyback systems with external CS resistors and flyback systems with integrated CS resistors, making it widely applicable; moreover, the protection threshold is not affected by external parameters, resulting in high reliability.

[0100] Accordingly, this application also provides a flyback converter system, including a short-circuit protection device for magnetic components in the flyback system described above.

[0101] In the description of the embodiments of this application, unless otherwise expressly specified and limited, ordinal numbers, such as "first" and "second," are used only to distinguish and describe related objects, and should not be construed as indicating or implying the relative importance or order between related objects. Furthermore, ordinal numbers do not represent the number of related objects.

[0102] In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Other quantifiers are similar.

[0103] The terms "or" and "and / or" used in this application are used to describe the relationship between related objects, indicating a non-exclusive inclusion. For example, "A and / or B" can include: "A alone", "B alone", or "A with B". Additionally, the character " / " in this document indicates that the preceding and following related objects are in an "or" relationship.

[0104] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of modules is merely a logical functional division, and there may be other division methods in actual implementation, which this application does not limit.

[0105] In the embodiments of this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are 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. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0106] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or they can be separate physical units, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware and software functional units.

[0107] Integrated units implemented as hardware and software functional units can be implemented by a processor calling software; for example, the system includes a processor connected to memory, which stores instructions. The processor calls the instructions stored in memory to implement any of the above methods or to implement the functions of each module of the system. The processor is, for example, a general-purpose processor, such as a CPU or microprocessor, and the memory is either internal or external to the system. The software described above can be stored in a computer-readable storage medium.

[0108] Although embodiments of this application have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting this application. Any person skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments without departing from the spirit and scope of this application.

Claims

1. A short-circuit protection device for magnetic components in a flyback system, the flyback system comprising: An oscillator, a primary switching transistor, and a transformer; characterized in that the device includes: a current sampling module and a detection and protection module; the detection and protection module includes: a sampling signal processing circuit, a logic control circuit, a drive circuit, and a voltage follower circuit; The current sampling module includes a sampling tube coupled to the primary side of the transformer and the primary switching transistor, used to sample the primary side current of the transformer to obtain the sampled current; The sampling signal processing circuit is used to output a control signal to the logic control circuit according to the magnitude of the sampling current, so as to control the logic control circuit to turn on or off. The logic control circuit is used to input the PWM signal generated by the oscillator, output a switching control signal to the drive circuit, and output a segmented time to the voltage follower circuit. The voltage follower circuit is used to output a follower control signal to the drive circuit according to the segmented time. The driving circuit is used to generate a gate driving voltage for the primary switch transistor according to the switch control signal, so as to drive the primary switch transistor to turn on or off, and to control the magnitude of the driving voltage through the follower control signal.

2. The short-circuit protection device for magnetic components in a flyback system according to claim 1, characterized in that, The sampling transistor is a MOS transistor, the gate of the MOS transistor is connected to the gate of the primary switching transistor, the drain of the MOS transistor is connected to the primary side of the transformer, and the source of the MOS transistor is connected to the sampling signal processing circuit.

3. The short-circuit protection device for magnetic components in a flyback system according to claim 1, characterized in that, The voltage follower circuit, based on the segmented time, ensures that the gate-source voltage of the primary switch is a first voltage during a first time period and a second voltage during a second time period; the second voltage is greater than the first voltage.

4. The short-circuit protection device for magnetic components in a flyback system according to claim 1, characterized in that, The sampling signal processing circuit includes: A voltage generation unit is used to generate a detection voltage based on the sampled current; A comparator is used to compare the detected voltage with a reference voltage. When the detected voltage is greater than the reference voltage, a control signal is output to the logic control circuit to turn off the logic control circuit.

5. The short-circuit protection device for magnetic components in a flyback system according to claim 1, characterized in that, The sampling signal processing circuit includes: A current mirror is used to replicate the sampled current proportionally to obtain a replicated current. The comparison unit is used to compare the replicated current with the reference current. When the replicated current is greater than the reference current, it outputs a control signal to the logic control circuit to turn off the logic control circuit.

6. The short-circuit protection device for magnetic components in a flyback system according to claim 3, characterized in that, The current sampling circuit also includes a sampling resistor connected between the source of the primary switching transistor and ground, used to generate a sampling voltage; The voltage follower circuit includes: a first-stage follower unit and a second-stage follower unit; The first-stage following unit is used to perform voltage following within the first time period based on the sampled voltage during the segmented time period; The second-stage following unit is used to perform voltage following within the second time period based on the sampled voltage after the segmented time ends.

7. The short-circuit protection device for magnetic components in a flyback system according to claim 3, characterized in that, The source of the primary switching transistor is grounded; The voltage follower circuit includes: a segmented clamping unit; The segmented clamping unit is used to output a follow control signal according to the segmented time, so as to clamp the driving voltage output by the driving circuit to the first voltage and the second voltage respectively during the first time period and the second time period.

8. The short-circuit protection device for magnetic components in a flyback system according to claim 1, characterized in that, The time intervals are determined based on the switching speed of the primary switching transistor.

9. The short-circuit protection device for magnetic components in a flyback system according to claim 8, characterized in that, The segmented time is the time it takes for the gate voltage of the primary switch to rise from 0 to its threshold voltage.

10. The short-circuit protection device for magnetic components in a flyback system according to any one of claims 1 to 9, characterized in that, The driving circuit includes: a driving logic unit, an upper driving transistor, and a lower driving transistor.

11. A flyback converter system, characterized in that, Includes a short-circuit protection device for magnetic components in a flyback system as described in any one of claims 1 to 10.

12. A chip, characterized in that, include: Sampling signal processing circuit, logic control circuit, driving circuit, and voltage follower circuit; The sampling signal processing circuit is used to output a control signal to the logic control circuit according to the magnitude of the sampling current, so as to control the logic control circuit to turn on or off; the sampling current is obtained by sampling the primary current of the transformer in the flyback system. The logic control circuit is used to input PWM signals, output switching control signals to the drive circuit, and output segmented time signals to the voltage follower circuit. The voltage follower circuit is used to output a follower control signal to the drive circuit according to the segmented time. The driving circuit is used to generate a gate driving voltage for the primary switch in the flyback system according to the switch control signal, so as to drive the primary switch to turn on or off, and to control the magnitude of the driving voltage through the follower control signal.

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