A short-circuit protection control method, a primary side control device, a secondary side feedback device and a switching power supply

Abstract

The application discloses a short-circuit protection control method, a primary side control device, a secondary side feedback device and a switching power supply. The short-circuit protection control method comprises the following steps: an output voltage rectification detection step; a comparison output step; a modulation step; an isolation processing step; a demodulation step; and an output short-circuit detection and protection execution step. Whether the switching power supply output is short-circuited is determined according to a feedback control signal, and the primary side drive is immediately turned off when the short circuit is identified. After a third set time, soft start is performed again. The conditions for determining the output short circuit in different working stages are as follows: in the soft start stage, the feedback control signal is equal to 1 for the first time but the duration is less than or equal to the first set time; or the time when the feedback control signal FB is continuously equal to 0 is greater than the second set time; and in the stable working stage, the time when the feedback control signal FB is continuously equal to 0 is greater than the second set time. The application can improve the reliability of the switching power supply.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power supply, and particularly relates to a short-circuit protection control method, a primary side control device, a secondary side feedback device and a switching power supply. BACKGROUND

[0002] In the current rapid development of electronic technology, the performance of DC-DC switching power supply as the cornerstone of energy conversion is directly related to the efficiency and stability of electronic equipment. Especially in the face of short circuit, how to realize efficient and accurate short circuit protection has become a key factor restricting the progress of electronic technology. Traditional short circuit protection methods are mostly based on single component monitoring or simple current threshold determination, which often cannot balance the protection speed, accuracy and recovery ability, limiting the overall efficiency and reliability of the switching power supply system. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to provide a short-circuit protection control method, a primary side control device, a secondary side feedback device and a switching power supply, which at least solves one of the technical problems existing in the prior art to some extent.

[0004] The present application aims to realize real-time monitoring of the working state of the switching power supply through a highly integrated digital logic determination scheme, accurately identify the output short circuit fault, and execute the corresponding protection action according to the preset logic algorithm, to ensure the reliability and efficiency of the switching power supply.

[0005] As a first aspect of the present application, the technical scheme of the provided short-circuit protection control method embodiment is as follows:

[0006] A short-circuit protection control method applied to a switching power supply, wherein the switching power supply comprises a transformer, and the short-circuit protection control method comprises:

[0007] An output voltage rectification detection step for converting an alternating current signal output from the secondary side of the transformer into a direct current voltage, and obtaining a first voltage signal VDIV representing the magnitude of the direct current voltage;

[0008] A comparison output step for comparing the first voltage signal with a reference voltage and outputting a PWM signal;

[0009] A modulation step for modulating the PWM signal into a first modulation signal ISOP and a second modulation signal ISON;

[0010] An isolation processing step for isolating the first modulation signal ISOP into a first isolated signal VIOP and isolating the second modulation signal ISON into a second isolated signal VION;

[0011] demodulating the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, the feedback control signal FB being a narrow pulse signal;

[0012] output short circuit detection and protection performing step, determining whether the output of the switching power supply is short circuited according to the feedback control signal FB, and immediately shutting down the primary side drive when the output of the switching power supply is identified to be short circuited, and re-performing soft start after a third set time, the condition for determining that the output of the switching power supply is short circuited in different working stages being as follows:

[0013] soft start stage, if the feedback control signal FB is identified to be equal to 1 for the first time but the duration is less than or equal to a first set time, or the feedback control signal FB is identified to be continuously equal to 0 for a time greater than a second set time, it is determined that the output of the switching power supply is short circuited;

[0014] stable working stage, if the feedback control signal FB is identified to be continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short circuited.

[0015] Preferably, the modulating step modulates the PWM signal into the first modulated signal ISOP and the second modulated signal ISON by an OOK modulation method.

[0016] Further, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent out.

[0017] Further, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, whether the output of the switching power supply is short circuited is not identified.

[0018] Further, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent out, and whether the output of the switching power supply is short circuited is not identified.

[0019] As a second aspect of the present application, the provided primary side control device embodiment technical solutions are as follows:

[0020] A primary side control device applied to a switching power supply, the switching power supply including a transformer, wherein the primary side control device includes:

[0021] a demodulating unit configured to receive the first isolated signal VIOP and the second isolated signal VION transmitted by the isolation processing unit, and demodulate the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, the feedback control signal FB being a narrow pulse signal;

[0022] The output short circuit detection and protection execution unit is configured to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and to immediately turn off the primary side drive when it is identified that the output of the switching power supply is short-circuited, and to restart soft start after a third set time. The conditions for determining that the output of the switching power supply is short-circuited in different working stages are as follows:

[0023] In the soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to the first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short-circuited.

[0024] In the stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short-circuited.

[0025] The first isolation signal VIOP is generated by the first modulation signal ISOP generated by the secondary side feedback device and the isolation processing device; and the second isolation signal VION is generated by the second modulation signal ISON generated by the secondary side feedback device and the isolation processing device.

[0026] The secondary side feedback device generates the first modulation signal ISOP and the second modulation signal ISON through the following units:

[0027] The output voltage rectification detection unit converts the alternating current signal output by the transformer secondary side into a direct current voltage, and obtains a first voltage signal VDIV representing the size of the direct current voltage.

[0028] The comparison output unit compares the first voltage signal with a reference voltage and outputs a PWM signal.

[0029] The modulation unit modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON.

[0030] Further, the output short circuit detection and protection execution unit comprises a counter, a control circuit and a soft start circuit; an input terminal CLK1 of the counter is configured to input a clock signal, a first output terminal CLK_DET_HW of the counter is connected to a first input terminal of the control circuit, a second output terminal CLK_SCP1 of the counter is connected to a second input terminal of the control circuit, a third output terminal CLK_DET_0 of the counter is connected to a third input terminal of the control circuit, a fourth output terminal CLK_SCP2 of the counter is connected to a fourth input terminal of the control circuit; a fifth input terminal of the control circuit is configured to input the feedback control signal FB, a first output terminal SOFT_EN of the control circuit is connected to a first input terminal of the soft start circuit, a second output terminal SECOND_EN of the control circuit is connected to a second input terminal of the pseudo-random circuit; and a SYS_OUT terminal of the soft start circuit outputs an initial driving signal.

[0031] The counter takes the input clock signal as an initial frequency to time the first set time, the second set time and the third set time.

[0032] The control circuit is configured to detect the first set time, the second set time, the third set time and an enable signal generated by the feedback control signal FB.

[0033] The soft start circuit is configured to generate the initial driving signal under the action of the enable signal.

[0034] Further, the output short circuit detection and protection execution unit further comprises a pseudo-random circuit, which is configured to convert the initial driving signal with a fixed frequency into a variable frequency driving signal based on a pseudo-random number, so as to reduce EMI and improve power supply performance.

[0035] As a third aspect of the present application, the provided secondary side feedback device embodiment technical solutions are as follows:

[0036] A secondary side feedback device applied to a switching power supply, wherein the switching power supply comprises a transformer, and the secondary side feedback device comprises:

[0037] An output voltage rectification detection unit configured to convert an alternating current signal output by the transformer secondary side into a direct current voltage, and obtain a first voltage signal VDIV representing the size of the direct current voltage;

[0038] A comparison output unit configured to compare the first voltage signal with a reference voltage and output a PWM signal;

[0039] A modulation unit configured to modulate the PWM signal into a first modulation signal ISOP and a second modulation signal ISON;

[0040] The first modulation signal ISOP is isolated by the isolation processing device into a first isolated signal VIOP, and the second modulation signal ISON is isolated by the isolation processing device into a second isolated signal VION.

[0041] A demodulation unit is configured to demodulate the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal.

[0042] An output short-circuit detection and protection execution unit is configured to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and to immediately turn off the primary side drive when the output of the switching power supply is identified as short-circuited, and to restart soft start after a third set time.

[0043] In the soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to a first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than a second set time, the output of the switching power supply is determined to be short-circuited.

[0044] In the stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, the output of the switching power supply is determined to be short-circuited.

[0045] As a fourth aspect of the present application, the switching power supply embodiment is provided as follows:

[0046] The switching power supply comprises a transformer, wherein the switching power supply further comprises the primary side control device of any one of the second aspect, the isolation processing device, and the secondary side feedback device of any one of the third aspect.

[0047] Compared with the prior art, the present application can ensure that the switching power supply can quickly and effectively identify whether the system triggers the short-circuit protection mechanism during the power-on soft start stage and the closed-loop control stage, thereby accurately and effectively protecting the system stable and safe and reliable.

[0048] 1. In the soft start stage: the feedback control signal FB=0 in the initial stage of power-on, the primary side circuit of the switching power supply starts soft start, so that the secondary side output voltage slowly rises, avoiding the output voltage overshoot caused by too large start-up stress; if the secondary side output voltage does not reach the rated output voltage within the specified time, at this time, if the first appearing feedback control signal FB is equal to 1 but the duration is less than or equal to the first set time; or the time of the feedback control signal FB continuously equal to 0 is greater than the second set time, the primary side drive is immediately turned off in response, the switching power supply enters the protection time waiting, and then restarts soft start, effectively avoiding the damage of the switching power supply caused by output short circuit in the start-up stage.

[0049] 2. In the stable working stage: the secondary side output voltage is maintained around the rated voltage through different states of the feedback control signal FB, and at the same time, the time of FB=0 is detected, once the time of FB=0 is greater than the short circuit protection set value, the primary side drive is immediately turned off in response, the switching power supply enters the protection time waiting, and then restarts soft start, effectively avoiding the damage of the switching power supply caused by output short circuit in the stable working stage.

[0050] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The flow chart of the circuit protection control method of the first embodiment of the present application applied to the switching power supply;

[0052] Figure 2 The specific embodiment principle block diagram of the primary side control device of the second embodiment of the present application applied to the switching power supply;

[0053] Figure 3 The specific principle block diagram of the output short circuit detection and protection execution unit of the second embodiment of the present application; Figure 2

[0054] Figure 4 The control timing diagram of the switching power supply; Figure 2

[0055] Figure 5 The control timing diagram of the switching power supply when the outputs are applied in parallel. DETAILED DESCRIPTION

[0056] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0057] ​​In the following, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the drawings in the embodiments of the present application, so that those skilled in the art can better understand the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0058] It should be noted that the terms "first", "second", and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so as to describe the embodiments of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0059] It should be understood that, in the description, claims and drawings of the present application, when describing a step succeeding to another step, the step can directly succeed to the other step, or succeed to the other step through a third step; when describing an element / unit "succeeding" to another element / unit, the element / unit can be "directly connected" to the other element / unit, or "connected" to the other element / unit through a third element / unit.

[0060] In addition, the drawings of the present disclosure are only schematic and not necessarily to scale. The same reference numerals in the drawings represent the same or similar parts, and thus repeated description thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities, which do not necessarily have to correspond to physically or logically independent entities. These functional entities can be implemented by software, or in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0061] First embodiment

[0062] The embodiment provided is a short-circuit protection control method applied to a switching power supply, the switching power supply comprising a transformer, wherein the short-circuit protection control method comprises:

[0063] An output voltage rectification detection step converts an alternating current signal output by the secondary side of the transformer into a direct current voltage, and obtains a first voltage signal VDIV representing the size of the direct current voltage;

[0064] comparing the first voltage signal with the reference voltage to output a PWM signal;

[0065] modulating the PWM signal into a first modulated signal ISOP and a second modulated signal ISON;

[0066] isolating the first modulated signal ISOP into a first isolated signal VIOP and isolating the second modulated signal ISON into a second isolated signal VION;

[0067] demodulating the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, the feedback control signal FB being a narrow pulse signal;

[0068] outputting a short-circuit detection and protection execution step, determining whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately shutting down the primary side drive when the output of the switching power supply is identified to be short-circuited, and after a third set time, re-performing soft start, the conditions for determining the output of the switching power supply to be short-circuited in different working stages are as follows:

[0069] in the soft start stage, if the feedback control signal FB is identified to be equal to 1 for the first time but the duration is less than or equal to a first set time, or the feedback control signal FB is identified to be continuously equal to 0 for a time greater than a second set time, the output of the switching power supply is determined to be short-circuited;

[0070] in the stable working stage, if the feedback control signal FB is identified to be continuously equal to 0 for a time greater than the second set time, the output of the switching power supply is determined to be short-circuited.

[0071] Figure 1 for the flow chart of the circuit protection control method of the first embodiment of the present application applied to the switching power supply, please refer to Figure 1 , wherein:

[0072] the output voltage sampling signal of the switching power supply (i.e. the first voltage signal representing the DC voltage) is denoted as VDIV, and the reference voltage of the feedback loop of the switching power supply is denoted as VREF;

[0073] the primary side soft start stage is a stage in which VDIV climbs from 0 to VREF, in this stage, since VDIV < VREF, the feedback control signal FB is always equal to 0, when VDIV = VREF, the feedback control signal FB will be equal to 1 for the first time, if the feedback control signal FB is identified to be equal to 1 for the first time and the duration is greater than a set time, the primary side soft start stage is ended and the stable working stage is entered, otherwise, the output of the switching power supply is determined to be short-circuited, the primary side drive is immediately shut down, and after a third set time, soft start is re-performed;

[0074] In the stable working phase, the output end of the switching power supply controlled by the feedback control signal FB is stabilized in the set range, VDIV fluctuates up and down around VREF, so that the feedback control signal FB changes between 0 and 1, but the time when the feedback control signal FB is continuously equal to 0 should be controlled within a certain range, if it is detected that the time when the feedback control signal is continuously equal to 0 is greater than the second set time, it is determined that the output of the switching power supply is short-circuited, and the primary side drive is immediately turned off, and after the third set time, the soft start is restarted.

[0075] Compared with the prior art, the control method of the embodiment can monitor the working state of the switching power supply in real time and accurately identify the output short-circuit fault, because the preset logical algorithm is added to perform the corresponding protection action.

[0076] As a specific embodiment of the embodiment, the modulation step modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON by the OOK modulation method.

[0077] As a specific embodiment of the embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent, so that the reference voltage VREF of the feedback loop of the switching power supply of the secondary side is inconsistent due to process deviation, so that one is in the primary side soft start phase and the other is in the stable working phase, and the output voltage overshoot risk caused thereby is avoided.

[0078] As a specific embodiment of the embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, whether the switching power supply appears the output short-circuit is not identified, so that the output voltage overshoot risk is avoided.

[0079] As a specific embodiment of the embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent, and whether the switching power supply appears the output short-circuit is not identified.

[0080] Second embodiment

[0081] The embodiment provided is a primary side control device applied to a switching power supply, the switching power supply including a transformer, Figure 2 As a specific embodiment principle diagram of the primary side control device applied to the switching power supply of the second embodiment of the application, wherein the primary side control device includes:

[0082] The demodulation unit is configured to receive the first isolation signal VIOP and the second isolation signal VION transmitted by the isolation processing unit, and demodulate the first isolation signal VIOP and the second isolation signal VION into the feedback control signal FB, the feedback control signal FB being a narrow pulse signal.

[0083] The output short circuit detection and protection execution unit is configured to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and to immediately turn off the primary side drive when the output of the switching power supply is identified to be short-circuited, and to re-perform soft start after a third set time.

[0084] In the soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to the first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, the output of the switching power supply is determined to be short-circuited.

[0085] In the stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, the output of the switching power supply is determined to be short-circuited.

[0086] The first isolation signal VIOP is generated by the first modulation signal ISOP generated by the secondary side feedback device and processed by the isolation processing device, and the second isolation signal VION is generated by the second modulation signal ISON generated by the secondary side feedback device and processed by the isolation processing device.

[0087] The secondary side feedback device generates the first modulation signal ISOP and the second modulation signal ISON through the following units:

[0088] The output voltage rectification detection unit converts the alternating current signal output by the transformer secondary side into a direct current voltage, and obtains the first voltage signal VDIV representing the size of the direct current voltage.

[0089] The comparison output unit compares the first voltage signal with the reference voltage and outputs the PWM signal.

[0090] The modulation unit modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON.

[0091] The technical means adopted by the control device of the embodiment corresponds to the control method of the first embodiment, has the same beneficial effects, and thus will not be described in detail.

[0092] In addition, the preferred technical means or further improved means of each step in the control method of the first embodiment can be extended to the corresponding units of the embodiment, and the embodiment will not be described one by one.

[0093] Figure 3 For Figure 2 A specific principle diagram of the output short circuit detection and protection execution unit is shown in Figure 3The output short-circuit detection and protection execution unit comprises a counter, a control circuit and a soft start circuit; an input end CLK1 of the counter is configured to input a clock signal, a first output end CLK_DET_HW of the counter is connected to a first input end of the control circuit, a second output end CLK_SCP1 of the counter is connected to a second input end of the control circuit, a third output end CLK_DET_0 of the counter is connected to a third input end of the control circuit, a fourth output end CLK_SCP2 of the counter is connected to a fourth input end of the control circuit, a fifth input end of the control circuit is configured to input a feedback control signal FB, a first output end SOFT_EN of the control circuit is connected to a first input end of the soft start circuit, and a second output end SECOND_EN of the control circuit is connected to a second input end of the pseudo-random circuit; and a SYS_OUT end of the soft start circuit outputs an initial driving signal.

[0094] The counter takes the input clock signal as an initial frequency, and is configured to time the first set time, the second set time and the third set time.

[0095] The control circuit is configured to detect the feedback control signal FB to generate the first set time, the second set time, the third set time and an enable signal.

[0096] The soft start circuit is configured to generate the initial driving signal under the action of the enable signal.

[0097] Further, the output short-circuit detection and protection execution unit further comprises a pseudo-random circuit, which is configured to convert the initial driving signal of a fixed frequency into a variable frequency driving signal based on a pseudo-random number, so as to reduce EMI and improve power supply performance.

[0098] Third embodiment

[0099] The embodiment provides a secondary side feedback device, which is applied to a switching power supply, and the switching power supply comprises a transformer.

[0100] The output voltage rectification detection unit is configured to convert an alternating current signal output by the secondary side of the transformer into a direct current voltage, and obtain a first voltage signal VDIV representing the size of the direct current voltage.

[0101] The comparison output unit is configured to compare the first voltage signal with a reference voltage, and output a PWM signal.

[0102] The modulation unit is configured to modulate the PWM signal into a first modulation signal ISOP and a second modulation signal ISON.

[0103] Wherein: the first modulation signal ISOP is isolated by the isolation processing device to the first isolated signal VIOP, the second modulation signal ISON is isolated by the isolation processing device to the second isolated signal VION, and the primary side control device controls short circuit protection through the following units according to the first isolated signal VIOP and the second isolated signal VION:

[0104] The demodulation unit is used for demodulating the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, and the feedback control signal FB is a narrow pulse signal.

[0105] The output short circuit detection and protection execution unit is used for determining whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately closing the primary side drive when the output of the switching power supply is identified to be short-circuited, and re-performing soft start after a third set time. The conditions for determining that the output of the switching power supply is short-circuited in different working stages are as follows:

[0106] In the soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to the first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short-circuited.

[0107] In the stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short-circuited.

[0108] The technical means adopted by the control device of the embodiment corresponds to the control method of the first embodiment, has the same beneficial effects, and thus is not described in detail.

[0109] In addition, the preferred technical means or further improved means of each step in the control method of the first embodiment can be extended to the corresponding units of the embodiment, and the embodiment will not be described one by one.

[0110] Fifth embodiment

[0111] The embodiment provides a switching power supply, which comprises a transformer, wherein: the switching power supply further comprises the primary side control device in any one of the second embodiment, the isolation processing device, and the secondary side feedback device in any one of the third embodiment.

[0112] Figure 4 For Figure 2 The control timing diagram of the switching power supply, in combination with Figure 4 To Figure 2 The working process of the switching power supply is analyzed as follows:

[0113] (1) In the soft start control process, at the beginning, the primary side soft start is started, the secondary side output voltage VISO gradually rises, VDIV < VREF, PWM = 0, the primary side feedback control signal FB = 0, the primary side keeps the soft start unchanged, and as the primary side soft start output signal duty cycle gradually increases, two situations can occur:

[0114] Situation one, the secondary side output voltage VISO voltage division (i.e. the first voltage signal representing the DC voltage size) VDIV > VREF, then PWM = 1, the feedback control signal FB = 1: if the first feedback control signal FB = 1 is identified but the duration is less than or equal to the first set time, it is determined that the switching power supply output is short-circuited, the primary side soft start is immediately turned off, and the short-circuit protection waiting time is entered, after the waiting time ends, the system is restarted; when the first feedback control signal FB = 1 is detected and the duration is greater than the first set time, the primary side soft start is ended, and the feedback control signal FB closed-loop control is started;

[0115] Situation two, the secondary side output voltage VISO voltage division VDIV < VREF, then FB = 0, the feedback control signal FB is detected to be continuously equal to 0 for a time greater than the second set time, and the switching power supply output is also determined to be short-circuited, the primary side soft start is immediately turned off, and the short-circuit protection waiting time is entered, after the waiting time ends, the system is restarted;

[0116] (2) In the closed-loop control process, when VDIV > VREF, PWM = 1, the primary side feedback control signal FB = 1, the primary side is not driven, and the secondary side output voltage VISO decreases; when VDIV < VREF, PWM = 0, the primary side feedback control signal FB = 0, the primary side is driven, and the secondary side output voltage VISO rises, if the secondary side output is short-circuited, VISO gradually decreases, VDIV < VREF, PWM = 0, the primary side feedback control signal FB = 0, and when the time that FB = 0 is detected is greater than the second set time, it is determined that the switching power supply enters the short-circuit state, the system immediately turns off the primary side drive, enters the short-circuit protection waiting time, and after the time ends, the soft start is restarted.

[0117] Figure 5is a control timing diagram when the switching power output is in parallel application, as shown in the figure, VREF1 is the reference voltage of the switching power feedback loop of the secondary side of chip 1 in the first branch, VREF2 is the reference voltage of the switching power feedback loop of the secondary side of chip 2 in the second branch, in the soft start process, the secondary side output voltage gradually rises, assuming VREF1 < VREF2, chip 1 enters the steady state working stage first, and chip 2 is in the soft start stage, at this time, since VDIV < VREF2, the feedback control signal FB2 of chip 2 = 0, the primary side is driven, and the secondary side output voltage will continue to rise, VDIV > VREF1, the feedback control signal FB1 of chip 1 = 1, the primary side is not driven, so the output voltage overshoot of parallel output application can be avoided, until chip 2 enters the steady state working stage, the system output voltage can be stabilized near the rated voltage.

[0118] The above is only the preferred embodiment of the present application, it should be pointed out that the above preferred embodiment should not be considered as a limitation of the present application, the protection scope of the present application should be limited by the scope defined by the claims. For ordinary skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A short-circuit protection control method applied to a switching power supply, the switching power supply comprising a transformer, characterized in that, The short-circuit protection control method comprises: An output voltage rectification detection step, which converts an alternating current signal output by the transformer secondary side into a direct current voltage, and acquires a first voltage signal VDIV representing the size of the direct current voltage; A comparison output step, which compares the first voltage signal with a reference voltage and outputs a PWM signal; A modulation step, which modulates the PWM signal into a first modulation signal ISOP and a second modulation signal ISON; An isolation processing step, which isolates the first modulation signal ISOP into a first isolated signal VIOP and isolates the second modulation signal ISON into a second isolated signal VION; A demodulation step, which demodulates the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, which is a narrow pulse signal; An output short-circuit detection and protection execution step, which determines whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately turns off the primary side drive when it is identified that the output of the switching power supply is short-circuited, and re-performs soft start after a third set time. The conditions for determining the output short-circuit of the switching power supply in different working stages are as follows: In the soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to a first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than a second set time, it is determined that the output of the switching power supply is short-circuited. In the stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short-circuited.

2. The short-circuit protection control method according to claim 1, characterized by: The modulation step modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON by an OOK modulation method.

3. The short-circuit protection control method of claim 1, wherein: If the switching power supply comprises two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent out.

4. The short-circuit protection control method of claim 1, wherein: If the switching power supply comprises two parallel outputs, when the feedback control signal FB is equal to 1, whether the switching power supply has an output short-circuit is not identified.

5. The short-circuit protection control method of claim 1, wherein: If the switching power supply comprises two parallel outputs, when the feedback control signal FB is equal to 1, the primary side drive is not sent out, and whether the switching power supply has an output short-circuit is not identified.

6. A primary side control device applied to a switching power supply, the switching power supply comprising a transformer, characterized in that, The primary side control device comprises: A demodulation unit, which receives the first isolated signal VIOP and the second isolated signal VION transmitted by the isolation processing unit, demodulates the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, which is a narrow pulse signal; An output short-circuit detection and protection execution unit, which determines whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately turns off the primary side drive when it is identified that the output of the switching power supply is short-circuited, and re-performs soft start after a third set time. The conditions for determining the output short-circuit of the switching power supply in different working stages are as follows: In the soft start stage, if it is identified that the first appearing feedback control signal FB is equal to 1 but the duration is less than or equal to the first set time, or it is identified that the time of the feedback control signal FB continuously equal to 0 is greater than the second set time, it is determined that the switching power supply output is short-circuited; In the stable working stage, if it is identified that the time of the feedback control signal FB continuously equal to 0 is greater than the second set time, it is determined that the switching power supply output is short-circuited; The first isolation signal VIOP is generated by the first modulation signal ISOP generated by the secondary side feedback device and generated by the isolation processing device; the second isolation signal VION is generated by the second modulation signal ISON generated by the secondary side feedback device and generated by the isolation processing device; The secondary side feedback device generates the first modulation signal ISOP and the second modulation signal ISON through the following units: The output voltage rectification detection unit converts the alternating current signal output by the transformer secondary side into a direct current voltage, and obtains a first voltage signal VDIV representing the size of the direct current voltage; The comparison output unit compares the first voltage signal with a reference voltage and outputs a PWM signal; The modulation unit modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON.

7. The primary side control device of claim 6, wherein: The output short-circuit detection and protection execution unit includes a counter, a control circuit and a soft start circuit; the input end CLK1 of the counter is used for inputting a clock signal, the first output end CLK_DET_HW of the counter is connected to the first input end of the control circuit, the second output end CLK_SCP1 of the counter is connected to the second input end of the control circuit, the third output end CLK_DET_0 of the counter is connected to the third input end of the control circuit, the fourth output end CLK_SCP2 of the counter is connected to the fourth input end of the control circuit; the fifth input end of the control circuit is used for inputting the feedback control signal FB, the first output end SOFT_EN of the control circuit is connected to the first input end of the soft start circuit; the SYS_OUT end of the soft start circuit outputs an initial driving signal; The counter takes the input clock signal as an initial frequency, and is used for timing the first set time, the second set time and the third set time; The control circuit is used for detecting the feedback control signal FB to generate the first set time, the second set time, the third set time and an enable signal; The soft start circuit is used for generating the initial driving signal under the action of the enable signal.

8. The primary side control device of claim 7, wherein: The output short-circuit detection and protection execution unit further includes a pseudo-random circuit, which is used for converting the initial driving signal with a fixed frequency into a variable frequency driving signal based on a pseudo-random number, so as to reduce EMI and improve the performance of the power supply.

9. A secondary side feedback device applied to a switching power supply, the switching power supply comprising a transformer, characterized in that, The secondary side feedback device includes: The output voltage rectification detection unit converts the alternating current signal output by the transformer secondary side into a direct current voltage, and obtains a first voltage signal VDIV representing the size of the direct current voltage; The comparison output unit compares the first voltage signal with a reference voltage and outputs a PWM signal; The modulation unit modulates the PWM signal into the first modulation signal ISOP and the second modulation signal ISON. a modulation unit, configured to modulate the PWM signal into a first modulation signal ISOP and a second modulation signal ISON; wherein: the first modulation signal ISOP is isolated by an isolation processing device into a first isolated signal VIOP, the second modulation signal ISON is isolated by the isolation processing device into a second isolated signal VION, and a primary side control device performs short circuit protection control according to the first isolated signal VIOP and the second isolated signal VION through the following units: a demodulation unit, configured to demodulate the first isolated signal VIOP and the second isolated signal VION into a feedback control signal FB, the feedback control signal FB being a narrow pulse signal; an output short circuit detection and protection execution unit, configured to determine whether the output of the switching power supply is short circuited according to the feedback control signal FB, and to immediately turn off the primary side drive when it is identified that the output of the switching power supply is short circuited, and to restart soft start after a third set time, the conditions for determining that the output of the switching power supply is short circuited in different working stages being as follows: in a soft start stage, if it is identified that the feedback control signal FB is equal to 1 for the first time but the duration is less than or equal to a first set time, or it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than a second set time, it is determined that the output of the switching power supply is short circuited; in a stable working stage, if it is identified that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, it is determined that the output of the switching power supply is short circuited.

10. A switched mode power supply comprising a transformer, characterised by: The switching power supply further comprises the primary side control device of any one of claims 6 to 8 and the secondary side feedback device of claim 9.

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