Short circuit protection control method, primary side control device, secondary side feedback device and switching power supply

Abstract

The invention 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: determining whether the output of the switching power supply is short-circuited according to the feedback control signal, immediately closing the primary drive when the short circuit is identified, and performing soft start again after a third set time, the feedback control signal appearing for the first time is recognized to be equal to 1, and the duration time is smaller than or equal to first set time; or identifying that 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, identifying that the time when the feedback control signal FB is continuously equal to 0 is greater than the second set time. The reliability of the switching power supply can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supply, and in particular relates to a short circuit protection control method, a primary side control device, a secondary side feedback device and a switching power supply. Background Art

[0002] In the tide of rapid development of contemporary electronic technology, DC-DC switching power supply, as the cornerstone of energy conversion, has a performance that is directly related to the efficiency and stability of electronic equipment. Especially in the face of the severe challenge of short circuit, how to achieve 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 makes it difficult to strike a balance between protection speed, accuracy and recovery ability, limiting the overall performance and reliability of the switching power supply system. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention 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 solve one of the technical problems existing in the prior art to a certain extent.

[0004] The present invention aims to monitor the working status of the switching power supply in real time through a highly integrated digital logic judgment scheme, accurately identify output short-circuit faults, and perform corresponding protection actions according to a preset logic algorithm to ensure the reliability and efficiency of the switching power supply.

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

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

[0007] An output voltage rectification detection step, converting the AC signal output by the secondary side of the transformer into a DC voltage, and obtaining a first voltage signal VDIV representing the magnitude of the DC voltage;

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

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

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

[0011] A demodulation step, demodulating the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal;

[0012] Output 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 re-starting the soft start after the third set time. The conditions for determining whether the output of the switching power supply is short-circuited in different working stages are as follows:

[0013] In the soft start phase, if it is identified that the first occurrence of the 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 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;

[0014] In the stable operation stage, if 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.

[0015] Preferably, the modulation step modulates the PWM signal into a first modulation signal ISOP and a second modulation 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 issued.

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

[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 issued, and it is not identified whether the switching power supply has an output short circuit.

[0019] As a second aspect of the present invention, the technical solution of the primary side control device embodiment provided is as follows:

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

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

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

[0023] In the soft start phase, if it is identified that the first occurrence of the 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 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 time when the feedback control signal FB 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;

[0025] Wherein: the first isolation signal VIOP is generated by the first modulation signal ISOP generated by the secondary feedback device and isolated and processed by the isolation processing device; the second isolation signal VION is generated by the second modulation signal ISON generated by the secondary feedback device and isolated and processed by 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] An output voltage rectification detection unit converts the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtains a first voltage signal VDIV representing the magnitude of the DC voltage;

[0028] A comparison output unit, which 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 includes a counter, a control circuit and a soft start circuit; the input terminal CLK1 of the counter is used to input a clock signal, the first output terminal CLK_DET_HW is connected to the first input terminal of the control circuit, the second output terminal CLK_SCP1 is connected to the second input terminal of the control circuit, the third output terminal CLK_DET_0 is connected to the third input terminal of the control circuit, and the fourth output terminal CLK_SCP2 is connected to the fourth input terminal of the control circuit; the fifth input terminal of the control circuit is used to input the feedback control signal FB, the first output terminal SOFT_EN of the control circuit is connected to the first input terminal of the soft start circuit, and the second output terminal SECOND_EN of the control circuit is connected to the second input terminal of the pseudo-random circuit; the SYS_OUT terminal of the soft start circuit outputs an initial drive signal;

[0031] The counter uses 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 used to detect the feedback control signal FB to generate the first setting time, the second setting time, the third setting time and an enable signal;

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

[0034] Furthermore, the output short circuit detection and protection execution unit also includes a pseudo-random circuit for converting an initial driving signal with a fixed frequency into a variable frequency driving signal based on a pseudo-random number, thereby achieving the purpose of reducing EMI and improving power supply performance.

[0035] As a third aspect of the present invention, a technical solution of an embodiment of a secondary feedback device is provided as follows:

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

[0037] An output voltage rectification detection unit, used for converting the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtaining a first voltage signal VDIV representing the magnitude of the DC voltage;

[0038] A comparison output unit, used for comparing the first voltage signal with a reference voltage and outputting 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] Wherein: the first modulation signal ISOP is isolated and processed by the isolation processing device into a first isolation signal VIOP, and the second modulation signal ISON is isolated and processed by the isolation processing device into a second isolation signal VION, and the primary side control device performs short circuit protection control through the following units according to the first isolation signal VIOP and the second isolation signal VION:

[0041] A demodulation unit, used for demodulating the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal;

[0042] The output short circuit detection and protection execution unit is used to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately shut down the primary side drive when the output of the switching power supply is identified to be short-circuited, and restart the soft start after the third set time. The conditions for determining whether the output of the switching power supply is short-circuited in different working stages are as follows:

[0043] In the soft start phase, if it is identified that the first occurrence of the 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 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;

[0044] In the stable operation stage, if 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.

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

[0046] A switching power supply, comprising a transformer, wherein: the switching power supply further comprises the primary side control device and the isolation processing device as described in any one of the second aspects above, and the secondary side feedback device as described in any one of the third aspects above.

[0047] Compared with the prior art, the present invention can ensure to the greatest extent 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 stability and safety and reliability. The specific beneficial effects are analyzed in detail as follows:

[0048] 1. In the soft start stage: at the initial stage of power-on, the feedback control signal FB=0, the primary circuit of the switching power supply starts soft start, so that the secondary output voltage rises slowly to avoid overshoot of the output voltage caused by excessive startup stress; if the secondary output voltage does not reach the rated output voltage within the specified time, at this time, if it is recognized that the first feedback control signal FB is equal to 1 but the duration is less than or equal to the first set time; or it is recognized that the feedback control signal FB is continuously equal to 0 for more than the second set time, the primary drive is immediately shut down, and the switching power supply enters the protection time waiting, and then restarts soft start, effectively avoiding damage to the switching power supply caused by output short circuit during the startup stage;

[0049] 2. In the stable working stage: the output voltage of the secondary side is maintained stable near the rated voltage through different states of the feedback control signal FB. At the same time, the time when FB=0 is detected. Once the time when FB=0 is greater than the short-circuit protection setting value, the primary side drive is immediately shut down. After the switching power supply takes into account the protection time waiting, it will restart the soft-start, effectively avoiding damage to the switching power supply caused by output short circuit in the stable working stage.

[0050] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A flow chart of a circuit protection control method according to a first embodiment of the present invention applied to a switching power supply;

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

[0053] Figure 3 for Figure 2 A specific principle block diagram of the output short circuit detection and protection execution unit;

[0054] Figure 4 for Figure 2 Control timing diagram of switching power supply;

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

[0056] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0057] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0059] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

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

[0061] First embodiment

[0062] This embodiment provides a short-circuit protection control method, which is applied to a switching power supply, wherein the switching power supply includes a transformer, wherein the short-circuit protection control method includes:

[0063] An output voltage rectification detection step, converting the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtaining a first voltage signal VDIV representing the magnitude of the DC voltage;

[0064] A comparison and output step, comparing the first voltage signal with a reference voltage and outputting a PWM signal;

[0065] A modulation step of modulating the PWM signal into a first modulation signal ISOP and a second modulation signal ISON;

[0066] An isolation processing step of isolating the first modulation signal ISOP into a first isolation signal VIOP and isolating the second modulation signal ISON into a second isolation signal VION;

[0067] A demodulation step, demodulating the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal;

[0068] Output short circuit detection and protection execution steps: determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately turn off the primary side drive when the output of the switching power supply is identified as short-circuited. After the third set time, soft start is restarted. The conditions for determining the output short circuit of the switching power supply in different working stages are as follows:

[0069] In the soft start phase, if it is identified that the first occurrence of the 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 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;

[0070] In the stable operation stage, if 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.

[0071] Figure 1 This is a flow chart of the circuit protection control method of the first embodiment of the present invention applied to a switching power supply. Figure 1 ,in:

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

[0073] The primary side soft start phase is the phase where VDIV starts to climb from 0 to VREF. In this phase, 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 it is recognized that the first feedback control signal FB is equal to 1 and the duration is greater than the set time, the primary side soft start phase is terminated and the stable working phase is entered. Otherwise, it is determined that the output of the switching power supply is short-circuited, and the primary side drive is immediately turned off. After the third set time, the soft start is restarted.

[0074] In the stable working stage, the output end of the switching power supply controlled by the feedback control signal FB is stabilized within the set range, and VDIV fluctuates around VREF, so that the feedback control signal FB will change back and forth 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. After the third set time, soft start is restarted.

[0075] Compared with the prior art, the control method of this embodiment adds a preset logic algorithm to execute corresponding protection actions, so it can monitor the working status of the switching power supply in real time and accurately identify output short-circuit faults.

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

[0077] As a specific implementation of this embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, no primary side drive is issued, thereby avoiding the risk of output voltage overshoot caused by the inconsistency of the reference voltage VREF of the feedback loop of the two secondary sides of the switching power supplies due to process deviation, resulting in one being in the primary side soft start stage and the other being in the stable working stage.

[0078] As a specific implementation of this embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, it is not identified whether the switching power supply has an output short circuit, thereby avoiding the risk of output voltage overshoot.

[0079] As a specific implementation of this embodiment, if the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, no primary side drive is issued, and it is not identified whether the switching power supply has an output short circuit.

[0080] Second embodiment

[0081] This embodiment provides a primary side control device, which is applied to a switching power supply. The switching power supply includes a transformer. Figure 2 This is a principle block diagram of a specific implementation of the primary side control device of the second embodiment of the present invention applied to a switching power supply, wherein the primary side control device includes:

[0082] a demodulation unit, 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 a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal;

[0083] The output short circuit detection and protection execution unit is used to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately shut down the primary side drive when the output of the switching power supply is identified to be short-circuited. After the third set time, the soft start is restarted. The conditions for determining the output short circuit of the switching power supply in different working stages are as follows:

[0084] In the soft start phase, if it is identified that the first occurrence of the 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 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;

[0085] In the stable working stage, if it is identified that the time when the feedback control signal FB 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;

[0086] Wherein: the first isolated signal VIOP is generated by the first modulation signal ISOP generated by the secondary feedback device and isolated by the isolation processing device; the second isolated signal VION is generated by the second modulation signal ISON generated by the secondary feedback device and isolated 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 AC signal outputted by the secondary side of the transformer into a DC voltage and obtains a first voltage signal VDIV representing the magnitude of the DC voltage;

[0089] A comparison output unit, which compares the first voltage signal with a reference voltage and outputs a PWM signal;

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

[0091] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects, so they 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 this embodiment, and this embodiment will not describe them one by one.

[0093] Figure 3 for Figure 2 For a specific block diagram of the output short-circuit detection and protection execution unit, see Figure 3, wherein the output short circuit detection and protection execution unit includes a counter, a control circuit and a soft start circuit; the input terminal CLK1 of the counter is used to input a clock signal, the first output terminal CLK_DET_HW is connected to the first input terminal of the control circuit, the second output terminal CLK_SCP1 is connected to the second input terminal of the control circuit, the third output terminal CLK_DET_0 is connected to the third input terminal of the control circuit, and the fourth output terminal CLK_SCP2 is connected to the fourth input terminal of the control circuit; the fifth input terminal of the control circuit is used to input a feedback control signal FB, the first output terminal SOFT_EN of the control circuit is connected to the first input terminal of the soft start circuit, and the second output terminal SECOND_EN of the control circuit is connected to the second input terminal of the pseudo-random circuit; the SYS_OUT terminal of the soft start circuit outputs an initial driving signal;

[0094] The counter uses the input clock signal as the initial frequency to time the first set time, the second set time and the third set time;

[0095] The control circuit is used to detect the feedback control signal FB to generate a first setting time, a second setting time, a third setting time and an enable signal;

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

[0097] Furthermore, the output short circuit detection and protection execution unit also includes a pseudo-random circuit for converting an initial driving signal with a fixed frequency into a variable frequency driving signal based on a pseudo-random number, thereby achieving the purpose of reducing EMI and improving power supply performance.

[0098] Third embodiment

[0099] This embodiment provides a secondary side feedback device, which is applied to a switching power supply, wherein the switching power supply includes a transformer, wherein the secondary side feedback device includes:

[0100] An output voltage rectification detection unit, used to convert the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtain a first voltage signal VDIV representing the magnitude of the DC voltage;

[0101] A comparison output unit, used for comparing the first voltage signal with a reference voltage and outputting a PWM signal;

[0102] A modulation unit, used for modulating the PWM signal into a first modulation signal ISOP and a second modulation signal ISON;

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

[0104] A demodulation unit, used for demodulating the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal;

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

[0106] In the soft start phase, if it is identified that the first occurrence of the 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 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 operation stage, if 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.

[0108] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects, so they will not be 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 this embodiment, and this embodiment will not describe them one by one.

[0110] Fifth embodiment

[0111] This embodiment provides a switching power supply, which includes a transformer, wherein: the switching power supply also includes the primary side control device and the isolation processing device described in any one of the second embodiments and the secondary side feedback device described in any one of the third embodiments.

[0112] Figure 4 for Figure 2 The control timing diagram of the switching power supply, combined with Figure 4 right Figure 2 The working process of the switching power supply is analyzed as follows:

[0113] (1) During the soft start control process, the primary side soft start is initially 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 duty cycle of the primary side soft start output signal gradually increases, two situations may occur:

[0114] Case 1, the voltage division of the secondary output voltage VISO (i.e., the first voltage signal characterizing the DC voltage) VDIV>VREF, then PWM=1, feedback control signal FB=1: if the first occurrence of the 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 output of the switching power supply is short-circuited, the primary soft start is immediately turned off, and the short-circuit protection waiting time is entered. After the waiting time is over, the system restarts the soft start; when the first occurrence of the feedback control signal FB=1 is detected and the duration is greater than the first set time, the primary soft start ends and starts to switch to the feedback control signal FB closed-loop control;

[0115] In case 2, the voltage division VDIV of the secondary output voltage VISO is less than VREF, then FB=0, and it is detected that the feedback control signal FB is continuously equal to 0 for a time greater than the second set time, and the output of the switching power supply is also determined to be short-circuited, and the primary side soft start is immediately turned off, and the short-circuit protection waiting time is entered. After the waiting time ends, the soft start is restarted;

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

[0117] Figure 5This is the control timing diagram when the switching power supply output is applied in parallel. As shown in the figure, VREF1 is the reference voltage of the switching power supply feedback loop of the secondary side of chip 1 in the first branch, and VREF2 is the reference voltage of the switching power supply feedback loop of the secondary side of chip 2 in the second branch. During 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, and the primary side is not driven, so the output voltage overshoot of the parallel output application can be avoided until chip 2 enters the steady-state working stage, and the system output voltage can be stabilized near the rated voltage.

[0118] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations of the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A short circuit protection control method, applied to a switching power supply, wherein the switching power supply comprises a transformer, characterized in that: The short circuit protection control method comprises: An output voltage rectification detection step, converting the AC signal output by the secondary side of the transformer into a DC voltage, and obtaining a first voltage signal VDIV representing the magnitude of the DC voltage; A comparison and output step, comparing the first voltage signal with a reference voltage to output a PWM signal; A modulation step of modulating the PWM signal into a first modulation signal ISOP and a second modulation signal ISON; an isolation processing step, isolating the first modulation signal ISOP into a first isolation signal VIOP, and isolating the second modulation signal ISON into a second isolation signal VION; A demodulation step, demodulating the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal; Output 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 re-starting the soft start after the third set time. The conditions for determining whether the output of the switching power supply is short-circuited in different working stages are as follows: In the soft start phase, if it is identified that the first occurrence of the 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 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; In the stable operation stage, if 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.

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

3. The short circuit protection control method according to claim 1, characterized in that: 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 issued.

4. The short circuit protection control method according to claim 1, characterized in that: If the switching power supply includes two parallel outputs, when the feedback control signal FB is equal to 1, it is not identified whether the switching power supply has an output short circuit.

5. The short circuit protection control method according to claim 1, characterized in that: 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 issued, and it is not identified whether the switching power supply has an output short circuit.

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, configured to receive a first isolation signal VIOP and a second isolation signal VION transmitted by the isolation processing unit, and demodulate the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal; The output short circuit detection and protection execution unit is used to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately shut down the primary side drive when the output of the switching power supply is identified to be short-circuited, and restart the soft start after the third set time. The conditions for determining whether the output of the switching power supply is short-circuited in different working stages are as follows: In the soft start phase, if it is identified that the first occurrence of the 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 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; In the stable working stage, if it is identified that the time when the feedback control signal FB 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; Wherein: the first isolation signal VIOP is generated by the first modulation signal ISOP generated by the secondary feedback device and isolated and processed by the isolation processing device; the second isolation signal VION is generated by the second modulation signal ISON generated by the secondary feedback device and isolated and processed 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: An output voltage rectification detection unit converts the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtains a first voltage signal VDIV representing the magnitude of the DC voltage; A comparison output unit, which 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 according to claim 6, characterized in that: The output short circuit detection and protection execution unit includes a counter, a control circuit and a soft start circuit; the input terminal CLK1 of the counter is used to input a clock signal, the first output terminal CLK_DET_HW is connected to the first input terminal of the control circuit, the second output terminal CLK_SCP1 is connected to the second input terminal of the control circuit, the third output terminal CLK_DET_0 is connected to the third input terminal of the control circuit, and the fourth output terminal CLK_SCP2 is connected to the fourth input terminal of the control circuit; the fifth input terminal of the control circuit is used to input the feedback control signal FB, the first output terminal SOFT_EN of the control circuit is connected to the first input terminal of the soft start circuit, and the second output terminal SECOND_EN of the control circuit is connected to the second input terminal of the pseudo-random circuit; the SYS_OUT terminal of the soft start circuit outputs an initial drive signal; The counter uses the input clock signal as an initial frequency to time the first set time, the second set time and the third set time; The control circuit is used to detect the feedback control signal FB to generate the first setting time, the second setting time, the third setting time and an enable signal; The soft start circuit is used to generate the initial driving signal under the action of the enable signal.

8. The primary side control device according to claim 7, characterized in that: The output short circuit detection and protection execution unit also includes a pseudo-random circuit for converting an initial driving signal with a fixed frequency into a variable frequency driving signal based on a pseudo-random number, thereby achieving the purpose of reducing EMI and improving power supply performance.

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 comprises: An output voltage rectification detection unit, used for converting the AC signal outputted by the secondary side of the transformer into a DC voltage, and obtaining a first voltage signal VDIV representing the magnitude of the DC voltage; A comparison output unit, used for comparing the first voltage signal with a reference voltage and outputting a PWM signal; 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 and processed by the isolation processing device into a first isolation signal VIOP, and the second modulation signal ISON is isolated and processed by the isolation processing device into a second isolation signal VION, and the primary side control device performs short circuit protection control through the following units according to the first isolation signal VIOP and the second isolation signal VION: a demodulation unit, configured to demodulate the first isolation signal VIOP and the second isolation signal VION into a feedback control signal FB, wherein the feedback control signal FB is a narrow pulse signal; The output short circuit detection and protection execution unit is used to determine whether the output of the switching power supply is short-circuited according to the feedback control signal FB, and immediately shut down the primary side drive when the output of the switching power supply is identified to be short-circuited, and restart the soft start after the third set time. The conditions for determining whether the output of the switching power supply is short-circuited in different working stages are as follows: In the soft start phase, if it is identified that the first occurrence of the 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 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; In the stable operation stage, if 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.

10. A switching power supply, comprising a transformer, characterized in that: The switching power supply further comprises the primary side control device and the isolation processing device as described in any one of claims 6 to 8 and the secondary side feedback device as described in claim 9.

Images