Control method and device of synchronous rectifier, medium, processor and switching power supply

Abstract

The invention relates to a control method and device of a synchronous rectifier, a medium, a processor and a switching power supply, and the control method comprises the steps: a first obtaining step: obtaining a first voltage signal representing the drain-source voltage of the synchronous rectifier; a second obtaining step: obtaining duration time representing that the first voltage signal is smaller than or equal to a first voltage threshold value; an execution step: giving the initial control mode of the synchronous rectifier as a second control mode, and switching the control mode of the synchronous rectifier between the first control mode and the second control mode according to a preset condition; wherein the first control mode is that the synchronous rectifier is switched on only when the duration time is longer than or equal to first time, the second control mode is that the synchronous rectifier is switched on only when the duration time is longer than or equal to second time, and the second time is longer than the first time. The control method is simple, and the anti-interference capability of the synchronous rectifier and the efficiency of the switching power supply can be improved.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly relates to a control method, device, medium, processor and switching power supply of a synchronous rectifier. Background Art

[0002] In the field of DC-DC converter switching power supply technology, according to application requirements and electrical isolation needs, DC-DC converters are divided into non-isolated DC converters and isolated DC converters. In applications such as electric vehicles, data centers, and on-vehicle chargers, in order to protect personal safety, isolated DC-DC converters are required. Isolated DC-DC converters are generally further divided into resonant converters and non-resonant converters. Compared with non-resonant converters, resonant converters have advantages such as sinusoidal waveforms and inherent soft switching. Resonant switching power supplies can operate at higher frequencies with low switching losses, can use smaller magnetic components, and still have high efficiency while ensuring small volume. At the same time, since resonant converter switching power supplies generally do not have sharp waveforms (such as waveforms with high di / dt or dv / dt), the EMI performance is improved, so smaller EMI filters can be used.

[0003] Of course, while resonant converters have the above advantages, they also have some disadvantages. The secondary-side synchronous rectifier in the converter is used to rectify the output current of the secondary winding to generate the secondary-side current, and this current charges the output capacitor. Under low-load conditions, the parasitic capacitance Coss of the synchronous rectifier may resonate, thereby causing capacitive current spikes in the secondary-side circuit. This capacitive current spike may mis-trigger the secondary-side synchronous rectifier, and energy backflow may occur, causing problems such as damage to the converter.

[0004] To solve the above problems, generally, the function of increasing the turn-on delay of the synchronous rectifier is adopted. Many companies have relevant patents, but there are certain problems. For example, in the US Patent US10164543B2 proposed by SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC, Phoenix, AZ (US), it is necessary to judge whether to enter light no-load according to the adaptive dead time, etc., so as to adjust the turn-on delay. If the adaptive dead time function is not required, the complexity of the switching power supply system will be greatly increased.

[0005] There is also the US Patent US10734908B2 proposed by TEXAS INSTRUMENTS INCORPORATED, Dallas, TX (US), which also avoids capacitive current spikes by increasing the turn-on delay function of the synchronous rectifier.

[0006] All of the above - mentioned schemes have a common problem, which only increases the turn - on delay. After the delay time, the synchronous rectifier starts to conduct. At this time, there is no need to judge the magnitude relationship between the drain - source voltage and the turn - on threshold value, and the synchronous rectifier conducts directly. Because a fixed turn - on delay is adopted, the oscillation period of the capacitive current spike is related to the converter power parameters and parasitic parameters, and the variation range is relatively large. When it turns on, it may still be in the period of the capacitive current spike, and there are still problems such as energy back - flow. Therefore, the fixed turn - on delay cannot meet the requirements of wide - range applications. Summary of the Invention

[0007] In view of this, the problem to be solved by the present invention is to provide a control method, device, medium, processor and switching power supply for a synchronous rectifier, which can at least to a certain extent solve the deficiencies of the above - mentioned technical problems.

[0008] The inventive concept of the present application is as follows: changing the turn - on delay of the synchronous rectifier in the prior art to turn - on detection delay, and the synchronous rectifier includes two control modes, and the turn - on detection delays corresponding to the two modes are different. The control mode of the synchronous rectifier is switched according to preset conditions, so as to effectively avoid the problem of capacitive current spikes that are prone to occur under light load in resonant converters, and improve the anti - interference ability and efficiency of the converter.

[0009] The meaning of the turn - on detection delay is as follows: when it is detected that the drain - source voltage of the synchronous rectifier is less than or equal to the set value, the timing starts, and when it is detected that the drain - source voltage of the synchronous rectifier is greater than the set value, the timing ends. The timing time is the turn - on detection delay. The "first time" and "second time" of the present invention both belong to the "turn - on detection delay".

[0010] As the first aspect of the present invention, the technical solution of the embodiment of the control method for the synchronous rectifier is as follows:

[0011] A control method for a synchronous rectifier, which includes:

[0012] A first acquisition step of acquiring a first voltage signal representing the magnitude of the drain - source voltage of the synchronous rectifier;

[0013] A second acquisition step of acquiring the duration for which the first voltage signal is less than or equal to a first voltage threshold;

[0014] An execution step of setting the initial control mode of the synchronous rectifier as the second control mode, and switching the control mode of the synchronous rectifier between the first control mode and the second control mode according to preset conditions;

[0015] Wherein: in the first control mode, the synchronous rectifier is turned on only when the duration is greater than or equal to a first time; in the second control mode, the synchronous rectifier is turned on only when the duration is greater than or equal to a second time, and the second time is greater than the first time.

[0016] Further, the second time is adjustable.

[0017] Further, the preset condition includes: when the synchronous rectifier is in the first control mode, during the minimum turn-on period, if a reverse current is detected flowing through the synchronous rectifier, the control mode of the synchronous rectifier is switched to the second control mode, and the synchronous rectifier is immediately turned off.

[0018] Further, if the first voltage signal continuously exceeds a third voltage threshold within a third time, it is determined that a reverse current is flowing through the synchronous rectifier.

[0019] Preferably, the third voltage threshold is greater than or equal to -10 mV and less than or equal to 100 mV.

[0020] Further, the preset condition includes: when the synchronous rectifier is in the second control mode, the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold only once is detected at a set time interval before the synchronous rectifier is turned on in each cycle. If it is detected that the number of times in N consecutive cycles is 1 and N reaches a preset value, the control mode of the synchronous rectifier is switched to the first control mode, where N is a natural number greater than or equal to 1.

[0021] Further, the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold only once is detected at a set time interval before the synchronous rectifier is turned on in each cycle includes: before the synchronous rectifier is turned on, the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is recorded in a first counter, and there is the time interval after the first counter counts. If the first voltage signal is detected to change from being greater than the first voltage threshold to being less than or equal to the first voltage threshold again within the time interval, the first counter does not count. The first counter resumes counting only when the time interval ends and the first voltage signal is detected to change from being greater than the first voltage threshold to being less than or equal to the first voltage threshold, and the first counter is cleared in each cycle.

[0022] Further, the detection that the number of times in N consecutive cycles is 1 and N reaches a preset value includes: if the count of the first counter is equal to 1, increment the second counter by 1; if the count of the first counter is greater than 1, clear the second counter. The count in the second counter is the N.

[0023] Preferably, the N is any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.

[0024] As a second aspect of the present invention, the technical solution of the embodiment of the control device of the synchronous rectifier is as follows:

[0025] A synchronous rectification control device, characterized by comprising:

[0026] A first acquisition module, configured to acquire a first voltage signal characterizing the magnitude of the drain-source voltage of the synchronous rectifier;

[0027] A second acquisition module, configured to acquire the duration during which the first voltage signal is less than or equal to a first voltage threshold;

[0028] An execution module, configured to set an initial control mode of the synchronous rectifier as a second control mode, and switch the control mode of the synchronous rectifier between a first control mode and the second control mode according to a preset condition;

[0029] Wherein: the first control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a first time; the second control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a second time, and the second time is greater than the first time.

[0030] As a third aspect of the present invention, the embodiment of the computer-readable storage medium is as follows:

[0031] A computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program runs, it executes the method according to any one of the above first aspects.

[0032] As a fourth aspect of the present invention, the embodiment of the processor is as follows:

[0033] A processor, wherein the processor is used to run a program, and when the program runs, it executes the method according to any one of the above first aspects.

[0034] As a fifth aspect of the present invention, the embodiment of the switching power supply is as follows:

[0035] A switching power supply includes a synchronous rectifier, wherein the synchronous rectifier is controlled by the control device described in the second aspect above.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The embodiments of the present invention include two control modes. The turn-on detection delays corresponding to the two modes are different, and the control mode of the synchronous rectifier is switched according to preset conditions, so as to effectively avoid the capacitive current spike problem that easily occurs under light load in resonant converters, avoid energy backflow under light load, and improve the anti-interference ability and efficiency of the converter;

[0038] (2) The embodiments of the present invention can also adjust the second time according to different converters, so as to broaden the application range, make the converter more efficient and have stronger anti-interference ability, and have a wide application prospect. Description of the Drawings

[0039] Figure 1 is a typical structural diagram of an LLC resonant converter topology;

[0040] Figure 2 is a waveform diagram of an embodiment of the existing control scheme;

[0041] Figure 3 is a flowchart of the control method of the synchronous rectifier according to the first embodiment of the present invention;

[0042] Figure 4 is a schematic diagram of the control device of the synchronous rectifier according to the second embodiment of the present invention;

[0043] Figure 5 The switching power supply of the fifth embodiment of the present invention adopts Figure 1 the waveform of the circuit topology. Detailed Embodiments

[0044] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0045] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions 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 a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present application.

[0046] It should be noted that in the description, claims and the above-mentioned drawings of this application, the terms "first", "second", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to describe the embodiments of this application here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0047] It should be understood that in the description, claims and the drawings of the specification, when it is described that one step follows another step, this step can directly follow this other step, or follow this other step through a third step; when it is described that an element / unit "follows" another element / unit, this element / unit can be "directly connected" to this other element / unit, or "connected" to this other element / unit through a third element / unit.

[0048] In addition, the drawings of this disclosure are only schematic diagrams of this disclosure and are not necessarily drawn to scale. The same reference signs in the drawings represent the same or similar parts, and thus the repeated description thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily have to correspond to physically or logically independent entities. These functional entities can be implemented by software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0049] The present invention is particularly applicable to resonant converters. Figure 1 is a typical structural diagram of an LLC resonant converter topology, as Figure 1 shown, which includes a high-side transistor Q1, a low-side transistor Q2, a transformer T, an inductor Lr, a capacitor Cr, a synchronous rectifier S1, a synchronous rectifier S2, and a synchronous rectification controller. Among them, the high-side transistor Q1 and the low-side transistor Q2 form a half-bridge, and the inductor Lr, the capacitor Cr, and the magnetic-ring inductor Lm form a resonant circuit. The synchronous rectifier S1 and the synchronous rectifier S2 are coupled to the secondary winding of the transformer T and the synchronous rectification controller, and are controlled by the synchronous rectification controller. The synchronous rectification controller detects the drain-source voltage of the synchronous rectifier S1 and generates a gate voltage for the synchronous rectifier S1 according to the drain-source voltage. Specifically, the synchronous rectification controller turns on the synchronous rectifier S1 by detecting the forward-biased body diode of the synchronous rectifier S1, and turns off the synchronous rectifier S1 by detecting that the current in the synchronous rectifier S1 is close to 0. Similarly, the control of the synchronous rectifier S2 is the same.

[0050] In one embodiment, when a first voltage signal representing the magnitude of the synchronous rectifier drain-source voltage is less than or equal to a first voltage threshold, the synchronous rectifier S1 is turned on and remains on for a predetermined minimum on-time. When the minimum on-time ends, if it is detected that the first voltage signal representing the magnitude of the synchronous rectifier drain-source voltage is greater than a second voltage threshold, the synchronous rectifier S1 generates a low (e.g., 0V) gate voltage to turn off. The synchronous rectifier S2 also operates in a similar manner.

[0051] It should be noted that the above circuit topology and control strategy are only examples of the topology and control strategy of the switching power supply involved in the present invention, and should not constitute a limitation on the topology and control strategy of the switching power supply involved in the present invention.

[0052] As Figure 2 shown, it is a waveform of an embodiment of the prior art synchronous rectifier control method. The prior art synchronous rectifier control method is that when a capacitive current spike is detected during or under a light load condition, the turn-on delay is increased to twice the original value to skip the capacitive current spike state, where ID is the current flowing through the synchronous rectifier S1 or S2, VDS is the drain-source voltage of the synchronous rectifier S1 or S2, minON is the minimum on-time of the synchronous rectifier, DELY is the turn-on delay of the synchronous rectifier, and VG is the gate voltage of the synchronous rectifier S1 or S2.

[0053] Please continue to refer to Figure 2 , in the time period from t1 to t6, at time t1, it is detected that VDS is less than the first voltage threshold, and the synchronous rectifier turns on at time t2 after a fixed turn-on delay. Due to the existence of the minimum on-time (t2 - t3), the synchronous rectifier cannot turn off. During the minimum on-time, the current ID reverses, and it is detected that a capacitive current spike appears. In the next cycle, the fixed turn-on delay is increased to twice the original value, and the waveform is as shown in Figure 2 the time period from t7 to t10. At time t7, it is detected that VDS is less than the first voltage threshold, and the synchronous rectifier conducts at time t8 after a 2-fold fixed turn-on delay. At this time, it is still during the capacitive current spike period, and due to the existence of the minimum on-time, it cannot turn off normally. During this period, energy backflow may occur and affect the converter. Seriously, it may cause damage to the converter. After the minimum on-time ends and the VDS voltage is less than the second voltage threshold, it conducts and turns off normally during the time period from t9 to t10.

[0054] In summary, when a capacitive current spike exists, increasing the turn-on delay to twice the original value cannot ensure that the capacitive current spike ends during this period. There may be a problem that the capacitive current spike does not end but the synchronous rectifier turns on, resulting in energy backflow, that is, the existing solution is not applicable to some switching power supplies, which limits the scope of application.

[0055] To solve the above problems, the present invention changes the turn-on delay in the prior art to turn-on detection delay, that is, the drain-source voltage of the synchronous rectifier needs to continuously be less than or equal to the set value to control the turn-on of the synchronous rectifier. When there is a capacitive current spike, the turn-on detection delay increases; when there is no capacitive current spike, the turn-on detection delay decreases, and there is a function of adaptive switching of the control mode.

[0056] The First Embodiment

[0057] The present embodiment provides a control method for a synchronous rectifier. Figure 3 For the flowchart of the control method of the synchronous rectifier in the first embodiment of the present invention, please refer to Figure 3 , including:

[0058] S100, the first acquisition step, to acquire a first voltage signal representing the magnitude of the drain-source voltage of the synchronous rectifier;

[0059] S200, the second acquisition step, to acquire the duration for which the first voltage signal is less than or equal to the first voltage threshold;

[0060] S300, the execution step, to set the initial control mode of the synchronous rectifier as the second control mode, and switch the control mode of the synchronous rectifier between the first control mode and the second control mode according to preset conditions;

[0061] Wherein: the first control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to the first time, and the second control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to the second time, and the second time is greater than the first time.

[0062] The control method of the present embodiment includes two control modes. The turn-on detection delays corresponding to the two modes are different, and the control mode of the synchronous rectifier is switched according to preset conditions, so as to effectively avoid the problem of capacitive current spikes that are prone to occur under light load in resonant converters, avoid energy backflow under light load, and improve the anti-interference ability and efficiency of the converter.

[0063] Furthermore, the second time is adjustable. Specifically, the second time can be adjusted according to different converters, so as to broaden the application range, make the converter more efficient and have stronger anti-interference ability, and have a wide range of application prospects.

[0064] Among them, the preset conditions include two situations:

[0065] (1) The preset condition for switching from the first control mode to the second control mode when the synchronous rectifier is in the first control mode

[0066] In this case, the preset condition is that if a reverse current is detected in the synchronous rectifier, the control mode of the synchronous rectifier is switched to the second control mode, and the synchronous rectifier is immediately turned off.

[0067] Further, if the first voltage signal continuously exceeds the third voltage threshold within the third time period, it is determined that a reverse current is flowing in the synchronous rectifier.

[0068] Preferably, the third voltage threshold is greater than or equal to -10 mV and less than or equal to 100 mV.

[0069] (2) Preset conditions for switching to the first control mode when the synchronous rectifier is in the second control mode

[0070] In this case, the preset condition is that the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is detected only once at a set time interval (such as 50 ns) before the synchronous rectifier is turned on for each cycle. If it is detected that the number of times in N consecutive cycles is 1 and N reaches a preset value, the control mode of the synchronous rectifier is switched to the first control mode, where N is a natural number greater than or equal to 1.

[0071] Further, detecting the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold only once at a set time interval before the synchronous rectifier is turned on for each cycle includes: before the synchronous rectifier is turned on, the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is recorded in the first counter, and there is a time interval after the first counter counts. If the first voltage signal is detected to change from being greater than the first voltage threshold to being less than or equal to the first voltage threshold again within the time interval, the first counter does not count. The first counter continues to count only when the first voltage signal is detected to change from being greater than the first voltage threshold to being less than or equal to the first voltage threshold after the time interval ends, where the first counter is cleared for each cycle. It should be noted that the time interval can be any value, and the specific design of the present invention is not limited; if the first voltage signal is detected to change from being greater than the first voltage threshold to being less than or equal to the first voltage threshold again within the time interval, the number of times of the re-detection includes one or more times.

[0072] Further, detecting that the number of consecutive N cycles is all 1 and N reaches a preset value includes: if the count of the first counter is equal to 1, then increment the second counter by 1; if the count of the first counter is greater than 1, then clear the second counter. The count in the second counter is N. It should be noted that if the synchronous rectifier is turned on, there must be a time when the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold, that is, the first voltage signal will not change 0 times from greater than the first voltage threshold to less than or equal to the first voltage threshold, so the first counter will not have a situation of 0.

[0073] Preferably, N is any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.

[0074] Second Embodiment

[0075] The control device provided in this embodiment is a control device for a synchronous rectifier. Figure 4 For the flowchart of the control device of the synchronous rectifier in the second embodiment of the present invention, please refer to Figure 4 , including:

[0076] A first acquisition module, configured to acquire a first voltage signal representing the magnitude of the drain-source voltage of the synchronous rectifier;

[0077] A second acquisition module, configured to acquire the duration during which the first voltage signal is less than or equal to the first voltage threshold;

[0078] An execution module, configured to set the initial control mode of the synchronous rectifier as the second control mode, and switch the control mode of the synchronous rectifier between the first control mode and the second control mode according to a preset condition;

[0079] Wherein: the first control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to the first time, and the second control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to the second time, and the second time is greater than the first time.

[0080] The technical means adopted by the control device in this embodiment correspond to those of the control method in the first embodiment, and the beneficial effects are the same.

[0081] Further, the second time is adjustable. Specifically, the second time can be adjusted according to different converters, so as to broaden the application range, make the converter more efficient and have stronger anti-interference ability, and have a wide application prospect.

[0082] Among them, the preset condition includes two situations:

[0083] (1) The preset condition for switching to the second control mode when the synchronous rectifier is in the first control mode

[0084] In this case, the preset condition is that if a reverse current is detected flowing through the synchronous rectifier, the control mode of the synchronous rectifier is switched to the second control mode, and the synchronous rectifier is immediately turned off.

[0085] Furthermore, if the first voltage signal continuously exceeds the third voltage threshold within the third time period, it is determined that a reverse current is flowing through the synchronous rectifier.

[0086] Preferably, the third voltage threshold is greater than or equal to -10 mV and less than or equal to 100 mV.

[0087] (2) Preset conditions for switching to the first control mode when the synchronous rectifier is in the second control mode

[0088] In this case, the preset condition is that the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is detected only once at a set time interval (such as 50 ns) before the synchronous rectifier is turned on for each cycle. If it is detected that the number of times in N consecutive cycles is 1, and when N reaches a preset value, the control mode of the synchronous rectifier is switched to the first control mode, where N is a natural number greater than or equal to 1.

[0089] Furthermore, detecting the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold only once at a set time interval before the synchronous rectifier is turned on for each cycle includes: before the synchronous rectifier is turned on, the number of times the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is recorded in the first counter, and there is a time interval after the first counter counts. If the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold again within the time interval, the first counter does not count. The first counter continues to count only when the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold is detected after the time interval ends, where the first counter is cleared for each cycle. It should be noted that the time interval can be any value, and the specific design of the present invention is not limited; if the first voltage signal changes from being greater than the first voltage threshold to being less than or equal to the first voltage threshold again within the time interval, the first counter does not count, and the number of times of the re-detection includes one or more times.

[0090] Furthermore, detecting that the number of times in N consecutive cycles is 1 and N reaches the preset value includes: if the count of the first counter is equal to 1, the second counter is incremented by 1; if the count of the first counter is greater than 1, the second counter is cleared, and the count in the second counter is N.

[0091] Preferably, N is any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.

[0092] Third Embodiment

[0093] In the above second embodiment, if the units integrated in the control device are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in the various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), mobile hard disks, magnetic disks, or optical discs that can store program codes.

[0094] Therefore, the third embodiment of the present invention provides a computer-readable storage medium, which includes a stored program, and the program executes the method of any one of the specific embodiments in the first embodiment.

[0095] Fourth Embodiment

[0096] The fourth embodiment of the present invention provides a processor for running a program, wherein when the program runs, it executes the method of any one of the specific embodiments in the first embodiment.

[0097] Fifth Embodiment

[0098] The fifth embodiment of the present invention provides a switching power supply, which includes a synchronous rectifier, and wherein the synchronous rectifier is controlled by any one of the control devices in the second embodiment above.

[0099] The synchronous rectifier in the switching power supply of this embodiment is controlled by any one of the control devices in the second embodiment above. Therefore, it can effectively avoid the problem of capacitive current spikes that are prone to occur when the resonant converter is lightly loaded, prevent energy backflow when lightly loaded, and improve the anti-interference ability and efficiency of the converter.

[0100] Figure 5 The switching power supply of the fifth embodiment of the present invention adopts Figure 1Waveforms of the circuit topology, where ID is the current flowing through synchronous rectifier S1 or S2, VDS is the drain-source voltage of synchronous rectifier S1 or S2, FLAG is the turn-on detection delay flag bit (high level represents the second control mode, low level represents the first control mode), DELY is the timing signal for the duration when the drain-source voltage of the synchronous rectifier is less than the first voltage threshold, and VG is the gate voltage of synchronous rectifier S1 or S2.

[0101] In the time period from t1 to t3, the capacitive current spike is detected for the first time. At t1, it is detected that VDS is less than the first voltage threshold, and it remains less than the first voltage threshold during the time period from t1 to t2, which is the first time (i.e., the first turn-on detection delay) T1. Therefore, at t2, the synchronous rectifier controller controls the synchronous rectifier to conduct. However, since there is a capacitive current spike at this time and it is within the minimum turn-on time, it is detected that VDS is greater than the third voltage threshold and the duration is greater than the third time T3 during the time period from t2 to t3, and the synchronous rectifier is immediately turned off. At the same time, the first control mode is switched to the second control mode, and the FLAG flag bit is set high.

[0102] In the time period from t4 to t8, there is still a capacitive current spike in the switching power supply. At this time, it is in the second control mode. During the time period from t4 to t5, although it is detected that VDS is less than the first voltage threshold, its duration is less than the second time (i.e., the second turn-on detection delay) T2. Therefore, the synchronous rectifier does not conduct. After the capacitive current spike ends, that is, at t6, it is detected again that VDS is less than the first voltage threshold, and the duration is greater than the second time T2, that is, during the time period from t6 to t7, the synchronous rectifier conducts and then turns off normally later.

[0103] After a certain period, in the time period from t9 to t11, there is no capacitive current spike in the switching power supply. At this time, it is still in the second control mode, that is, it is detected that VDS continuously remains less than the first voltage threshold during the time period from t9 to t10, meeting the second time T2. At t10, the synchronous rectifier conducts. At t11, VDS is greater than the second voltage threshold and the synchronous rectifier turns off normally. In this cycle, before t10 (when the synchronous rectifier conducts), it is only detected once that VDS changes from greater than the first voltage threshold to less than or equal to the first voltage threshold, and the second counter is incremented by 1. In the time period from t11 to t12, before the synchronous rectifier conducts in N cycles, it is only detected once that VDS changes from greater than the first voltage threshold to less than or equal to the first voltage threshold, and the count value of the second counter reaches the preset number, meeting the preset condition, and the second control mode is switched to the first control mode.

[0104] In the time period from t12 to t14 and after t14, it is in the first control mode until the capacitive current spike is detected again.

[0105] Specifically, the second time T2 in the second control mode can be adjusted according to different switching power supplies to meet a wider operating range.

[0106] By comparison Figure 2 and Figure 5 It is obvious that by replacing the turn-on delay with the turn-on detection delay, the problem of false turn-on during the capacitive current spike can be effectively avoided.

[0107] This solution also includes immediately turning off the synchronous rectifier when reverse current is detected, rather than waiting for the minimum turn-on time to end, which can minimize the impact caused by the capacitive current spike. In addition, the second control mode needs to meet certain requirements for several consecutive cycles to switch to the first control mode, avoiding contingency.

[0108] In summary, this control method broadens the applicable range, making the overall efficiency of the converter higher and the anti-interference ability stronger, with broad application prospects.

[0109] The above description is only an example of the technical solution and the content of the present invention. It should be noted that the above embodiments should not be regarded as a limitation of the present invention. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, several improvements and refinements can be made, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims, and should also be regarded as the protection scope of the present invention.

Claims

1. A control method for a synchronous rectifier, characterized in that, Including: A first obtaining step of obtaining a first voltage signal representing the magnitude of the drain-source voltage of the synchronous rectifier; A second obtaining step of obtaining the duration for which the first voltage signal is less than or equal to a first voltage threshold; An execution step of setting the initial control mode of the synchronous rectifier to a second control mode and switching the control mode of the synchronous rectifier between a first control mode and the second control mode according to a preset condition; Wherein: the first control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a first time, the second control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a second time, and the second time is greater than the first time.

2. The control method of the synchronous rectifier according to claim 1, characterized in that: The second time is adjustable.

3. The control method of the synchronous rectifier according to claim 1, wherein The preset condition includes: when the synchronous rectifier is in the first control mode, during the minimum on-time, if a reverse current is detected flowing through the synchronous rectifier, the control mode of the synchronous rectifier is switched to the second control mode, and the synchronous rectifier is immediately turned off.

4. The control method of the synchronous rectifier according to claim 3, wherein: If the first voltage signal continuously exceeds a third voltage threshold within a third time, it is determined that a reverse current is flowing through the synchronous rectifier.

5. The control method of the synchronous rectifier according to claim 4, wherein: The third voltage threshold is greater than or equal to -10 mV and less than or equal to 100 mV.

6. The control method of the synchronous rectifier according to claim 1, wherein The preset condition includes: when the synchronous rectifier is in the second control mode, the number of times the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold is detected only once at a set time interval before the synchronous rectifier is turned on in each cycle. If it is detected that the number of times in N consecutive cycles is 1 and N reaches a preset value, the control mode of the synchronous rectifier is switched to the first control mode, where N is a natural number greater than or equal to 1.

7. The control method of the synchronous rectifier according to claim 6, characterized in that, The step of detecting the number of times the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold only once at a set time interval before the synchronous rectifier is turned on in each cycle includes: before the synchronous rectifier is turned on, the number of times the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold is recorded in a first counter, and there is the time interval after the first counter counts. If the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold again within the time interval, the first counter does not count. The first counter continues to count only after the time interval ends and the first voltage signal changes from greater than the first voltage threshold to less than or equal to the first voltage threshold, and the first counter is cleared in each cycle.

8. The control method of the synchronous rectifier according to claim 7, characterized in that, The detection that the number of times in N consecutive cycles is 1 and N reaches the preset value includes: if the count of the first counter is equal to 1, a second counter is incremented by 1; if the count of the first counter is greater than 1, the second counter is cleared, and the count in the second counter is the N.

9. The control method of the synchronous rectifier according to claim 6, wherein: The N is any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.

10. A synchronous rectification control device, characterized in that Including: A first acquisition module, configured to acquire a first voltage signal representing the magnitude of the drain-source voltage of the synchronous rectifier; A second acquisition module, configured to acquire the duration during which the first voltage signal is less than or equal to a first voltage threshold; An execution module, configured to set an initial control mode of the synchronous rectifier as a second control mode, and switch the control mode of the synchronous rectifier between a first control mode and the second control mode according to a preset condition; Wherein: the first control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a first time, the second control mode is to turn on the synchronous rectifier only when the duration is greater than or equal to a second time, and the second time is greater than the first time.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein the program, when running, executes the method according to any one of claims 1 to 9.

12. A processor, characterized in that, The processor is configured to run a program, wherein the program, when running, executes the method according to any one of claims 1 to 9.

13. A switching power supply, comprising a synchronous rectifier, characterized in that: The synchronous rectifier is controlled by the control device according to claim 10 of the claims.

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