A control method, device, medium, processor and switching power supply of a switching power supply

Abstract

The present invention discloses a control method, device, medium, processor and switching power supply of a switching power supply. The switching power supply includes a primary side circuit, a transformer and a secondary side circuit. The primary side circuit includes: first to third switching tubes, a first diode, a power supply capacitor, a clamping capacitor, a primary winding of the transformer and a control device; the positive input terminal of the switching power supply, the primary winding, the second switching tube, the first diode, the power supply capacitor and the input ground terminal of the switching power supply are connected in sequence to form a first loop; the positive input terminal of the switching power supply, the primary winding, the second switching tube, the first switching tube and the input ground terminal of the switching power supply are connected in sequence to form a second loop; one end of the clamping capacitor, the primary winding, the third switching tube and the other end of the clamping capacitor are connected in sequence to form a third loop. The control device controls the first to third switching tubes to be turned on and off, so that when the switching power supply is lightly no-loaded, the demagnetization energy and reverse demagnetization energy of the primary winding are not transmitted to the secondary side circuit, thereby avoiding high output voltage.

Description

Technical Field

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

[0002] In a switching power supply, a supply voltage signal is required to drive the components inside the switching power supply (such as drivers, clock signal generators, etc.). In AC-DC switching power supplies, low-voltage dropout linear regulators, integrated clamping circuits, and tertiary windings are often used to generate the supply voltage signal. Although the structure of using a low-voltage dropout linear regulator and an integrated clamping circuit to generate the supply voltage signal is simple, the loss is large, resulting in reduced efficiency of the switching power supply. Although the control method of generating the supply voltage signal VCC through the tertiary winding has a simple circuit, the tertiary winding will increase the cost of the AC-DC switching power supply and reduce its integration. To solve this difficulty, many researchers have invented patents such as the following:

[0003] Patent number CN106602883B discloses a power MOS tube switching power supply integrated power supply circuit without auxiliary winding. Figure 1a The patent provides a schematic diagram of the integrated power supply circuit of the power MOS tube switching power supply without auxiliary winding, in which the capacitor CVCC is the power supply capacitor.

[0004] Patent number CN107612107A discloses a power supply voltage generating circuit and its integrated circuit. Figure 1b This is a schematic diagram of the power supply voltage generating circuit and its integrated circuit provided in the patent, wherein capacitor 14 is a power supply capacitor.

[0005] The above patents and other prior patents for winding-free power supply mainly charge the power supply capacitor through the main winding. The switch tube on the charging circuit is saturated and turned on, so that the main winding is forwardly excited while charging the power supply capacitor, achieving the advantage of low loss in the charging circuit. Summary of the Invention

[0006] After research, the inventors of this application found that the above-mentioned scheme does achieve the effect of high conversion efficiency and saving the third winding when the load is large, but when the load is light, the power consumption of the primary chip needs to be reduced or the loss of the secondary side needs to be increased to meet the law of conservation of energy. The reason is that while the power supply capacitor is charging, the primary winding is also forwardly excited. When the energy required for the power consumption of the primary control device is met, the demagnetization energy of the primary winding of the transformer will be much greater than the energy required on the secondary side, which will eventually cause the output voltage to float high. Only by increasing the secondary power consumption can energy balance be achieved and the output voltage stabilized at the rated value. However, increasing the secondary power consumption will cause the light no-load power consumption to be too large and not meet the existing six-level energy efficiency standards.

[0007] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a control method, device, medium, processor and switching power supply for a switching power supply, so that when the switching power supply involved adopts a power supply scheme without auxiliary winding, there is no need to reduce the power consumption of the primary side chip or increase the loss on the secondary side under light no-load conditions.

[0008] As a first aspect of the present invention, an embodiment of a method for controlling a switching power supply is provided as follows:

[0009] A method for controlling a switching power supply, the switching power supply comprising a primary-side circuit, a transformer, and a secondary-side circuit, the primary-side circuit comprising: a first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, a primary winding of the transformer, and a control device; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and an input ground terminal of the switching power supply are sequentially connected to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are sequentially connected to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are sequentially connected to form a third loop, the control device controlling the conduction and disconnection of the first switching tube, the second switching tube, and the third switching tube; the control method comprising the following steps:

[0010] Acquire a first signal representing the current output power of the switching power supply;

[0011] Acquire a second signal representing a current voltage value across the power supply capacitor;

[0012] comparing the first signal with a first set value to generate a third signal;

[0013] comparing the second signal with a second set value to generate a fourth signal;

[0014] Based on the third signal and the fourth signal, the first switching tube, the second switching tube, and the third switching tube are controlled to be turned on and off, so that the switching power supply operates in different operating processes. Specifically, when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply.

[0015] Furthermore, when the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply, the demagnetization energy is first transferred to the clamping capacitor, and then the transformer is reversely excited through the clamping capacitor, and the reverse demagnetization energy is finally transferred to the input end of the switching power supply.

[0016] Furthermore, when the first signal is less than the first set value and the second signal is less than the second set value, the switching power supply operation process includes:

[0017] In the first stage, the first switch is turned off, the second switch is turned on, and the third switch is turned off. The primary winding of the transformer is forward excited through the first circuit and the power supply capacitor is charged at the same time.

[0018] In the second stage, the second switch is turned off, the primary winding of the transformer begins to be demagnetized, the body diode of the third switch is turned on first, and then the third switch is turned on. The demagnetization energy of the primary winding of the transformer is transferred to the clamping capacitor through the third loop, and the current in the primary winding of the transformer gradually decreases to zero.

[0019] In stage three, the third switching transistor is continuously turned on for a first period of time, the clamping capacitor reversely excites the primary winding of the transformer, the current in the primary winding of the transformer increases in the reverse direction from zero, and part of the energy of the clamping capacitor is transferred to the primary winding of the transformer through the third loop;

[0020] In stage 4, the third switch tube is turned off, the primary winding of the transformer begins to be reversely demagnetized, the body diode of the first switch tube and the body diode of the second switch tube are turned on, and the reverse demagnetization energy of the primary winding of the transformer is transferred to the input end of the switching power supply through the second loop.

[0021] Furthermore, in the third stage, when part of the energy of the clamping capacitor is transferred to the primary winding of the transformer, the voltage across the clamping capacitor is controlled to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply.

[0022] Furthermore, in the third stage, the voltage across the clamping capacitor is controlled to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply by controlling the first duration.

[0023] As a second aspect of the present invention, an embodiment of a control device for a switching power supply is provided as follows:

[0024] A control device for a switching power supply, the switching power supply comprising a primary-side circuit, a transformer, and a secondary-side circuit, the primary-side circuit comprising: a first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, a primary winding of the transformer, and a control device; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and an input ground terminal of the switching power supply are sequentially connected to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are sequentially connected to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are sequentially connected to form a third loop, the control device controlling the on and off of the first switching tube, the second switching tube, and the third switching tube; the control device comprising:

[0025] A first acquiring unit, configured to acquire a first signal representing a current output power of the switching power supply;

[0026] A second acquiring unit, configured to acquire a second signal representing a current voltage value across the power supply capacitor;

[0027] a first comparing unit, configured to compare the first signal with a first set value to generate a third signal;

[0028] a second comparing unit, configured to compare the second signal with a second set value to generate a fourth signal;

[0029] a processing unit, configured to control the on and off states of the first switching tube, the second switching tube, and the third switching tube based on the third signal and the fourth signal, so that the switching power supply operates in different operating processes, wherein when the first signal is less than the first set value and the second signal is less than the second set value, neither the demagnetization energy nor the reverse demagnetization energy of the primary winding of the transformer is transferred to the secondary-side circuit during the operation of the switching power supply.

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

[0031] A computer-readable storage medium, characterized in that the computer-readable storage medium includes a stored program, wherein the program executes any one of the above-mentioned control methods for the switching power supply.

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

[0033] A processor, characterized in that the processor is used to run a program, wherein when the program is run, any one of the above-mentioned control methods for a switching power supply is executed.

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

[0035] A switching power supply, comprising:

[0036] A primary-side circuit, a transformer, and a secondary-side circuit, wherein the primary-side circuit includes: a first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, the primary winding of the transformer, and a control device; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and the input ground terminal of the switching power supply are sequentially connected to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are sequentially connected to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are sequentially connected to form a third loop, and the control device controls the conduction and shutdown of the first switching tube, the second switching tube, and the third switching tube;

[0037] and the above-mentioned control device.

[0038] The embodiments of the present invention include at least the following beneficial effects: in the embodiments of the present invention, when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply, that is, the transformer energy is not transmitted to the secondary side when the switching power supply is lightly no-loaded and the power supply capacitor is undervoltage, thereby solving the problem that the primary side control device of the existing winding-free power supply scheme of the switching power supply consumes a lot of power, resulting in high output voltage and low no-load power consumption. Moreover, when the switching power supply allows the use of a control device with higher power consumption, for some complex control devices, the design difficulty of the control device can be greatly reduced. In addition, the power supply scheme without auxiliary winding can reduce the cost of the switching power supply and improve the integration of the switching power supply.

[0039] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained through the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1a The schematic diagram of the integrated power supply circuit of the existing power MOS tube switching power supply without auxiliary winding;

[0041] Figure 1b Schematic diagram of the circuit and integrated circuit for generating the existing power supply voltage;

[0042] Figure 2 A schematic diagram of an embodiment of a switching power supply circuit to which the present invention is applicable;

[0043] Figure 3 The present invention is aimed at Figure 2 A flow chart of an embodiment of a control method provided by the switching power supply shown;

[0044] Figure 4 The present invention is aimed at Figure 2 A schematic diagram of an embodiment of a control device provided by the switching power supply shown;

[0045] Figure 5 Working waveform diagram of the switching power supply embodiment of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0048] 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 described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0049] 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.

[0050] In addition, the figures of this disclosure are merely schematic diagrams of the present disclosure and are not necessarily drawn to scale. Identical reference numbers in the figures denote identical or similar parts, and therefore repeated descriptions thereof will be omitted. Some of the blocks shown in the figures are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented using software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontrollers.

[0051] Figure 2 FIG2 is a schematic diagram of an embodiment of a switching power supply circuit applicable to the present invention, including a primary side circuit, a transformer T1 and a secondary side circuit.

[0052] The primary-side circuit includes: a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, a first diode D1, a power supply capacitor Cv, a clamping capacitor C1, a primary winding Np of a transformer, and a control device U1. The positive input terminal Vin of the switching power supply, the primary winding Np of the transformer, the second switching tube Q2, the anode of the first diode D1, the cathode of the first diode D1, the power supply capacitor Cv, and the switching power supply input ground terminal GND are connected in sequence to form a first loop. The positive input terminal Vin of the switching power supply, the primary winding Np of the transformer, the second switching tube Q2, the first switching tube Q1, and the switching power supply input ground terminal GND are connected in sequence to form a second loop. One end of the clamping capacitor C1, the primary winding Np of the transformer, the third switching tube Q3, and the other end of the clamping capacitor C1 are connected in sequence to form a third loop. The control device U1 controls the conduction and shutdown of the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3.

[0053] The primary side circuit further includes an input filter capacitor Cin. The input filter capacitor Cin serves as a switching power supply. According to the technology in the field of the switching power supply, the function of the input filter capacitor Cin can be realized through an external capacitor. The technicians in this field can choose how to set it according to the actual situation. The switching power supply of the embodiment of the present invention does not limit whether to set this capacitor.

[0054] The secondary side circuit E1 includes: rectifier diode Do, output filter capacitor Co, the secondary side circuit can be a conventional flyback circuit, or a circuit of other topology. The rectification scheme can be adopted Figure 2The diode rectification scheme in the embodiment can also use a synchronous switch tube for synchronous rectification to improve the efficiency of the switching power supply. Those skilled in the art can design a specific secondary side circuit according to the actual application scenario requirements, and the switching power supply of the embodiment of the present invention is not limited to this.

[0055] The control device U1 outputs a control signal SW1 through a first control signal output terminal to control the on / off of the first switch tube Q1, outputs a control signal SW2 through a second control signal output terminal to control the on / off of the second switch tube Q2, and outputs a control signal SW3 through a third control signal output terminal to control the on / off of the third switch tube Q3. Different control methods will result in different working processes of the switching power supply, which are analyzed as follows:

[0056] (1) The transformer excitation stage is divided into the following two cases:

[0057] In case 1, the power supply capacitor Cv supplies power to the components inside the switching power supply, so that the energy stored in the power supply capacitor Cv is consumed. When it is detected that the voltage across the power supply capacitor Cv is less than the first undervoltage value V L1 When , the control device U1 controls the first switch tube Q1 to be turned off, the second switch tube Q2 to be turned on and the third switch tube Q3 to be turned off, the first loop is connected, and the first loop is forwardly excited through the primary winding Np of the transformer while charging the power supply capacitor Cv.

[0058] When charging the power supply capacitor Cv, the power P in a single cycle of the power supply capacitor Cv is Cv The expression is:

[0059]

[0060] Among them, C Cv is the capacitance of the power supply capacitor Cv, V Cv1 The voltage at the end of charging of the power supply capacitor Cv; V Cv0 The voltage at the start of charging of the power supply capacitor Cv; f sw is the switching frequency of the switching power supply.

[0061] The excitation energy generated by transformer T1 when charging the power supply capacitor Cv is converted into a single cycle power P L1 The expression is:

[0062]

[0063] Among them, L p is the inductance of the primary winding Np of the transformer, I L1 I is the current flowing through the primary winding Np when the power supply capacitor Cv is charged; L0 The current flowing through the primary winding Np when the power supply capacitor Cv starts to charge; fsw is the switching frequency of the switching power supply.

[0064] Case 2: The voltage across the power supply capacitor Cv is greater than or equal to the second undervoltage value V L2 When , the control device U1 controls the first switch tube Q1 to be turned on, the second switch tube Q2 to be turned on and the third switch tube Q3 to be turned off, the second loop is connected, and the second loop is forwardly excited only through the primary winding Np of the transformer T1.

[0065] The first undervoltage value V L1 and the second undervoltage value V L2 There is a voltage difference between them, and V L1 <V L2 The purpose of setting the hysteresis is to ensure that situation 1 and situation 2 will not switch repeatedly.

[0066] (2) Transformer demagnetization stage

[0067] The control device U1 controls the second switch tube Q2 to turn off. After the second switch tube Q2 is turned off, the transformer T1 begins to demagnetize. After the clamping capacitor C1 stores a small amount of energy, the remaining excitation energy is transferred to the secondary side to supply power to the load.

[0068] Regardless of the operating conditions in the transformer excitation stage of the above-mentioned conventional control method, the excitation energy generated by the transformer through the first circuit or the excitation energy generated by the second circuit is transferred to the secondary side and provided to the load end.

[0069] When the load of the switching power supply is large, the output power Po of the switching power supply is large. By adjusting the excitation energy generated by the second circuit through closed-loop control, the output voltage can be stabilized at the rated voltage value under different load conditions. When the load of the switching power supply is large, P L1 It will be much smaller than Po, so it will not cause abnormal operation of the switching power supply.

[0070] However, when the load is extremely small (i.e., the load is light or no-load, referred to as light no-load), the output power Po is very small (usually within 20mW). If the transformer excitation stage is the above situation, P L1 It must be less than or equal to Po to prevent the output voltage from floating abnormally high. The above formula can be deduced as follows: When the switching power supply is unloaded, it operates in DCM mode. L1 =0A. In this case, the control device U1 needs to achieve extremely low loss to meet the requirements. When the control device U1 consumes a lot of power, P L1 Will be much larger than Po, P L1 It will be transferred to the secondary side, resulting in excessive output energy and abnormally high output voltage.

[0071] There are two existing solutions to the above problem. One is to add a dummy load, which will increase the light no-load power consumption; the other is to reduce the power consumption of the control device U1, which will make chip design more difficult.

[0072] Therefore, the current switching power supply without auxiliary winding power supply schemes all directly draw power linearly from the input filter capacitor Cin or the drain of the second switch tube Q2 when the load is light. Although these schemes solve the abnormal high output voltage fluctuation under light no-load conditions, since the power consumption of linear power is equal to the input voltage multiplied by the power consumption current of the control device U1, the power consumption of linear power will be very large, resulting in large light no-load losses, which has obvious defects.

[0073] It should be noted that when the load is extremely small, if the transformer excitation stage is the above-mentioned situation one, although the technical personnel in this field have noticed that this causes the output voltage of the switching power supply to fluctuate abnormally, it is difficult to think of a more complete solution. In the end, a linear power supply method is used to solve the problem, while minimizing the chip power consumption as much as possible. The inventor of this application has conducted in-depth research and produced the embodiment solution proposed in the following content.

[0074] First embodiment

[0075] See also Figure 3 , which is targeted by the present invention Figure 2 The flowchart of the control method embodiment provided by the switching power supply shown includes the following steps:

[0076] S101, obtaining a first signal representing the current output power of the switching power supply;

[0077] S102, obtaining a second signal representing a current voltage value across the power supply capacitor;

[0078] S103, comparing the first signal with a first set value to generate a third signal;

[0079] This step is configured to determine the load condition of the switching power supply, thereby identifying whether the switching power supply is in a light no-load state. A person skilled in the art may set the first set value based on actual conditions. For example, a first signal value corresponding to 10% of the rated output power of the switching power supply may be used as the first set value. A person skilled in the art may analyze and calculate the specific design based on actual conditions. The key point is to ensure that the output voltage does not fluctuate excessively, and this embodiment does not impose any limitation thereto.

[0080] S104, comparing the second signal with a second set value to generate a fourth signal;

[0081] The purpose of this step is to determine whether the power supply capacitor Cv is in an undervoltage state, so as to ensure that the power supply capacitor Cv, as an auxiliary power supply device, can provide energy for the normal operation of the active devices inside the switching power supply. The second set value can be set by technicians in this field according to actual conditions. For example, 11V can be used as the second set value. The specific design method can be analyzed and calculated by technicians in this field according to actual conditions. The key point is to ensure that the control device U1 does not trigger the undervoltage protection, which is not limited in this embodiment.

[0082] S104, controlling the on and off of the first switching tube, the second switching tube, and the third switching tube according to the third signal and the fourth signal, so that the switching power supply operates in different operating processes, wherein when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary during the operation of the switching power supply.

[0083] The on / off control of the first, second, and third switching tubes may be performed based on the third and fourth signals. Alternatively, the on / off control of the first, second, and third switching tubes may be performed by directly using the third and fourth signals. Alternatively, the on / off control of the first, second, and third switching tubes may be performed by preprocessing the third and fourth signals (such as amplification, attenuation, isolation, etc.). The on / off control of the first, second, and third switching tubes may be performed by using the preprocessed signals. The specific implementation method may be independently selected by technicians in this field according to the actual application scenario, and this embodiment does not limit this.

[0084] In this step, when the first signal is less than the first set value and the second signal is less than the second set value, it means that the switching power supply is in a light no-load state and the power supply capacitor Cv is in an undervoltage state. At this time, the secondary side has sufficient energy and the power supply capacitor Cv needs to be replenished. In order to prevent the excitation energy generated in the process of replenishing the power supply capacitor Cv from causing the output voltage to fluctuate, it is necessary to prevent the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer from being transferred to the secondary during the operation of the switching power supply, so that the output voltage is stabilized at the rated value.

[0085] The order of steps S101 and S102 is irrelevant and they are performed simultaneously and in real time. After the corresponding signals are obtained in the two steps, they are compared in steps S103 and S104 respectively. The order of steps S103 and S104 is also irrelevant and they are performed simultaneously and in real time. The comparison results obtained in steps S103 and S104 serve as the basis for executing step S105, which controls the on and off of the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3, so that the switching power supply operates in different working processes.

[0086] In the control method of this embodiment, when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer are not transferred to the secondary circuit during the operation of the switching power supply. That is, when the switching power supply is lightly no-loaded and the power supply capacitor is undervoltage, the transformer energy is not transferred to the secondary side. This solves the problem of high power consumption of the primary side control device of the existing winding-free power supply solution, which leads to high output voltage fluctuation and low no-load power consumption. When the switching power supply allows the use of a control device with higher power consumption, the design difficulty of some complex control devices can be greatly reduced. In addition, the power supply solution without auxiliary windings can reduce the cost of the switching power supply and improve the integration of the switching power supply.

[0087] Furthermore, when the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply, the demagnetization energy is first transferred to the clamping capacitor C1, and then the transformer is reversely excited through the clamping capacitor C1. The reverse demagnetization energy is finally transferred to the input terminal Vin of the switching power supply.

[0088] The reverse demagnetization energy is transferred to the switching power supply input terminal Vin and can be stored as follows: Figure 2 The input filter capacitor Cin shown ultimately achieves the goal of preventing energy from being transferred to the secondary-side circuit, thus stabilizing the output voltage at the rated value.

[0089] Furthermore, when the first signal is less than the first set value and the second signal is less than the second set value, the switching power supply operation process includes:

[0090] In the first stage, the first switch Q1 is turned off, the second switch Q2 is turned on, and the third switch Q3 is turned off. The primary winding Np of the transformer is forward excited through the first circuit, and the power supply capacitor Cv is charged at the same time.

[0091] In the second stage, the second switch Q2 is turned off, the primary winding Np of the transformer begins to demagnetize, and the body diode of the third switch Q3 is turned on first. Then the third switch Q3 is turned on, and the demagnetization energy of the primary winding Np of the transformer is transferred to the clamping capacitor Cv through the third loop. The current in the primary winding Np of the transformer gradually decreases to zero.

[0092] In the third stage, the third switch Q3 is continuously turned on for the first duration. The clamping capacitor reversely excites the primary winding Np of the transformer. The current in the primary winding Np of the transformer increases in the reverse direction from zero. Part of the energy of the clamping capacitor Cv is transferred to the primary winding Np of the transformer through the third loop.

[0093] The first duration is mainly used to control the voltage across the clamping capacitor C1 to always be less than the product of the turns ratio of the transformer and the output voltage of the switching power supply, to ensure that the demagnetization energy is not transferred to the secondary side. The specific design method can be analyzed and calculated by technicians in this field according to actual conditions, and this embodiment does not limit this.

[0094] In stage 4, the third switch tube Q3 is turned off, and the primary winding Np of the transformer begins to be reverse demagnetized. The body diode of the first switch tube Q1 and the body diode of the second switch tube Q2 are turned on, and the reverse demagnetization energy of the primary winding Np of the transformer is transferred to the switching power supply input terminal Vin through the second loop.

[0095] Furthermore, in the third stage, when part of the energy of the clamping capacitor C1 is transferred to the primary winding of the transformer, the voltage V across the clamping capacitor C1 is controlled. C1 Less than the product of the transformer's turns ratio (primary winding turns Np / secondary winding turns Ns) and the switching power supply output voltage Vo, that is, V C1 <(Np / Ns)·Vo.

[0096] The purpose of controlling VC1<(Np / Ns)·Vo is that when the rectifier switch tube of the secondary side circuit adopts diode rectification ( Figure 2 The diode Do in the circuit is the rectifier switch tube). In stage three, the voltage across the primary winding of the transformer is the voltage across the clamping capacitor VC1. The voltage induced in the secondary winding Ns of the transformer is VNs = (VC1 / Np)·Ns. Therefore, VNs < Vo. This ensures that the diode in the secondary circuit is cut off due to the reverse bias voltage, and energy is not transferred to the secondary circuit.

[0097] Furthermore, in stage three, the voltage across the clamping capacitor is controlled to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply by controlling the first duration.

[0098] Second embodiment

[0099] See also Figure 4 , which is targeted by the present invention Figure 2 The schematic diagram of an embodiment of a control device provided by the switching power supply shown includes:

[0100] A first acquiring unit 101 is configured to acquire a first signal representing a current output power of the switching power supply;

[0101] For example, the first signal representing the current output power of the switching power supply can be obtained through the feedback signal, the output current signal, and the input current signal. The specific method of obtaining the first signal is not limited in this embodiment.

[0102] The second acquiring unit 102 is configured to acquire a second signal representing a current voltage value across the power supply capacitor;

[0103] In actual application, for example, the second signal representing the current voltage value across the power supply capacitor can be obtained through an amplification circuit. This embodiment does not limit how to obtain the second signal.

[0104] A first comparing unit 103 is configured to compare the first signal with a first set value to generate a third signal;

[0105] In actual application, for example, the first comparison unit may be designed by using a comparator and necessary auxiliary components, and this embodiment does not limit the specific design method.

[0106] A second comparing unit 104 is configured to compare the second signal with a second set value to generate a fourth signal;

[0107] In actual application, for example, the second comparison unit may be designed by using a comparator and necessary auxiliary components, and this embodiment does not limit the specific design method.

[0108] The processing unit 105 is configured to control the on and off states of the first switching tube, the second switching tube, and the third switching tube based on the third signal and the fourth signal, so that the switching power supply operates in different operating processes. When the first signal is less than a first set value and the second signal is less than a second set value, the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary circuit during the operation of the switching power supply.

[0109] In actual application, for example, a special controller, a single-chip microcomputer (MCU) or a digital signal processor (DSP) can be designed to control the on and off of the first switch tube, the second switch tube and the third switch tube according to the third signal and the fourth signal. The specific implementation method of this embodiment does not limit this.

[0110] In the control device of this embodiment, when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer are not transferred to the secondary circuit during the operation of the switching power supply. That is, when the switching power supply is lightly no-loaded and the power supply capacitor is undervoltage, the transformer energy is not transferred to the secondary side. This solves the problem of high power consumption of the primary side control device of the existing winding-free power supply solution, which leads to high output voltage fluctuation and low no-load power consumption. When the switching power supply allows the use of a control device with higher power consumption, the design difficulty of the control device can be greatly reduced for some complex control devices. In addition, the power supply solution without auxiliary winding can reduce the cost of the switching power supply and improve the integration of the switching power supply.

[0111] Furthermore, the processing unit 105 ensures that when the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply, the demagnetization energy is first transferred to the clamping capacitor C1, and then the transformer is reversely excited through the clamping capacitor C1, and the reverse demagnetization energy is finally transferred to the switching power supply input terminal Vin.

[0112] Furthermore, the processing unit 105 is configured such that when the first signal is less than a first set value and the second signal is less than a second set value, the switching power supply operation process includes:

[0113] In the first stage, the first switch Q1 is turned off, the second switch Q2 is turned on, and the third switch Q3 is turned off. The primary winding Np of the transformer is forward excited through the first circuit, and the power supply capacitor Cv is charged at the same time.

[0114] In the second stage, the second switch Q2 is turned off, the primary winding Np of the transformer begins to demagnetize, and the body diode of the third switch Q3 is turned on first. Then the third switch Q3 is turned on, and the demagnetization energy of the primary winding Np of the transformer is transferred to the clamping capacitor Cv through the third loop. The current in the primary winding Np of the transformer gradually decreases to zero.

[0115] In the third stage, the third switch Q3 is continuously turned on for the first duration. The clamping capacitor reversely excites the primary winding Np of the transformer. The current in the primary winding Np of the transformer increases in the reverse direction from zero. Part of the energy of the clamping capacitor Cv is transferred to the primary winding Np of the transformer through the third loop.

[0116] In stage 4, the third switch tube Q3 is turned off, and the primary winding Np of the transformer begins to be reverse demagnetized. The body diode of the first switch tube Q1 and the body diode of the second switch tube Q2 are turned on, and the reverse demagnetization energy of the primary winding Np of the transformer is transferred to the switching power supply input terminal Vin through the second loop.

[0117] Furthermore, the control device further includes a first control unit for controlling the voltage V across the clamping capacitor C1 when part of the energy of the clamping capacitor C1 is transferred to the primary winding of the transformer in the third stage. C1 Smaller than the product of the transformer's turns ratio and the switching power supply's output voltage Vo.

[0118] Furthermore, the control device also includes a second control unit, configured to control the voltage across the clamping capacitor to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply by controlling the first time duration.

[0119] In this embodiment, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiment described above is merely illustrative. For example, the division of the above-mentioned units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, and can be electrical or other forms.

[0120] In this embodiment, the units described above as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0121] In addition, the functional units in each implementation of this embodiment may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0122] If the above-mentioned integrated unit in this embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, 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. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the above-mentioned methods of each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0123] Third embodiment

[0124] A third embodiment of the present invention provides a computer-readable storage medium, which includes a stored program. The program executes the method of any specific implementation method of the first embodiment.

[0125] Fourth embodiment

[0126] A fourth embodiment of the present invention provides a processor for running a program, wherein the program executes the method of any specific implementation method of the first embodiment when running.

[0127] Fifth embodiment

[0128] The fifth embodiment of the present invention provides a switching power supply. Figure 2 ,include:

[0129] A primary-side circuit, a transformer T1, and a secondary-side circuit E1. The primary-side circuit includes: a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, a first diode D1, a power supply capacitor Cv, a clamping capacitor C1, a primary winding Np of the transformer, and a control device U1. The switching power supply positive input terminal Vin, the primary winding Np of the transformer, the second switching tube Q2, the anode of the first diode D1, the cathode of the first diode D1, the power supply capacitor Cv, and the switching power supply input ground terminal GND are sequentially connected to form a first loop. The switching power supply positive input terminal Vin, the primary winding Np of the transformer, the second switching tube Q2, the first switching tube Q1, and the switching power supply input ground terminal GND are sequentially connected to form a second loop. One end of the clamping capacitor C1, the primary winding Np of the transformer, the third switching tube Q3, and the other end of the clamping capacitor C1 are sequentially connected to form a third loop. The control device U1 controls the conduction and shutdown of the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3.

[0130] and a control device U1.

[0131] The control device U1 is the control device of any specific implementation manner in the second embodiment.

[0132] Figure 5 The following is a working waveform diagram of the switching power supply provided in this embodiment, where the meanings of the waveform symbols are as follows:

[0133] Vo: output voltage waveform;

[0134] V Ns : Voltage waveform across the secondary winding Ns of the transformer;

[0135] Vin: input capacitor Cin voltage waveform;

[0136] V C1 : Clamp capacitor C1 voltage waveform;

[0137] Vcc: voltage waveform of power supply capacitor Cv;

[0138] IL: transformer primary winding Np current waveform;

[0139] SW3: driving waveform of the third switch Q3, which is turned on when high level and turned off when low level;

[0140] SW2: driving waveform of the second switch tube Q2, which is turned on when high level and turned off when low level;

[0141] SW1: driving waveform of the first switch tube Q1, which is turned on when the voltage is high and turned off when the voltage is low.

[0142] Combine Figure 2 The circuit shown in FIG. 1 analyzes the working process of the switching power supply when it is lightly no-loaded (i.e., when the first signal is less than the first set value) as follows:

[0143] State 1: When the power supply capacitor Cv drops to the undervoltage V L When the second signal is less than the second set value, the first switch tube Q1 is turned off, the second switch tube Q2 is turned on, and the third switch tube Q3 is turned off. The first loop consisting of the positive input terminal Vin of the switching power supply, the primary winding Np of the transformer, the second switch tube Q2, the first diode D1, the power supply capacitor Cv and the input ground terminal GND of the switching power supply is connected, and the voltage across the primary winding Np of the transformer is Vin-V Cv (Ignore the conduction voltage drop of the switching tube), the primary winding Np of the transformer begins to be forwardly excited, and the power supply capacitor Cv is charged at the same time. The current IL flowing through the primary winding Np of the transformer and the power supply capacitor Cv gradually increases, the primary winding Np of the transformer is excited, and the voltage across the power supply capacitor Cv also gradually increases.

[0144] State 2: When the voltage of the power supply capacitor Cv rises to the clamping voltage V H After that, the first switch tube Q1 is turned on, the second switch tube Q2 is turned off, and the third switch tube Q3 remains off, stopping charging the power supply capacitor Cv. After the primary winding Np of the transformer is magnetized, it begins to demagnetize, controlling the voltage on the clamping capacitor C1. (The purpose is to prevent energy from being transferred to the secondary side), so that the energy stored in the primary winding Np of the transformer only charges the clamping capacitor C1. The third switch tube body diode is turned on first, and after a dead time, the third switch tube Q3 is turned on. The energy stored in the primary winding Np of the transformer is transferred to the clamping capacitor C1. As the current IL decreases, the clamping capacitor voltage V C1 Increase; where: V L1 <V H <V L2 , the control device U1 clamps the voltage V H To control the charging time of the power supply capacitor Cv.

[0145] State 3: When the current IL decreases to 0A, the clamp capacitor voltage V C1When the maximum voltage value is reached, all the energy of the transformer primary winding Np is transferred to the clamping capacitor C1. During the entire process of energy transfer, the voltage V on the clamping capacitor C1 is ensured by controlling the conduction time of the third switch tube Q3. C1 Always less than Therefore, the secondary side diode Do is insufficiently conductive, so energy is not transferred to the secondary side.

[0146] State 4: Since the third switch Q3 remains on, the voltage of the clamping capacitor C1 is applied to the transformer T1, causing the transformer primary winding Np to start reverse excitation, the reverse direction of the current IL increases, and the clamping capacitor voltage V C1 The voltage gradually decreases, and when the set on-time of the third switch tube Q3 is reached, the third switch tube Q3 is turned off. Part of the energy stored in the clamping capacitor C1 is transferred to the primary winding Np of the transformer again.

[0147] State 5: When the third switch tube Q3 is turned off, the first switch tube Q1 is turned on, and the reverse current IL causes the body diode of the second switch tube Q2 to be turned on. Therefore, the energy stored in the primary winding Np of the transformer charges the input capacitor Cin, so that the energy stored in the primary winding Np of the transformer is finally transferred to the input terminal Vin of the switching power supply, that is, Figure 2 The input filter capacitor Cin.

[0148] The above analysis of the operating process shows that, in the switching power supply of this embodiment, when the first signal is less than the first set value and the second signal is less than the second set value, neither the demagnetization energy nor the reverse demagnetization energy of the primary winding of the transformer is transferred to the secondary circuit during operation of the switching power supply. That is, when the switching power supply is lightly no-loaded and the power supply capacitor is undervoltage, the transformer energy is not transferred to the secondary side. This solves the problem of high power consumption of the primary control device of the existing winding-free power supply switching power supply, resulting in high output voltage fluctuation and low no-load power consumption. Moreover, when the switching power supply allows the use of a control device with higher power consumption, the design difficulty of some complex control devices can be greatly reduced. In addition, the power supply solution without auxiliary windings can reduce the cost of the switching power supply and improve the integration of the switching power supply.

[0149] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention. Persons skilled in the art will appreciate that equivalent power supplies, improvements, and modifications may be made without departing from the spirit and scope of the present invention. These equivalent power supplies, improvements, and modifications should also be considered within the scope of protection of the present invention. Examples will not be used here for further elaboration. The scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A method for controlling a switching power supply, the switching power supply comprising a primary-side circuit, a transformer, and a secondary-side circuit, wherein the primary-side circuit comprises: A first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, the primary winding of the transformer and a control device; The positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and the input ground terminal of the switching power supply are connected in sequence to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are connected in sequence to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are connected in sequence to form a third loop, and the control device controls the conduction and shutdown of the first switching tube, the second switching tube, and the third switching tube; characterized in that the control method comprises the following steps: Acquire a first signal representing the current output power of the switching power supply; Acquire a second signal representing a current voltage value across the power supply capacitor; comparing the first signal with a first set value to generate a third signal; comparing the second signal with a second set value to generate a fourth signal; Based on the third signal and the fourth signal, the first switching tube, the second switching tube, and the third switching tube are controlled to be turned on and off, so that the switching power supply operates in different operating processes. Specifically, when the first signal is less than the first set value and the second signal is less than the second set value, the demagnetization energy and the reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply.

2. The method for controlling a switching power supply according to claim 1, wherein: When the demagnetization energy and reverse demagnetization energy of the primary winding of the transformer are not transmitted to the secondary side circuit during the operation of the switching power supply, the demagnetization energy is first transferred to the clamping capacitor, and then the transformer is reversely excited through the clamping capacitor. The reverse demagnetization energy is finally transferred to the input end of the switching power supply.

3. The method for controlling a switching power supply according to claim 1 or 2, wherein: When the first signal is less than the first set value and the second signal is less than the second set value, the switching power supply operation process includes: In the first stage, the first switch is turned off, the second switch is turned on, and the third switch is turned off. The primary winding of the transformer is forward excited through the first circuit and the power supply capacitor is charged at the same time. In the second stage, the second switch is turned off, the primary winding of the transformer begins to be demagnetized, the body diode of the third switch is turned on first, and then the third switch is turned on. The demagnetization energy of the primary winding of the transformer is transferred to the clamping capacitor through the third loop, and the current in the primary winding of the transformer gradually decreases to zero. In stage three, the third switching transistor is continuously turned on for a first period of time, the clamping capacitor reversely excites the primary winding of the transformer, the current in the primary winding of the transformer increases in the reverse direction from zero, and part of the energy of the clamping capacitor is transferred to the primary winding of the transformer through the third loop; In stage 4, the third switch tube is turned off, the primary winding of the transformer begins to be reversely demagnetized, the body diode of the first switch tube and the body diode of the second switch tube are turned on, and the reverse demagnetization energy of the primary winding of the transformer is transferred to the input end of the switching power supply through the second loop.

4. The method for controlling a switching power supply according to claim 3, wherein: In the third stage, when part of the energy in the clamping capacitor is transferred to the primary winding of the transformer, the voltage across the clamping capacitor is controlled to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply.

5. The method for controlling a switching power supply according to claim 4, wherein: In the third stage, the voltage across the clamping capacitor is controlled to be smaller than the product of the turns ratio of the transformer and the output voltage of the switching power supply by controlling the first duration.

6. A control device for a switching power supply, the switching power supply comprising a primary side circuit, a transformer, and a secondary side circuit, the primary side circuit comprising: A first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, the primary winding of the transformer and a control device; The positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and the input ground terminal of the switching power supply are connected in sequence to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are connected in sequence to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are connected in sequence to form a third loop, and the control device controls the conduction and shutdown of the first switching tube, the second switching tube, and the third switching tube; characterized in that the control device includes: A first acquiring unit, configured to acquire a first signal representing a current output power of the switching power supply; A second acquiring unit, configured to acquire a second signal representing a current voltage value across the power supply capacitor; a first comparing unit, configured to compare the first signal with a first set value to generate a third signal; a second comparing unit, configured to compare the second signal with a second set value to generate a fourth signal; a processing unit, configured to control the on and off states of the first switching tube, the second switching tube, and the third switching tube based on the third signal and the fourth signal, so that the switching power supply operates in different operating processes, wherein when the first signal is less than the first set value and the second signal is less than the second set value, neither the demagnetization energy nor the reverse demagnetization energy of the primary winding of the transformer is transferred to the secondary-side circuit during the operation of the switching power supply.

7. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored program, wherein the program executes the method according to any one of claims 1 to 5.

8. A processor, characterized in that: The processor is configured to run a program, wherein the program executes the method according to any one of claims 1 to 5 when running.

9. A switching power supply, characterized in that: include: A primary-side circuit, a transformer, and a secondary-side circuit, wherein the primary-side circuit includes: a first switching tube, a second switching tube, a third switching tube, a first diode, a power supply capacitor, a clamping capacitor, the primary winding of the transformer, and a control device; The positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the anode of the first diode, the cathode of the first diode, the power supply capacitor, and the input ground terminal of the switching power supply are connected in sequence to form a first loop; the positive input terminal of the switching power supply, the primary winding of the transformer, the second switching tube, the first switching tube, and the input ground terminal of the switching power supply are connected in sequence to form a second loop; one end of the clamping capacitor, the primary winding of the transformer, the third switching tube, and the other end of the clamping capacitor are connected in sequence to form a third loop, and the control device controls the conduction and shutdown of the first switching tube, the second switching tube, and the third switching tube; And the control device according to claim 6.

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