Flyback switching power supply

Abstract

The application relates to a flyback switching power supply, the number of secondary windings of the transformer of the flyback switching power supply is the same as the number of required unidirectional conducting devices, each secondary winding is connected in series with a unidirectional conducting device and then connected in parallel to the positive pole of the power supply output, so that the current flowing through the unidirectional conducting device is limited by the connected secondary winding and is not affected by the forward conducting voltage drop, meanwhile, the current backflow between the secondary windings of the transformer in the blocking dead time is blocked, the circuit loss is reduced, and the problem of large temperature difference when the flyback switching power supply uses multiple unidirectional conducting devices is solved.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a flyback switching power supply. Background Technology

[0002] For high-power flyback power supplies, the secondary output current is large, often requiring two or even three diodes in parallel to meet the current requirements. In most existing circuits, the common approach is to connect two secondary diodes in parallel, followed by an RC (resistor and capacitor) snubber circuit to absorb the spikes caused by leakage inductance. However, due to inherent differences in individual diodes, their forward voltage drops are not identical, and diodes are positive temperature coefficient devices, meaning their forward voltage drop decreases with increasing temperature. This leads to a vicious cycle in practical applications: a diode with a smaller forward voltage drop will draw a larger current when connected in parallel with another diode. The diode with the larger current draws a higher temperature, further reducing its forward voltage drop. Therefore, parallel diode connections inevitably fall into a vicious cycle, resulting in a significant temperature difference between the two diodes. Furthermore, poor heat dissipation can cause the diodes to overheat and burn out.

[0003] In addition, when the two secondary windings of a transformer are connected in parallel and / or the two coils of a winding are connected in parallel and then connected to a secondary diode, during the dead time after energy discharge, current backflow occurs between the two parallel secondary windings and / or between the two coils of a winding, increasing circuit losses. Utility Model Content

[0004] The purpose of this application is to provide a flyback switching power supply, which aims to solve the problems of large temperature difference of parallel diodes and large circuit loss in the output circuit of traditional flyback power supplies.

[0005] In a first aspect, embodiments of this application provide a flyback switching power supply, comprising an input section, a transformer, and an output section connected in sequence. The transformer includes a primary winding, a magnetic core, and multiple secondary windings. The primary winding, the magnetic core, and the secondary windings are all wound on the magnetic core. The output section includes multiple unidirectional conducting devices. The first end of each secondary winding is grounded, and the second end of each secondary winding is connected to the input end of each unidirectional conducting device in a one-to-one correspondence. The input ends of each unidirectional conducting device are not shared, and the output ends of each unidirectional conducting device are shared and connected to the output end of the output section.

[0006] In some embodiments, a plurality of absorption circuits are further included, each absorption circuit being connected in parallel with each of the unidirectional conducting devices, and the absorption circuits being used to absorb peak currents.

[0007] In some embodiments, the absorption circuit includes a first resistor and a first capacitor, which are connected in series and then in parallel with the unidirectional conducting device.

[0008] In some embodiments, there are n secondary windings and n unidirectional conducting devices, and each secondary winding includes m secondary sub-windings. The i-th secondary sub-winding of each secondary winding is arranged in the same layer. When m≥2, different secondary sub-windings in the same secondary winding are stacked.

[0009] The first end of each of the secondary sub-windings is grounded, and the second end of the secondary sub-winding in the k-th secondary winding is connected to the input end of the k-th unidirectional conducting device, where n≥2, m≥1, and n and m are positive integers, i∈[1,m], k∈[1,n].

[0010] In some embodiments, the plurality of secondary windings include a primary winding and a secondary winding, the primary winding including a primary sub-winding, the secondary winding including a secondary sub-winding, and the primary sub-winding and the secondary sub-winding being wound in the same layer.

[0011] In some embodiments, the plurality of secondary windings include a first secondary winding and a second secondary winding, the plurality of unidirectional conducting devices include a first unidirectional conducting device and a second unidirectional conducting device, the first secondary winding includes two stacked first secondary sub-windings, and the second secondary winding includes two stacked second secondary sub-windings.

[0012] The first end of each of the first stage sub-windings and the first end of each of the second stage sub-windings are grounded. The second end of each of the first stage sub-windings is connected to the input terminal of the first unidirectional conducting device. The second end of each of the second stage sub-windings is connected to the input terminal of the second unidirectional conducting device. The output terminal of the first unidirectional conducting device and the output terminal of the second unidirectional conducting device are connected to the output terminal of the output section.

[0013] In some embodiments, the first-stage sub-winding and the second-stage sub-winding arranged in the same layer are wound in a double-wire parallel winding manner.

[0014] In some embodiments, a plurality of secondary windings are stacked sequentially, with the first end of each secondary winding grounded and the second end of each secondary winding connected to the input terminal of the corresponding unidirectional conducting device.

[0015] In some embodiments, each of the secondary windings includes n secondary sub-windings wound in parallel on the same layer, the first end of each of the secondary sub-windings is grounded, and the second end of each of the secondary sub-windings is connected to the input terminal of the corresponding unidirectional conducting device, wherein n≥2 and n is a positive integer.

[0016] In some embodiments, the primary winding includes a first primary sub-winding and a second primary sub-winding stacked together, wherein the first primary winding and the second primary winding are located between the first primary sub-winding and the second primary sub-winding.

[0017] In some embodiments, the primary winding includes n+1 primary sub-windings stacked sequentially, and each secondary sub-winding arranged on the same layer is located between two adjacent primary sub-windings.

[0018] In some embodiments, the secondary windings arranged in the same layer have the same wire diameter and number of turns.

[0019] The beneficial effects of this application embodiment compared with related technologies are as follows: the number of secondary windings of the transformer in the flyback switching power supply is the same as the number of unidirectional conducting devices required. Each secondary winding is connected in series with a unidirectional conducting device and then connected in parallel to the positive terminal of the power output. This makes the current flowing through the unidirectional conducting device limited by the connected secondary winding and not affected by the forward conduction voltage drop. At the same time, it blocks the current return between the secondary windings of the transformer during the dead time, reducing circuit losses. Attached Figure Description

[0020] Figure 1 This is a circuit diagram of a flyback switching power supply in the prior art;

[0021] Figure 2 This is a circuit diagram of the output section of another flyback switching power supply in the prior art;

[0022] Figure 3 This is a typical temperature characteristic curve of a diode;

[0023] Figure 4 for Figure 1 or Figure 2 The waveform diagram of the current recirculation between the windings in a flyback switching power supply;

[0024] Figure 5 A waveform diagram of the current recirculation between windings in a flyback switching power supply provided in an embodiment of this application;

[0025] Figure 6 A circuit diagram of a flyback switching power supply provided in an embodiment of this application;

[0026] Figure 7A circuit diagram of the output section of a flyback switching power supply provided in an embodiment of this application;

[0027] Figure 8 A schematic diagram of the cross-sectional structure of the transformer of a flyback switching power supply provided in an embodiment of this application;

[0028] Figure 9 A circuit diagram of the output section of a flyback switching power supply provided in an embodiment of this application;

[0029] Figure 10 A schematic diagram of the cross-sectional structure of the transformer of a flyback switching power supply provided in an embodiment of this application;

[0030] Figure 11 A circuit diagram of the output section of a flyback switching power supply provided in an embodiment of this application;

[0031] Figure 12 A schematic diagram of the cross-sectional structure of the transformer of a flyback switching power supply provided in an embodiment of this application;

[0032] Figure 13 The current waveform flowing through the rectifier diode when using two different transformers in a flyback switching power supply provided in an embodiment of this application;

[0033] Figure 14 The current waveforms flowing through the diodes of a flyback switching power supply provided in an embodiment of this application are shown when the diodes are connected in parallel with the same and different absorption circuits.

[0034] Figure 15 The output section of the flyback switching power supply provided in one embodiment of this application uses the current waveforms of three rectifier diodes. Detailed Implementation

[0035] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0036] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0037] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0039] like Figure 1 As shown, conventional flyback switching power supplies have a relatively large secondary output current, often requiring two or even three rectifier diodes D1 and D2 connected in parallel to meet the output current requirements. For most existing circuits, the common solution is to connect the two rectifier diodes D1 and D2 on the output side in parallel, and then connect an RC snubber circuit in parallel to absorb the spikes generated by leakage inductance. Figure 1 The secondary winding Ns1 of the transformer shown is composed of two secondary sub-windings (i.e. coils) Ns1-1 and Ns1-2 connected in parallel. It can also be represented as two secondary windings Ns1-1 and Ns1-2 connected in parallel. Figure 2 The transformer shown has two secondary windings Ns1 and Ns2 with a four-band / five-band structure. Secondary winding Ns1 has two secondary sub-windings Ns1-1 and Ns1-2 connected in parallel, and secondary winding Ns2 has two secondary sub-windings Ns2-1 and Ns2-2 connected in parallel. After the two secondary windings Ns1 and Ns2 are connected in parallel, they are connected to the anodes of two diodes D1 and D2.

[0040] For example, if an ultrafast recovery diode or a Schottky diode is used for rectification on the output side, the forward voltage drop V will vary due to individual differences between ultrafast recovery diodes, Schottky diodes, and other devices. F They will not be exactly the same, and diode devices are positive temperature coefficient devices (typical temperature characteristic curves are shown in Figure 1). Figure 3 As shown in the figure, the higher the temperature, the higher the forward conduction voltage drop V. F The smaller the value, the lower the forward voltage drop V. This results in a lower forward voltage drop V0 during actual use. F When the smaller rectifier diode D1 is connected in parallel with another rectifier diode D2, a larger current flows through it. The rectifier diode D1, with its larger current flow, experiences a higher temperature and a lower forward voltage drop V. FThe temperature will decrease further, so the parallel connection of rectifier diodes D1 and D2 will inevitably fall into a vicious cycle, resulting in a large temperature difference between the two rectifier diodes D1 and D2.

[0041] Additionally, when the transformer uses a double-wire parallel winding (such as...) Figure 1 (as shown) or four- or five-sided sandwich wrapping method (such as...) Figure 2 As shown, the common practice is to connect the two secondary windings Ns1-1 and Ns1-2 of the transformer in parallel, or connect the two secondary windings Ns1 and Ns2 in parallel and then connect them to the secondary diodes D1 and D2. In this case, during the dead time after energy dissipation, current flows back between the secondary windings, such as... Figure 4 As shown in the diagram, the yellow waveform represents the voltage of the main MOSFET Q1 in the flyback switching power supply, while the blue and red waveforms represent the currents in the two secondary windings Ns1 and Ns2. As can be seen from the red arrow, current backflow occurs between the windings when entering the dead zone, increasing circuit losses.

[0042] In some application scenarios, the technical solutions of this application connect each secondary winding of the transformer (or each secondary sub-winding of a secondary winding) to a separate rectifier diode. Furthermore, the transformer design ensures that the inductance and leakage inductance of each secondary winding are similar, thereby maximizing the balance of current flowing through the rectifier diodes. Additionally, the reverse cutoff function of the rectifier diodes eliminates backflow in the secondary windings of the transformer during the dead zone, improving overall energy efficiency. Figure 5 As shown, according to the technical solution of this application embodiment, the dead zone at the red arrow will not experience the aforementioned phenomenon of current backflow between secondary windings.

[0043] Specifically, please refer to Figure 6 One embodiment of this application provides a flyback switching power supply, including an input section, a transformer, and an output section connected in sequence. The transformer includes a primary winding, a magnetic core, and multiple secondary windings, with both the primary and secondary windings wound on the magnetic core. Figure 6 In this embodiment, the primary winding includes a first primary sub-winding Np1, a second primary sub-winding Np2, and a primary auxiliary winding Np4, and the secondary winding includes a first primary winding Ns1 and a second secondary winding Ns2. This is used as an example for illustration. In other embodiments, the number of primary and secondary windings of the transformer can be different.

[0044] The output section includes multiple unidirectional conducting devices D1 and D2. The first end of each secondary winding Ns1 and Ns2 is used for grounding. The second end of each secondary winding Ns1 and Ns2 is connected to the input end of each unidirectional conducting device D1 and D2 respectively. The input ends of each unidirectional conducting device D1 and D2 are not shared. The output ends of each unidirectional conducting device D1 and D2 are shared with the output end of the output section.

[0045] For example, a unidirectional conducting device can be a semiconductor transistor, such as a diode or triode. Figure 6 For example, the transformer includes a primary winding Ns1 and a secondary winding Ns2. The non-corresponding terminals of the primary winding Ns1 and the secondary winding Ns2 are grounded. The corresponding terminal of the primary winding Ns1 is connected to the anode of diode D1, and the corresponding terminal of the secondary winding Ns2 is connected to the anode of diode D2. The cathodes of diodes D1 and D2 are connected to the positive terminal V+ of the output section. That is, each secondary winding Ns1 and Ns2 is connected in series with each unidirectional conducting device D1 and D2, and then connected in parallel to the output terminal of the output section.

[0046] When designing a transformer, for example, two secondary windings Ns1 and Ns2 are arranged in the same layer, with the two secondary windings Ns1 and Ns2 located between the two primary windings (or primary sub-windings) Np1 and Np2. This ensures that the inductance of the two secondary windings Ns1 and Ns2 is the same or similar, and the leakage inductance is also close. This makes the energy of each secondary winding Ns1 and Ns2 as equal as possible during transformer operation, and the current flowing through the unidirectional conducting devices D1 and D2 also tends to be consistent. This makes the current of the unidirectional conducting devices D1 and D2 unaffected by their forward conduction voltage drop, improving the temperature difference caused by the different forward conduction voltage drops of diodes, and the problem of diodes easily overheating and burning out under poor heat dissipation conditions. At the same time, the secondary windings Ns1 and Ns2 are not directly connected in parallel. The unidirectional conducting devices D1 and D2 connected to them can block the backflow of current between the secondary windings Ns1 and Ns2 of the transformer, reducing circuit losses.

[0047] The input section of the flyback switching power supply includes a DC input circuit 11, a startup circuit R1, a main MOSFET Q1, and a PWM control chip U1. The DC input circuit 11 is connected to the drain of the main MOSFET Q1 via the primary windings Np1 and Np2 of the transformer. The source of the main MOSFET Q1 is connected to the CS (current sampling) pin of the PWM control chip U1 and grounded through a sampling resistor R2. The GATE pin of the PWM control chip U1 is connected to the gate of the main MOSFET Q1. The primary auxiliary winding Np4 and the startup circuit R1 are connected to the VDD (power supply) pin of the PWM control chip U1. The startup circuit R1 is connected to the DC input circuit 11 and typically includes a current-limiting resistor. Additionally, the flyback switching power supply generally includes a voltage detection circuit 12. The output voltage of its detection output section is input to the FB (feedback) pin of the PWM control chip U1 via an optocoupler U2. The circuit structure of the voltage detection circuit 12 can be found in [reference needed]. Figure 6Example. It is understood that the DC input circuit 11 may include a rectifier bridge and a filter capacitor for connecting AC voltage; the DC input circuit 11 may also be disconnected for connecting DC power. The output section typically also includes a filter capacitor C1, which is connected between the positive and negative terminals of the output section. It is understood that the above is merely a brief description of the input and output sections of a flyback switching power supply in one specific embodiment, and is exemplary in illustrating the technical solution of this application, not intended to limit it. Those skilled in the art should understand that the input and output sections of the flyback switching power supply can also be substituted with other equivalent embodiments.

[0048] In some embodiments, each secondary winding is wound with two or more wires in the same layer, such a structure allows the magnetic flux induced in two or more secondary windings to be similar.

[0049] Please see Figure 7 In some embodiments, multiple absorption circuits 13 are also included, each absorption circuit 13 being connected in parallel with each unidirectional conducting device D1, D2 in a one-to-one correspondence. The absorption circuit 13 is used to absorb the spike current generated by leakage inductance.

[0050] In some embodiments, the absorption circuit includes a first resistor R3 and a first capacitor C2, which are connected in series and then in parallel with unidirectional conducting devices D1 / D2. For example, the parameters of each absorption circuit 13 are identical to avoid generating different current spikes.

[0051] Please see Figures 7 to 10 In some embodiments, there are n secondary windings and n unidirectional conducting devices. Each secondary winding includes m secondary sub-windings. The i-th secondary sub-winding of each secondary winding is arranged in the same layer. When m≥2, different secondary sub-windings in the same secondary winding are stacked. The first end of each secondary sub-winding is grounded. The second end of the secondary sub-winding in the k-th secondary winding is connected to the input end of the k-th unidirectional conducting device. Here, n≥2, m≥1, and n and m are positive integers, i∈[1,m], k∈[1,n].

[0052] In this context, "winding (or sub-winding) in the same layer" means that the winding is located between two adjacent layers of insulating tape. The winding can be wound in one (or two) or more layers between two adjacent layers of insulating tape. "Winding stacking" means that two or more windings (or sub-windings) are arranged in different layers, with at least one layer of insulating tape separating the two or more windings.

[0053] In some embodiments, when n=2 and m=1, the transformer constitutes a sandwich-structure transformer. See also... Figure 8The primary winding includes a first primary sub-winding Np1 and a second primary sub-winding Np2 stacked together. The first primary winding Ns1 and the second primary winding Ns2 are located between the first primary sub-winding Np1 and the second primary sub-winding Np2. The sandwich structure transformer is: primary (sub) winding - secondary winding - primary (sub) winding stacked in sequence.

[0054] Please see Figure 7 and Figure 8 In some embodiments, multiple secondary windings include a primary winding Ns1 and a secondary winding Ns2. The primary winding Ns1 includes a primary sub-winding, and the secondary winding Ns2 includes a secondary sub-winding. The primary sub-winding and the secondary sub-winding are wound in the same layer, and their magnetic inductance and leakage inductance are similar. This makes the energy of the primary winding Ns1 and the secondary winding Ns2 as equal as possible during the operation of the transformer, and the current flowing through the unidirectional conducting devices D1 and D2 also tends to be consistent.

[0055] Figure 8 In this embodiment, the primary winding also includes a primary auxiliary winding Np4 (terminal X-terminal Y), where "·" represents the first primary winding Ns1 and "×" represents the second primary winding Ns2, both wound with two wires in parallel. The first primary sub-winding Np1 (terminal A-terminal B) has a two-layer structure, and after being wound close to the magnetic core 100, it is covered with a first double-layer adhesive tape 101 for insulation. Then, the first primary winding Ns1 (terminal F-terminal G) and the second primary winding Ns2 (terminal H-terminal I) are wound on the first double-layer adhesive tape 101 in the same layer with two wires in parallel. After the first primary winding Ns1 and the second primary winding Ns2 are wound, they are covered with a second double-layer adhesive tape 102, and then the second primary sub-winding Np2 (terminal B-terminal C) is wound. The second primary sub-winding Np2 has one layer, and after being wound, it is covered with a third double-layer adhesive tape 103, and then the primary auxiliary winding Np4 is wound. Figure 8 It can be seen more clearly that the first end F of the first winding Ns1 and the first end H of the second winding Ns2 are grounded. The second end G of the first winding Ns1 and the second end I of the second winding Ns2 are connected in series with the input ends of the two unidirectional conducting devices D1 and D2, and then connected in parallel to the positive output terminal V+.

[0056] Figure 8 In the example, the winding directions of the first primary sub-winding Np1, the second primary sub-winding Np2, the primary auxiliary winding Np4, the first primary winding Ns1, and the second primary winding Ns2 are consistent. In some embodiments, the wire diameter and number of turns of the first primary winding Ns1 and the second primary winding Ns2 are the same, further making the energy of the first primary winding Ns1 and the second primary winding Ns2 as equal as possible, and the current flowing through the unidirectional conducting devices D1 and D2 also tend to be consistent.

[0057] In some embodiments, when n=2 and m=2, the transformer constitutes a four-sided or five-sided transformer. The primary winding includes n+1 primary sub-windings stacked sequentially, with each secondary sub-winding on the same layer located between two adjacent primary sub-windings. See also... Figure 10 The primary winding includes the first primary sub-winding Np1 (terminal A-terminal B), the second primary sub-winding Np2 (terminal B-terminal C), the third primary sub-winding Np3 (terminal C-terminal D), and the primary auxiliary winding Np4 (terminal X-terminal Y), forming a five-phase transformer.

[0058] Please see Figure 9 and Figure 10 In some embodiments, the secondary winding includes a primary winding Ns1 and a secondary winding Ns2, and the unidirectional conducting device includes a first unidirectional conducting device D1 and a second unidirectional conducting device D2. The primary winding Ns1 includes two stacked primary sub-windings Ns1-1 (terminal F-terminal G) and Ns1-2 (terminal H-terminal I), and the secondary winding Ns2 includes two stacked secondary sub-windings Ns2-1 (terminal J-terminal K) and Ns2-2 (terminal L-terminal M). The first terminals F and H of each primary stage sub-winding Ns1-1 and Ns1-2 and the first terminals J and L of each secondary stage sub-winding Ns2-1 and Ns2-2 are all grounded. The second terminals G and I of each primary stage sub-winding Ns1-1 and Ns1-2 are connected to the input terminal of the first unidirectional conducting device D1. The second terminals K and M of each secondary stage sub-winding Ns2-1 and Ns2-2 are connected to the input terminal of the second unidirectional conducting device D2. The output terminal of the first unidirectional conducting device D1 and the output terminal of the second unidirectional conducting device D2 are connected to the output terminal of the output section.

[0059] Figure 10In this embodiment, "·" represents the first primary winding Ns1, and "×" represents the second primary winding Ns2; both are wound in parallel with double wires on the same layer. The first primary sub-winding Np1 has a single-layer structure and is covered with a first double-layer adhesive tape 101 after being wound close to the magnetic core 100 for insulation. Then, the first primary sub-winding Ns1-1 and the second primary sub-winding Ns2-1 are wound on the first double-layer adhesive tape 101 using a parallel double-wire winding method, forming a two-layer structure. After the first primary sub-winding Ns1-1 and the second primary sub-winding Ns2-1 are wound, they are covered with a second double-layer adhesive tape 102, and then the second primary sub-winding Np2 is wound. The second primary sub-winding Np2 is a single layer. After winding, it is covered with a third double-layer tape 103. Then, the first primary sub-winding Ns1-2 and the second primary sub-winding Ns2-2 are wound using a double-wire parallel winding method. The first primary sub-winding Ns1-2 and the second primary sub-winding Ns2-2 are two-layer structures. After winding, they are covered with a fourth double-layer tape 104. Then, the third primary sub-winding Np3 is wound. The third primary sub-winding Np3 is a single layer. After winding, it is covered with a fifth double-layer tape 105. Finally, the primary auxiliary winding Np4 is wound. Figure 10 It can be seen more clearly that the first terminal F of the first stage sub-winding Ns1-1 and the first terminal H of the first stage sub-winding Ns1-2 are grounded. The second terminal G of the first stage sub-winding Ns1-1 and the second terminal I of the first stage sub-winding Ns1-2 are connected together and then connected to the input terminal of the first unidirectional conducting device D1. The first terminal J of the second stage sub-winding Ns2-1 and the first terminal L of the second stage sub-winding Ns2-2 are grounded. The second terminal K of the second stage sub-winding Ns2-1 and the second terminal M of the second stage sub-winding Ns2-2 are connected together and then connected to the input terminal of the second unidirectional conducting device D2. The output terminals of the unidirectional conducting devices D1 and D2 are connected to the positive terminal V+ of the output terminal.

[0060] Figure 10 In the example, the winding directions of the first primary sub-winding Np1, the second primary sub-winding Np2, the third primary sub-winding Np3, the primary auxiliary winding Np4, the first primary winding Ns1, and the second primary winding Ns2 are consistent. In some embodiments, the wire diameter and number of turns of the first primary winding Ns1 and the second primary winding N2 are the same, further making the energy of the first primary winding Ns1 and the second primary winding Ns2 as equal as possible, and the current flowing through the unidirectional conducting devices D1 and D2 also tend to be consistent.

[0061] Please see Figure 11 and Figure 12 In some embodiments, multiple secondary windings Ns1 and Ns2 are stacked sequentially, with the first terminals F, H, L, and J of each secondary winding Ns1 and Ns2 grounded, and the second terminals I, G, M, and K of each secondary winding Ns1 and Ns2 connected to the input terminals of the corresponding unidirectional conducting devices D1 / D2. Figure 12 In the example, the secondary winding includes the first primary winding Ns1 and the second primary winding Ns2, and the primary winding includes the first primary sub-winding Np1 (terminal A-terminal B), the second primary sub-winding Np2 (terminal B-terminal C), the third primary sub-winding Np3 (terminal C-terminal D), and the primary auxiliary winding Np4 (terminal X-terminal Y). The first primary sub-winding Np1, the first primary winding Ns1, the second primary sub-winding Np2, the second primary winding Ns2, the third primary sub-winding Np3, and the primary auxiliary winding Np4 are stacked sequentially to form a five-layer transformer. It can be understood that removing the third primary sub-winding Np3 from the five-layer transformer results in a four-layer transformer.

[0062] Specifically, the second ends I and G of the two sub-windings of the first primary winding Ns1 are connected to the input terminal of the first unidirectional conducting device D1, and the second ends M and K of the two sub-windings of the second primary winding Ns2 are connected to the input terminal of the first unidirectional conducting device D2.

[0063] In some embodiments, each secondary winding includes n parallel-wound secondary sub-windings, the first end of each secondary sub-winding is grounded, and the second end of each secondary sub-winding is connected to the input terminal of the corresponding unidirectional conducting device, where n≥2 and n is a positive integer. Figure 12 In the example, the first stage winding Ns1 includes two wires of the same layer wound between the first double-layer tape 101 and the second double-layer tape 102, and two sub-windings Ns1-1 (terminal F-terminal G) and Ns1-2 (terminal H-terminal I). The second stage winding Ns2 includes two wires of the same layer wound between the second double-layer tape 102 and the third double-layer tape 103, and two sub-windings Ns2-1 (terminal J-terminal K) and Ns2-2 (terminal L-terminal M). The first terminals F and H of each primary stage sub-winding Ns1-1 and Ns1-2, and the first terminals J and L of each secondary stage sub-winding Ns2-1 and Ns2-2 are all grounded. The second terminals G and I of each primary stage sub-winding Ns1-1 and Ns1-2 are connected to the input terminal of the first unidirectional conducting device D1. The second terminals K and M of each secondary stage sub-winding Ns2-1 and Ns2-2 are connected to the input terminal of the second unidirectional conducting device D2. The output terminals of the first and second unidirectional conducting devices D1 and D2 are connected to the positive output terminal V+.

[0064] Figure 12In the example, "×" and "·" represent different secondary sub-windings within the same primary winding. The winding directions of the first primary sub-winding Np1, the second primary sub-winding Np2, the third primary sub-winding Np3, the primary auxiliary winding Np4, the first primary winding Ns1, and the second secondary winding Ns2 are consistent. In some embodiments, the wire diameter and number of turns of the first primary winding Ns1 and the second secondary winding N2 may be different, further ensuring that the energy of the first primary winding Ns1 and the second secondary winding Ns2 is as equal as possible, and that the current flowing through the unidirectional conducting devices D1 and D2 also tends to be consistent.

[0065] In addition to using double-wire parallel winding, the windings or sub-windings can also be arranged in the same layer by dividing each sub-layer between two adjacent insulating tape layers into multiple parts corresponding to the number of windings (or sub-windings). Each part is wound with different windings (or sub-windings). These multiple parts can be staggered (one example is double-wire parallel winding, with the two parts represented by "×" and "·" respectively), or they can be symmetrically distributed, that is, "×" and "·" are concentrated on both sides of each sub-layer.

[0066] To verify the feasibility of the embodiments of this application, four transformer schemes (T1, T2, T3, and T4) were wound for comparison, and their primary and secondary winding inductance and leakage inductance were compared respectively. The transformer winding structures of T1, T2, T3, and T4 are as follows (primary windings are Np1, Np2, and Np3; secondary windings are Ns1 and Ns2):

[0067]

[0068]

[0069] The table below shows the primary and secondary inductance and leakage inductance of four transformers: T1, T2, T3, and T4 (for T1, Ns1 and Ns2 refer to one of the two parallel windings of the Ns winding):

[0070]

[0071] T1 has a standard sandwich structure, and the secondary windings Ns1 and Ns2 are wound with two wires in parallel. (Reference) Figure 8 T2 differs from T1 in that the secondary windings Ns1 and Ns2 are changed from being wound in parallel with two wires to being wound with a single wire in two layers. (Refer to...) Figure 8 The winding method of Np1 is used to further increase the difference between the secondary windings Ns1 and Ns2. T3 is a four-sided sandwich structure, and T4 is a five-sided sandwich structure. The winding methods used for the secondary windings Ns1 and Ns2 of T3 and T4 are referenced. Figure 12 .

[0072] By comparing the transformer inductance and leakage inductance parameters, it can be found that: the inductance and leakage inductance of the secondary windings Ns1 and Ns2 of T1 are relatively balanced; the inductance of the secondary winding Ns2 of T2 is slightly greater than that of the secondary winding Ns1; the inductance of the secondary winding Ns2 of T3 and T4 is significantly greater than that of the secondary winding Ns1, and the leakage inductance of the secondary winding Ns2 of T3 is significantly greater than that of Ns1.

[0073] In conventional circuits (see attached) Figure 1 , 2 When testing with two rectifier diodes D1 and D2 connected in parallel (rectifier diodes are used as one embodiment of unidirectional conducting devices, and the same reference numerals are used in subsequent test / experiment descriptions for unidirectional conducting devices), the temperatures of the two rectifier diodes corresponding to T1, T2, T3, and T4 are as follows:

[0074]

[0075] Arrange T1 and T2 according to Figure 6 Connect the two rectifier diodes D1 and D2 in the following manner, and T3 and T4 in accordance with... Figure 11 Two rectifier diodes D1 and D2 are connected in the same configuration. Secondary windings Ns1 and Ns2 are connected in series with the two rectifier diodes D1 and D2 respectively, and then connected in parallel with the same absorption circuit 13. The peak current, average current, and temperature rise data for each rectifier diode D1 and D2 are as follows:

[0076]

[0077] It can be observed that the inductance and leakage inductance of the secondary windings Ns1 and Ns2 of transformer T1 are more balanced. Using the circuit design of this embodiment, the current and temperature differences between the two rectifier diodes D1 and D2 are also minimal. For transformers T2, T3, and T4, due to the larger differences in the inductance and leakage inductance of the secondary windings Ns1 and Ns2, the current and temperature differences between the two rectifier diodes D1 and D2 are also larger. However, compared to conventional circuits ( Figure 1 and Figure 2 The circuit structure has been optimized, and the temperatures of the two rectifier diodes D1 and D2 have been improved.

[0078] In the above experiment, Figure 12 The illustrated quad transformer T3 / quintet transformer T4, if the two secondary windings Ns1 and Ns2 use the same wire diameter and number of turns, will result in significant differences in the inductance and leakage inductance of the secondary windings Ns1 and Ns2, leading to uneven current and temperature distribution in the two rectifier diodes D1 and D2. Therefore, generally speaking... Figure 12The secondary windings Ns1 and Ns2 of the illustrated quadrilateral transformer T3 / quintet transformer T4 can be configured with different wire diameters and number of turns, thereby reducing the current and temperature differences between the two rectifier diodes D1 and D2. Alternatively, to address the problem of significant temperature differences between the two rectifier diodes D1 and D2 due to unbalanced parameters in the secondary windings Ns1 and Ns2, the following method is proposed... Figure 10 The diagram shows that when a four- or five-layer transformer is used in this alternating parallel configuration, the parameters of the two secondary windings, Ns1 and Ns2, will be more balanced.

[0079] The table below shows Figure 10 The diagram shows the primary and secondary inductance and leakage inductance of a four-sided / five-sided transformer structure. Figure 10 The four-sided / five-sided transformers shown are denoted by T3* and T4* respectively:

[0080]

[0081] According to T3* and T4* Figure 9 and Figure 10 Two rectifier diodes D1 and D2 are connected in the same configuration. The peak current, average current, and temperature rise data of the two rectifier diodes D1 and D2 are as follows:

[0082]

[0083] As can be seen from the table above, after adopting the four-sided / five-sided transformer structure shown in Figure 10, the inductance difference between the secondary windings Ns1 and Ns2 of T3* and T4* is significantly reduced, and the average current and temperature difference of the two rectifier diodes D1 and D2 are also significantly reduced.

[0084] Figure 13 Showing Figure 10 The structure of the five Meiji transformer T4* and Figure 12 The difference in current waveforms between the two rectifier diodes D1 and D2 when the transformer T4 is connected to two rectifier diodes D1 and D2 is shown. Green and red represent the currents flowing through the two rectifier diodes D1 and D2, respectively. It can be seen that due to the difference in inductance between the secondary windings Ns1 and Ns2, their induced electromotive forces differ, resulting in different discharge sequences and a large difference in the average current flowing through the two rectifier diodes D1 and D2. Using... Figure 10 The T4* structure of the five Meiji transformers ensures balanced transformer parameters and prevents this problem.

[0085] For each absorption circuit 13, the parameters are exactly the same.

[0086] exist Figure 1 , Figure 2In the circuit shown, if the forward voltage drops of the two rectifier diodes D1 and D2 are similar, the current spike flowing through the diode closer to the capacitor in the snubber circuit 13 will be greater than that of the other rectifier diode, resulting in a temperature difference between the two rectifier diodes. In an extreme case, when one rectifier diode is connected in parallel with the snubber circuit 13 and the other rectifier diode is not connected in parallel, all the energy discharged by the capacitor in the snubber circuit 13 will flow out through one rectifier diode.

[0087] The table below compares the performance of three types of transformers: T1, T3*, and T4*. Figure 8 and Figure 10 Based on the connection of rectifier diodes D1 and D2, when only one rectifier diode is connected in parallel with the absorption circuit 13, the current flowing through the two rectifier diodes D1 and D2 and their temperature are as follows:

[0088]

[0089] Figure 14 The T3* transformer was demonstrated in Figure 10 Based on the connection of rectifier diodes D1 to D2, the difference in current waveforms is observed when there is only one rectifier diode connected in parallel with the snubber circuit 13 (i.e., different RC circuits) and when both rectifier diodes D1 and D2 are connected in parallel with RC snubber circuits (i.e., the same RC circuit). Figure 14 In the upper part, green represents the current of the rectifier diode in the parallel absorption circuit 13, and red represents the current of the rectifier diode without the parallel absorption circuit 13. It can be seen that the current peak and average value are significantly different under different RC parameters.

[0090] The technical solution of this application is also applicable to situations where multiple rectifier diodes are connected in parallel in the output section. From the previous tests, it can be concluded that when the secondary winding adopts a multi-wire parallel winding structure (T1, T3*, T4*), the secondary winding parameters of the transformer are more balanced, and the temperature difference between the two rectifier diodes D1 and D2 is minimal. Therefore, taking the use of three rectifier diodes in the output section as an example, tests were conducted on a 107-watt power supply board, with transformer T5 wound. The winding method of transformer T5 is referenced... Figure 8 The difference is that the secondary winding consists of three secondary sub-windings with the same or similar parameters wound in parallel, which are connected in series with three diodes and then in parallel between the positive terminal V+ of the output and ground. The specific parameters are as follows:

[0091]

[0092] Among them, N1, N3, and N4 are the primary windings, equivalent to Figure 8 Np1, Np2, Np4, and N2 are secondary windings, equivalent to Figure 8 Ns1.

[0093] The table below shows the primary and secondary inductance and leakage inductance of transformer T5:

[0094]

[0095] Among them, N2-1, N2-2, and N2-3 are the three wires of the secondary winding, that is, the three secondary sub-windings.

[0096] Comparative testing was conducted in a conventional circuit (i.e., rectifier diodes were used in accordance with...). Figure 1 (Connection method) and temperature rise of the rectifier diode in this embodiment:

[0097] D1 Temperature / °C D2 Temperature / ℃ D3 temperature / ℃ Maximum temperature difference / °C conventional circuits 124.4 124.8 116.2 8.6 This embodiment 116.9 117.9 112.9 5

[0098] Among them, D1, D2, and D3 are three rectifier diodes.

[0099] It can be observed that when using a conventional circuit, the temperature difference between the rectifier diodes is large, and the temperatures of rectifier diodes D1 and D2 both exceed the temperature limit of 120°C. After using the circuit of the embodiment, the temperatures of the three rectifier diodes D1, D2, and D3 are optimized, and the temperature difference is reduced. Figure 15 In this embodiment, the current of the three rectifier diodes reaches a balanced state.

[0100] As can be seen from the above embodiments, using the circuit structure and transformer structure of the embodiments of this application, the output section of the flyback switching power supply, with multiple rectifier diodes connected in parallel, makes the current flowing through each rectifier diode more balanced, thereby reducing the temperature difference.

[0101] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A flyback switching power supply, comprising an input section, a transformer, and an output section connected in sequence, characterized in that, The transformer includes a primary winding, a magnetic core, and multiple secondary windings. The primary winding and the secondary windings are both wound on the magnetic core. The output section includes multiple unidirectional conducting devices. The first end of each secondary winding is grounded, and the second end of each secondary winding is connected to the input end of each unidirectional conducting device. The input ends of each unidirectional conducting device are not shared, and the output ends of each unidirectional conducting device are shared and connected to the output end of the output section.

2. The flyback switching power supply as described in claim 1, characterized in that, It also includes multiple absorption circuits, each of which is connected in parallel to each of the unidirectional conducting devices, and the absorption circuits are used to absorb peak currents.

3. The flyback switching power supply as described in claim 2, characterized in that, The absorption circuit includes a first resistor and a first capacitor, which are connected in series and then in parallel with the unidirectional conducting device.

4. The flyback switching power supply as described in claim 1, characterized in that, There are n secondary windings and n unidirectional conducting devices. Each secondary winding includes m secondary sub-windings. The i-th secondary sub-winding of each secondary winding is arranged in the same layer. When m≥2, different secondary sub-windings in the same secondary winding are stacked. The first end of each of the secondary sub-windings is grounded, and the second end of the secondary sub-winding in the k-th secondary winding is connected to the input end of the k-th unidirectional conducting device, where n≥2, m≥1, and n and m are positive integers, i∈[1,m], k∈[1,n].

5. The flyback switching power supply as described in claim 4, characterized in that, The plurality of secondary windings include a primary winding and a secondary winding. The primary winding includes a primary sub-winding, and the secondary winding includes a secondary sub-winding. The primary sub-winding and the secondary sub-winding are wound in the same layer.

6. The flyback switching power supply as described in claim 4, characterized in that, The plurality of secondary windings include a first secondary winding and a second secondary winding, and the plurality of unidirectional conducting devices include a first unidirectional conducting device and a second unidirectional conducting device. The first secondary winding includes two stacked first secondary sub-windings, and the second secondary winding includes two stacked second secondary sub-windings. The first end of each of the first stage sub-windings and the first end of each of the second stage sub-windings are grounded. The second end of each of the first stage sub-windings is connected to the input terminal of the first unidirectional conducting device. The second end of each of the second stage sub-windings is connected to the input terminal of the second unidirectional conducting device. The output terminal of the first unidirectional conducting device and the output terminal of the second unidirectional conducting device are connected to the output terminal of the output section.

7. The flyback switching power supply as described in claim 5 or 6, characterized in that, The first-stage sub-winding and the second-stage sub-winding, which are arranged in the same layer, are wound in a double-wire parallel winding manner.

8. The flyback switching power supply as described in claim 1, characterized in that, Multiple secondary windings are stacked sequentially, with the first end of each secondary winding grounded and the second end of each secondary winding connected to the input terminal of the corresponding unidirectional conducting device.

9. The flyback switching power supply as described in claim 8, characterized in that, Each of the secondary windings includes n secondary sub-windings wound in parallel on the same layer. The first end of each of the secondary sub-windings is grounded, and the second end of each of the secondary sub-windings is connected to the input terminal of the corresponding unidirectional conducting device, where n≥2 and n is a positive integer.

10. The flyback switching power supply as described in claim 5, characterized in that, The primary winding includes a first primary sub-winding and a second primary sub-winding stacked together, with the first primary winding and the second primary winding located between the first primary sub-winding and the second primary sub-winding.

11. The flyback switching power supply as described in claim 4 or 9, characterized in that, The primary winding includes n+1 primary sub-windings stacked sequentially, and each secondary sub-winding in the same layer is located between two adjacent primary sub-windings.

12. The flyback switching power supply as described in claim 4 or 9, characterized in that, The secondary windings arranged in the same layer have the same wire diameter and number of turns.

Images