A switching power supply circuit, a power adapter and a charging system

Abstract

The embodiment of the application provides a switching power supply circuit, a power adapter and a charging system, and relates to the technical field of electronics. The switching power supply circuit comprises a first input end, a first output end, a power conversion circuit, a rectifier circuit, a first Y capacitor and a second Y capacitor. The first ends of the two Y capacitors are coupled with the first input end, and the second ends of the two Y capacitors are coupled with the first output end. The capacitance values of the two Y capacitors are adjusted to make the EMI meet the specification requirements. Regardless of the insertion direction of the power adapter, there is a Y capacitor with a leakage current, and the other Y capacitor is bypassed. By reducing the capacitance value of the Y capacitor with the leakage current in the switching power supply circuit, the leakage current of the Y capacitor in the switching power supply circuit is smaller than the leakage current of the Y capacitor in the structure with only one Y capacitor.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a switching power supply circuit, a power adapter, and a charging system. Background Technology

[0002] With the widespread use of electronic devices, charging equipment such as power adapters has become a necessity. Among these, the Y capacitor in the power adapter has always been a key method for reducing electromagnetic interference (EMI). Moreover, as the power of power adapters increases, the importance of Y capacitor solutions becomes increasingly apparent.

[0003] However, while Y capacitors offer benefits in terms of EMI, they also worsen the leakage current of the power adapter. This worsening leakage current can cause a tingling sensation in the user's hand during use, negatively impacting the charging experience. Therefore, how to reduce the leakage current of the power adapter while meeting EMI testing requirements has become a problem that those skilled in the art need to further address. Utility Model Content

[0004] To address the aforementioned issues, this application provides a switching power supply circuit, a power adapter, and a charging system that can meet EMI testing requirements without requiring users to manually perform reverse insertion, thereby reducing power adapter leakage current.

[0005] A first aspect of this application provides a switching power supply circuit. The switching power supply circuit includes a first input terminal, a first output terminal, a power conversion circuit, a rectifier circuit, a first Y capacitor, and a second Y capacitor. The first input terminal includes a first input terminal and a second input terminal. The first output terminal includes a first output terminal and a second output terminal. The power conversion circuit includes an input side and an output side; the input side of the power conversion circuit is correspondingly coupled to the two output terminals of the rectifier circuit, and the output side of the power conversion circuit is correspondingly coupled to the first output terminal and the second output terminal. The rectifier circuit includes two input terminals and two output terminals; the two input terminals are correspondingly coupled to the first input terminal and the second input terminal.

[0006] The first terminal of the first Y capacitor is coupled to the first input terminal, and the second terminal of the first Y capacitor is coupled to the first output terminal. The first terminal of the second Y capacitor is coupled to the second input terminal, and the second terminal of the second Y capacitor is coupled to the first output terminal. In a switching power supply circuit with two Y capacitors, regardless of whether the power adapter is plugged in correctly or incorrectly, one of the first or second Y capacitors will always have its first terminal coupled to the live wire of the AC power supply, while the first terminal of the other Y capacitor will inevitably be coupled to the neutral wire. Therefore, the voltage difference across the Y capacitor whose first terminal is coupled to the neutral wire is nearly 0V, insufficient to drive leakage current; the branch containing this Y capacitor can be considered bypassed. However, the branch containing the Y capacitor whose first terminal is coupled to the live wire has a voltage difference, allowing leakage current to exist. Thus, regardless of whether the power adapter is plugged in correctly or incorrectly, one of the first or second Y capacitors will have leakage current, while the other Y capacitor will not.

[0007] Because the first and second Y capacitors work together to meet the EMI requirements of the power adapter, their capacitance values ​​are smaller than those of the single-Y capacitor architecture in existing technologies. Therefore, the capacitance values ​​of both the first and second Y capacitors are reduced. Furthermore, since capacitance is proportional to leakage current, a decrease in capacitance leads to a decrease in leakage current. In the charging process of this application, one of the first and second Y capacitors experiences leakage current, while the other does not. Therefore, this solution effectively reduces the leakage current of the switching power supply circuit during charging. In summary, regardless of whether the capacitor is plugged in correctly or incorrectly, the leakage current of the switching power supply circuit can be effectively reduced while meeting EMI requirements.

[0008] In some embodiments, the capacitance values ​​of the first Y capacitor and the second Y capacitor are equal. When the power adapter is plugged in either way, one of the first and second Y capacitors will have leakage current, while the other will not. Therefore, when the capacitance values ​​of the first and second Y capacitors are equal, regardless of whether the power adapter is plugged in correctly or incorrectly, the Y capacitors with the same capacitance value will have leakage current. Thus, the improvement effect on leakage current is the same regardless of whether the power adapter is plugged in correctly or incorrectly.

[0009] In some embodiments, the capacitance of the first Y capacitor is smaller than that of the second Y capacitor. When this switching power supply circuit is applied to a power adapter, a marking pattern can be provided on the surface of the power adapter housing to identify the first input terminal, which is coupled to the mains live wire. By setting the capacitance of the Y capacitor coupled to the first input terminal to be smaller, the leakage current of the switching power supply circuit is further reduced.

[0010] In some embodiments, the switching power supply circuit further includes an input filter circuit. The two input terminals of the input filter circuit are coupled to the first input terminal and the second input terminal respectively, and the two output terminals of the input filter circuit are coupled to the two input terminals of the rectifier circuit respectively.

[0011] In some embodiments, the first terminal of the first Y capacitor and the first terminal of the second Y capacitor are coupled to the input filter circuit. For example, the first terminal of the first Y capacitor and the first terminal of the second Y capacitor are coupled to internal terminals of the input filter circuit, or, for example, the first terminal of the first Y capacitor and the first terminal of the second Y capacitor are correspondingly coupled to the two output terminals of the input filter circuit. The presence of X capacitors and common-mode inductors may enable the input filter circuit to effectively suppress EMI interference from the power adapter.

[0012] In some embodiments, the power conversion circuit of the switching power supply circuit includes a transformer and a switching transistor. The transformer includes a primary side and a secondary side, the primary side and the switching transistor are connected in series between the two output terminals of the rectifier circuit, and the secondary side is connected between the first output terminal and the second output terminal. In some embodiments, the second terminals of the first Y capacitor and the second Y capacitor are respectively coupled to the first output terminal and the second output terminal of the first output terminal. The second terminals of the first Y capacitor and the second Y capacitor can be coupled to the two output terminals in various ways to form a variety of optional circuit configurations, thereby making the switching power supply circuit highly flexible and configurable.

[0013] In some embodiments, the switching power supply circuit further includes a third Y capacitor. The first terminal of the third Y capacitor is coupled to one output terminal of the rectifier circuit, and the second terminal of the third Y capacitor is coupled to the first output terminal. This allows for a reduction in the total leakage current in the switching power supply circuit while meeting the EMI requirements of the power adapter by adjusting the sum of the capacitance values ​​of the three Y capacitors. It also makes the capacitance setting of each Y capacitor more flexible.

[0014] A second aspect of this application provides a power adapter. It includes a first housing and a switching power supply circuit, as described in the first aspect and its possible implementations, mounted within the first housing. For example, the capacitance of the first Y capacitor is smaller than that of the second Y capacitor. For example, the surface of the first housing includes a marking pattern for identifying a first input terminal coupled to the mains live wire. By setting the capacitance of the Y capacitor coupled to the first input terminal to be smaller, the leakage current of the switching power supply circuit is further reduced.

[0015] A third aspect of this application provides a charging system including a power adapter and an electronic device. For example, the electronic device includes a second housing with conductive regions. The power adapter is coupled to the electronic device and includes the power adapter described in the second aspect. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a charging system provided in an embodiment of this application; Figure 2 A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 3A A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 3B A schematic diagram of another switching power supply circuit provided in an embodiment of this application; Figure 3C A schematic diagram of yet another switching power supply circuit provided in an embodiment of this application; Figure 4A A schematic diagram of the topology of a switching power supply circuit provided in an embodiment of this application; Figure 4B A schematic diagram of another switching power supply circuit topology provided in an embodiment of this application; Figures 5-7 A schematic diagram of the topology of another switching power supply circuit provided in an embodiment of this application; Figure 8A A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 8B A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 9 This is a schematic diagram of a charging system provided in an embodiment of this application.

[0017] Figure label: 10 - Electronic device; 20 - Power adapter; 21 - Switching power supply circuit; 22 - First housing; 30 - Charging cable; 31 - First plug; 32 - Second plug; 211 - Input filter circuit; 212 - Rectifier circuit; 213 - Power conversion circuit; 214 - Output filter circuit; 215 - First Y capacitor; 216 - Second Y capacitor; Cps - Parasitic capacitance of transformer primary and secondary sides; Cy - Y capacitor; A1 - First input terminal; A2 - Second input terminal; Vbus - First output terminal; SGND - Second output terminal; D1 - Rectifier bridge; Ci - Bus capacitor; Co - Capacitor; Q1 - Switch; T1 - Transformer; I1 - Leakage current of the first Y capacitor Cy1; I2 - Leakage current of the second Y capacitor Cy2; I3 - Leakage current due to parasitic capacitance Cps on the primary and secondary sides of the transformer; CX1 - X capacitor; LF1 - Common mode inductor; cy1 - Capacitance of the first Y capacitor Cy1; cy2 - Capacitance of the second Y capacitor Cy2; CY - Capacitance of the Y capacitor. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "second," "first," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] Furthermore, in the embodiments of this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly based on the orientation of the components in the accompanying drawings.

[0021] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "coupled" should be interpreted broadly. For example, "coupled" can be a fixed coupling, a detachable coupling, or an integral coupling; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "phase coupling" can be a direct electrical coupling or an indirect electrical coupling through an intermediate medium. The term "contact" can be direct contact or indirect contact through an intermediate medium.

[0022] In this embodiment of the application, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0023] Figure 1 This is a schematic diagram of a charging system provided in an embodiment of this application.

[0024] like Figure 1 As shown, an embodiment of this application provides a charging system including a power adapter 20 and an electronic device 10. The power adapter 20 is coupled to the electronic device 10 and is used to charge the electronic device 10. For example, the charging system also includes a charging cable 30, one end of which includes a first plug 31, and the other end of which includes a second plug 32. One end of the charging cable 30 is coupled to the power adapter 20 via the plug 31, and the other end of the charging cable 30 is coupled to the electronic device 10 via the plug 32.

[0025] Electronic devices 10 may include, for example, mobile phones, tablets, laptops, ultra-mobile personal computers (UMPCs), handheld computers, netbooks, personal digital assistants (PDAs), wearable electronic devices, virtual reality devices, and other electronic devices 10 that require external charging. Figure 1 The following illustrations use an electronic device 10, including a smart TV, a mobile phone, and a computer. However, the embodiments of this application do not impose special limitations on the specific form of the electronic device 10. For ease of explanation, the following embodiments all use a mobile phone as an example for illustration.

[0026] In some embodiments, the electronic device 10 includes a second housing, which includes conductive regions. For example, the second housing is a metal housing.

[0027] In some embodiments, the power adapter 20 includes a first housing 22 and a switching power supply circuit 21, the switching power supply circuit 21 being mounted within the housing. For example, the input terminal of the switching power supply circuit 21 is coupled to mains power via a plug disposed on the first housing 22, and the output terminal of the switching power supply circuit 21 is coupled to the electronic device 10 via a plug 32. Furthermore, the switching power supply circuit 21 may, for example, be soldered to a printed circuit board within the first housing 22. Figure 1 (Not shown in the image)

[0028] Figure 1The power adapter 20 shown is only one possible implementation and does not limit the application scenario of the technical solution of this application. For example, the type and specific shape of the plug 32 corresponding to different electronic devices 10 may differ.

[0029] As electronic devices 10 evolve towards higher performance and larger screens, the power demands of the power adapter 20 matched with the electronic devices 10 are constantly increasing, leading to increasingly serious electromagnetic interference (EMI) problems generated by the internal switching power supply circuit 21 of the power adapter 20 during operation. Therefore, solving the EMI problem faced by the power adapter 20 means suppressing the EMI electromagnetic interference of its switching power supply circuit 21. Based on the noise propagation path, EMI mainly includes conducted emission (CE) and radiated emission (RE). CE refers to noise propagating along conductors such as power lines and signal lines, while RE refers to noise propagating through space in the form of electromagnetic waves. Therefore, solving the EMI problem means addressing the CE and RE issues of the switching power supply circuit 21.

[0030] Figure 2 This is a schematic diagram of a switching power supply circuit provided in an embodiment of this application.

[0031] In some embodiments, such as Figure 2 As shown, the switching power supply circuit 21 includes a first input terminal, a first output terminal, an input filter circuit 211, a rectifier circuit 212, a power conversion circuit 213, an output rectifier filter circuit 214, and a Y capacitor Cy.

[0032] The first input terminal includes a first input terminal A1 and a second input terminal A2. The first input terminal is used to receive AC power supplied by the mains. For example, the first input terminal A1 is coupled to the live wire L of the mains, and the second input terminal A2 is coupled to the neutral wire N of the mains.

[0033] The first output terminal includes a first output terminal Vbus and a second output terminal SGND, and the first output terminal is used to charge the electronic device 10. For example, the first output terminal Vbus and the second output terminal SGND are coupled to the electronic device 10.

[0034] The input filter circuit 211 includes two input terminals and two output terminals. The two input terminals are coupled to the first input terminal A1 and the second input terminal A2, respectively, and the two output terminals are coupled to the two input terminals of the rectifier circuit 212, respectively.

[0035] The rectifier circuit 212 includes two input terminals and two output terminals. The two input terminals of the rectifier circuit 212 are coupled to the first input terminal and the second input terminal respectively, converting AC power into smooth DC power, and providing a stable, high-voltage DC operating voltage for the subsequent power conversion circuit 213.

[0036] The power conversion circuit 213 includes an input side and an output side. The rectified high-voltage DC power enters the power conversion circuit 213 through the input side for power conversion, converting the high-voltage DC power into low-voltage AC power, which is then output through the output side of the power conversion circuit 213 and provided to the subsequent output rectifier and filter circuit 214.

[0037] For example, the power conversion circuit 213 includes a transformer T1 and a switching transistor Q1.

[0038] For example, the output rectifier and filter circuit 214 includes a switching device D2 and a capacitor Co. For example, the switching device D2 may be a diode or a field-effect transistor. The figure uses a diode as an example for the switching device D2. This output rectifier and filter circuit 214 converts the low-voltage AC power transmitted from the output side of the power conversion circuit 213 into low-voltage DC power, and then transmits it to the first output terminal to power the electronic device 10.

[0039] For example, the working principle of the power conversion circuit 213 and the output rectifier and filter circuit 214 working together to supply power to the first output terminal is explained. When the switch Q1 is turned on, the high-voltage DC current stores energy in the primary winding of the transformer T1. According to the same-name terminal relationship of the transformer, the switching device D2 in the output rectifier and filter circuit 214 is turned off at this time, and the capacitor Co charges the electronic device 10 coupled to the power adapter 20. When the switch Q1 is turned off, the switching device D2 is turned on, and the energy stored in the transformer T1 is released to charge the electronic device 10 through the secondary winding.

[0040] Since the high-speed switching of the switching transistor Q1 will generate EMI, in order to ensure that the EMI of the power adapter 20 meets the specification requirements, a Y capacitor Cy is usually connected between the first input terminal and the first output terminal of the switching power supply circuit 21.

[0041] For example, the first terminal of the Y capacitor Cy is coupled to the first input terminal A1, and the second terminal of the Y capacitor Cy is coupled to the first output terminal Vbus. The Y capacitor Cy is positioned between the power supply line and ground to filter common-mode noise. The capacitance value of the Y capacitor Cy is denoted as CY.

[0042] By using the Y capacitor Cy to provide a low-impedance return path for EMI common-mode noise, the common-mode noise level of power adapter 20 is significantly reduced. This results in a significant reduction in the noise level of power adapter 20 during CE and RE tests, enabling it to meet EMI requirements.

[0043] However, adding the Y capacitor Cy will increase the leakage current of electronic device 10. For the specific leakage current path, please refer to [link to relevant documentation]. Figure 2 As indicated by the middle arrow, after the power adapter 20 is coupled to the electronic device 10, leakage current flows to the electronic device 10 and is transmitted to the user through the conductive area of ​​the second housing in the electronic device 10. When the user touches the conductive area of ​​the second housing, they will feel a tingling sensation in their hand due to the leakage current, reducing the user's experience.

[0044] The larger the capacitance value of the Y capacitor (Cy), the smaller its impedance, and the better its effect on improving EMI common-mode noise. According to the leakage current calculation formula: I = 2πfcU, where f is the frequency of the AC mains, U is the input mains voltage, and c is the capacitance value where leakage current exists. (Reference) Figure 2 As shown by the arrow path, the value of 'c' is related to the capacitance value CY of the Y capacitor Cy and the capacitance value cps of the parasitic capacitance Cps on the primary and secondary sides of the transformer. Therefore, the larger the capacitance value of the Y capacitor Cy, the larger the value of 'c', and the greater the leakage current, resulting in a stronger tingling sensation in the user's hand. While choosing a Y capacitor Cy with a smaller capacitance value reduces the leakage current, it fails to meet EMI requirements.

[0045] In addition, the value of 'c' is also related to the orientation of the power adapter 20. Figure 2 Based on the architecture shown, the value of c will differ when the first input terminal A1 is coupled to the live wire L, and the magnitude of the leakage current will also differ when the first input terminal A1 is coupled to the neutral wire N. Therefore, the user experience will differ depending on the plugging configuration of the power adapter 20.

[0046] To more clearly illustrate the relationship between the selection of the Y capacitor value and EMI benefits and leakage current, this embodiment, while controlling the leakage current to avoid excessive levels and meeting the EMI requirements of the power adapter 20, uses a 110pF Y capacitor Cy and a planar transformer with a parasitic capacitance Cps on the primary and secondary sides of the transformer (cps) of approximately 70pF as examples. In subsequent embodiments, the Y capacitor value that meets the EMI requirements of the power adapter 20 will be referred to as the target Y capacitor value CY.

[0047] For example, such as Figure 2The diagram shows the power adapter 20 in the correct plug-in position. In this case, the first input terminal A1 of the power adapter 20 is coupled to the mains power line L, and the first end of the Y capacitor Cy is coupled to the first input terminal of the power adapter 20, i.e., the first end of the Y capacitor Cy is coupled to the mains power line L. The second end of the Y capacitor Cy is coupled to the first output terminal, which is coupled to the second housing of the electronic device 10, and then connected to ground via the user through the second housing. At this time, there is a voltage difference between the first and second ends of the Y capacitor Cy, and the Y capacitor Cy is connected to the leakage current loop. In this case, the value c in the leakage current calculation formula is the sum of the parasitic capacitance Cps of the transformer's primary and secondary sides and the capacitance value of the Y capacitor Cy. Taking an input AC mains voltage of 240V as an example, according to the leakage current calculation formula, the total leakage current generated by the internal switching power supply circuit 21 of the power adapter 20 is approximately 14uA. This leakage current causes some sensitive users to experience a tingling sensation in their hands when using the power adapter 20 to charge the electronic device 10, reducing the user's charging experience.

[0048] For example, when the power adapter 20 is plugged in reverse, i.e., the first input terminal A1 of the power adapter 20 is coupled to the neutral line N of the mains, and the first end of the Y capacitor Cy is coupled to the first input terminal of the power adapter 20, i.e., the first end of the Y capacitor Cy is coupled to the neutral line N of the mains. The second end of the Y capacitor Cy is coupled to the first output terminal, and the first output terminal is coupled to the second housing of the electronic device 10, which is connected to ground through the user via the second housing. At this time, since the voltage difference across the Y capacitor Cy is almost zero, it is insufficient to drive leakage current through. Therefore, the Y capacitor Cy is bypassed by the leakage current loop. There is leakage current in the parasitic capacitance Cps of the transformer primary and secondary sides in the switching power supply circuit 21. In the leakage current calculation formula, c is the capacitance of the parasitic capacitance Cps of the transformer primary and secondary sides, which is 70pF. The total leakage current generated by the switching power supply circuit 21 inside the power adapter 20 is approximately 5uA.

[0049] According to embodiments of this application, in order to meet EMI requirements, in Figure 2 Based on the architecture shown, to control leakage current and avoid excessive leakage while meeting the EMI requirements of power adapter 20, a 110pF Y capacitor Cy and a planar transformer T1 with a parasitic capacitance Cps and a capacitance cps of approximately 70pF are used. When power adapter 20 is plugged in correctly, i.e., the first input terminal is coupled to the AC power live wire L, the total leakage current is approximately 14uA, which may cause some sensitive users to experience a noticeable tingling sensation in their hands during charging. When power adapter 20 is plugged in reverse, i.e., the first input terminal is coupled to the AC power neutral wire N, the total leakage current is approximately 5uA, which significantly reduces the tingling sensation in the hands of some sensitive users during charging.

[0050] However, when users actually use the power adapter 20, they cannot distinguish between the correct and reverse plugging to avoid large leakage circuits. Therefore, when users use the power adapter 20 to charge electronic devices 10, the numbness in their hands still exists.

[0051] Therefore, how to meet EMI testing requirements without requiring users to distinguish between positive and negative plugs, while reducing the leakage current of the power adapter 20, has become a problem that needs to be further solved by those skilled in the art.

[0052] Figure 3A A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 3B A schematic diagram of another switching power supply circuit provided in an embodiment of this application; Figure 3C This is a schematic diagram of a switching power supply circuit provided for an embodiment of this application.

[0053] Based on this, embodiments of this application provide a switching power supply circuit 21, such as... Figure 3A As shown, the switching power supply circuit 21 includes a first input terminal, a first output terminal, a rectifier circuit 212, a power conversion circuit 213, a first Y capacitor 215, and a second Y capacitor 216.

[0054] The first input terminal includes a first input terminal A1 and a second input terminal A2, and is used to receive alternating current supplied by mains power. For example, one of the first input terminal A1 and the second input terminal A2 is coupled to the live wire L of the mains power, and the other is coupled to the neutral wire N of the mains power. For instance, when the power adapter 20 is plugged in correctly, the first input terminal A1 is coupled to the live wire L of the mains power, and the second input terminal A2 is coupled to the neutral wire N of the mains power. Alternatively, for example, when the power adapter 20 is plugged in incorrectly, the first input terminal A1 is coupled to the neutral wire N of the mains power, and the second input terminal A2 is coupled to the live wire L of the mains power.

[0055] The first output terminal includes a first output terminal Vbus and a second output terminal SGND, and the first output terminal is used to charge the electronic device 10. For example, the first output terminal Vbus and the second output terminal SGND are coupled to the electronic device 10.

[0056] The rectifier circuit 212 includes two input terminals and two output terminals. The two input terminals of the rectifier circuit 212 are coupled to the first input terminal A1 and the second input terminal A2 respectively. The rectifier circuit 212 is used to convert the AC power supplied by the mains into smooth DC power, providing a stable and high-voltage DC operating voltage for the subsequent power conversion circuit 213.

[0057] The power conversion circuit 213 includes an input side and an output side. The high-voltage DC power rectified by the rectifier circuit 212 enters the power conversion circuit 213 through the input side for power conversion. The power conversion circuit 213 converts the high-voltage DC power into low-voltage AC power, which is then output through the output side of the power conversion circuit 213 and provided to the output terminal of the switching power supply circuit 21. For example, the input side of the power conversion circuit 213 is coupled to the two output terminals of the rectifier circuit 212, and the output side of the power conversion circuit 213 is coupled to the first input terminal A1 and the second input terminal A2.

[0058] The first Y capacitor 215 includes a first terminal and a second terminal. The first terminal of the first Y capacitor 215 is coupled to the first input terminal A1, and the second terminal of the first Y capacitor 215 is coupled to the first output terminal. For example, Figure 3A As shown, the second end of the first Y capacitor 215 is coupled to the first output terminal Vbus of the first output terminal.

[0059] The second Y capacitor 216 includes a first terminal and a second terminal. The first terminal of the second Y capacitor 216 is coupled to the second input terminal A2, and the second terminal of the second Y capacitor 216 is coupled to the first output terminal. For example, as shown... Figure 3A As shown, the second terminal of the second Y capacitor 216 is coupled to the second output terminal SGND of the first output terminal.

[0060] In some embodiments, the switching power supply circuit 21 further includes an input filter circuit 211.

[0061] The input filter circuit 211 includes two input terminals and two output terminals. The two input terminals are coupled to the first input terminal A1 and the second input terminal A2 of the switching power supply circuit 21, and the two output terminals are coupled to the two input terminals of the rectifier circuit 212. At this time, the two input terminals of the rectifier circuit 212 are indirectly coupled to the first input terminal A1 and the second input terminal A2 through the input filter circuit 211.

[0062] The input filter circuit 211 can effectively suppress the EMI interference of the power adapter, thereby meeting the EMI requirements of the power adapter 20.

[0063] In the case where the switching power supply circuit 21 also includes an input filter circuit 211: In one possible implementation, such as Figure 3A As shown, the first terminal of the first Y capacitor 215 is directly coupled to the first input terminal A1, that is, the first terminal of the first Y capacitor 215 is coupled to one input terminal of the input filter circuit 211. The second terminal of the first Y capacitor 215 is coupled to the first output terminal. For example, the second terminal of the first Y capacitor 215 is coupled to the first output terminal Vbus of the first output terminal.

[0064] The first terminal of the second Y capacitor 216 is directly coupled to the second input terminal A2, that is, the first terminal of the second Y capacitor 216 is coupled to the other input terminal of the input filter circuit 211. The second terminal of the second Y capacitor 216 is coupled to the first output terminal. For example, the second terminal of the second Y capacitor 216 is coupled to the second output terminal SGND.

[0065] In another possible implementation, such as Figure 3B As shown, the first terminal of the first Y capacitor 215 is coupled to the internal terminal of the input filter circuit 211, thereby enabling the first Y capacitor 215 to be coupled to the first input terminal A1 through a portion of the circuit of the input filter circuit 211. The first terminal of the second Y capacitor 216 is coupled to the internal terminal of the input filter circuit 211, thereby enabling the second Y capacitor 216 to be coupled to the second input terminal A2 through a portion of the circuit of the input filter circuit 211.

[0066] In another possible implementation, such as Figure 3C As shown, the first end of the first Y capacitor 215 is coupled to the output end of the input filter circuit 211, thereby achieving coupling of the first Y capacitor 215 to the first input terminal A1 through the input filter circuit 211. The first end of the second Y capacitor 216 is coupled to the output end of the input filter circuit 211, thereby achieving coupling of the second Y capacitor 216 to the second input terminal A2 through the input filter circuit 211.

[0067] When the switching power supply circuit 21 also includes an input filter circuit 211, the first end of the first Y capacitor 215 and the first end of the second Y capacitor 216 can be flexibly coupled according to the specific effect of the power adapter EMI.

[0068] In some embodiments, the switching power supply circuit 21 further includes an output rectifier and filter circuit 214.

[0069] The output rectifier and filter circuit 214 includes two input terminals and two output terminals. The two input terminals of the output rectifier and filter circuit 214 are correspondingly coupled to the output side of the power conversion circuit 213, and the two output terminals of the output rectifier and filter circuit 214 are correspondingly coupled to the first output terminal Vbus and the second output terminal SGND, respectively. In this case, the output side of the power conversion circuit 213 is indirectly coupled to the first output terminal Vbus and the second output terminal SGND through the output rectifier and filter circuit 214.

[0070] After the output rectifier and filter circuit 214 converts the low-voltage AC power transmitted from the output side of the power conversion circuit 213 into low-voltage DC power, a portion of the electrical energy is used for internal energy storage, and the remaining portion is transmitted to the first output terminal to charge the electronic device 10. Furthermore, when the output side of the power conversion circuit 213 stops outputting electrical energy to the subsequent switching power supply circuit, the output rectifier and filter circuit 214 transmits the stored electrical energy to the first output terminal to charge the electronic device 10.

[0071] Figure 4A A schematic diagram of the topology of a switching power supply circuit provided in an embodiment of this application; Figure 4B This is a schematic diagram of another switching power supply circuit topology provided in an embodiment of this application.

[0072] In some embodiments, such as Figure 4A As shown, the input filter circuit 211 includes an X capacitor CX1 and / or a common-mode inductor LF1. Figure 4A The filter circuit 211, including capacitor X CX1 and common-mode inductor LF1, is illustrated as an example.

[0073] For example, the first and second terminals of capacitor X CX1 are respectively coupled to the first input terminal A1 and the second input terminal A2 of the first input terminal. The input terminals of the two windings of common-mode inductor LF1 are respectively coupled to the first input terminal A1 and the second input terminal A2 of the first input terminal, and the output terminals of the two windings of common-mode inductor LF1 are respectively coupled to the two input terminals of rectifier circuit 212.

[0074] The presence of capacitor CX1 and common-mode inductor LF1 enables the input filter circuit 211 to effectively suppress EMI interference from the power adapter.

[0075] The structure of the input filter circuit 211 described above is only an illustration. Other structures with the same function as the input filter circuit 211 provided in the embodiments of this application are also applicable to the embodiments of this application.

[0076] In some embodiments, the rectifier circuit 212 includes a rectifier bridge D1 and a bus capacitor Ci.

[0077] The two input terminals of rectifier bridge D1 serve as the two input terminals of rectifier circuit 212, and are correspondingly coupled to the two output terminals of input filter circuit 211. The two output terminals of rectifier bridge D1 serve as the two output terminals of rectifier circuit 212, and are correspondingly coupled to the input side of power conversion circuit 213.

[0078] The two ends of the bus capacitor Ci are coupled to the two output terminals of the rectifier bridge D1.

[0079] In some embodiments, one of the two input terminals of the rectifier bridge D1 is also coupled to ground PGND, and one end of the bus capacitor Ci is also coupled to ground PGND.

[0080] In some embodiments, the power conversion circuit 213 includes a transformer T1 and a switching transistor Q1.

[0081] Transformer T1 includes a primary side and a secondary side. The primary side of transformer T1 and the switching transistor Q1 are connected in series between the two output terminals of rectifier circuit 212. The first terminal of the secondary side of transformer T1 is connected to the first output terminal, and the second terminal of the secondary side of transformer T1 is connected to the second output terminal. I3 is the leakage current value of the parasitic capacitance Cps of the primary and secondary sides of the transformer.

[0082] In some embodiments, the output rectifier filter circuit 214 includes a switching device D2 and a capacitor Co. For example, the switching device D2 includes a diode or a field-effect transistor. The figure illustrates this by using a diode as an example of the switching device D2.

[0083] The switching device D2 is connected in series between the second end of the secondary side of transformer T1 and the second output terminal SGND. The two ends of capacitor Co are coupled to the first output terminal Vbus and the second output terminal SGND, respectively.

[0084] In some embodiments, the first Y capacitor 215 includes a first Y capacitor Cy1. The first Y capacitor 215 may also include other Y capacitors connected in series and / or in parallel with the first Y capacitor Cy1. This embodiment is merely illustrative and does not constitute any limitation.

[0085] In some embodiments, the second Y capacitor 216 includes a second Y capacitor Cy2. The second Y capacitor 216 may also include other Y capacitors connected in series and / or in parallel with the second Y capacitor Cy2. This embodiment is merely illustrative and does not constitute any limitation.

[0086] In some embodiments, such as Figure 4A As shown, the first terminal of the first Y capacitor Cy1 is coupled to the first input terminal A1, and the second terminal of the first Y capacitor Cy1 is coupled to the first output terminal Vbus. The first terminal of the second Y capacitor Cy2 is coupled to the second input terminal A2, and the second terminal of the second Y capacitor Cy2 is coupled to the second output terminal SGND.

[0087] In one possible implementation, to meet EMI requirements, the sum of the capacitance values ​​of the first Y capacitor Cy1 and the second Y capacitor Cy2 is equal to the capacitance value of the Y capacitors in the above embodiment. That is, cy1 + cy2 = CY, where cy1 is the capacitance value of the first Y capacitor Cy1 and cy2 is the capacitance value of the second Y capacitor Cy2. Since both cy1 and cy2 are positive values, cy1... <CY,cy2<CY。

[0088] For example, the target Y-capacitance value CY=110pF, cy1<110pF, cy2<110pF, and cy1+cy2=110pF.

[0089] Based on the above architecture, as Figure 4A shown, in the first usage mode, the power adapter 20 is inserted in the forward direction. The first input terminal A1 is coupled to the live line L of the mains power, and the second input terminal A2 is coupled to the neutral line N of the mains power. The neutral line N is usually grounded in the power distribution system to provide a reference ground potential.

[0090] Accordingly, there is a voltage difference across the first Y-capacitor Cy1, so a leakage current exists in the first Y-capacitor Cy1.

[0091] Accordingly, the voltage difference across the second Y-capacitor Cy2 is nearly 0V, so the second Y-capacitor Cy2 is bypassed by the leakage current loop, that is, no leakage current exists in the second Y-capacitor Cy2.

[0092] Therefore, when the power adapter 20 is inserted in the forward direction, of the first Y-capacitor Cy1 and the second Y-capacitor Cy2, a leakage current exists in the first Y-capacitor Cy1, and no leakage current exists in the second Y-capacitor Cy2. At this time, the total leakage current generated by the switching power supply circuit 21 is borne by the first Y-capacitor Cy1 and the primary-secondary side parasitic capacitance Cps of the transformer. Under the two architectures where the switching power supply circuit 21 includes two paths of Y-capacitors and the switching power supply circuit 21 includes one path of Y-capacitor, the voltage difference across the first Y-capacitor Cy1 and the Y-capacitor Cy remains unchanged. According to the leakage current calculation formula, since cy1<CY, the leakage current I1 of the first Y-capacitor Cy1 is smaller than the leakage current of the Y-capacitor Cy under the architecture where the switching power supply circuit 21 includes one path of Y-capacitor. Moreover, under the architecture where the switching power supply circuit 21 includes two paths of Y-capacitors, the sum of the leakage currents of the first Y-capacitor Cy1 and the primary-secondary side parasitic capacitance Cps of the transformer is also smaller than the sum of the leakage currents of the Y-capacitor Cy and the primary-secondary side parasitic capacitance Cps of the transformer under the architecture where the switching power supply circuit 21 includes one path of Y-capacitor.

[0093] Or, for example, as Figure 4B shown, in the second usage mode, the power adapter 20 is inserted in the reverse direction. The first input terminal A1 is coupled to the neutral line N of the mains power, and the second input terminal A2 is coupled to the live line L of the mains power.

[0094] Accordingly, the voltage difference across the first Y-capacitor Cy1 is nearly 0V. Therefore, the first Y-capacitor Cy1 is bypassed by the leakage current loop, that is, no leakage current exists in Cy2.

[0095] Accordingly, there is a voltage difference across the second Y-capacitor Cy2, so a leakage current exists in the second Y-capacitor Cy2.

[0096] Therefore, when the power adapter 20 is reversely plugged, of the first Y capacitor Cy1 and the second Y capacitor Cy2, the second Y capacitor Cy2 has a leakage current, and the first Y capacitor Cy1 has no leakage current. At this time, the total leakage current generated by the switching power supply circuit 21 is borne by the second Y capacitor Cy2 and the primary-secondary side parasitic capacitance Cps of the transformer. According to the leakage current calculation formula, under the two architectures where the switching power supply circuit 21 includes two paths of Y capacitors and the switching power supply circuit 21 includes one path of Y capacitor, the voltage difference across the second Y capacitor Cy2 and the Y capacitor Cy remains unchanged. According to the leakage current calculation formula, since cy2<CY, the leakage current I2 of the second Y capacitor Cy2 is smaller than the leakage current of the Y capacitor Cy under the architecture where the switching power supply circuit 21 has only one path of Y capacitor. Moreover, under the architecture where the switching power supply circuit 21 includes two paths of Y capacitors, the sum of the leakage currents of the second Y capacitor Cy2 and the primary-secondary side parasitic capacitance Cps of the transformer is also smaller than the sum of the leakage currents of the Y capacitor Cy and the primary-secondary side parasitic capacitance Cps of the transformer under the architecture where the switching power supply circuit 21 includes one path of Y capacitor.

[0097] In summary, under the architecture of the switching power supply circuit 21 provided in the embodiments of the present application, the sum of the capacitance value of the first Y capacitor Cy1 and the capacitance value of the second Y capacitor Cy2 can be adjusted to make EMI meet the specification requirements. On this basis, when the power adapter 20 is normally plugged, the first Y capacitor Cy1 has a leakage current, the second Y capacitor Cy2 is bypassed, and the second Y capacitor Cy2 has no leakage current. When the power adapter 20 is reversely plugged, the second Y capacitor Cy2 has a leakage current, the first Y capacitor Cy1 is bypassed, and the first Y capacitor Cy1 has no leakage current. Therefore, no matter the power adapter 20 is normally plugged or reversely plugged, one of the first Y capacitor Cy1 and the second Y capacitor Cy2 has a leakage current. Then, the leakage currents of the first Y capacitor and the second Y capacitor are both smaller than the leakage current of the Y capacitor under the architecture with only one path of Y capacitor. That is to say, no matter the power adapter 20 is normally or reversely plugged, the leakage current of the switching power supply circuit 21 can be reduced. Therefore, when the switching power supply circuit 21 provided in this embodiment is applied to the power adapter 20, on the basis that the power adapter 20 meets the EMI requirements and specifications, it is possible to reduce the leakage current of the power adapter 20 when charging the electronic device 10 without requiring the user to distinguish between normal and reverse plugging, thereby improving the user's charging experience.

[0098] In a possible implementation, the capacitance value of the first Y capacitor Cy1 and the capacitance value of the second Y capacitor Cy2 are not equal. Then, the improvement effect on the leakage current will be different during normal plugging and reverse plugging.

[0099] In another possible implementation, the capacitance value of the first Y capacitor Cy1 is equal to the capacitance value of the second Y capacitor Cy2. That is, cy1=cy2. For example, cy1=cy2=CY / 2.

[0100] As described above, when the power adapter 20 is plugged in correctly, of the two Y capacitors, first Y capacitor Cy1 has leakage current, while second Y capacitor Cy2 does not. When the power adapter 20 is plugged in reverse, of the two Y capacitors, second Y capacitor Cy2 has leakage current, while first Y capacitor Cy1 does not. Therefore, when the capacitance values ​​of the first Y capacitor Cy1 and the second Y capacitor Cy2 are equal, regardless of whether the power adapter 20 is plugged in correctly or reverse, the Y capacitors with the same capacitance value will have leakage current. Thus, the improvement effect on leakage current is the same regardless of whether the power adapter 20 is plugged in correctly or reverse.

[0101] The following is a schematic description of the coupling method between the second terminal of the first Y capacitor Cy1 and the second terminal of the second Y capacitor Cy2 and the first output terminal in an embodiment of this application.

[0102] In one possible implementation, such as Figure 4B As shown, the second terminal of the first Y capacitor Cy1 is coupled to the first output terminal Vbus. The second terminal of the second Y capacitor Cy2 is coupled to the second output terminal SGND.

[0103] Figures 5-7 This is a schematic diagram of the topology of another switching power supply circuit provided in an embodiment of this application.

[0104] In another possible implementation, such as Figure 5 As shown, the second end of the first Y capacitor Cy1 is coupled to the second output terminal SGND, and the second end of the second Y capacitor Cy2 is coupled to the first output terminal Vbus.

[0105] In another possible implementation, such as Figure 6 As shown, the second terminal of the first Y capacitor Cy1 is coupled to the first output terminal Vbus. The second terminal of the second Y capacitor Cy2 is also coupled to the first output terminal Vbus.

[0106] In another possible implementation, such as Figure 7 As shown, the second terminal of the first Y capacitor Cy1 is coupled to the second output terminal SGND. The second terminal of the second Y capacitor Cy2 is also coupled to the second output terminal SGND.

[0107] The above example illustrates the direct coupling of the second terminal of the first capacitor Cy1 and the second terminal of the second capacitor Cy2 to one of the first output terminal Vbus and the second output terminal SGND. Alternatively, the second terminals of the first capacitor Cy1 and the second terminal of the second capacitor Cy2 can be indirectly coupled to either the first output terminal Vbus or the second output terminal SGND.

[0108] In summary, the second terminals of the first Y capacitor and the second Y capacitor can be coupled to the two output terminals of the switching power supply circuit 21 in various ways to form a variety of optional circuit configurations, thereby giving the switching power supply circuit 21 a high degree of flexibility and configurability.

[0109] Figure 8A A schematic diagram of a switching power supply circuit provided in an embodiment of this application; Figure 8B This is a schematic diagram of a switching power supply circuit provided in an embodiment of this application.

[0110] In some embodiments, the switching power supply circuit 21 further includes a third Y capacitor. A first terminal of the third Y capacitor is coupled to an output terminal of the rectifier circuit 212, and a second terminal of the third Y capacitor is coupled to a first output terminal.

[0111] For example, such as Figure 8A As shown, the third Y capacitor includes a third Y capacitor Cy3. A first terminal of the third Y capacitor Cy3 is coupled to an output terminal of the rectifier circuit 212, and a second terminal of the third Y capacitor Cy3 is coupled to a first output terminal. For example, the second terminal of the third Y capacitor Cy3 is coupled to the first output terminal Vbus.

[0112] The third Y capacitor may also include other Y capacitors connected in series and / or in parallel with the third Y capacitor Cy3. The embodiments in this application are merely illustrative and do not constitute any limitation.

[0113] In one possible implementation, to meet EMI requirements, the sum of the capacitance values ​​of the first Y capacitor Cy1, the second Y capacitor Cy2, and the third Y capacitor Cy3 is equal to the capacitance value of the Y capacitor Cy in the architecture with only one Y capacitor in the above embodiment. That is, cy1 + cy2 + cy3 = CY. Here, cy1 is the capacitance value of the first Y capacitor Cy1, cy2 is the capacitance value of the second Y capacitor Cy2, and cy3 is the capacitance value of the third Y capacitor Cy3. Since cy1, cy2, and cy3 are all positive values, cy1... <CY,cy2<CY,cy3<CY。

[0114] For example, the target capacitance value of Y is CY = 110pF. cy1 < 110pF, cy2 < 110pF, cy3 < 110pF, cy1 + cy2 + cy3 = 110pF.

[0115] Based on the above architecture, such as Figure 8A As shown, in the first usage mode, the power adapter 20 is plugged in correctly. The first input terminal A1 is coupled to the live wire L of the mains power, and the second input terminal A2 is coupled to the neutral wire N of the mains power.

[0116] Therefore, there is a voltage difference across the first Y capacitor Cy1. Consequently, the first Y capacitor Cy1 experiences leakage current.

[0117] Based on this, the voltage difference across the second Y capacitor Cy2 is approximately 0V. Therefore, the second Y capacitor Cy2 is bypassed by the leakage current loop, that is, no leakage current exists in the second Y capacitor Cy2.

[0118] A first terminal of the third Y capacitor Cy3 is coupled to an output terminal of the rectifier bridge D1 in the rectifier circuit 212, and a second terminal of the third Y capacitor Cy3 is coupled to the first output terminal Vbus of the switching power supply circuit 21. Based on this, a voltage difference exists across the third Y capacitor Cy3. Therefore, a leakage current exists in the third Y capacitor Cy3.

[0119] When the power adapter 20 is plugged in the forward direction, in the switching power supply circuit 21, leakage currents exist in the first Y capacitor Cy1 and the third Y capacitor Cy3. At this time, the total leakage current generated by the switching power supply circuit 21 is borne by the first Y capacitor Cy1, the third Y capacitor Cy3 and the primary-secondary side parasitic capacitance Cps of the transformer. According to the leakage current calculation formula, since cy1+cy3<CY, the sum of the leakage currents of the first Y capacitor Cy1 and the third Y capacitor Cy3 is smaller than the leakage current of the Y capacitor Cy in the architecture where the switching power supply circuit 21 includes one Y capacitor. Therefore, under the architecture where the switching power supply circuit 21 includes three Y capacitors, the sum of the leakage currents of the first Y capacitor Cy1, the third Y capacitor Cy3 and the primary-secondary side parasitic capacitance Cps of the transformer is also smaller than the sum of the leakage currents of the Y capacitor Cy and the primary-secondary side parasitic capacitance Cps of the transformer in the architecture where the switching power supply circuit 21 includes one Y capacitor.

[0120] As Figure 8B shown, in the second usage mode, the power adapter 20 is plugged in the reverse direction.

[0121] The first input terminal A1 is coupled to the neutral line N of the mains utility power, and the second input terminal A2 is coupled to the live line L of the mains utility power.

[0122] Based on this, the voltage difference across the first Y capacitor Cy1 is approximately 0V. Therefore, the first Y capacitor Cy1 is bypassed by the leakage current loop, that is, no leakage current exists in the first Y capacitor Cy1.

[0123] Based on this, a voltage difference exists across the second Y capacitor Cy2. Therefore, a leakage current exists in the second Y capacitor Cy2.

[0124] A first terminal of the third Y capacitor Cy3 is coupled to an output terminal of the rectifier bridge D1 in the rectifier circuit 212. In this case, the voltage at the output terminal of the rectifier bridge D1 does not change with the insertion direction of the power adapter 20. That is, no matter the power adapter 20 is inserted in the forward direction or the reverse direction, the voltage at the first terminal of the third Y capacitor Cy3 does not change. A second terminal of the third Y capacitor Cy3 is coupled to the first output terminal Vbus of the switching power supply circuit 21. Based on this, a voltage difference exists across the third Y capacitor Cy3. Therefore, a leakage current exists in the third Y capacitor Cy3.

[0125] When the power adapter 20 is inserted in the reverse direction, leakage currents exist in the second Y capacitor Cy2 and the third Y capacitor Cy3 in the switching power supply circuit 21. At this time, the total leakage current generated by the switching power supply circuit 21 is borne by the second Y capacitor Cy2, the third Y capacitor Cy3, and the primary-secondary parasitic capacitance Cps of the transformer. According to the leakage current calculation formula, since cy2+cy3<CY, the sum of the leakage currents of the second Y capacitor Cy2 and the third Y capacitor Cy3 is less than the leakage current of the Y capacitor Cy in the architecture where the switching power supply circuit 21 includes one Y capacitor. Therefore, in the architecture where the switching power supply circuit 21 includes three Y capacitors, the sum of the leakage currents of the second Y capacitor Cy2, the third Y capacitor Cy3, and the primary-secondary parasitic capacitance Cps of the transformer is also less than the sum of the leakage currents of the Y capacitor Cy and the primary-secondary parasitic capacitance Cps of the transformer in the architecture where the switching power supply circuit 21 includes one Y capacitor.

[0126] In conclusion, under the architecture of the switching power supply circuit 21 provided in the embodiments of the present application, EMI can meet the specification requirements by adjusting the sum of the capacitances of the first Y capacitor Cy1, the second Y capacitor Cy2, and the third Y capacitor Cy3. At the same time, under this architecture, the capacitance setting manners of each Y capacitor are more flexible. On this basis, when the power adapter 20 is inserted in the forward direction, leakage currents exist in the first Y capacitor Cy1 and the third Y capacitor Cy3, and the second Y capacitor Cy2 is bypassed. When the power adapter 20 is inserted in the reverse direction, leakage currents exist in the second Y capacitor Cy2 and the third Y capacitor Cy3, and the first Y capacitor Cy1 is bypassed. Therefore, no matter the power adapter 20 is inserted in the forward direction or the reverse direction, the sum of the leakage currents of the first Y capacitor Cy1 and the third Y capacitor Cy3, or the sum of the leakage currents of the second Y capacitor Cy2 and the third Y capacitor Cy3, is less than the leakage current of the Y capacitor under the architecture with only one Y capacitor. That is to say, under the architecture of the switching power supply circuit 21 in the embodiments of the present application, the leakage current of the switching power supply circuit 21 can be reduced no matter the power adapter 20 is inserted in the forward direction or the reverse direction. Therefore, when the switching power supply circuit 21 provided in this embodiment is applied to the power adapter 20, on the basis that the power adapter 20 meets the EMI requirement specification, the leakage current of the power adapter 20 during charging the electronic device 10 can be reduced without the user needing to distinguish the forward and reverse insertion directions, thereby improving the user's charging experience.

[0127] Figure 9 This is a schematic diagram of a charging system provided in an embodiment of this application.

[0128] like Figure 9 As shown, the surface of the first housing 22 includes a marking pattern 221, which is used to identify the first input terminal A1. For example, different marking patterns 221 can be used to distinguish between the first input terminal A1 and the second input terminal A2. In this embodiment, the marking pattern 221 is used to identify the first input terminal A1 as an example. For example, the marking pattern 221 includes geometric shapes, text, symbols, or any combination thereof. For example, the marking pattern 221 can be a star, triangle, circle, "positive", "negative", "+", "-", "A", "B", "1", or "2", etc.

[0129] For example, such as Figure 9 As shown, the first input terminal is coupled to the socket 2 via the plug of the power adapter 20.

[0130] For example, the capacitance of the first Y capacitor 215 is smaller than the capacitance of the second Y capacitor 216. For instance, the first terminal of the first Y capacitor 215 is coupled to the first input terminal A1, and the first terminal of the second Y capacitor 216 is coupled to the second input terminal A2.

[0131] For example, let's take the first input terminal A1 with a marking pattern 221 as an example. The marking pattern 221 identifies the first input terminal A1, thus coupling it to the live wire socket L of the socket 2. At this time, due to the voltage difference across the first Y capacitor 215, leakage current occurs in the first Y capacitor 215. However, the second input terminal A2 is coupled to the neutral wire socket N of the socket 2. Since the voltage difference across the second Y capacitor 216 is nearly zero, there is no leakage current in the second Y capacitor 216.

[0132] In this situation, since the capacitance of the first Y capacitor 215, which has leakage current, is less than the capacitance of the Y capacitor when the capacitances of the two Y capacitors are equal, the leakage current of the first Y capacitor 215 is also less than the leakage current of the Y capacitor when the capacitances of the two Y capacitors are equal. This further reduces the leakage current of the switching power supply circuit 21, meaning that the leakage current of the power adapter 20 when charging the electronic device 10 is further reduced, thereby improving the user's charging experience.

[0133] Figure 9 This is merely one possible implementation of the marking pattern 221, and the embodiments of this application do not limit it.

[0134] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A switching power supply circuit, characterized in that, include: The first input terminal includes a first input terminal and a second input terminal; The first input terminal is used to receive alternating current; The first output terminal includes a first output terminal and a second output terminal; The power conversion circuit (213) includes an input side and an output side; the output side is correspondingly coupled to the first output terminal and the second output terminal. The rectifier circuit (212) includes two input terminals and two output terminals; the two input terminals are correspondingly coupled to the first input terminal and the second input terminal; The two output terminals are correspondingly coupled to the input side; A first Y capacitor, wherein a first end of the first Y capacitor is coupled to the first input terminal, and a second end of the first Y capacitor is coupled to the first output terminal; The second Y capacitor has its first end coupled to the second input terminal and its second end coupled to the first output terminal.

2. The switching power supply circuit according to claim 1, characterized in that, The capacitance of the first Y capacitor is equal to the capacitance of the second Y capacitor; or, The capacitance of the first Y capacitor is smaller than that of the second Y capacitor.

3. The switching power supply circuit according to claim 1 or 2, characterized in that, The switching power supply circuit also includes an input filter circuit; The two input terminals of the input filter circuit are coupled to the first input terminal and the second input terminal respectively, and the two output terminals of the input filter circuit are coupled to the two input terminals of the rectifier circuit respectively.

4. The switching power supply circuit according to claim 3, characterized in that, The first end of the first Y capacitor and the first end of the second Y capacitor are coupled to the two output terminals of the filter circuit.

5. The switching power supply circuit according to any one of claims 1-4, characterized in that, The second end of the first Y capacitor and the second end of the second Y capacitor are both coupled to the first output terminal; or, The second end of the first Y capacitor and the second end of the second Y capacitor are both coupled to the second output terminal.

6. The switching power supply circuit according to any one of claims 1-4, characterized in that, The second end of the first Y capacitor is coupled to the first output terminal, and the second end of the second Y capacitor is coupled to the second output terminal.

7. The switching power supply circuit according to any one of claims 1-6, characterized in that, The switching power supply circuit also includes a third Y capacitor; The first end of the third Y capacitor is coupled to one output terminal of the rectifier circuit, and the second end of the third Y capacitor is coupled to the first output terminal.

8. The switching power supply circuit according to any one of claims 1-7, characterized in that, The power conversion circuit includes a transformer and a switching transistor; The transformer includes a primary side and a secondary side. The primary side and the switching transistor are connected in series between the two output terminals of the rectifier circuit, and the secondary side is connected between the first output terminal and the second output terminal.

9. A power adapter, characterized in that, It includes a first housing and a switching power supply circuit as described in any one of claims 1-8, which is installed within the first housing.

10. The power adapter according to claim 9, characterized in that, The surface of the first housing includes a marking pattern for identifying the first input terminal; The capacitance of the first Y capacitor is smaller than that of the second Y capacitor.

11. A charging system, characterized in that, It includes a power adapter and an electronic device; the power adapter is coupled to the electronic device, and the power adapter includes the power adapter as described in claim 9 or 10.

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