A switching power supply circuit, a flyback switching power supply, and electronic equipment.

Abstract

This application provides a switching power supply circuit, a flyback switching power supply, and an electronic device, relating to the field of flyback switching power supply technology. The circuit includes: a transformer, a 485 power module, a main control power module, a metering power module, a controller, a first Y capacitor, a second Y capacitor, and a third Y capacitor. The transformer includes a first primary winding, a second primary winding, a third primary winding, a first secondary winding, and a second secondary winding, providing isolated power to the 485 power module, the main control power module, the metering power module, and the controller. The switching power supply ground and analog ground are electrically connected through the first Y capacitor; the 485 ground and digital ground are electrically connected through the second Y capacitor, and the digital ground and analog ground are further electrically connected through the third Y capacitor. This circuit can introduce the noise of each isolated power supply in the switching power supply circuit to ground, thereby reducing the noise at the output terminal of the switching power supply and thus reducing the ripple of the output voltage.

Description

Technical Field

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

[0002] Smart meters are a general term for electricity meters that have automatic metering and billing functions as well as data transmission capabilities. A smart meter is a digital meter that internally includes a microprocessor, input and output interfaces, communication devices, and a display screen. As one of the basic devices for data acquisition in smart grids, smart meters undertake the tasks of collecting, metering, and transmitting raw electrical energy data, and are fundamental to information integration, analysis and optimization, and information presentation.

[0003] With the continuous development of single-phase smart meters, the integration of switching power supplies within these meters is becoming increasingly common. Flyback switching power supplies are DC-DC converters that achieve electrical isolation between the input and output circuits using a high-frequency transformer. Their operating principle is based on the alternating process of energy storage and release controlled by switching on and off. Based on this principle, during normal operation, the MOSFETs (metal-oxide-semiconductor-field-effect transistors) or diodes in their internal circuitry generate high-frequency transient noise during switching. This noise is coupled to the output terminal through the power plane or parasitic parameters, resulting in relatively high output noise from the switching power supply.

[0004] The voltage output of the switching power supply provides power to the smart meter, ensuring its normal operation. For smart meters, excessive power supply noise at the switching power supply output can affect the accuracy of metering and billing. For smart meters including a carrier module, excessive power supply noise can interfere with communication, leading to communication failures. To ensure the accuracy of metering and the stability of communication, smart meters place higher demands on the noise level of the switching power supply output. Therefore, reducing the noise at the switching power supply output is a crucial issue that needs to be addressed. Utility Model Content

[0005] This application provides a switching power supply circuit, a flyback switching power supply, and an electronic device to reduce noise at the output of the switching power supply.

[0006] In a first aspect, this application provides a switching power supply circuit, the switching power supply circuit comprising: a transformer, a 485 power module, a main control power module, a metering power module, a controller, a first Y capacitor, a second Y capacitor, and a third Y capacitor; wherein, the transformer comprises a first primary winding, a second primary winding, a third primary winding, a first secondary winding, and a second secondary winding.

[0007] The first end of the first primary winding is used to connect to the input voltage, and the second end of the first primary winding is electrically connected to the first end of the controller; the first end of the second primary winding is connected to the switching power supply ground, and the second end of the second primary winding is electrically connected to the second end of the controller; the first end of the third primary winding is connected to analog ground, and the second end of the third primary winding is electrically connected to the input end of the metering power module; the first end of the first secondary winding is electrically connected to the input end of the 485 power module, and the second end of the first secondary winding is connected to the 485 ground; the first end of the second secondary winding is electrically connected to the input end of the main control power module, and the second end of the second secondary winding is connected to digital ground; the main control power module is electrically connected to the third end of the controller;

[0008] The switching power supply ground and the analog ground are electrically connected through the first Y capacitor;

[0009] The 485 ground and the digital ground are electrically connected through the second Y capacitor, and the digital ground and the analog ground are electrically connected through the third Y capacitor.

[0010] In one possible design, the withstand voltage of the first Y capacitor, the second Y capacitor, and the third Y capacitor is not less than 4KV.

[0011] In one possible design, the capacitance values ​​of the first Y capacitor, the second Y capacitor, and the third Y capacitor are all 1nF or 470pF.

[0012] In one possible design, the 485 power supply module includes: a first rectifier submodule, a first filter submodule, and a first voltage regulator submodule; the first rectifier submodule includes: a first resistor, a first capacitor, and a first diode; the first filter submodule includes: a first polarized capacitor; the first voltage regulator submodule includes: a second capacitor, a second resistor, a third capacitor, a fourth capacitor, and a first voltage regulator;

[0013] The first end of the first resistor is electrically connected to the first end of the first secondary winding and the positive terminal of the first diode, and the second end of the first resistor is electrically connected to the first end of the first capacitor.

[0014] The second terminal of the first capacitor is electrically connected to the negative terminal of the first diode, the positive terminal of the first polarized capacitor, the first terminal of the second capacitor, the first terminal of the second resistor, and the input terminal of the first voltage regulator.

[0015] The output terminal of the first voltage regulator is electrically connected to the first terminal of the third capacitor and the first terminal of the fourth capacitor, respectively, for outputting 485 power supply voltage;

[0016] The negative terminal of the first polarized capacitor, the second terminal of the second capacitor, the second terminal of the second resistor, the third terminal of the first voltage regulator, the second terminal of the third capacitor, and the second terminal of the fourth capacitor are all connected to 485 ground.

[0017] In one possible design, the main control power supply module includes: a second rectifier submodule and a second filter submodule; the second rectifier submodule includes: a third resistor, a fifth capacitor and a second diode; the second filter submodule includes: a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second polarized capacitor and a first inductor;

[0018] The first end of the third resistor is electrically connected to the positive terminal of the second diode and the first end of the second secondary winding, respectively; the second end of the third resistor is electrically connected to the first end of the fifth capacitor.

[0019] The second terminal of the fifth capacitor is electrically connected to the negative terminal of the second diode, the first terminal of the sixth capacitor, the first terminal of the seventh capacitor, the positive terminal of the second polarized capacitor, the first terminal of the first inductor, and the third terminal of the controller.

[0020] The second end of the first inductor is electrically connected to the first end of the eighth capacitor and the first end of the ninth capacitor, respectively, for outputting the main control power supply voltage;

[0021] The second terminal of the sixth capacitor, the second terminal of the seventh capacitor, the negative terminal of the second polarized capacitor, the second terminal of the eighth capacitor, and the second terminal of the ninth capacitor are all connected to digital ground.

[0022] In one possible design, the metering power supply module includes: a third rectifier submodule, a third filter submodule, and a second voltage regulator submodule; the third rectifier submodule includes: a fourth resistor, a tenth capacitor, and a third diode; the third filter submodule includes: a third polarized capacitor; the second voltage regulator submodule includes: an eleventh capacitor, a twelfth capacitor, and a second voltage regulator;

[0023] The first terminal of the tenth capacitor is electrically connected to the positive terminal of the third diode and the second terminal of the third primary winding, respectively, and the second terminal of the tenth capacitor is electrically connected to the first terminal of the fourth resistor.

[0024] The second end of the fourth resistor is electrically connected to the negative terminal of the third diode, the positive terminal of the third polarized capacitor, the first end of the eleventh capacitor, and the input terminal of the second voltage regulator.

[0025] The output terminal of the second voltage regulator is electrically connected to the first terminal of the twelfth capacitor, and is used to output the metering power supply voltage;

[0026] The negative terminal of the third polarity capacitor, the second terminal of the eleventh capacitor, the second terminal of the twelfth capacitor, and the third terminal of the second voltage regulator are all connected to analog ground.

[0027] In one possible design, the controller is model 8254T / Q, and the first voltage regulator is model CJ78L05.

[0028] In one possible design, the second voltage regulator is model CJ78L05.

[0029] Secondly, this application provides a flyback switching power supply, including: the switching power supply circuit as described in the first aspect.

[0030] Thirdly, this application provides an electronic device, including: a flyback switching power supply as described in the second aspect.

[0031] The beneficial effects of the embodiments of this application are as follows:

[0032] In this embodiment, the 485 power module, main control power module, metering power module, and controller are isolated by the first primary winding, second primary winding, third primary winding, first secondary winding, and second secondary winding of the transformer, which reduces interference between the modules. On the primary side of the transformer, the switching power supply ground is electrically connected to the analog ground through the first Y capacitor, introducing the noise from the primary side of the transformer to the analog ground. On the secondary side of the transformer, the noise from the 485 ground (G485) is first introduced to the digital ground through the second Y capacitor, and then the noise from both the 485 ground and the digital ground is introduced to the analog ground through the third Y capacitor. This allows the noise in the switching power supply circuit to be introduced to the ground, thereby reducing the noise at the output of the switching power supply and thus reducing the ripple of the output voltage. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0034] Figure 1A schematic diagram of the circuit structure of a switching power supply circuit provided in an embodiment of this application;

[0035] Figure 2 A circuit diagram of a switching power supply circuit provided in an embodiment of this application. Detailed Implementation

[0036] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c alone can mean: a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] The terms “center,” “longitudinal,” “lateral,” “up,” “down,” “left,” “right,” “front,” and “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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] The terms "connected" and "connected" should be interpreted broadly. For example, in circuit structures, "connected" or "connected" can refer not only to physical connections but also to electrical or signal connections. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Similarly, a signal connection can refer to a connection via a circuit or a medium, such as radio waves. Those skilled in the art will understand the specific meaning of these terms in this application based on the specific circumstances.

[0039] In the design of flyback switching power supplies, in order to reduce output noise and output voltage ripple, the following methods are adopted: The first method is to increase the filtering effect by adding multi-stage filter circuits; the second method is to make reasonable layout of the PCB circuit board of the flyback switching power supply to reduce noise.

[0040] To reduce noise at the output of the switching power supply, this application proposes a switching power supply circuit, see [link to relevant documentation]. Figure 1 , Figure 1 A circuit structure diagram of a switching power supply circuit provided in an embodiment of this application is shown below. Figure 1 As shown, the switching power supply circuit 1000 may include: a transformer T1, a 485 power module, a main control power module, a metering power module, a controller, a first Y capacitor CY1, a second Y capacitor CY2, and a third Y capacitor CY3; wherein, the transformer T1 includes a first primary winding NP1, a second primary winding NP2, a third primary winding NP3, a first secondary winding NS1, and a second secondary winding NS2.

[0041] The first terminal of the first primary winding NP1 is used to connect to the input voltage IN, and the second terminal of the first primary winding NP1 is electrically connected to the first terminal SW of the controller; the first terminal of the second primary winding NP2 is connected to the switching power supply ground MGND, and the second terminal of the second primary winding NP2 is electrically connected to the second terminal VDD of the controller; the first terminal of the third primary winding NP3 is connected to the analog ground AGND, and the second terminal of the third primary winding NP3 is electrically connected to the input terminal of the metering power supply module; the first terminal of the first secondary winding NS1 is electrically connected to the input terminal of the 485 power supply module, and the second terminal of the first secondary winding NS1 is connected to the 485 ground G485; the first terminal of the second secondary winding NS2 is electrically connected to the input terminal of the main control power supply module, and the second terminal of the second secondary winding NS2 is connected to the digital ground GND; the main control power supply module is electrically connected to the third terminal COMP of the controller.

[0042] The switching power supply ground MGND and the analog ground AGND are electrically connected through the first Y capacitor CY1.

[0043] The 485 ground G485 and the digital ground GND are electrically connected through the second Y capacitor CY2, and the digital ground GND and the analog ground AGND are electrically connected through the third Y capacitor CY3.

[0044] As one of the basic devices for data acquisition in smart grids, smart meters need to integrate a communication module, a main control module, and a metering module to complete the functions of raw energy data acquisition, metering, and data transmission. The communication module is used to realize data transmission, the main control module is used for internal control, and the metering module is used for raw energy data acquisition and metering.

[0045] To reduce interference between functional modules, they are often isolated, and correspondingly, the power supply circuits for each module are also isolated. In smart meters, the communication module used for data transmission is typically a RS-485 communication module. Therefore, the power supply circuits for the communication module, main control module, and metering module are respectively the RS-485 power supply module, the main control power supply module, and the metering power supply module. Additionally, for flyback switching power supplies, a controller is needed to adjust the switching frequency and duration of the primary-side switch to control the alternating process of energy storage and release, thereby obtaining a stable voltage output.

[0046] The switching power supply circuit in this application is a flyback switching power supply circuit, which uses a transformer to isolate the power supply circuit sections of each module. Specifically, transformer T1 includes a first primary winding NP1, a second primary winding NP2, a third primary winding NP3, a first secondary winding NS1, and a second secondary winding NS2. The first terminal of the first primary winding NP1 is used to connect to the input voltage IN, and the second terminal of the first primary winding NP1 is electrically connected to the first terminal SW of the controller. The first terminal of the second primary winding NP2 is connected to the switching power supply ground MGND, and the second terminal of the second primary winding NP2 is electrically connected to the second terminal VDD of the controller. Based on the above electrical connections, it can be seen that the first primary winding NP1 and the second primary winding NP2 are used to connect to the input voltage IN and supply power to the controller. In the flyback switching power supply circuit, the controller is used to adjust the switching cycle to control the alternating process of energy storage and release, thereby achieving stable voltage output. The ground corresponding to this part is set to the switching power supply ground MGND.

[0047] The metering module is used for raw energy data acquisition and metering. Therefore, it needs to be powered from the primary winding of transformer T1. Power is supplied to the input of the metering power module through the third primary winding NP3. Specifically, the first end of the third primary winding NP3 is connected to the analog ground AGND, and the second end of the third primary winding NP3 is electrically connected to the input of the metering power module. The ground corresponding to this part is set as the analog ground AGND, which in this application can be electrically connected to the earth.

[0048] The 485 communication module is used for data transmission and requires a stable voltage. Power is supplied to this module from the secondary side of transformer T1, which is achieved through the first secondary winding NS1, supplying power to the input terminal of the 485 power module. Specifically, the first end of the first secondary winding NS1 is electrically connected to the input terminal of the 485 power module, and the second end of the first secondary winding NS1 is connected to 485 ground G485. The corresponding ground for this part is set to 485 ground G485.

[0049] The main control module is the control core of the smart meter and also requires a stable voltage. Power is supplied to this module from the secondary side of transformer T1, specifically through the second secondary winding NS2, which powers the input of the main control power module. The first terminal of the second secondary winding NS2 is electrically connected to the input of the main control power module, and the second terminal of the second secondary winding NS2 is connected to digital ground GND. This part is set to digital ground GND.

[0050] In addition, in flyback switching power supply circuits, the main control power module is usually electrically connected to the third terminal COMP of the controller. This is used to feed back the voltage output by the flyback switching power supply to the controller, thereby realizing closed-loop control of the output voltage of the flyback switching power supply. Based on the magnitude of the output voltage of the flyback switching power supply, the controller controls the switching frequency and duration of the primary-side switch, thereby achieving stable voltage output. This is a commonly used technique in flyback switching power supplies and belongs to existing technology, so it will not be elaborated here.

[0051] Based on the above embodiments, this application uses transformers to isolate the power supply circuits of each module, which can reduce interference between modules. Furthermore, to reduce noise at the output of the switching power supply, the power supply circuits of each module need to be processed. Specifically, firstly, a first Y capacitor CY1 is used to electrically connect the switching power supply ground MGND and the analog ground AGND; secondly, a second Y capacitor CY2 is used to electrically connect the 485 ground G485 and the digital ground GND; and then a third Y capacitor CY3 is used to electrically connect the digital ground GND and the analog ground AGND.

[0052] This application reduces noise at the output of the switching power supply by processing various grounds, thereby reducing power supply ripple for each module. The application employs a two-stage filtering process. The first stage involves electrically connecting the switching power supply ground MGND to the analog ground AGND via a first Y capacitor CY1 on the primary side of the transformer, introducing noise from the primary side of the transformer to the analog ground AGND. The second stage involves first introducing noise from the 485 ground G485 to the digital ground GND via a second Y capacitor CY2 on the secondary side of the transformer, and then introducing the noise from both the 485 ground G485 and the digital ground GND to the analog ground AGND via a third Y capacitor CY3. The analog ground AGND can be electrically connected to earth, effectively introducing noise from the switching power supply circuit to earth, thus reducing noise at the output of the switching power supply.

[0053] It should be noted that, in order to reduce interference with communication, the 485 communication module is usually placed far away from the analog ground AGND in the PCB circuit board of smart meters. Therefore, the noise of the 485 ground G485 needs to be introduced into the digital ground GND first, and then the noise of the digital ground GND needs to be introduced into the analog ground AGND.

[0054] In this embodiment, the 485 power module, main control power module, metering power module, and controller are isolated by the first primary winding, second primary winding, third primary winding, first secondary winding, and second secondary winding of the transformer, which reduces interference between the modules. On the primary side of the transformer, the switching power supply ground is electrically connected to the analog ground through the first Y capacitor, introducing the noise from the primary side of the transformer to the analog ground. On the secondary side of the transformer, the noise from the 485 ground (G485) is first introduced to the digital ground through the second Y capacitor, and then the noise from both the 485 ground and the digital ground is introduced to the analog ground through the third Y capacitor. This allows the noise in the switching power supply circuit to be introduced to the ground, thereby reducing the noise at the output of the switching power supply and thus reducing the ripple of the output voltage.

[0055] In one possible embodiment, the withstand voltage of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 is not less than 4KV.

[0056] Y capacitors are a type of safety capacitor, also known as high-voltage ceramic capacitors. They are widely used in various applications and can prevent electric shock or personal safety when the capacitor fails.

[0057] In this embodiment of the application, in order to achieve a better effect of reducing the noise at the output of the switching power supply, the selected Y capacitor has a high withstand voltage value. The withstand voltage values ​​of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 are all not lower than 4KV. For example, the withstand voltage values ​​of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 can be 4KV, 4.5KV, or 5KV.

[0058] In one possible embodiment, the capacitance values ​​of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 are all 1nF or 470pF.

[0059] The transformer in this application is usually a high-frequency transformer. In order to effectively filter out high-frequency noise, it is necessary to select Y capacitors with high withstand voltage and low capacitance. In one example, a 1nF Y capacitor is selected, that is, the capacitance values ​​of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 are all 1nF; or, a 470pF Y capacitor is selected, that is, the capacitance values ​​of the first Y capacitor CY1, the second Y capacitor CY2, and the third Y capacitor CY3 are all 470pF.

[0060] In one possible embodiment, see Figure 2 , Figure 2 A circuit diagram of a switching power supply circuit provided in an embodiment of this application is shown below. Figure 2As shown, the 485 power supply module 100 may include: a first rectifier submodule, a first filter submodule, and a first voltage regulator submodule; the first rectifier submodule includes: a first resistor R1, a first capacitor C1, and a first diode D1; the first filter submodule includes: a first polarized capacitor CE1; the first voltage regulator submodule includes: a second capacitor C2, a second resistor R2, a third capacitor C3, a fourth capacitor C4, and a first voltage regulator U1.

[0061] The first end of the first resistor R1 is electrically connected to the first end of the first secondary winding NS1 and the positive terminal of the first diode D1, and the second end of the first resistor R1 is electrically connected to the first end of the first capacitor C1.

[0062] The second terminal of the first capacitor C1 is electrically connected to the negative terminal of the first diode D1, the positive terminal of the first polarized capacitor CE1, the first terminal of the second capacitor C2, the first terminal of the second resistor R2, and the input terminal VIN of the first voltage regulator U1.

[0063] The output terminal VOUT of the first voltage regulator U1 is electrically connected to the first terminal of the third capacitor C3 and the first terminal of the fourth capacitor C4, respectively, to output the 485 power supply voltage V485.

[0064] The negative terminal of the first polarized capacitor CE1, the second terminal of the second capacitor C2, the second terminal of the second resistor R2, the third terminal GND of the first voltage regulator U1, the second terminal of the third capacitor C3, and the second terminal of the fourth capacitor C4 are all connected to the 485 ground G485.

[0065] In this embodiment, the 485 power supply module is used to convert the voltage connected to the first secondary winding NS1 into a 485 power supply voltage V485 to power the 485 communication module. The first voltage regulator U1 is used to perform voltage conversion, for example, converting 12V to 5V.

[0066] In one possible embodiment, see Figure 2 The main control power module 200 may include: a second rectifier submodule and a second filter submodule; the second rectifier submodule includes: a third resistor R3, a fifth capacitor C5 and a second diode D2; the second filter submodule includes: a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a second polarized capacitor CE2 and a first inductor L1.

[0067] The first end of the third resistor R3 is electrically connected to the positive terminal of the second diode D2 and the first end of the second secondary winding NS2, respectively, and the second end of the third resistor R3 is electrically connected to the first end of the fifth capacitor C5.

[0068] The second terminal of the fifth capacitor C5 is electrically connected to the negative terminal of the second diode D2, the first terminal of the sixth capacitor C6, the first terminal of the seventh capacitor C7, the positive terminal of the second polarized capacitor CE2, the first terminal of the first inductor L1, and the third terminal COMP of the controller 400.

[0069] The second terminal of the first inductor L1 is electrically connected to the first terminal of the eighth capacitor C8 and the first terminal of the ninth capacitor C9, respectively, for outputting the main control power supply voltage VCC.

[0070] The second terminal of the sixth capacitor C6, the second terminal of the seventh capacitor C7, the negative terminal of the second polarity capacitor CE2, the second terminal of the eighth capacitor C8, and the second terminal of the ninth capacitor C9 are all connected to digital ground GND.

[0071] In this embodiment, the main control power module is only used to filter the voltage connected to the second secondary winding NS2 and convert it into the main control power supply voltage VCC. When it is necessary to power the subsequent MCU (Microcontroller Unit), the main control power supply voltage VCC usually needs to be stepped down again to convert it into the required voltage. For example, the main control power supply voltage VCC is converted to 3.3V through an LDO (Low-dropout regulator) to provide power to the MCU.

[0072] In addition, the second terminal of the fifth capacitor C5 is electrically connected to the third terminal COMP of the controller 400. Its function is to feed back the voltage output of the second secondary winding NS2 to the controller to realize closed-loop control of the voltage output of the flyback switching power supply. According to the magnitude of the voltage output of the flyback switching power supply, the controller controls the switching frequency and duration of the primary side switch, thereby achieving stable voltage output.

[0073] In one possible embodiment, see Figure 2 The metering power supply module 300 may include: a third rectifier submodule, a third filter submodule, and a second voltage regulator submodule; the third rectifier submodule includes: a fourth resistor R4, a tenth capacitor C10, and a third diode D3; the third filter submodule includes: a third polarized capacitor CE3; the second voltage regulator submodule includes: an eleventh capacitor C11, a twelfth capacitor C12, and a second voltage regulator U2.

[0074] The first terminal of the tenth capacitor C10 is electrically connected to the positive terminal of the third diode D3 and the second terminal of the third primary winding NP3, respectively. The second terminal of the tenth capacitor C10 is electrically connected to the first terminal of the fourth resistor R4.

[0075] The second terminal of the fourth resistor R4 is electrically connected to the negative terminal of the third diode D3, the positive terminal of the third polarized capacitor CE3, the first terminal of the eleventh capacitor C11, and the input terminal VIN of the second voltage regulator U2.

[0076] The output terminal VOUT of the second voltage regulator U2 is electrically connected to the first terminal of the twelfth capacitor C12, and is used to output the metering power supply voltage DVDD.

[0077] The negative terminal of the third polarity capacitor CE3, the second terminal of the eleventh capacitor C11, the second terminal of the twelfth capacitor C12, and the third terminal GND of the second voltage regulator U2 are all connected to analog ground AGND.

[0078] In this embodiment, the metering power supply module converts the voltage connected to the third primary winding NP3 into the metering power supply voltage DVDD to power the metering module. The second voltage regulator U2 is used to perform voltage conversion, for example, converting 12V to 5V.

[0079] In one possible embodiment, the controller is model 8254T / Q, and the first voltage regulator U1 is model CJ78L05.

[0080] The controller in this application can be model 8254T / Q. The 8254T / Q is a low-power standby offline pulse-width modulation converter that integrates a pulse-width modulation (PWM) controller and power MOSFETs. It also provides comprehensive protection functions, such as automatic self-recovery, overload protection, overvoltage protection, short-circuit protection, and soft-start. It is commonly used in flyback switching power supplies.

[0081] The 8254T / Q includes multiple pins such as SW, COMP, VDD, GND, and CS. Among them, SW is the switching node; COMP is the feedback pin; VDD is the power input pin; GND is the ground pin; and CS is the MOSFET source and current limit pin.

[0082] The first voltage regulator U1 is model CJ78L05. CJ78L05 is a three-terminal voltage regulator that provides a wide range of input voltages and can convert an input voltage of 7V to 20V into an output voltage of 5V.

[0083] In one possible embodiment, the second voltage regulator U2 is model CJ78L05.

[0084] The second voltage regulator U2 is model CJ78L05. CJ78L05 is a three-terminal voltage regulator that provides a wide range of input voltages and can convert an input voltage of 7V to 20V into an output voltage of 5V.

[0085] This application also provides a flyback switching power supply, including: the switching power supply circuit as described above.

[0086] The flyback switching power supply in this application is a flyback switching power supply used in smart meters. It needs to provide power to the communication module, main control module, and metering module.

[0087] This application also provides an electronic device, including: a flyback switching power supply as described above.

[0088] The electronic device in this application may be a smart meter.

[0089] Finally, it should be noted that the above embodiments are merely specific implementations 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 covered 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 by comprising: The switching power supply circuit includes: a transformer, a 485 power module, a main control power module, a metering power module, a controller, a first Y capacitor, a second Y capacitor, and a third Y capacitor; wherein, the transformer includes a first primary winding, a second primary winding, a third primary winding, a first secondary winding, and a second secondary winding. The first end of the first primary winding is used to connect to the input voltage, and the second end of the first primary winding is electrically connected to the first end of the controller; the first end of the second primary winding is connected to the switching power supply ground, and the second end of the second primary winding is electrically connected to the second end of the controller; the first end of the third primary winding is connected to analog ground, and the second end of the third primary winding is electrically connected to the input end of the metering power supply module; the first end of the first secondary winding is electrically connected to the input end of the 485 power supply module, and the second end of the first secondary winding is connected to the 485 ground; the first end of the second secondary winding is electrically connected to the input end of the main control power supply module, and the second end of the second secondary winding is connected to digital ground; the main control power supply module is electrically connected to the third end of the controller; The switching power supply ground and the analog ground are electrically connected through the first Y capacitor; The 485 ground and the digital ground are electrically connected through the second Y capacitor, and the digital ground and the analog ground are electrically connected through the third Y capacitor.

2. The switching power supply circuit according to claim 1, characterized by The withstand voltage of the first Y capacitor, the second Y capacitor, and the third Y capacitor is not less than 4KV.

3. The switching power supply circuit according to claim 1, characterized by The capacitance values ​​of the first Y capacitor, the second Y capacitor, and the third Y capacitor are all 1nF or 470pF.

4. The switching power supply circuit according to claim 1, characterized by The 485 power supply module includes: a first rectifier submodule, a first filter submodule, and a first voltage regulator submodule; the first rectifier submodule includes: a first resistor, a first capacitor, and a first diode; the first filter submodule includes: a first polarized capacitor; the first voltage regulator submodule includes: a second capacitor, a second resistor, a third capacitor, a fourth capacitor, and a first voltage regulator; The first end of the first resistor is electrically connected to the first end of the first secondary winding and the positive terminal of the first diode, and the second end of the first resistor is electrically connected to the first end of the first capacitor. The second terminal of the first capacitor is electrically connected to the negative terminal of the first diode, the positive terminal of the first polarized capacitor, the first terminal of the second capacitor, the first terminal of the second resistor, and the input terminal of the first voltage regulator. The output terminal of the first voltage regulator is electrically connected to the first terminal of the third capacitor and the first terminal of the fourth capacitor, respectively, for outputting 485 power supply voltage; The negative terminal of the first polarized capacitor, the second terminal of the second capacitor, the second terminal of the second resistor, the third terminal of the first voltage regulator, the second terminal of the third capacitor, and the second terminal of the fourth capacitor are all connected to 485 ground.

5. The switching power supply circuit according to claim 1, characterized by The main control power supply module includes: a second rectifier submodule and a second filter submodule; the second rectifier submodule includes: a third resistor, a fifth capacitor and a second diode; the second filter submodule includes: a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second polarized capacitor and a first inductor; The first end of the third resistor is electrically connected to the positive terminal of the second diode and the first end of the second secondary winding, respectively; the second end of the third resistor is electrically connected to the first end of the fifth capacitor. The second terminal of the fifth capacitor is electrically connected to the negative terminal of the second diode, the first terminal of the sixth capacitor, the first terminal of the seventh capacitor, the positive terminal of the second polarized capacitor, the first terminal of the first inductor, and the third terminal of the controller. The second end of the first inductor is electrically connected to the first end of the eighth capacitor and the first end of the ninth capacitor, respectively, for outputting the main control power supply voltage; The second terminal of the sixth capacitor, the second terminal of the seventh capacitor, the negative terminal of the second polarized capacitor, the second terminal of the eighth capacitor, and the second terminal of the ninth capacitor are all connected to digital ground.

6. The switching power supply circuit according to claim 1, characterized by The metering power supply module includes: a third rectifier submodule, a third filter submodule, and a second voltage regulator submodule; the third rectifier submodule includes: a fourth resistor, a tenth capacitor, and a third diode; the third filter submodule includes: a third polarized capacitor; the second voltage regulator submodule includes: an eleventh capacitor, a twelfth capacitor, and a second voltage regulator; The first terminal of the tenth capacitor is electrically connected to the positive terminal of the third diode and the second terminal of the third primary winding, respectively, and the second terminal of the tenth capacitor is electrically connected to the first terminal of the fourth resistor. The second end of the fourth resistor is electrically connected to the negative terminal of the third diode, the positive terminal of the third polarized capacitor, the first end of the eleventh capacitor, and the input terminal of the second voltage regulator. The output terminal of the second voltage regulator is electrically connected to the first terminal of the twelfth capacitor, and is used to output the metering power supply voltage; The negative terminal of the third polarity capacitor, the second terminal of the eleventh capacitor, the second terminal of the twelfth capacitor, and the third terminal of the second voltage regulator are all connected to analog ground.

7. The switching power supply circuit according to claim 4, characterized by The controller is model 8254T / Q, and the first voltage regulator is model CJ78L05.

8. The switching power supply circuit according to claim 6, characterized in that, The second voltage regulator is model CJ78L05.

9. A flyback switching power supply, characterized by include: The switching power supply circuit as described in any one of claims 1-8.

10. An electronic device, comprising: include: The flyback switching power supply as described in claim 9.

Images