A flyback switching power supply

Abstract

This invention discloses a flyback switching power supply, which includes a circuit board and multiple components mounted on the circuit board. The components are functionally divided into a main circuit, a self-feeding coil circuit, and a control circuit. The main circuit is connected to both the self-feeding coil circuit and the control circuit. The main circuit includes a first capacitor, a second capacitor, a first resistor, a third capacitor, a first diode, a switching transistor, a second resistor, a fourth capacitor, a third resistor, a fourth resistor, a fifth capacitor, a fifth resistor, and a first winding of a transformer. The length of the control signal connection between the third resistor and the sixth terminal of the control chip does not exceed one-twentieth of the high-frequency interference wavelength. Copper foil is laid between the second terminal of the first winding of the transformer and the first terminal of the switching transistor. The width of the sampling line between the fifth terminal of the control chip and the fifth resistor is 0.25mm-0.3mm. This invention enables a reasonable layout of all components, ensuring reliable and efficient operation while improving performance.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and more particularly to a flyback switching power supply. Background Technology

[0002] Switching power supplies are widely used because they can generate stable DC output voltage and have high conversion efficiency. A switching power supply mainly consists of a controller and power transistors. The controller controls the switching on and off of the power transistors to generate a stable DC output voltage.

[0003] For flyback switching power supplies, improper PCB layout and routing can lead to the following problems: Inappropriate handling of the transformer primary circuit can generate high-frequency interference above 76MHz, causing electromagnetic compatibility (EMC) tests to fail. Inadequate layout and routing of critical components and signals on the transformer primary side can degrade the overall circuit performance, causing instability and, in severe cases, malfunction. Summary of the Invention

[0004] This invention provides a flyback switching power supply to achieve a reasonable layout of all components in the flyback switching power supply, ensuring reliable and efficient operation of the switching power supply and improving its performance.

[0005] According to one aspect of the present invention, a flyback switching power supply is provided, comprising: a circuit board and a plurality of components disposed on the circuit board; the plurality of components are functionally divided into a main circuit, a self-feeding coil circuit and a control circuit, wherein the main circuit is connected to the self-feeding coil circuit and the control circuit respectively;

[0006] The self-feeding coil circuit includes a control chip, and the main circuit includes a first capacitor, a second capacitor, a first resistor, a third capacitor, a first diode, a switching transistor, a second resistor, a fourth capacitor, a third resistor, a fourth resistor, a fifth capacitor, a fifth resistor, and a transformer first winding;

[0007] The control chip, the fifth capacitor, the fifth resistor, the third resistor, the fourth resistor, and the first capacitor are arranged sequentially along a first direction; the fourth capacitor, the second resistor, and the first winding of the transformer are arranged sequentially along a second direction; the switching transistor, the first diode, and the first resistor are arranged sequentially along the first direction and parallel to the fifth resistor; the second capacitor and the third capacitor are arranged sequentially along the second direction and parallel to the fourth capacitor; wherein the first direction and the second direction are perpendicular to each other.

[0008] The length of the connection between the third resistor and the sixth terminal of the control chip shall not exceed one-twentieth of the high-frequency interference wavelength. Copper foil shall be laid between the second terminal of the first winding of the transformer and the first pole of the switching transistor. The width of the sampling line between the fifth terminal of the control chip and the fifth resistor shall be 0.25mm-0.3mm.

[0009] Optionally, the main circuit is located in a first region on the circuit board, the self-feeding coil circuit is located in a second region on the circuit board, and the control circuit is located in a third region on the circuit board. The third region and the second region are arranged sequentially along a second direction, and the first region is parallel to the arrangement direction of the second region and the third region.

[0010] Optionally, the first capacitor, the second capacitor, the first resistor, and the first terminal of the third capacitor are connected and then connected to the first terminal of the first winding of the transformer. The second terminal of the first capacitor is grounded, the second terminal of the second capacitor is grounded, the first resistor and the second terminal of the third capacitor are connected and then connected to the cathode of the first diode, the anode of the first diode is connected to the second terminal of the first winding of the transformer, the first terminal of the switching transistor is connected to the anode of the first diode, the control terminal of the switching transistor is connected to the first terminals of the third resistor and the fourth resistor respectively, the second terminal of the fourth resistor is grounded, the first terminal of the third resistor is connected to the sixth terminal of the control chip, the second terminal of the switching transistor is connected to the first terminals of the fifth capacitor and the fifth resistor, the fifth capacitor and the second terminal of the fifth resistor are connected and then grounded, the first terminal of the fifth capacitor is connected to the first terminal of the control chip, and the second resistor and the fourth capacitor are connected in series between the first and second terminals of the switching transistor.

[0011] Optionally, the self-feeding coil circuit further includes a second diode, a sixth capacitor, a sixth resistor, a seventh capacitor, an eighth capacitor, a seventh resistor, an eighth resistor, a ninth resistor, a ninth capacitor, and a second winding of the transformer;

[0012] The eighth resistor, the sixth capacitor, and the sixth resistor are arranged sequentially along the first direction; the seventh resistor, the eighth capacitor, and the seventh capacitor are arranged sequentially along the second direction; and the ninth capacitor, the ninth resistor, and the second winding of the transformer are arranged sequentially along the second direction.

[0013] Optionally, the anode of the second diode is connected to the second end of the second winding of the transformer, the cathode of the second diode is connected to the first ends of the seventh capacitor, the eighth capacitor, the seventh resistor, and the eighth resistor, respectively, the second ends of the seventh capacitor, the eighth capacitor, and the seventh resistor are connected to the first end of the second winding of the transformer, the sixth capacitor and the sixth resistor are connected in series between the anode and the cathode of the second diode, the second end of the eighth resistor is connected to the first end of the ninth resistor and the first end of the ninth capacitor, respectively, and then connected to the third end of the control chip, and the second end of the ninth resistor and the second end of the ninth capacitor are connected to the fourth end of the control chip.

[0014] Optionally, the control circuit includes a tenth capacitor, an eleventh capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor, a transistor, a thirteenth resistor, and a fourteenth resistor;

[0015] The thirteenth resistor, the fourteenth resistor, the transistor, and the twelfth resistor are arranged sequentially along the first direction, and the eleventh resistor, the tenth capacitor, the eleventh capacitor, and the tenth resistor are arranged sequentially along the second direction.

[0016] Optionally, the first terminal of the tenth capacitor is connected to the eighth terminal of the control chip, the second terminal of the tenth capacitor is grounded, the first terminal of the eleventh capacitor is connected to the second terminal of the control chip, the second terminal of the eleventh capacitor is connected to the first terminal of the tenth resistor, the second terminal of the tenth resistor is connected to the fourth terminal of the control chip, the first terminal of the eleventh resistor is connected to the seventh terminal of the control chip, the second terminal of the eleventh resistor is connected to the second terminal of the twelfth resistor, the first terminal of the twelfth resistor is connected to the first power supply terminal, the second terminal of the twelfth resistor is connected to the collector of the transistor, the fourteenth resistor is connected between the base and emitter of the transistor, the first terminal of the thirteenth resistor is connected to the base of the transistor, and the second terminal of the thirteenth resistor is connected to the power supply enable terminal.

[0017] Optionally, it also includes a differential mode loop, which includes a fifteenth resistor, a twelfth capacitor, a third diode, a thirteenth capacitor, a fourteenth capacitor, and a third winding of the transformer;

[0018] The fifteenth resistor, the third diode, and the thirteenth capacitor are arranged sequentially along the first direction, and the third winding of the transformer, the twelfth capacitor, and the fourteenth capacitor are arranged sequentially along the second direction.

[0019] Optionally, the anode of the third diode is connected to the first end of the third winding of the transformer, the cathode of the third diode is connected to the first end of the thirteenth capacitor and the first end of the fourteenth capacitor, the fifteenth resistor and the twelfth capacitor are connected in series between the anode and cathode of the third diode, the second end of the thirteenth capacitor and the second end of the fourteenth capacitor are connected and then connected to the second end of the third winding of the transformer, the first end of the fourteenth capacitor is connected to the second power supply terminal, and the second end of the fourteenth capacitor is grounded.

[0020] Optionally, the differential mode loop is located in a fourth region, which is parallel to the first region.

[0021] The flyback switching power supply in this embodiment of the invention includes a circuit board and multiple components disposed on the circuit board. The multiple components are functionally divided into a main circuit, a self-feeding coil circuit, and a control circuit. The main circuit is connected to both the self-feeding coil circuit and the control circuit. The self-feeding coil circuit includes a control chip. The main circuit includes the control chip, a first capacitor, a second capacitor, a first resistor, a third capacitor, a first diode, a switching transistor, a second resistor, a fourth capacitor, a third resistor, a fourth resistor, a fifth capacitor, a fifth resistor, and a first winding of a transformer. The control chip, the fifth capacitor, the fifth resistor, the third resistor, the fourth resistor, and the first capacitor are connected along a first direction. The components are arranged sequentially: the fourth capacitor, the second resistor, and the first winding of the transformer are arranged sequentially along the second direction; the switching transistor, the first diode, and the first resistor are arranged sequentially along the first direction and parallel to the fifth resistor; the second capacitor and the third capacitor are arranged sequentially along the second direction and parallel to the fourth capacitor; wherein the first and second directions are perpendicular to each other; the connection length of the control signal between the third resistor and the sixth terminal of the control chip does not exceed one-twentieth of the high-frequency interference wavelength; copper foil is laid between the second terminal of the first winding of the transformer and the first terminal of the switching transistor; the width of the sampling line between the fifth terminal of the control chip and the fifth resistor is 0.25mm-0.3mm. This invention's technical solution, through reasonable layout and wiring of components, makes full use of each component, resulting in a stable and manufacturable solution. It solves the problems of high-frequency interference, signal crosstalk, sampling accuracy, and manufacturing process issues commonly encountered in existing technologies, saving production costs, ensuring reliable and efficient operation of the switching power supply, and improving the working performance of the switching power supply.

[0022] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the component layout of a flyback switching power supply according to an embodiment of the present invention;

[0025] Figure 2 This is a circuit schematic diagram of a flyback switching power supply according to an embodiment of the present invention;

[0026] Figure 3 This is a circuit layout diagram of a flyback switching power supply according to an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the component layout of another flyback switching power supply according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the component layout of another flyback switching power supply provided according to an embodiment of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] Figure 1This is a schematic diagram of the component layout of a flyback switching power supply according to an embodiment of the present invention. Figure 2 This is a circuit schematic diagram of a flyback switching power supply according to an embodiment of the present invention, for reference. Figure 1 and Figure 2 This invention provides a flyback switching power supply, which includes a circuit board and multiple components disposed on the circuit board. The multiple components are functionally divided into a main circuit 10, a self-feeding coil circuit 20, and a control circuit 30. The main circuit 10 is connected to both the self-feeding coil circuit 20 and the control circuit 30. The self-feeding coil circuit 20 includes a control chip IC201. The main circuit 10 includes a first capacitor E201, a second capacitor C205, a first resistor R204, a third capacitor C206, a first diode D203, a switching transistor M201, a second resistor R205, a fourth capacitor C210, a third resistor R206, a fourth resistor R209, a fifth capacitor C212, a fifth resistor R211, and a first winding of a transformer T201. The control chip IC201, the fifth capacitor C212, the fifth resistor R211, the third resistor R206, the fourth resistor R209, the fifth capacitor C212, the fifth resistor R211, the fifth resistor R209, the fifth resistor R211, the fifth resistor R211, the fifth resistor R209, the fifth resistor R211, the fifth resistor R212, the fifth resistor R211, the fifth resistor R206, the fifth resistor R211, the fifth resistor R211, the fifth resistor R212, the fifth resistor R211, the fifth resistor R209, the fifth resistor R211, the fifth resistor R211, the fifth resistor R211, the fifth resistor R212 ... 209. The first capacitor E201 is arranged sequentially along the first direction X; the fourth capacitor C210, the second resistor R205, and the first winding of the transformer T201 are arranged sequentially along the second direction Y; the switch M201, the first diode D203, and the first resistor R204 are arranged sequentially along the first direction X and parallel to the fifth resistor R211; the second capacitor C205 and the third capacitor C206 are arranged sequentially along the second direction Y and parallel to the fourth capacitor C210; wherein, the first direction X and the second direction Y are perpendicular to each other; the connection length of the control signal between the third resistor R206 and the sixth terminal 6 of the control chip IC201 does not exceed one-twentieth of the high-frequency interference wavelength; copper foil is laid between the second terminal 2 of the first winding of the transformer T201 and the first pole of the switch M201; the width of the sampling line between the fifth terminal 5 of the control chip IC201 and the fifth resistor R211 is 0.25mm-0.3mm.

[0032] Specifically, the primary side of a flyback switching power supply consists of three circuits: the main circuit 10, the self-feeding coil circuit 20, and the control circuit 30. It is essential to ensure that these three circuits do not interfere with each other. All components in the main circuit 10 should be placed on the same plane, arranged according to the function of each component, and the wiring should be as short as possible.

[0033] The switching transistor M201 directly switches the connection between the second terminal 2 of the first winding of transformer T201 and GND. Therefore, the switching transistor M201 needs to be placed close to the second terminal 2 of the first winding of transformer T201. The edge of the switching transistor M201 needs to be at least 0.7mm away from the pin pads of transformer T201. Because transformer T201 is a high-voltage device, the solder paste needs to be spread out to ensure a firm solder joint and good solder adhesion on the pads. The current-carrying capacity of the connection line between the first terminal of switching transistor M201 and the second terminal 2 of the first winding of transformer T201 needs to be 30% greater than the actual circuit current, and the trace should be as short as possible. For example, switching transistor M201 can be a MOSFET, with the first terminal being the drain and the second terminal being the source. The fourth resistor R209 is used to release the capacitor voltage between the drain and source of switching transistor M201, and at the same time pulls down the voltage at the control terminal to prevent malfunction of switching transistor M201. The fourth resistor R209 should be placed as close as possible to the control terminal and source pins of switching transistor M201. The grounding of the fourth resistor R209 needs to be connected to the grounding terminal of the fifth resistor R211 with the shortest possible distance. The third resistor R206 is a current-limiting resistor and is placed next to the fourth resistor R209. It is important to note that the length of the connection between the third resistor R206 and the control chip IC201 should not exceed 10mm, and it should be grounded. This is because the switching transistor M201 is controlled at a frequency of 100kHz. Longer wires will introduce parasitic inductance and capacitance, which will affect the normal operation of the switching transistor M201. Grounding is to prevent 100kHz frequency crosstalk to other signals. The connection length between the third resistor R206 and the sixth terminal (6) of the control chip IC201 should be as short as possible, not exceeding one-twentieth of the high-frequency interference wavelength. The frequency range of the high-frequency interference wave is 70MHz-80MHz. The first resistor R204, the third capacitor C206, and the first diode D203 are placed close together. This placement ensures that the reverse voltage generated by the turn-off of the switch M201 at the input of the transformer T201 quickly returns to its source. They should be placed as close as possible between the transformer T201 and the switch M201. Due to the large energy, the loop area should be as small as possible. From the switch M201 to the first diode D203, then to the first resistor R204 and the third capacitor C206, a large copper trace should not be used; the trace width should be 0.5mm. Because this network does not have a large current, a large copper trace will increase radiation, introduce noise, and affect EMC testing. The second resistor R205 and the fourth capacitor C210 are used to absorb the switching noise of the switch M201. They should be bypassed and not directly connected to the power loop. A large copper trace should not be used; a 0.25mm trace width is sufficient. The fifth resistor, R211, can be used as a sampling resistor. It should be placed close to the source of the switching transistor M201, and the trace length needs to be short. The current carrying capacity of the trace width needs to be 30% greater than the actual operating current. The ground of the fifth resistor R211 should be directly connected to the GND terminal of the first capacitor E201, while also considering the current carrying capacity of the trace width.It's important to note that while ensuring sufficient current carrying capacity, the copper plating must also consider heat dissipation for the pads. The first capacitor, E201, can be an electrolytic capacitor, and there are electrolytic capacitor pads. The power input terminal VPP-CTL of the reverse-amplified switching power supply needs to pass through the first capacitor E201 and the second capacitor C205 before connecting to the transformer pins. Furthermore, the fifth capacitor C212 needs to be placed between the fifth resistor R211 and the control chip IC201, perpendicular to the orientation of the fifth resistor R211, to reduce noise coupling and prevent false protection. The power input terminal VPP-CTL of the reverse-amplified switching power supply provides power to the transformer T201 and the control chip IC201. To reduce standby power consumption, this power supply can control the shutdown of the transformer T201 and the control chip IC201.

[0034] The sampling line from control chip IC201 to the fifth resistor R211 passes through the fifth capacitor C212 and connects to the underside of the sampling resistor. It's important to note that the width of the sampling line between the fifth terminal 5 of control chip IC201 and the fifth resistor R211 should be 0.25mm-0.3mm. The sampling line should not be too wide; preferably 0.254mm. It must be led out from the pad under the fifth resistor R211. This ensures the shortest possible connection to the resistor body pin and avoids the influence of noise introduced by the pad on the sampling line. This is because component pads are typically extended outwards. If the sampling line is connected from the outside of the pad, it will first connect to the large copper foil of the pad. The sampling line also needs to avoid copper plating, as copper plating increases radiation and introduces interference. Voltage sampling is generally a high-impedance circuit. A key characteristic is that when common-mode interference signals are introduced, the high impedance of the sampling segment easily causes common-mode to differential-mode conversion, thus affecting the sampling function. Therefore, it's crucial to avoid running a single sampling line on the surface layer and keep the trace as short as possible.

[0035] The flyback switching power supply in this embodiment of the invention includes a circuit board and multiple components disposed on the circuit board. The multiple components are functionally divided into a main circuit, a self-feeding coil circuit, and a control circuit. The main circuit is connected to both the self-feeding coil circuit and the control circuit. The self-feeding coil circuit includes a control chip. The main circuit includes the control chip, a first capacitor, a second capacitor, a first resistor, a third capacitor, a first diode, a switching transistor, a second resistor, a fourth capacitor, a third resistor, a fourth resistor, a fifth capacitor, a fifth resistor, and a first winding of a transformer. The control chip, the fifth capacitor, the fifth resistor, the third resistor, the fourth resistor, and the first capacitor are connected along a first direction. The components are arranged sequentially: the fourth capacitor, the second resistor, and the first winding of the transformer are arranged sequentially along the second direction; the switching transistor, the first diode, and the first resistor are arranged sequentially along the first direction and parallel to the fifth resistor; the second capacitor and the third capacitor are arranged sequentially along the second direction and parallel to the fourth capacitor; wherein the first and second directions are perpendicular to each other; the connection length of the control signal between the third resistor and the sixth terminal of the control chip does not exceed one-twentieth of the high-frequency interference wavelength; copper foil is laid between the second terminal of the first winding of the transformer and the first terminal of the switching transistor; the width of the sampling line between the fifth terminal of the control chip and the fifth resistor is 0.25mm-0.3mm. This invention's technical solution, through reasonable layout and wiring of components, makes full use of each component, resulting in a stable and manufacturable solution. It solves the problems of high-frequency interference, signal crosstalk, sampling accuracy, and manufacturing process issues commonly encountered in existing technologies, saving production costs, ensuring reliable and efficient operation of the switching power supply, and improving the working performance of the switching power supply.

[0036] Figure 3 This is a circuit layout diagram of a flyback switching power supply according to an embodiment of the present invention; Reference Figure 3 Optionally, the main circuit 10 is located in the first region 100 on the circuit board, the self-feeding coil circuit 20 is located in the second region 200 on the circuit board, and the control circuit 30 is located in the third region 300 on the circuit board. The third region 300 and the second region 200 are arranged sequentially along the second direction Y, and the arrangement direction of the first region 100 is parallel to that of the second region 200 and the third region 300.

[0037] Continue to refer to Figure 2Optionally, the first terminals of the first capacitor E201, the second capacitor C205, the first resistor R204, and the third capacitor C206 are connected to the first terminal 1 of the first winding of the transformer T201. The second terminal of the first capacitor E201 is grounded to LV-GND, the second terminal of the second capacitor C205 is grounded to LV-GND, the second terminals of the first resistor R204 and the third capacitor C206 are connected to the cathode of the first diode D203, the anode of the first diode D203 is connected to the second terminal 2 of the first winding of the transformer T201, and the first electrode D of the switching transistor M201 is connected to the anode of the first diode D203. The control electrode of the switching transistor M201 is... The control terminal G is connected to the first terminals of the third resistor R206 and the fourth resistor R209 respectively. The second terminal of the fourth resistor R209 is grounded to LV-GND. The first terminal of the third resistor R206 is connected to the sixth terminal 6 of the control chip IC201. The second terminal S of the switching transistor M201 is connected to the first terminal of the fifth capacitor C212 and the fifth resistor R211. The fifth capacitor C212 is connected to the second terminal of the fifth resistor R211 and then grounded to LV-GND. The first terminal of the fifth capacitor C212 is connected to the first terminal of the control chip IC201. The second resistor R205 and the fourth capacitor C210 are connected in series between the first terminal D and the second terminal S of the switching transistor M201.

[0038] Continue to refer to Figure 1 Optionally, the self-feeding coil circuit 20 further includes a second diode D201, a sixth capacitor C201, a sixth resistor R201, a seventh capacitor C203, an eighth capacitor C202, a seventh resistor R202, an eighth resistor R207, a ninth resistor R213, a ninth capacitor C213, and a second winding of transformer T201; the eighth resistor R207, the sixth capacitor C201, and the sixth resistor R201 are arranged sequentially along the first direction X, the seventh resistor R202, the eighth capacitor C202, and the seventh capacitor C203 are arranged sequentially along the second direction Y, and the ninth capacitor C213, the ninth resistor R213, and the second winding of transformer T201 are arranged sequentially along the second direction Y.

[0039] Specifically, the self-feeding coil circuit 20 helps the control chip IC201 monitor the operating voltage of the primary side of transformer T201, and this circuit should be as short as possible. The second diode D201 can be a rectifier diode. Since the current in the self-feeding coil circuit 20 is alternating current, and the control chip IC201 can only acquire DC voltage, the second diode D201 is used for rectification. The second diode D201 is placed close to pin 4 of the second winding of transformer T201, ensuring a distance of ≥0.7mm from the transformer pins. The sixth capacitor C201 and the sixth resistor R201 are used to absorb voltage spikes during the operation of the second diode D201. The sixth capacitor C201 and the sixth resistor R201 are placed close to the second diode D201. Do not place a large copper foil between the sixth capacitor C201 and the sixth resistor R201. The seventh capacitor C203 and the eighth capacitor C202 are used for filtering and energy storage after rectification by the second diode D201, respectively. The seventh capacitor C203 and the eighth capacitor C202 need to be placed before the seventh resistor R202. The trace should first pass through the seventh capacitor C203, the eighth capacitor C202, and then the seventh resistor R202, which can be a load resistor. The shortest possible connection between the ground terminals of the seventh resistor R202, the eighth capacitor C202, and the seventh capacitor C203 and the primary side ground terminal of the transformer must be ensured. Finally, a hole should be drilled at the ground terminals of the eighth capacitor C202 and the seventh capacitor C203 to connect to the ground terminal of the first capacitor E201. The eighth resistor R207 can be a current-limiting resistor and should be placed in the middle of the circuit. The ninth resistor R213 and the ninth capacitor C213 are used for RC filtering and should be placed close to the pins of the control chip IC201. The trace must pass through RC filtering before connecting to the control chip IC201. The ground of the ninth resistor R213 and the ninth capacitor C213 should be directly connected to pin 4 of the control chip IC201. The connection from the second diode D201 to the control chip IC201 should not be too wide, but should be as short as possible. The trace should not exceed the width of the component pad while meeting the current carrying capacity requirements.

[0040] Continue to refer to Figure 2Optionally, the anode of the second diode D201 is connected to the second terminal 4 of the second winding of the transformer T201. The cathode of the second diode D201 is connected to the first terminals of the seventh capacitor C203, the eighth capacitor C202, the seventh resistor R202, and the eighth resistor R207, respectively. The second terminals of the seventh capacitor C203, the eighth capacitor C202, and the seventh resistor R202 are connected to the first terminal 5 of the second winding of the transformer T201. The sixth capacitor C201 and the sixth resistor R201 are connected in series between the anode and cathode of the second diode D201. The second terminal of the eighth resistor R207 is connected to the first terminal of the ninth resistor R213 and the first terminal of the ninth capacitor C213, respectively, and then connected to the third terminal 3 of the control chip IC201. The second terminal of the ninth resistor R213 and the second terminal of the ninth capacitor C213 are connected to the fourth terminal 4 of the control chip IC201.

[0041] Continue to refer to Figure 1 Optionally, the control circuit 30 includes a tenth capacitor C209, an eleventh capacitor C211, a tenth resistor R212, an eleventh resistor R210, a twelfth resistor R208, a transistor Q201, a thirteenth resistor R214, and a fourteenth resistor R215; the thirteenth resistor R214, the fourteenth resistor R215, the transistor Q201, and the twelfth resistor R208 are arranged sequentially along the first direction X, and the eleventh resistor R210, the tenth capacitor C209, the eleventh capacitor C211, and the tenth resistor R212 are arranged sequentially along the second direction Y.

[0042] Specifically, control loop 30 is the grounding loop for control chip IC201 and some discrete control devices. Terminals 4 (pin 4) and 5 (pin 5) of control chip IC201 should not be directly connected together. The tenth resistor R212 and the eleventh capacitor C211 are used for chip phase compensation; they should be placed close to control chip IC201. The eleventh resistor R210 can be a current-limiting resistor; its position is not critical, and it should be placed close to transistor Q201. The twelfth resistor R208 can be a pull-up resistor; it should be placed close to transistor Q201. Transistor Q201 is used to wake up control chip IC201, acting as a switch; its position is not critical, and it can be placed near control chip IC201 if space allows, or on the other side if space is limited. The fourteenth resistor R215 is used to release the voltage across the capacitor between the base (B) and emitter (E) of Q201, and also pulls the base (B) low to prevent transistor Q201 from malfunctioning; the fourteenth resistor R215 should be placed close to the base (B) and emitter (E) of Q201. The thirteenth resistor, R214, can be a current-limiting resistor and should be placed close to transistor Q201. Note that the ground terminal of control loop 30 is connected to the fourth terminal 4 of IC201, and then a hole is drilled to the ground terminal of the first capacitor E201. The fifth terminal 5 of control chip IC201 needs to be directly connected to the ground terminal of the fifth capacitor C212 and the fifth resistor R211. This reduces the sampling loop and minimizes interference to the sampling line. The tenth capacitor C209 should be placed close to the power pin of control chip IC201, and the trace should pass through the tenth capacitor C209 before connecting to the power pin of control chip IC201. Control chip IC201 and other loose components should not be placed inside the main circuit; they need to be placed outside the main circuit. Otherwise, they will be interfered with by the main circuit, causing control chip IC201 to malfunction.

[0043] Continue to refer to Figure 2 Optionally, the first terminal of the tenth capacitor C209 is connected to the eighth terminal 8 of the control chip IC201, and the second terminal of the tenth capacitor C209 is grounded (LV-GND). The first terminal of the eleventh capacitor C211 is connected to the second terminal 2 of the control chip IC201, and the second terminal of the eleventh capacitor C211 is connected to the first terminal of the tenth resistor R212. The second terminal of the tenth resistor R212 is connected to the fourth terminal 4 of the control chip IC201, and the first terminal of the eleventh resistor R210 is connected to the seventh terminal of the control chip IC201. 7. Connect the second end of the eleventh resistor R210 to the second end of the twelfth resistor R208. Connect the first end of the twelfth resistor R208 to the first power supply terminal LV-5V. Connect the second end of the twelfth resistor R208 to the collector C of the transistor Q201. Connect the fourteenth resistor R215 between the base B and emitter E of the transistor. Connect the first end of the thirteenth resistor R214 to the base B of the transistor Q201. Connect the second end of the thirteenth resistor R214 to the power supply enable terminal 15V-EN.

[0044] Figure 4 This is a schematic diagram of the component layout of another flyback switching power supply according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the component layout of another flyback switching power supply according to an embodiment of the present invention, for reference. Figure 4 and Figure 5 Optionally, it also includes a differential mode loop 40, which includes a fifteenth resistor R203, a twelfth capacitor C204, a third diode D202, a thirteenth capacitor E202, a fourteenth capacitor C207, and a third winding of transformer T201; the fifteenth resistor R203, the third diode D202, and the thirteenth capacitor E202 are arranged sequentially along the first direction X, and the third winding of transformer T201, the twelfth capacitor C204, and the fourteenth capacitor C207 are arranged sequentially along the second direction Y.

[0045] Specifically, the secondary output circuit of the transformer is a differential-mode loop. This will also generate high-frequency interference above 76MHz. Many products currently address this by adding a 100pF capacitor at the output, but this added capacitor negatively impacts the transformer's efficiency. Every component on both the primary and secondary sides of the transformer in a flyback switching power supply needs proper handling; otherwise, the power supply's performance will inevitably be affected.

[0046] The signals output from the first terminal 6 (pin 6) and the second terminal 7 (pin 7) of the third winding of transformer T201 should be routed as close as possible, with the loop as short as possible. Otherwise, high-frequency interference will occur, affecting EMC testing and severely impacting the normal operation of the circuit. The third diode D202 should be placed close to pin 6 of transformer T201, ensuring the distance from the component edge to the transformer pin is ≥0.7mm. The lead-in trace of the third diode D202 should be close to the ground terminal to effectively reduce differential-mode loops and couple out interference signals from the positive terminal. This is equivalent to having a capacitor in series between the two lines, which does not affect operating efficiency and eliminates both internal and external interference. This routing method ensures circuit performance while saving costs. The fifteenth resistor R203 and the twelfth capacitor C204 are used to absorb voltage spikes during the operation of the third diode D202. They should be placed close to the third diode D202, bypassing it, and the traces should not be covered with large copper foil. The grounding pin of transformer T201 needs to be connected to the grounding pin of the thirteenth capacitor E202 before being connected to the subsequent circuit. Pin 7 of transformer T201 is the main circuit; keep the trace as thick and short as possible. Pin 10 of transformer T201 is for EMC testing and does not need to be a wide trace. The thirteenth capacitor E202 can be an electrolytic capacitor. As a high-voltage component, E202 also requires solder expansion. This includes the first capacitor E201 on the primary side of transformer T201; the distance from the component edge to the solder expansion pad should be ≥0.7mm. The trace routing should also consider the heat dissipation of the component pads. The fourteenth capacitor C207 should be placed close to the thirteenth capacitor E202, maintaining a solder expansion distance of ≥0.7mm from the E202 pad. Note that the output of the third diode D202 should first pass through the thirteenth capacitor E202, then through the fourteenth capacitor C207, and finally be output to the external circuit. If the current carrying capacity of the line is sufficient, the trace width should not exceed the width of the pad pin. When the trace is wider than the pad, it is difficult to ensure the integrity of the pad, and poor soldering is easy to occur during soldering.

[0047] Finally, it's important to note the copper plating. If the transformer primary side is near-end grounded, the copper foil of the ground terminal T201 on the primary side of transformer T201 can be placed under the transformer pins. If transformer T201 is far-end grounded, do not place copper under the second diode D201, the sixth capacitor C201, the sixth resistor R201, the first diode D203, the third capacitor C206, and the first resistor R204. Also, the primary side of the transformer has significant switching noise and cannot be directly connected to the ground plane of other circuits. It needs to be led out from the ground terminal of the first capacitor E201, with a copper cut distance greater than 1mm. Do not place copper under the third diode D202, the twelfth capacitor C204, and the fifteenth resistor R203 on the secondary side of transformer T201. When placing copper, ensure that the ground plane is completely laid on layers close to the component faces. The outer copper foil of layer L3 goes through a via to the first capacitor E201, and then through a via into the transformer primary side circuit. This achieves effective overcapacitance and ground isolation, preventing the switching noise of the transformer primary side from affecting other circuits.

[0048] Copper plating should be applied to the secondary side of the transformer. The grounding terminal hole should be placed near the fourteenth capacitor, C207, as capacitor handling has been considered. No traces or copper plating should be run under the transformer. For tall components, a 2mm clearance should be provided for adhesive application.

[0049] Continue to refer to Figure 2 Optionally, the anode of the third diode D202 is connected to the first terminal 6 of the third winding of the transformer T201, the cathode of the third diode D202 is connected to the first terminal of the thirteenth capacitor E202 and the first terminal of the fourteenth capacitor C207, the fifteenth resistor R203 and the twelfth capacitor C204 are connected in series between the anode and cathode of the third diode D202, the second terminal of the thirteenth capacitor E202 and the second terminal of the fourteenth capacitor C207 are connected and then connected to the second terminal 7 of the third winding of the transformer T201, the first terminal of the fourteenth capacitor C207 is connected to the second power supply terminal 15V, and the second terminal of the fourteenth capacitor C207 is grounded to HV-GND.

[0050] Continue to refer to Figure 3 Optionally, the differential loop 40 is located in the fourth region 400, which is parallel to the first region 100.

[0051] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A flyback switching power supply, characterized by comprising: include: A circuit board and multiple components disposed on the circuit board; the multiple components are divided into a main circuit, a self-feeding coil circuit and a control circuit according to their functions, and the main circuit is connected to the self-feeding coil circuit and the control circuit respectively; The self-feeding coil circuit includes a control chip, and the main circuit includes a first capacitor, a second capacitor, a first resistor, a third capacitor, a first diode, a switching transistor, a second resistor, a fourth capacitor, a third resistor, a fourth resistor, a fifth capacitor, a fifth resistor, and a transformer first winding; The control chip, the fifth capacitor, the fifth resistor, the third resistor, the fourth resistor, and the first capacitor are arranged sequentially along a first direction; the fourth capacitor, the second resistor, and the first winding of the transformer are arranged sequentially along a second direction; the switching transistor, the first diode, and the first resistor are arranged sequentially along the first direction and parallel to the fifth resistor; the second capacitor and the third capacitor are arranged sequentially along the second direction and parallel to the fourth capacitor; wherein the first direction and the second direction are perpendicular to each other. The length of the connection between the third resistor and the sixth terminal of the control chip shall not exceed one-twentieth of the high-frequency interference wavelength. Copper foil shall be laid between the second terminal of the first winding of the transformer and the first pole of the switching transistor. The width of the sampling line between the fifth terminal of the control chip and the fifth resistor shall be 0.25mm-0.3mm. The fifth terminal of the control chip shall be grounded. The first capacitor, the second capacitor, the first resistor, and the first terminal of the third capacitor are connected and then connected to the first terminal of the first winding of the transformer. The second terminal of the first capacitor is grounded, and the second terminal of the second capacitor is grounded. The first resistor and the second terminal of the third capacitor are connected and then connected to the cathode of the first diode. The anode of the first diode is connected to the second terminal of the first winding of the transformer. The first terminal of the switching transistor is connected to the anode of the first diode. The control terminal of the switching transistor is connected to the first terminals of the third resistor and the fourth resistor, respectively. The second terminal of the fourth resistor is grounded. The second terminal of the third resistor is connected to the sixth terminal of the control chip. The second terminal of the switching transistor is connected to the first terminals of the fifth capacitor and the fifth resistor. The fifth capacitor and the second terminal of the fifth resistor are connected and then grounded. The first terminal of the fifth capacitor is connected to the first terminal of the control chip. The second resistor and the fourth capacitor are connected in series between the first and second terminals of the switching transistor.

2. The flyback switching power supply according to claim 1, characterized in that The main circuit is located in the first region on the circuit board, the self-feeding coil circuit is located in the second region on the circuit board, and the control circuit is located in the third region on the circuit board. The third region and the second region are arranged sequentially along the second direction, and the first region, the second region, and the third region are arranged adjacent to each other.

3. The flyback switching power supply of claim 1, wherein The self-feeding coil circuit also includes a second diode, a sixth capacitor, a sixth resistor, a seventh capacitor, an eighth capacitor, a seventh resistor, an eighth resistor, a ninth resistor, a ninth capacitor, and a second winding of a transformer; The eighth resistor, the sixth capacitor, and the sixth resistor are arranged sequentially along the first direction; the seventh resistor, the eighth capacitor, and the seventh capacitor are arranged sequentially along the second direction; and the ninth capacitor, the ninth resistor, and the second winding of the transformer are arranged sequentially along the second direction.

4. The flyback switching power supply according to claim 3, characterized in that The anode of the second diode is connected to the second end of the second winding of the transformer. The cathode of the second diode is connected to the first ends of the seventh capacitor, the eighth capacitor, the seventh resistor, and the eighth resistor, respectively. The second ends of the seventh capacitor, the eighth capacitor, and the seventh resistor are connected to the first end of the second winding of the transformer. The sixth capacitor and the sixth resistor are connected in series between the anode and the cathode of the second diode. The second end of the eighth resistor is connected to the first end of the ninth resistor and the first end of the ninth capacitor, respectively, and then connected to the third end of the control chip. The second end of the ninth resistor and the second end of the ninth capacitor are connected to the fourth end of the control chip.

5. The flyback switching power supply of claim 1, wherein The control circuit includes a tenth capacitor, an eleventh capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor, a transistor, a thirteenth resistor, and a fourteenth resistor; The thirteenth resistor, the fourteenth resistor, the transistor, and the twelfth resistor are arranged sequentially along the first direction, and the eleventh resistor, the tenth capacitor, the eleventh capacitor, and the tenth resistor are arranged sequentially along the second direction.

6. The flyback switching power supply of claim 5, wherein The first terminal of the tenth capacitor is connected to the eighth terminal of the control chip, and the second terminal of the tenth capacitor is grounded. The first terminal of the eleventh capacitor is connected to the second terminal of the control chip, and the second terminal of the eleventh capacitor is connected to the first terminal of the tenth resistor. The second terminal of the tenth resistor is connected to the fourth terminal of the control chip, and the first terminal of the eleventh resistor is connected to the seventh terminal of the control chip. The second terminal of the eleventh resistor is connected to the second terminal of the twelfth resistor. The first terminal of the twelfth resistor is connected to the first power supply terminal, and the second terminal of the twelfth resistor is connected to the collector of the transistor. The fourteenth resistor is connected between the base and emitter of the transistor. The first terminal of the thirteenth resistor is connected to the base of the transistor, and the second terminal of the thirteenth resistor is connected to the power supply enable terminal.

7. The flyback switching power supply of claim 2, wherein It also includes a differential mode loop, which includes a fifteenth resistor, a twelfth capacitor, a third diode, a thirteenth capacitor, a fourteenth capacitor, and a third winding of the transformer; The fifteenth resistor, the third diode, and the thirteenth capacitor are arranged sequentially along the first direction, and the third winding of the transformer, the twelfth capacitor, and the fourteenth capacitor are arranged sequentially along the second direction.

8. The flyback switching power supply of claim 7, wherein The anode of the third diode is connected to the first end of the third winding of the transformer. The cathode of the third diode is connected to the first end of the thirteenth capacitor and the first end of the fourteenth capacitor. The fifteenth resistor and the twelfth capacitor are connected in series between the anode and cathode of the third diode. The second end of the thirteenth capacitor and the second end of the fourteenth capacitor are connected and then connected to the second end of the third winding of the transformer. The first end of the fourteenth capacitor is connected to the second power supply terminal, and the second end of the fourteenth capacitor is grounded.

9. The flyback switching power supply of claim 7, wherein, The differential loop is located in the fourth region, which is parallel to the first region.

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