Circuit structure of a slim switching power supply

Abstract

The present invention relates to the technical field of switch power supplies, in particular to a circuit structure of a slim switch power supply, comprising a rectifier module, a PFC module, a BUCK module and an undervoltage and overvoltage protection module; the rectifier module is electrically connected to the PFC module, and is used to rectify an AC voltage into a rectified voltage and output it to the PFC module; the PFC module is electrically connected to the BUCK module, and is used to output a DC voltage to the BUCK module after power factor correction of the rectified voltage; the BUCK module is used to supply power to a load after DC / DC conversion of the DC voltage; the undervoltage and overvoltage protection module is electrically connected between the PFC module and the BUCK module, and is used to shut down the BUCK module when undervoltage or overvoltage of the rectified voltage is detected; the BUCK module is also connected to a separate reference ground; the problem that the circuit structure of an isolated switch power supply is not suitable for the layout of a slim switch power supply is solved.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, in particular to a circuit structure of a slim switching power supply. Background Art

[0002] Currently, due to the limitations of installation space and budget costs, there is a great demand for low-cost, cost-effective, slim switching power supplies for miniaturized products.

[0003] Current switching power supplies usually use an isolated switching power supply circuit structure. There is no direct electrical connection between the input circuit and the output circuit of the isolated switching power supply. The input and output are insulated high-impedance and there is no current loop. Therefore, it has high safety, can prevent electric shock accidents, and can effectively reduce the impact of undervoltage and overvoltage faults on the switching power supply.

[0004] However, the circuit structure of the isolated switching power supply usually adopts an AC / DC flyback circuit solution, which has a relatively complex circuit structure and low driving efficiency. Faced with the circuit board of the slender switching power supply, the layout is difficult, and the extreme compression of the distance between components may also reduce the anti-interference ability of the isolated power supply circuit structure; more importantly, the circuit structure cost of the isolated switching power supply is relatively high, which does not meet the needs of the slender switching power supply. Summary of the invention

[0005] In view of the above defects, the present invention aims to provide a circuit structure of a slim switching power supply, which solves the problem that the circuit structure of an isolated switching power supply is not suitable for the layout of a slim switching power supply.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A circuit structure of a slim switching power supply, comprising a rectifier module, a PFC module, a BUCK module and an undervoltage and overvoltage protection module; the rectifier module is electrically connected to the PFC module, and is used to rectify an AC voltage into a rectified voltage and output it to the PFC module;

[0008] The PFC module is electrically connected to the BUCK module and is used to output a DC voltage to the BUCK module after performing power factor correction on the rectified voltage;

[0009] The BUCK module is used to perform DC / DC conversion on the DC voltage and then supply power to the load;

[0010] The undervoltage and overvoltage protection module is electrically connected between the PFC module and the BUCK module, and is used to shut down the BUCK module when it is detected that the rectified voltage is undervoltage or overvoltage;

[0011] The BUCK module is also connected to a separate reference ground.

[0012] Furthermore, the undervoltage and overvoltage protection module includes a power management chip IC1 and a photocoupler U3; the power management chip IC1 is electrically connected to the input end of the PFC module to detect whether the rectified voltage is undervoltage or overvoltage;

[0013] The power management chip IC1 is electrically connected to the power supply end of the BUCK module through the photocoupler U3, and is used for turning on the photodetector of the photocoupler U3 to shut down the BUCK module when undervoltage or overvoltage of the rectified voltage is detected.

[0014] Furthermore, the undervoltage and overvoltage protection module further includes a resistor R26, a resistor R25, a resistor R15, a resistor R29, a resistor R17, a resistor R18, a resistor R22, a resistor R23, a resistor R30, a resistor R28, a resistor R12, a resistor R8, a capacitor C3 and a capacitor C7; the collector of the photodetector of the photocoupler U3 is connected in series with the resistor R26 and then electrically connected to the power supply end of the BUCK module, and the emitter of the photodetector of the photocoupler U3 is connected to the ground end GND2;

[0015] The cathode of the light emitting diode of the photoelectric coupler U3 is connected in series with the resistor R25 and then electrically connected to the action end of the power management chip IC1. The anode of the light emitting diode of the photoelectric coupler U3 is connected in series with the resistor R30, the resistor R28, the resistor R12 and the resistor R8 in sequence and then electrically connected to the input end of the PFC module. The connection point between the anode of the light emitting diode of the photoelectric coupler U3 and the resistor R30 is electrically connected to one end of the capacitor C3 and the VDD end of the power management chip IC1. The other end of the capacitor C3 and the GND end of the power management chip IC1 are both connected to the GND1 ground end.

[0016] The temperature sensing end of the power management chip IC1 is connected in series with the resistor R15 and then connected to the GND1 ground end. The resistor R23 is connected in parallel between the undervoltage end and the GND end of the power management chip IC1. The overvoltage end of the power management chip IC1 is connected in series with the capacitor C7 and then connected to the GND1 ground end. The resistor R22 is connected in parallel between the overvoltage end and the undervoltage end of the power management chip IC1. The connection point between the overvoltage end of the power management chip IC1 and the resistor R22 is connected in series with the resistor R18, the resistor R17 and the resistor R29 in sequence and then electrically connected to the input end of the PFC module.

[0017] Further, the BUCK module includes a driving chip U2, a resistor R20, a resistor R21, a resistor R27, a resistor R31, a resistor R14, a resistor R13, a diode D5, a resistor R10, a resistor R11, a resistor RS4, a resistor RS5, a resistor R19, a resistor R16, a resistor R9, a capacitor C8, a capacitor C12, a capacitor EC3, an inductor L3, a magnetic bead B2, a diode D4 and a common mode inductor LF2; the VCC terminal of the driving chip U2 is used as the power supply terminal of the BUCK module;

[0018] The VCC terminal of the driver chip U2 is connected in series with the resistor R27, the resistor R21, and the resistor R20 in sequence, and then electrically connected to the output terminal of the PFC module. The drain terminals of the built-in MOS tubes of the driver chip U2 are electrically connected to the output terminal of the PFC module. The GND terminal of the driver chip U2 is connected to the GND2 ground terminal. The capacitor C8 is connected in parallel between the VCC terminal of the driver chip U2 and the GND2 ground terminal. The resistor R9 is connected in parallel between the feedback terminal of the driver chip U2 and the GND2 ground terminal.

[0019] The source terminal of the built-in MOS tube of the driving chip U2, the sampling terminal of the driving chip U2, one end of the resistor RS4, and one end of the resistor RS5 are all electrically connected to one end of the magnetic bead B2, the other end of the magnetic bead B2 and one end of the capacitor C12 are all electrically connected to the cathode of the diode D4, the other end of the capacitor C12 is electrically connected to one end of the resistor R19, the other end of the resistor RS4, the other end of the resistor RS5, and one end of the inductor L3 are all connected to the ground terminal GND2, the other end of the inductor L3, the The positive electrode of the capacitor EC3, one end of the resistor R16, and one end of the capacitor C10 are all electrically connected to the input end of the first winding of the common-mode inductor LF2, the other end of the capacitor C10 is electrically connected to the output end of the PFC module, the other end of the resistor R19, the anode of the diode D4, the negative electrode of the capacitor EC3, the other end of the resistor R16, and the input end of the second winding of the common-mode inductor LF2 are all connected to the ground terminal GND1, and the output ends of the first winding and the second winding of the common-mode inductor LF2 are electrically connected to the load;

[0020] The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is sequentially connected in series with the resistor R11 and the resistor R10 and then electrically connected to the feedback end of the driving chip U2. The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is also electrically connected to the anode of the diode D5. The cathode of the diode D5 is sequentially connected in series with the resistor R13, the resistor R14 and the resistor R31 and then electrically connected to the VCC end of the driving chip U2.

[0021] Furthermore, the undervoltage and overvoltage protection module also includes a resistor R34, a resistor R33 and a resistor R32; the VDD end of the power management chip IC1 is also connected in series with the resistor R34, the resistor R33 and the resistor R32 in sequence and then electrically connected to the output end of the PFC module.

[0022] Furthermore, the VDD terminal of the power management chip IC1 and the connection point of the resistor R34 are electrically connected by a jumper wire J1, and the jumper wire J1 is made of tinned copper wire.

[0023] Furthermore, the resistor RS4, the resistor RS5, the inductor L3, the capacitor EC3, the magnetic bead B2 and the diode D4 are all arranged close to the source end of the built-in MOS tube of the driving chip U2.

[0024] Furthermore, the wire width from the sampling end of the driving chip U2 through the resistor RS4 and the resistor RS5 to the ground end GND2 is greater than a preset wire width.

[0025] Furthermore, the BUCK module also includes capacitor C9, capacitor C5 and capacitor C6; the temperature measurement end of the driver chip U2 is connected in series with the capacitor C9 and then connected to the GND2 ground terminal, the compensation end of the driver chip U2 is connected in series with the capacitor C5 and then connected to the GND2 ground terminal, and the capacitor C6 is connected in parallel between the feedback end of the driver chip U2 and the GND2 ground terminal.

[0026] Furthermore, the resistor R9 , the resistor R10 , and the resistor R11 are all arranged close to the feedback end of the driving chip U2 .

[0027] The technical solution provided by the present invention may include the following beneficial effects: a non-isolated switching power supply is composed of a rectifier module, a PFC module, and a BUCK module. Compared with an isolated power supply, a transformer, an auxiliary winding, and a complex flyback circuit structure are omitted. The circuit is simple, the driving efficiency is high, and the cost is low. It is suitable for the circuit board layout of a slender switching power supply and meets higher safety requirements.

[0028] At the same time, due to the layout on a slender circuit board, the rectifier module and PFC module may be at one end of the circuit board, and the BUCK module may be at the other end of the circuit board. The span is relatively large. When the PFC module is undervoltage or overvoltage, the BUCK module cannot be turned off in time to stop the switching power supply for protection. Therefore, an undervoltage and overvoltage protection module is added to connect the PFC module and the BUCK module to reduce the impact of undervoltage and overvoltage faults on the switching power supply, improve the safety of direct electrical connections, and effectively prevent electric shock accidents.

[0029] More importantly, considering that the modules of the non-isolated switching power supply have direct electrical connections, crosstalk will be generated, which will affect the stability of the BUCK module's power supply to the load and make the load unstable (for example, when the load is an LED lamp, it will flicker). Therefore, the BUCK module is connected to a separate reference ground (that is, it is connected to the GND ground terminal alone, and the other modules are connected to the GND ground terminal). This can also avoid a large ground span on a slender circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the circuit structure of a slim switching power supply according to one embodiment of the present invention.

[0031] Figure 2 Yes Figure 1 The circuit diagram of the rectifier module and PFC module is shown.

[0032] Figure 3 Yes Figure 1 The circuit diagram of the undervoltage and overvoltage protection module is shown.

[0033] Figure 4 Yes Figure 1 The circuit diagram of the BUCK module is shown.

[0034] Figure 5 Yes Figure 4 The diagram shows the path of the high current loop 1 of the BUCK module.

[0035] Figure 6 Yes Figure 4 The schematic diagram of the path of the high current loop 2 of the BUCK module is shown.

[0036] Among them: rectifier module 1, PFC module 2, BUCK module 3, undervoltage and overvoltage protection module 4, power management chip IC1, photocoupler U3, resistor R26, resistor R25, resistor R15, resistor R29, resistor R17, resistor R18, resistor R22, resistor R23, resistor R30, resistor R28, resistor R12, resistor R8, capacitor C3, capacitor C7, driver chip U2, resistor R20, resistor R21, resistor R27, resistor R31, resistor R14, resistor R13, diode D5, resistor R10, resistor R11, resistor RS4, resistor RS5, resistor R19, resistor R16, resistor R9, capacitor C8, capacitor C12, capacitor EC3, inductor L3, magnetic bead B2 diode D4, common mode inductor LF2, resistor R34, resistor R33, resistor R32, jumper J1, capacitor C9, capacitor C5, capacitor C6. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0038] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0040] Combine the following Figures 1 to 6 , describing the circuit structure of a slim switching power supply according to an embodiment of the present invention.

[0041] A circuit structure of a slim switching power supply includes a rectifier module 1, a PFC module 2, a BUCK module 3 and an undervoltage and overvoltage protection module 4; the rectifier module 1 is electrically connected to the PFC module 2 and is used to rectify an AC voltage into a rectified voltage and output it to the PFC module 2;

[0042] The PFC module 2 is electrically connected to the BUCK module 3 and is used to output a DC voltage to the BUCK module 3 after performing power factor correction on the rectified voltage;

[0043] BUCK module 3 is used to convert the DC voltage into DC / DC and then supply power to the load;

[0044] The undervoltage and overvoltage protection module 4 is electrically connected between the PFC module 2 and the BUCK module 3, and is used to shut down the BUCK module 3 when the rectified voltage is detected to be undervoltage or overvoltage;

[0045] BUCK module 3 is also connected to a separate reference ground.

[0046] The present invention proposes a circuit structure preferred embodiment of a slim switching power supply, such as Figure 1As shown, the non-isolated switching power supply is composed of a rectifier module 1, a PFC module 2, and a BUCK module 3. Compared with the isolated power supply, the transformer, the auxiliary winding, and the complex flyback circuit structure are omitted. The circuit is simple, the driving efficiency is high, and the cost is low. It is suitable for the circuit board layout of a slender switching power supply and meets higher safety requirements.

[0047] At the same time, due to the layout on a slender circuit board, the rectifier module 1 and the PFC module 2 may be at one end of the circuit board, and the BUCK module 3 may be at the other end of the circuit board. The span is relatively large. When the PFC module 2 is undervoltage or overvoltage, the BUCK module 3 cannot be turned off in time to stop the switching power supply for protection. Therefore, an undervoltage and overvoltage protection module 4 is added to connect the PFC module 2 and the BUCK module 4, thereby reducing the impact of undervoltage and overvoltage faults on the switching power supply, improving the safety of direct electrical connections, and effectively preventing electric shock accidents.

[0048] More importantly, considering that the modules of the non-isolated switching power supply have direct electrical connections, crosstalk will be generated, which will affect the stability of the power supply of the load by the BUCK module 3, making the load unstable (for example, when the load is an LED lamp, it will flicker). Therefore, the BUCK module 3 is connected to a separate reference ground (that is, it is connected to the GND2 ground terminal alone, and the other modules are connected to the GND1 ground terminal). It can also avoid the ground line span on the slender circuit board being too large.

[0049] It should be noted that the working principle of the rectifier module 1 is as follows (one embodiment is as follows: Figure 2 As shown in the figure): After the AC power passes through the safety circuit composed of components such as common mode inductor LF3, resistor R1, resistor R2, etc., the rectifier bridge BD1 generates a rectified voltage; and the working principle of the PFC module 3 is (one embodiment is as follows Figure 2 As shown in the figure): The peripheral circuit is built with the PFC chip (such as JW1964) as the core, and after the rectified voltage is power factor corrected, a DC voltage is output to the BUCK module 3 through the energy storage filter capacitor EC1 (or large aluminum electrolytic capacitor EC1).

[0050] Furthermore, the undervoltage and overvoltage protection module 4 includes a power management chip IC1 and a photocoupler U3; the power management chip IC1 is electrically connected to the input end of the PFC module 2, and is used to detect whether the rectified voltage is undervoltage or overvoltage;

[0051] The power management chip IC1 is electrically connected to the power supply terminal of the BUCK module 3 through the photocoupler U3 , and is used for turning on the photodetector of the photocoupler U3 and shutting down the BUCK module 3 when the rectified voltage is detected to be undervoltage or overvoltage.

[0052] In this embodiment, Figure 3As shown, in order to improve the integration of the undervoltage and overvoltage protection module 4 and make it more suitable for the layout of a slender circuit board, the undervoltage and overvoltage protection is realized by the power management chip IC1 and the photocoupler U3. In order to detect the fault earlier and control the BUCK module 3 to shut down, the power management chip IC1 collects the rectified voltage at the input end (HV1) of the PFC module 2 for judgment, and then controls the BUCK module 3 to shut down through the isolated feedback of the photocoupler U3.

[0053] Furthermore, the undervoltage and overvoltage protection module 4 also includes a resistor R26, a resistor R25, a resistor R15, a resistor R29, a resistor R17, a resistor R18, a resistor R22, a resistor R23, a resistor R30, a resistor R28, a resistor R12, a resistor R8, a capacitor C3 and a capacitor C7; the collector of the photodetector of the photocoupler U3 is electrically connected to the power supply end of the BUCK module 3 after being connected in series with the resistor R26, and the emitter of the photodetector of the photocoupler U3 is connected to the ground end GND2;

[0054] The cathode of the light-emitting diode of the photocoupler U3 is connected in series with the resistor R25 and then electrically connected to the action end of the power management chip IC1. The anode of the light-emitting diode of the photocoupler U3 is connected in series with the resistor R30, the resistor R28, the resistor R12 and the resistor R8 in sequence and then electrically connected to the input end of the PFC module 2. The connection point between the anode of the light-emitting diode of the photocoupler U3 and the resistor R30 is electrically connected to one end of the capacitor C3 and the VDD end of the power management chip IC1. The other end of the capacitor C3 and the GND end of the power management chip IC1 are both connected to the GND1 ground end.

[0055] The temperature sensing end of the power management chip IC1 is connected in series with resistor R15 and then connected to the GND1 ground end, a resistor R23 is connected in parallel between the undervoltage end and the GND end of the power management chip IC1, the overvoltage end of the power management chip IC1 is connected in series with capacitor C7 and then connected to the GND1 ground end, a resistor R22 is connected in parallel between the overvoltage end and the undervoltage end of the power management chip IC1, and the connection point between the overvoltage end of the power management chip IC1 and the resistor R22 is connected in series with resistors R18, R17 and R29 in sequence, and then electrically connected to the input end of the PFC module 2.

[0056] In this embodiment, the undervoltage and overvoltage protection module 4 is specifically composed of a resistor R26, a resistor R25, a resistor R15, a resistor R29, a resistor R17, a resistor R18, a resistor R22, a resistor R23, a resistor R30, a resistor R28, a resistor R12, a resistor R8, a capacitor C3 and a capacitor C7 to form a peripheral circuit of the power management chip IC1 and the photocoupler U3, wherein the input end (HV1) of the PFC module 2 is powered by the power management chip IC1 and the photocoupler U3 after current limiting by multiple resistors such as resistors R30 and resistor R28, and the same At this time, the input end (HV1) of the PFC module 2 is limited by multiple resistors such as resistors R29 and resistor R17, and the high-frequency interference is suppressed to increase the detection voltage of the overvoltage end (OVR end) and the undervoltage end (BRO end) of the power management chip IC1. For example, when the power management chip IC1 is an OB3631 chip, the internal overvoltage reference voltage can be set to 2V, and the undervoltage reference voltage can be set to 0.5V. When the detection voltage is higher than 2V or lower than 0.5V, the internal transistor is driven to make the action end (DRP end) low level, and the BUCK module 3 is turned off.

[0057] It should be noted that the temperature sensing end, overvoltage end, undervoltage end and action end (or pull-down protection end) of the power management chip IC1 are determined by the specific chip used. For example, when the power management chip IC1 uses the OB3631 chip, the temperature sensing end, overvoltage end, undervoltage end and action end (or pull-down protection end) are the RT end, OVR end, BRO end and DRP end respectively.

[0058] Further, the BUCK module 3 includes a driving chip U2, a resistor R20, a resistor R21, a resistor R27, a resistor R31, a resistor R14, a resistor R13, a diode D5, a resistor R10, a resistor R11, a resistor RS4, a resistor RS5, a resistor R19, a resistor R16, a resistor R9, a capacitor C8, a capacitor C12, a capacitor EC3, an inductor L3, a magnetic bead B2, a diode D4 and a common mode inductor LF2; the VCC terminal of the driving chip U2 is used as the power supply terminal of the BUCK module 3;

[0059] The VCC terminal of the driver chip U2 is connected in series with resistors R27, R21, and R20 in sequence, and then electrically connected to the output terminal of the PFC module 2. The drain terminals of the built-in MOS tubes of the driver chip U2 are electrically connected to the output terminal of the PFC module 2. The GND terminal of the driver chip U2 is connected to the GND2 ground terminal. A capacitor C8 is connected in parallel between the VCC terminal of the driver chip U2 and the GND2 ground terminal. A resistor R9 is connected in parallel between the feedback terminal of the driver chip U2 and the GND2 ground terminal.

[0060] The source end of the MOS tube built in the driving chip U2, the sampling end of the driving chip U2, one end of the resistor RS4, and one end of the resistor RS5 are all electrically connected to one end of the magnetic bead B2, the other end of the magnetic bead B2 and one end of the capacitor C12 are all electrically connected to the cathode of the diode D4, the other end of the capacitor C12 is electrically connected to one end of the resistor R19, the other end of the resistor RS4, the other end of the resistor RS5, and one end of the inductor L3 are all connected to the GND2 ground terminal, the other end of the inductor L3, the positive electrode of the capacitor EC3, one end of the resistor R16, and one end of the capacitor C10 are all electrically connected to the input end of the first winding of the common-mode inductor LF2, the other end of the capacitor C10 is electrically connected to the output end of the PFC module 2, the other end of the resistor R19, the anode of the diode D4, the negative electrode of the capacitor EC3, the other end of the resistor R16, and the input end of the second winding of the common-mode inductor LF2 are all connected to the GND1 ground terminal, and the output ends of the first winding and the second winding of the common-mode inductor LF2 are electrically connected to the load;

[0061] The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is connected in series with the resistor R11 and the resistor R10 in sequence and then electrically connected to the feedback end of the driving chip U2. The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is also electrically connected to the anode of the diode D5. The cathode of the diode D5 is connected in series with the resistor R13, the resistor R14 and the resistor R31 in sequence and then electrically connected to the VCC end of the driving chip U2.

[0062] In this embodiment, Figure 4 As shown, the BUCK module 3 realizes the DC / DC conversion function by the driver chip U2 and its peripheral circuits.

[0063] It should be noted that the source terminal, the drain terminal, the temperature measurement terminal, the compensation terminal, the feedback terminal and the sampling terminal of the built-in MOS tube of the driver chip U2 are determined by the specific chip used. For example, when the driver chip U2 uses the BP2872 chip, the source terminal, the drain terminal, the temperature measurement terminal, the compensation terminal, the feedback terminal and the sampling terminal of the built-in MOS tube are the Source terminal, the DRAIN terminal, the NTC terminal, the COMP terminal, the FB terminal and the CS terminal respectively.

[0064] Furthermore, the undervoltage and overvoltage protection module 4 also includes a resistor R34 , a resistor R33 and a resistor R32 ; the VDD end of the power management chip IC1 is also connected in series with the resistor R34 , the resistor R33 and the resistor R32 in sequence and then electrically connected to the output end of the PFC module 2 .

[0065] In this embodiment, since the power management chip IC1 of the undervoltage and overvoltage protection module 4 is powered by the input end (HV1) of the PFC module 2, and the driver chip U2 of the BUCK module 3 is powered by the output end (HV) of the PFC module 2, due to the different power supplies, there is a time difference in power-off in the case of a slender circuit board layout. When the switching power supply is shut down, the undervoltage and overvoltage protection module 4 will be turned off first, so that the action end of the power management chip IC1 becomes low level at the moment of shutdown, and the malfunction photoelectric coupler U3 is started, so that the BUCK module 3 is turned off, and then the power management chip IC1 stops working, and the power supply of the output end (HV) of the PFC module 2 restarts the BUCK module 3, and then it is shut down as the output end (HV) of the PFC module 2 is powered off, resulting in a shutdown load flickering (or unstable) problem; therefore, the VDD end of the power management chip IC1 is also connected in series with multiple resistors to the output end (HV) of the PFC module 2 for delayed shutdown of the power management chip IC1, so that the switch power supply no longer has a load flickering (or unstable) problem.

[0066] Furthermore, the VDD terminal of the power management chip IC1 and the connection point of the resistor R34 are electrically connected by a jumper wire J1 , and the jumper wire J1 is made of tinned copper wire.

[0067] In this embodiment, based on the large span between modules in the slender circuit board layout, no matter where the undervoltage and overvoltage protection module 4 is arranged, there is a long distance to the output end (HV) of the PFC module 2; therefore, the use of the jumper J1 for electrical connection can reduce the wiring space occupied by the circuit board (because the power line width is usually relatively large); and the jumper J1 preferably uses tinned copper wire, which is more advantageous than the generally used pure copper wire in terms of anti-interference, corrosion resistance and service life.

[0068] Furthermore, the resistor RS4, the resistor RS5, the inductor L3, the capacitor EC3, the magnetic bead B2 and the diode D4 are all arranged close to the source end of the built-in MOS tube of the driving chip U2.

[0069] In this embodiment, since the output of the PFC module 2 passes through the large aluminum electrolytic capacitor EC1, the GND2 ground terminal of the BUCK module 3 that adopts a floating ground (i.e., connected to a separate reference ground) is an interference source relative to the large aluminum electrolytic capacitor EC1, which increases the difficulty of EMI debugging; therefore, the BUCK module 3 needs to reduce the area of ​​the large current loop (the loop area refers to the area enclosed by the current in the circuit on a closed path) to reduce EMI radiation.

[0070] Specifically, a large current loop (such as Figure 5As shown in the figure): A closed path is formed by a large aluminum electrolytic capacitor EC1, a built-in MOS tube of the driver chip U2, a resistor RS4, a resistor RS5, an inductor L3 and a capacitor EC3 for charging the capacitor EC3; therefore, in the BUCK module 3, the resistor RS4, the resistor RS5, the inductor L3 and the capacitor EC3 are closely clustered and arranged close to the source terminal of the built-in MOS tube of the driver chip U2, so that the wires between the components are shorter, thereby reducing the loop area.

[0071] Similarly, the second large current loop (such as Figure 6 As shown in the figure): a closed path is formed by resistor RS4, resistor RS5, inductor L3, capacitor EC3, diode D4 and magnetic bead B2 for discharging capacitor EC3; therefore, diode D4 and magnetic bead B2 are arranged together with resistor RS4, resistor RS5, inductor L3 and capacitor EC3 in BUCK module 3, and the wires between the components are shorter, thereby reducing the loop area.

[0072] Furthermore, the width of the wire from the sampling terminal of the driving chip U2 through the resistor RS4 and the resistor RS5 to the ground terminal GND2 is greater than the preset wire width.

[0073] In this embodiment, since the BUCK module 3 is connected to the GND2 ground terminal (floating ground), the EMI radiation is relatively large, and the power ground line of the current sampling resistor (i.e., the resistor RS4 and the resistor RS5) of the driver chip U2 is as thick as possible to ensure the accuracy of current sampling; therefore, the wire width from the sampling end of the driver chip U2 through the resistor RS4 and the resistor RS5 to the GND2 ground terminal is greater than the preset wire width, that is, wider than other wires (the preset width is the width generally used for electrical connection wires).

[0074] Furthermore, the BUCK module 3 also includes capacitor C9, capacitor C5 and capacitor C6; the temperature measurement end of the driver chip U2 is connected in series with capacitor C9 and then connected to the GND2 ground terminal, the compensation end of the driver chip U2 is connected in series with capacitor C5 and then connected to the GND2 ground terminal, and the capacitor C6 is connected in parallel between the feedback end of the driver chip U2 and the GND2 ground terminal.

[0075] In this embodiment, since the BUCK module 3 is connected to the GND2 ground terminal (floating ground), the EMI radiation is relatively large, and capacitors are respectively arranged between the temperature measurement terminal (NTC terminal) of the driver chip U2 and the GND2 ground terminal, between the compensation terminal (COMP terminal) of the driver chip U2 and the GND2 ground terminal, and between the feedback terminal (FB terminal) of the driver chip U2 and the GND2 ground terminal to avoid EMI interference.

[0076] Furthermore, the resistor R9 , the resistor R10 , and the resistor R11 are all disposed close to the feedback terminal of the driving chip U2 .

[0077] In this embodiment, the voltage divider resistors (i.e., resistors R9, R10, and R11) connected to the feedback terminal (FB terminal) of the driver chip U2 are close to the feedback terminal, which can reduce interference effects and prevent noise from falsely triggering the protection function of the driver chip U2.

[0078] Other components and operations of the circuit structure of a slim switching power supply according to the embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0079] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A circuit structure of a slim switching power supply, characterized in that: It includes a rectifier module, a PFC module, a BUCK module and an undervoltage and overvoltage protection module; the rectifier module is electrically connected to the PFC module and is used to rectify the AC voltage into a rectified voltage and output it to the PFC module; The PFC module is electrically connected to the BUCK module and is used to output a DC voltage to the BUCK module after performing power factor correction on the rectified voltage; The BUCK module is used to perform DC / DC conversion on the DC voltage and then supply power to the load; The undervoltage and overvoltage protection module is electrically connected between the PFC module and the BUCK module, and is used to shut down the BUCK module when it is detected that the rectified voltage is undervoltage or overvoltage; The BUCK module is also connected to a separate reference ground; The undervoltage and overvoltage protection module includes a power management chip IC1 and a photocoupler U3; the power management chip IC1 is electrically connected to the input end of the PFC module to detect whether the rectified voltage is undervoltage or overvoltage; The power management chip IC1 is electrically connected to the power supply end of the BUCK module through the photocoupler U3, and is used for turning on the photodetector of the photocoupler U3 to shut down the BUCK module when the rectified voltage is detected to be undervoltage or overvoltage; The undervoltage and overvoltage protection module further includes a resistor R26, a resistor R25, a resistor R15, a resistor R29, a resistor R17, a resistor R18, a resistor R22, a resistor R23, a resistor R30, a resistor R28, a resistor R12, a resistor R8, a capacitor C3 and a capacitor C7; the collector of the photodetector of the photocoupler U3 is connected in series with the resistor R26 and then electrically connected to the power supply end of the BUCK module, and the emitter of the photodetector of the photocoupler U3 is connected to the ground end GND2; The cathode of the light emitting diode of the photoelectric coupler U3 is connected in series with the resistor R25 and then electrically connected to the action end of the power management chip IC1. The anode of the light emitting diode of the photoelectric coupler U3 is connected in series with the resistor R30, the resistor R28, the resistor R12 and the resistor R8 in sequence and then electrically connected to the input end of the PFC module. The connection point between the anode of the light emitting diode of the photoelectric coupler U3 and the resistor R30 is electrically connected to one end of the capacitor C3 and the VDD end of the power management chip IC1. The other end of the capacitor C3 and the GND end of the power management chip IC1 are both connected to the GND1 ground end. The temperature sensing end of the power management chip IC1 is connected in series with the resistor R15 and then connected to the GND1 ground end. The resistor R23 is connected in parallel between the undervoltage end and the GND end of the power management chip IC1. The overvoltage end of the power management chip IC1 is connected in series with the capacitor C7 and then connected to the GND1 ground end. The resistor R22 is connected in parallel between the overvoltage end and the undervoltage end of the power management chip IC1. The connection point between the overvoltage end of the power management chip IC1 and the resistor R22 is connected in series with the resistor R18, the resistor R17 and the resistor R29 in sequence and then electrically connected to the input end of the PFC module.

2. The circuit structure of a slim switching power supply according to claim 1, characterized in that: The BUCK module includes a driver chip U2, a resistor R20, a resistor R21, a resistor R27, a resistor R31, a resistor R14, a resistor R13, a diode D5, a resistor R10, a resistor R11, a resistor RS4, a resistor RS5, a resistor R19, a resistor R16, a resistor R9, a capacitor C8, a capacitor C12, a capacitor EC3, an inductor L3, a magnetic bead B2, a diode D4 and a common mode inductor LF2; the VCC terminal of the driver chip U2 is used as the power supply terminal of the BUCK module; The VCC terminal of the driver chip U2 is connected in series with the resistor R27, the resistor R21, and the resistor R20 in sequence, and then electrically connected to the output terminal of the PFC module. The drain terminals of the built-in MOS tubes of the driver chip U2 are electrically connected to the output terminal of the PFC module. The GND terminal of the driver chip U2 is connected to the GND2 ground terminal. The capacitor C8 is connected in parallel between the VCC terminal of the driver chip U2 and the GND2 ground terminal. The resistor R9 is connected in parallel between the feedback terminal of the driver chip U2 and the GND2 ground terminal. The source terminal of the built-in MOS tube of the driving chip U2, the sampling terminal of the driving chip U2, one end of the resistor RS4, and one end of the resistor RS5 are all electrically connected to one end of the magnetic bead B2, the other end of the magnetic bead B2 and one end of the capacitor C12 are all electrically connected to the cathode of the diode D4, the other end of the capacitor C12 is electrically connected to one end of the resistor R19, the other end of the resistor RS4, the other end of the resistor RS5, and one end of the inductor L3 are all connected to the ground terminal GND2, the other end of the inductor L3, the The positive electrode of the capacitor EC3, one end of the resistor R16, and one end of the capacitor C10 are all electrically connected to the input end of the first winding of the common-mode inductor LF2, the other end of the capacitor C10 is electrically connected to the output end of the PFC module, the other end of the resistor R19, the anode of the diode D4, the negative electrode of the capacitor EC3, the other end of the resistor R16, and the input end of the second winding of the common-mode inductor LF2 are all connected to the ground terminal GND1, and the output ends of the first winding and the second winding of the common-mode inductor LF2 are electrically connected to the load; The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is sequentially connected in series with the resistor R11 and the resistor R10 and then electrically connected to the feedback end of the driving chip U2. The common point of the inductor L3, the capacitor EC3, the resistor R16, the capacitor C10 and the common-mode inductor LF2 is also electrically connected to the anode of the diode D5. The cathode of the diode D5 is sequentially connected in series with the resistor R13, the resistor R14 and the resistor R31 and then electrically connected to the VCC end of the driving chip U2.

3. The circuit structure of a slim switching power supply according to claim 2, characterized in that: The undervoltage and overvoltage protection module also includes a resistor R34, a resistor R33 and a resistor R32; the VDD end of the power management chip IC1 is also connected in series with the resistor R34, the resistor R33 and the resistor R32 in sequence and then electrically connected to the output end of the PFC module.

4. The circuit structure of a slim switching power supply according to claim 3, characterized in that: The VDD terminal of the power management chip IC1 and the connection point of the resistor R34 are electrically connected by a jumper wire J1 , and the jumper wire J1 is made of tinned copper wire.

5. The circuit structure of a slim switching power supply according to claim 2, characterized in that: The resistor RS4, the resistor RS5, the inductor L3, the capacitor EC3, the magnetic bead B2 and the diode D4 are all arranged close to the source terminal of the built-in MOS tube of the driving chip U2.

6. The circuit structure of a slim switching power supply according to claim 2, characterized in that: The width of the wire from the sampling end of the driving chip U2 through the resistor RS4 and the resistor RS5 to the ground end GND2 is greater than the preset wire width.

7. The circuit structure of a slim switching power supply according to claim 2, characterized in that: The BUCK module also includes capacitor C9, capacitor C5 and capacitor C6; the temperature measurement end of the driver chip U2 is connected in series with the capacitor C9 and then connected to the GND2 ground terminal, the compensation end of the driver chip U2 is connected in series with the capacitor C5 and then connected to the GND2 ground terminal, and the capacitor C6 is connected in parallel between the feedback end of the driver chip U2 and the GND2 ground terminal.

8. The circuit structure of a slim switching power supply according to claim 2, characterized in that: The resistor R9 , the resistor R10 , and the resistor R11 are all disposed close to the feedback end of the driving chip U2 .

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