Free switching and anti-backflow circuit for direct-current or alternating-current input power supply
By designing a circuit that includes an AC input terminal, a DC input terminal, a PWM switching power supply circuit, and a reverse current protection circuit, the problems of size mismatch and safety risks in traditional power supply retrofitting are solved. It achieves seamless switching between DC and AC power supply and reverse current protection, meeting the needs of different users.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2026-04-07
AI Technical Summary
Traditional power supply retrofits suffer from issues such as size mismatch, inconvenient installation, and high safety risks. Furthermore, traditional backflow prevention designs are inefficient, costly, and affect system stability under high loads.
Design a circuit that includes an AC input terminal, a DC input terminal, a PWM switching power supply circuit, an AC/DC switching circuit, and a reverse current protection circuit. The circuit uses components such as relays and MOSFETs to achieve free switching between DC and AC inputs and reverse current protection. The DC priority strategy and the reverse current protection circuit ensure system stability.
It achieves seamless switching between DC and AC power supply, provides effective backflow protection, enhances the adaptability and safety of the equipment, reduces modification costs, and meets the needs of ordinary users and technology enthusiasts.
Smart Images
Figure CN224097601U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power supply technology, specifically to a circuit for freely switching between DC and AC input power and preventing backflow. Background Technology
[0002] In the consumer electronics sector, product design and manufacturing require finding a balance between performance, cost, and market demand. For manufacturers, to meet the needs of the mass market and offer competitive products at reasonable prices, certain compromises must be made in product design. This means that every product cannot be pushed to its technological limits, as doing so would lead to excessive costs and violate market principles.
[0003] However, for tech enthusiasts seeking the ultimate experience, standard products on the market often fail to meet their needs. These users want to modify their equipment in various ways to achieve higher performance or fulfill personalized usage requirements. Among these modifications, power supply system upgrades are particularly common.
[0004] Traditional power supply retrofitting typically involves discarding the original onboard power supply and replacing it with a higher-performance third-party power supply. However, this approach has significant drawbacks: on the one hand, the new power supply may face issues such as size mismatch and installation inconvenience; on the other hand, non-professionals face an extremely high risk of coming into contact with high-voltage components during disassembly and assembly, potentially leading to serious safety accidents.
[0005] In addition, traditional anti-backflow designs often rely on Schottky diodes. Although they have advantages such as fast switching speed, they also expose a series of problems in practical applications: such as large loss of forward conduction efficiency under high load current, the need for additional heat dissipation measures leading to increased cost and space requirements, and increased reverse leakage current as temperature rises, thus affecting system stability. Utility Model Content
[0006] This invention addresses the shortcomings and deficiencies of existing technologies by providing a low-cost and simple circuit for freely switching between DC and AC input power supplies and preventing backflow.
[0007] To achieve the above objectives, the present invention provides a circuit for freely switching between DC and AC input power and preventing backflow, comprising an AC input terminal, a DC input terminal, a PWM switching power supply circuit, an AC-DC switching circuit, a backflow prevention protection circuit, and a DC output terminal; the AC input terminal is electrically connected to the AC-DC switching circuit; the AC-DC switching circuit is electrically connected to the PWM switching power supply circuit; the DC input terminal is electrically connected to the backflow prevention protection circuit; the backflow prevention protection circuit is electrically connected to the PWM switching power supply circuit; and the DC output terminal is electrically connected to the backflow prevention protection circuit.
[0008] Further, the AC / DC switching circuit includes a relay, a first transistor, a second transistor, a first diode, a first resistor, and a second resistor; the third and fifth pins of the relay are electrically connected, the fourth and sixth pins of the relay are electrically connected, and the first pin of the relay is connected to a 12V voltage; one end of the first diode is electrically connected to the first pin of the relay, and the other end is electrically connected to the second pin of the relay; the collector of the first transistor is electrically connected to the first diode, the emitter of the first transistor is grounded, and the base of the first transistor is electrically connected to the collector of the second transistor; one end of the first resistor is electrically connected to the first diode, and the other end is electrically connected to the emitter of the second transistor; one end of the second resistor is electrically connected to the base of the second transistor, and the other end is grounded.
[0009] Further; the PWM switching power supply circuit includes a power management chip, an isolation transformer, a rectifier bridge, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a ninth diode, a thermistor, a transient voltage suppressor, an optocoupler, a rectifier filter circuit, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a third transistor, and a first MOSFET; The rectifier-filter circuit is electrically connected to the AC input terminal. The first capacitor and the transient voltage suppressor are connected in parallel, and the first capacitor and the transient voltage suppressor are positioned between the rectifier-filter circuit and the AC input terminal. One end of the thermistor is electrically connected to the transient voltage suppressor, and the other end is connected to an output port. The first terminal of the rectifier bridge is electrically connected to the rectifier-filter circuit. The second diode and the third diode are connected in parallel, with one end electrically connected to the first terminal of the rectifier bridge and the other end electrically connected to the third resistor. The eighth pin of the power management chip is electrically connected to the third resistor. The second terminal of the rectifier bridge is electrically connected to the third diode. One end of the first capacitor is electrically connected to the fourth terminal of the rectifier bridge. One end is connected to the first capacitor, and the other end is electrically connected to the third terminal of the rectifier bridge; the fourth, fifth, and sixth resistors and the second capacitor are connected in parallel, one end of which is electrically connected to the first capacitor, and the other end is electrically connected to the first pin of the isolation transformer; the seventh and eighth resistors are connected in parallel, one end of which is electrically connected to the fourth resistor, and the other end is electrically connected to one end of the fourth diode; the other end of the fourth diode is electrically connected to the third pin of the isolation transformer; one end of the third capacitor is electrically connected to the sixth pin of the power management chip, and the other end is grounded; the fifth diode and the ninth resistor are connected in series, one end of which is electrically connected to the fifth pin of the isolation transformer, and the other end is electrically connected to the third capacitor; the fourth... One end of the tenth resistor is electrically connected to the first pin of the power management chip, and the other end is electrically connected to the ninth resistor. One end of the eleventh resistor is electrically connected to the fifth pin of the power management chip, and the other end is electrically connected to the gate of the first MOSFET. The drain of the first MOSFET is electrically connected to the fifth diode. One end of the twelfth resistor is electrically connected to the third pin of the power management chip, and the other end is electrically connected to the source of the first MOSFET. The base of the third transistor is electrically connected to the fifth pin of the power management chip. The emitter of the third transistor is electrically connected to the eleventh resistor. One end of the thirteenth resistor is electrically connected to the fourth pin of the power management chip, and the other end is electrically connected to the collector of the third transistor.One end of the fourteenth resistor is electrically connected to the thirteenth resistor, and the other end is electrically connected to the drain of the first MOSFET. One end of the fourth capacitor is electrically connected to the twelfth resistor, and the other end is electrically connected to the fourth pin of the power management chip. One end of the fifth capacitor is electrically connected to the second pin of the power management chip, and the other end is electrically connected to the fourth pin of the power management chip. The fourth pin of the optocoupler is electrically connected to the second pin of the power management chip, and the third pin of the optocoupler is electrically connected to the fifth capacitor. The fifth diode and the sixth diode are connected in parallel, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the first voltage regulator circuit. The sixth capacitor and the tenth... Five resistors are connected in series, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the fifth diode. One end of the seventh capacitor is electrically connected to the sixth diode, and the other end is electrically connected to the ninth pin of the isolation transformer. The seventh and eighth diodes are connected in parallel, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to a second voltage regulator circuit. The eighth capacitor and the sixteenth resistor are connected in series, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to the seventh diode. One end of the ninth capacitor is electrically connected to the eighth diode, and the other end is grounded. The eighth pin of the isolation transformer is electrically connected to the ninth capacitor.
[0010] Furthermore, the backflow prevention protection circuit includes a first backflow prevention protection circuit, a second backflow prevention protection circuit, and a third backflow prevention protection circuit; one end of the first backflow prevention protection circuit is electrically connected to the output terminal of the first voltage regulator circuit, and the other end is electrically connected to the second backflow prevention protection circuit; the first backflow prevention protection circuit is electrically connected to the second voltage regulator circuit; a third voltage regulator circuit is provided between the second voltage regulator circuit and the third backflow prevention protection circuit; one end of the third voltage regulator circuit is connected to the second voltage regulator circuit, and the other end is electrically connected to the third backflow prevention protection circuit.
[0011] Further; the first backflow prevention protection circuit includes a first ideal diode controller, a tenth capacitor, a seventeenth resistor, and a second MOSFET; one end of the tenth capacitor is grounded, and the other end is electrically connected to the first pin of the first ideal diode controller; the source of the second MOSFET is electrically connected to the first voltage regulator circuit, and the gate of the second MOSFET is electrically connected to the fifth pin of the first ideal diode controller; one end of the seventeenth resistor is electrically connected to the tenth capacitor, and the other end is electrically connected to the source of the second MOSFET; the fourth pin of the first ideal diode controller is electrically connected to the seventeenth resistor; the second and third pins of the first ideal diode controller are both grounded; the second and sixth pins of the first ideal diode controller are both electrically connected to the second backflow prevention protection circuit; and the drain of the second MOSFET is electrically connected to the sixth pin of the first ideal diode controller.
[0012] Further; the second backflow protection circuit includes a second ideal diode controller, an eleventh capacitor, a twelfth capacitor, a nineteenth resistor, and a third MOSFET; the source of the third MOSFET is connected to a 12V voltage, the gate of the third MOSFET is electrically connected to the fifth pin of the second ideal diode controller, and the drain of the third MOSFET is electrically connected to the sixth pin of the second ideal diode controller; one end of the eleventh capacitor is grounded, and the other end is electrically connected to the source of the third MOSFET, and the fourth pin of the second ideal diode controller is electrically connected to the eleventh capacitor; the nineteenth resistor and the twelfth capacitor are connected in series, one end of which is electrically connected to the fourth pin of the second ideal diode controller, and the other end is electrically connected to the second pin of the first ideal diode controller; the second pin of the second ideal diode controller is electrically connected to the second pin of the first ideal diode controller, and the second pin of the second ideal diode controller is electrically connected to the third pin of the second ideal diode controller.
[0013] Furthermore, the third reverse current protection circuit includes a third ideal diode controller, a thirteenth capacitor, a twentieth resistor, and a fourth MOSFET. The source of the fourth MOSFET is electrically connected to the third voltage regulator circuit, and the drain of the fourth MOSFET is connected to a 5V voltage. The fourth pin of the third ideal diode controller is electrically connected to the source of the fourth MOSFET. The twentieth resistor and the thirteenth capacitor are connected in series, with one end grounded and the other end electrically connected to the source of the fourth MOSFET. The gate of the fourth MOSFET is electrically connected to the fifth pin of the third ideal diode controller. The sixth pin of the third ideal diode controller is electrically connected to the drain of the fourth MOSFET. The second and third pins of the third ideal diode controller are both grounded, and the first pin of the third ideal diode controller is electrically connected to the thirteenth capacitor.
[0014] The beneficial effects of this utility model are:
[0015] This invention provides a circuit for freely switching between DC and AC input power and preventing backflow. Through the combined action of a PWM switching power supply circuit, an AC / DC switching circuit, and a backflow protection circuit, it achieves simultaneous support for AC and DC power supply on the same circuit board. This not only enables smooth switching from AC to DC but also provides an effective backflow protection mechanism, ensuring the safety and stability of the entire system. This not only enhances the adaptability and flexibility of the equipment but also provides users with a safer and more convenient user experience. This design meets the daily needs of ordinary users and also provides a convenient and safe modification path for technology enthusiasts seeking ultimate performance. This application is not only simple in structure but also has low manufacturing cost. Attached Figure Description
[0016] Figure 1 This is a block diagram illustrating the working principle of a circuit for freely switching between DC and AC input power and preventing backflow, according to this utility model.
[0017] Figure 2 This is a circuit diagram of a circuit for freely switching between DC and AC input power and preventing backflow, according to the present invention. Detailed Implementation
[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0019] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.
[0020] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.
[0021] This invention proposes a circuit for freely switching between DC and AC input power and preventing backflow.
[0022] In the embodiments of this utility model, such as Figure 1-2 As shown, this circuit for freely switching between DC and AC input power and preventing backflow includes an AC input terminal, a DC input terminal, a PWM switching power supply circuit, an AC-DC switching circuit, a backflow prevention protection circuit, and a DC output terminal. The AC input terminal is electrically connected to the AC-DC switching circuit; the AC-DC switching circuit is electrically connected to the PWM switching power supply circuit; the DC input terminal is electrically connected to the backflow prevention protection circuit; the backflow prevention protection circuit is electrically connected to the PWM switching power supply circuit; and the DC output terminal is electrically connected to the backflow prevention protection circuit.
[0023] In this embodiment, the AC / DC switching circuit includes a relay, a first transistor, a second transistor, a first diode, a first resistor, and a second resistor. The third and fifth pins of the relay are electrically connected, as are the fourth and sixth pins. The first pin of the relay is connected to a 12V voltage. One end of the first diode is electrically connected to the first pin of the relay, and the other end is electrically connected to the second pin of the relay. The collector of the first transistor is electrically connected to the first diode, the emitter of the first transistor is grounded, and the base of the first transistor is electrically connected to the collector of the second transistor. One end of the first resistor is electrically connected to the first diode, and the other end is electrically connected to the emitter of the second transistor. One end of the second resistor is electrically connected to the base of the second transistor, and the other end is grounded.
[0024] In this embodiment, the PWM switching power supply circuit includes a power management chip, an isolation transformer, a rectifier bridge, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a ninth diode, a thermistor, a transient voltage suppressor, an optocoupler, a rectifier filter circuit, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a third transistor, and a first MOSFET; The rectifier-filter circuit is electrically connected to the AC input terminal. The first capacitor and the transient voltage suppressor are connected in parallel, and the first capacitor and the transient voltage suppressor are positioned between the rectifier-filter circuit and the AC input terminal. One end of the thermistor is electrically connected to the transient voltage suppressor, and the other end is connected to an output port. The first terminal of the rectifier bridge is electrically connected to the rectifier-filter circuit. The second diode and the third diode are connected in parallel, with one end electrically connected to the first terminal of the rectifier bridge and the other end electrically connected to the third resistor. The eighth pin of the power management chip is electrically connected to the third resistor. The second terminal of the rectifier bridge is electrically connected to the third diode. One end of the first capacitor is connected to the fourth terminal of the rectifier bridge. One end is electrically connected to the first capacitor, and the other end is electrically connected to the third terminal of the rectifier bridge; the fourth, fifth, and sixth resistors and the second capacitor are connected in parallel, one end of which is electrically connected to the first capacitor, and the other end is electrically connected to the first pin of the isolation transformer; the seventh and eighth resistors are connected in parallel, one end of which is electrically connected to the fourth resistor, and the other end is electrically connected to one end of the fourth diode; the other end of the fourth diode is electrically connected to the third pin of the isolation transformer; one end of the third capacitor is electrically connected to the sixth pin of the power management chip, and the other end is grounded; the fifth diode and the ninth resistor are connected in series, one end of which is electrically connected to the fifth pin of the isolation transformer, and the other end is electrically connected to the third capacitor; the fourth... One end of the tenth resistor is electrically connected to the first pin of the power management chip, and the other end is electrically connected to the ninth resistor. One end of the eleventh resistor is electrically connected to the fifth pin of the power management chip, and the other end is electrically connected to the gate of the first MOSFET. The drain of the first MOSFET is electrically connected to the fifth diode. One end of the twelfth resistor is electrically connected to the third pin of the power management chip, and the other end is electrically connected to the source of the first MOSFET. The base of the third transistor is electrically connected to the fifth pin of the power management chip. The emitter of the third transistor is electrically connected to the eleventh resistor. One end of the thirteenth resistor is electrically connected to the fourth pin of the power management chip, and the other end is electrically connected to the collector of the third transistor.One end of the fourteenth resistor is electrically connected to the thirteenth resistor, and the other end is electrically connected to the drain of the first MOSFET. One end of the fourth capacitor is electrically connected to the twelfth resistor, and the other end is electrically connected to the fourth pin of the power management chip. One end of the fifth capacitor is electrically connected to the second pin of the power management chip, and the other end is electrically connected to the fourth pin of the power management chip. The fourth pin of the optocoupler is electrically connected to the second pin of the power management chip, and the third pin of the optocoupler is electrically connected to the fifth capacitor. The fifth diode and the sixth diode are connected in parallel, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the first voltage regulator circuit. The sixth capacitor and the tenth... Five resistors are connected in series, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the fifth diode. One end of the seventh capacitor is electrically connected to the sixth diode, and the other end is electrically connected to the ninth pin of the isolation transformer. The seventh and eighth diodes are connected in parallel, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to a second voltage regulator circuit. The eighth capacitor and the sixteenth resistor are connected in series, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to the seventh diode. One end of the ninth capacitor is electrically connected to the eighth diode, and the other end is grounded. The eighth pin of the isolation transformer is electrically connected to the ninth capacitor.
[0025] In this embodiment, the backflow prevention protection circuit includes a first backflow prevention protection circuit, a second backflow prevention protection circuit, and a third backflow prevention protection circuit. One end of the first backflow prevention protection circuit is electrically connected to the output terminal of the first voltage regulator circuit, and the other end is electrically connected to the second backflow prevention protection circuit. The first backflow prevention protection circuit is electrically connected to the second voltage regulator circuit. A third voltage regulator circuit is provided between the second voltage regulator circuit and the third backflow prevention protection circuit. One end of the third voltage regulator circuit is connected to the second voltage regulator circuit, and the other end is electrically connected to the third backflow prevention protection circuit.
[0026] In this embodiment, the first backflow prevention protection circuit includes a first ideal diode controller, a tenth capacitor, a seventeenth resistor, and a second MOSFET. One end of the tenth capacitor is grounded, and the other end is electrically connected to the first pin of the first ideal diode controller. The source of the second MOSFET is electrically connected to the first voltage regulator circuit, and the gate of the second MOSFET is electrically connected to the fifth pin of the first ideal diode controller. One end of the seventeenth resistor is electrically connected to the tenth capacitor, and the other end is electrically connected to the source of the second MOSFET. The fourth pin of the first ideal diode controller is electrically connected to the seventeenth resistor. The second and third pins of the first ideal diode controller are both grounded. The second and sixth pins of the first ideal diode controller are both electrically connected to the second backflow prevention protection circuit, and the drain of the second MOSFET is electrically connected to the sixth pin of the first ideal diode controller.
[0027] In this embodiment, the second backflow prevention circuit includes a second ideal diode controller, an eleventh capacitor, a twelfth capacitor, a nineteenth resistor, and a third MOSFET. The source of the third MOSFET is connected to a 12V voltage, the gate of the third MOSFET is electrically connected to the fifth pin of the second ideal diode controller, and the drain of the third MOSFET is electrically connected to the sixth pin of the second ideal diode controller. One end of the eleventh capacitor is grounded, and the other end is electrically connected to the source of the third MOSFET. The fourth pin of the second ideal diode controller is electrically connected to the eleventh capacitor. The nineteenth resistor and the twelfth capacitor are connected in series, one end of which is electrically connected to the fourth pin of the second ideal diode controller, and the other end is electrically connected to the second pin of the first ideal diode controller. The second pin of the second ideal diode controller is connected to the second pin of the first ideal diode controller, and the second pin of the second ideal diode controller is connected to the third pin of the second ideal diode controller.
[0028] In this embodiment, the third reverse current protection circuit includes a third ideal diode controller, a thirteenth capacitor, a twentieth resistor, and a fourth MOSFET. The source of the fourth MOSFET is electrically connected to the third voltage regulator circuit, and the drain of the fourth MOSFET is connected to a 5V voltage. The fourth pin of the third ideal diode controller is electrically connected to the source of the fourth MOSFET. The twentieth resistor and the thirteenth capacitor are connected in series, with one end grounded and the other end electrically connected to the source of the fourth MOSFET. The gate of the fourth MOSFET is electrically connected to the fifth pin of the third ideal diode controller. The sixth pin of the third ideal diode controller is electrically connected to the drain of the fourth MOSFET. The second and third pins of the third ideal diode controller are both grounded, and the first pin of the third ideal diode controller is electrically connected to the thirteenth capacitor.
[0029] Specifically, in practical applications, to enable a single circuit board to support both DC and AC power simultaneously, and to ensure that the power system does not malfunction or crash when both are connected at the same time, a DC priority strategy is adopted: when both DC and AC power are connected simultaneously, the system prioritizes using DC power.
[0030] This mechanism is achieved by switching the AC live wire using a set of relays K1. Once DC voltage is inserted, the high-voltage signal first passes through the first transistor Q6 and the second transistor Q7, causing relay K1 to disconnect the AC live wire, cut off the AC input, and switch to DC to power the DC input terminal.
[0031] When AC power is used as the input source, relay K1 employs normally closed technology. Current flows through the switch of relay K1, enabling the PWM switching power supply circuit to operate and providing stable +12V and +5V voltages to the entire device. If an external +12V or +5V DC power supply is connected, due to the DC input priority design, the 12V voltage acts on the base (B-level) of the PNP type second transistor Q7 through the first resistor R15, putting it at a low level, and the second transistor Q7 conducts. At this time, the second transistor Q7 provides a high level to the base of the NPN type first transistor Q6, causing the first transistor Q6 to conduct. After the first transistor Q6 conducts, current flows into the coil of relay K1 and generates a magnetic field, causing relay K1 to open, cutting off the AC circuit L, and the PWM switching power supply circuit to stop working, effectively avoiding AC / DC power supply conflicts.
[0032] Under DC power supply, the base (B-terminal) of the second transistor Q7 receives a low-level signal, turning on the PNP transistor Q7. This, in turn, provides a high-level signal to the NPN transistor Q6, turning on Q6. At this time, the coil of relay K1 is energized, causing relay K1 to open and disconnecting the AC circuit L.
[0033] When the DC input is interrupted, the normally closed design of relay K1 comes into play. The base of the second transistor Q7 is grounded, and the base of the first transistor Q6 is at a low level. The first transistor Q6 is not conducting, and relay K1 returns to its normally closed state, reconnecting the AC live wire L and automatically switching back to AC power supply mode to supply power to the AC input terminal.
[0034] To prevent the 12V DC voltage generated during AC power supply from flowing back into relay K1 and causing it to malfunction and cut off the AC input power, a second ideal diode controller U8 is selected in conjunction with a third MOSFET Q9 for control, effectively preventing the DC voltage generated on the AC side from affecting the working state of relay K1.
[0035] When using DC power supply, in order to prevent DC voltage from flowing back to the AC input terminal and damaging the first voltage regulator circuit U6, the second voltage regulator circuit U4 and the third voltage regulator circuit U5, the first ideal diode controller U7 and the third ideal diode controller U9 are used respectively, in conjunction with the first MOSFET Q4 and the fourth MOSFET Q10, to ensure that the DC power supply does not flow back into the AC circuit and to protect each component.
[0036] Specifically, for the 12V DC power supply path, a first ideal diode controller U7 is used in conjunction with a second MOSFET Q4 to prevent voltage backflow into the AC circuit, protecting the first voltage regulator circuit. Similarly, for the 5V DC power supply path, a third ideal diode controller U9 is used in conjunction with a fourth MOSFET Q10 to prevent voltage backflow into the AC circuit, protecting the second and third voltage regulator circuits. The first ideal diode controller U7 and the third ideal diode controller U9 have characteristics such as low quiescent current, ultra-low shutdown current, regulated forward voltage, and fast reverse current response, enabling them to drive external N-channel second MOSFET Q4 and fourth MOSFET Q10 to achieve ultra-low voltage drop and negligible reverse current.
[0037] It should be noted that the first ideal diode controller, second ideal diode controller, and third ideal diode controller in this application can be divided into two categories based on the gate control mechanisms of the second MOSFET Q4, third MOSFET Q9, and fourth MOSFET Q10: linear regulation control and hysteresis on / off control. This application uses hysteresis on / off control. In hysteresis on / off control, when the forward comparator threshold VFWD_ON is exceeded, the second MOSFET Q4 is fully turned on. When the reverse comparator threshold VREV_OFF is reached, the gate of the second MOSFET is fully enhanced, and the source voltage of the second MOSFET is not controlled by the load current. When the reverse current VREV_OFF / RDS(ON) is reached, the second MOSFET Q4 is turned off. However, it should be noted that if the reverse current is less than VREV_OFF / RDS(ON), the second MOSFET Q4 cannot be turned off. In summary, the first ideal diode controller U7 controls the second MOSFET Q4 to prevent the 12V DC input voltage from flowing back into the AC and damaging the first voltage regulator circuit. The third ideal diode controller U9 controls the fourth MOSFET Q10 to prevent the 5V DC input voltage from flowing back into the AC and damaging the second and third voltage regulator circuits. The first ideal diode controller U7 and the third ideal diode controller U9 control the second MOSFET Q4 and the fourth MOSFET Q10 respectively to prevent current backflow from damaging the circuit components. The second ideal diode U8 controls the third MOSFET Q9 to ensure that the 12V generated by the AC input voltage is backflowed into the coil and control pin of the relay K1 while ensuring that the DC input power supply is normal, thus avoiding the relay K1 from malfunctioning and causing abnormal power supply to the product.
[0038] This design not only achieves seamless switching between DC and AC power supply but also effectively prevents various potential risks caused by current backflow, ensuring system stability and reliability. This solution meets the daily needs of ordinary users while also providing a safe and convenient modification option for technology enthusiasts seeking ultimate performance.
[0039] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.
Claims
1. A circuit for freely switching between DC and AC input power and preventing backflow, characterized in that, It includes an AC input terminal, a DC input terminal, a PWM switching power supply circuit, an AC-DC switching circuit, a backflow prevention protection circuit, and a DC output terminal; the AC input terminal is electrically connected to the AC-DC switching circuit; the AC-DC switching circuit is electrically connected to the PWM switching power supply circuit; the DC input terminal is electrically connected to the backflow prevention protection circuit; the backflow prevention protection circuit is electrically connected to the PWM switching power supply circuit; and the DC output terminal is electrically connected to the backflow prevention protection circuit.
2. The circuit for freely switching between DC and AC input power and preventing backflow as described in claim 1, characterized in that, The AC / DC switching circuit includes a relay, a first transistor, a second transistor, a first diode, a first resistor, and a second resistor. The third and fifth pins of the relay are electrically connected, as are the fourth and sixth pins. The first pin of the relay is connected to a 12V voltage. One end of the first diode is electrically connected to the first pin of the relay, and the other end is electrically connected to the second pin. The collector of the first transistor is electrically connected to the first diode, the emitter of the first transistor is grounded, and the base of the first transistor is electrically connected to the collector of the second transistor. One end of the first resistor is electrically connected to the first diode, and the other end is electrically connected to the emitter of the second transistor. One end of the second resistor is electrically connected to the base of the second transistor, and the other end is grounded.
3. The circuit for free switching between DC and AC input power and anti-backflow as described in claim 2, characterized in that, The PWM switching power supply circuit includes a power management chip, an isolation transformer, a rectifier bridge, second diodes, third diodes, fourth diodes, fifth diodes, sixth diodes, seventh diodes, eighth diodes, and ninth diodes, a thermistor, a transient voltage suppressor, an optocoupler, a rectifier filter circuit, first capacitors, second capacitors, third capacitors, fourth capacitors, fifth capacitors, sixth capacitors, seventh capacitors, eighth capacitors, and ninth capacitors, third resistors, fourth resistors, fifth resistors, sixth resistors, seventh resistors, eighth resistors, ninth resistors, tenth resistors, eleventh resistors, twelfth resistors, thirteenth resistors, fourteenth resistors, fifteenth resistors, sixteenth resistors, a third transistor, and a first MOSFET; the rectifier filter... The circuit is electrically connected to the AC input terminal. The first capacitor and the transient voltage suppressor are connected in parallel, and the first capacitor and the transient voltage suppressor are positioned between the rectifier filter circuit and the AC input terminal. One end of the thermistor is electrically connected to the transient voltage suppressor, and the other end is connected to an output port. The first terminal of the rectifier bridge is electrically connected to the rectifier filter circuit. The second diode and the third diode are connected in parallel, with one end electrically connected to the first terminal of the rectifier bridge and the other end electrically connected to the third resistor. The eighth pin of the power management chip is electrically connected to the third resistor. The second terminal of the rectifier bridge is electrically connected to the third diode. One end of the first capacitor is electrically connected to the fourth terminal of the rectifier bridge. The other end is electrically connected to the third terminal of the rectifier bridge; the fourth, fifth, and sixth resistors and the second capacitor are connected in parallel, one end of which is electrically connected to the first capacitor, and the other end is electrically connected to the first pin of the isolation transformer; the seventh and eighth resistors are connected in parallel, one end of which is electrically connected to the fourth resistor, and the other end is electrically connected to one end of the fourth diode; the other end of the fourth diode is electrically connected to the third pin of the isolation transformer; one end of the third capacitor is electrically connected to the sixth pin of the power management chip, and the other end is grounded; the fifth diode and the ninth resistor are connected in series, one end of which is electrically connected to the fifth pin of the isolation transformer, and the other end is electrically connected to the third capacitor; the tenth... One end of the resistor is electrically connected to the first pin of the power management chip, and the other end is electrically connected to the ninth resistor. One end of the eleventh resistor is electrically connected to the fifth pin of the power management chip, and the other end is electrically connected to the gate of the first MOSFET. The drain of the first MOSFET is electrically connected to the fifth diode. One end of the twelfth resistor is electrically connected to the third pin of the power management chip, and the other end is electrically connected to the source of the first MOSFET. The base of the third transistor is electrically connected to the fifth pin of the power management chip. The emitter of the third transistor is electrically connected to the eleventh resistor. One end of the thirteenth resistor is electrically connected to the fourth pin of the power management chip, and the other end is electrically connected to the collector of the third transistor.One end of the fourteenth resistor is electrically connected to the thirteenth resistor, and the other end is electrically connected to the drain of the first MOSFET. One end of the fourth capacitor is electrically connected to the twelfth resistor, and the other end is electrically connected to the fourth pin of the power management chip. One end of the fifth capacitor is electrically connected to the second pin of the power management chip, and the other end is electrically connected to the fourth pin of the power management chip. The fourth pin of the optocoupler is electrically connected to the second pin of the power management chip, and the third pin of the optocoupler is electrically connected to the fifth capacitor. The fifth diode and the sixth diode are connected in parallel, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the first voltage regulator circuit. The sixth capacitor and the tenth... Five resistors are connected in series, one end of which is electrically connected to the tenth pin of the isolation transformer, and the other end is electrically connected to the fifth diode. One end of the seventh capacitor is electrically connected to the sixth diode, and the other end is electrically connected to the ninth pin of the isolation transformer. The seventh and eighth diodes are connected in parallel, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to a second voltage regulator circuit. The eighth capacitor and the sixteenth resistor are connected in series, one end of which is electrically connected to the seventh pin of the isolation transformer, and the other end is electrically connected to the seventh diode. One end of the ninth capacitor is electrically connected to the eighth diode, and the other end is grounded. The eighth pin of the isolation transformer is electrically connected to the ninth capacitor.
4. The circuit for free switching between DC and AC input power and anti-backflow as described in claim 3, characterized in that, The backflow prevention protection circuit includes a first backflow prevention protection circuit, a second backflow prevention protection circuit, and a third backflow prevention protection circuit. One end of the first backflow prevention protection circuit is electrically connected to the output terminal of the first voltage regulator circuit, and the other end is electrically connected to the second backflow prevention protection circuit. The first backflow prevention protection circuit is electrically connected to the second voltage regulator circuit. A third voltage regulator circuit is provided between the second voltage regulator circuit and the third backflow prevention protection circuit. One end of the third voltage regulator circuit is connected to the second voltage regulator circuit, and the other end is electrically connected to the third backflow prevention protection circuit.
5. The circuit for free switching between DC and AC input power and anti-backflow as described in claim 4, characterized in that, The first backflow prevention protection circuit includes a first ideal diode controller, a tenth capacitor, a seventeenth resistor, and a second MOSFET. One end of the tenth capacitor is grounded, and the other end is electrically connected to the first pin of the first ideal diode controller. The source of the second MOSFET is electrically connected to the first voltage regulator circuit, and the gate of the second MOSFET is electrically connected to the fifth pin of the first ideal diode controller. One end of the seventeenth resistor is electrically connected to the tenth capacitor, and the other end is electrically connected to the source of the second MOSFET. The fourth pin of the first ideal diode controller is electrically connected to the seventeenth resistor. The second and third pins of the first ideal diode controller are both grounded. The second and sixth pins of the first ideal diode controller are both electrically connected to the second backflow prevention protection circuit. The drain of the second MOSFET is electrically connected to the sixth pin of the first ideal diode controller.
6. The circuit for free switching between DC and AC input power and anti-backflow as described in claim 5, characterized in that, The second reverse current protection circuit includes a second ideal diode controller, an eleventh capacitor, a twelfth capacitor, a nineteenth resistor, and a third MOSFET. The source of the third MOSFET is connected to a 12V voltage, the gate of the third MOSFET is electrically connected to the fifth pin of the second ideal diode controller, and the drain of the third MOSFET is electrically connected to the sixth pin of the second ideal diode controller. One end of the eleventh capacitor is grounded, and the other end is electrically connected to the source of the third MOSFET. The fourth pin of the second ideal diode controller is electrically connected to the eleventh capacitor. The nineteenth resistor and the twelfth capacitor are connected in series, one end of which is electrically connected to the fourth pin of the second ideal diode controller, and the other end is electrically connected to the second pin of the first ideal diode controller. The second pin of the second ideal diode controller is connected to the second pin of the first ideal diode controller, and the second pin of the second ideal diode controller is connected to the third pin of the second ideal diode controller.
7. The circuit for free switching between DC and AC input power and anti-backflow as described in claim 4, characterized in that, The third backflow protection circuit includes a third ideal diode controller, a thirteenth capacitor, a twentieth resistor, and a fourth MOSFET. The source of the fourth MOSFET is electrically connected to the third voltage regulator circuit, and the drain of the fourth MOSFET is connected to a 5V voltage. The fourth pin of the third ideal diode controller is electrically connected to the source of the fourth MOSFET. The twentieth resistor and the thirteenth capacitor are connected in series, with one end grounded and the other end electrically connected to the source of the fourth MOSFET. The gate of the fourth MOSFET is electrically connected to the fifth pin of the third ideal diode controller. The sixth pin of the third ideal diode controller is electrically connected to the drain of the fourth MOSFET. The second and third pins of the third ideal diode controller are both grounded, and the first pin of the third ideal diode controller is electrically connected to the thirteenth capacitor.