Power supply circuit and electronic equipment

Abstract

The invention provides a power supply circuit and electronic equipment, and relates to the technical field of power supplies, the power supply circuit comprises a first direct current end, a second direct current end, a DC / DC conversion circuit, a current detection circuit and a switching circuit, the input end of the DC / DC conversion circuit is connected with the first direct current end; the input end of the current detection circuit is connected with the output end of the DC / DC conversion circuit; the switching circuit is connected in series between the current detection circuit and the second direct current end, and the switching circuit is electrically connected with the output end of the current detection circuit; the switching circuit is used for switching on a path between the output end of the DC / DC conversion circuit and the second direct current end under the condition that the current output by the DC / DC conversion circuit is determined to be greater than a first preset current threshold value based on the current detection signal; and the switching circuit is used for disconnecting a path between the output end of the DC / DC conversion circuit and the second direct current end based on the current detection signal under the condition that the current output by the DC / DC conversion circuit is less than a second preset current threshold, so that the conversion efficiency can be improved, and the driving loss can be reduced.

Description

Technical Field

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

[0002] In existing DC-DC converters, under low current conditions, the continuous conduction of the synchronous rectifier tube will generate unnecessary drive losses, which not only wastes energy but also severely restricts the efficiency improvement potential under light load conditions. Summary of the Invention

[0003] The main objective of this invention is to provide a power supply circuit that aims to reduce the driving losses of the power supply circuit.

[0004] To achieve the above objectives, the present invention provides a power supply circuit, the power supply circuit comprising: The first DC terminal is used to connect an externally input first DC voltage. The second DC terminal is used to output a second DC voltage. A DC / DC conversion circuit, wherein the input terminal of the DC / DC conversion circuit is connected to the first DC terminal, and the DC / DC conversion circuit is used to convert the first DC voltage into the second DC voltage; A current detection circuit is provided, wherein the input terminal of the current detection circuit is connected to the output terminal of the DC / DC conversion circuit, and the current detection circuit is used to detect the current output by the DC / DC conversion circuit and output a corresponding current detection signal. A switching circuit is connected in series between the current detection circuit and the second DC terminal, and the controlled terminal of the switching circuit is electrically connected to the output terminal of the current detection circuit. The switching circuit is configured to, based on the current detection signal, determine if the current output by the DC / DC conversion circuit is greater than a first preset current threshold, and then connect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal; the switching circuit is configured to, based on the current detection signal, determine if the current output by the DC / DC conversion circuit is less than a second preset current threshold, and then disconnect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal.

[0005] Optionally, the current detection circuit includes: A current sensing resistor, the first end of which is connected to the output terminal of the DC / DC conversion circuit, and the second end of which is connected to the second DC terminal.

[0006] Optionally, the switching circuit includes: A switch branch is connected in series between the current sensing resistor and the second DC terminal; A switch driving circuit is provided, wherein the controlled terminal of the switch driving circuit is connected to the first terminal of the current sensing resistor. The switch driving circuit is used to control the switch branch to conduct the path between the output terminal of the DC / DC conversion circuit and the second DC terminal when the voltage drop of the current sensing resistor is greater than a first preset voltage drop threshold; and to control the switch branch to disconnect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal when the voltage drop of the current sensing resistor is less than a second preset voltage drop threshold. Specifically, when the voltage drop across the current sensing resistor is greater than a first preset voltage drop threshold, the current detection circuit detects that the current output by the DC / DC conversion circuit is greater than a first preset current threshold; when the voltage drop across the current sensing resistor is less than a second preset voltage drop threshold, the current detection circuit detects that the current output by the DC / DC conversion circuit is less than a second preset current threshold.

[0007] Optionally, the switch driving circuit includes: A first diode, wherein a first resistor is connected in series between the cathode of the first diode and the second terminal of the current sensing resistor; The second resistor has a first end connected to the first power supply terminal and a second end connected to the positive terminal of the first diode. The first transistor has a third resistor connected in series between its base and the anode of the first diode, and its emitter is connected to the first terminal of the current sensing resistor. The fourth resistor has a first end connected to the first power supply terminal and a second end connected to the collector of the first transistor. The base of the second transistor is connected to the collector of the first transistor, the collector of the second transistor is connected to the first terminal of the current sensing resistor, and the emitter of the second transistor is connected to the controlled terminal of the switching circuit. The fifth resistor has its first end connected to the emitter of the second transistor, and its second end connected to the first power supply terminal.

[0008] Optionally, the power supply circuit includes: The self-driven power supply circuit has its power input terminal connected to the output terminal of the DC / DC conversion circuit, and its power output terminal connected to the power input terminal of the switch drive circuit.

[0009] Optionally, the self-driven power supply circuit includes: The first capacitor has its first terminal connected to the first output terminal of the DC / DC conversion circuit, and its second terminal connected to the second output terminal of the DC / DC conversion circuit. or, The transformer of the DC / DC conversion circuit includes an auxiliary secondary winding, which is connected to the power input terminal of the switch drive circuit.

[0010] Optionally, the power supply circuit further includes: A step-down circuit is provided, wherein the input terminal of the step-down circuit is connected to the output terminal of the self-driven power supply circuit, and the output terminal of the step-down circuit is connected to the power input terminal of the switch drive circuit. The step-down circuit is used to reduce the voltage output by the self-driven power supply circuit and then output it to the switch drive circuit.

[0011] Optionally, the DC / DC conversion circuit includes: A first conversion circuit, wherein the input terminal of the first conversion circuit is connected to the first DC terminal, and the first conversion circuit is used to convert the first DC voltage connected to the first DC terminal into a first AC power supply. A transformer, wherein the primary winding of the transformer is connected to the output terminal of the first conversion circuit; The second conversion circuit has a first input terminal connected to the first terminal of the secondary winding of the transformer, and a second input terminal connected to the third terminal of the secondary winding of the transformer. A filter circuit, wherein the input terminal of the filter circuit is connected to the output terminal of the second conversion circuit, and the output terminal of the filter circuit is connected to the input terminal of the current detection circuit.

[0012] Optionally, the second conversion circuit includes: First switching transistor; The drain of the second switch is connected to the source of the first switch, and the common node of the first switch and the second switch is connected to the first end of the secondary winding of the transformer. The third switching transistor, the drain of which is connected to the drain of the first switching transistor; The fourth switch is connected to the source of the third switch, and the source of the fourth switch is connected to the source of the second switch. The common node of the third and fourth switches is connected to the third terminal of the secondary winding of the transformer. The power supply circuit also includes: A rectifier switch driving circuit is provided, wherein the controlled terminal of the rectifier switch driving circuit is electrically connected to the switch driving circuit of the switch circuit, and the rectifier switch driving circuit is used to control the synchronous switching state of the second switch and the fourth switch.

[0013] In addition, to achieve the above objectives, the present invention also provides an electronic device including the power supply circuit described above.

[0014] This invention embodiment includes a first DC terminal, a second DC terminal, a DC / DC conversion circuit, a current detection circuit, and a switching circuit. First, the first DC terminal is used to connect to an externally input first DC voltage. Then, the second DC terminal is used to output a second DC voltage. The input terminal of the DC / DC conversion circuit is connected to the first DC terminal, and the input terminal of the current detection circuit is connected to the output terminal of the DC / DC conversion circuit. Finally, the switching circuit is connected in series between the current detection circuit and the second DC terminal, and the controlled terminal of the switching circuit is electrically connected to the output terminal of the current detection circuit. The DC / DC conversion circuit converts the first DC voltage to the second DC voltage. The current detection circuit detects the current output by the DC / DC conversion circuit and outputs a corresponding current detection signal. Based on the current detection signal, if the current output by the DC / DC conversion circuit is greater than a first preset current threshold, the switching circuit opens the path between the output terminal of the DC / DC conversion circuit and the second DC terminal. Alternatively, based on the current detection signal, if the current output by the DC / DC conversion circuit is less than a second preset current threshold, the switching circuit closes the path between the output terminal of the DC / DC conversion circuit and the second DC terminal. In this way, by monitoring the output current of the DC / DC conversion circuit in real time through the current detection circuit, and dynamically controlling the switching circuit based on the current detection signal, intelligent switching control triggered by the current threshold can be achieved, which can improve the response speed and conversion efficiency, and reduce drive losses. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a circuit block diagram of a power supply circuit according to an embodiment of the present invention; Figure 2 for Figure 1 The circuit diagram of the power supply circuit; Figure 3 This is a circuit block diagram of a power supply circuit according to another embodiment of the present invention; Figure 4 This is a circuit schematic diagram of a power supply circuit according to another embodiment of the present invention; Figure 5 Here is a circuit block diagram of a power supply circuit according to another embodiment of the present invention; Figure 6 This is a circuit schematic diagram of a power supply circuit according to another embodiment of the present invention; Figure 7 This is a circuit block diagram of a power supply circuit according to another embodiment of the present invention; Figure 8 This is a circuit block diagram of a power supply circuit according to another embodiment of the present invention; Figure 9 for Figure 8 The circuit diagram of the power supply circuit; Figure 10 Here is a circuit block diagram of a power supply circuit according to another embodiment of the present invention; Figure 11 for Figure 10 The circuit diagram of the rectifier switch drive circuit.

[0018] Explanation of icon numbers:

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Well-known modules, units, and their connections, links, communications, or operations are not shown or described in detail. Furthermore, the described features, architectures, or functions can be combined in any way in one or more embodiments. Those skilled in the art should understand that the various embodiments described below are only for illustrative purposes and not for limiting the scope of protection of the present invention. It is also readily understood that the modules, units, or processing methods in the various embodiments described herein and shown in the accompanying drawings can be combined and designed in various different configurations. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The definitions of various terms or methods used in the following embodiments are, except where logically impossible, generally defined as broad concepts that can be implemented under the premise of the content disclosed in the embodiments. Under this understanding, all specific subordinate limitations of the terms or methods should be considered as part of the invention and should not be narrowly interpreted or biased simply because the specification does not disclose such a specific limitation. Similarly, provided that it is logically feasible, the order of the steps in the method is flexible and varied, and all specific subordinate limitations in the broad concepts of various terms or methods fall within the scope of protection of this invention.

[0022] With the widespread application of DC-DC converters, synchronous rectification technology has become a key means to improve power conversion efficiency. In traditional solutions, when the system needs to achieve high current transmission or high efficiency, MOSFETs are usually used instead of diodes to reduce conduction losses. However, existing technologies have obvious control defects: the MOSFET drive signal is usually generated directly by the microcontroller, which not only increases the microcontroller's I / O resource usage, but also leads to insufficient response speed due to software control delay, easily causing false turn-on accidents.

[0023] More importantly, current mainstream solutions generally employ voltage control strategies, which cannot intelligently adjust the operating mode of the switching transistors based on the actual current conditions. Under low-current conditions, the continuous conduction of the synchronous rectifier transistor generates unnecessary drive losses, which not only wastes energy but also severely limits the potential for efficiency improvement under light load conditions. This coarse-grained control method cannot meet the needs of refined management, nor can it adapt to the requirements of modern electronic equipment for high-efficiency and intelligent power systems.

[0024] To solve the above problems, refer to Figure 1 and Figure 2 In one embodiment of the present invention, the power supply circuit includes a first DC terminal 10, a second DC terminal 50, a DC / DC conversion circuit 20, a current detection circuit 30, and a switching circuit 40, wherein: The first DC terminal 10 is used to receive an externally input first DC voltage; the second DC terminal 50 is used to output a second DC voltage; the input terminal of the DC / DC conversion circuit 20 is connected to the first DC terminal 10, and the DC / DC conversion circuit 20 is used to convert the first DC voltage into the second DC voltage; the input terminal of the current detection circuit 30 is connected to the output terminal of the DC / DC conversion circuit 20, and the current detection circuit 30 is used to detect the current output by the DC / DC conversion circuit 20 and output a corresponding current detection signal; the switching circuit 40 is connected in series between the current detection circuit 30 and the second DC terminal 50, and the controlled terminal of the switching circuit 40 is electrically connected to the output terminal of the current detection circuit 30. The switching circuit 40 is used to connect the path between the output terminal of the DC / DC conversion circuit 20 and the second DC terminal 50 when the current output of the DC / DC conversion circuit 20 is greater than the first preset current threshold based on the current detection signal. The switching circuit 40 is used to disconnect the path between the output terminal of the DC / DC conversion circuit 20 and the second DC terminal 50 when the current output of the DC / DC conversion circuit 20 is less than the second preset current threshold, based on the current detection signal.

[0025] The DC / DC conversion circuit 20 refers to a topology employing alternating dual-switch conduction, which can be implemented using a half-bridge or full-bridge configuration, and voltage conversion is achieved through coupling via transformer 22. The current detection circuit 30 is a sensing unit capable of converting current signals into voltage signals, which can be implemented using a series sampling resistor and a differential amplifier. Its output is connected to a threshold comparator to generate a logic signal. The switching circuit 40 is a power semiconductor device with controlled conduction capability, which can be implemented using a field-effect transistor or an insulated-gate bipolar transistor. Its gate drive signal is directly controlled by the logic level output from the detection circuit.

[0026] In this system, after the first DC terminal 10 is connected to an external DC power supply, the DC / DC conversion circuit 20 converts the input voltage into an AC signal through high-frequency switching. This signal is then coupled through transformer 22 and rectified by the secondary winding to output the target DC voltage. The current detection circuit 30 acquires real-time current information through a sensing element connected in series in the output circuit. When the detected value exceeds a preset upper limit, it triggers the switching circuit 40 to conduct, ensuring a low-impedance path is established under high-current conditions. When the detected value is below a preset lower limit, it disconnects the switching device to avoid ineffective drive losses under light load conditions. This control logic enables the system to dynamically adjust the energy transmission path according to actual load requirements, achieving optimal efficiency operation.

[0027] Compared to existing technologies, this embodiment directly establishes a current-switch state mapping relationship through hardware circuitry, eliminating the risk of malfunction caused by signal transmission delay. A current threshold control mechanism replaces the traditional voltage control mode, ensuring that the switching device is activated only under necessary load conditions, fundamentally solving the efficiency bottleneck problem under light loads. The independent closed-loop control architecture reduces the resource requirements of the main control chip and simplifies system design complexity.

[0028] Through the above technical solution, this embodiment achieves adaptive synchronous rectification control with load current, maintaining low conduction loss under heavy load conditions and automatically cutting off the drive circuit to reduce ineffective power consumption under light load conditions. This design effectively balances energy efficiency performance under different load conditions, especially significantly reducing energy waste in low-current operating mode.

[0029] This embodiment includes a first DC terminal 10, a second DC terminal 50, a DC / DC conversion circuit 20, a current detection circuit 30, and a switching circuit 40. First, the first DC terminal 10 is used to connect to an externally input first DC voltage. Then, the second DC terminal 50 is used to output a second DC voltage. The input terminal of the DC / DC conversion circuit 20 is connected to the first DC terminal 10, and the input terminal of the current detection circuit 30 is connected to the output terminal of the DC / DC conversion circuit 20. Finally, the switching circuit 40 is connected in series between the current detection circuit 30 and the second DC terminal 50, and the controlled terminal of the switching circuit 40 is electrically connected to the output terminal of the current detection circuit 30. The DC / DC conversion circuit... DC / DC converter circuit 20 is used to convert a first DC voltage to a second DC voltage. Current detection circuit 30 is used to detect the current output by DC / DC converter circuit 20 and output a corresponding current detection signal. Switching circuit 40, based on the current detection signal, determines whether the current output by DC / DC converter circuit 20 is greater than a first preset current threshold. If so, it opens the path between the output terminal of DC / DC converter circuit 20 and the second DC terminal 50. If, based on the current detection signal, the current output by DC / DC converter circuit 20 is less than a second preset current threshold, it closes the path between the output terminal of DC / DC converter circuit 20 and the second DC terminal 50. Thus, by real-time monitoring of the output current of DC / DC converter circuit 20 by current detection circuit 30 and dynamic control of switching circuit 40 based on the current detection signal, intelligent switching control triggered by current threshold is achieved, which can improve response speed and conversion efficiency while reducing drive losses.

[0030] Optionally, refer to Figure 2 Another embodiment of the present invention provides a power supply circuit based on the above. Figure 1 and Figure 2 In the embodiment shown, the current detection circuit 30 includes a current sensing resistor Cs, wherein: The first end of the current sensing resistor Cs is connected to the output terminal of the DC / DC conversion circuit 20, and the second end of the current sensing resistor Cs is connected to the second DC terminal 50.

[0031] The current sensing resistor Cs is a component connected in series in the circuit to convert the current signal into a voltage signal. It can be a metal film resistor or an alloy resistor with a resistance range of 0.1 milliohms to 100 milliohms. This resistor converts the current flowing through the DC / DC conversion circuit 20 into a corresponding voltage drop signal through Ohm's law, providing a control basis for the subsequent switch drive circuit 42.

[0032] In this circuit, the current sensing resistor Cs is directly connected in series between the output terminal of the DC / DC converter circuit 20 and the second DC terminal 50, forming a current detection loop. When the current output by the DC / DC converter circuit 20 flows through this resistor, a voltage drop proportional to the current magnitude is generated across it. This voltage drop signal is transmitted to the switch drive circuit 42 as a reference signal to determine whether to trigger a switch action. For example, when the detected voltage drop exceeds a first preset voltage drop threshold, it indicates that the loop current has reached the operating current magnitude. At this time, the switch drive circuit 42 immediately responds and controls the switch branch 41 to conduct, so as to supply power to the DC / DC converter circuit 20.

[0033] This embodiment establishes a current-to-voltage conversion link directly by physically connecting the current sensing resistor Cs in series, achieving real-time detection without the need for an additional control interface. It also avoids transmission delay of the drive signal between the MCU and the switching circuit 40. This embodiment enables real-time monitoring and control of the output current of the DC / DC conversion circuit 20, and can actively cut off the synchronous rectifier drive signal under light load conditions, eliminating unnecessary drive energy loss.

[0034] Optionally, refer to Figure 3 Another embodiment of the present invention provides a power supply circuit based on the above. Figure 2 In the embodiment shown, the switching circuit 40 includes a switching branch 41 and a switching drive circuit 42, wherein: The switch branch 41 is connected in series between the current sensing resistor Cs and the second DC terminal 50; the controlled terminal of the switch driving circuit 42 is connected to the first terminal of the current sensing resistor Cs. The switch driving circuit 42 is used to control the switch branch 41 to conduct the path between the output terminal of the DC / DC conversion circuit 20 and the second DC terminal 50 when the voltage drop of the current sensing resistor Cs is greater than a first preset voltage drop threshold; and to control the switch branch 41 to disconnect the path between the output terminal of the DC / DC conversion circuit 20 and the second DC terminal 50 when the voltage drop of the current sensing resistor Cs is less than a second preset voltage drop threshold. Specifically, when the voltage drop across the current sensing resistor Cs is greater than a first preset voltage drop threshold, the current detection circuit 30 detects that the current output by the DC / DC conversion circuit 20 is greater than a first preset current threshold; when the voltage drop across the current sensing resistor Cs is less than a second preset voltage drop threshold, the current detection circuit 30 detects that the current output by the DC / DC conversion circuit 20 is less than a second preset current threshold.

[0035] In this circuit, the switch branch 41 refers to the controllable conductive path connected in series in the current detection loop, which can be implemented using a power MOSFET or IGBT device. In this embodiment, a single MOSFET can be used preferentially. The on-resistance of the switch branch 41 directly affects the current detection accuracy; therefore, a semiconductor device with low on-resistance should be selected to reduce additional losses. The switch drive circuit 42 refers to the circuit module that generates drive logic based on the current detection signal, which can be implemented using a transistor. By setting two voltage drop thresholds to form a hysteresis range, frequent switching of the switch state under high-frequency fluctuations can be avoided.

[0036] When the output current of the DC / DC converter circuit 20 increases, the current flowing through the current sensing resistor Cs rises, and the voltage drop across it exceeds a first preset voltage drop threshold. At this time, the switch drive circuit 42 transmits a drive signal to the control terminal of the switch branch 41, causing the switch branch 41 to conduct and form a low-impedance path. When the output current decreases, causing the voltage drop to fall below a second preset threshold, the drive circuit immediately cuts off the control signal of the switch branch 41, causing the current path to switch to a high-impedance state. This control process is entirely based on real-time current detection and does not require the intervention of an external controller.

[0037] This embodiment establishes closed-loop control directly at the current sensing stage, achieving rapid response through hardware circuitry. Compared to synchronous rectification control based on voltage sensing, current threshold control can precisely match the load state, actively cutting off the switching branch 41 under light load conditions to avoid ineffective drive losses. Through this current threshold control mechanism, this embodiment ensures a low conduction loss path under heavy load and automatically cuts off the drive circuit under light load, optimizing the overall efficiency of the power supply circuit under different load conditions.

[0038] Optionally, refer to Figure 4 In another embodiment of the present invention, a power supply circuit is provided, based on the above... Figure 3 In the embodiment shown, the switch driving circuit 42 includes a first diode D1, a first resistor R4, a second resistor R2, a first transistor P2, a third resistor R3, a second transistor P1, a fourth resistor R1, and a fifth resistor R5, wherein: A first resistor R4 is connected in series between the cathode of the first diode D1 and the second terminal of the current sensing resistor Cs; the first terminal of the second resistor R2 is connected to the first power supply terminal, and the second terminal of the second resistor R2 is connected to the anode of the first diode D1; a third resistor R3 is connected in series between the base of the first transistor P2 and the anode of the first diode D1, and the emitter of the first transistor P2 is connected to the first terminal of the current sensing resistor Cs; the first terminal of the fourth resistor R1 is connected to the first power supply terminal, and the second terminal of the fourth resistor R1 is connected to the collector of the first transistor P2; the base of the second transistor P1 is connected to the collector of the first transistor P2, the collector of the second transistor P1 is connected to the first terminal of the current sensing resistor Cs, and the emitter of the second transistor P1 is connected to the controlled terminal of the switching circuit 40; the first terminal of the fifth resistor R5 is connected to the emitter of the second transistor P1, and the second terminal of the fifth resistor R5 is connected to the first power supply terminal.

[0039] In this circuit, the first diode D1 is a unidirectional conducting element, which can be implemented using a silicon-based semiconductor device, and is used to prevent reverse current from flowing into the drive circuit. The third resistor R3 is a current-limiting element, which can be implemented using a carbon film resistor, and is used to limit the base current to prevent overload. The fourth resistor R1 is a pull-up element, which can be implemented using a metal film resistor, and is used to maintain a stable collector potential. The first transistor P2 is a current amplification element, which can be implemented using an NPN transistor, and is used to convert the detection signal into a drive signal. The second transistor P1 is a power switching element, which can be implemented using a PNP transistor, and is used to control the on / off state of the main switch branch 41. The fifth resistor R5 is a biasing element, which can be implemented using a surface-mount resistor, and is used to set the emitter operating point.

[0040] When the current sensing resistor Cs generates a voltage drop, this voltage drop flows through the first resistor R4 and the first diode D1, causing a voltage drop in the first diode D1, thereby applying a corresponding voltage to the base of the first transistor P2. When the voltage drop exceeds the conduction threshold, the first transistor P2 conducts, causing the fourth resistor R1 to form a voltage divider, driving the second transistor P1 to conduct and thus controlling the closing of the switching branch 41. When the voltage drop falls below the turn-off threshold, the first transistor P2 turns off, causing the base of the second transistor P1 to lose voltage, and the switching branch 41 immediately opens. Through the two-stage transistor amplification structure, the response threshold of the switching action can be precisely controlled.

[0041] This embodiment implements threshold judgment and switching control through pure hardware circuitry, eliminating the digital signal processing stage and improving response speed to the microsecond level. Simultaneously, the bipolar transistor combination structure avoids the complex level conversion circuitry required for MOSFET driving. This embodiment achieves real-time current detection and control of the synchronous rectifier switch, automatically turning on the low-impedance path when the load current exceeds a set threshold, significantly reducing conduction losses. When the load current falls below a safe threshold, the path is quickly cut off, effectively preventing energy loss caused by accidental switching.

[0042] Optionally, refer to Figure 4 and Figure 5 In another embodiment of the present invention, a power supply circuit is provided, based on the above. Figure 4 In the embodiment shown, the power supply circuit includes a self-driven power supply circuit 60, wherein: The power input terminal of the self-driven power supply circuit 60 is connected to the output terminal of the DC / DC conversion circuit 20, and the power output terminal of the self-driven power supply circuit 60 is connected to the power input terminal of the switch drive circuit 42.

[0043] The self-driven power supply circuit 60 refers to the circuit that obtains electrical energy from the output of the DC / DC conversion circuit 20 and provides operating power to the switch drive circuit 42. It can be implemented using a capacitor energy storage structure or an auxiliary winding structure of the transformer 22. For example, when a capacitor energy storage structure is used, the AC component of the push-pull rectified output is stored in the capacitor to form DC power; when an auxiliary secondary winding is used, the transformer 22 is additionally equipped with a winding to directly induce and generate the voltage required for drive.

[0044] In this design, the self-powered power supply circuit 60 obtains energy from the output of the DC / DC converter circuit 20, and then processes it internally to form a stable voltage output to the switch drive circuit 42. For example, in a capacitor energy storage structure, the AC power output from the push-pull rectified circuit is filtered and stored through the first capacitor C3 to form a DC voltage usable by the switch drive circuit 42. In the auxiliary winding embodiment, the auxiliary winding added to the transformer 22 generates an AC voltage synchronized with the main circuit through electromagnetic induction, which is then rectified and filtered to power the drive circuit. This design allows the switch drive circuit 42 to achieve self-powering without an external independent power supply, directly utilizing the energy of the main circuit.

[0045] Compared to existing technologies, the existing switch drive circuit 42 requires an external power supply or relies on MCU power, which increases circuit complexity and introduces drive delay. This embodiment obtains energy directly from the main power circuit through a self-driven power supply structure, eliminating the need for external power supply lines and achieving real-time synchronization between the drive signal and the main circuit state, thus avoiding control lag caused by power supply path delays.

[0046] Through the above technical solution, this embodiment effectively solves the problems of control delay and circuit complexity caused by the reliance on external power supply for the drive circuit, and realizes autonomous drive energy supply and real-time matching with the main circuit state. Under light load conditions, the self-driven power supply circuit 60 can automatically reduce power output as the main circuit power decreases, avoiding no-load losses in the drive circuit, thereby improving light load efficiency and reducing overall energy consumption.

[0047] Optionally, refer to Figure 6 Another embodiment of the present invention provides a power supply circuit based on the above. Figure 4 and Figure 5 In the embodiment shown, the self-driven power supply circuit 60 includes a first capacitor C3, wherein: The first terminal is connected to the first output terminal of the DC / DC conversion circuit 20, and the second terminal of the first capacitor C3 is connected to the second output terminal of the DC / DC conversion circuit 20. Alternatively, the transformer 22 of the DC / DC conversion circuit 20 may include an auxiliary secondary winding, which is connected to the power input terminal of the switch drive circuit 42.

[0048] Among them, the self-powered power supply circuit 60 refers to the circuit that obtains electrical energy from the output terminal of the DC / DC conversion circuit 20 and provides working power to the switch drive circuit 42. It can be implemented by using a capacitor energy storage structure or the auxiliary winding of the transformer 22. Its function is to realize the autonomous power supply of the drive circuit without the need for an external independent power supply.

[0049] The self-driven power supply circuit 60 obtains power from the output of the DC / DC converter circuit 20, and its output voltage may fluctuate due to load changes. The initial voltage can be reduced to a stable value through voltage division or regulation by the buck circuit 70. For example, a three-terminal regulator can be used to convert the 24V input to a 5V output, and then this voltage is transmitted to the power input of the switch driver circuit 42. When the DC / DC converter circuit 20 is under light load, the output voltage of the self-driven power supply circuit 60 may drop to a critical value. At this time, the buck circuit 70 can still maintain the minimum operating voltage requirement of the switch driver circuit 42.

[0050] The self-driven circuit power supply section uses the voltage of the clamping capacitor (i.e., the first capacitor C3) to power the safety switch (i.e., switch branch 41) through a step-down voltage regulator circuit. Alternatively, an auxiliary winding can be added to the transformer 22 or the inductor for conversion, or an auxiliary winding can be added to the secondary winding for power conversion.

[0051] Existing solutions directly use a self-driven power supply voltage to drive the switching circuit 40. When the output voltage is too high, it can easily cause the drive circuit components to break down; when the output voltage is too low, it cannot maintain normal operation. This embodiment eliminates the risk of overvoltage and ensures stable power supply over a wide input voltage range by adding a step-down circuit 70. This embodiment achieves precise control of the power supply voltage of the switching drive circuit 42, solving the problem of drive failure or component damage caused by voltage fluctuations in traditional self-driven power supply solutions. It also avoids the increased cost of adding an independent power supply module, optimizing the circuit structure complexity while ensuring system reliability.

[0052] Optionally, refer to Figure 4 and Figure 7 Another embodiment of the present invention provides a power supply circuit based on the above. Figure 4 and Figure 5 In the embodiment shown, the power supply circuit further includes a step-down circuit 70, wherein: The input terminal of the step-down circuit 70 is connected to the output terminal of the self-driven power supply circuit 60, and the output terminal of the step-down circuit 70 is connected to the power input terminal of the switch drive circuit 42. The step-down circuit 70 is used to reduce the voltage output by the self-driven power supply circuit 60 and then output it to the switch drive circuit 42.

[0053] The step-down circuit 70 is a conversion circuit that reduces the input voltage. It can be implemented using a linear regulator, a DC-DC converter, or a voltage divider network. The step-down circuit 70 converts the higher voltage output from the self-driven power supply circuit 60 into a lower voltage suitable for the operation of the switch drive circuit 42, preventing damage to the drive circuit due to overvoltage. The self-driven power supply circuit 60 is a power supply unit that obtains energy from the output of the DC / DC converter circuit 20. It can be implemented using a capacitor energy storage circuit or an auxiliary winding circuit of the transformer 22. The self-driven power supply circuit 60 provides an independent power supply for the switch drive circuit 42. The switch drive circuit 42 is a drive unit that controls the conduction state of the switch branch 41. It can be implemented using a transistor combination circuit or an integrated circuit, and is used to control the on / off state of the switch branch 41 based on the current detection signal. The switch branch 41 includes a safety switch transistor Q0.

[0054] The self-powered power supply circuit 60, after obtaining energy from the output of the DC / DC converter circuit 20, may have an output voltage higher than the operating voltage range of the switching drive circuit 42. By employing a buck converter circuit 70, the voltage output by the self-powered power supply circuit 60 is reduced before being supplied to the switching drive circuit 42. For example, when the output voltage of the DC / DC converter circuit 20 is 24V, the buck converter circuit 70 can convert it to 5V to supply the driver chip. This design prevents the switching drive circuit 42 from being damaged due to excessively high input voltage and also reduces the power consumption of the drive circuit itself. When the DC / DC converter circuit 20 is under light load, the output voltage of the self-powered power supply circuit 60 may fluctuate with load changes; the buck converter circuit 70 maintains a stable power supply to the drive circuit through its voltage regulation function.

[0055] This embodiment introduces a step-down circuit 70, which ensures a stable operating voltage for the drive circuit under different load conditions while reducing the energy loss of the drive circuit itself. This embodiment achieves precise control of the supply voltage of the switch drive circuit 42, avoiding energy waste caused by excessively high supply voltage, while ensuring reliable operation of the drive circuit under light load conditions, thereby improving the overall efficiency of the power supply system.

[0056] Optionally, refer to Figure 8 and Figure 9 In another embodiment of the present invention, a power supply circuit is provided, based on the above... Figures 1 to 7 In any of the embodiments shown, the DC / DC conversion circuit 20 includes a first conversion circuit 21, a transformer 22, a second conversion circuit 23, and a filter circuit 24, wherein: The input terminal of the first conversion circuit 21 is connected to the first DC terminal 10, and the first conversion circuit 21 is used to convert the first DC voltage connected to the first DC terminal 10 into a first AC power supply; the primary winding of the transformer 22 is connected to the output terminal of the first conversion circuit 21; the first input terminal of the second conversion circuit 23 is connected to the first end of the secondary winding of the transformer 22, and the second input terminal of the second conversion circuit 23 is connected to the third end of the secondary winding of the transformer 22; the input terminal of the filter circuit 24 is connected to the output terminal of the second conversion circuit 23, and the output terminal of the filter circuit 24 is connected to the input terminal of the current detection circuit 30.

[0057] The filter circuit 24 includes a first inductor L1 and a second capacitor C1, wherein: The first end of the first inductor L1 is connected to the output end of the transformer circuit, and the second end of the first inductor L1 is connected to the first input end of the drive circuit; the first end of the second capacitor C1 is connected to the second end of the first inductor L1.

[0058] The first conversion circuit 21 refers to an inverter module that converts DC voltage to AC voltage. It can be implemented using a combination of switching transistors in a full-bridge or half-bridge topology, generating alternating current by controlling the alternating conduction of the switching transistors. The transformer 22 is an electromagnetic coupling device used for voltage conversion. It can employ a secondary winding structure with a center tap, and voltage rise / fall is achieved by adjusting the turns ratio of the primary and secondary windings. The second conversion circuit 23 is a synchronous rectification module, which can use a half-wave or full-wave rectifier circuit composed of field-effect transistors. Rectification is achieved by controlling the switching transistors to conduct at specific phases. The filter circuit 24 is an LC filter network composed of inductors and capacitors. It can employ a single-stage or multi-stage LC structure, using inductors to suppress current surges and capacitors to absorb voltage ripple, thus stabilizing the output current.

[0059] The first conversion circuit 21 is a primary-side bridge circuit, which can be either a full-bridge circuit or a half-bridge circuit. The second conversion circuit 23 can be a push-pull rectifier structure.

[0060] The first conversion circuit 21 converts the input DC voltage into high-frequency AC voltage, which is then regulated by transformer 22 before being transmitted to the secondary side. The synchronous rectifier in the second conversion circuit 23 alternates between the positive and negative half-cycles of the AC voltage according to the drive signal, rectifying the AC voltage output from the secondary winding into pulsating DC. The inductor and capacitor in the filter circuit 24 work together to smooth the pulsating DC, reducing the ripple coefficient of the output current. The inductor is connected in series between the rectified output terminal and the load to limit the rate of current change; the capacitor is connected in parallel between the output terminal and ground to absorb high-frequency noise and stabilize the output voltage. This structure, through physical filtering, can improve energy conversion efficiency under light load conditions while reducing drive losses.

[0061] This embodiment directly processes the rectified current signal through an independently configured filter circuit 24, utilizing the inherent characteristics of the LC network to achieve current smoothing without relying on external controller intervention. Furthermore, the drive signal for the synchronous rectifier in the second conversion circuit 23 can be directly generated by the self-driven power supply circuit 60, avoiding the false turn-on problem caused by signal transmission delay in traditional solutions, thus improving system response speed and reliability. This embodiment solves the problems of complex control and low efficiency under light loads in traditional synchronous rectifier circuits. The filter circuit 24 effectively suppresses output current fluctuations, reducing switching losses caused by sudden current changes; the generation of the synchronous rectifier's drive signal is directly related to current detection, automatically reducing the switching frequency under light load conditions and minimizing ineffective drive energy consumption. This structure simplifies control logic while improving overall system efficiency, making it particularly suitable for power supply applications with high requirements for dynamic response and energy efficiency.

[0062] Optionally, refer to Figures 9 to 11 In another embodiment of the present invention, a power supply circuit is provided, based on the above. Figure 8 and Figure 9 In the embodiment shown, the second conversion circuit 23 includes a first switch Q5, a second switch Q6, a third switch Q7, and a fourth switch Q8, wherein: The drain of the second switch Q6 is connected to the source of the first switch Q5, and the common node of the first switch Q5 and the second switch Q6 is connected to the first end of the secondary winding of the transformer 22; the drain of the third switch Q7 is connected to the drain of the first switch Q5; the drain of the fourth switch Q8 is connected to the source of the third switch Q7, the source of the fourth switch Q8 is connected to the source of the second switch Q6, and the common node of the third switch Q7 and the fourth switch Q8 is connected to the third end of the secondary winding of the transformer 22.

[0063] Reference Figure 10 As shown, the power supply circuit also includes a rectifier switch drive circuit 80, wherein: The controlled terminal of the rectifier switch drive circuit 80 is electrically connected to the switch drive circuit 42 of the switch circuit 40. The rectifier switch drive circuit 80 is used to control the synchronous switching state of the second switch Q6 and the fourth switch Q8.

[0064] Reference Figure 11 As shown, the rectifier switch drive circuit 80 includes a third transistor P3, a sixth resistor R6, a fourth transistor P4, a seventh resistor R7, and a second diode D2, wherein: The base of the third transistor P3 is connected to the output terminal of the switch drive circuit 42 of the switch circuit 40, and the emitter of the third transistor P3 is grounded; the second terminal of the sixth resistor R6 is connected to the collector of the third transistor P3; the base of the fourth transistor P4 is connected to the collector of the third transistor P3, the emitter of the fourth transistor P4 is grounded, and the collector of the fourth transistor P4 is connected to the controlled terminals of the third switch Q7 and the fourth switch Q8, respectively; a seventh resistor R8 is connected in series between the second terminal of the seventh resistor R7 and ground, and the common ground of the seventh resistor R7 and the seventh resistor R8 is connected to the collector of the fourth transistor P4; the anode of the second diode D2 is grounded, and the cathode of the second diode D2 is connected to the collector of the fourth transistor P4.

[0065] In this context, synchronous switching refers to the state where the third switch Q7 and the fourth switch Q8 maintain a state where one is on and the other is off. For example, if the third switch Q7 is on, the fourth switch Q8 must be off, achieving synchronous rectification. This can be achieved by connecting the controlled terminals of both switches in parallel to the same drive signal. The third transistor P3 and the fourth transistor P4 form a Darlington transistor structure to amplify the current drive capability of the drive signal; this can be implemented using an NPN transistor combination. The second diode D2 provides a reverse current discharge path when the switches are off; a fast recovery diode can be used to prevent voltage spikes. The sixth resistor R6 and the seventh resistor R7 form a voltage divider network to adjust the voltage amplitude of the drive signal; for example, a resistor combination with a resistance ratio of 1:2 can be used for level matching.

[0066] When the current detection circuit 30 detects that the output current of the DC / DC conversion circuit 20 exceeds the threshold, the control signal output by the switch drive circuit 42 is amplified by the third transistor P3, then amplified again by the fourth transistor P4, and finally output to the gates of the third switch Q7 and the fourth switch Q8. At this time, the sufficient drive current provided by the Darlington structure enables both switches to conduct simultaneously, and the AC current of the secondary winding of the transformer 22 forms a low-impedance path through the switches. When the current is below the threshold, the drive signal disappears, the second diode D2 provides a discharge circuit for the gate capacitance of the switches, and the voltage division effect of the sixth resistor R6 and the seventh resistor R7 ensures that the switches are quickly and completely turned off.

[0067] In some specific implementations, the third switch Q7 and the fourth switch Q8 can be N-channel MOSFET devices, and a temperature sensor can be placed at their source connection to monitor their operating status. The resistance value of the sixth resistor R6 can be set from 1kΩ to 10kΩ to limit the base current of the transistor. The resistance value of the seventh resistor R8 can be configured to be half the resistance value of the seventh resistor R7 to form a specific voltage division ratio.

[0068] Existing synchronous rectification schemes rely on the MCU to directly control the switching transistor, requiring additional I / O ports and incurring signal delays. This embodiment directly responds to the current detection signal through the rectifier switch driver circuit 80, utilizing a multi-stage transistor amplification structure to achieve rapid transmission of the drive signal, enabling real-time synchronization between the switching transistor's operation and the current state. The combined design of the voltage divider resistor network and the bleeder diode effectively avoids the voltage residue problem when the switching transistor is turned off, resulting in more accurate current response characteristics compared to traditional voltage-based control schemes.

[0069] This embodiment achieves autonomous current control of the synchronous rectifier switch, automatically switching its operating state based on the load current without MCU intervention. The Darlington drive circuit improves signal response speed, and the voltage divider network ensures reliable turn-off of the switch under light loads, thereby reducing drive losses. This design simplifies the control architecture while maintaining high efficiency, making it particularly suitable for power conversion scenarios requiring rapid dynamic response.

[0070] Please refer to Figures 1 to 11 As shown in the diagram and in conjunction with all the above embodiments, with the widespread application of DC-DC converters, synchronous rectification technology is becoming increasingly prevalent. When the current is relatively large or the efficiency requirement is high, it is desirable for the current to flow through the MOSFET rather than the diode, thereby reducing energy loss. The MOSFET's driving circuit is generally directly controlled by the MCU, which adds an I / O port to the MCU, and the control becomes more complex, the response speed is not fast enough, and there is a risk of accidental turn-on.

[0071] However, existing technologies have the following problems: 1. This will require the MCU to add an additional I / O port, and the control will be more complex. The response speed will not be fast enough, which may cause false activation. 2. Most current solutions are based on voltage control and cannot control the switch to turn off according to the current. In many cases, it is not desirable to turn on the synchronous rectifier tube at low current to consume drive losses and waste drive energy, which would prevent the efficiency of light load from being further improved. In this case, it is necessary to control the switch according to the current.

[0072] In order to achieve self-driven control based on the current magnitude, this invention proposes a new self-driven circuit to control the synchronous rectifier tube based on the current magnitude.

[0073] Taking a classic DC / DC converter circuit as an example, the ports require reverse current protection, so a safety switch transistor is added, such as... Figure 2 The schematic diagram of the DC / DC conversion circuit is shown.

[0074] Switches Q1, Q2, Q3, and Q4 form the primary-side bridge circuit, while Q5, Q6, Q7, and Q8 form the secondary-side rectifier circuit. Q5 and Q7 are clamping transistors, and Q6 and Q8 are synchronous rectifier transistors. T is an isolation transformer, L1 is a filter inductor, C1 is a filter capacitor, and C3 is a clamping capacitor. Q0 is a safety switch. The safety switch Q0, as well as the synchronous rectifier transistors Q6 and Q8, can all be controlled using self-driven circuits.

[0075] The self-driven power supply circuit 60 supplies power to the safety switch Q0 by passing the voltage of the clamping capacitor C3 through a step-down and voltage-regulating circuit. Alternatively, an auxiliary winding can be added to the transformer T or inductor L1 for conversion, or an auxiliary power source section can be used to convert electrical energy.

[0076] The main body of the switch drive circuit in the self-driven circuit consists of PNP transistor P1, NPN transistor P2, matching diode D1, matching resistor R4, and current limiting resistors R1, R2, R3, and R5. The voltage difference between the branch voltage of diode D1 and the base voltage of transistor P2 is used to control P2. When no current flows through resistor Cs, or when the current is very small, since the required turn-on voltage of the diode D1 branch is high (D1 voltage + R4 voltage - Cs resistor voltage), transistor P2 turns on first, the diode branch does not turn on, P1 turns on, the drive signal DRV is low voltage, the safety switch Q0 does not turn on, and the synchronous rectifier does not turn on. When a large current flows through resistor Cs, Cs generates a large voltage drop, which reduces the voltage of the diode D1 branch. Diode D1 conducts first, while transistor P2 does not conduct. Neither transistor P1 nor the drive signal DRV is high, so the safety switch Q0 conducts, and the synchronous rectifier also conducts. The voltage of branch D1 can be made greater than the base voltage of P2 by adjusting the resistance of R4, and the switching of the synchronous rectifier can be controlled at a certain current.

[0077] The solutions in the embodiments of the present invention can also be implemented in the following ways: 1. The primary-side bridge circuit can be either a full-bridge or a half-bridge device; 2. The secondary side can be a push-pull, half-bridge, or full-bridge rectifier structure; 3. The self-driven circuit power supply section uses the voltage of the clamping capacitor C3 through a step-down and voltage-regulating circuit to power the safety switch Q0. Alternatively, an auxiliary winding can be added to the transformer T or inductor L1 for conversion, or an auxiliary power source section can be used to convert electrical energy.

[0078] The present invention also proposes an electronic device, the electronic device comprising the components described above. Figures 1 to 11 The power supply circuit described in the illustrated embodiment.

[0079] The electronic device converts the input DC voltage into a high-frequency AC signal via a DC / DC converter circuit 20. This signal is then coupled through a transformer 22 and output from the secondary winding to the rectifier stage. A current detection circuit 30 continuously monitors the rectified output current signal. When the detected current exceeds a preset upper limit, a switching circuit 40 immediately turns on to ensure efficient energy transfer under high current conditions. When the current falls below a preset lower limit, the switching circuit 40 automatically cuts off the path to avoid drive losses under low current conditions. This control process is entirely autonomous and based on the current detection signal, requiring no external controller. The synchronous rectifier drive circuit and the switching drive circuit 42 form a linked control mechanism, ensuring real-time matching between switching actions and current conditions.

[0080] It is worth noting that since the electronic device of the present invention is based on the power supply circuit described above, the embodiments of the electronic device of the present invention include all the technical solutions of all the embodiments of the power supply circuit described above, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0081] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A power supply circuit, characterized in that, The power supply circuit includes: The first DC terminal is used to connect an externally input first DC voltage. The second DC terminal is used to output a second DC voltage. A DC / DC conversion circuit, wherein the input terminal of the DC / DC conversion circuit is connected to the first DC terminal, and the DC / DC conversion circuit is used to convert the first DC voltage into the second DC voltage; A current detection circuit is provided, wherein the input terminal of the current detection circuit is connected to the output terminal of the DC / DC conversion circuit, and the current detection circuit is used to detect the current output by the DC / DC conversion circuit and output a corresponding current detection signal. A switching circuit is connected in series between the current detection circuit and the second DC terminal, and the controlled terminal of the switching circuit is electrically connected to the output terminal of the current detection circuit. The switching circuit is configured to, based on the current detection signal, determine if the current output by the DC / DC conversion circuit is greater than a first preset current threshold, and then connect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal; the switching circuit is configured to, based on the current detection signal, determine if the current output by the DC / DC conversion circuit is less than a second preset current threshold, and then disconnect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal.

2. The power supply circuit as described in claim 1, characterized in that, The current detection circuit includes: A current sensing resistor, the first end of which is connected to the output terminal of the DC / DC conversion circuit, and the second end of which is connected to the second DC terminal.

3. The power supply circuit as described in claim 2, characterized in that, The switching circuit includes: A switch branch is connected in series between the current sensing resistor and the second DC terminal; A switch driving circuit is provided, wherein the controlled terminal of the switch driving circuit is connected to the first terminal of the current sensing resistor. The switch driving circuit is used to control the switch branch to conduct the path between the output terminal of the DC / DC conversion circuit and the second DC terminal when the voltage drop of the current sensing resistor is greater than a first preset voltage drop threshold; and to control the switch branch to disconnect the path between the output terminal of the DC / DC conversion circuit and the second DC terminal when the voltage drop of the current sensing resistor is less than a second preset voltage drop threshold. Specifically, when the voltage drop across the current sensing resistor is greater than a first preset voltage drop threshold, the current detection circuit detects that the current output by the DC / DC conversion circuit is greater than a first preset current threshold; when the voltage drop across the current sensing resistor is less than a second preset voltage drop threshold, the current detection circuit detects that the current output by the DC / DC conversion circuit is less than a second preset current threshold.

4. The power supply circuit as described in claim 3, characterized in that, The switch driving circuit includes: A first diode, wherein a first resistor is connected in series between the cathode of the first diode and the second terminal of the current sensing resistor; The second resistor has a first end connected to the first power supply terminal and a second end connected to the positive terminal of the first diode. The first transistor has a third resistor connected in series between its base and the anode of the first diode, and its emitter is connected to the first terminal of the current sensing resistor. The fourth resistor has a first end connected to the first power supply terminal and a second end connected to the collector of the first transistor. The base of the second transistor is connected to the collector of the first transistor, the collector of the second transistor is connected to the first terminal of the current sensing resistor, and the emitter of the second transistor is connected to the controlled terminal of the switching circuit. The fifth resistor has its first end connected to the emitter of the second transistor, and its second end connected to the first power supply terminal.

5. The power supply circuit as described in claim 4, characterized in that, The power supply circuit includes: The self-driven power supply circuit has its power input terminal connected to the output terminal of the DC / DC conversion circuit, and its power output terminal connected to the power input terminal of the switch drive circuit.

6. The power supply circuit as described in claim 5, characterized in that, The self-driven power supply circuit includes: The first capacitor has its first terminal connected to the first output terminal of the DC / DC conversion circuit, and its second terminal connected to the second output terminal of the DC / DC conversion circuit. or, The transformer of the DC / DC conversion circuit includes an auxiliary secondary winding, which is connected to the power input terminal of the switch drive circuit.

7. The power supply circuit as described in claim 5, characterized in that, The power supply circuit also includes: A step-down circuit is provided, wherein the input terminal of the step-down circuit is connected to the output terminal of the self-driven power supply circuit, and the output terminal of the step-down circuit is connected to the power input terminal of the switch drive circuit. The step-down circuit is used to reduce the voltage output by the self-driven power supply circuit and then output it to the switch drive circuit.

8. The power supply circuit according to any one of claims 1 to 7, characterized in that, The DC / DC conversion circuit includes: A first conversion circuit, wherein the input terminal of the first conversion circuit is connected to the first DC terminal, and the first conversion circuit is used to convert the first DC voltage connected to the first DC terminal into a first AC power supply. A transformer, wherein the primary winding of the transformer is connected to the output terminal of the first conversion circuit; The second conversion circuit has a first input terminal connected to the first terminal of the secondary winding of the transformer, and a second input terminal connected to the third terminal of the secondary winding of the transformer. A filter circuit, wherein the input terminal of the filter circuit is connected to the output terminal of the second conversion circuit, and the output terminal of the filter circuit is connected to the input terminal of the current detection circuit.

9. The power supply circuit as described in claim 8, characterized in that, The second conversion circuit includes: First switching transistor; The drain of the second switch is connected to the source of the first switch, and the common node of the first switch and the second switch is connected to the first end of the secondary winding of the transformer. The third switching transistor, the drain of which is connected to the drain of the first switching transistor; The fourth switch is connected to the source of the third switch, and the source of the fourth switch is connected to the source of the second switch. The common node of the third and fourth switches is connected to the third terminal of the secondary winding of the transformer. The power supply circuit also includes: A rectifier switch driving circuit is provided, wherein the controlled terminal of the rectifier switch driving circuit is electrically connected to the switch driving circuit of the switch circuit, and the rectifier switch driving circuit is used to control the synchronous switching state of the second switch and the fourth switch.

10. An electronic device, characterized in that, Includes the power supply circuit as described in any one of claims 1 to 9.

Images