Power supply circuit and power supply device

Abstract

The application discloses a power supply circuit and a power supply device. The power supply circuit comprises a transformer, a switching circuit, a resonance capacitor and an auxiliary power supply circuit; the auxiliary power supply circuit comprises a step-down circuit and a valley detection circuit, a first end of the step-down circuit is connected with a first end of the switching circuit, a second end of the step-down circuit is connected with a first end of the valley detection circuit, a second end of the valley detection circuit is grounded, and the second end of the step-down circuit is also used for connecting a second load; wherein the valley detection circuit is used for detecting a valley signal according to a voltage on the first end of the switching circuit, and the power supply circuit is configured to control the switching circuit to be turned on through the valley signal. The above setting does not need to additionally set multiple windings, can simplify the circuit structure, reduce the circuit occupied space, reduce the cost and facilitate the circuit layout. On the other hand, the auxiliary power supply circuit is provided with the valley detection circuit, can turn on the switching circuit when the voltage on the switching circuit reaches the valley through the valley detection circuit, and can reduce the turn-on loss.

Description

Technical Field

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

[0002] With the development of technology, the types of electronic devices are increasing, such as microwave ovens, induction cookers, power strips, and small appliances. Power supply circuits are widely used in these devices. Related technologies propose a power supply circuit, but the problems with this circuit include high cost, large space occupation, and difficult circuit layout. Utility Model Content

[0003] The main technical problem this application addresses is to provide a power supply circuit and power supply device that simplifies the circuit structure, reduces the space occupied by the power supply circuit, and facilitates the layout of the power supply circuit.

[0004] To address the aforementioned problems, this application provides a power supply circuit comprising a transformer, a switching circuit, a resonant capacitor, and an auxiliary power supply circuit. The transformer includes a primary winding and a secondary winding. The first end of the primary winding is connected to a power source, and the secondary winding is connected to an external first load. The second end of the primary winding is connected to the first end of the switching circuit, and the second end of the switching circuit is grounded. The first end of the resonant capacitor is connected to the first end of the primary winding, and the second end of the resonant capacitor is connected to the second end of the primary winding. The auxiliary power supply circuit includes a step-down circuit and a valley detection circuit. The first end of the step-down circuit is connected to the first end of the switching circuit, and the second end of the step-down circuit is connected to the first end of the valley detection circuit, which is grounded. The second end of the step-down circuit is also used to connect to a second external load. The valley detection circuit detects a valley signal based on the voltage at the first end of the switching circuit, and the power supply circuit is configured to control the switching circuit's conduction via the valley signal.

[0005] In one possible implementation, the valley detection circuit includes a valley detection diode, a first voltage divider circuit, a driving transistor, a first valley signal generating device, and a high-level input. The cathode of the valley detection diode is connected to the second terminal of the step-down circuit; the anode of the valley detection diode is connected to the first terminal of the first voltage divider circuit, and the second terminal of the first voltage divider circuit is grounded; the first terminal of the driving transistor is connected to the first terminal of the first voltage divider circuit, the control terminal of the driving transistor is connected to the second terminal of the first voltage divider circuit, the high-level input is connected to the first valley signal generating device, and the second terminal of the driving transistor is connected between the first valley signal generating device and the high-level input. The first valley signal generating device is configured to generate a valley signal when it receives a high-level signal.

[0006] In one possible implementation, the first voltage divider circuit includes a voltage divider resistor, the first end of which is connected to the anode of the valley detection diode, and the second end of which is grounded.

[0007] In one possible implementation, the valley detection circuit includes: a second voltage divider circuit, the first end of which is connected to the second end of the step-down circuit; a first voltage regulator circuit, the first end of which is connected to the second end of the second voltage divider circuit, and the second end of the first voltage regulator circuit is grounded; and a second valley signal generating device is connected between the first voltage regulator circuit and the second voltage divider circuit.

[0008] In one possible implementation, the auxiliary power supply circuit further includes a rectifier circuit, a filter circuit, and a second voltage regulator circuit. The first terminal of the rectifier circuit is connected to the second terminal of the step-down circuit. The second terminal of the rectifier circuit is connected to the first terminal of the filter circuit, and the second terminal of the filter circuit is grounded. The first terminal of the filter circuit is used to connect the second load externally. The second terminal of the rectifier circuit is connected to the first terminal of the second voltage regulator circuit, and the second terminal of the second voltage regulator circuit is grounded.

[0009] In one possible implementation, the step-down circuit includes a step-down capacitor, the first end of which is connected to the first end of the switching circuit, and the second end of which is connected to the first end of the valley detection circuit.

[0010] In one possible implementation, the rectifier circuit includes a rectifier diode, the anode of which is connected to a second terminal of the buck circuit, and the cathode of which is connected to a first terminal of the filter circuit.

[0011] In one possible implementation, the second voltage regulator circuit includes a Zener diode, the first end of which is connected to the second end of the rectifier circuit, and the second end of which is grounded.

[0012] In one possible implementation, the switching circuit includes a switching transistor, the output of which is connected to the second end of the primary winding and grounded. The switching transistor also includes a control terminal configured to conduct upon receiving the valley signal.

[0013] To address the aforementioned problems, this application also provides a power supply device, which includes the aforementioned power supply circuit.

[0014] The beneficial effects of this application are as follows: The auxiliary power supply circuit of the power supply circuit includes a step-down circuit, which is connected to the switching circuit. After the voltage is stepped down by the step-down circuit, power is supplied to the second load. The above configuration eliminates the need for multiple windings on the secondary side of the transformer, simplifying the circuit structure, reducing the space occupied by the circuit, lowering costs, and facilitating circuit layout. On the other hand, the auxiliary power supply circuit is equipped with a valley detection circuit, which can detect when the voltage on the switching circuit reaches the valley and turn on the switching circuit, thereby reducing the turn-on loss of the switching circuit. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural block diagram of one embodiment of the power supply circuit of this application;

[0017] Figure 2 This is a structural block diagram of an embodiment of the auxiliary power supply circuit of this application;

[0018] Figure 3 for Figure 1 A schematic diagram of the first embodiment of the power supply circuit;

[0019] Figure 4 for Figure 3 Waveform timing diagrams of the switching circuit voltage, valley detection circuit output voltage, and switching circuit control signal in the power supply circuit;

[0020] Figure 5 for Figure 1 A schematic diagram of the second embodiment of the power supply circuit.

[0021] Figure label:

[0022] 100. Power supply circuit; 10. Resonant capacitor; 20. Transformer; 21. Primary winding; 22. Secondary winding; 30. Switching circuit; 301. Switching transistor; 40. Auxiliary power supply circuit; 41. Valley detection circuit; 42. Step-down circuit; 424. Step-down capacitor; 43. Rectifier circuit; 431. Rectifier diode; 44. Filtering circuit; 45. Second voltage regulator circuit; 451. Zener diode; 200. Power supply; 300. First load; 400. Second load; 50. Bus capacitor; 411. Valley detection diode; 412. First voltage divider circuit; 4121. Voltage divider resistor; 413. Driver transistor; 414. First valley signal generator; 421. Second voltage divider circuit; 422. First voltage regulator circuit; 423. Second valley signal generator. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0024] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless otherwise clearly indicated above. “Multiple” generally includes at least two, but does not exclude the inclusion of at least one.

[0025] It should be understood that the term "and / or" used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Furthermore, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0026] It should be understood that the terms "comprising," "including," or any other variations used herein are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in every place in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] Existing power supply circuits suffer from technical problems such as high circuit cost, large circuit space occupation, and difficult circuit layout.

[0029] To address the technical problem, this application provides a power supply circuit and a power supply device. The power supply circuit includes a switching circuit and an auxiliary power supply circuit. The auxiliary power supply circuit includes a step-down circuit connected to the switching circuit. The auxiliary power supply circuit supplies power to a second load after the voltage is stepped down by the step-down circuit. This simplifies the circuit structure, reduces the space occupied by the power supply circuit, and facilitates the layout of the power supply circuit.

[0030] For ease of explanation, please refer to the following examples. Figure 1 , Figure 2 and Figure 3 , Figure 1 This is a structural block diagram of one embodiment of the power supply circuit of this application; Figure 2 This is a structural block diagram of an embodiment of the auxiliary power supply circuit of this application; Figure 3 for Figure 1 A schematic diagram of the first embodiment of the power supply circuit.

[0031] In one specific embodiment, the power supply circuit 100 includes a transformer 20, a switching circuit 30, a resonant capacitor 10, and an auxiliary power supply circuit 40. The transformer 20 includes a primary winding 21 and a secondary winding 22. The first end of the primary winding 21 is connected to a power source 200, and the secondary winding 22 is used to connect an external first load 300. The second end of the primary winding 21 is connected to the first end of the switching circuit 30, and the second end of the switching circuit 30 is grounded. The first end of the resonant capacitor 10 is connected to the first end of the primary winding 21, and the second end of the resonant capacitor 10 is connected to the second end of the primary winding 21. The auxiliary power supply circuit 40 includes a step-down circuit 42 and a valley detection circuit 41. The first end of the step-down circuit 42 is connected to the first end of the switching circuit 30, and the second end of the step-down circuit 42 is connected to the first end of the valley detection circuit 41, which is grounded. The second end of the step-down circuit 42 is also used to connect an external second load 400. The valley detection circuit 41 is used to detect the valley signal based on the voltage at the first terminal of the switching circuit 30, and the power supply circuit 100 is configured to control the switching circuit 30 to conduct through the valley signal.

[0032] The primary winding 21 of transformer 20 is used for external power supply 200 input. Power supply 200 can specifically be high-voltage AC mains power, a battery device, a generator, etc. The input current is transmitted through electromagnetic induction coupling in transformer 20 to the secondary winding 22, supplying power to the first load 300. The first load 300 can specifically be an induction cooker, microwave oven, etc. As described above, transformer 20 serves the functions of voltage transformation and electromagnetic isolation. In related technologies, the power supply circuit usually also needs to have an auxiliary power supply circuit to supply power to the controller chip, indicator lights, display screen, etc. In related technologies, the auxiliary power supply circuit is implemented by adding an auxiliary winding on the secondary side of the transformer, using the auxiliary winding to reduce voltage and supply power to the load. The disadvantages of the above-mentioned related technologies are: the need to add an extra auxiliary winding for voltage reduction to supply power to the load, increasing circuit cost, occupying more circuit space, and making circuit layout difficult. In some embodiments of this application, the auxiliary power supply circuit 40 includes a step-down circuit 42, which is connected to the switching circuit 30. The step-down circuit 42 reduces the voltage and supplies power to the second load 400, such as the controller chip, indicator lights, and display screen, eliminating the need for an additional auxiliary winding, thus reducing costs and simplifying the circuit. Additionally, the first end of the resonant capacitor 10 is connected to the first end of the primary winding 21, and the second end of the resonant capacitor 10 is connected to the second end of the primary winding 21. The resonant capacitor 10 and the primary winding 21 form an LC parallel resonant circuit (inductor and capacitor parallel resonant circuit). The switching circuit 30 is connected to one end of the LC parallel resonant circuit. By switching the switching circuit 30 on and off, the resonant capacitor 10 and the inductive characteristics of the primary winding 21 resonate, generating an approximately sinusoidal alternating current in the circuit. This alternating current is then transmitted to the secondary winding 22 via electromagnetic induction coupling through the transformer 20 to supply power to the first load 300. In this embodiment, the switching circuit 30 specifically uses an NMOS transistor to achieve the switching function of turning on and off. In some other embodiments, the switching circuit 30 can also achieve the same function using other switching devices such as transistors. Furthermore, by switching on and off, the switching circuit 30 generates an approximately sinusoidal alternating current in the circuit. When the switching circuit 30 is on, it incurs turn-on losses. According to the power formula: P = U*I, when the switching circuit 30 is turned on at the voltage trough of the alternating current, the voltage across the switching circuit 30 is close to zero, which significantly reduces the turn-on losses when the switching circuit 30 is turned on, achieving a smaller turn-on loss. In order to detect when the voltage reaches the valley on the switching circuit 30, in this embodiment, the auxiliary power supply circuit 40 also includes a valley detection circuit 41. The valley detection circuit 41 can detect the change in voltage at the first terminal of the switching circuit 30, and detect the valley signal when the voltage at the first terminal of the switching circuit 30 reaches the valley. When the valley detection circuit 41 detects the valley signal, the power supply circuit 100 controls the switching circuit 30 to be turned on, which can reduce the turn-on loss of the switching circuit 30.

[0033] Unlike existing technologies, this application provides a power supply circuit 100, whose auxiliary power supply circuit 40 includes a step-down circuit 42 connected to a switching circuit 30. The voltage is stepped down by the step-down circuit 42 before supplying power to the second load 400. This configuration eliminates the need for multiple windings on the secondary side of the transformer 20, simplifying the circuit structure, reducing space requirements, lowering costs, and facilitating circuit layout. Furthermore, the auxiliary power supply circuit 40 includes a valley detection circuit 41, which detects when the voltage on the switching circuit 30 reaches a valley level and then activates the switching circuit 30, reducing the turn-on losses of the switching circuit 30.

[0034] In some embodiments, the power supply circuit 100 further includes a bus capacitor 50, the first end of which is connected to the first end of the primary winding 21, and the second end of which is grounded.

[0035] The primary winding 21 is connected to the power supply 200 input via the bus capacitor 50, which functions to stabilize voltage, filter, and buffer energy. Additionally, in this embodiment, the first terminal of the switching circuit 30 is also connected to the first terminal of the bus capacitor 50 via the primary winding 21. Therefore, when the switching circuit 30 is turned off, the bus capacitor 50 can clamp the switching circuit 30, enabling soft turn-off. Furthermore, in some embodiments, the pre-amplifier module of the bus capacitor 50 also includes a rectifier module (not shown), which can specifically be a diode rectifier bridge, a thyristor rectifier circuit 43, etc.

[0036] In one specific embodiment, the valley detection circuit 41 includes a valley detection diode 411, a first voltage divider circuit 412, a driving transistor 413, a first valley signal generating device 414, and a high-level input (not shown). The cathode (not shown) of the valley detection diode 411 is connected to the second terminal of the step-down circuit 42; the anode (not shown) of the valley detection diode 411 is connected to the first terminal of the first voltage divider circuit 412, and the second terminal of the first voltage divider circuit 412 is grounded; the first terminal of the driving transistor 413 is connected to the first terminal of the first voltage divider circuit 412, the control terminal (not shown) of the driving transistor 413 is connected to the second terminal of the first voltage divider circuit 412, the high-level input is connected to the first valley signal generating device 414, and the second terminal of the driving transistor 413 is connected between the first valley signal generating device 414 and the high-level input. The first valley signal generating device 414 is configured to generate a valley signal when it receives a high level.

[0037] In this embodiment, the step-down circuit 42 includes a step-down capacitor 424, and the driving transistor 413 is specifically an NPN transistor. The first terminal of the driving transistor 413 is the emitter of the NPN transistor, the second terminal of the driving transistor 413 is the collector of the NPN transistor, and the control terminal of the driving transistor is the base of the NPN transistor. The principle of detecting when the voltage on the switching circuit 30 reaches the valley is as follows: When the voltage on the first terminal of the switching circuit 30 begins to drop, the step-down capacitor 424 discharges, causing current to be generated in the first voltage divider circuit 412. Since the base of the driving transistor 413 is connected to the second terminal of the first voltage divider circuit 412, a voltage drop is formed when current is generated in the first voltage divider circuit 412, making the voltage on the base of the driving transistor 413 greater than the voltage on the emitter of the driving transistor 413. This causes the emitter junction of the driving transistor 413 to be forward biased, thereby driving the transistor 413 to conduct. When the driving transistor 413 is conducting, a short circuit is formed, so that the first valley signal generating device 414 does not receive a high level, and therefore does not generate a valley signal. When the voltage at the first terminal of the switching circuit 30 stops decreasing, i.e., when the voltage valley is reached, the step-down capacitor 424 stops discharging, causing the first voltage divider circuit 412 to stop generating current. Since there is no voltage drop across the first voltage divider circuit 412, the emitter voltage of the driving transistor 413 is greater than its base voltage, thereby reversing the emitter junction of the driving transistor 413. The emitter junction is cut off, and the driving transistor 413 is turned off. When the driving transistor 413 is turned off, the high-level input will send a high-level signal to the first valley signal generating device 414, enabling the first valley signal generating device 414 to generate a valley signal. Furthermore, in this embodiment, the high-level input is 5V; in other embodiments, the high-level input can also be 4V, 6V, etc. In addition, in this embodiment, the first valley signal generating device 414 is a microcontroller, which is also connected to the control terminal of the switching circuit 30. The valley signal generated by the microcontroller is sent to the control terminal of the switching circuit 30. When the control terminal of the switching circuit 30 receives the valley signal, it turns on, thereby realizing the valley conduction of the switching circuit 30 and reducing the turn-on loss. In other embodiments, the first valley signal generating device 414 can also be a programmable logic controller, a microprocessor, etc.

[0038] In some embodiments, the first voltage divider circuit 412 includes a voltage divider resistor 4121, the first end of which is connected to the anode of the valley detection diode 411, and the second end of which is grounded.

[0039] The voltage divider resistor 4121 acts as a voltage drop resistor. When current flows through the voltage divider resistor 4121, the potentials across it are different, causing the emitter voltage of the driving transistor 413 to be lower than its base voltage, thus turning on the driving transistor 413. In some preferred embodiments, the valley detection circuit 41 may also include a current limiting protection circuit (not shown). The first terminal of the current limiting protection circuit is connected to the emitter of the driving transistor 413, and the second terminal is connected between the valley detection diode 411 and the first voltage divider circuit 412. The current limiting protection circuit can provide voltage reduction protection and current limiting. Specifically, the current limiting protection circuit may include a resistor.

[0040] In a specific application scenario, please refer to the following: Figure 4 , Figure 4 for Figure 3 The figure shows the timing diagrams of the switching circuit voltage, valley detection circuit output voltage, and switching circuit control signal in the power supply circuit. As shown, a represents the timing change of the voltage waveform of switching circuit 30, b represents the timing change of the output waveform of valley detection circuit 41, and c represents the timing change of the control signal waveform of switching circuit 30. When the voltage of switching circuit 30 drops to the valley, valley detection circuit 41 outputs a high-level valley detection signal. This valley detection signal acts on switching circuit 30, turning it on, thus achieving valley-level conduction of switching circuit 30 and reducing turn-on losses.

[0041] Please refer to the following: Figure 5 , Figure 5 for Figure 1 A schematic diagram of the second embodiment of the power supply circuit. Figure 5 The diagram illustrates another embodiment of a valley detection circuit 41 to achieve the function of valley detection. In this embodiment, the valley detection circuit 41 includes a second voltage divider circuit 421, a first voltage regulator circuit 422, and a second valley signal generating device 423. The first terminal of the second voltage divider circuit 421 is connected to the second terminal of the step-down circuit 42; the first terminal of the first voltage regulator circuit 422 is connected to the second terminal of the second voltage divider circuit 421, and the second terminal of the first voltage regulator circuit 422 is grounded; the second valley signal generating device 423 is connected between the first voltage regulator circuit 422 and the second voltage divider circuit 421.

[0042] In this embodiment, the step-down circuit 42 includes a step-down capacitor 424, and the first voltage regulator circuit 422 is a Zener diode. When the valley power supply circuit 100 is working, the voltage at the first terminal of the switching circuit 30 is approximately sinusoidal. When the voltage at the first terminal of the switching circuit 30 begins to decrease, the step-down capacitor 424 discharges, and current is generated in the second voltage divider circuit 421. The second valley signal generating device 423 is configured such that no valley signal is generated when current flows through the second voltage divider circuit 421 and the first voltage regulator circuit 422. When the voltage at the first terminal of the switching circuit 30 stops decreasing, that is, when the voltage valley is reached in the switching circuit 30, the step-down capacitor 424 stops discharging, current is stopped being generated in the second voltage divider circuit 421, and the second fixed signal generating device is configured such that a valley signal is generated when current flows through the second voltage divider circuit 421 and the first voltage regulator circuit 422. The second valley signal generating device 423 can be a microcontroller, a programmable logic controller, a microprocessor, etc. In some embodiments, the second voltage divider circuit 421 may include a resistor.

[0043] In some embodiments, the auxiliary power supply circuit 40 further includes a rectifier circuit 43, the first terminal of which is connected to the second terminal of the step-down circuit 42. In some embodiments, the auxiliary power supply circuit 40 further includes a filter circuit 44, the second terminal of which is connected to the first terminal of the filter circuit 44, the second terminal of which is grounded, and the first terminal of which is used to connect an external second load 400. In some embodiments, the auxiliary power supply circuit 40 includes a second voltage regulator circuit 45, the second terminal of which is connected to the first terminal of the second voltage regulator circuit 45, and the second terminal of which is grounded.

[0044] The rectifier circuit 43 is used to convert the sinusoidal alternating current (AC) voltage reduced by the step-down circuit 42 into direct current (DC). In some embodiments, the rectifier circuit 43 may include a rectifier diode 431, with the anode of the rectifier diode 431 connected to the second terminal of the step-down circuit 42 and the cathode of the rectifier diode 431 connected to the first terminal of the filter circuit 44. The rectifier diode 431 enables the conversion of AC to DC. In other embodiments, the rectifier circuit 43 can be composed of a diode bridge or a diode combined with a capacitor for filtering to achieve the rectification function. For example, the rectifier circuit 43 can be rectified by forming a bridge with four diodes. In still other embodiments, the rectifier circuit 43 may be a half-wave rectifier circuit 43 or a full-wave rectifier circuit 43, etc.

[0045] The second load 400 is connected to the first terminal of the filter circuit 44. The filter circuit 44 is used to reduce the AC ripple in the DC power obtained after rectification by the rectifier circuit 43, and can protect the second load 400. In some embodiments, the filter circuit 44 includes a filter capacitor (not shown), one end of which is connected to the second terminal of the rectifier circuit 43, and the other end of which is grounded. In other embodiments, the filter circuit 44 can also be an inductor-capacitor π-type filter circuit 44. In still some embodiments, the filter circuit 44 can also use a multilayer ceramic capacitor in conjunction with a common-mode choke to achieve the filtering function.

[0046] The second voltage regulator circuit 45 is used to stabilize the DC voltage filtered by the filter circuit 44 into the precise voltage value required by the second load 400, reducing voltage fluctuations. In this embodiment, the second voltage regulator circuit 45 includes a Zener diode 451, the first terminal of which is connected to the second terminal of the rectifier circuit 43, and the second terminal of the Zener diode 451 is grounded. In other embodiments, the second voltage regulator circuit 45 can also achieve the voltage regulation function by setting a linear regulator or a switching regulator.

[0047] In this embodiment, the step-down circuit 42 includes a step-down capacitor 424. The first terminal of the step-down capacitor 424 is connected to the first terminal of the switching circuit 30, and the second terminal of the step-down capacitor 424 is connected to the first terminal of the valley detection circuit 41. Specifically, the step-down capacitor 424 can be a high-voltage ceramic capacitor. In other embodiments, the step-down circuit 42 can also be a thyristor step-down circuit. The thyristor step-down circuit can include a thyristor and a trigger circuit. The thyristor is connected to the first terminal of the switching circuit 30, and the trigger circuit is connected to the thyristor. The trigger circuit can control the conduction angle of the thyristor to change the effective value of the output voltage of the thyristor step-down circuit.

[0048] In some embodiments, the switching circuit 30 includes a switching transistor 301, the output terminal of which is connected to the second end of the primary winding 21 and grounded. The switching transistor 301 also includes a control terminal (not shown), which is configured to turn on after receiving a valley signal.

[0049] The switching transistor 301 is a switching device whose on and off states are changed by voltage changes at its control terminal. In this embodiment, the control terminal of the switching transistor 301 is connected to the auxiliary power supply circuit 40. When the auxiliary power supply circuit 40 detects a valley signal, it sends the valley signal to the control terminal of the switching transistor 301. The valley signal is specifically a high-level signal. When the control terminal of the switching transistor 301 receives the high-level signal, it turns on, thereby reducing the turn-on loss of the switching transistor 301. In addition, in this embodiment, the switching transistor 301 is specifically an NMOS transistor. In some other embodiments, the switching transistor 301 can also be an NPN transistor, a PNP transistor, a bipolar transistor, etc.

[0050] Unlike existing technologies, this application provides a power supply circuit 100, whose auxiliary power supply circuit 40 includes a step-down circuit 42 connected to a switching circuit 30. The voltage is stepped down by the step-down circuit 42 before supplying power to the second load 400. This configuration eliminates the need for multiple windings on the secondary side of the transformer 20, simplifying the circuit structure, reducing space requirements, lowering costs, and facilitating circuit layout. Furthermore, the auxiliary power supply circuit 40 includes a valley detection circuit 41, which detects when the voltage on the switching circuit 30 reaches a valley level and then activates the switching circuit 30, reducing the turn-on losses of the switching circuit 30.

[0051] Correspondingly, this application also proposes a power supply device, which includes the power supply circuit 100 of any of the above embodiments.

[0052] Finally, in a specific application scenario, the existing power supply circuit 100 suffers from high circuit cost, large circuit space occupation, and difficult circuit layout. The power supply circuit 100 of this application includes a transformer 20, a switching circuit 30, a resonant capacitor 10, and an auxiliary power supply circuit 40. The transformer 20 includes a primary winding 21 and a secondary winding 22. The first end of the primary winding 21 is used to connect to the power supply 200, and the secondary winding 22 is used to connect to an external first load 300. The second end of the primary winding 21 is connected to the first end of the switching circuit 30, and the second end of the switching circuit 30 is grounded. The first end of the resonant capacitor 10 is connected to the first end of the primary winding 21, and the second end of the resonant capacitor 10 is connected to the second end of the primary winding 21. Two-terminal auxiliary power supply circuit 40 includes a step-down circuit 42 and a valley detection circuit 41. The first terminal of the step-down circuit 42 is connected to the first terminal of the switching circuit 30, and the second terminal of the step-down circuit 42 is connected to the first terminal of the valley detection circuit 41. The second terminal of the valley detection circuit 41 is grounded, and the second terminal of the step-down circuit 42 is also used to connect an external second load 400. The valley detection circuit 41 is used to detect the valley signal based on the voltage on the first terminal of the switching circuit 30. The power supply circuit 100 is configured to control the conduction of the switching circuit 30 through the valley signal. The valley detection circuit 41 includes a valley detection diode 411, a first voltage divider circuit 412, a driving transistor 413, a first valley signal generating device 414, and a high-level input. The cathode of the valley detection diode 411 is connected to the second terminal of the step-down circuit 42; the anode of the valley detection diode 411 is connected to the first terminal of the first voltage divider circuit 412, and the second terminal of the first voltage divider circuit 412 is grounded; the first terminal of the driving transistor 413 is connected to the first terminal of the first voltage divider circuit 412, the control terminal of the driving transistor 413 is connected to the second terminal of the first voltage divider circuit 412, the high-level input is connected to the first valley signal generating device 414, and the second terminal of the driving transistor 413 is connected between the first valley signal generating device 414 and the high-level input. The first valley signal generating device 414 is configured to generate a valley signal when it receives a high-level input. The first voltage divider circuit 412 includes a voltage divider resistor 4121, the first terminal of which is connected to the anode of the valley detection diode 411, and the second terminal of which is grounded. The auxiliary power supply circuit 40 also includes a rectifier circuit 43, a filter circuit 44, and a second voltage regulator circuit 45. The first end of the rectifier circuit 43 is connected to the second end of the step-down circuit 42; the second end of the rectifier circuit 43 is connected to the first end of the filter circuit 44, the second end of the filter circuit 44 is grounded, and the first end of the filter circuit 44 is used to connect an external second load 400; the second end of the rectifier circuit 43 is connected to the first end of the second voltage regulator circuit 45, and the second end of the second voltage regulator circuit 45 is grounded.

[0053] The above are merely embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A power supply circuit, characterized in that, The power supply circuit includes: A transformer, comprising a primary winding and a secondary winding, wherein a first end of the primary winding is used to connect to a power source, and the secondary winding is used to connect to an external first load; A switching circuit, wherein the second end of the primary winding is connected to the first end of the switching circuit, and the second end of the switching circuit is grounded; A resonant capacitor, wherein a first end of the resonant capacitor is connected to a first end of the primary winding, and a second end of the resonant capacitor is connected to a second end of the primary winding; An auxiliary power supply circuit includes a step-down circuit and a valley detection circuit. The first terminal of the step-down circuit is connected to the first terminal of the switching circuit, and the second terminal of the step-down circuit is connected to the first terminal of the valley detection circuit. The second terminal of the valley detection circuit is grounded, and the second terminal of the step-down circuit is also used to connect a second external load. The valley detection circuit is used to detect a valley signal based on the voltage at the first terminal of the switching circuit, and the power supply circuit is configured to control the switching circuit to conduct through the valley signal.

2. The power supply circuit according to claim 1, characterized in that, The valley detection circuit includes: Valley detection diode, wherein the cathode of the valley detection diode is connected to the second terminal of the step-down circuit; In the first voltage divider circuit, the anode of the valley detection diode is connected to the first terminal of the first voltage divider circuit, and the second terminal of the first voltage divider circuit is grounded. A driving transistor is provided, with its first terminal connected to the first terminal of the first voltage divider circuit, and its control terminal connected to the second terminal of the first voltage divider circuit. A first valley signal generating device is connected to a high-level input, and the second terminal of the driving transistor is connected between the first valley signal generating device and the high-level input. The first valley signal generating device is configured to generate a valley signal when it receives a high level.

3. The power supply circuit according to claim 2, characterized in that, The first voltage divider circuit includes a voltage divider resistor, the first end of which is connected to the anode of the valley detection diode, and the second end of which is grounded.

4. The power supply circuit according to claim 1, characterized in that, The valley detection circuit includes: A second voltage divider circuit, wherein the first terminal of the second voltage divider circuit is connected to the second terminal of the step-down circuit; A first voltage regulator circuit, wherein the first terminal of the first voltage regulator circuit is connected to the second terminal of the second voltage divider circuit, and the second terminal of the first voltage regulator circuit is grounded; The second valley signal generating device is connected between the first voltage regulator circuit and the second voltage divider circuit.

5. The power supply circuit according to claim 2 or 4, characterized in that, The auxiliary power supply circuit also includes: A rectifier circuit, wherein the first terminal of the rectifier circuit is connected to the second terminal of the step-down circuit; The filter circuit has a second terminal connected to the first terminal of the rectifier circuit, the second terminal of the filter circuit being grounded, and the first terminal of the filter circuit being used to connect the second load externally. The second voltage regulator circuit has a second terminal connected to the first terminal of the rectifier circuit, and the second terminal of the second voltage regulator circuit is grounded.

6. The power supply circuit according to claim 2 or 4, characterized in that, The step-down circuit includes: A step-down capacitor, the first end of which is connected to the first end of the switching circuit, and the second end of which is connected to the first end of the valley detection circuit.

7. The power supply circuit according to claim 5, characterized in that, The rectifier circuit includes: A rectifier diode, wherein the anode of the rectifier diode is connected to the second terminal of the step-down circuit, and the cathode of the rectifier diode is connected to the first terminal of the filter circuit.

8. The power supply circuit according to claim 5, characterized in that, The second voltage regulator circuit includes: A Zener diode, the first end of which is connected to the second end of the rectifier circuit, and the second end of which is grounded.

9. The power supply circuit according to claim 1, characterized in that, The switching circuit includes: The switching transistor has its output terminal connected to the second terminal of the primary winding and grounded. The switching transistor also includes a control terminal configured to conduct after receiving the valley signal.

10. A power supply device, characterized in that, The power supply device includes the power supply circuit according to any one of claims 1-9.

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