Constant current output power supply circuit

Abstract

The embodiment of the utility model provides a constant-current output power supply circuit. The constant-current output power supply circuit is characterized in that an output end of an input circuit is coupled to a first end through a rectification chip; the starting end of the power supply chip is coupled with the output end of the rectification chip; the driving end of the first element is coupled with the switching element; the over-current detection end is coupled with the second element; the third element is coupled to the second end; one end of a first resistor in the driving circuit is coupled with a driving end, and the other end of the first resistor is coupled with a first element and / or grounded; the anode of the first diode is coupled with the first element, and the cathode of the first diode is coupled with the other end of the first resistor; the input end of the output circuit is coupled to the secondary coil, and the output end of the output circuit is coupled to an external load. Through the power supply chip and the feedback circuit, the working state of the primary side coil can be automatically adjusted according to the voltage change of the output end, the output current is ensured to be constant, and therefore the requirements of various precise electronic devices for stable current are met.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power supply circuits, and in particular to a constant current output power supply circuit. Background Art

[0002] In the field of modern power electronics, with the popularization of portable electronic devices and the development of new energy technologies, the demand for efficient, stable and safe power conversion systems is growing. Especially for application scenarios that require precise constant current output, such as battery charging, LED lighting drive, etc., the power conversion technology in related technologies has gradually shown its limitations. The AC-DC converters in related technologies often adopt relatively simple control strategies and circuit architectures, which leads to poor stability of the output current when the load changes, making it difficult to meet the constant current requirements of precision equipment. Especially when it is necessary to convert AC power into a specific DC voltage (e.g., 20V to 24V) and maintain a constant current output of 1.5A, the existing technology often finds it difficult to maintain the consistency and accuracy of the output under various working conditions. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a constant current output power supply circuit to solve the problems in the related art.

[0004] A first aspect of the present disclosure provides a constant current output power supply circuit, comprising:

[0005] An input circuit, wherein an input end of the input circuit is connected to an alternating current;

[0006] A transformer, the transformer comprising a primary coil, an auxiliary coil and a secondary coil;

[0007] The primary coil includes a first end and a second end; the auxiliary coil includes a third end and a fourth end;

[0008] The output end of the input circuit is coupled to the first end through a rectifier chip;

[0009] A power chip, the power chip comprising a start-up terminal, a power supply terminal, an overcurrent detection terminal, an overvoltage detection terminal, a feedback terminal, a driving terminal and a ground terminal;

[0010] The start-up end is coupled to the output end of the rectifier chip through a start-up circuit; the power supply end is coupled to the third end through a power supply circuit; the overvoltage detection end is coupled to the third end through an overvoltage detection circuit; the feedback end is coupled to a feedback circuit; and the ground end is grounded;

[0011] The output end of the rectifier chip is connected in parallel with a first energy storage filter capacitor;

[0012] A switch element, the switch element comprises a first element, a second element and a third element; the driving end is coupled to the first element through a driving circuit; the overcurrent detection end is coupled to the second element through an overcurrent detection circuit; the third element is coupled to the second end;

[0013] The driving circuit comprises:

[0014] a first resistor, one end of the first resistor being coupled to the driving end via a second resistor, and the other end of the first resistor being coupled to the first element and / or being grounded via a third resistor;

[0015] a first diode, wherein an anode of the first diode is coupled to the first element, and a cathode of the first diode is coupled to the other end of the first resistor; the first element end is used to be applied with a signal to control the on-off between the second element end and the third element end;

[0016] an output circuit, wherein an input end of the output circuit is coupled to the secondary coil, and an output end of the output circuit is coupled to an external load;

[0017] One end of the feedback circuit is coupled to the secondary output end between the input end and the output end of the output circuit. The feedback circuit generates a feedback signal according to the output voltage of the output circuit to control the on and off of the primary coil, thereby controlling the output current and the output voltage.

[0018] In an embodiment of the first aspect, the startup circuit includes:

[0019] A fourth resistor, one end of the fourth resistor is coupled to the positive electrode of the first energy storage filter capacitor, and the other end of the fourth resistor is coupled to the start-up end.

[0020] In an embodiment of the first aspect, the power supply circuit includes:

[0021] a second diode, wherein an anode of the second diode is coupled to the third end via a fifth resistor, and a cathode of the second diode is coupled to the power supply end;

[0022] a second energy storage filter capacitor, wherein the positive electrode of the second energy storage filter capacitor is coupled to the negative electrode of the second diode, and the negative electrode of the second energy storage filter capacitor is coupled to the fourth end; and the fourth end is grounded;

[0023] A first capacitor is connected in parallel with the second energy storage filter capacitor.

[0024] In an embodiment of the first aspect, the overvoltage detection circuit includes:

[0025] a sixth resistor, one end of the sixth resistor being coupled to the third end, and the other end of the sixth resistor being coupled to the overvoltage detection end;

[0026] a seventh resistor, one end of the seventh resistor being coupled to the other end of the sixth resistor, and the other end of the seventh resistor being grounded;

[0027] A second capacitor, one end of the second capacitor is coupled to the other end of the seventh resistor, and the other end of the second capacitor is coupled to the overvoltage detection end.

[0028] In an embodiment of the first aspect, the overcurrent detection circuit includes:

[0029] A third capacitor, one end of the third capacitor is coupled to the overcurrent detection end, and the other end of the third capacitor is grounded;

[0030] an eighth resistor, one end of the eighth resistor being coupled to the overcurrent detection end, and the other end of the eighth resistor being grounded through a ninth resistor;

[0031] a tenth resistor, one end of the tenth resistor being coupled to the other end of the ninth resistor, and the other end of the tenth resistor being grounded;

[0032] An eleventh resistor is connected in parallel with the tenth resistor, one end of the eleventh resistor is coupled to the third element end, and the other end of the eleventh resistor is grounded.

[0033] In an embodiment of the first aspect, the feedback circuit comprises:

[0034] An optical coupling element, the optical coupling element comprising a transmitting end and a receiving end; one end of the receiving end is coupled to the feedback end through a twelfth resistor; a fourth capacitor is coupled between the two ends of the receiving end, and the other end of the receiving end is grounded;

[0035] One end of the transmitting end is coupled to the secondary output end through a thirteenth resistor;

[0036] A feedback chip, the feedback chip comprising a voltage positive feedback input terminal, a voltage negative feedback input terminal, a voltage feedback output terminal, a current positive feedback input terminal, a current negative feedback input terminal, a current feedback output terminal, a feedback chip power supply terminal and a feedback chip ground terminal;

[0037] The other end of the transmitting end is coupled to the voltage feedback output end and / or the current feedback output end, and the transmitting end adjusts the current value of the transmitting end according to the voltage feedback signal of the voltage feedback output end and the current feedback signal of the current feedback output end;

[0038] The voltage positive feedback input terminal is coupled to the feedback chip power supply terminal through a fourteenth resistor; the voltage negative feedback input terminal is coupled to a voltage feedback unit;

[0039] The current positive feedback input terminal is coupled to the feedback chip power supply terminal through the fifteenth resistor and the fourteenth resistor in sequence; the current negative feedback input terminal is grounded through a current feedback unit;

[0040] The feedback chip power supply end is coupled to the positive output end of the output circuit through a feedback chip power supply unit;

[0041] a third diode, wherein an anode of the third diode is coupled to the other end of the transmitting end, and a cathode of the third diode is coupled to the voltage feedback output end via a sixteenth resistor;

[0042] a fourth diode, wherein an anode of the fourth diode is coupled to one end of the transmitting end through a seventeenth resistor, and a cathode of the fourth diode is coupled to the current feedback output end through an eighteenth resistor;

[0043] The feedback chip ground terminal is grounded.

[0044] In an embodiment of the first aspect, the voltage feedback unit includes:

[0045] A nineteenth resistor, one end of the nineteenth resistor is coupled to the positive output terminal through a twentieth resistor, and the other end of the nineteenth resistor is coupled to the voltage negative feedback input terminal;

[0046] A twenty-first resistor, one end of the twenty-first resistor is coupled to the other end of the nineteenth resistor, and the other end of the twenty-first resistor is grounded.

[0047] In an embodiment of the first aspect, the current feedback unit includes:

[0048] A twenty-second resistor, one end of which is coupled to the current negative feedback input end through the negative output end of the output circuit, and the other end of which is grounded;

[0049] The external load is coupled between the positive output terminal and the negative output terminal;

[0050] A twenty-third resistor, the twenty-third resistor is connected in parallel with the twenty-second resistor.

[0051] In an embodiment of the first aspect, the feedback chip power supply unit includes:

[0052] A conversion chip, the conversion chip comprising a voltage input terminal, a voltage output terminal and a conversion chip ground terminal;

[0053] The voltage input terminal is coupled to the positive output terminal through a twenty-fourth resistor;

[0054] The voltage output terminal is coupled to the feedback chip power supply terminal;

[0055] A third energy storage filter capacitor, wherein a positive electrode of the third energy storage filter capacitor is coupled to the voltage output terminal, and a negative electrode of the third energy storage filter capacitor is grounded;

[0056] A fourth capacitor is connected in parallel with the third energy storage filter capacitor.

[0057] In an embodiment of the first aspect, the output end of the output circuit includes a positive output end and a negative output end; the secondary coil includes a fifth end and a sixth end

[0058] The output circuit comprises:

[0059] a fifth diode, wherein an anode of the fifth diode is coupled to the fifth terminal, and a cathode of the fifth diode is coupled to the positive output terminal via a first inductor;

[0060] a fourth energy storage filter capacitor, wherein a positive electrode of the fourth energy storage filter capacitor is coupled to one end of the first inductor, and a negative electrode of the fourth energy storage filter capacitor is grounded;

[0061] a fifth energy storage filter capacitor, wherein a positive electrode of the fifth energy storage filter capacitor is coupled to the other end of the first inductor, and a negative electrode of the fifth energy storage filter capacitor is grounded;

[0062] a fifth capacitor, the fifth capacitor being coupled between the positive output terminal and the negative output terminal;

[0063] a twenty-fourth resistor, one end of the twenty-fourth resistor being coupled to the anode of the fifth diode, and the other end of the twenty-fourth resistor being coupled to the cathode of the fifth diode via a sixth capacitor;

[0064] A twenty-fifth resistor, the twenty-fifth resistor is connected in parallel with the twenty-fourth resistor.

[0065] Beneficial effects of the present disclosure: The present disclosure can automatically adjust the working state of the primary coil according to the voltage change at the output end through the power chip and the feedback circuit, ensuring the constancy of the output current, thereby meeting the needs of various precision electronic equipment for stable current. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 A circuit schematic diagram showing a constant current output power supply circuit in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0067] The following is an explanation of the embodiments of the present disclosure by specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the information disclosed by the present disclosure. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in the present disclosure can also be modified or changed in various ways according to different viewpoints and application modules without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0068] The following is a detailed description of the embodiments of the present disclosure with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in many different forms and is not limited to the embodiments described herein.

[0069] In the representations of the present disclosure, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented may be combined in any one or a group of embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples represented in the present disclosure and the features of different embodiments or examples, unless they are mutually contradictory.

[0070] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the representation of the present disclosure, "a group" means two or more, unless otherwise clearly and specifically defined.

[0071] In order to clearly describe the present disclosure, components not related to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0072] Throughout the specification, when a device is said to be "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" by placing other elements therebetween. In addition, when a device is said to "include" a certain component, unless otherwise stated, it does not exclude other components, but means that other components may be included.

[0073] Although the terms first, second, etc. are used to represent various elements in this article in some examples, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first interface and the second interface, etc. are represented. Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising" and "including" indicate that there are the described features, steps, operations, elements, modules, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or a group of other features, steps, operations, elements, modules, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0074] The technical terms used herein are only used to refer to specific embodiments and are not intended to limit the present disclosure. The singular form used herein also includes the plural form unless the sentence clearly indicates the contrary meaning. The meaning of "including" used in the specification is to specify specific characteristics, regions, integers, steps, operations, elements and / or components, and does not exclude the existence or addition of other characteristics, regions, integers, steps, operations, elements and / or components.

[0075] Although not defined differently, all terms, including technical and scientific terms used herein, have the same meaning as those generally understood by those skilled in the art to which the present disclosure belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with relevant technical literature and the message of the present disclosure, and shall not be overly interpreted as ideal or very formal meanings unless defined.

[0076] In the related art, the AC-DC converters in the related art often adopt relatively simple control strategies and circuit architectures, which leads to poor stability of the output current when the load changes, and it is difficult to meet the constant current requirements of precision equipment. In particular, when it is necessary to convert AC power into a specific DC voltage (e.g., 20V to 24V) and maintain a constant current output of 1.5A, the existing technology often has difficulty in maintaining the consistency and accuracy of the output under various working conditions.

[0077] The first aspect of the present disclosure provides a constant current output power supply circuit, wherein Figure 1 In the embodiment, the constant current output power supply circuit includes: an input circuit, a transformer T1, a power supply chip, a switch element Q1 and an output circuit.

[0078] The input end of the input circuit is connected to alternating current.

[0079] The transformer T1 includes a primary coil, an auxiliary coil and a secondary coil.

[0080] The primary coil includes a first end 1 and a second end 2. The auxiliary coil includes a third end 3 and a fourth end 4.

[0081] The output end of the input circuit is coupled to the first end 1 through a rectifier chip.

[0082] exist Figure 1 In the embodiment, the power chip includes a startup terminal HV, a power supply terminal VDD, an overcurrent detection terminal CS, an overvoltage detection terminal DMG, a feedback terminal FB, a driving terminal GATE and a ground terminal GND1.

[0083] The start-up terminal HV is coupled to the output terminal of the rectifier chip through a start-up circuit. The power supply terminal VDD is coupled to the third terminal 3 through a power supply circuit. The overvoltage detection terminal DMG is coupled to the third terminal 3 through an overvoltage detection circuit. The feedback terminal FB is coupled to a feedback circuit. The ground terminal GND1 is grounded.

[0084] The output end of the rectifier chip is connected in parallel with a first energy storage filter capacitor EC1.

[0085] The switch element Q1 includes a first element terminal G, a second element terminal S and a third element terminal D. The driving terminal GATE is coupled to the first element terminal G through a driving circuit. The overcurrent detection terminal CS is coupled to the second element terminal S through an overcurrent detection circuit. The third element terminal D is coupled to the second terminal 2.

[0086] exist Figure 1 In the embodiment, the driving circuit includes: a first resistor R1, a second resistor R2, a third resistor R3 and a first diode D1.

[0087] One end of the first resistor R1 is coupled to the driving end GATE via the second resistor R2 , and the other end of the first resistor R1 is coupled to the first element end G and / or is grounded via the third resistor R3 .

[0088] The anode of the first diode D1 is coupled to the first element terminal G, and the cathode of the first diode D1 is coupled to the other end of the first resistor R1. The first element terminal G is used to be applied with a signal to control the on-off between the second element terminal S and the third element terminal D.

[0089] An input terminal of the output circuit is coupled to the secondary coil, and an output terminal of the output circuit is coupled to an external load.

[0090] One end of the feedback circuit is coupled to the secondary output end between the input end and the output end of the output circuit. The feedback circuit generates a feedback signal according to the output voltage of the output circuit to control the on and off of the primary coil, thereby controlling the output current and the output voltage.

[0091] Specifically, in some embodiments, the input end of the input circuit is connected to an AC power grid, and the AC power is rectified by a rectifier chip and output as DC power.

[0092] Optional, in Figure 1 In the embodiment, the input circuit includes: a live input terminal L, a neutral input terminal N, a first fuse F1, a second fuse F2, an adjustable resistor RV1, a common mode suppression inductor T2, a twelfth capacitor C12, a thirteenth capacitor C13, a thirty-third resistor R33 and a thirty-fourth resistor R34.

[0093] The live line input terminal L is coupled to one input terminal of the common mode suppression inductor T2 through the first fuse F1; the neutral line input terminal N is coupled to the other input terminal of the common mode suppression inductor T2 through the second fuse F2. The safety of the circuit is ensured when encountering an overcurrent condition, and the first fuse F1 and the second fuse F2 will be blown in time to cut off the power supply and avoid circuit damage.

[0094] One end of the adjustable resistor RV1 is coupled to the first fuse F1, and the other end of the adjustable resistor RV1 is coupled to the second fuse F2; the adjustable resistor RV1 is connected in parallel with the thirteenth capacitor C13. The adjustable resistor RV1 is arranged between the first fuse F1 and the second fuse F2, so that the input impedance of the circuit can be fine-tuned according to actual needs.

[0095] The common mode suppression inductor T2 is used to suppress common mode noise and improve the quality of power supply. The two ends of the common mode suppression inductor T2 are connected to the live wire and the neutral wire respectively, which can effectively block the common mode interference signal propagating along the power line.

[0096] One end of the thirty-third resistor R33 is coupled to one output end of the common-mode suppression inductor T2, and the other end of the thirty-third resistor R33 is coupled to the other output end of the common-mode suppression inductor T2 through the thirty-fourth resistor R34, forming a voltage divider circuit, which helps to adjust and stabilize the voltage level entering the subsequent rectification stage.

[0097] The twelfth capacitor C12 is connected in parallel with the thirty-third and thirty-fourth resistors R34 to form a low-pass filter to further filter out high-frequency noise.

[0098] The output end of the input circuit is coupled to the input end of the rectifier chip. The processed power is coupled to the input end of the rectifier chip through the output end of the input circuit. The rectifier chip is responsible for converting the pre-processed AC power into DC power. Because the output after direct rectification still has a voltage component that fluctuates with the AC input frequency. In order to obtain smoother DC power, a first energy storage filter capacitor EC1 is connected in parallel to the output end of the rectifier chip. The first energy storage filter capacitor EC1 is used to further reduce the ripple and obtain a more stable DC output.

[0099] Optionally, in some embodiments, the model of the rectifier chip is DB207S, or it can be implemented by rectifier chips from other manufacturers with similar principles.

[0100] Optionally, the transformer T1 includes a primary coil, an auxiliary coil and a secondary coil. The primary coil is used to receive the DC power from the rectification and control the energy transfer to the secondary coil through the switch element Q1. The auxiliary coil provides auxiliary power for the power chip. The second end 2 of the primary coil and the third end 3 of the auxiliary coil are the same end.

[0101] Optional, in Figure 1 In the embodiment, a thirteenth capacitor C13 is further coupled between the first end 1 of the primary coil and the ground end GND1 for filtering and noise suppression.

[0102] The power chip includes a startup terminal HV, a power supply terminal VDD, an overcurrent detection terminal CS, an overvoltage detection terminal DMG, a feedback terminal FB, a drive terminal GATE and a ground terminal GND1. The startup circuit of the power chip is composed of a small capacitor and a resistor to ensure that the chip can start reliably when powered on. The power supply circuit provides a stable power supply to the chip through the third terminal 3 of the auxiliary coil. The overvoltage detection circuit monitors the voltage of the auxiliary coil to prevent overvoltage from damaging the chip. The feedback terminal FB is connected to the feedback circuit for closed-loop control of the output voltage and current. The feedback terminal FB is used to sample the output voltage or current, and it sends the sampling information back to the comparator of the power chip. The feedback signal represents the actual output state of the power supply, which is compared with the preset reference value to determine whether the amplitude or frequency of the drive signal needs to be adjusted to maintain output stability.

[0103] In some embodiments, the power chip model may be PN8273 and related series chips with similar functions, or power chips from other manufacturers with similar principles.

[0104] The switch element Q1 can use NMOSFET as the high-frequency switch element Q1, the first element terminal G as the gate, the second element terminal S as the source of overcurrent detection, and the third element terminal D as the drain of the primary coil. The drive circuit includes a first resistor R1, a second resistor R2, a third resistor R3 and a first diode D1. The drive circuit is used to convert the drive signal output by the drive terminal GATE of the power chip into a drive current to drive the switch element Q1. When the switch element Q1 is turned on, the second end 2 of the primary coil passes through the second element terminal D, the third element terminal S, the ninth resistor R9, the tenth resistor R10 and the eleventh resistor in sequence. The intensity and timing of the drive signal affect the conduction and cutoff of the switch element Q1, thereby controlling the transmission and conversion efficiency of energy. The generation of the drive signal is usually regulated by the feedback signal output by the feedback terminal FB to achieve precise control of the drive current. In some embodiments, the switch element can also select a triode.

[0105] When the driving terminal GATE of the power chip outputs a high level, the high level signal first reaches one end of the first resistor R1 through the second resistor R2. The function of the second resistor R2 is to limit the current and protect the power chip from excessive transient current shocks. The voltage divider circuit formed by the first resistor R1 and the second resistor R2 adjusts the voltage reaching the first element terminal G (the gate of the switching element Q1). The third resistor R3 provides an additional path to help stabilize the gate voltage and provide a certain gate charge discharge path to facilitate rapid shutdown. The positive electrode of the first diode D1 is directly connected to the first element terminal G. When a high level signal arrives, the first diode D1 is not turned on (because the gate voltage is higher than the forward voltage of the diode), and does not affect the transmission of the drive signal. This design is mainly to provide a fast discharge channel when the gate voltage drops (that is, the switching element Q1 is turned off) to prevent the switch delay or mis-turning on caused by the slow drop in the gate voltage.

[0106] When the driving signal becomes low, the gate voltage is low. Due to the existence of parasitic capacitance between the gate and source, the parasitic capacitance begins to discharge, and the first diode D1 provides a low impedance path for the gate through the driving end GATE of the power chip to the ground end GND1, so that the gate charge can be quickly released, which accelerates the turn-off process of the switching element Q1, reduces the turn-off loss and shortens the turn-off time.

[0107] In some embodiments, the actual output voltage or current of the output circuit is sampled through the feedback circuit to obtain a feedback signal, which is fed back to the feedback terminal FB of the power chip. The power chip adjusts the on and off of the switching element Q1 according to the feedback signal to further adjust the switching frequency and duty cycle of the primary coil, thereby accurately controlling the output voltage and maintaining a constant current, and maintaining the consistency and accuracy of the output even when the load changes.

[0108] Optional, in Figure 1 In the embodiment, an RCD absorption circuit is further provided between the output end of the input circuit and the primary coil of the transformer T1, and the RCD absorption circuit includes: a sixth diode D6, an eleventh capacitor C11, a thirtieth resistor R30, a thirty-first resistor R31, a thirty-second resistor R32 and a thirty-fifth resistor R35.

[0109] The anode of the sixth diode D6 is coupled to the second end 2 of the primary coil, and the cathode of the sixth diode D6 is coupled to one end of the thirty-first resistor R31. The function of the sixth diode D6 is to allow current to flow in a specific direction. When a reverse voltage spike appears in the circuit, the sixth diode D6 is turned on to provide a low impedance path to protect circuit components from overvoltage damage.

[0110] The other end of the thirty-first resistor R31 is coupled to the first end 1 through the thirty-fifth resistor R35; the thirtieth resistor R30 is connected in parallel with the thirty-fifth resistor R35; the thirty-second resistor R32 is connected in parallel with the thirty-first resistor R31; the eleventh capacitor C11 is connected in parallel with the thirty-fifth resistor R35. The eleventh capacitor C11 is used to absorb high-frequency harmonics and reduce circuit noise, and at the same time, forms a filter network together with the thirty-fifth resistor R35, which helps to smooth voltage fluctuations in the circuit.

[0111] During the switching action, the induced voltage spike or current surge generated by the primary coil of the transformer T1 will be guided by the sixth diode D6 to the resistor-capacitor network, wherein the resistors (the 30th resistor R30, the 31st resistor R31, the 32nd resistor R32 and the 35th resistor R35) provide an energy dissipation path, and the 11th capacitor C11 is used to store and release energy. Under their combined effect, the overvoltage and overcurrent phenomena in the circuit are greatly reduced, thereby enhancing the stability and reliability of the entire power supply system.

[0112] Optionally, the startup circuit includes: a fourth resistor R4.

[0113] One end of the fourth resistor R4 is coupled to the positive electrode of the first energy storage filter capacitor EC1 , and the other end of the fourth resistor R4 is coupled to the start-up terminal HV.

[0114] Specifically, in some embodiments, the startup circuit includes: a fourth resistor R4.

[0115] One end of the fourth resistor R4 is connected to the positive electrode of the first energy storage filter capacitor EC1, and the other end is coupled to the startup terminal HV of the power chip. Since the power supply current required by the power chip is very low, the resistance value of the fourth resistor R4 is 10k, which prevents the power chip from being impacted by excessive current at startup, and provides a startup current for the power chip. It can also work together with the first energy storage filter capacitor EC1 to form an RC (resistance-capacitance) delay circuit, which is conducive to smoothing the startup process and ensuring that the startup of the power chip is more stable and reliable.

[0116] Optional, in Figure 1 In the embodiment, the power supply circuit includes: a second diode D2, a second energy storage filter capacitor EC2 and a first capacitor C1.

[0117] An anode of the second diode D2 is coupled to the third terminal 3 via a fifth resistor R5 , and a cathode of the second diode D2 is coupled to the power supply terminal VDD.

[0118] The positive electrode of the second energy storage filter capacitor EC2 is coupled to the negative electrode of the second diode D2, and the negative electrode of the second energy storage filter capacitor EC2 is coupled to the fourth terminal 4. The fourth terminal 4 is grounded.

[0119] The first capacitor C1 is connected in parallel with the second energy storage filter capacitor EC2.

[0120] Specifically, in some embodiments, the anode of the second diode D2 is connected to the third end 3 of the auxiliary coil of the transformer T1 through the fifth resistor R5. The current flows to the anode of the second diode D2 through the fifth resistor R5, and then provides the rectified current to the power supply terminal VDD. The fifth resistor R5 plays a role in current limiting and protection to prevent excessive instantaneous current from damaging the circuit. One end (positive electrode) of the second energy storage filter capacitor EC2 is coupled to the cathode of the second diode D2, that is, the output end of the rectified DC current, and the other end (negative electrode) is connected to the ground terminal GND1. The second energy storage filter capacitor EC2 is used to store electrical energy and release it when needed to smooth the output current, reduce ripple, and improve the purity of DC power. The first capacitor C1 is connected in parallel with the second energy storage filter capacitor EC2, which can more effectively filter out high-frequency noise and maintain the stability of the output voltage.

[0121] Optional, in Figure 1 In the embodiment, the overvoltage detection circuit includes: a sixth resistor R6, a seventh resistor R7 and a second capacitor C2.

[0122] One end of the sixth resistor R6 is coupled to the third end 3 , and the other end of the sixth resistor R6 is coupled to the overvoltage detection end DMG.

[0123] One end of the seventh resistor R7 is coupled to the other end of the sixth resistor R6 , and the other end of the seventh resistor R7 is grounded.

[0124] One end of the second capacitor C2 is coupled to the other end of the seventh resistor R7 , and the other end of the second capacitor C2 is coupled to the overvoltage detection end DMG.

[0125] Specifically, in some embodiments, the overvoltage detection circuit can promptly identify and respond to an abnormal increase in the output voltage of the auxiliary coil of the transformer T1, effectively protecting subsequent circuits from damage due to overvoltage.

[0126] The sixth resistor R6 is coupled between the third terminal 3 of the auxiliary coil and the overvoltage detection terminal DMG of the power chip, with one end coupled to the third terminal 3 and the other end connected to the overvoltage detection terminal DMG. The sixth resistor R6 is used to limit the current flowing into the overvoltage detection terminal DMG to prevent excessive transient voltage from directly impacting the power management chip and ensure chip safety.

[0127] One end of the seventh resistor R7 is connected to the other end of the sixth resistor R6 to form a voltage divider circuit, and the other end is grounded. The selection of the seventh resistor R7 needs to consider the resistance ratio with the sixth resistor R6 to set the threshold of overvoltage detection. One end of the second capacitor C2 is coupled to the ground terminal GND1 of the seventh resistor R7, and the other end is coupled to the overvoltage detection terminal DMG. The second capacitor C2 helps to filter out high-frequency noise and ensure the accuracy of the overvoltage detection signal.

[0128] Under normal working conditions, the voltage output by the auxiliary coil is applied to the overvoltage detection terminal DMG through the voltage divider circuit composed of the sixth resistor R6 and the seventh resistor R7. The second capacitor C2 plays the role of smoothing voltage fluctuations in this circuit to avoid false alarms caused by instantaneous voltage fluctuations. When the voltage of the auxiliary coil rises abnormally for some reason and exceeds the preset overvoltage threshold, the voltage of the overvoltage detection terminal DMG rises accordingly, triggering the overvoltage protection mechanism of the power chip, and quickly taking measures such as cutting off the power supply or adjusting the working state to protect the entire power system from damage.

[0129] Optional, in Figure 1 In the embodiment, the over-current detection circuit includes: a third capacitor C3, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10 and an eleventh resistor R11.

[0130] One end of the third capacitor C3 is coupled to the over-current detection terminal CS, and the other end of the third capacitor C3 is grounded.

[0131] One end of the eighth resistor R8 is coupled to the over-current detection terminal CS, and the other end of the eighth resistor R8 is grounded via a ninth resistor R9.

[0132] One end of the tenth resistor R10 is coupled to the other end of the ninth resistor R9 , and the other end of the tenth resistor R10 is grounded.

[0133] The eleventh resistor R11 is connected in parallel with the tenth resistor R10 , one end of the eleventh resistor R11 is coupled to the third element end D, and the other end of the eleventh resistor R11 is grounded.

[0134] Specifically, in some embodiments, the overcurrent detection circuit includes: a third capacitor C3, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and an eleventh resistor R11. One end of the third capacitor C3 is coupled to the overcurrent detection terminal CS of the power chip, and the other end is grounded. The main function of the third capacitor C3 is to filter out high-frequency noise, ensure the purity of the overcurrent signal, and avoid misjudgment caused by noise.

[0135] One end of the eighth resistor R8 is connected to the overcurrent detection terminal CS, and the other end is grounded through the ninth resistor R9 to form a voltage divider circuit. The resistance ratio of the eighth resistor R8 to the ninth resistor R9 determines the threshold of the overcurrent detection, that is, when the current passing through the eighth resistor R8 exceeds the preset value, the voltage of the overcurrent detection terminal CS will change significantly, triggering the protection mechanism. One end of the tenth resistor R10 is connected to the other end of the ninth resistor R9, and its function is to further adjust and stabilize the characteristics of the overcurrent detection circuit, and the other end is grounded. The eleventh resistor R11 is connected in parallel with the tenth resistor R10, one end of which is connected to the third element terminal D of the switching element Q1, and the other end is also grounded.

[0136] During normal operation, the third capacitor C3 keeps the voltage of the overcurrent detection terminal CS stable, while the voltage divider circuit composed of the eighth resistor R8 and the ninth resistor R9 monitors the current in the circuit. When the load is abnormal or an excessive current appears in the circuit, the current passing through the eighth resistor R8 increases, causing the voltage of the overcurrent detection terminal CS to change. This change is detected by the power chip, and then overcurrent protection measures are activated, such as limiting the current output or temporarily shutting down the power output, thereby protecting the components in the circuit from damage by overcurrent.

[0137] Optional, in Figure 1 In the embodiment, the feedback circuit includes: an optocoupler element, a feedback chip, a third diode D3 and a fourth diode D4.

[0138] The optical coupling element includes a transmitting terminal O2 and a receiving terminal O1. One end of the receiving terminal O1 is coupled to the feedback terminal FB via a twelfth resistor R12. A fourth capacitor C4 is coupled between two ends of the receiving terminal O1, and the other end of the receiving terminal O1 is grounded.

[0139] One end of the transmitting end O2 is coupled to the secondary output end through a thirteenth resistor R13.

[0140] The feedback chip includes a voltage positive feedback input terminal 1+, a voltage negative feedback input terminal 1-, a voltage feedback output terminal OP1, a current positive feedback input terminal 2+, a current negative feedback input terminal 2-, a current feedback output terminal OP2, a feedback chip power supply terminal VCC and a feedback chip ground terminal GND2.

[0141] The other end of the transmitting end O2 is coupled to the voltage feedback output end OP1 and / or the current feedback output end OP2. The transmitting end O2 adjusts the current value of the transmitting end O2 according to the voltage feedback signal of the voltage feedback output end OP1 and the current feedback signal of the current feedback output end OP2.

[0142] The voltage positive feedback input terminal 1+ is coupled to the feedback chip power supply terminal VCC through the fourteenth resistor R14. The voltage negative feedback input terminal 1- is coupled to a voltage feedback unit.

[0143] The current positive feedback input terminal 2+ is coupled to the feedback chip power supply terminal VCC through the fifteenth resistor R15 and the fourteenth resistor R14 in sequence. The current negative feedback input terminal 2- is grounded through a current feedback unit.

[0144] The feedback chip power supply terminal VCC is coupled to the positive output terminal VO+ of the output circuit through a feedback chip power supply unit.

[0145] An anode of the third diode D3 is coupled to the other end of the transmitting end O2 , and a cathode of the third diode D3 is coupled to the voltage feedback output end OP1 via a sixteenth resistor R16 .

[0146] An anode of the fourth diode D4 is coupled to one end of the emitter terminal O2 via a seventeenth resistor R17 , and a cathode of the fourth diode D4 is coupled to the current feedback output terminal OP2 via an eighteenth resistor R18 .

[0147] The feedback chip ground terminal GND2 is grounded.

[0148] Specifically, in some embodiments, one end of the transmitting terminal O2 of the optical coupling element is coupled to the secondary output terminal through the thirteenth resistor R13 to sense the changes in the actual output voltage and current. One end of the receiving terminal O1 is connected to the feedback terminal FB of the power chip through the twelfth resistor R12, and the fourth capacitor C4 is coupled between the two ends of the receiving terminal O1 to filter out high-frequency noise, and the other end is grounded to ensure the purity of the signal. A seventh capacitor C7 is also connected in parallel between the two ends of the receiving terminal O1, and one end of the seventh capacitor C7 is grounded.

[0149] The voltage positive feedback input terminal 1+ is connected to the feedback chip power supply terminal VCC through the fourteenth resistor R14, and the voltage negative feedback input terminal 1- is connected to the external voltage feedback unit. The current positive feedback input terminal 2+ is connected to the power supply terminal VDD through the fifteenth resistor R15 and the fourteenth resistor R14, and the current negative feedback input terminal 2- is grounded through the current feedback unit. The feedback chip power supply terminal VCC obtains power from the positive output terminal VO+ of the output circuit through the feedback chip power supply unit, and the ground terminal GND1 is directly grounded to ensure the normal operation of the chip.

[0150] The anode of the third diode D3 is connected to the other end of the optocoupler element emitter terminal O2, and the cathode is coupled to the voltage feedback output terminal OP1 through the sixteenth resistor R16, which is used to protect the feedback chip from overvoltage shock and assist in adjusting the voltage feedback signal. The anode of the fourth diode D4 is coupled to one end of the optocoupler element emitter terminal O2 through the seventeenth resistor R17, and the cathode is connected to the current feedback output terminal OP2 through the eighteenth resistor R18, which ensures the stable transmission and protection of the current feedback signal.

[0151] The feedback chip receives the current feedback signal and the voltage feedback signal of the output end of the output circuit through the voltage negative feedback input terminal 1- and the current negative feedback input terminal 2-. The voltage feedback signal reflects the state of the output voltage, while the current feedback signal conveys the information of the output current.

[0152] The received voltage and current feedback signals will be processed by the circuit inside the feedback chip. The chip may contain circuits such as an error amplifier and a comparator. The voltage feedback signal is compared with the voltage value of the voltage positive feedback input terminal 1+ and the current feedback signal is compared with the voltage value of the current positive feedback input terminal 2+, so as to determine whether the output needs to adjust the current of the optocoupler element. Based on the result after error amplification, the feedback chip will generate corresponding control signals. These control signals are output through the voltage feedback output terminal OP1 and the current feedback output terminal OP2, and are used to adjust the current value of the optocoupler element transmitting terminal O2. This adjustment is to indirectly control the duty cycle or switching frequency of the primary coil by changing the driving current of the transmitting terminal O2, thereby adjusting the output voltage and current.

[0153] Furthermore, when the feedback chip detects that the output voltage or current deviates from the set value, it changes the voltage of the voltage feedback output terminal OP1 or the current feedback output terminal OP2, thereby adjusting the current flowing through the thirteenth resistor R13 (connecting the emission terminal O2 and the secondary output terminal), and indirectly controlling the emission intensity of the optocoupler. The emission terminal O2 of the optocoupler element changes its luminous intensity according to the control signal generated by the feedback chip. A stronger control signal causes the optocoupler to emit more light, while a weaker signal reduces the emission of light. This change in light intensity reflects the feedback chip's instruction to adjust the output voltage or current.

[0154] In some embodiments, the feedback chip model may be AP4310A and related series chips with similar functions, or feedback chips from other manufacturers with similar principles.

[0155] Optional, in Figure 1 In the embodiment, the feedback circuit also includes a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, an eighth capacitor C8, a ninth capacitor C9 and a tenth capacitor C10. One end of the twenty-sixth resistor R26 is coupled to the voltage feedback output terminal OP1 for receiving a voltage feedback signal from the feedback chip, and the other end of the twenty-sixth resistor R26 is coupled to the voltage negative feedback input terminal 1- through the eighth capacitor C8. Filtering is performed through the twenty-sixth resistor R26 and the eighth capacitor C8. One end of the twenty-seventh resistor R27 is coupled to the current feedback output terminal OP2 for receiving a current feedback signal output by the feedback chip, and the other end of the twenty-seventh resistor R27 is coupled to the current negative feedback input terminal 2- through the ninth capacitor C9. The twenty-seventh resistor R27 and the ninth capacitor C9 also perform filtering.

[0156] The twenty-eighth resistor R28, the twenty-ninth resistor R29 and the thirtieth resistor R30 are connected in parallel, one end of the twenty-ninth resistor R29 is coupled to the fifteenth resistor R15, the other end of the twenty-ninth resistor R29 is grounded, one end of the tenth capacitor C10 is coupled to the current positive feedback input terminal 2+, the other end of the tenth capacitor C10 is grounded.

[0157] Optional, in Figure 1 In the embodiment, the voltage feedback unit includes: a nineteenth resistor R19, a twentieth resistor R20 and a twenty-first resistor R21.

[0158] One end of the nineteenth resistor R19 is coupled to the positive output terminal VO+ through the twentieth resistor R20, and the other end of the nineteenth resistor R19 is coupled to the voltage negative feedback input terminal 1-.

[0159] One end of the twenty-first resistor R21 is coupled to the other end of the nineteenth resistor R19 , and the other end of the twenty-first resistor R21 is grounded.

[0160] Specifically, in some embodiments, one end of the nineteenth resistor R19 is connected to the positive output terminal VO+ of the output circuit; the twentieth resistor R20 is connected in series with the nineteenth resistor R19, and its function is to form a voltage divider circuit, so that the output voltage can be proportionally reduced to a range suitable for the input level of the feedback chip, avoiding direct large voltage input from causing damage to the chip, and realizing preliminary voltage regulation. The other end of the nineteenth resistor R19 is connected to the voltage negative feedback input terminal 1- after passing through the twentieth resistor R20, and the voltage feedback signal is sent to the voltage feedback processing unit. The twenty-first resistor R21 is installed between the other end of the nineteenth resistor R19 and the ground, and its function is to provide a stable reference base (ground potential).

[0161] When the output voltage of the circuit changes, the change is proportionally reduced and converted into a voltage signal proportional to the output voltage through the voltage divider circuit composed of the nineteenth resistor R19 and the twentieth resistor R20. This signal is then sent to the voltage negative feedback input terminal 1-, and the feedback chip calculates the necessary correction amount based on the difference between this signal and the voltage positive feedback input terminal 1+, and then adjusts the output voltage of the circuit until the output is stable near the target value.

[0162] Optionally, the current feedback unit includes: a twenty-second resistor R22 and a twenty-third resistor R23.

[0163] One end of the 22nd resistor R22 is coupled to the current negative feedback input terminal 2- through the negative output terminal VO- of the output circuit, and the other end of the 22nd resistor R22 is grounded.

[0164] The external load is coupled between the positive output terminal VO+ and the negative output terminal VO-.

[0165] The twenty-third resistor R23 is connected in parallel with the twenty-second resistor R22.

[0166] Specifically, in the above embodiment, one end of the twenty-second resistor R22 is connected to the negative output terminal VO- of the output circuit, and the other end is grounded. It is used to sample the output current. The current flowing through the load can be indirectly measured by the voltage drop across the resistor, because the current flowing through the twenty-second resistor R22 is equal to the load current. The twenty-third resistor R23 is connected in parallel with the twenty-second resistor R22; the twenty-third resistor R23 can be used as a shunt resistor to help share part of the current, especially in high current applications, to reduce the heat load of a single resistor and improve system reliability. The external load is coupled between the positive output terminal VO+ and the negative output terminal VO- of the output circuit, which means that any change in the load will affect the current flowing through the twenty-second resistor R22 and the twenty-third resistor R23, thereby changing the voltage drop across the resistor. This change is sensed by the feedback chip through the current negative feedback input terminal 2-, and the feedback chip adjusts the output according to this signal to ensure the constant output current.

[0167] When the external load changes, causing the total current flowing through the twenty-second resistor R22 and the twenty-third resistor R23 to change, the voltage drop across the resistor changes accordingly. This changing voltage signal is fed back to the current negative feedback input terminal 2-, and the feedback chip adjusts its output control signal in real time according to this signal, such as adjusting the duty cycle or frequency of the switching element Q1, to maintain the output current constant and meet the system's requirements for current stability.

[0168] Optional, in Figure 1 In the embodiment, the feedback chip power supply unit includes: a conversion chip, a third energy storage filter capacitor EC3 and a fourth capacitor C4.

[0169] The conversion chip includes a voltage input terminal IN, a voltage output terminal OUT and a conversion chip ground terminal GND3.

[0170] The voltage input terminal IN is coupled to the positive output terminal VO+ through a twenty-fourth resistor R24.

[0171] The voltage output terminal OUT is coupled to the feedback chip power supply terminal VCC.

[0172] The positive electrode of the third energy storage filter capacitor EC3 is coupled to the voltage output terminal OUT, and the negative electrode of the third energy storage filter capacitor EC3 is grounded.

[0173] The fourth capacitor C4 is connected in parallel with the third energy storage filter capacitor EC3.

[0174] Specifically, in some embodiments, the feedback chip power supply unit includes: a conversion chip, a third energy storage filter capacitor EC3 and a fourth capacitor C4.

[0175] The conversion chip has a voltage input terminal IN, a voltage output terminal OUT and a conversion chip ground terminal GND3. The conversion chip extracts electrical energy from the power output terminal and converts it into a stable voltage suitable for the feedback chip to work. The voltage input terminal IN of the conversion chip is connected to the positive output terminal VO+ of the output circuit through the twenty-fourth resistor R24. The twenty-fourth resistor R24 ​​is used for current limiting to protect the conversion chip from transient current shocks, and can also filter out power supply ripple to a certain extent and improve the stability of the input voltage. The voltage output terminal OUT of the conversion chip is directly coupled to the power supply terminal VDD of the feedback chip to provide the feedback chip with the DC voltage required for work.

[0176] The positive electrode of the third energy storage filter capacitor EC3 is connected to the voltage output terminal OUT of the conversion chip, and the negative electrode is grounded. It can store and release electric energy, smooth the ripple in the output voltage, ensure the purity of the feedback chip power supply, and reduce noise interference. The fourth capacitor C4 is connected in parallel with the third energy storage filter capacitor EC3 to form a higher-level filter network. Thereby further reducing the power supply ripple, improving the ability to suppress high-frequency noise, ensuring that the voltage ripple of the feedback chip power supply is minimized when the dynamic load changes, and maintaining the accuracy of feedback control.

[0177] Optional, in Figure 1 In the embodiment, the output end of the output circuit includes a positive output end VO+ and a negative output end VO-. The secondary coil includes a fifth end 5 and a sixth end 6.

[0178] The output circuit includes: a fifth diode D5, a fourth energy storage filter capacitor EC4, a fifth energy storage filter capacitor EC5, a fifth capacitor C5, a twenty-fourth resistor R24 ​​and a twenty-fifth resistor R25.

[0179] An anode of the fifth diode D5 is coupled to the fifth terminal 5 , and a cathode of the fifth diode D5 is coupled to the positive output terminal VO+ via the first inductor L1 .

[0180] A positive electrode of the fourth energy storage filter capacitor EC4 is coupled to one end of the first inductor L1 , and a negative electrode of the fourth energy storage filter capacitor EC4 is grounded.

[0181] A positive electrode of the fifth energy storage filter capacitor EC5 is coupled to the other end of the first inductor L1 , and a negative electrode of the fifth energy storage filter capacitor EC5 is grounded.

[0182] The fifth capacitor C5 is coupled between the positive output terminal VO+ and the negative output terminal VO-.

[0183] One end of the twenty-fourth resistor R24 ​​is coupled to the anode of the fifth diode D5 , and the other end of the twenty-fourth resistor R24 ​​is coupled to the cathode of the fifth diode D5 via the sixth capacitor C6 .

[0184] The twenty-fifth resistor R25 is connected in parallel with the twenty-fourth resistor R24.

[0185] Specifically, in the above embodiment, the anode of the fifth diode D5 is directly coupled to the fifth terminal 5 of the secondary coil, and the cathode is coupled to the positive output terminal VO+ through the first inductor L1. The anode of the fourth energy storage filter capacitor EC4 is connected to one end of the first inductor L1, and the cathode is grounded, which is used to filter out high-frequency ripples; the anode of the fifth energy storage filter capacitor EC5 is coupled to the other end of the first inductor L1, and the cathode is also grounded, which further enhances the filtering effect and improves the quality of the output DC voltage.

[0186] A fifth capacitor C5 is coupled between the positive output terminal VO+ and the negative output terminal VO-, which helps stabilize the voltage at the output terminal, reduces transient voltage changes, and ensures that the load obtains a more stable DC power supply. In order to protect the fifth diode D5 and further smooth the output, one end of the twenty-fourth resistor R24 ​​is connected to the positive electrode of the fifth diode D5, and the other end is coupled to the negative electrode of the fifth diode D5 through the sixth capacitor C6 to form an RC filter, which helps to suppress rapidly changing current spikes and protect circuit components. At the same time, the twenty-fifth resistor R25 is connected in parallel with the twenty-fourth resistor R24, which can provide an additional current path to help share the load.

[0187] The above embodiments are merely illustrative of the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present disclosure shall still be covered by the protection scope of the present disclosure.

Claims

1. A constant current output power supply circuit, characterized in that: include: An input circuit, wherein an input end of the input circuit is connected to an alternating current; A transformer, the transformer comprising a primary coil, an auxiliary coil and a secondary coil; The primary coil includes a first end and a second end; the auxiliary coil includes a third end and a fourth end; The output end of the input circuit is coupled to the first end through a rectifier chip; A power chip, the power chip comprising a start-up terminal, a power supply terminal, an over-current detection terminal, an over-voltage detection terminal, a feedback terminal, a driving terminal and a ground terminal; The start-up end is coupled to the output end of the rectifier chip through a start-up circuit; the power supply end is coupled to the third end through a power supply circuit; the overvoltage detection end is coupled to the third end through an overvoltage detection circuit; The feedback terminal is coupled to a feedback circuit; the ground terminal is grounded; The output end of the rectifier chip is connected in parallel with a first energy storage filter capacitor; A switch element, the switch element comprising a first element, a second element and a third element; the driving end is coupled to the first element via a driving circuit; The over-current detection terminal is coupled to the second element via an over-current detection circuit; The third element is coupled to the second end; The driving circuit comprises: a first resistor, one end of the first resistor being coupled to the driving end via a second resistor, and the other end of the first resistor being coupled to the first element and / or being grounded via a third resistor; a first diode, wherein an anode of the first diode is coupled to the first element, and a cathode of the first diode is coupled to the other end of the first resistor; the first element end is used to be applied with a signal to control the on-off between the second element end and the third element end; an output circuit, wherein an input end of the output circuit is coupled to the secondary coil, and an output end of the output circuit is coupled to an external load; One end of the feedback circuit is coupled to the secondary output end between the input end and the output end of the output circuit. The feedback circuit generates a feedback signal according to the output voltage of the output circuit to control the on and off of the primary coil, thereby controlling the output current and the output voltage.

2. The constant current output power supply circuit according to claim 1, characterized in that: The startup circuit comprises: A fourth resistor, one end of the fourth resistor is coupled to the positive electrode of the first energy storage filter capacitor, and the other end of the fourth resistor is coupled to the start-up end.

3. The constant current output power supply circuit according to claim 1, characterized in that: The power supply circuit comprises: a second diode, wherein an anode of the second diode is coupled to the third end via a fifth resistor, and a cathode of the second diode is coupled to the power supply end; a second energy storage filter capacitor, wherein the positive electrode of the second energy storage filter capacitor is coupled to the negative electrode of the second diode, and the negative electrode of the second energy storage filter capacitor is coupled to the fourth end; and the fourth end is grounded; A first capacitor is connected in parallel with the second energy storage filter capacitor.

4. The constant current output power supply circuit according to claim 1, characterized in that: The overvoltage detection circuit comprises: a sixth resistor, one end of the sixth resistor being coupled to the third end, and the other end of the sixth resistor being coupled to the overvoltage detection end; a seventh resistor, one end of the seventh resistor being coupled to the other end of the sixth resistor, and the other end of the seventh resistor being grounded; A second capacitor, one end of the second capacitor is coupled to the other end of the seventh resistor, and the other end of the second capacitor is coupled to the overvoltage detection end.

5. The constant current output power supply circuit according to claim 1, characterized in that: The overcurrent detection circuit comprises: A third capacitor, one end of the third capacitor is coupled to the overcurrent detection end, and the other end of the third capacitor is grounded; an eighth resistor, one end of the eighth resistor being coupled to the overcurrent detection end, and the other end of the eighth resistor being grounded through a ninth resistor; a tenth resistor, one end of the tenth resistor being coupled to the other end of the ninth resistor, and the other end of the tenth resistor being grounded; An eleventh resistor is connected in parallel with the tenth resistor, one end of the eleventh resistor is coupled to the third element end, and the other end of the eleventh resistor is grounded.

6. The constant current output power supply circuit according to claim 1, characterized in that: The feedback circuit comprises: An optical coupling element, the optical coupling element comprising a transmitting end and a receiving end; one end of the receiving end is coupled to the feedback end through a twelfth resistor; a fourth capacitor is coupled between the two ends of the receiving end, and the other end of the receiving end is grounded; One end of the transmitting end is coupled to the secondary output end through a thirteenth resistor; A feedback chip, the feedback chip comprising a voltage positive feedback input terminal, a voltage negative feedback input terminal, a voltage feedback output terminal, a current positive feedback input terminal, a current negative feedback input terminal, a current feedback output terminal, a feedback chip power supply terminal and a feedback chip ground terminal; The other end of the transmitting end is coupled to the voltage feedback output end and / or the current feedback output end, and the transmitting end adjusts the current value of the transmitting end according to the voltage feedback signal of the voltage feedback output end and the current feedback signal of the current feedback output end; The voltage positive feedback input terminal is coupled to the feedback chip power supply terminal through a fourteenth resistor; the voltage negative feedback input terminal is coupled to a voltage feedback unit; The current positive feedback input terminal is coupled to the feedback chip power supply terminal through the fifteenth resistor and the fourteenth resistor in sequence; the current negative feedback input terminal is grounded through a current feedback unit; The feedback chip power supply end is coupled to the positive output end of the output circuit through a feedback chip power supply unit; a third diode, wherein an anode of the third diode is coupled to the other end of the transmitting end, and a cathode of the third diode is coupled to the voltage feedback output end via a sixteenth resistor; a fourth diode, wherein an anode of the fourth diode is coupled to one end of the transmitting end through a seventeenth resistor, and a cathode of the fourth diode is coupled to the current feedback output end through an eighteenth resistor; The feedback chip ground terminal is grounded.

7. The constant current output power supply circuit according to claim 6, characterized in that: The voltage feedback unit comprises: A nineteenth resistor, one end of the nineteenth resistor is coupled to the positive output terminal through a twentieth resistor, and the other end of the nineteenth resistor is coupled to the voltage negative feedback input terminal; A twenty-first resistor, one end of the twenty-first resistor is coupled to the other end of the nineteenth resistor, and the other end of the twenty-first resistor is grounded.

8. The constant current output power supply circuit according to claim 6, characterized in that: The current feedback unit comprises: A twenty-second resistor, one end of which is coupled to the current negative feedback input end through the negative output end of the output circuit, and the other end of which is grounded; The external load is coupled between the positive output terminal and the negative output terminal; A twenty-third resistor, the twenty-third resistor is connected in parallel with the twenty-second resistor.

9. The constant current output power supply circuit according to claim 6, characterized in that: The feedback chip power supply unit comprises: A conversion chip, the conversion chip comprising a voltage input terminal, a voltage output terminal and a conversion chip ground terminal; The voltage input terminal is coupled to the positive output terminal through a twenty-fourth resistor; The voltage output terminal is coupled to the feedback chip power supply terminal; A third energy storage filter capacitor, wherein a positive electrode of the third energy storage filter capacitor is coupled to the voltage output terminal, and a negative electrode of the third energy storage filter capacitor is grounded; A fourth capacitor is connected in parallel with the third energy storage filter capacitor.

10. The constant current output power supply circuit according to claim 1, characterized in that: The output end of the output circuit includes a positive output end and a negative output end; the secondary coil includes a fifth end and a sixth end The output circuit comprises: a fifth diode, wherein an anode of the fifth diode is coupled to the fifth terminal, and a cathode of the fifth diode is coupled to the positive output terminal via a first inductor; a fourth energy storage filter capacitor, wherein a positive electrode of the fourth energy storage filter capacitor is coupled to one end of the first inductor, and a negative electrode of the fourth energy storage filter capacitor is grounded; a fifth energy storage filter capacitor, wherein a positive electrode of the fifth energy storage filter capacitor is coupled to the other end of the first inductor, and a negative electrode of the fifth energy storage filter capacitor is grounded; a fifth capacitor, the fifth capacitor being coupled between the positive output terminal and the negative output terminal; a twenty-fourth resistor, one end of the twenty-fourth resistor being coupled to the anode of the fifth diode, and the other end of the twenty-fourth resistor being coupled to the cathode of the fifth diode via a sixth capacitor; A twenty-fifth resistor, the twenty-fifth resistor is connected in parallel with the twenty-fourth resistor.

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