CIRCUIT FOR SUPPLYING POWER TO A SWITCHING POWER SUPPLY CONTROL CIRCUIT BASED ON AUXILIARY WINDING CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to a Chinese patent application, application number 202211200833.3, entitled "CIRCUITS FOR SUPPLYING POWER TO A SWITCHING POWER SUPPLY CONTROL CIRCUIT BASED ON AUXILIARY WINDING", filed with the China Patent Office on September 29, 2022, the entire contents of which are incorporated herein by reference.

Abstract

A circuit for supplying power to a switching power supply control circuit based on an auxiliary winding, which relates to the technical field of switching power supplies, includes an auxiliary winding, a switching transistor, an LDO, a first diode, a second diode, a forward energy storage capacitor, and a flyback energy storage capacitor, in which the flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor, and the switching transistor charges the flyback energy storage capacitor, and the flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor, and the switching transistor charges the flyback energy storage capacitor. In the forward state, when the voltage of the forward energy storage capacitor is lower than the voltage of the LDO output terminal, the flyback energy storage capacitor supplies power to the control circuit, and when it is higher than the voltage of the LDO output terminal, the forward energy storage capacitor supplies power to the control circuit. Therefore, based on the voltage of the forward energy storage capacitor at that time, the forward energy storage and the flyback energy storage are combined to supply power to the control circuit, and the voltage of the power supply terminal of the control circuit is effectively pulled down by the stable voltage characteristic of the LDO.

Description

[Technical field]

[0001] The present application relates to the technical field of switching power supplies, and in particular to a circuit for powering a switching power supply control circuit based on an auxiliary winding. [Background technology]

[0002] In the Flyback switching power supply technology, auxiliary winding flyback supply or auxiliary winding forward supply is usually adopted to supply power to the control circuit in the Flyback switching power supply. For Flyback switching power supplies with a wide range of input voltages (for example, 50V to 375V voltage) or a wide range of output voltages (for example, 3V to 20V voltage), the voltage supplied to the control circuit in the Flyback supply may reach 70V in the operation mode with a higher output voltage, and the voltage supplied to the control circuit in the forward supply may also reach 70V in the operation mode with a higher input voltage. However, under normal circumstances, the supply voltage of the control circuit should not exceed 60V. If the supply voltage exceeds 60V, the operating temperature of some components will rise, affecting the service life and reliability, and at the same time, the wear of the rectifier elements in the control circuit and the Flyback switching power supply will increase, affecting the reliability of the entire system.

[0003] At present, in order to reduce the voltage of the control circuit power supply end in a wide range input voltage or wide range output voltage mode, the method of double auxiliary winding flyback power supply is usually used to reduce the control circuit power supply voltage, or a boost circuit is added based on a single auxiliary winding flyback power supply to reduce the control circuit power supply voltage. However, whether the double auxiliary winding method or the method of adding a boost circuit is used, although the control circuit power supply voltage can be reduced, both methods increase the cost.

[0004] Therefore, on the premise of controlling costs, how to effectively reduce the voltage at the power supply end of the control circuit of a switching power supply in a wide range of input voltages or a wide range of output voltage modes, reduce system losses, and further improve system reliability has become a problem that awaits an immediate solution by those skilled in the art. Summary of the Invention

[0005] The objective of the present application is to provide a circuit for powering a switching power supply control circuit based on an auxiliary winding, which combines forward power supply and flyback power supply to power the control circuit, thereby reducing the power supply voltage of the control circuit in a wide range of input voltages or a wide range of output voltage modes, and further effectively reducing system losses.

[0006] In order to solve the above technical problems, the present application provides a circuit for supplying power to a switching power supply control circuit based on an auxiliary winding, the circuit including an auxiliary winding, a switching transistor, an LDO, a first diode, a second diode, a forward energy storage capacitor, and a flyback energy storage capacitor, wherein one end of the forward energy storage capacitor and a negative electrode of the first diode are connected to form a common end, which is respectively connected to an output end of the LDO and a power supply end of the control circuit, the other end of the forward energy storage capacitor is grounded, a common end of the forward energy storage capacitor and a positive electrode of the first diode are connected to form a common end, which is connected to an opposite polarity end of the auxiliary winding, the same polarity end of the auxiliary winding is grounded, and a common end of the flyback energy storage capacitor and a positive electrode of the second diode are connected to form a common end, which is connected to one end of the switching transistor. the other end of the switching transistor is grounded, and the negative electrode of the second diode is connected to the input end of the LDO; a forward energy storage circuit formed by the auxiliary winding, the first diode and the forward energy storage capacitor charges the forward energy storage capacitor; a flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor and the switching transistor charges the flyback energy storage capacitor to store energy; in a forward state, when a voltage of the forward energy storage capacitor is smaller than a voltage of the LDO output end, the flyback energy storage capacitor supplies power to the control circuit; and when a voltage of the forward energy storage capacitor is larger than a voltage of the LDO output end, the forward energy storage capacitor supplies power to the control circuit.

[0007] Preferably, the circuit for powering the switching power supply control circuit based on the auxiliary winding further includes a voltage stabilizing capacitor; One end of the voltage stabilizing capacitor is connected to the input terminal of the LDO, and the other end is grounded.

[0008] Preferably, the circuit for supplying power to the switching power supply control circuit based on the auxiliary winding further includes a third diode; The third diode has a positive electrode connected to the output terminal of the LDO and a negative electrode connected to the power supply terminal of the control circuit.

[0009] Preferably, when the switching transistor is a field effect transistor, the circuit for supplying power to the switching power supply control circuit based on the auxiliary winding further includes: one end of the field effect transistor is connected to the other end of the flyback energy storage capacitor, the other end of the field effect transistor is grounded, and the control end is connected to a ZVS control end of the control circuit, used to realize ZVS of the switching power supply.

[0010] Preferably, the circuit for supplying power to the switching power supply control circuit based on the auxiliary winding further includes a first resistor and a second resistor; A common terminal formed by connecting the first resistor and the second resistor in series is connected to a voltage sampling terminal of the control circuit, and the other terminal of the second resistor is grounded and the other terminal of the first resistor is connected to the opposite polarity terminal of the auxiliary winding.

[0011] In order to solve the above technical problems, the present application further provides a switching power supply including a circuit for supplying power to a switching power supply control circuit based on the auxiliary winding.

[0012] The circuit for powering a switching power supply control circuit based on the auxiliary winding provided in the present invention includes an auxiliary winding, a switching transistor, an LDO, a first diode, a second diode, a forward energy storage capacitor, and a flyback energy storage capacitor, in which the flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor, and the switching transistor charges the flyback energy storage capacitor to store energy, and the flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor, and the switching transistor charges the flyback energy storage capacitor to store energy. When powering the control circuit in a forward state, if the voltage of the forward energy storage capacitor is lower than the voltage of the LDO output terminal, the flyback energy storage capacitor supplies power to the control circuit, and if the voltage of the forward energy storage capacitor is higher than the voltage of the LDO output terminal, the forward energy storage capacitor supplies power to the control circuit. Therefore, the technical method provided in this application combines forward energy storage and flyback energy storage to power the control circuit based on the voltage of the forward energy storage capacitor at that time, and effectively pulls down the voltage at the power supply end of the control circuit through the stable voltage characteristics of the LDO.

[0013] The present application also provides a switching power supply, which corresponds to a circuit for supplying power to a switching power supply control circuit based on the above auxiliary winding, and has the same effect.

[0014] In order to more clearly explain the embodiments of the present application, the following provides a brief introduction of drawings that may be used in the embodiments. However, the drawings in the following description are only some of the embodiments of the present application, and it is obvious that a person skilled in the art can obtain other drawings based on these drawings on the premise that no creative work is performed. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a schematic diagram of a circuit for powering a switching power supply control circuit based on an auxiliary winding provided herein. [Diagram 2] FIG. 2 is a schematic diagram of a circuit for powering a switching power supply control circuit based on an auxiliary winding provided in another embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The technical methods in the embodiments of the present application will be described below clearly and completely in conjunction with the drawings in the embodiments of the present application, but it is clear that the described embodiments are only a part of the embodiments of the present application, and are not all of the embodiments. All other embodiments obtained by those skilled in the art on the basis of the embodiments of the present application without performing creative labor, fall within the scope of protection of the present application.

[0017] The gist of this application is to provide a circuit for powering a switching power supply control circuit based on an auxiliary winding, and when powering the control circuit, the forward energy storage capacitor or the flyback energy storage capacitor is used to power the control circuit according to the relationship between the voltage of the forward energy storage capacitor and the voltage at the output end of the LDO. That is, the forward power supply and the flyback power supply are combined to power the control circuit, so that the voltage at the power supply end of the control circuit can be reduced in a special operating mode, and the loss of the system can be effectively reduced.

[0018] In order to allow those skilled in the art to better understand the present invention, the present invention will be described in more detail below in conjunction with drawings and specific embodiments.

[0019] In the Flyback switching power supply technology, auxiliary winding flyback supply or auxiliary winding forward supply is usually adopted to supply power to the control circuit in the Flyback switching power supply. For Flyback switching power supplies with a wide range of input voltages (for example, 50V to 375V voltage) or a wide range of output voltages (for example, 3V to 20V voltage), the voltage supplied to the control circuit in the Flyback supply may reach 70V in the operation mode with a higher output voltage, and the voltage supplied to the control circuit in the forward supply may also reach 70V in the operation mode with a higher input voltage. However, under normal circumstances, the supply voltage of the control circuit should not exceed 60V. If the supply voltage exceeds 60V, the operating temperature of some components will rise, affecting the service life and reliability, and at the same time, the wear of the rectifier elements in the control circuit and the Flyback switching power supply will increase, affecting the reliability of the entire system.

[0020] At present, in order to reduce the voltage of the control circuit power supply end in a wide range input voltage or wide range output voltage mode, the method of double auxiliary winding flyback power supply is usually used to reduce the control circuit power supply voltage, or a boost circuit is added based on a single auxiliary winding flyback power supply to reduce the control circuit power supply voltage. However, whether the double auxiliary winding method or the method of adding a boost circuit is used, although the control circuit power supply voltage can be reduced, both methods increase the cost.

[0021] Under the premise of controlling costs, in order to effectively reduce the voltage at the power supply end of the control circuit of a switching power supply in a wide range of input voltages or a wide range of output voltage modes, and reduce system losses, the present application provides a circuit for powering a switching power supply control circuit based on an auxiliary winding. When the circuit powers the control circuit in a forward state, the forward power supply and flyback power supply are combined with the properties of an LDO to power the control circuit, thereby effectively reducing the voltage at the power supply end of the control circuit in a wide range of input or output modes.

[0022] FIG. 1 is a schematic diagram of a circuit for powering a switching power supply control circuit based on an auxiliary winding provided in the present application. As shown in FIG. 1, the circuit includes an auxiliary winding W, a switching transistor Qa, an LDO, a first diode D1, a second diode D2, a forward energy storage capacitor C1, and a flyback energy storage capacitor C2.

[0023] The common terminal generated by connecting one end of the forward energy storage capacitor C1 and the negative electrode of the first diode D1 is connected to the output terminal OUT1 of the LDO and the power supply terminal VCC of the control circuit, the other end of the forward energy storage capacitor C1 is grounded, the common terminal generated by connecting the positive electrode of the first diode D1 and one end of the flyback energy storage capacitor C2 is connected to the opposite polarity terminal of the auxiliary winding, the same polarity terminal of the auxiliary winding W is grounded, the common terminal generated by connecting the other end of the flyback energy storage capacitor C2 and the positive electrode of the second diode D2 is connected to one end of the switching transistor Qa, the other end of the switching transistor Qa is grounded, and the negative electrode of the second diode D2 is connected to the input terminal IN1 of the LDO.

[0024] In practice, in the switching power supply, when the power switch Qp, which is coupled to the same polarity end of the primary winding of the transformer T and controlled by the control circuit, is cut off, the power supply circuit of the control circuit enters a flyback state, at this time, the auxiliary winding W, the flyback energy storage capacitor C2 and the switching transistor Qa form a flyback energy storage circuit, and current flows from the ground end of the switching transistor Qa through the switching transistor Qa to the flyback energy storage capacitor C2, and then flows from the flyback energy storage capacitor C2 to the auxiliary winding W and further to the ground end to form the flyback energy storage circuit, charging the flyback energy storage capacitor C2 to store energy.

[0025] When the power switch Qp is turned on, the power supply circuit is in the forward state. At this time, the auxiliary winding W, the first diode D1 and the forward energy storage capacitor C1 form a forward energy storage circuit, and a current flows from the ground end of the auxiliary winding W through the auxiliary winding W toward the first diode D1, and then flows from the first diode D1 toward the forward energy storage capacitor C1 to the ground end, thereby forming the forward energy storage circuit and charging the forward energy storage capacitor C1 to store energy.

[0026] When the power switch Qp is turned on and the power supply circuit is in the forward state to supply power to the control circuit, if the voltage of the forward energy storage capacitor C1 is smaller than the voltage of the LDO output terminal OUT1, the flyback energy storage capacitor C2 supplies the electrical energy stored in the flyback state to the control circuit, and if the voltage of the forward energy storage capacitor C1 is greater than the voltage of the LDO output terminal OUT1, the forward energy storage capacitor C1 supplies power to the control circuit.

[0027] A low dropout regulator (LDO) is used to stabilize voltage, so if the input voltage of the LDO input terminal IN1 is greater than the stabilized voltage of the LDO, the LDO will always output a stabilized voltage. It should be noted that, as shown in FIG. 1, if the positive pole voltage Vaux of the first diode D1 is not greater than the negative pole voltage, the conduction of the first diode D1 cannot be guaranteed, and for the same reason, if the positive pole voltage Vsw of the second diode D2 is not greater than the negative pole voltage, the second diode D2 cannot be made conductive, and since there is a voltage drop across the diode during conduction, the negative pole voltage is the positive pole voltage minus the voltage drop.

[0028] In practice, as shown in Fig. 1, the voltage of the positive pole of the first diode D1 is Vaux=Vin*Naux / Np, where Vin is the input voltage of the switching power supply, Naux is the number of turns of the auxiliary winding, and Np is the number of turns of the primary winding of the transformer T. The voltage of the positive pole of the second diode D2 is Vsw=Vaux+Vout*Naux / Ns, where Vout is the output voltage of the switching power supply, and Ns is the number of turns of the secondary winding of the transformer T. The voltage across the flyback energy storage capacitor C2 is Vc2=Vsw-Vaux, so the positive voltage Vsw of the second diode D2 is equal to the sum of the voltage across the flyback energy storage capacitor C2 and the positive voltage of the first diode D1, i.e., Vsw=Vc2+Vaux.

[0029] It should be further explained that when the common node voltage where the first diode D1 and the forward energy storage capacitor C1 are connected is different from the voltage at the LDO output terminal OUT1, the one with the larger voltage value will supply power to the control circuit. Therefore, based on the relationship between the voltage of the forward energy storage capacitor C1 and the voltage at the LDO output terminal OUT1 and the properties of the LDO, the supply voltage of the control circuit can be effectively reduced in a wide range of input voltages or a wide range of output voltage modes. That is, the combination of the forward power supply and the flyback power supply can effectively reduce the voltage at the VCC terminal of the control circuit. For ease of understanding, an example is given below.

[0030] When the power switch Qp is conducting and the power supply circuit is in the forward state, assume that Vaux = 7V, the voltage across the flyback energy storage capacitor C2 is Vc2 = 20V, the voltage drops of both the first diode D1 and the second diode D2 are Vx = 1V, and the regulated voltage of the LDO is Vy = 15V. At this time, Vc1 = Vaux - Vx = 6V, Vsw = Vc2 + Vaux = 20 + 7 = 27V, the voltage Vin1 at the input terminal IN1 of the LDO is Vin1 = Vsw - Vx = 27 - 1 = 26V, and the voltage Vout1 at the output terminal OUT1 of the LDO is Vout1 = 15V. From Figure 1, when the forward energy storage capacitor C1 and the LDO output terminal are at one node, Vc1 < Vout1. Since the VCC power supply follows the higher voltage of the LDO output terminal and the forward energy storage capacitor C1, Vout1 = 15V supplies power to the control circuit, so VCC = Vout1 = 15V. At this time, the electrical energy passing through the LDO is the electrical energy when the flyback energy storage circuit charges the flyback energy storage capacitor C2 in the flyback state. That is, it can be seen that the control circuit is powered by flyback.

[0031] When Vaux = 20V, Vc2 = 20V, Vx = 1V, and the regulated voltage of the LDO is Vy = 15V, Vc1 = Vaux - Vx = 19V, Vsw = Vc2 + Vaux = 40V, and the voltage Vin1 at the input terminal IN1 of the LDO is Vin1 = Vsw - Vx = 40 - 1 = 39V. Due to the voltage regulation characteristics of the LDO, the voltage Vout1 at the output terminal OUT1 of the LDO is Vout1 = 15V. At this time, since Vc1 > Vout1, Vc1 = 19V supplies power to the control circuit. That is, VCC = Vc1 = 19V. At this time, it can be seen that the electrical energy when the forward energy storage capacitor C1 is charged by the forward energy storage circuit supplies power to the control circuit. That is, the control circuit is powered by forward.

[0032] From the above, if Vaux - Vx > Vy, then VCC = Vaux - Vx; if Vaux - Vx < Vy and Vsw - Vx > Vy, then VCC = Vy; if Vaux - Vx < Vy and Vsw - Vx < Vy, then VCC = Vsw - Vx. Among them, Vy is the stable voltage of the LDO.

[0033] Therefore, when Vaux is relatively high, power is supplied in the forward mode, and when Vaux is relatively small, power is supplied in the flyback mode. The technical method provided in this application combines forward power supply and flyback power supply to supply power to the control circuit, thereby avoiding the situation where in a wide range of inputs or a wide range of outputs, the power supply voltage of the control circuit exceeds the maximum voltage that can be tolerated, the operating temperature of some components rises, which affects the service life of the components and further affects the reliability of the system.

[0034] The circuit for supplying power to the switching power supply control circuit based on the auxiliary winding provided in the embodiment of this application includes an auxiliary winding, a switching transistor, an LDO, a first diode, a second diode, a forward energy storage capacitor, and a flyback energy storage capacitor. Among them, the flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor, and the switching transistor charges the flyback energy storage capacitor to store energy. When supplying power to the control circuit in the forward state, if the voltage of the forward energy storage capacitor is smaller than the voltage at the output end of the LDO, the flyback energy storage capacitor supplies power to the control circuit; if the voltage of the forward energy storage capacitor is larger than the voltage at the output end of the LDO, the forward energy storage capacitor supplies power to the control circuit. That is, the technical method provided in this application combines forward energy storage and flyback energy storage to supply power to the control circuit based on the voltage of the forward energy storage capacitor at that time, and effectively reduces the voltage at the power supply end of the control circuit due to the stable voltage characteristic of the LDO.

[0035] FIG. 2 is a schematic diagram of a circuit for powering a switching power supply control circuit based on an auxiliary winding provided in another embodiment of the present application. Based on the above embodiment, in order to avoid fluctuations in the voltage at the input end of the LDO, the circuit for powering a switching power supply control circuit based on an auxiliary winding provided in the embodiment of the present application further includes a voltage stabilizing capacitor C3, as shown in FIG. 2, one end of the voltage stabilizing capacitor C3 is connected to the input end IN1 of the LDO and the other end is grounded.

[0036] In practice, if the second diode D2 is an ideal diode, no parasitic capacitance will be generated in the second diode D2 during use, and the voltage across the LDO output will be a stable voltage. However, in actual applications, the second diode D2 cannot reach the ideal state, and will usually have parasitic capacitance, causing fluctuations in Vsw, which will cause voltage fluctuations at the LDO input, and if the LDO input voltage fluctuates to a negative voltage, the LDO may be damaged.

[0037] Therefore, in order to avoid damage to the LDO and improve the reliability of the entire system, the circuit for powering the switching power supply control circuit based on the auxiliary winding provided in this application further includes a voltage stabilization capacitor C3 between the second diode D2 and the LDO.

[0038] After adding the voltage stabilization capacitor C3, when the power switch Qp is turned on, in addition to the auxiliary winding W, the first diode D1, and the forward energy storage capacitor C1 forming a forward energy storage circuit, the auxiliary winding W, the flyback energy storage capacitor C2, the second diode D2, and the voltage stabilization capacitor C3 also form a forward energy storage circuit, and the current flows from the ground end of the auxiliary winding W through the auxiliary winding W to the flyback energy storage capacitor C2, and then flows through the second diode D2 to the voltage stabilization capacitor C3, charging the voltage stabilization capacitor C3 to store energy. That is, in the forward state, the forward energy storage includes two energy storage circuits, each of which charges the forward energy storage capacitor C1 and the voltage stabilization capacitor C3.

[0039] The circuit for powering a switching power supply control circuit based on the auxiliary winding provided in the embodiment of the present application adds a voltage stabilizing capacitor between the second diode and the LDO, thereby preventing voltage fluctuations at the input terminal of the LDO that could cause damage to the LDO, thereby reducing system losses and improving reliability.

[0040] Based on the above embodiment, in order to avoid reverse conduction between the LDO input terminal and the control circuit VCC terminal, the circuit for powering the switching power supply control circuit based on the auxiliary winding provided in the present application further includes a third diode D3, the positive electrode of which is connected to the output terminal OUT1 of the LDO, and the negative electrode of which is connected to the power supply terminal VCC of the control circuit, as shown in FIG. 2.

[0041] The circuit for supplying power to a switching power supply control circuit based on the auxiliary winding provided in the embodiment of the present application adds a diode between the LDO output terminal and the control circuit power supply terminal to prevent reverse conduction between the LDO input terminal and the VCC terminal of the control circuit, thereby further improving the reliability of the switching power supply.

[0042] In a specific implementation, the switching transistor Qa may be a diode or a field effect transistor, which is not limited in the present application. When the switching transistor Qa is a field effect transistor, as shown in Figure 2, one end of the field effect transistor Qa is connected to the other end of the flyback energy storage capacitor C2, the other end of the field effect transistor Qa is grounded, and the control end is connected to the control end ZVS-DR of the control circuit.

[0043] Before the power switch Qp is turned on, the control circuit generates a ZVS control signal according to the voltage at point Vaux, and controls the conduction of the field effect transistor Qa by the control terminal ZVS-DR, thereby forming a resonant current between the auxiliary winding W, the flyback energy storage capacitor C2 and the switching transistor Qa. The resonant current affects the voltage of the power switch Qp to generate downward resonance, and at the same time, the magnetic coupling between the auxiliary winding W and the transformer T realizes the reverse flow of the excitation current of the primary winding, and reversely extracts the junction capacitance charge of the primary power switch Qp, thereby pulling down the Vds voltage of the primary power switch to zero, thereby realizing ZVS of the primary power switch Qp, and effectively providing the efficiency of the switching power supply.

[0044] The circuit for supplying power to a switching power supply control circuit based on the auxiliary winding provided in the embodiments of the present application configures the switching transistor as a field effect transistor, and connects the control end of the field effect transistor to the ZVS control end of the control circuit, thereby realizing ZVS of the switching power supply, improving the operating efficiency of the system, and further improving the reliability of the system.

[0045] 2, in a preferred embodiment, the circuit for powering a switching power supply control circuit based on the auxiliary winding provided in the present application further includes a first resistor R1 and a second resistor R2, the common terminal formed by the series connection of the first resistor R1 and the second resistor R2 is connected to the voltage sampling terminal DEM of the control circuit, and the other terminal of the second resistor R2 is grounded and connected to the opposite polarity terminal of the auxiliary winding W. The first resistor R1 and the second resistor R2 realize voltage division sampling for Vaux, and further generate a control signal for ZVS.

[0046] The circuit for supplying power to a switching power supply control circuit based on the auxiliary winding provided in the embodiments of the present application further includes a first resistor and a second resistor, and a common terminal generated by connecting the first resistor and the second resistor in series is connected to a voltage sampling terminal of the control circuit, and the other terminal of the second resistor is grounded and connected to the opposite polarity terminal of the auxiliary winding, thereby realizing voltage division sampling for the opposite polarity terminal of the auxiliary winding by the first resistor and the second resistor to generate a ZVS control signal for the switching power supply, and further realizing ZVS for the switching power supply to improve the operating efficiency of the system.

[0047] In the above embodiments, a circuit for supplying power to a switching power supply control circuit based on an auxiliary winding has been described in detail. In the embodiments of the present application, a switching power supply including a circuit for supplying power to a switching power supply control circuit based on the auxiliary winding provided in the above embodiments is also provided. The beneficial effects produced correspond to those of the circuit for supplying power to a switching power supply control circuit based on the auxiliary winding in the above embodiments, and the effects are the same as those described above, so they will not be repeated here.

[0048] As above, the circuit for powering a switching power supply control circuit based on the auxiliary winding provided in the present application has been introduced in detail. Each embodiment of the specification is described in a progressive manner, and the focus of each embodiment is on the differences from other embodiments, and the same or similar parts between each embodiment can be mutually referenced. The apparatus disclosed in the embodiment corresponds to the method disclosed in the embodiment and is relatively simple to describe, so that the relevant points can be referred to the description of the method part. It is pointed out that a person skilled in the art can make some improvements and modifications to the present application without departing from the principles of the present application, and such improvements and modifications are also within the scope of the claims of the present application.

[0049] It should also be explained that relational terms such as first, second, etc. are used herein only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any substantial relationship or sequence between those entities or operations. Also, the terms "comprise", "include", or any other variation thereof cover non-exclusive inclusions, such that a process, method, article, or facility that includes a set of elements includes not only those elements, but also other elements not expressly listed or elements inherent to that type of process, method, article, or facility. In a context without further limitations, an element qualified by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or facility that includes the element.

Claims

1. 1. A circuit for powering a switching power supply control circuit based on an auxiliary winding, comprising: an auxiliary winding; a switching transistor; a low dropout regulator (LDO); a first diode; a second diode; a forward energy storage capacitor; and a flyback energy storage capacitor; a common end generated by connecting one end of the forward energy storage capacitor and the negative electrode of the first diode is connected to the output end of the LDO and the power supply end of the control circuit, the other end of the forward energy storage capacitor is grounded, a common end generated by connecting the positive electrode of the first diode and one end of the flyback energy storage capacitor is connected to the opposite polarity end of the auxiliary winding, the same polarity end of the auxiliary winding is grounded, a common end generated by connecting the other end of the flyback energy storage capacitor and the positive electrode of the second diode is connected to one end of the switching transistor, the other end of the switching transistor is grounded, and the negative electrode of the second diode is connected to the input end of the LDO, a forward energy storage circuit formed by the auxiliary winding, the first diode and the forward energy storage capacitor charges the forward energy storage capacitor, and a flyback energy storage circuit formed by the auxiliary winding, the flyback energy storage capacitor and the switching transistor charges the flyback energy storage capacitor to store energy, In a forward state, when the voltage of the forward energy storage capacitor is smaller than the voltage of the LDO output terminal, the flyback energy storage capacitor supplies power to the control circuit, and when the voltage of the forward energy storage capacitor is larger than the voltage of the LDO output terminal, the forward energy storage capacitor supplies power to the control circuit. A circuit that powers a switching power supply control circuit based on an auxiliary winding.

2. further comprising a voltage stabilizing capacitor; One end of the voltage stabilizing capacitor is connected to the input terminal of the LDO, and the other end is grounded.

2. A circuit for powering a switching power supply control circuit based on the auxiliary winding of claim 1.

3. further comprising a third diode; The positive electrode of the third diode is connected to the output terminal of the LDO, and the negative electrode is connected to the power supply terminal of the control circuit.

3. A circuit for powering a switching power supply control circuit based on the auxiliary winding of claim 2.

4. When the switching transistor is a field effect transistor, One end of the field effect transistor is connected to the other end of the flyback energy storage capacitor, the other end of the field effect transistor is grounded, and a control end is connected to a ZVS control end of the control circuit, for realizing ZVS of the switching power supply.

2. A circuit for powering a switching power supply control circuit based on the auxiliary winding of claim 1.

5. Further comprising a first resistor and a second resistor, a common terminal formed by connecting the first resistor and the second resistor in series is connected to a voltage sampling terminal of the control circuit, the other terminal of the second resistor is grounded, and the other terminal of the first resistor is connected to a different polarity terminal of the auxiliary winding.

5. A circuit for powering a switching power supply control circuit based on an auxiliary winding as claimed in claim 4.

6. A switching power supply, comprising a circuit for supplying power to a switching power supply control circuit based on the auxiliary winding according to any one of claims 1 to 5.

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