Circuit for powering a switching power supply control circuit based on an auxiliary winding

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] This application relates to the technical field of switching power supplies, and more particularly to a circuit for powering a switching power supply control circuit based on an auxiliary winding. [Background technology]

[0002] Flyback switching power supply technology typically uses an auxiliary winding flyback feed or auxiliary winding forward feed to power the control circuit in a flyback switching power supply. For flyback switching power supplies with a wide input voltage range (e.g., 50V to 375V) or a wide output voltage range (e.g., 3V to 20V), the voltage supplied to the control circuit with a flyback feed can reach 70V in operating modes with higher output voltages, while the voltage supplied to the control circuit with a forward feed can also reach 70V in operating modes with higher input voltages. However, under normal circumstances, the control circuit's power supply voltage should not exceed 60V. If the power supply voltage exceeds 60V, the operating temperature of some components will rise, affecting their service life and reliability, and increasing wear on the rectifier elements in the control circuit and flyback switching power supply, thereby affecting the reliability of the entire system.

[0003] Currently, in order to reduce the voltage at the control circuit power supply end in a wide input voltage range or a wide output voltage range mode, the usual method is to use a double auxiliary winding flyback power supply to reduce the control circuit power supply voltage, or to add a boost circuit 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 can reduce the control circuit power supply voltage, both methods increase costs.

[0004] Therefore, under the premise of controlling costs, how to effectively reduce the voltage at the control circuit power supply end 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 needs to be solved by those skilled in the art as soon as possible. Summary of the Invention

[0005] The objective of this 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 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 the negative electrode of the first diode are connected to form a common terminal which is respectively connected to the output terminal of the LDO and the power supply terminal of the control circuit, the other end of the forward energy storage capacitor is grounded, a common terminal which is connected to 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, and a common terminal which is connected to 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. 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 end, the flyback energy storage capacitor supplies power to the control circuit. When the voltage of the forward energy storage capacitor is larger than the voltage of the LDO output end, the forward energy storage capacitor supplies power to the control circuit.

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

[0008] Preferably, the circuit that supplies power to the switching power supply control circuit based on the auxiliary winding further includes 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.

[0009] Preferably, when the switching transistor is a field-effect transistor, the circuit that supplies 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, so as 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; The common terminal formed by connecting the first resistor and the second resistor in series is connected to the 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] 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 an auxiliary winding provided by 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, wherein 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 smaller than the voltage at the LDO output end, the flyback energy storage capacitor powers the control circuit, and if the voltage of the forward energy storage capacitor is greater than the voltage at the LDO output end, the forward energy storage capacitor powers the control circuit. Therefore, the technical approach proposed 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 reduces the voltage at the power supply end of the control circuit using the stable voltage characteristics of the LDO.

[0013] The present invention also provides a switching power supply, which corresponds to a circuit that supplies 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 to the drawings that need to 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 without performing any creative work. [Brief explanation 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. [Figure 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 INVENTION

[0016] The following clearly and completely describes the technical solutions in the embodiments of the present application 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 do not include all of the embodiments. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present application without performing any creative work fall within the scope of protection of the present application.

[0017] The core 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 control circuit is powered by either the forward energy storage capacitor or the flyback energy storage capacitor according to the relationship between the voltage of the forward energy storage capacitor and the voltage at the output terminal of the LDO. That is, by combining the forward power supply and the flyback power supply to power the control circuit, the voltage at the power supply terminal of the control circuit can be reduced in a special operating mode, and the system loss can be effectively reduced.

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

[0019] Flyback switching power supply technology typically uses an auxiliary winding flyback feed or auxiliary winding forward feed to power the control circuit in a flyback switching power supply. For flyback switching power supplies with a wide input voltage range (e.g., 50V to 375V) or a wide output voltage range (e.g., 3V to 20V), the voltage supplied to the control circuit with a flyback feed can reach 70V in operating modes with higher output voltages, while the voltage supplied to the control circuit with a forward feed can also reach 70V in operating modes with higher input voltages. However, under normal circumstances, the control circuit's power supply voltage should not exceed 60V. If the power supply voltage exceeds 60V, the operating temperature of some components will rise, affecting their service life and reliability, and increasing wear on the rectifier elements in the control circuit and flyback switching power supply, thereby affecting the reliability of the entire system.

[0020] Currently, in order to reduce the voltage at the control circuit power supply end in a wide input voltage range or a wide output voltage range mode, the usual method is to use a double auxiliary winding flyback power supply to reduce the control circuit power supply voltage, or to add a boost circuit 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 can reduce the control circuit power supply voltage, both methods increase costs.

[0021] 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 thereby reduce system losses, while maintaining cost control, the present application provides a circuit for powering the control circuit of a switching power supply based on an auxiliary winding. When the circuit powers the control circuit in the 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 voltages or a wide range of output voltage 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 formed 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, respectively; the other end of the forward energy storage capacitor C1 is grounded; the common terminal formed 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 formed 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 connected to the same polarity end of the primary winding of the transformer T and controlled by the control circuit, is turned off, the power supply circuit of the control circuit enters a flyback state, and 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 from the flyback energy storage capacitor C2 to the auxiliary winding W and then to the ground end, thereby completing the flyback energy storage circuit and 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. 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 and reaches 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; 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 voltages. When the input voltage at 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 Figure 1, the positive pole voltage Vaux of the first diode D1 must be greater than the negative pole voltage to ensure conduction of the first diode D1. For the same reason, the positive pole voltage Vsw of the second diode D2 must be greater than the negative pole voltage to ensure conduction of the second diode D2. When the second diode D2 is conducting, due to the voltage drop across the diode, the negative pole voltage is the positive pole voltage minus the voltage drop.

[0028] 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 positive pole voltage 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 pole 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 pole voltage of the first diode D1, i.e., Vsw=Vc2+Vaux.

[0029] It should also be noted that if the common node voltage between the first diode D1 and the forward energy storage capacitor C1 is different from the voltage at the LDO output terminal OUT1, the voltage with the larger value will power 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 characteristics of the LDO, it is possible to effectively reduce the control circuit power supply voltage over a wide range of input voltages or output voltage modes. That is, the combination of forward power supply and 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 conducts 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, the control circuit is powered by Vout1 = 15V, so VCC = Vout1 = 15V. At this time, the electrical energy passing through the LDO is the electrical energy when the flyback energy storage circuit in the flyback state charges the flyback energy storage capacitor C2. 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, the control circuit is powered by Vc1 = 19V. That is, VCC = Vc1 = 19V. At this time, it can be seen that the electrical energy when the forward energy storage circuit charges the forward energy storage capacitor C1 is supplied 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, it supplies power in the forward mode, and when Vaux is relatively small, it supplies power 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 wide range of outputs, the power supply voltage of the control circuit exceeds the maximum voltage that can be tolerated, causing the operating temperature of some components to rise, affecting the service life of the components, and further affecting 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 characteristics 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 voltage fluctuations at the input end of the LDO, the circuit for powering a switching power supply control circuit based on an auxiliary winding provided in this 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 stable. However, in actual applications, the second diode D2 cannot reach an ideal state, and parasitic capacitance will usually be generated, causing fluctuations in Vsw, which will result in voltage fluctuations at the LDO input. 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 provided in this application that supplies power to the switching power supply control circuit based on the auxiliary winding adds 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 conductive, in addition to the auxiliary winding W, first diode D1, and forward energy storage capacitor C1 forming a forward energy storage circuit, the auxiliary winding W, flyback energy storage capacitor C2, second diode D2, and voltage stabilization capacitor C3 also form a forward energy storage circuit, with current flowing from the ground end of the auxiliary winding W through the auxiliary winding W to the flyback energy storage capacitor C2, then via the second diode D2 to the voltage stabilization capacitor C3, charging the voltage stabilization capacitor C3 and storing 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 stabilization capacitor between the second diode and the LDO, thereby preventing voltage fluctuations at the input terminal of the LDO from damaging the LDO, thereby reducing system losses and improving reliability.

[0040] Based on the above embodiment, in order to avoid reverse conduction between the input terminal of the LDO and the VCC terminal of the control circuit, the circuit for powering the switching power supply control circuit based on the auxiliary winding provided in this 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 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, thereby preventing reverse conduction between the LDO input terminal and the VCC terminal of the control circuit and 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] Until the power switch Qp is turned on, the control circuit generates a ZVS control signal based on the voltage at point Vaux and controls the conduction of the field-effect transistor Qa via 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, generating downward resonance. 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 reducing the Vds voltage of the primary power switch to zero, thereby achieving ZVS for the primary power switch Qp and effectively improving the efficiency of the switching power supply.

[0044] The circuit for powering a switching power supply control circuit based on an auxiliary winding provided in the embodiment of the present application uses a field-effect transistor as the switching transistor, and the control end of the field-effect transistor is connected to the ZVS control end of the control circuit, thereby realizing ZVS for 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, a circuit for powering a switching power supply control circuit based on an auxiliary winding provided herein 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 also 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 embodiment of the present application further includes a first resistor and a second resistor, and the common terminal formed by connecting the first resistor and the second resistor in series is connected to the voltage sampling terminal of the control circuit, and the other terminal of the second resistor is grounded. The other terminal of the first resistor is 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] The above embodiments have described in detail the circuit for supplying power to a switching power supply control circuit based on an auxiliary winding. However, the embodiments of the present application also provide a switching power supply including the circuit for supplying power to a switching power supply control circuit based on the auxiliary winding provided in the above embodiments. The beneficial effects achieved correspond to those of the circuit for supplying power to a switching power supply control circuit based on an 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 mentioned above, the circuit for powering a switching power supply control circuit based on an auxiliary winding provided in the present application has been introduced in detail. Each embodiment of the specification is described in a step-by-step manner, with the focus being on the differences between each embodiment and other embodiments. The same or similar parts between the embodiments can be referenced. The devices disclosed in the embodiments correspond to the methods disclosed in the embodiments and are relatively simple to describe. Therefore, for relevant points, please refer to the method description. Those skilled in the art may make minor improvements and modifications to the present application without departing from the principles of the present application, and these 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 and do not necessarily require or imply any substantial relationship or sequence between those entities or operations. Furthermore, 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 that are inherent in that type of process, method, article, or facility. In a more limiting context, an element qualified by the phrase "comprising a..." does not exclude the presence of additional identical elements within the process, method, article, or facility that includes that element.

Claims

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

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

3. further comprising a third diode; a positive electrode of the third diode connected to the output terminal of the LDO regulator and a negative electrode of the third diode connected to the power supply terminal of the switching power supply 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 element 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 of the field effect transistor is connected to a ZVS control end of the switching power supply control circuit, for realizing ZVS of the switching power supply.

10. 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 switching power supply control circuit, the other terminal of the second resistor is grounded, and the other terminal of the first resistor is connected to an opposite polarity terminal of the auxiliary winding.

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

Images