Switching power supply, switching power supply converter and control method thereof

Abstract

This application provides a switching power supply, a switching power converter, and a control method thereof. The switching power converter includes: a first switching transistor; a transformer including a first winding and a second winding, the first winding and the first switching transistor being connected; and an asymmetric resonant unit including a resonant capacitor and a second switching transistor, wherein a branch of the resonant capacitor connected in series with the second switching transistor is connected in parallel with a target winding, the target winding being either the first winding or the second winding. The asymmetric resonant unit is configured such that: when the first switching transistor is turned off and the voltage of the target winding is greater than a first threshold, the second switching transistor is turned on, and the freewheeling current generated by the target winding charges the resonant capacitor; when the first switching transistor is turned off and the voltage of the target winding is less than a second threshold, the second switching transistor is turned off, so that the resonant capacitor does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold.

Description

Technical Field

[0001] This application relates primarily to the field of electronic technology, and in particular to a switching power supply, a switching power supply converter, and a control method thereof. Background Technology

[0002] Switching power converters are a common topology in the current field of small and medium power switching power supplies. Their conventional control logic is as follows: after the transformer freewheeling phase ends, the system inductance and system capacitance jointly generate an LC resonance. The power transistor is triggered to turn on when its drain-source voltage oscillates to the valley of the LC resonance, a technique known as valley-turn-on. The system inductance includes the parasitic inductance of the power transistor and the equivalent inductance of the transformer coil, while the system capacitance includes the parasitic capacitance of the power switching transistor.

[0003] However, existing switching power converters suffer from switching losses because the charge stored in parasitic capacitors is directly discharged through the power transistors when the power is turned on. Summary of the Invention

[0004] This application addresses the aforementioned technical problems by providing a switching power supply converter that can reduce the switching losses generated by the switching power supply converter.

[0005] To address the aforementioned technical problems, this application provides a switching power converter, comprising: a first switching transistor; a transformer including a first winding and a second winding, the first winding and the first switching transistor being connected; an asymmetric resonant unit including a resonant capacitor and a second switching transistor, wherein a branch of the resonant capacitor connected in series with the second switching transistor is connected in parallel with a target winding, the target winding being either the first winding or the second winding; the asymmetric resonant unit is configured to: when the first switching transistor is turned off and the voltage of the target winding is greater than a first threshold, the second switching transistor is turned on, and the freewheeling current generated by the target winding charges the resonant capacitor; when the first switching transistor is turned off and the voltage of the target winding is less than a second threshold, the second switching transistor is turned off, so that the resonant capacitor does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold; a control unit connected to the control terminal of the first switching transistor, the control unit being configured to: when the drain-source voltage of the first switching transistor is detected to reach the target threshold in the resonant trough of the system LC resonance, control the first switching transistor to turn on, so that the transformer outputs a preset voltage.

[0006] In one embodiment of this application, the first end of the resonant capacitor is connected to the first end of the second switching transistor, the second end of the resonant capacitor is connected to the first end of the target winding and the control end of the second switching transistor, the control end of the second switching transistor is connected to the first end of the target winding, and the second end of the second switching transistor is connected to the second end of the target winding.

[0007] In one embodiment of this application, the asymmetric resonant unit is further configured such that: before the second switch is turned off and after the freewheeling is completed, the resonant capacitor Cr participates in the initial LC resonance generated by the switching power converter; the second winding includes an auxiliary winding, the transformer includes a primary side, the first winding and the auxiliary winding are respectively disposed on the primary side, and the capacitance value of the resonant capacitor is positively correlated with the first equivalent total capacitance value, the oscillation amplitude ratio, and the turns ratio, wherein the first equivalent total capacitance value is the equivalent total capacitance value of the switching power converter excluding the resonant capacitor, the oscillation amplitude ratio is the ratio of the oscillation amplitude of the system LC resonance to the oscillation amplitude of the initial LC resonance, and the turns ratio is the ratio of the number of turns of the first winding to the number of turns of the auxiliary winding.

[0008] In one embodiment of this application, the switching power converter further includes a winding voltage detector connected between a first end of the target winding and a control terminal of the second switching transistor. The winding voltage detector is used to turn on the second switching transistor when the voltage of the target winding is greater than the first threshold, and to turn off the second switching transistor when the voltage of the target winding is less than the second threshold.

[0009] In one embodiment of this application, the second winding includes a secondary winding and an auxiliary winding, and the target winding is the first winding, the secondary winding, or the auxiliary winding; the transformer includes a primary side and a secondary side, the first winding and the auxiliary winding are respectively disposed on the primary side, and the secondary winding is disposed on the secondary side; the switching power converter includes an input terminal and an output terminal, the input terminal is used to receive external power supply, and the input terminal is connected to the first winding; the output terminal is used to output the preset voltage, and the output terminal is connected to the secondary winding.

[0010] In one embodiment of this application, the target winding is the auxiliary winding, and the first end of the resonant capacitor, the first end of the second switching transistor, and the control unit share a common ground.

[0011] In one embodiment of this application, the second winding includes a secondary winding, and the target winding is either the first winding or the secondary winding; the transformer includes a primary side and a secondary side, the first winding is disposed on the primary side, and the secondary winding is disposed on the secondary side; the switching power converter includes an input terminal and an output terminal, the input terminal is used to receive external power supply, and the input terminal is connected to the first winding; the output terminal is used to output the preset voltage, and the output terminal is connected to the secondary winding.

[0012] In one embodiment of this application, the second winding includes a secondary winding, and the target winding is either the first winding or the secondary winding; the transformer includes a primary side and a secondary side, the first winding is disposed on the primary side, and the secondary winding is disposed on the secondary side; the switching power converter includes an input terminal and an output terminal, the input terminal is used to receive external power supply, and the input terminal is connected to the second end of the first winding; the output terminal is used to output the preset voltage, and the output terminal is connected to the first end of the first winding.

[0013] In one embodiment of this application, the second winding includes an auxiliary winding, and the target winding is either the first winding or the auxiliary winding; the transformer includes a primary side and a secondary side, and the first winding and the auxiliary winding are respectively disposed on the primary side; the switching power converter includes an input terminal and an output terminal, the input terminal is used to receive external power supply, and the input terminal is respectively connected to the first end of the first winding; the output terminal is used to output the preset voltage, and the output terminal is connected to the first end of the first winding.

[0014] In one embodiment of this application, the switching power converter further includes: a first capacitor, a first resistor, and a first diode. The first capacitor and the first resistor are connected in parallel. The first terminal of the first capacitor and the first terminal of the first resistor are respectively connected to the first terminal of the first winding. The second terminal of the first capacitor and the second terminal of the first resistor are respectively connected to the cathode of the first diode. The anode of the first diode is respectively connected to the first terminal of the first winding and the first terminal of the first switching transistor. The second terminal of the first switching transistor is connected to the first terminal of the first winding, and the second terminal of the first switching transistor is grounded.

[0015] This application also provides a control method for a switching power converter, applicable to the switching power converter described above. The control method includes: when the voltage of the target winding is greater than a first threshold, turning on the second switching transistor, allowing the target winding to perform inductor freewheeling, and the freewheeling current of the target winding charging the resonant capacitor; when the voltage of the target winding is less than a second threshold, turning off the second switching transistor so that the resonant capacitor does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold; and when the drain-source voltage of the first switching transistor is detected to reach the target threshold in the resonant trough of the system LC resonance, controlling the first switching transistor to turn on so that the transformer outputs a preset voltage.

[0016] This application also proposes a switching power supply, including the switching power converter described above.

[0017] This application improves the initial resonant energy of the resonant system by setting an asymmetric resonant unit connected in parallel with the transformer winding via a series branch, and turning on the second switch when the first switch is turned off and the target winding voltage is greater than a first threshold. The freewheeling current of the target winding is used to charge the resonant capacitor. When the target winding voltage is less than a second threshold, the second switch is turned off, and the switching power converter generates system LC resonance. The resonant capacitor does not participate in the system LC resonance. Compared with a switching power converter without a resonant capacitor, the total capacitance value of the system LC resonance remains unchanged. Since the voltage oscillation amplitude of the LC resonance is positively correlated with the initial resonant energy of the resonant system and negatively correlated with the total capacitance value of the resonant system, the above design increases the voltage oscillation amplitude of the system LC resonance. This can pull the resonant valley value of the drain-source voltage of the first switch to a lower level, thereby allowing the control unit to turn on the first switch at the target threshold of the resonant valley of the system LC resonance. That is, controlling the drain-source voltage of the first switch to turn on when it is close to 0V, thereby reducing the switching losses caused by parasitic capacitance discharge. Attached Figure Description

[0018] The accompanying drawings are included to provide a further understanding of this application; they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of this application and, together with this specification, serve to explain the principles of this application. In the drawings: Figure 1 This is a circuit diagram of a quasi-resonant flyback converter; Figure 2 yes Figure 1 The diagram shows a timing diagram of the operation of the switching transistor Q11 in the quasi-resonant flyback converter. Figure 3 It shows Figure 1 Another timing diagram of the operation of the switch Q11 in the quasi-resonant flyback converter is shown. Figure 4 This is a circuit diagram of a switching power converter according to an embodiment of this application; Figure 5 yes Figure 4 The diagram shown represents a timing diagram of the operation of a switching power supply converter. Figure 6 yes Figure 4 Another timing diagram of the switching power supply converter is shown. Figure 7 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 8 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 9 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 10This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 11 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 12 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 13 This is a circuit diagram of a switching power converter according to another embodiment of this application; Figure 14 This is a flowchart of a control method for a switching power converter according to an embodiment of this application. Detailed Implementation

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0020] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0022] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0023] It should be understood that when a component is referred to as "on another component," "connected to another component," "coupled to another component," or "in contact with another component," it can be directly on, connected to, coupled to, or in contact with that other component, or there may be an intervening component. In contrast, when a component is referred to as "directly on another component," "directly connected to," "directly coupled to," or "directly in contact with" another component, there is no intervening component. Similarly, when a first component is referred to as "electrically contacting" or "electrically coupled to" a second component, there is an electrical path between the first and second components that allows current to flow. This electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even if there is no direct contact between the conductive components.

[0024] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0025] Figure 1 A circuit diagram of a quasi-resonant flyback converter is shown. Figure 1 As shown, the quasi-resonant flyback converter 10 includes transformer coils N11, N12, N13, and N14. The drain of the switching transistor Q11 is connected to the first terminal of the transformer coil N11, and the source of the switching transistor Q11 is grounded. The control unit 15 is used to control the gate voltage of the switching transistor Q11. The quasi-resonant flyback converter 10 is used to convert the input voltage INPUT into target output voltages OUTPUT1 and OUTPUT2.

[0026] Figure 2 It shows Figure 1 The diagram shown illustrates a timing diagram of the operation of the switching transistor Q11 in the quasi-resonant flyback converter. Figure 3 It shows Figure 1Another timing diagram showing the operation of switch Q11 in the quasi-resonant flyback converter is presented. Figure 2 and Figure 3 In the middle, V GS V is the voltage difference between the gate and source voltages of the switching transistor Q11. DS I is the drain-source voltage of the switching transistor Q11. DS This is the drain-source current of the switching transistor Q11. For example... Figure 2 and Figure 3 As shown, the quasi-resonant flyback converter 10 adopts a valley-turn-on mechanism: when GATE is low, the switch Q11 is turned off, the transformer enters the freewheeling stage, and the drain-source voltage V of the switch Q11... DS The current is pulled high until the secondary-side rectifier diodes D11 and D12 are stably turned on, ending the freewheeling phase. After the freewheeling phase ends, the system inductance and system capacitance together generate LC resonance. The system inductance includes the equivalent inductance of the transformer coils N11-N14, and the system capacitance includes the parasitic capacitances of the switching transistor Q11, diodes D11 and D12. To more clearly illustrate LC resonance, Figure 2 and Figure 3 Band S101 shows the drain-source voltage V of switch Q11 when GATE is continuously low. DS In band S101, V DS The voltage oscillates continuously with symmetrical amplitude. Control unit 15 at V DS When the oscillation reaches its lowest point, the gate is pulled high, thus turning on the switch Q11 at the bottom of the oscillation. The control unit 15 can select to turn on the switch Q11 at different resonant valleys as needed, for example... Figure 2 The gate is raised at the bottom of the first trough during LC resonance, at point 21. Figure 3 This involves raising the gate at the bottom of the second trough during LC resonance, at point 31. DS The theoretical minimum value, which is the bottom of the trough of LC resonance, is the input voltage INPUT minus the reflected voltage. The reflected voltage is obtained by superimposing two parts: one is the output voltage OUTPUT1 multiplied by the turns ratio of windings N11 and N12, and the other is the output voltage OUTPUT2 multiplied by the turns ratio of windings N11 and N13. The sum of the two is the final reflected voltage.

[0027] The above Figure 1 When transistor Q11 is turned on in the scheme, the energy stored in the system's equivalent parasitic capacitance will be directly dissipated through the conducting switch, thus resulting in residual switching losses. These switching losses can be expressed by formula (1): (1) in For switching losses, This is the circuit's equivalent parasitic capacitance. V at the turn-on time of switch Q11 DS .

[0028] Formula (1) shows that, The square value of the value is positively correlated with the switching loss.

[0029] In the above Figure 1 In the quasi-resonant flyback converter 10, Theoretically, the square value of the LC resonance is at its lowest, which is the trough of the LC resonance. If the oscillation amplitude of the LC resonance is small, A large square value will result in significant switching losses.

[0030] To reduce switching losses, this application proposes a switching power supply converter. Figure 4 , Figures 7-13 Circuit diagrams of a switching power converter according to an embodiment of this application are shown. Among them, in... Figure 4 , Figures 7-13 In the illustrated embodiment, the target windings are the second winding N621, the first winding N61, the second winding N622, the second winding N622, and the second winding N621. Figure 4 , Figures 7-13 As shown, this application proposes a switching power supply converter, comprising: a first switching transistor Q61; a transformer including a first winding N61 and a second winding N62, the first winding N61 and the first switching transistor Q61 being connected; an asymmetric resonant unit including a resonant capacitor Cr and a second switching transistor Q62, wherein a branch L1 of the resonant capacitor Cr and the second switching transistor Q62 connected in series is connected in parallel with a target winding, the target winding being any one of the first winding N61 and the second winding N62; the asymmetric resonant unit is configured such that: when the first switching transistor Q61 is turned off and the voltage of the target winding is greater than a first threshold, the second switching transistor Q61... When switch Q62 is turned on, the freewheeling current generated by the target winding charges the resonant capacitor Cr. When the first switch Q61 is turned off and the voltage of the target winding is less than the second threshold, the second switch Q62 is turned off so that the resonant capacitor Cr does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold. Control unit 65 is connected to the control terminal of the first switch Q61. Control unit 65 is configured to: when it is detected that the drain-source voltage of the first switch Q61 reaches the target threshold in the resonant trough of the system LC resonance, control the first switch Q61 to turn on so that the transformer outputs a preset voltage.

[0031] This application improves the initial resonant energy of the system by setting an asymmetric resonant unit with the transformer winding in parallel via a series branch L1, and turning on the second switch Q62 when the first switch Q61 is turned off and the target winding voltage is greater than the first threshold. The freewheeling current of the target winding charges the resonant capacitor Cr. When the target winding voltage is less than the second threshold, the second switch Q62 is turned off, and the switching power converter generates system LC resonance. The resonant capacitor does not participate in the system LC resonance. Compared to the aforementioned switching power converter without the resonant capacitor Cr, the total capacitance value of the system LC resonance remains unchanged. Since the voltage oscillation amplitude of the LC resonance is related to the resonance system... The initial resonant energy of the system is positively correlated with the voltage oscillation amplitude, while the voltage oscillation amplitude is negatively correlated with the total capacitance of the resonant system. By designing the second switch Q62 and the resonant capacitor Cr, the initial resonant energy of the system is increased without increasing the total capacitance of the LC resonant system, thus increasing the voltage oscillation amplitude of the LC resonant system. This can pull the resonant valley value of the drain-source voltage of the first switch Q61 to a lower level, thereby allowing the control unit 65 to turn on the first switch Q61 at the target threshold of the resonant valley of the LC resonant system. That is, controlling the drain-source voltage of the first switch Q61 to turn on the first switch when it is close to 0V, thereby reducing the switching losses caused by parasitic capacitance discharge.

[0032] This application does not impose specific restrictions on the types of the first switch Q61 and the second switch Q62. For example, the types of the first switch Q61 and the second switch Q62 can be any of BJT, MOSFET and IGBT.

[0033] like Figure 4 , Figures 7-13 As shown, the first switching transistor Q61 is an NMOS, with its source grounded and its drain connected to the first end of the first winding N61. The first winding N61 is located on the primary side of the transformer. The control terminal of the first switching transistor Q61 is its gate, which is connected to the control unit 65. This allows the control unit 65 to turn on the first switching transistor Q61 when the rising or falling edge of the resonant trough of the system's LC resonance reaches a target threshold. In some embodiments, the control unit 65 sets the turn-on frequency and the on-time of the first switching transistor Q61 within one turn-off cycle based on the specific output voltage of the switching power converter.

[0034] like Figure 4 , Figures 7-13 As shown, in some embodiments, the first terminal 601 of the resonant capacitor Cr is connected to the first terminal of the second switch Q62, the second terminal 602 of the resonant capacitor Cr is connected to the first terminal of the target winding and the control terminal of the second switch Q62, the control terminal of the second switch Q62 is connected to the first terminal of the target winding, and the second terminal of the second switch Q62 is connected to the second terminal of the target winding. Figure 4 , Figures 7-13 In the embodiment shown, the second switch Q62 is an NMOS transistor, the first terminal of the second switch Q62 is the source, the second terminal of the second switch Q62 is the drain, and the control terminal of the second switch Q62 is the gate.

[0035] Figure 5 It shows Figure 4 The diagram shown represents a timing diagram of the operation of a switching power supply converter. Figure 6 It shows Figure 4 The diagram shows another timing diagram of the switching power supply converter in operation. Figure 5 and Figure 6 In the middle, V GS_Q61 V represents the voltage difference between the gate and source voltages of the first switching transistor Q61. DS_Q61 I is the drain-source voltage of the first switching transistor Q61. DS_Q61 V is the drain-source current of the first switching transistor Q61. N61 V is the voltage at the first terminal of the first winding N61. N621 V is the voltage at the second terminal of winding N621. GS_Q62 V is the voltage difference between the gate and source of the second switch Q62. When the source of the second switch Q62 is grounded, V GS_Q62 That is, the gate voltage of the second switching transistor Q62. Figure 5 and Figure 6 The difference is: Figure 5 V is raised at the bottom of the first trough during the system's LC resonance, at point 71. GS_Q61 , Figure 6 This involves raising V at the bottom of the second trough during the system's LC resonance, at point 81. GS_Q61 .

[0036] This application provides a specific example to further elaborate on the operation of the switching power supply converter described herein. Figures 4-6 In the illustrated embodiment, the target winding of the transformer is winding N621. A resonant capacitor Cr and a second switching transistor Q62 are added to both ends of winding N621, generating asymmetrical resonance. In this embodiment, both the first threshold and the second threshold are 0V, but this is not a limitation. In some embodiments, the first threshold and the second threshold are not equal. Its working principle is as follows: When the first switching transistor Q61 is turned off, the voltage across winding N621 increases; when the voltage at the second end of winding N621 rises above the first threshold of 0V, the second switching transistor Q62 is turned on, and the first end of winding N621 is connected to the resonant capacitor Cr through the second switching transistor Q62. The freewheeling current in winding N621 charges the resonant capacitor Cr. After the freewheeling ends, initial LC resonance is generated in the circuit of the switching power converter, at which time the resonant capacitor Cr participates in the initial LC resonance. Figure 5 In the middle, for VDS_Q61 In terms of waveform, the initial LC resonance includes multiple peaks 72 formed above the transformer input voltage VIN with a positive amplitude; when the voltage at the first terminal of winding N621 drops back to the second threshold 0V, the second switching transistor Q62 turns off, and system LC resonance is generated in the circuit of the switching power converter. At this time, the resonant capacitor Cr does not participate in the resonance. Figure 5 In the middle, for V DS_Q61 In terms of waveform, the system LC resonance includes multiple troughs 73 formed between the negative amplitude and the transformer input voltage VIN-0V, among which trough 71 also belongs to trough 73; compared with the initial LC resonance in which the resonant capacitor Cr participates in the resonance, the resonant frequency of the system LC resonance increases and the oscillation amplitude increases, that is, the oscillation amplitude of the negative amplitude of the system LC resonance is greater than the oscillation amplitude of the positive amplitude of the initial LC resonance, thus forming an asymmetric LC resonance; when the control unit 65 detects the voltage V across the drain and source of the first switching transistor Q61... DS_Q61 When the resonance reaches the valley, i.e. the target threshold, the first switch Q61 is turned on. After the first switch Q61 is turned on, the level of the first terminal of the first winding N61 is pulled low, the two ends of the first winding N61 are turned on, the secondary winding 622 generates an induced current, and the preset voltage is output.

[0037] It should be understood that as long as the oscillation amplitude of trough 73 is large enough to make the valley voltage low enough and close to 0V, zero-voltage turn-on of the first switching transistor Q61 can be achieved, thereby significantly reducing switching losses and improving the efficiency of the switching power supply converter. Since the oscillation amplitude is inversely proportional to the total equivalent capacitance participating in the system LC resonance, the expected oscillation amplitude can be achieved by reasonably setting the value of the resonant capacitor Cr, thereby achieving zero-voltage turn-on of the first switching transistor Q61.

[0038] like Figure 4 As shown, in some embodiments, the asymmetric resonant unit is further configured such that: before the second switch is turned off and after the freewheeling is completed, the resonant capacitor Cr participates in the initial LC resonance generated by the switching power converter; the second winding 62 includes an auxiliary winding, i.e., winding N621; the transformer includes a primary side; the first winding 61 and winding N621 are respectively disposed on the primary side; the capacitance value of the resonant capacitor Cr is proportional to the first equivalent total capacitance value, the oscillation amplitude ratio, and the turns ratio, respectively. The first equivalent total capacitance value is the equivalent total capacitance value in the switching power converter 60 excluding the resonant capacitor Cr; the oscillation amplitude ratio is the ratio of the oscillation amplitude of the system LC resonance to the oscillation amplitude of the initial LC resonance; and the turns ratio is the ratio of the number of turns of the first winding to the number of turns of the auxiliary winding. Wherein, for V... N61 and V N621 In terms of the waveform, the dividing line between the initial LC resonance and the system LC resonance is 0V. Then the oscillation amplitude ratio is the ratio of the valley voltage value of the system LC resonance trough 73 to the peak voltage value of the initial LC resonance 72.

[0039] For V DS_Q61 Regarding the waveform, the boundary between the initial LC resonance and the system LC resonance is the input voltage VIN of the switching power supply converter. The oscillation amplitude ratio is: the ratio between the difference between the trough 0V of wave 73 and the input voltage VIN, i.e., the input voltage VIN, and the difference between the peak 72 and the input voltage VIN. At this time, the capacitance value of the resonant capacitor Cr can be expressed by the following formula (2): (2) Where, N A Np is the number of turns in winding N621, and V is the number of turns in winding N61. IN That is, the input voltage VIN, V RFO That is, the difference between peak 72 and input voltage VIN, C D It is the total capacitance value of the LC resonance of the system.

[0040] In some embodiments, the switching power converter further includes a voltage detector for acquiring the drain-source voltage V of the first switching transistor. DS_Q61 And send it to the control unit 65, the control unit 65 detects the drain-source voltage V of the first switching transistor Q61. DS_Q61 When the resonance reaches the target threshold, the first switch Q61 is turned on. In some embodiments, the target threshold can be set to a value close to 0V. For example, if the voltage input to the first winding 61 is about 500V, a target threshold of 1V-5V can be considered close to 0V.

[0041] like Figure 4 , Figures 9-13 As shown, in some embodiments, the switching power converter further includes a winding voltage detector 66, which is connected between the first end of the target winding and the control terminal of the second switching transistor Q62. The winding voltage detector 66 is used to turn on the second switching transistor Q62 when the voltage of the target winding is greater than a first threshold, and to turn off the second switching transistor Q62 when the voltage of the target winding is less than a second threshold. The winding voltage detector 66 turns on the second switching transistor Q62 only when the voltage is greater than the first threshold and turns it off when the voltage is less than the second threshold. This avoids damage to the second switching transistor Q62 when the voltage of the target winding is too high or instability in the second switching transistor Q62 when the voltage is too low, thus ensuring reliable conduction of the second switching transistor Q62. The first threshold is the effective turn-on threshold of the second switching transistor Q62, and the second threshold is the effective turn-off threshold of the second switching transistor Q62.

[0042] like Figure 7 As shown, in some embodiments, the switching power converter may also exclude the winding voltage detector 66 to save on cost and circuit area requirements.

[0043] like Figure 8As shown, in some embodiments, the winding voltage detector 66 can be replaced with a comparator 101 in the switching power converter. The non-inverting input of the comparator 101 is connected to the first end of the target winding and the second end 602 of the resonant capacitor Cr, respectively. The inverting input of the comparator 101 is used to input the reference voltage Vref. The output of the comparator 101 is connected to the control terminal of the second switch Q62. By replacing the winding voltage detector 66 with the comparator 101, and setting the reference voltage Vref to a first threshold or a second threshold, the second switch Q62 can be reliably turned on or off.

[0044] The non-resonant unit of this application can be selected and connected in parallel with different windings according to actual needs. The switching power converter of this application can be of various circuit topologies, including but not limited to Flyback circuits, Buck circuits, and BOOST circuits. Figure 4 , Figures 7-11 The embodiments shown are all flyback circuits. Figure 12 The embodiment shown is a BOOST circuit. Figure 13 The embodiment shown is a Buck circuit.

[0045] In some embodiments, the Flyback circuit topology may include a plurality of second windings 62. For example... Figure 4 , Figure 7 and Figure 8 As shown, in some embodiments, the second winding includes a secondary winding N622 and an auxiliary winding N621, and the target winding is the first winding N61, the secondary winding N622, or the auxiliary winding N621; the transformer includes a primary side and a secondary side, the first winding N61 and the auxiliary winding N621 are respectively disposed on the primary side, and the secondary winding N622 is disposed on the secondary side; the switching power converter includes an input terminal INPUT and an output terminal OUTPUT1, the input terminal INPUT is used to receive external power supply, and the input terminal INPUT is connected to the second end of the first winding N61; the output terminal OUTPUT1 is used to output a preset voltage, and the output terminal OUTPUT1 is connected to the secondary winding N622.

[0046] In some embodiments, the target winding is an auxiliary winding N622, and the first terminal 601 of the resonant capacitor Cr, the first terminal of the second switch Q62, and the control unit 65 share a common ground, thereby improving the convenience of integrated design.

[0047] In some embodiments, the Flyback circuit topology may include a second winding 62. For example... Figures 9-11As shown, in some embodiments, the second winding 62 includes a secondary winding N622, and the target winding is either the first winding N61 or the secondary winding N622; the transformer includes a primary side and a secondary side, with the first winding N61 disposed on the primary side and the secondary winding N622 disposed on the secondary side; the switching power converter includes an input terminal INPUT and an output terminal OUTPUT1, the input terminal INPUT is used to receive external power supply, and the input terminal INPUT is connected to the second end of the first winding N61; the output terminal OUTPUT1 is used to output a preset voltage, and the output terminal OUTPUT1 is connected to the secondary winding N622.

[0048] like Figure 12 As shown, in some embodiments, the second winding N62 includes a secondary winding N622, and the target winding is either the first winding N61 or the secondary winding N622; the transformer includes a primary side and a secondary side, with the first winding N61 disposed on the primary side and the secondary winding N622 disposed on the secondary side; the switching power converter includes an input terminal INPUT and an output terminal OUTPUT1, the input terminal INPUT is used to receive external power supply, and the input terminal INPUT is connected to the second end of the first winding N61; the output terminal OUTPUT1 is used to output a preset voltage, and the output terminal OUTPUT1 is connected to the first end of the first winding N61.

[0049] like Figure 13 As shown, in some embodiments, the second winding N62 includes an auxiliary winding N621, and the target winding is either the first winding N61 or the auxiliary winding N621; the transformer includes a primary side and a secondary side, with the first winding N61 and the auxiliary winding N621 respectively disposed on the primary side; the switching power converter includes an input terminal INPUT and an output terminal OUTPUT1, the input terminal INPUT is used to receive external power supply, and the input terminal INPUT is connected to the first end of the first winding N61; the output terminal OUTPUT1 is used to output a preset voltage, and the output terminal OUTPUT1 is connected to the first end of the first winding N61. Wherein, Figure 13 The switching power converter shown also includes a capacitor 131 and a resistor R131 connected in parallel, and the output terminal OUTPUT1 is connected in parallel across the two ends of the resistor R131.

[0050] like Figure 4 , Figures 7-9 , Figure 11As shown, in some embodiments, the switching power converter further includes: a first capacitor C61, a first resistor R1, and a first diode D61. The first capacitor C61 and the first resistor R1 are connected in parallel. The first terminals of the first capacitor R1 and the first resistor R1 are respectively connected to the first terminal of the first winding N61. The second terminals of the first capacitor R1 and the first resistor R1 are respectively connected to the cathode of the first diode D61. The anode of the first diode D61 is respectively connected to the first terminal of the first winding N61 and the first terminal of the first switching transistor Q61. The second terminal of the first switching transistor Q61 is connected to the first terminal of the first winding and is grounded. By setting the first capacitor C61, the first resistor R1, and the first diode D61, the leakage inductance energy of the transformer can be guided to the first capacitor C61, the first resistor R1, and the first diode D61 for consumption or recovery, reducing the leakage inductance energy from entering the first switching transistor Q61 in the form of voltage spikes. This allows the first switching transistor Q61 to operate under safe voltage stress, enabling the converter to operate reliably for a long time.

[0051] like Figure 10 As shown, in some embodiments, the switching power converter may omit the first capacitor C61, the first resistor R1, and the first diode D61, depending on actual cost and layout requirements.

[0052] like Figure 4 , Figures 7-11 As shown, in some embodiments, the switching power converter further includes a second diode D62 and a first polarized capacitor C62. The second winding N62 includes a secondary winding N622. The first end of the secondary winding N622 is connected to the anode of the second diode D62 and the positive terminal of the first polarized capacitor C62, respectively. The second end of the secondary winding N622 is connected to the negative terminal of the first polarized capacitor C62.

[0053] like Figure 4 , Figure 7 and Figure 8 As shown, in some embodiments, the switching power converter further includes a third diode D63 and a second capacitor C63. The second winding N62 includes an auxiliary winding N621. The first end of the auxiliary winding N621 is connected to the anode of the third diode D63, the cathode of the third diode D63 is connected to the first end of the second capacitor C63, and the second end of the second capacitor C63 is grounded.

[0054] To reduce switching losses, this application also proposes a control method for a switching power converter, applicable to the switching power converter described above. Figure 14 A flowchart illustrating a control method for a switching power converter according to an embodiment of this application is shown. Figure 14 As shown, the control method 140 includes: Step S141: When the voltage of the target winding is greater than the first threshold, the second switch is turned on, the target winding performs inductor freewheeling, and the freewheeling current of the target winding charges the resonant capacitor. Step S142: When the voltage of the target winding is less than the second threshold, turn off the second switch to prevent the resonant capacitor from participating in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold; and Step S143: When the drain-source voltage of the first switch is detected to reach the target threshold in the resonant valley of the system LC resonance, the first switch is controlled to turn on so that the transformer outputs a preset voltage.

[0055] The specific implementation of the control method 140 to reduce switching losses has been detailed in the section on switching power supply converters, and will not be repeated here.

[0056] To reduce switching losses, this application also proposes a switching power supply, including the switching power converter described above.

[0057] It should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the application requires more features than those mentioned. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0058] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used to describe embodiments are sometimes modified by the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in this application are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

Claims

1. A switching power supply converter, characterized in that, include: First switching transistor; The transformer includes a first winding and a second winding, wherein the first winding is connected to the first switching transistor; An asymmetric resonant unit includes a resonant capacitor and a second switch. A branch connecting the resonant capacitor and the second switch in series is connected in parallel with a target winding, which can be either the first winding or the second winding. The asymmetric resonant unit is configured such that: when the first switch is off and the voltage of the target winding is greater than a first threshold, the second switch is turned on, and the freewheeling current generated by the target winding charges the resonant capacitor; when the first switch is off and the voltage of the target winding is less than a second threshold, the second switch is turned off, so that the resonant capacitor does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold. The control unit is connected to the control terminal of the first switching transistor. The control unit is configured to: when the drain-source voltage of the first switching transistor is detected to reach the target threshold in the resonant valley of the LC resonance of the system, control the first switching transistor to turn on so that the transformer outputs a preset voltage.

2. The switching power supply converter as described in claim 1, characterized in that, The first end of the resonant capacitor is connected to the first end of the second switching transistor, the second end of the resonant capacitor is connected to the first end of the target winding and the control end of the second switching transistor, the control end of the second switching transistor is connected to the first end of the target winding, and the second end of the second switching transistor is connected to the second end of the target winding.

3. The switching power supply converter as described in claim 1, characterized in that, The asymmetric resonant unit is further configured such that, before the second switch is turned off and after the freewheeling is completed, the resonant capacitor participates in the initial LC resonance generated by the switching power converter. The second winding includes an auxiliary winding, and the transformer includes a primary side. The first winding and the auxiliary winding are respectively disposed on the primary side. The capacitance value of the resonant capacitor is positively correlated with the first equivalent total capacitance, the oscillation amplitude ratio, and the turns ratio. The first equivalent total capacitance is the equivalent total capacitance value of the switching power converter excluding the resonant capacitor. The oscillation amplitude ratio is the ratio of the oscillation amplitude of the system LC resonance to the oscillation amplitude of the initial LC resonance. The turns ratio is the ratio of the number of turns of the first winding to the number of turns of the auxiliary winding.

4. The switching power supply converter as described in claim 1, characterized in that, The switching power converter further includes a winding voltage detector connected between a first end of the target winding and a control terminal of the second switching transistor. The winding voltage detector is used to turn on the second switching transistor when the voltage of the target winding is greater than the first threshold, and to turn off the second switching transistor when the voltage of the target winding is less than the second threshold.

5. The switching power supply converter as described in claim 1, characterized in that, The second winding includes a secondary winding and an auxiliary winding, and the target winding is the first winding, the secondary winding, or the auxiliary winding; The transformer includes a primary side and a secondary side, with the first winding and the auxiliary winding respectively disposed on the primary side, and the secondary winding disposed on the secondary side; The switching power converter includes an input terminal and an output terminal. The input terminal is used to receive external power supply and is connected to the first winding. The output terminal is used to output the preset voltage, and the output terminal is connected to the secondary winding.

6. The switching power supply converter as described in claim 5, characterized in that, The target winding is the auxiliary winding, and the first end of the resonant capacitor, the first end of the second switching transistor, and the control unit share a common ground.

7. The switching power supply converter as described in claim 1, characterized in that, The second winding includes a secondary winding, and the target winding is either the first winding or the secondary winding; The transformer includes a primary side and a secondary side, with the first winding disposed on the primary side and the secondary winding disposed on the secondary side; The switching power converter includes an input terminal and an output terminal. The input terminal is used to receive external power supply and is connected to the first winding. The output terminal is used to output the preset voltage, and the output terminal is connected to the secondary winding.

8. The switching power supply converter as described in claim 1, characterized in that, The second winding includes a secondary winding, and the target winding is either the first winding or the secondary winding; The transformer includes a primary side and a secondary side, with the first winding disposed on the primary side and the secondary winding disposed on the secondary side; The switching power converter includes an input terminal and an output terminal. The input terminal is used to receive external power supply and is connected to the second end of the first winding. The output terminal is used to output the preset voltage, and the output terminal is connected to the first end of the first winding.

9. The switching power supply converter as described in claim 1, characterized in that, The second winding includes an auxiliary winding, and the target winding is either the first winding or the auxiliary winding; The transformer includes a primary side and a secondary side, with the first winding and the auxiliary winding respectively disposed on the primary side; The switching power converter includes an input terminal and an output terminal. The input terminal is used to receive external power supply and is connected to the first terminal of the first winding. The output terminal is used to output the preset voltage, and the output terminal is connected to the first end of the first winding.

10. The switching power supply converter as described in claim 1, characterized in that, The switching power converter further includes: a first capacitor, a first resistor, and a first diode. The first capacitor and the first resistor are connected in parallel. The first terminal of the first capacitor and the first terminal of the first resistor are respectively connected to the first terminal of the first winding. The second terminal of the first capacitor and the second terminal of the first resistor are respectively connected to the cathode of the first diode. The anode of the first diode is respectively connected to the first terminal of the first winding and the first terminal of the first switching transistor. The second terminal of the first switching transistor is connected to the first terminal of the first winding and is grounded.

11. A control method for a switching power supply converter, applicable to the switching power supply converter as described in any one of claims 1-10, characterized in that, The control method includes: When the voltage of the target winding is greater than the first threshold, the second switch is turned on, the target winding performs inductive freewheeling, and the freewheeling current of the target winding charges the resonant capacitor; When the voltage of the target winding is less than a second threshold, the second switch is turned off so that the resonant capacitor does not participate in the system LC resonance of the switching power converter, wherein the second threshold is less than or equal to the first threshold; and When the drain-source voltage of the first switch is detected to reach the target threshold in the trough of the LC resonance of the system, the first switch is controlled to turn on so that the transformer outputs a preset voltage.

12. A switching power supply, characterized in that, Including the switching power supply converter as described in any one of claims 1-10.

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