An asymmetric half-bridge flyback converter and power supply system

Abstract

This application discloses an asymmetric half-bridge flyback converter and power supply system to reduce losses and improve efficiency in the asymmetric half-bridge flyback converter. The asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first power transistor and the second power transistor are connected in series and coupled across a DC power supply. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled to the third power transistor and the secondary-side resonant capacitor.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to an asymmetric half-bridge flyback converter and power supply system. Background Technology

[0002] Currently, switching power supplies, with their advantages of high efficiency and small size, are widely used in various power systems. The asymmetrical half-bridge (AHB) converter is a typical example of a switching power supply. To achieve sufficient energy savings, the efficiency of the AHB converter in full-load or heavy-load operating modes becomes a key characteristic. Especially for half-wave rectification, the output current ripple is relatively large, increasing the losses of the AHB converter and reducing its efficiency. Summary of the Invention

[0003] This application provides an asymmetric half-bridge flyback converter and a power supply system to reduce the losses and improve the efficiency of the asymmetric half-bridge flyback converter.

[0004] To address the aforementioned technical problems, this application provides the following technical solutions:

[0005] In a first aspect, embodiments of this application provide an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor, wherein the first power transistor and the second power transistor are coupled in series to both ends of a DC power supply; the primary side of the transformer is connected in parallel to both ends of the first power transistor through the primary-side resonant capacitor, and the secondary side of the transformer is coupled to the third power transistor and the secondary-side resonant capacitor.

[0006] In this embodiment, the asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across a DC power supply. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because both the primary and secondary sides of the transformer are coupled with the primary-side and secondary-side resonant capacitors, the waveform of the current flowing through the third power transistor can be adjusted to reduce the effective value of the current flowing through it. This reduces the conduction loss of the third power transistor, lowers the losses of the asymmetric half-bridge flyback converter, and improves its efficiency.

[0007] In one possible implementation of the first aspect, the transformer includes a magnetizing inductor and a transformer leakage inductance. When the first power transistor is turned on, the primary-side resonant capacitor, the secondary-side resonant capacitor, and the transformer leakage inductance all participate in resonance, which is a hybrid resonance. In the above scheme, the first power transistor can be controlled to turn on. At this time, in the asymmetric half-bridge flyback converter, the primary-side resonant capacitor, the secondary-side resonant capacitor, and the transformer leakage inductance participate in resonance, which is a hybrid resonance. Since the secondary-side resonant capacitor is introduced into the circuit of the asymmetric half-bridge flyback converter to achieve hybrid resonance, the original resonant current waveform is effectively improved, the effective value of the current flowing through the third power transistor Q1 is reduced, the conduction loss of the third power transistor is reduced, and the efficiency of the asymmetric half-bridge flyback converter is improved.

[0008] In one possible implementation of the first aspect, the transformer includes a magnetizing inductor and a leakage inductance. When the first power transistor is turned on, the secondary resonant capacitor and the transformer leakage inductance resonate, but the primary capacitor of the transformer does not resonate. The resonance is secondary-side resonance, where the primary capacitor is the primary-side coupling capacitor of the transformer. In the above scheme, the first power transistor can be controlled to be turned on. At this time, in the circuit of the asymmetric half-bridge flyback converter, the secondary resonant capacitor and the transformer leakage inductance resonate, and the primary capacitor of the transformer does not resonate. The resonance is secondary-side resonance, where the primary capacitor is the primary-side coupling capacitor of the transformer. Although the primary capacitor is in the resonant circuit, it can be regarded as a constant voltage source. Since the secondary resonant capacitor is introduced into the circuit of the asymmetric half-bridge flyback converter to achieve secondary-side resonance, the resonant current waveform is effectively improved, the effective value of the secondary resonant current is reduced, the conduction loss of the third power transistor is reduced, and the efficiency of the asymmetric half-bridge flyback converter is improved.

[0009] In one possible implementation of the first aspect, the asymmetric half-bridge flyback converter further includes: a filter, wherein the filter is connected in parallel with the secondary-side resonant capacitor; the filter is used to reduce the ripple of the output voltage of the asymmetric half-bridge flyback converter. In the above scheme, the specific implementation of the filter further included in the asymmetric half-bridge flyback converter is not limited. The filter, connected in parallel with the secondary-side resonant capacitor, is used to reduce the ripple of the output voltage of the asymmetric half-bridge flyback converter, making the output voltage more stable. In addition, the filter is also used to reduce electromagnetic interference and improve electromagnetic compatibility characteristics.

[0010] In one possible implementation of the first aspect, the filter includes: a first inductor and a first capacitor, wherein the first inductor is used to reduce the ripple of the first capacitor; and the secondary resonant capacitor is further used to reduce the ripple of the first capacitor, thereby reducing losses due to the equivalent series resistance (ESR) of the first capacitor. In the above scheme, the first inductor and the first capacitor are connected in series, and the first inductor is used to reduce the ripple of the first capacitor. The secondary resonant capacitor is connected in parallel with the first capacitor through the first inductor, therefore the secondary resonant capacitor is also used to reduce the ripple of the first capacitor and reduce losses due to the ESR of the first capacitor. The first capacitor may specifically be an electrolytic capacitor.

[0011] In one possible implementation of the first aspect, the filter includes: a single-stage LC filter and a multi-stage LC filter. In the above scheme, the filter includes a single-stage LC filter, for example, the single-stage LC filter includes: a first inductor and a first capacitor. Alternatively, the filter may include a multi-stage LC filter, which can be considered as multiple single-stage LC filters connected in series. Through the above various filters, the ripple of the output voltage of the asymmetric half-bridge flyback converter is reduced, making the output voltage more stable.

[0012] In one possible implementation of the first aspect, the effective value of the current flowing through the third power transistor is reduced by adjusting the parameters of the hybrid resonance. In the above scheme, in the scenario where hybrid resonance is formed in the circuit of an asymmetric half-bridge flyback converter, to further reduce the effective value of the current flowing through the third power transistor, the parameters of the hybrid resonance can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor and thus reducing the conduction loss of the third power transistor. Here, the parameters of the hybrid resonance refer to the parameters forming the hybrid resonance circuit, such as adjusting the parameters of the resonant elements (transformer leakage inductance, resonant capacitor, etc.) in the hybrid resonance circuit. The parameters of the hybrid resonance can also be called the resonant circuit parameters. This application does not limit the specific process of adjusting the parameters of the hybrid resonance; for example, the method of adjusting the parameters of the hybrid resonance can be determined by combining the specific circuit forming the hybrid resonance in the asymmetric half-bridge flyback converter.

[0013] In one possible implementation of the first aspect, adjusting the parameters of the hybrid resonance includes at least one of the following: adjusting the primary-side resonant capacitor, adjusting the secondary-side resonant capacitor, and adjusting the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side; the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side is expressed as... Wherein, the C rp This represents the capacitance value of the primary-side resonant capacitor. This represents the equivalent capacitance value of the secondary-side resonant capacitor on the primary side, where C... rsThis represents the capacitance value of the secondary resonant capacitor, and N... p N represents the number of turns in the primary winding of the transformer. s This indicates the number of turns in the secondary winding of the transformer.

[0014] In the above scheme, the equivalent capacitance of the secondary-side resonant capacitor on the primary side refers to the capacitance value of the secondary-side resonant capacitor when it is equivalent to the capacitance value on the primary side. The parameters of the hybrid resonance may include: the capacitance value of the primary-side resonant capacitor, the capacitance value of the secondary-side resonant capacitor, and the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side. The ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side is expressed as: Therefore, the expression for the above ratio can be adjusted to reduce the effective value of the current flowing through the third power transistor. For example, C can be adjusted. rp Or adjust C rs Alternatively, the turns ratio of the primary and secondary windings of the transformer can be adjusted. This application embodiment does not limit the specific adjustment amount and needs to be determined based on the specific application scenario. In this application embodiment, adjusting the ratio of the hybrid resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0015] In one possible implementation of the first aspect, adjusting the parameters of the hybrid resonance includes: adjusting the initial state value of the hybrid resonance; the asymmetric half-bridge flyback converter further includes: a second capacitor, which is connected in parallel with the third power transistor; the second capacitor is used to adjust the initial state value of the hybrid resonance. In the above scheme, the initial state value of the hybrid resonance refers to the state value of the resonant elements in the initial state of the hybrid resonant circuit when the primary-side resonant capacitor, the secondary-side resonant capacitor, and the transformer leakage inductance participate in resonance to form a hybrid resonant circuit. The resonant elements include the primary-side resonant capacitor, the secondary-side resonant capacitor, and the transformer leakage inductance. For example, the initial state value of the hybrid resonance includes the initial current value of the transformer leakage inductance (i.e., the resonant inductance) and the initial voltage value of the resonant capacitor (i.e., the capacitor participating in the resonance). Therefore, adjusting the initial state value of the hybrid resonance to reduce the effective value of the current of the third power transistor, the embodiments of this application do not limit the detailed adjustment amount, which needs to be determined in combination with the specific application scenario. In this embodiment, the initial state value of the hybrid resonance is adjusted to improve the current waveform of the third power transistor, so that the effective value of the secondary winding current is as small as possible, thereby reducing the conduction loss of the third power transistor.

[0016] In one possible implementation of the first aspect, the asymmetric half-bridge flyback converter further includes: a first resistor, which is connected in series with the second capacitor; the first resistor is used to reduce the current surge and current oscillation on the third power transistor when it is turned on. In the above scheme, after the second capacitor and the first resistor are connected in series, the second capacitor and the first resistor are connected in parallel with the third power transistor. When the third power transistor is turned on, the damping effect of the first resistor on the current can reduce the current surge and current oscillation on the third power transistor. For example, the first resistor and the second capacitor form a buffer circuit, which is connected in parallel with the third power transistor. By adding a buffer circuit, electromagnetic compatibility can be improved.

[0017] In one possible implementation of the first aspect, the effective value of the current flowing through the third power transistor is reduced by adjusting the parameters of the secondary-side resonance. In the above scheme, in the scenario where secondary-side resonance is formed in the circuit of an asymmetric half-bridge flyback converter, to further reduce the effective value of the current flowing through the third power transistor, the parameters of the secondary-side resonance can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor and thus reducing the conduction loss of the third power transistor. Here, the parameters of the secondary-side resonance refer to the parameters forming the secondary-side resonant circuit, such as adjusting the parameters of the resonant elements (transformer leakage inductance, secondary-side resonant capacitor, etc.) in the secondary-side resonant circuit. The parameters of the secondary-side resonance can also be called the secondary-side resonant circuit parameters. This application does not limit the specific process of adjusting the secondary-side resonance parameters; for example, the method of adjusting the secondary-side resonance parameters can be determined by combining the specific secondary-side resonant circuit formed in the asymmetric half-bridge flyback converter.

[0018] In one possible implementation of the first aspect, adjusting the parameters of the secondary resonant circuit includes adjusting the secondary resonant capacitor. In the above scheme, the capacitance value of the secondary resonant capacitor can be adjusted. This application embodiment does not limit the specific adjustment amount, which needs to be determined based on the specific application scenario. In this application embodiment, adjusting the secondary resonant capacitor improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0019] In one possible implementation of the first aspect, adjusting the parameters of the secondary-side resonance includes: adjusting the initial state value of the resonant element of the secondary-side resonance; the asymmetric half-bridge flyback converter further includes: a second capacitor, which is connected in parallel with the third power transistor; the second capacitor is used to adjust the initial state value of the secondary-side resonance. In the above scheme, the initial state value of the secondary-side resonance refers to the state value of the resonant element when the secondary-side resonant capacitor and the transformer leakage inductance participate in resonance to form a secondary-side resonant circuit, and the resonant element includes the secondary-side resonant capacitor and the transformer leakage inductance. For example, the initial state value of the secondary-side resonance includes the initial current value of the transformer leakage inductance (i.e., the resonant inductance) and the initial voltage value of the resonant capacitor (i.e., the capacitor participating in the resonance). Therefore, adjusting the initial state value of the secondary-side resonance to reduce the effective value of the current of the third power transistor, the embodiments of this application do not limit the detailed adjustment amount, which needs to be determined in combination with the specific application scenario. In this embodiment, the initial state value of the secondary resonance is adjusted to improve the current waveform of the third power transistor, so that the effective value of the secondary winding current is as small as possible, thereby reducing the conduction loss of the third power transistor.

[0020] In one possible implementation of the first aspect, the first power transistor is the upper transistor and the second power transistor is the lower transistor; or, the first power transistor is the lower transistor and the second power transistor is the upper transistor. In the above scheme, the first power transistor is the upper transistor and the second power transistor is the lower transistor, that is, the primary side of the transformer is connected in parallel across the two ends of the upper transistor. In this case, the asymmetric half-bridge flyback switch converter is an asymmetric half-bridge flyback switch converter with the transformer connected to the upper half-bridge arm. Alternatively, the first power transistor is the lower transistor and the second power transistor is the upper transistor. That is, the primary side of the transformer is connected in parallel across the two ends of the lower power transistor. In this case, the asymmetric half-bridge flyback switch converter is an asymmetric half-bridge flyback switch converter with the transformer connected to the lower half-bridge arm.

[0021] In one possible implementation of the first aspect, the third power transistor includes at least one of the following: a synchronous rectifier and a diode. In the above scheme, for example, the third power transistor is a synchronous rectifier, which performs a rectification function. When the secondary output voltage of the transformer remains constant, in this embodiment, the synchronous rectifier and the secondary resonant capacitor are connected in series. Through the cooperation of the primary and secondary resonant capacitors in the asymmetric half-bridge flyback converter, the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor, and thus reducing the conduction loss of the synchronous rectifier. Alternatively, the synchronous rectifier can be replaced by a diode to perform the rectification function. Through the cooperation of the primary and secondary resonant capacitors in the asymmetric half-bridge flyback converter, the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can be adjusted, thereby reducing the effective value of the current flowing through the diode, and also reducing the conduction loss of the diode.

[0022] Secondly, embodiments of this application also provide a power supply system, including: a DC power supply and an asymmetric half-bridge flyback converter as described in any of the first aspects above, wherein the input terminal of the asymmetric half-bridge flyback converter is coupled to the DC power supply.

[0023] In the second aspect of this application, the components of the power supply system may be the structures described in the first aspect and various possible implementations, as detailed in the foregoing description of the first aspect and various possible implementations.

[0024] Thirdly, embodiments of this application provide an asymmetric half-bridge converter, the asymmetric half-bridge converter comprising: an asymmetric half-bridge flyback converter as described in any one of the first aspects above; or, the asymmetric half-bridge converter comprising: an asymmetric half-bridge forward converter, wherein the connection method of the same-name terminal of the transformer in the asymmetric half-bridge forward converter is opposite to that of the same-name terminal of the transformer in the asymmetric half-bridge flyback converter; the asymmetric half-bridge forward converter comprises: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor, wherein the first power transistor and the second power transistor are coupled in series to both ends of a DC power supply; the primary side of the transformer is connected in parallel to both ends of the first power transistor through the primary-side resonant capacitor, and the secondary side of the transformer is coupled to the third power transistor and the secondary-side resonant capacitor.

[0025] In this embodiment, the asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across a DC power supply. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because both the primary and secondary sides of the transformer are coupled with the primary-side and secondary-side resonant capacitors, the waveform of the current flowing through the third power transistor can be adjusted to reduce the effective value of the current flowing through it. This reduces the conduction loss of the third power transistor, lowers the losses of the asymmetric half-bridge flyback converter, and improves its efficiency.

[0026] In this embodiment, the asymmetric half-bridge forward converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across a DC power supply. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because the primary and secondary sides of the transformer are coupled with the primary-side resonant capacitor, the waveform of the current flowing through the third power transistor can be adjusted by their interaction, thereby reducing the effective value of the current flowing through the third power transistor. This reduces the conduction loss of the third power transistor, lowers the losses of the asymmetric half-bridge forward converter, and improves its efficiency.

[0027] Fourthly, embodiments of this application also provide a power supply system, including: a DC power supply and an asymmetric half-bridge converter as described in the third aspect above, wherein...

[0028] The input terminal of the asymmetric half-bridge converter is coupled to the DC power supply.

[0029] In the fourth aspect of this application, the components of the power supply system may be the structures described in the third aspect and various possible implementations above, as detailed in the foregoing description of the third aspect and various possible implementations. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the composition structure of an asymmetric half-bridge converter provided in an embodiment of this application;

[0031] Figure 2 A circuit diagram of an asymmetric half-bridge forward converter provided in this application embodiment;

[0032] Figure 3 A circuit diagram of an asymmetric half-bridge flyback converter provided in this application embodiment;

[0033] Figure 4 A circuit diagram of an asymmetric half-bridge flyback converter provided in this application embodiment;

[0034] Figure 5 A circuit diagram of an asymmetric half-bridge flyback converter provided in this application embodiment;

[0035] Figure 6 An equivalent circuit diagram of the hybrid resonance circuit provided in the embodiments of this application;

[0036] Figure 7 This is a schematic diagram of the current variation of an asymmetric half-bridge flyback converter provided in an embodiment of this application;

[0037] Figure 8 A schematic diagram showing the primary-side current change of only the primary-side resonant capacitor is provided for the embodiments of this application;

[0038] Figure 9 A schematic diagram showing the primary current variation of only the secondary resonant capacitor is provided for the embodiments of this application;

[0039] Figure 10 A schematic diagram of the primary-side current variation when the primary-side resonant capacitor and the secondary-side resonant capacitor form a hybrid resonance, as provided in the embodiments of this application;

[0040] Figure 11 This is a schematic diagram of the composition structure of a power supply system provided in an embodiment of this application. Detailed Implementation

[0041] The embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0042] This application provides an asymmetrical half-bridge (AHB) flyback converter, also known as an asymmetrical half-bridge flyback converter. The asymmetrical half-bridge flyback converter combines the advantages of both asymmetrical half-bridge and flyback converters, featuring simple structure, low cost, and high efficiency. It can be applied to power systems, such as power adapters, lithium battery chargers, communication power supplies, and server power supplies.

[0043] This application also provides a direct-current / direct-current converter (DC / DC). The DC / DC converter in this application may include, but is not limited to, an asymmetric half-bridge flyback converter, an asymmetric half-bridge forward converter, an LLC resonant converter, etc.

[0044] An embodiment of this application provides an asymmetric half-bridge converter, comprising: an asymmetric half-bridge flyback converter; or...

[0045] The asymmetric half-bridge converter includes: an asymmetric half-bridge forward converter.

[0046] The connection method of the same-name terminal of the transformer in the asymmetric half-bridge forward converter is opposite to that of the same-name terminal of the transformer in the asymmetric half-bridge flyback converter.

[0047] For example Figure 1As shown, the asymmetric half-bridge converter includes: an asymmetric half-bridge forward converter, which includes: a first power transistor 101, a second power transistor 102, a primary-side resonant capacitor 103, a transformer 104, a third power transistor 105, and a secondary-side resonant capacitor 106, wherein...

[0048] The first power transistor 101 and the second power transistor 102 are connected in series and coupled to both ends of the DC power supply;

[0049] The primary side of transformer 104 is connected in parallel across the first power transistor 101 via the primary resonant capacitor 103. The secondary side of transformer 104 is coupled with the third power transistor 105 and the secondary resonant capacitor 106.

[0050] This application also provides an asymmetric half-bridge converter, which may include, but is not limited to, an asymmetric half-bridge flyback converter and an asymmetric half-bridge forward converter.

[0051] like Figure 2 The diagram shown is a circuit diagram of an asymmetric half-bridge forward converter. The asymmetric half-bridge forward converter includes: a first power transistor Q. L The second power transistor Q H Primary resonant capacitor C rp Transformer leakage inductance L r Magnetizing inductance L m The third power transistor Q1, and the secondary resonant capacitor C rs .in,

[0052] First power transistor Q L With the second power transistor Q H After being connected in series, it is coupled to the DC power supply V. in The two ends;

[0053] The primary side of the transformer is connected to the primary resonant capacitor C. rp Parallel connection to the first power transistor Q L At both ends, the secondary side of the transformer is coupled with the third power transistor Q1 and the secondary resonant capacitor C. rs .For example, Figure 2 The example uses the third power transistor Q1 as the synchronous rectifier SR.

[0054] For example, an asymmetric half-bridge forward converter includes a transformer, wherein one side of the primary side of the transformer, for example the upper side, and the other side of the secondary side of the transformer, for example the upper side, are terminals of the same name, or the other side of the primary side of the transformer, for example the lower side, and one side of the secondary side of the transformer, for example the lower side, are terminals of the same name.

[0055] In subsequent embodiments, the asymmetric half-bridge converter will be specifically described as an asymmetric half-bridge flyback converter, such as... Figure 1As shown in the figure, an asymmetric half-bridge flyback converter provided in this application includes: a first power transistor 101, a second power transistor 102, a primary-side resonant capacitor 103, a transformer 104, a third power transistor 105, and a secondary-side resonant capacitor 106, wherein,

[0056] The first power transistor 101 and the second power transistor 102 are connected in series and coupled to both ends of the DC power supply;

[0057] The primary side of transformer 104 is connected in parallel across the first power transistor 101 via the primary resonant capacitor 103. The secondary side of transformer 104 is coupled with the third power transistor 105 and the secondary resonant capacitor 106.

[0058] It should be noted that the "coupling" described in this application refers to a direct or indirect connection. For example, coupling between A and B can mean that A and B are connected, which can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thus enabling A and B to be connected through C.

[0059] An asymmetric half-bridge flyback converter includes multiple power transistors, which can be power semiconductor devices. The power transistors are distributed in different positions within the converter, and the other devices they are connected to also differ. For example, an asymmetric half-bridge flyback converter may include three power transistors: a first power transistor 101, a second power transistor 102, and a third power transistor 105. The first and second power transistors 101 and 102 can be switching transistors. They are connected in series and coupled across a DC power supply. The first and second power transistors 101 and 102 can be switched on and off under the control of a controller, which can be connected to the asymmetric half-bridge flyback converter.

[0060] The first power transistor 101 and the second power transistor 102 are connected in series, and then the first power transistor 101 and the second power transistor 102 are respectively connected to the transformer 104, as follows. Figure 1 As shown, transformer 104 and primary-side resonant capacitor 103 are connected in series and then in parallel across the first power transistor 101; alternatively, transformer 104 and primary-side resonant capacitor 103 are connected in series and then in parallel across the second power transistor 102. Subsequent figures will illustrate this with the example of transformer 104 and primary-side resonant capacitor 103 connected in series and then in parallel across the first power transistor 101. Both the first power transistor 101 and the second power transistor 102 can be switching transistors; for example, the first power transistor 101 can be the first switching transistor, and the second power transistor 102 can be the second switching transistor. Figure 3 The example uses the first switch as the upper switch and the second switch as the lower switch.

[0061] The embodiments of this application use metal-oxide-semiconductor field-effect transistors (MOSFETs) as examples for illustration. It should be understood that the switching transistors can also be other semiconductor devices such as insulated-gate bipolar transistors (IGBTs).

[0062] In addition to the first power transistor 101 and the second power transistor 102, the asymmetric half-bridge flyback converter provided in this application embodiment may include a third power transistor 105. This third power transistor 105 may be part of a rectifier circuit, which may include the third power transistor 105 and a secondary resonant capacitor 106. The third power transistor 105 and the secondary resonant capacitor 106 are coupled to the secondary side of the transformer 104, for example, the third power transistor 105 and the secondary resonant capacitor 106 are connected in series and then in parallel to the secondary side of the transformer 104.

[0063] The third power transistor 105 acts as a rectifier in the asymmetric half-bridge flyback converter. As the power of the asymmetric half-bridge flyback converter increases, the difference between the effective value and the average value of the current flowing through the third power transistor increases further when the secondary output voltage of the transformer remains constant. The larger this difference, the greater the conduction loss of the third power transistor. The average value of the current flowing through the third power transistor is determined by the DC load, but adjusting the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can reduce the effective value of the current, thereby reducing the conduction loss of the third power transistor. In this embodiment, the third power transistor 105 and the secondary resonant capacitor 106 are connected in series. By coordinating the primary resonant capacitor 103 and the secondary resonant capacitor 106 in the asymmetric half-bridge flyback converter, the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor, and thus reducing the conduction loss of the third power transistor.

[0064] In some embodiments of this application, the third power transistor includes at least one of the following: a synchronous rectifier (SR) and a diode. For example, the third power transistor is a synchronous rectifier, which performs rectification. When the secondary output voltage of the transformer remains constant, in this embodiment, the synchronous rectifier and the secondary resonant capacitor 106 are connected in series. Through the cooperation of the primary resonant capacitor 103 and the secondary resonant capacitor 106 in the asymmetric half-bridge flyback converter, the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor, and thus reducing the conduction loss of the synchronous rectifier. Alternatively, the synchronous rectifier can be replaced by a diode to perform the rectification function. Through the cooperation of the primary resonant capacitor 103 and the secondary resonant capacitor 106 in the asymmetric half-bridge flyback converter, the control parameters and circuit parameters of the asymmetric half-bridge flyback converter can be adjusted, thereby reducing the effective value of the current flowing through the diode, and also reducing the conduction loss of the diode.

[0065] In this embodiment, the transformer includes a magnetizing inductance and a leakage inductance. It is understood that the magnetizing inductance, leakage inductance, and ideal transformer can be specifically implemented as an actual transformer. The transformer has a primary winding and a secondary winding, and the primary-to-secondary turns ratio of the transformer can be expressed as N. p / N s N p N represents the number of turns in the primary winding of a transformer. s This indicates the number of turns in the secondary winding of the transformer, where " / " is the division symbol. Additionally, N... p / N s It can also be represented as N P :N S , ":" is the division symbol.

[0066] In this embodiment, the asymmetric half-bridge flyback converter includes at least two capacitors. At least one of these two capacitors is used to form a resonant circuit with the leakage inductance of the transformer. Based on the positional relationship between the at least two capacitors and the transformer, they can be divided into primary-side capacitors and secondary-side capacitors. When a capacitor participates in resonance, it can also be called a "resonant capacitor." For example, when the primary-side capacitor participates in resonance, it can also be called a "primary-side resonant capacitor," and when the secondary-side capacitor participates in resonance, it can also be called a "secondary-side resonant capacitor."

[0067] The asymmetric half-bridge flyback converter provided in this application includes both a primary-side resonant capacitor and a secondary-side resonant capacitor. The secondary side of the transformer is coupled with a third power transistor and a secondary-side resonant capacitor, which are connected in series. By adjusting the parameters of the resonant circuit including the primary-side and secondary-side resonant capacitors, the current waveform of the third power transistor is made closer to the average value of the secondary winding current, and the effective value of the current of the third power transistor is closer to the average value of the secondary winding current, thereby reducing the conduction loss of the third power transistor.

[0068] The aforementioned DC power supply connects the first power transistor and the second power transistor. For example, the DC power supply can be an energy storage battery (such as a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-ion battery, a lithium polymer battery, etc.), a solar cell, an AC / DC converter (alternating current / direct-current converter), or other DC / DC converters (such as a BUCK converter, a BOOST converter, a BUCK-BOOST converter, etc.).

[0069] In the asymmetric half-bridge flyback converter provided in this application embodiment, after the secondary side of the transformer 104 couples the third power transistor 105 and the secondary side resonant capacitor 106, it can also couple a DC load, such as a resistor, a mobile terminal, an energy storage battery, other DC / DC converters and / or DC / AC converters (direct-current / alternating current converters), etc.

[0070] like Figure 3 The diagram shown is a circuit diagram of an asymmetric half-bridge flyback converter. The asymmetric half-bridge flyback converter includes: a first power transistor Q. L The second power transistor Q H Primary resonant capacitor C rp Transformer leakage inductance L r Magnetizing inductance L m The third power transistor Q1, and the secondary resonant capacitor C rs .in,

[0071] First power transistor Q L With the second power transistor Q H After being connected in series, it is coupled to the DC power supply V. in The two ends;

[0072] The primary side of the transformer is connected to the primary resonant capacitor C. rp Parallel connection to the first power transistor Q L At both ends, the secondary side of the transformer is coupled with the third power transistor Q1 and the secondary resonant capacitor C. rs .For example, Figure 3The example uses the third power transistor Q1 as the synchronous rectifier SR.

[0073] Figure 3 The first power transistor is used as the first switching transistor Q. L The second power transistor is the second switching transistor Q. H The third power transistor, Q1, is used as an example of a synchronous rectifier. Additionally, N... p :N s The transformer's primary and secondary turns ratio, V0 represents the output voltage, I0 represents the output current, and R... L This represents the load. It is understandable that the magnetizing inductance, transformer leakage inductance, and ideal transformer can be concretely implemented as a single, actual transformer.

[0074] It should be noted that, Figure 3 The example shown uses the connection of the third power transistor Q1 to the positive terminal of the secondary resonant capacitor. However, it is not limited to this example. The third power transistor Q1 can also be connected to the negative terminal of the secondary resonant capacitor. No further illustration is provided here. The connection method between the third power transistor Q1 and the secondary resonant capacitor is not limited.

[0075] The first and second switching transistors are connected in series and coupled to the DC power supply V. in The two ends of the transistor are coupled, namely the drain of the first switching transistor and the source of the second switching transistor, and the drain of the second switching transistor is coupled to the DC power supply V. in The positive terminal of the first switching transistor is coupled to the DC power supply V. in The negative terminal. Optional, DC power supply V in A filter capacitor C is connected in parallel across its two ends. in The primary winding of the transformer is connected in parallel across the first switching transistor via a primary resonant capacitor. For example, the drain of the first switching transistor is coupled to one end of the primary resonant capacitor, the other end of the primary resonant capacitor is coupled to one side of the transformer's primary winding, and the other side of the transformer's primary winding is coupled to the source of the first switching transistor. The secondary winding of the transformer is coupled to a DC load. For example, one side of the transformer's secondary winding is coupled to the source of a third power transistor Q1, the drain of the third power transistor Q1 is coupled to one end of the secondary resonant capacitor and one end of the load, and the other end of the secondary resonant capacitor and the other end of the load are coupled to the other side of the transformer's secondary winding. For example, one side of the transformer's primary winding, for example, the upper side, and the other side of the transformer's secondary winding, for example, the lower side, and the other side of the transformer's primary winding, for example, the upper side, are terminals of the same name, or vice versa.

[0076] Understandable, Figure 3 The example uses a load resistor to represent a DC load; however, this application does not limit the DC load coupled to the asymmetric half-bridge flyback converter. Furthermore, Figure 3 The third power transistor Q1 shown can be replaced by a diode to achieve the rectification function.

[0077] In some embodiments of this application, the transformer includes: a magnetizing inductor and a transformer leakage inductance.

[0078] When the first power transistor is turned on, the primary resonant capacitor, the secondary resonant capacitor, and the transformer leakage inductance participate in the resonance, which is a hybrid resonance.

[0079] In this circuit, the first power transistor can be controlled to turn on. At this point, in the asymmetric half-bridge flyback converter, the primary-side resonant capacitor, the secondary-side resonant capacitor, and the transformer leakage inductance all participate in resonance, resulting in a hybrid resonance. Because the secondary-side resonant capacitor is introduced into the circuit of the asymmetric half-bridge flyback converter to achieve hybrid resonance, the original resonant current waveform is effectively improved, the effective value of the current flowing through the third power transistor Q1 is reduced, the conduction loss of the third power transistor is reduced, and the efficiency of the asymmetric half-bridge flyback converter is improved.

[0080] In some embodiments of this application, the transformer includes: a magnetizing inductor and a transformer leakage inductance.

[0081] When the first power transistor is turned on, the secondary resonant capacitor and the transformer leakage inductance participate in the resonance, but the primary capacitor of the transformer does not participate in the resonance. This resonance is the secondary resonance, where the primary capacitor is the primary coupling capacitor of the transformer.

[0082] In this circuit, the first power transistor can be controlled to turn on. At this point, in the asymmetric half-bridge flyback converter circuit, the secondary-side resonant capacitor and the transformer leakage inductance participate in resonance, while the primary-side capacitor of the transformer does not participate in resonance. The resonance is secondary-side resonance. The primary-side capacitor is the primary-side coupling capacitor of the transformer. Although the primary-side capacitor is in the resonant circuit, it can be considered a constant voltage source. By introducing a secondary-side resonant capacitor to achieve secondary-side resonance in the asymmetric half-bridge flyback converter circuit, the resonant current waveform is effectively improved, the effective value of the secondary-side resonant current is reduced, the conduction loss of the third power transistor is reduced, and the efficiency of the asymmetric half-bridge flyback converter is improved.

[0083] In some embodiments of this application, the transformer includes: a magnetizing inductor and a transformer leakage inductance.

[0084] When the first power transistor is turned on, the primary resonant capacitor and the transformer leakage inductance participate in the resonance, but the secondary capacitor of the transformer does not participate in the resonance, and the resonance is the primary resonance; where the secondary capacitor is the capacitor coupled to the secondary side of the transformer.

[0085] In this circuit, the first power transistor can be controlled to turn on. At this point, in the asymmetric half-bridge flyback converter circuit, the primary-side resonant capacitor and the transformer leakage inductance participate in resonance, while the secondary-side capacitor of the transformer does not participate in resonance. This resonance is primary-side resonance. Although the secondary-side capacitor is in the resonant circuit, it can be considered a constant voltage source. The secondary-side capacitor is the capacitor coupled to the secondary side of the transformer.

[0086] In some embodiments of this application, the parameters of the hybrid resonance are adjusted to reduce the effective value of the current flowing through the third power transistor.

[0087] In a scenario where a hybrid resonance is formed in the circuit of an asymmetric half-bridge flyback converter, to further reduce the effective value of the current flowing through the third power transistor, the parameters of the hybrid resonance can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor and thus reducing its conduction loss. The parameters of the hybrid resonance refer to the parameters that form the hybrid resonant circuit, such as adjusting the parameters of the resonant elements (transformer leakage inductance, resonant capacitor, etc.) in the hybrid resonant circuit. The parameters of the hybrid resonance can also be called the resonant circuit parameters. This application does not limit the specific process of adjusting the hybrid resonance parameters; for example, the method of adjusting the hybrid resonance parameters can be determined by considering the specific circuit forming the hybrid resonance in the asymmetric half-bridge flyback converter.

[0088] In some embodiments of this application, adjusting the parameters of the hybrid resonance includes at least one of the following: adjusting the primary-side resonant capacitor, adjusting the secondary-side resonant capacitor, and adjusting the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side.

[0089] The ratio of the capacitance of the primary-side resonant capacitor to the equivalent capacitance of the secondary-side resonant capacitor on the primary side is expressed as:

[0090] Among them, C rp This represents the capacitance value of the primary-side resonant capacitor. C represents the equivalent capacitance of the secondary-side resonant capacitor on the primary side. rs N represents the capacitance value of the secondary resonant capacitor. p N represents the number of turns in the primary winding of a transformer. s This indicates the number of turns in the secondary winding of the transformer.

[0091] Specifically, the equivalent capacitance of the secondary-side resonant capacitor on the primary side refers to the capacitance value of the secondary-side resonant capacitor when it is equivalent to the capacitance value on the primary side. Parameters of hybrid resonance may include: the capacitance value of the primary-side resonant capacitor, the capacitance value of the secondary-side resonant capacitor, and the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side.

[0092] The ratio of the capacitance of the primary-side resonant capacitor to the equivalent capacitance of the secondary-side resonant capacitor on the primary side is expressed as: Therefore, the expression for the above ratio can be adjusted to reduce the effective value of the current flowing through the third power transistor. For example, C can be adjusted. rp Or adjust C rsAlternatively, the turns ratio of the primary and secondary windings of the transformer can be adjusted. This application embodiment does not limit the specific adjustment amount and needs to be determined based on the specific application scenario. In this application embodiment, adjusting the ratio of the hybrid resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0093] In some embodiments of this application, adjusting the parameters of the hybrid resonance includes adjusting the initial state value of the hybrid resonance.

[0094] The initial state value of hybrid resonance refers to the state value of the resonant elements in the hybrid resonant circuit when the primary-side resonant capacitor, secondary-side resonant capacitor, and transformer leakage inductance participate in resonance to form a hybrid resonant circuit. The resonant elements include the primary-side resonant capacitor, secondary-side resonant capacitor, and transformer leakage inductance. For example, the initial state value of hybrid resonance includes the initial current value of the transformer leakage inductance (i.e., the resonant inductor) and the initial voltage value of the resonant capacitor (i.e., the capacitor participating in resonance). Therefore, adjusting the initial state value of hybrid resonance reduces the effective value of the current of the third power transistor. This application embodiment does not limit the specific adjustment amount and needs to determine it based on the specific application scenario. In this application embodiment, adjusting the initial state value of hybrid resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0095] Specifically, adjusting the initial state value of the hybrid resonance can be achieved by changing the capacitance of the second capacitor. For example, an asymmetric half-bridge flyback converter also includes a second capacitor connected in parallel with a third power transistor; the second capacitor is used to adjust the initial state value of the hybrid resonance. For example, the second capacitor could be C in the subsequent illustration. b .

[0096] In this embodiment, the second capacitor is connected in parallel with the third power transistor. For example, the second capacitor can be a ceramic capacitor. By changing the capacitance value of the second capacitor, the initial state value of the hybrid resonance can be adjusted. In this embodiment, adjusting the initial state value of the hybrid resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thereby reducing the conduction loss of the third power transistor.

[0097] In some embodiments of this application, the effective value of the current flowing through the third power transistor is reduced by adjusting the parameters of the secondary resonant circuit.

[0098] In a scenario where secondary-side resonance is formed in an asymmetric half-bridge flyback converter circuit, to further reduce the effective value of the current flowing through the third power transistor, the parameters of the secondary-side resonance can be adjusted, thereby reducing the effective value of the current flowing through the third power transistor and thus reducing its conduction losses. The parameters of the secondary-side resonance refer to the parameters that form the secondary-side resonant circuit, such as adjusting the parameters of the resonant elements (transformer leakage inductance, secondary-side resonant capacitor, etc.) in the secondary-side resonant circuit. The parameters of the secondary-side resonance can also be called the secondary-side resonant circuit parameters. This application does not limit the specific process of adjusting the secondary-side resonance parameters; for example, the method of adjusting the secondary-side resonance parameters can be determined by considering the specific secondary-side resonant circuit formed in the asymmetric half-bridge flyback converter.

[0099] In some embodiments of this application, adjusting the parameters of the secondary resonant includes adjusting the secondary resonant capacitor.

[0100] The capacitance value of the secondary resonant capacitor can be adjusted. This application embodiment does not limit the specific adjustment amount, which needs to be determined based on the specific application scenario. In this application embodiment, adjusting the secondary resonant capacitor improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0101] In some embodiments of this application, adjusting the parameters of the secondary resonance includes: adjusting the initial state value of the resonant element of the secondary resonance;

[0102] The asymmetric half-bridge flyback converter also includes: a second capacitor, and the second capacitor and the third power transistor are connected in parallel;

[0103] The second capacitor is used to adjust the initial state value of the secondary side resonance.

[0104] The initial state value of the secondary-side resonance refers to the state value of the resonant elements when the secondary-side resonant capacitor and the transformer leakage inductance participate in resonance to form a secondary-side resonant circuit. The resonant elements include the secondary-side resonant capacitor and the transformer leakage inductance. For example, the initial state value of the secondary-side resonance includes the initial current value of the transformer leakage inductance (i.e., the resonant inductance) and the initial voltage value of the resonant capacitor (i.e., the capacitor participating in the resonance). Therefore, adjusting the initial state value of the secondary-side resonance reduces the effective value of the current of the third power transistor. This application embodiment does not limit the specific adjustment amount and needs to determine it based on the specific application scenario. In this application embodiment, adjusting the initial state value of the secondary-side resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thus reducing the conduction loss of the third power transistor.

[0105] Specifically, adjusting the initial state value of the secondary-side resonance can be achieved by changing the capacitance of the second capacitor. For example, an asymmetric half-bridge flyback converter also includes a second capacitor, which is connected in parallel with the third power transistor; the second capacitor is used to adjust the initial state value of the secondary-side resonance. For example, the second capacitor can be C in the subsequent illustration. b .

[0106] In this embodiment, the second capacitor is connected in parallel with the third power transistor. For example, the second capacitor can be a ceramic capacitor. By changing the capacitance value of the second capacitor, the initial state value of the secondary resonance can be adjusted. In this embodiment, adjusting the initial state value of the secondary resonance improves the current waveform of the third power transistor, making the effective value of the secondary winding current as small as possible, thereby reducing the conduction loss of the third power transistor.

[0107] Furthermore, in the scenario where the second capacitor is connected in parallel with the third power transistor, the asymmetric half-bridge flyback converter also includes: a first resistor, and the first resistor and the second capacitor are connected in series.

[0108] The first resistor is used to reduce the current surge to the third power transistor and reduce current oscillation when the third power transistor is turned on.

[0109] In this circuit, the second capacitor and the first resistor are connected in series, and then connected in parallel with the third power transistor. When the third power transistor is turned on, the damping effect of the first resistor reduces the current surge and oscillations. For example, the first resistor and the second capacitor form a buffer circuit, which is connected in parallel with the third power transistor. Adding this buffer circuit improves electromagnetic compatibility (EMC). For example, the first resistor could be R as shown in the subsequent diagram. b .

[0110] In some embodiments of this application, the asymmetric half-bridge flyback converter further includes: a filter, wherein,

[0111] The filter is connected in parallel with the secondary resonant capacitor;

[0112] A filter is used to reduce the ripple of the output voltage of an asymmetric half-bridge flyback converter.

[0113] The specific implementation of the filter included in the asymmetric half-bridge flyback converter is not limited. This filter is connected in parallel with the secondary resonant capacitor and is used to reduce the ripple of the output voltage of the asymmetric half-bridge flyback converter, making the output voltage more stable. In addition, this filter also reduces electromagnetic interference and improves electromagnetic compatibility characteristics.

[0114] In some embodiments of this application, the filter includes: a first inductor and a first capacitor.

[0115] The first inductor is used to reduce the ripple of the first capacitor;

[0116] The secondary resonant capacitor is also used to reduce the ripple of the first capacitor and reduce the losses caused by the equivalent series resistance (ESR) of the first capacitor.

[0117] In this configuration, the first inductor and the first capacitor are connected in series, with the first inductor used to reduce the ripple of the first capacitor. The secondary resonant capacitor is connected in parallel with the first capacitor through the first inductor; therefore, the secondary resonant capacitor also helps reduce the ripple of the first capacitor and the losses caused by the ESR of the first capacitor. For example, the first capacitor could be C0 in a later illustration, and the first inductor could be L in a later illustration. f The first capacitor may specifically be an electrolytic capacitor, but the implementation method of the first capacitor is not limited in the embodiments of this application.

[0118] Furthermore, in some embodiments of this application, the filter includes: a single-stage LC filter and a multi-stage LC filter.

[0119] Specifically, the filter includes a single-stage LC filter, which may include, for example, a first inductor and a first capacitor. Alternatively, the filter may include a multi-stage LC filter, which can be considered as multiple single-stage LC filters connected in series. Through these various filters, the ripple of the output voltage of the asymmetric half-bridge flyback converter is reduced, resulting in a more stable output voltage.

[0120] In some embodiments of this application, the first power transistor is the upper transistor, and the second power transistor is the lower transistor, meaning the primary winding of the transformer is connected in parallel across the two ends of the upper transistor. In this case, the asymmetric half-bridge flyback switch converter is an asymmetric half-bridge flyback switch converter with the transformer connected to the upper half-bridge arm. Alternatively, the first power transistor is the lower transistor, and the second power transistor is the upper transistor. That is, the primary winding of the transformer is connected in parallel across the two ends of the lower power transistor. In this case, the asymmetric half-bridge flyback switch converter is an asymmetric half-bridge flyback switch converter with the transformer connected to the lower half-bridge arm.

[0121] As illustrated by the foregoing examples of the embodiments in this application, the asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across the two ends of a DC power supply. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because the primary side of the transformer is coupled with the primary-side resonant capacitor, and the secondary side is coupled with the secondary-side resonant capacitor, the current waveform flowing through the third power transistor can be adjusted through their cooperation. This reduces the effective value of the current flowing through the third power transistor, thereby reducing its conduction losses and improving the efficiency of the asymmetric half-bridge flyback converter.

[0122] The embodiments of this application will be illustrated with detailed application scenarios below.

[0123] like Figure 4 The diagram shown is a circuit diagram of an asymmetric half-bridge flyback converter provided in an embodiment of this application. The asymmetric half-bridge flyback converter includes: a first power transistor Q. L The second power transistor Q H Primary resonant capacitor C rp Transformer leakage inductance L r Magnetizing inductance L m The third power transistor Q1, and the secondary resonant capacitor C rs For example, the diagram uses the third power transistor Q1 as an example of a synchronous rectifier; subsequent examples will specifically use Q1 as an SR. Compared to Figure 3 , Figure 4 The asymmetric half-bridge flyback converter shown also includes: a first resistor R b The second capacitor C b An LC filter. The LC filter includes: a first inductor L. f And the first capacitor C0. Figure 4 This is an asymmetric half-bridge flyback switching converter with the transformer connected to the lower half-bridge arm. Hybrid resonance can adjust the current waveform flowing through the third power transistor, reducing its effective value and thus its conduction losses. Additionally, the secondary-side resonant capacitor reduces the ripple of the first capacitor C0, minimizing conduction losses caused by its equivalent series resistance.

[0124] This application provides a hybrid resonance circuit for a switching converter, applied to an asymmetrical half-bridge flyback circuit, Q... L For the lower tube, Q H For the upper pipe, V inThe voltage is the input DC voltage, V O The voltage is the DC voltage on the output side, I O The voltage is the DC current on the output side.

[0125] like Figure 5 The diagram shown is a circuit diagram of an asymmetric half-bridge flyback converter provided in an embodiment of this application. Compared to Figure 4 , Figure 5 The asymmetric half-bridge flyback converter shown is an asymmetric half-bridge flyback switching converter with the transformer connected to the upper half-bridge arm. Figure 5 and Figure 4 The difference is that, Figure 5 The bridge arm connected to the transformer and Figure 4 The bridge arms connected to the transformers are different.

[0126] like Figure 6 The diagram shown is an equivalent circuit diagram of the hybrid resonance circuit provided in an embodiment of this application, wherein... Figure 6 The upper part shown is the first switching transistor Q. L When the circuit is turned on, three current loops are formed, namely the primary resonant capacitor C. rp L f L m The first current loop formed by the primary winding of an ideal transformer. The secondary winding of an ideal transformer, Q1, C... rs This forms a second current loop. On the secondary side of an ideal transformer, Q1, L... f The third current loop is formed by C0 and the DC load. The first switching transistor Q... L The equivalent circuit of the three current loops formed when the circuit is on is as follows: Figure 6 The lower half is shown. Figure 6 In this context, I0 represents the output current of the DC load. Indicate C rs Equivalent capacitance to the primary side This represents the equivalent current of I0 to the primary side.

[0127] like Figure 7 The diagram shown is a schematic representation of the current variation in an asymmetric half-bridge flyback converter provided in an embodiment of this application. Figure 7 It can be seen that I Q1 I represents the secondary current flowing through the third power transistor. LM I represents the primary excitation current. Lr Let t1-t0 = D*T and t2-t1 = (1-D)*T. Here, * indicates multiplication, D is the duty cycle of the asymmetric half-bridge flyback converter, and T is the switching period of the asymmetric half-bridge flyback converter.

[0128] Between time t0 and t1, the second switch Q HIt is in the conducting state. At this time, the primary-side capacitor C rp After the second switch, the magnetizing inductor, and the transformer leakage inductance form a closed loop, the current in the magnetizing inductor increases almost linearly, and there is no current output from the secondary winding of the transformer. Between times t1 and t2, the first switch Q... L In the conducting state, such as Figure 6 In the three current loops shown, the current in the magnetizing inductor decreases almost linearly, and the primary winding current under primary resonance and the primary winding current under hybrid resonance are both sinusoidal waveforms.

[0129] Figure 7 The various current values ​​shown satisfy the following relationship:

[0130]

[0131]

[0132] Among them, I Lm I represents the primary excitation current. Lr-P This represents the primary winding current under primary resonance. I represents the secondary winding current under primary-side resonance. Lr-m This represents the primary winding current under hybrid resonance. This represents the secondary winding current under hybrid resonance.

[0133] I av I represents the average current flowing through the third power transistor when it is turned on. av =I0 / (1-D), where D is the duty cycle of the asymmetric half-bridge flyback converter, D = V0 / V in V0 is the output voltage, V in This is the input voltage.

[0134] In the case of hybrid resonance, the secondary winding current is closer to the average value of the secondary winding (third power transistor) current. When the average value of the secondary winding current remains unchanged, the effective value of the secondary winding current can be reduced by adjusting the hybrid resonance parameters, thus reducing the conduction loss of the third power transistor.

[0135] In this application embodiment, adjusting the parameters of the hybrid resonance can be achieved in various ways, such as the following two adjustment methods:

[0136] (1) Adjust the ratio of the hybrid resonance This allows adjustment of the current waveform of the third power transistor, minimizing the effective value of the secondary winding current and thus reducing I. RMS / I av To minimize the conduction loss of the third power transistor, I should be kept as small as possible. RMSI represents the effective value of the current flowing through the third power transistor when it is turned on. av This represents the average current flowing through the third power transistor when it is turned on.

[0137] (2) Adjusting the initial value of the resonant state allows adjustment of the current waveform of the third power transistor, making I... RMS / I av Minimize the conduction loss of the third power transistor as much as possible.

[0138] The following section explains the implementation process of primary-side resonance, secondary-side resonance, and hybrid resonance from the perspective of their working principles.

[0139] When only the primary resonant capacitor is present, the secondary capacitor is considered as a constant voltage source, and the state equation of the resonant circuit is:

[0140]

[0141] Among them, V Crp C rp The voltage value at both ends, i Lr For flow through L r The current value, L r This represents the inductance value of the transformer leakage inductance, where V0 is the output voltage, and N... p / N s This represents the turns ratio of the primary and secondary sides of the transformer.

[0142] At this time, the primary current i Lr for:

[0143]

[0144] Among them, V Crp0 C rp The initial voltage value, Z is ω represents t0 represents the initial time point of the resonant state, I Lr0 Indicates flow through L r The initial current value, V0 represents the output voltage.

[0145] Here's an example of the waveform of the primary current mentioned above, such as... Figure 8 The diagram shown is a schematic representation of the primary-side current change with only the primary-side resonant capacitor provided in an embodiment of this application. Figure 8 It can be seen that i Lr (t) represents the primary winding current, i Lr (t) is around i Lr =0 oscillating sinusoidal waveform.

[0146] When only the secondary-side resonant capacitor is present, the primary-side capacitor is considered as a constant voltage source, and the state equation of the resonant circuit is:

[0147]

[0148] At this time, the primary current i Lr for:

[0149]

[0150] Among them, V Crs0 C rs The initial voltage value, Z is ω represents t0 represents the initial time point of the resonant state, I Lr0 L represents r The initial current value, V0 represents the output voltage, I Lm0 L represents m The initial current value.

[0151] Here's an example of the waveform of the primary current mentioned above, such as... Figure 9 The diagram shown illustrates the primary-side current variation in a hybrid resonance formed by the primary-side resonant capacitor and the secondary-side resonant capacitor according to an embodiment of this application. Figure 9 It can be seen that, from top to bottom, i Lr (t) represents the primary winding current, i Lm (t) represents the magnetizing inductor current. I0 represents the output current. Lr (t) is around i Lr-Linear (t) The oscillating sinusoidal waveform.

[0152] The primary-side current waveform of a hybrid resonance is equivalent to a mixture of the primary-side current waveforms of primary-side resonance and secondary-side resonance, such as... Figure 10 The diagram shows the primary-side current variation of a hybrid resonance formed by the primary-side resonant capacitor and the secondary-side resonant capacitor according to an embodiment of this application. The dashed box represents a time window with a size of (1-D)*T, where T represents the switching cycle of an asymmetric half-bridge flyback converter. Within a time period of (1-D)*T, the primary-side current waveform of the hybrid resonance is equivalent to... Figure 10 The waveforms of the currents after mixing are shown in the dashed boxes on the left and right. It can be seen that the current waveform of the hybrid resonance can be adjusted more flexibly. During the adjustment process, the overall current can be made closer to the average value, thereby reducing the effective value of the current flowing through the third power transistor.

[0153] As illustrated by the foregoing examples, the secondary-side resonant capacitor introduced in this embodiment achieves hybrid resonance, effectively adjusting the original resonant current waveform, reducing the effective value of the secondary-side resonant current, decreasing the conduction loss of the third power transistor, and improving the efficiency of the asymmetric half-bridge flyback converter. Furthermore, in this embodiment, the secondary-side resonant capacitor can reduce the ripple current flowing through the output electrolytic capacitor, lowering the electrolytic capacitor's losses and further improving the efficiency of the asymmetric half-bridge flyback converter.

[0154] This application also provides a power supply system, such as... Figure 11 As shown, the power supply system includes: a DC power supply and as described above. Figure 1 , Figures 3 to 5 The asymmetric half-bridge flyback converter described in any one of the following statements, wherein,

[0155] The input terminal of the asymmetric half-bridge flyback converter is coupled to the DC power supply.

[0156] In some embodiments of this application, the power system further includes: a load,

[0157] The load is coupled to the output of the asymmetric half-bridge flyback converter.

[0158] As illustrated by the foregoing examples of the embodiments of this application, the power supply system may include an asymmetric half-bridge flyback converter. This asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across the two ends of a DC power supply. The transformer includes a magnetizing inductor and a leakage inductance. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because the primary side of the transformer is coupled with the primary-side resonant capacitor, and the secondary side is coupled with the secondary-side resonant capacitor, the current waveform flowing through the third power transistor can be adjusted through their cooperation. This reduces the effective value of the current flowing through the third power transistor, thereby reducing its conduction losses and improving the efficiency of the asymmetric half-bridge flyback converter, thus also improving the efficiency of the power supply system.

[0159] This application embodiment also provides a power supply system, the power supply system including: a DC power supply and as described above. Figures 1 to 2 The asymmetric half-bridge converter described in any one of the following statements, wherein,

[0160] The input terminal of the asymmetric half-bridge converter is coupled to the DC power supply.

[0161] In some embodiments of this application, the power system further includes: a load,

[0162] The load is coupled to the output of the asymmetric half-bridge converter.

[0163] As illustrated by the foregoing examples of the embodiments of this application, the power supply system may include an asymmetric half-bridge converter. This asymmetric half-bridge converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor. The first and second power transistors are connected in series and coupled across the two ends of a DC power supply. The transformer includes a magnetizing inductor and a leakage inductance. The primary side of the transformer is connected in parallel across the first power transistor via the primary-side resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary-side resonant capacitor. Because the primary side of the transformer is coupled with the primary-side resonant capacitor, and the secondary side is coupled with the secondary-side resonant capacitor, the waveform of the current flowing through the third power transistor can be adjusted through their cooperation. This reduces the effective value of the current flowing through the third power transistor, thereby reducing its conduction losses and improving the efficiency of the asymmetric half-bridge converter, thus also improving the efficiency of the power supply system.

[0164] The embodiments of this application do not specifically limit the implementation type of the switching transistor, but specifically refer to controllable switching transistors, such as metal-oxide-semiconductor field-effect transistors, insulated-gate bipolar transistors, etc.

[0165] It should be noted that the terms "first" and "second" in the specification, claims, and accompanying drawings of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements but may include other elements not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0166] In this application, "at least one" means one or more, and "more" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0167] In the various embodiments of this application, all functional units can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0168] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any way. Although this application has disclosed preferred embodiments above, it is not intended to limit the application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. An asymmetrical half-bridge flyback converter, characterized in that, The asymmetric half-bridge flyback converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor, wherein... The first power transistor and the second power transistor are connected in series and coupled to both ends of the DC power supply; The primary side of the transformer is connected in parallel to the two ends of the first power transistor via the primary resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary resonant capacitor. One end of the third power transistor is connected to the same-name terminal of the secondary side of the transformer, and the other end of the third power transistor is connected to one end of the secondary resonant capacitor. The other end of the secondary resonant capacitor is connected to the opposite-name terminal of the secondary side of the transformer. The secondary resonant capacitor is connected to the output terminal of the asymmetric half-bridge flyback converter.

2. The asymmetrical half bridge flyback converter of claim 1, wherein, The transformer includes: a magnetizing inductor and a transformer leakage inductance. When the first power transistor is turned on, the primary resonant capacitor, the secondary resonant capacitor, and the transformer leakage inductance all participate in resonance, and the resonance is a hybrid resonance.

3. The asymmetrical half bridge flyback converter of claim 1, wherein, The transformer includes: a magnetizing inductor and a transformer leakage inductance. When the first power transistor is turned on, the secondary resonant capacitor and the transformer leakage inductance participate in the resonance, but the primary capacitor of the transformer does not participate in the resonance. The resonance is a secondary resonance, wherein the primary capacitor is the capacitor coupled to the primary side of the transformer.

4. The asymmetric half-bridge flyback converter according to any one of claims 1 to 3, characterized in that, The asymmetric half-bridge flyback converter further includes: a filter, wherein, The filter is connected in parallel with the secondary resonant capacitor; The filter is used to reduce the ripple of the output voltage of the asymmetric half-bridge flyback converter.

5. The asymmetric half-bridge flyback converter according to claim 4, characterized in that, The filter includes: a first inductor and a first capacitor. The first inductor is used to reduce the ripple of the first capacitor; The secondary resonant capacitor is also used to reduce the ripple of the first capacitor, thereby reducing the losses caused by the equivalent series resistance (ESR) of the first capacitor.

6. The asymmetric half-bridge flyback converter according to claim 4, characterized in that, The filters include: single-stage LC filters and multi-stage LC filters.

7. The asymmetric half-bridge flyback converter according to claim 2, characterized in that, By adjusting the parameters of the hybrid resonance, the effective value of the current flowing through the third power transistor is reduced.

8. The asymmetric half-bridge flyback converter according to claim 7, characterized in that, The parameters for adjusting the hybrid resonance include at least one of the following: Adjust the primary-side resonant capacitor, adjust the secondary-side resonant capacitor, and adjust the ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side; The ratio of the capacitance value of the primary-side resonant capacitor to the equivalent capacitance value of the secondary-side resonant capacitor on the primary side is expressed as follows: , Among them, the This represents the capacitance value of the primary-side resonant capacitor. This represents the equivalent capacitance value of the secondary-side resonant capacitor on the primary side. This represents the capacitance value of the secondary resonant capacitor. This indicates the number of turns in the primary winding of the transformer. This indicates the number of turns in the secondary winding of the transformer.

9. The asymmetric half-bridge flyback converter according to claim 7, characterized in that, The adjustment of the parameters of the hybrid resonance includes: adjusting the initial state value of the hybrid resonance; The asymmetric half-bridge flyback converter further includes: a second capacitor, which is connected in parallel with the third power transistor; The second capacitor is used to adjust the initial state value of the hybrid resonance.

10. The asymmetric half-bridge flyback converter according to claim 9, characterized in that, The asymmetric half-bridge flyback converter also includes: a first resistor, The first resistor and the second capacitor are connected in series; The first resistor is used to reduce the current surge to the third power transistor and reduce current oscillation when the third power transistor is turned on.

11. The asymmetric half-bridge flyback converter according to claim 3, characterized in that, By adjusting the parameters of the secondary resonant circuit, the effective value of the current flowing through the third power transistor is reduced.

12. The asymmetric half-bridge flyback converter according to claim 11, characterized in that, The adjustment of the parameters of the secondary resonant circuit includes: adjusting the secondary resonant capacitor.

13. The asymmetric half-bridge flyback converter according to claim 11, characterized in that, The adjustment of the parameters of the secondary side resonance includes: adjusting the initial state value of the resonant element of the secondary side resonance; The asymmetric half-bridge flyback converter further includes: a second capacitor, which is connected in parallel with the third power transistor; The second capacitor is used to adjust the initial state value of the secondary side resonance.

14. The asymmetric half-bridge flyback converter according to any one of claims 1 to 3, characterized in that, The first power transistor is the upper transistor, and the second power transistor is the lower transistor; or... The first power transistor is the lower transistor, and the second power transistor is the upper transistor.

15. The asymmetric half-bridge flyback converter according to any one of claims 1 to 3, characterized in that, The third power transistor includes at least one of the following: a synchronous rectifier diode or a diode.

16. An asymmetric half-bridge converter, characterized in that, The asymmetric half-bridge converter includes: an asymmetric half-bridge flyback converter as described in any one of claims 1 to 15; or... The asymmetric half-bridge converter includes: an asymmetric half-bridge forward converter. The connection method of the same-name terminal of the transformer in the asymmetric half-bridge forward converter is opposite to that of the same-name terminal of the transformer in the asymmetric half-bridge flyback converter; the asymmetric half-bridge forward converter includes: a first power transistor, a second power transistor, a primary-side resonant capacitor, a transformer, a third power transistor, and a secondary-side resonant capacitor, wherein, The first power transistor and the second power transistor are connected in series and coupled to both ends of the DC power supply; The primary side of the transformer is connected in parallel to the two ends of the first power transistor via the primary resonant capacitor. The secondary side of the transformer is coupled with the third power transistor and the secondary resonant capacitor. One end of the third power transistor is connected to the same-name terminal of the secondary side of the transformer, and the other end of the third power transistor is connected to one end of the secondary resonant capacitor. The other end of the secondary resonant capacitor is connected to the opposite-name terminal of the secondary side of the transformer. The secondary resonant capacitor is connected to the output terminal of the asymmetric half-bridge flyback converter.

17. A power supply system, characterized in that, The power supply system includes: a DC power supply and an asymmetric half-bridge flyback converter as described in any one of claims 1 to 15, wherein, The input terminal of the asymmetric half-bridge flyback converter is coupled to the DC power supply.

18. A power supply system, characterized in that, The power supply system includes: a DC power supply and an asymmetric half-bridge converter as described in claim 16, wherein... The input terminal of the asymmetric half-bridge converter is coupled to the DC power supply.

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