Power converter and control method thereof

Abstract

The invention provides a power converter and a control method thereof. The power converter comprises a transformer, an inductance-capacitance resonance circuit, a first switch, a second switch and a controller. The transformer includes a primary side winding and a secondary side winding. The inductor-capacitor resonant circuit is coupled to the primary side winding. The inductor-capacitor resonant circuit includes a resonant capacitor and a resonant inductor. The first switch and the second switch are coupled to the inductance-capacitance resonance circuit. The controller complementarily controls on and off of the first switch and the second switch according to the received output voltage feedback signal of the power converter so as to adjust the magnitude of the output voltage of the power converter.

Description

Technical Field

[0001] The present application relates to a power converter and a control method thereof, and more particularly to an asymmetric half-bridge flyback converter and a control method thereof. Background Art

[0002] A half-bridge DC converter is a power conversion architecture that converts a DC voltage into a different DC voltage. It is mainly composed of two switching transistors, i.e., the switch elements are alternately turned on and off to achieve the purpose of adjusting the voltage output. Furthermore, the asymmetric half-bridge converter (AHB converter) has the characteristics of fewer components, switch voltage clamping and flexible switching, so it is widely used in the field of medium and low power power conversion. The half-bridge converter is controlled by pulse width modulation of the switch asymmetric duty cycle to achieve flexible switching of the switch of the half-bridge converter.

[0003] The asymmetric half-bridge flyback converter (AHB flyback converter) combines the advantages of the primary-side zero voltage switching of the LLC resonant circuit architecture and the wide voltage output of the flyback architecture. It is suitable for power conversion applications with high switching frequencies. However, under the architecture of this converter, after the AC is turned off, the resonant capacitor of the LLC resonant circuit will have residual energy. Therefore, if the AC power is turned on again, the grounded switch in the converter will be turned on, which will cause the residual energy on the resonant capacitor to be instantly conducted to the ground, generating a surge current. This surge current will cause the risk of damage to the switch, and the level of switch stress must be increased, which will increase the circuit cost.

[0004] Therefore, how to design a power converter and a control method thereof to solve the problems and technical bottlenecks existing in the prior art is an important topic studied in this case. Summary of the invention

[0005] One aspect of the present invention is to provide a power converter, including a transformer, an inductor-capacitor resonant circuit, a first switch, a second switch coupled to the first switch, and a controller. The transformer includes a primary winding and a secondary winding coupled to the primary winding. The inductor-capacitor resonant circuit is coupled to the primary winding, and the inductor-capacitor resonant circuit includes a resonant capacitor and a resonant inductor, wherein the resonant inductor is the excitation inductance of the primary winding. The first switch and the second switch are coupled to the inductor-capacitor resonant circuit. The controller complementarily controls the first switch and the second switch to turn on and off according to the output voltage feedback signal received from the power converter to adjust the output voltage of the power converter.

[0006] In one embodiment, the power converter further includes a discharge circuit connected in parallel with the resonant capacitor.

[0007] In one embodiment, the discharge circuit includes a resistor and a switch, wherein the switch is connected in series with the resistor.

[0008] In one embodiment, the first switch is connected in parallel with the inductor-capacitor resonant circuit.

[0009] In one embodiment, the second switch is connected in parallel with the inductor-capacitor resonant circuit.

[0010] In one embodiment, the controller provides a first control signal to control the first switch, provides a second control signal to control the second switch, and provides a discharge control signal to control the switch.

[0011] In one embodiment, based on the power converter being powered by an input power supply: when the first switch is turned off, the second switch is turned on, and the switch is turned off, the resonant inductor stores energy; when the first switch is turned on, the second switch is turned off, and the switch is turned off, the resonant inductor resonates with the resonant capacitor to transfer the stored energy of the resonant inductor to the secondary side winding.

[0012] In one embodiment, based on the power converter interrupting the input power supply, the switch is turned on, and the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

[0013] In one embodiment, the power converter is powered again based on the input power: when the first switch is turned off, the second switch is turned on, and the switch is turned off, the power converter is started in a state where the voltage across the resonant capacitor is zero.

[0014] In one embodiment, based on the power converter being powered by an input power supply: when the first switch is turned on, the second switch is turned off, and the switch is turned off, the resonant inductor stores energy; when the first switch is turned off, the second switch is turned on, and the switch is turned off, the resonant inductor resonates with the resonant capacitor to transfer the stored energy of the resonant inductor to the secondary side winding.

[0015] In one embodiment, based on the power converter interrupting the input power supply, the switch is turned on, and the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

[0016] In one embodiment, the power converter is repowered based on the input power: when the first switch is turned on, the second switch is turned off, and when the switch is turned off, the power converter is started in a state where the voltage across the resonant capacitor is zero.

[0017] Thus, the power converter proposed by the present invention has the following features and advantages: the present invention connects a discharge circuit, i.e., a bleeder circuit, in parallel with the resonant capacitor, and after the AC is turned off, the switch is turned on, so that the energy on the resonant capacitor can be discharged by using a resistor. When the AC is turned on again, there is no voltage difference between the two ends of the resonant capacitor, and the power converter is started, thereby protecting the switch element through zero voltage switching.

[0018] Another aspect of the present invention is to provide a control method for a power converter, the power converter comprising an inductor-capacitor resonant circuit having a resonant capacitor and a resonant inductor, a first switch and a second switch coupled to the inductor-capacitor resonant circuit, and a discharge circuit connected in parallel to the resonant capacitor and having a resistor and a switch, the control method for the power converter comprising: based on the power converter being powered by an input power supply: controlling the first switch to be turned off, the second switch to be turned on, and when the switch is turned off, storing energy in the resonant inductor; and controlling the first switch to be turned on, the second switch to be turned off, and when the switch is turned off, the resonant inductor and the resonant capacitor to resonate and transfer the stored energy of the resonant inductor to the secondary side winding.

[0019] In one embodiment, the control method of the power converter further includes: based on the power converter interrupting the input power supply: controlling the switch to be turned on, so that the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

[0020] In one embodiment, the control method of the power converter further includes: re-powering the power converter based on the input power supply: controlling the first switch to be turned off, the second switch to be turned on, and the switch to be turned off, and starting the power converter when the voltage across the resonant capacitor is zero.

[0021] Thus, the control method of the power converter proposed by the present invention has the following features and advantages: the present invention connects a discharge circuit, i.e., a bleeder circuit, in parallel with the resonant capacitor, and after the AC is turned off, the switch is turned on, so that the energy on the resonant capacitor can be discharged by using a resistor. When the AC is turned on again, there is no voltage difference between the two ends of the resonant capacitor, and the power converter is started, thereby protecting the switch element through zero voltage switching.

[0022] In order to further understand the technologies, means and effects adopted by the present application to achieve the intended purpose, please refer to the following detailed description and drawings of the present application. It is believed that the purpose, characteristics and features of the present application can be deeply and specifically understood thereby. However, the drawings are only provided for reference and illustration and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a circuit diagram of a first embodiment of a power converter of the present invention;

[0024] Figure 2is a circuit diagram of a second embodiment of a power converter of the present invention;

[0025] Figure 3 is a circuit diagram of a third embodiment of a power converter of the present invention;

[0026] Figure 4 is a circuit diagram of a fourth embodiment of a power converter of the present invention;

[0027] Figure 5 A schematic diagram of a switch control circuit of a power converter according to a third embodiment of the present invention;

[0028] Figure 6 A circuit diagram of switch control of a fourth embodiment of a power converter according to the present invention;

[0029] Figure 7A to Figure 7D A current diagram of the operation of the power converter of the third embodiment of the present invention;

[0030] Figures 8A to 8D A current diagram of the operation of the power converter of the fourth embodiment of the present invention;

[0031] Fig. 9 is a flow chart of a control method of a power converter according to the present invention;

[0032] Wherein, the reference numerals are:

[0033] TR: Transformer

[0034] 10: Inductor-capacitor resonant circuit

[0035] 20: Controller

[0036] 30: Discharge circuit

[0037] S1: First switch

[0038] S2: Second switch

[0039] W1: primary winding

[0040] W2: Secondary winding

[0041] Cr: resonant capacitor

[0042] Lm: Excitation inductance

[0043] Vbulk: DC voltage

[0044] Ns: Node

[0045] Q1: Switch

[0046] R1: Resistor

[0047] S VOUT :Output voltage feedback signal

[0048] S S1 :First control signal

[0049] S S2 : Second control signal

[0050] S Q1 :Discharge control signal

[0051] S10~S30: steps. DETAILED DESCRIPTION

[0052] In this specification, many specific details are provided to provide a thorough understanding of the specific embodiments of the present application; however, those skilled in the art should know that the present application can still be practiced without one or more of these specific details; in other cases, well-known details are not shown or described to avoid obscuring the main technical features of the present application. The technical content and detailed description of the present application are described as follows with the help of the drawings:

[0053] See also Figure 1 and Figure 2 , which are circuit diagrams of the first and second embodiments of the power converter of the present invention. As shown in the figure, the power converter includes a transformer TR, an inductor-capacitor resonant circuit 10, a first switch S1, a second switch S2 and a controller 20. The transformer TR includes a primary winding W1 and a secondary winding W2 coupled to the primary winding W1.

[0054] The inductor-capacitor resonant circuit 10, i.e., an LC resonant circuit, is coupled to the primary winding W1. The inductor-capacitor resonant circuit 10 includes a resonant capacitor Cr and a resonant inductor, wherein the resonant inductor is the excitation inductance Lm of the primary winding W1, i.e., the excitation inductance Lm and the resonant capacitor Cr respectively provide the inductance (L) part and the capacitance (C) part of the inductor-capacitor resonant circuit 10. Furthermore, the inductor-capacitor resonant circuit 10 coupled to the primary winding W1 receives a DC voltage Vbulk.

[0055] The first switch S1 and the second switch S2 are coupled to the inductor-capacitor resonant circuit 10. Figure 1In the first embodiment shown, the first switch S1 and the second switch S2 are connected to the node Ns. One end of the first switch S1 which is not the control end, such as but not limited to the drain of an n-type MOS switch, is coupled to the excitation inductance Lm of the inductor-capacitor resonant circuit 10 and the DC voltage Vbulk, while the other end which is not the control end, such as but not limited to the source of the n-type MOS switch, is coupled to the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 and the node Ns. One end of the second switch S2 which is not the control end, such as but not limited to the drain of the n-type MOS switch, is coupled to the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 and the node Ns, while the other end which is not the control end, such as but not limited to the source of the n-type MOS switch, is grounded. Therefore, in the first embodiment, the first switch S1 is connected in parallel to the inductor-capacitor resonant circuit 10. In this embodiment, the aforementioned control end refers to the gate of the n-type MOS switch.

[0056] like Figure 2 In the second embodiment shown, the first switch S1 and the second switch S2 are connected to the node Ns. One end of the first switch S1 which is not the control end, such as but not limited to the drain of the n-type MOS switch, is coupled to the DC voltage Vbulk, and the other end which is not the control end, such as but not limited to the source of the n-type MOS switch, is coupled to the excitation inductance Lm of the inductor-capacitor resonant circuit 10 and the node Ns. One end of the second switch S2 which is not the control end, such as but not limited to the drain of the n-type MOS switch, is coupled to the excitation inductance Lm of the inductor-capacitor resonant circuit 10 and the node Ns, and the other end which is not the control end, such as but not limited to the source of the n-type MOS switch, is coupled to the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 and is grounded. Therefore, in the second embodiment, the second switch S2 is connected in parallel to the inductor-capacitor resonant circuit 10. In this embodiment, the control end disclosed above refers to the gate of the n-type MOS switch.

[0057] The controller 20 receives the output voltage feedback signal S of the power converter. VOUT (See first Figure 5 , Figure 6 , which will be described later) complementarily controls the first switch S1 and the second switch S2 to turn on and off, so as to adjust the output voltage of the power converter. By the way, the output voltage feedback signal S VOUT is a signal that is positively correlated with the output voltage, such as a voltage signal. In other words, the output voltage feedback signal S VOUT The voltage value of the output voltage can reflect the value of the output voltage. Therefore, the controller 20 generates a voltage signal S according to the output voltage feedback signal S. VOUTThe voltage size (that is, the size of the output voltage) is adjusted to control the on and off of the first switch S1 and the second switch S2, that is, to adjust the on and off time of the first switch S1 and the second switch S2, so as to adjust the size of the energy stored on the primary side of the power converter and the energy transferred to the secondary side, thereby adjusting the size of the output voltage of the power converter.

[0058] See also Figure 3 and Figure 4 As shown in FIG. 1 , they are circuit diagrams of the third and fourth embodiments of the power converter of the present invention. Figure 1 and Figure 2 The embodiment shown, Figure 3 and Figure 4 The power converter further includes a discharge circuit 30. The discharge circuit 30 is connected in parallel to the resonant capacitor Cr. Specifically, the resonant capacitor Cr includes a resistor R1 and a switch Q1, and the switch Q1 is connected in series to the resistor R1 to form a series branch. Figure 3 In the third embodiment, two ends of the series branch are respectively connected to two ends of the resonant capacitor Cr, one end of the series branch is connected to the excitation inductor Lm, and the other end is connected to the node Ns. Figure 4 In the fourth embodiment, the two ends of the series branch are respectively connected to the two ends of the resonant capacitor Cr, and one end is connected to the excitation inductor Lm, and the other end is grounded. Incidentally, the discharge circuit used in the present invention is not limited to the components and structures shown in the figure, and any circuit structure that can provide a discharge path for releasing energy and the circuit components used therein should be included in the scope of the present invention.

[0059] See also Figure 5 and Figure 6 , which are respectively the circuit schematic diagram of the switch control of the power converter of the third embodiment and the circuit schematic diagram of the switch control of the fourth embodiment of the present invention. The controller 20 provides a first control signal S S1 Control the on and off of the first switch S1 to provide a second control signal S S2 Controls the on and off of the second switch S2 and provides a discharge control signal S Q1 Controls the on and off of the switch Q1.

[0060] See also Figure 7A to Figure 7D , is a current diagram of the operation of the third embodiment of the power converter of the present invention. Fig. 7A As shown, the controller 20 provides a first control signal S S1 The first switch S1 is controlled to be turned off, and the second control signal S S2 Control the second switch S2 to be turned on, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, the resonant inductance (ie, the excitation inductance Lm) of the inductor-capacitor resonant circuit 10 stores energy. Fig. 7A As shown, the current during the energy storage operation flows from the DC voltage Vbulk through the excitation inductor Lm, the resonant capacitor Cr and the second switch S2 to the ground. Therefore, the input power supply (which can be represented by the DC voltage Vbulk) stores energy in the excitation inductor Lm.

[0061] like Figure 7B As shown, the controller 20 provides a first control signal S S1 The first switch S1 is controlled to be turned on, and the second control signal S S2 Control the second switch S2 to turn off, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, the resonant inductor (ie, the magnetizing inductor Lm) resonates with the resonant capacitor Cr, and the energy stored in the resonant inductor is transferred to the secondary winding W2 to provide the power required by the output side load.

[0062] As mentioned above, under the architecture of this converter, after the AC is turned off, the resonant capacitor of the resonant circuit will have residual energy. Therefore, if the AC power is turned on again, the grounded switch in the converter will be turned on, causing the residual energy on the resonant capacitor to be instantly conducted to the ground, generating a surge current. This surge current will cause the switch to be damaged. Figure 7C As shown, when the power converter is interrupted, the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 will have residual energy. Therefore, when the power converter interrupts the input power (which can be represented by the DC voltage Vbulk), the first control signal S provided by the controller 20 S1 The first switch S1 is controlled to be turned off, and the second control signal S S2 Control the second switch S2 to turn off, and the discharge control signal S Q1 The switch Q1 is controlled to be turned on. In this operation, the residual energy of the resonant capacitor Cr is released through the discharge path provided by the series branch formed by the resistor R1 of the discharge circuit 30 and the switch Q1, that is, the energy of the resonant capacitor Cr is released.

[0063] Afterwards, if Fig.7D As shown, when the input power (represented by the DC voltage Vbulk) supplies power to the power converter again, the first control signal S provided by the controller 20 S1 The first switch S1 is controlled to be turned off, and the second control signal S S2 Control the second switch S2 to be turned on, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, since the voltage across the resonant capacitor Cr is zero (because the residual energy has been released), the power converter can be started when the voltage across the resonant capacitor Cr is zero, thereby protecting the switching element through zero voltage switching.

[0064] See also Figures 8A to 8D , is a current diagram of the operation of the fourth embodiment of the power converter of the present invention. Fig. 8A As shown, the controller 20 provides a first control signal S S1 The first switch S1 is controlled to be turned on, and the second control signal S S2 Control the second switch S2 to turn off, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, the resonant inductance (ie, the excitation inductance Lm) of the inductor-capacitor resonant circuit 10 stores energy. Fig. 8A As shown, the current during the energy storage operation flows from the DC voltage Vbulk through the first switch S1, the excitation inductor Lm and the resonant capacitor Cr to the ground. Therefore, the input power supply (which can be represented by the DC voltage Vbulk) stores energy in the excitation inductor Lm.

[0065] like Figure 8B As shown, the controller 20 provides a first control signal S S1 The first switch S1 is controlled to be turned off, and the second control signal S S2 Control the second switch S2 to be turned on, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, the resonant inductor (ie, the magnetizing inductor Lm) resonates with the resonant capacitor Cr, and the energy stored in the resonant inductor is transferred to the secondary winding W2 to provide the power required by the output side load.

[0066] As mentioned above, under the architecture of this converter, after the AC is turned off, the resonant capacitor of the resonant circuit will have residual energy. Therefore, if the AC power is turned on again, the grounded switch in the converter will be turned on, causing the residual energy on the resonant capacitor to be instantly conducted to the ground, generating a surge current. This surge current will cause the switch to be damaged. Figure 8C As shown, when the power converter is interrupted, the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 will have residual energy. Therefore, when the power converter interrupts the input power (which can be represented by the DC voltage Vbulk), the first control signal S provided by the controller 20 S1 The first switch S1 is controlled to be turned off, and the second control signal S S2 Control the second switch S2 to turn off, and the discharge control signal S Q1 The switch Q1 is controlled to be turned on. In this operation, the residual energy of the resonant capacitor Cr is released through the discharge path provided by the series branch formed by the resistor R1 of the discharge circuit 30 and the switch Q1, that is, the energy of the resonant capacitor Cr is released.

[0067] Afterwards, if Fig.8D As shown, when the input power (represented by the DC voltage Vbulk) supplies power to the power converter again, the first control signal S provided by the controller 20S1 The first switch S1 is controlled to be turned on, and the second control signal S S2 Control the second switch S2 to turn off, and the discharge control signal S Q1 The control switch Q1 is turned off. In this operation, since the voltage across the resonant capacitor Cr is zero (because the residual energy has been released), the power converter can be started when the voltage across the resonant capacitor Cr is zero, thereby protecting the switching element through zero voltage switching.

[0068] See also Fig. 9 As shown, it is a flow chart of the control method of the power converter of the present invention, and is combined with the aforementioned Figure 1 to Figure 8D The circuit architecture of the power converter described. The control method of the power converter of the present invention, the power converter includes an inductor-capacitor resonant circuit 10 having a resonant capacitor Cr and a resonant inductor, a first switch S1 and a second switch S2 coupled to the inductor-capacitor resonant circuit 10, and a discharge circuit 30 connected in parallel to the resonant capacitor Cr and having a resistor R1 and a switch Q1. The control method of the power converter includes the steps of: based on the power converter being powered by an input power source (step S10), that is, when the input power source (which can be represented by a DC voltage Vbulk) supplies power to the power converter, controlling the first switch S1 to be turned off, the second switch S2 to be turned on, and the switch Q1 to be turned off, energy is stored in the resonant inductor (step S20). The first switch S1 is controlled by a first control signal S provided by a controller 20. S1 The second switch S2 is controlled by the second control signal S provided by the controller 20. S2 The switch Q1 is controlled by the discharge control signal S provided by the controller 20. Q1 Then, when the first switch S1 is turned on, the second switch S2 is turned off, and the switch Q1 is turned off, the resonant inductor resonates with the resonant capacitor Cr, and the energy stored in the resonant inductor is transferred to the secondary winding (step S30). Fig. 7A , Figure 7B An embodiment implemented, and Fig. 8A , Figure 8B Another embodiment implemented.

[0069] After step S30, the resonant capacitor of the resonant circuit will have residual energy due to the power converter interrupting the input power supply, that is, after the AC is turned off. Therefore, if the AC power is turned on again, the switch connected to the ground in the converter will be turned on, which will cause the residual energy on the resonant capacitor to be instantly conducted to the ground, thereby generating a surge current, which will cause the switch to be damaged. Due to the interruption of the power converter, the resonant capacitor Cr of the inductor-capacitor resonant circuit 10 will have residual energy. Therefore, when the power converter interrupts the input power supply (which can be represented by the DC voltage Vbulk), the discharge control signal S provided by the controller 20 Q1 The switch Q1 is controlled to be turned on. In this operation, the residual energy of the resonant capacitor Cr is released through the discharge path provided by the series branch formed by the resistor R1 of the discharge circuit 30 and the switch Q1, that is, the energy of the resonant capacitor Cr is released.

[0070] After releasing the energy of the resonant capacitor Cr, the power converter is powered again based on the input power. That is, when the input power (represented by the DC voltage Vbulk) is powered again to the power converter, the discharge control signal S provided by the controller 20 is Q1 The control switch Q1 is turned off. In this operation, since the voltage across the resonant capacitor Cr is zero (because the residual energy has been released), the power converter can be started when the voltage across the resonant capacitor Cr is zero, thereby protecting the switching element through zero voltage switching.

[0071] In summary, the present invention has the following features and advantages: The present invention connects a discharge circuit, i.e., a bleeder circuit, in parallel with the resonant capacitor Cr. After the AC is turned off, the switch Q1 is turned on, so that the energy on the resonant capacitor Cr can be discharged by using the resistor R1. When the AC is turned on again, there is no voltage difference between the two ends of the resonant capacitor Cr, and the power converter is started, thereby protecting the switch element through zero voltage switching.

[0072] By the way, in power supply equipment with multiple output voltages (such as PD power supply type), they are generally designed based on the maximum output voltage and maximum output wattage. Therefore, when the transformer is fixed, the leakage inductance is also fixed. Therefore, under the condition of maximum output voltage (wattage), the capacitance value of the resonant capacitor can be designed according to the formula. However, once at other output voltages, the capacitance value of this resonant capacitor cannot be the capacitance value required for the output voltage. In this case, when the capacitance value of the resonant capacitor is insufficient, the efficiency will be reduced, the voltage surge of the resonant capacitor will increase, and the resonant current will increase, which will cause damage to the transistor switch in the AHB architecture.

[0073] Since the capacitance value of a single resonant capacitor cannot be compatible with the capacitance values ​​required for all output voltages, a capacitance adjustment circuit is used to change the required capacitance value. After detecting the output voltage (i.e. knowing the output voltage), the capacitance adjustment circuit can be used to connect the resonant capacitor in parallel, in series, in parallel and in series, or in series and in parallel, thereby changing the equivalent capacitance value. Therefore, the equivalent capacitance value required under the output voltage can be designed in response to different output voltages.

[0074] Specifically, the first embodiment of the capacitance adjustment circuit is: the capacitance adjustment circuit includes a capacitor and a switch, wherein the capacitor and the switch are connected in series to form a series branch. The series branch is connected in parallel with the resonant capacitor. In addition, in this embodiment, the number of series branches can also be multiple, each connected in parallel with the resonant capacitor. Thereby, by controlling the on and off of the switch, the capacitance of the parallel resonant capacitor can be adjusted to adjust the equivalent capacitance value.

[0075] The second embodiment of the capacitance adjustment circuit is as follows: the capacitance adjustment circuit comprises a capacitor and a switch, wherein the switching switch can be controlled to control whether the capacitor is connected in series with the resonant capacitor to adjust the equivalent capacitance value.

[0076] The third embodiment of the capacitance adjustment circuit is as follows: the capacitance adjustment circuit includes a first capacitor, a second capacitor, a switch, and a switching switch, wherein the first capacitor is connected in series with the switch to form a series branch. The series branch is connected in parallel with the resonant capacitor. In addition, in this embodiment, the number of series branches can also be multiple, each connected in parallel with the resonant capacitor. Furthermore, the switching switch can be controlled to control whether the second capacitor is connected in series with the resonant capacitor to adjust the equivalent capacitance value.

[0077] Embodiment 4 of the capacitance adjustment circuit is as follows: the capacitance adjustment circuit includes a first capacitor, a second capacitor, a switch, and a switching switch, wherein the second capacitor can be controlled by controlling the switching switch to control whether to connect the second capacitor in series with the resonant capacitor. The first capacitor is connected in series with the switch to form a series branch. The series branch is connected in parallel with the resonant capacitor or in parallel with the resonant capacitor and the second capacitor. In addition, in this embodiment, the number of series branches can also be multiple, respectively connecting the resonant capacitor or the resonant capacitor in parallel with the second capacitor to adjust the equivalent capacitance value.

[0078] However, the above is only a preferred embodiment of the present application, and should not limit the scope of implementation of the present application, that is, all equivalent changes and modifications made according to the present application should still fall within the scope of the patent coverage of the present application. The present application may also have other embodiments, and those skilled in the art may make various corresponding changes and deformations according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and deformations should fall within the scope of protection of the claims attached to the present application.

Claims

1. A power converter, characterized in that: include: A transformer comprising a primary winding and a secondary winding coupled to the primary winding; an inductor-capacitor resonant circuit coupled to the primary winding, the inductor-capacitor resonant circuit comprising a resonant capacitor and a resonant inductor, wherein the resonant inductor is an excitation inductor of the primary winding; A first switch and a second switch coupled to the first switch, wherein the first switch and the second switch are coupled to the inductor-capacitor resonant circuit; as well as A controller controls the first switch and the second switch to be turned on and off complementarily according to an output voltage feedback signal received from the power converter, so as to adjust the magnitude of an output voltage of the power converter.

2. The power converter according to claim 1, wherein: Also includes: A discharge circuit is connected in parallel with the resonant capacitor.

3. The power converter according to claim 2, wherein: The discharge circuit includes: a resistor; and A switch is connected in series with the resistor.

4. The power converter according to claim 3, wherein: The first switch is connected in parallel with the inductor-capacitor resonant circuit.

5. The power converter according to claim 3, wherein: The second switch is connected in parallel with the inductor-capacitor resonant circuit.

6. The power converter according to claim 3, wherein: The controller provides a first control signal to control the first switch, provides a second control signal to control the second switch, and provides a discharge control signal to control the switch.

7. The power converter according to claim 4, wherein: Based on the power converter being powered by an input power source: When the first switch is turned off, the second switch is turned on, and the switch is turned off, the resonant inductor stores energy; When the first switch is turned on, the second switch is turned off, and the switch is turned off, the resonant inductor resonates with the resonant capacitor, and the stored energy of the resonant inductor is transferred to the secondary winding.

8. The power converter according to claim 7, wherein: Based on the power converter interrupting the input power supply: The switch is turned on, and the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

9. The power converter according to claim 8, wherein: Repower the power converter based on the input power: When the first switch is turned off, the second switch is turned on, and the switch is turned off, the power converter is started in a state where the voltage across the resonant capacitor is zero.

10. The power converter according to claim 4, wherein: Based on the power converter being powered by an input power source: When the first switch is turned on, the second switch is turned off, and the switch is turned off, the resonant inductor stores energy; When the first switch is turned off, the second switch is turned on, and the switch is turned off, the resonant inductor resonates with the resonant capacitor, and the stored energy of the resonant inductor is transferred to the secondary winding.

11. The power converter according to claim 10, wherein: Based on the power converter interrupting the input power supply: The switch is turned on, and the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

12. The power converter according to claim 11, wherein: Repower the power converter based on the input power: When the first switch is turned on, the second switch is turned off, and the switch is turned off, the power converter is started in a state where the voltage across the resonant capacitor is zero.

13. A control method for a power converter, characterized in that: The power converter includes an inductor-capacitor resonant circuit having a resonant capacitor and a resonant inductor, a first switch and a second switch coupled to the inductor-capacitor resonant circuit, and a discharge circuit connected in parallel to the resonant capacitor and having a resistor and a switch. The control method of the power converter includes: Based on the power converter being powered by an input power source: Controlling the first switch to be turned off, the second switch to be turned on, and the switch to be turned off to store energy in the resonant inductor; and The first switch is controlled to be turned on, the second switch is controlled to be turned off, and when the switch is turned off, the resonant inductor resonates with the resonant capacitor, and the stored energy of the resonant inductor is transferred to the secondary winding.

14. The control method of the power converter according to claim 13, wherein: Also includes: Based on the power converter interrupting the input power supply: The switch is controlled to be turned on, and the energy on the resonant capacitor is released through a discharge path provided by the resistor and the switch.

15. The control method of the power converter according to claim 14, wherein: Also includes: Repower the power converter based on the input power: The first switch is controlled to be turned off, the second switch is controlled to be turned on, and the switch is controlled to be turned off, and the power converter is started in a state where the voltage across the resonant capacitor is zero.

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