Power converter

Abstract

A power converter includes a transformer, a resonant circuit, first and second switches, and a controller. The transformer has a primary side winding and a secondary side winding coupled to the primary side winding. The resonant circuit is coupled to the primary side winding. The resonant circuit includes a resonant capacitor and a resonant inductor. The first switch and the second switch are coupled to the resonant circuit. The controller receives an output voltage feedback signal corresponding to the output voltage of the power converter, and controls the first switch and the second switch to be alternately turned on and turned off according to the output voltage feedback signal so as to adjust the output voltage.

Description

Technical Field

[0001] The present invention relates to a power converter, and more particularly to a power converter capable of adjusting the size of a resonant capacitor. Background Art

[0002] The so-called half-bridge DC converter is a power conversion architecture that converts DC voltage into different DC voltages. It is mainly composed of two switching transistors, that is, the switch components are alternately turned on and turned off to achieve the purpose of adjusting the voltage output. In addition, 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 the pulse width modulation method of the switch asymmetric duty cycle to achieve flexible switching 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. In models with multiple output voltages, such as PD (power delivery) models, they are generally designed based on the maximum output voltage and maximum output wattage. Therefore, once the design of the transformer is fixed, the size of its leakage inductance is also fixed. Therefore, under the design conditions of the maximum output voltage and the maximum output wattage, the resonant capacitor of the AHB can be calculated and designed according to the formula. However, for other output voltages under actual operation, the resonant capacitor value cannot be the capacitance value required to meet the output voltage. In this way, when the resonant capacitor capacitance is insufficient, the efficiency will be reduced, the resonant capacitor voltage surge will increase, and the resonant current will increase, which will cause the transistor in the AHB architecture to be damaged.

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

[0005] The object of the present invention is to provide a power converter, comprising a transformer, a resonant circuit, a first switch, a second switch and a controller. The transformer has a primary winding and a secondary winding coupled to the primary winding. The resonant circuit is coupled to the primary winding. The resonant circuit comprises a resonant capacitor and a resonant inductor, wherein the resonant inductor is composed of a magnetizing inductance and a leakage inductance of the primary winding. The first switch and the second switch are coupled to the resonant circuit. The controller receives an output voltage feedback signal corresponding to the output voltage size of the power converter, and controls the first switch and the second switch to be alternately turned on and off according to the output voltage feedback signal to adjust the output voltage size.

[0006] In one embodiment, the power converter further includes a capacitor adjustment circuit. The capacitor adjustment circuit has an adjustment capacitor coupled to the resonant capacitor. The controller controls the connection relationship between the adjustment capacitor and the resonant capacitor according to the output voltage feedback signal to determine the equivalent resonant capacitance value of the resonant circuit.

[0007] In one embodiment, when the output voltage increases, the equivalent resonant capacitance value is controlled to decrease, and when the output voltage decreases, the equivalent resonant capacitance value is controlled to increase.

[0008] In one embodiment, the controller provides a first signal, a second signal, and a capacitance adjustment signal to control the first switch, the second switch, and the capacitance adjustment circuit respectively.

[0009] In one embodiment, the capacitance adjustment circuit includes a second capacitor and a third switch. The second capacitor is used as an adjustment capacitor. The third switch is connected in series with the second capacitor to form a series path. The series path is connected in parallel with the resonant capacitor.

[0010] In one embodiment, when the third switch is turned off and the resonant circuit performs a resonant operation, the first equivalent resonant capacitance value is the capacitance value of the resonant capacitance, and the resonant current flows through the resonant capacitance. When the third switch is turned on and the resonant circuit performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance in parallel with the second capacitance, and the resonant current flows through the resonant capacitance and the second capacitance respectively.

[0011] In one embodiment, when the capacitance value of the resonant capacitor is equal to the capacitance value of the second capacitor, the second equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value. When the output voltage is less than the voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value. When the output voltage is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value.

[0012] In one embodiment, the capacitance adjustment circuit includes a third capacitor and a fourth switch. The third capacitor is used as an adjustment capacitor. The fourth switch has a common terminal, a first switching terminal and a second switching terminal. The common terminal is connected to the resonant capacitor, the first switching terminal is connected to an end of the third capacitor close to the magnetizing inductor, and the second switching terminal is connected to the other end of the third capacitor.

[0013] In one embodiment, when the common terminal of the fourth switch is connected to the first switching terminal and the resonant circuit performs a resonant operation, the first equivalent resonant capacitance value is the capacitance value of the resonant capacitance, and the resonant current flows through the resonant capacitance. When the common terminal of the fourth switch is connected to the second switching terminal and the resonant circuit performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance connected in series with the third capacitance, and the resonant current flows through the third capacitance and the resonant capacitance.

[0014] In one embodiment, when the capacitance value of the resonant capacitor is equal to the capacitance value of the third capacitor, the first equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value. When the output voltage is less than the voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value. When the output voltage is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

[0015] In one embodiment, the capacitance adjustment circuit includes a second capacitor and a third capacitor, a third switch and a fourth switch. The second capacitor and the third capacitor are used as adjustment capacitors. The third switch is connected in series with the second capacitor to form a series path. The series path is connected in parallel with the resonant capacitor. The fourth switch has a common terminal, a first switching terminal and a second switching terminal. The common terminal connects the resonant capacitor and the second capacitor, the first switching terminal connects one end of the third capacitor close to the magnetizing inductor, and the second switching terminal connects the other end of the third capacitor.

[0016] In one embodiment, when the third switch is turned off and the common terminal of the fourth switch is connected to the first switching terminal, when the resonant circuit performs a resonant operation, the first equivalent resonant capacitance value is the capacitance value of the resonant capacitance, and the resonant current flows through the resonant capacitance. When the third switch is turned off and the common terminal of the fourth switch is connected to the second switching terminal, when the resonant circuit performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance in series with the third capacitance, and the resonant current flows through the third capacitance and the resonant capacitance. When the third switch is turned on and the common terminal of the fourth switch is connected to the first switching terminal, when the resonant circuit performs a resonant operation, the third equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance in parallel with the second capacitance, and the resonant current flows through the resonant capacitance and the second capacitance respectively. When the third switch is turned on and the common terminal of the fourth switch is connected to the second switching terminal, when the resonant circuit performs a resonant operation, the fourth equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance in parallel with the second capacitance, and then in series with the third capacitance, and the resonant current flows through the third capacitance and flows through the resonant capacitance and the second capacitance respectively.

[0017] In one embodiment, when the capacitance value of the resonant capacitor, the capacitance value of the second capacitor, and the capacitance value of the third capacitor are equal, the third equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value, the first equivalent resonant capacitance value is greater than the fourth equivalent resonant capacitance value, and the fourth equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value. When the output voltage is less than the first voltage threshold, the equivalent capacitance value of the resonant circuit is the third equivalent resonant capacitance value. When the output voltage is greater than the first voltage threshold but less than the second voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value. When the output voltage is greater than the second voltage threshold but less than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the fourth equivalent resonant capacitance value. When the output voltage is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

[0018] In one embodiment, the capacitor adjustment circuit includes a second capacitor and a third capacitor, a fourth switch and a third switch. The second capacitor and the third capacitor are used as adjustment capacitors. The fourth switch has a common terminal, a first switching terminal and a second switching terminal. The common terminal is connected to the resonant capacitor, the first switching terminal is connected to an end of the third capacitor close to the magnetizing inductor, and the second switching terminal is connected to the other end of the third capacitor. The third switch is connected in series with the second capacitor to form a series path. One end of the series path is connected to the resonant capacitor, and the other end of the series path is connected to the first switching terminal and the third capacitor.

[0019] In one embodiment, when the third switch is turned off and the common terminal of the fourth switch is connected to the first switching terminal, when the resonant circuit performs a resonant operation, the first equivalent resonant capacitance value is the capacitance value of the resonant capacitance, and the resonant current flows through the resonant capacitance. When the third switch is turned off and the common terminal of the fourth switch is connected to the second switching terminal, when the resonant circuit performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance connected in series with the third capacitance, and the resonant current flows through the third capacitance and the resonant capacitance. When the third switch is turned on and the common terminal of the fourth switch is connected to the first switching terminal, when the resonant circuit performs a resonant operation, the third equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance connected in parallel with the second capacitance, and the resonant current flows through the resonant capacitance and the second capacitance respectively. When the third switch is turned on and the common terminal of the fourth switch is connected to the second switching terminal, when the resonant circuit performs a resonant operation, the fourth equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitance connected in series with the third capacitance and then connected in parallel with the second capacitance, and the resonant current flows through the third capacitance, the resonant capacitance and the second capacitance respectively.

[0020] In one embodiment, when the capacitance value of the resonant capacitor, the capacitance value of the second capacitor and the capacitance value of the third capacitor are equal, the third equivalent resonant capacitance value is greater than the fourth equivalent resonant capacitance value, the fourth equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value, and the first equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value. When the output voltage is less than the first voltage threshold, the equivalent capacitance value of the resonant circuit is the third equivalent resonant capacitance value. When the output voltage is greater than the first voltage threshold but less than the second voltage threshold, the equivalent capacitance value of the resonant circuit is the fourth equivalent resonant capacitance value. When the output voltage is greater than the second voltage threshold but less than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value. When the output voltage is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

[0021] In one embodiment, the transformer further has an auxiliary winding, and the secondary winding and the auxiliary winding have a turns ratio relationship. The output voltage provides an auxiliary voltage having a turns ratio relationship at the auxiliary winding. The controller receives an auxiliary voltage feedback signal corresponding to the auxiliary voltage magnitude, and controls the first switch and the second switch to be alternately turned on and off according to the auxiliary voltage feedback signal to adjust the output voltage magnitude.

[0022] In one embodiment, the power converter further includes an output voltage detection circuit that receives the output voltage and detects the magnitude of the output voltage to generate an output voltage feedback signal corresponding to the magnitude of the output voltage.

[0023] Thus, the power converter proposed by the present invention has the following features and advantages: 1. In view of the fact that 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 of the resonant capacitor required under the output voltage can be designed in response to different output voltages. 2. In response to the size of the output voltage, the equivalent capacitance value of the resonant circuit is adjusted in real time, and a normal resonant waveform can be obtained, thereby improving efficiency, reducing the voltage surge on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0024] In order to further understand the technology, means and effects adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, characteristics and features of the present invention can be understood in depth and in detail. However, the drawings are only provided for reference and explanation and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : is a circuit block diagram of the power converter of the present invention.

[0026] Figure 2 : is a circuit diagram of the first embodiment of the capacitor adjustment circuit of the power converter of the present invention.

[0027] Figure 3 : is a circuit diagram of a second embodiment of a capacitor adjustment circuit of a power converter of the present invention.

[0028] Figure 4 : is a circuit diagram of the third embodiment of the capacitor adjustment circuit of the power converter of the present invention.

[0029] Figure 5 : is a circuit diagram of a fourth embodiment of a capacitor adjustment circuit of a power converter of the present invention.

[0030] Figure 6 : is a circuit diagram of the auxiliary voltage detection of the power converter of the present invention.

[0031] Wherein, the reference numerals are:

[0032] 100: Power Converter

[0033] TR: Transformer

[0034] 10: Resonant Circuit

[0035] 20: Controller

[0036] 30: Capacitor adjustment circuit

[0037] 40: Output voltage detection circuit

[0038] Q1: First switch

[0039] Q2: Second switch

[0040] Q3: The third switch

[0041] SW4: The fourth switch

[0042] W1: primary winding

[0043] W2: Secondary winding

[0044] Wa: Auxiliary winding

[0045] CR1: Resonant capacitor

[0046] Lm: Magnetizing inductance

[0047] Lk: Leakage inductance

[0048] CR2: Second capacitor

[0049] CR3: The third capacitor

[0050] 0: Common terminal

[0051] 1: First switch end

[0052] 2: Second switch terminal

[0053] Vout: output voltage

[0054] Vaux: Auxiliary voltage

[0055] Svout: output voltage feedback signal

[0056] S1: First signal

[0057] S2: Second signal

[0058] Scc: Capacitor adjustment signal

[0059] Scc1: First capacitor adjustment signal

[0060] Scc2: Second capacitor adjustment signal DETAILED DESCRIPTION

[0061] The technical content and detailed description of the present invention are now described as follows with reference to the accompanying drawings.

[0062] See also Figure 1, which is a circuit block diagram of the power converter of the present invention. The power converter 100 includes a transformer TR, a resonant circuit 10, a first switch Q1, a second switch Q2 and a controller 20. The transformer TR has a primary side winding W1 and a secondary side winding W2 coupled to the primary side winding W1. The resonant circuit 10 couples the primary side winding W1. The resonant circuit 10 includes a resonant capacitor CR1 and a resonant inductor. The resonant inductor is composed of the magnetizing inductance Lm and the leakage inductance Lk of the primary side winding W1. The first switch Q1 and the second switch Q2 are coupled to the resonant circuit 10.

[0063] The controller 20 receives an output voltage feedback signal Svout corresponding to the output voltage Vout of the power converter 100, and controls the first switch Q1 and the second switch Q2 to be alternately turned on and off according to the output voltage feedback signal Svout to adjust the output voltage Vout. In one embodiment, the power converter 100 includes an output voltage detection circuit 40. The output voltage detection circuit 40 receives the output voltage Vout and detects the output voltage Vout to generate an output voltage feedback signal Svout corresponding to the output voltage Vout.

[0064] In addition, see Figure 6 , which is a circuit diagram of the auxiliary voltage detection of the power converter of the present invention. In the present invention, in addition to obtaining the output voltage feedback signal Svout through the output voltage Vout detected at the output side of the power converter 100, the auxiliary voltage feedback signal can also be obtained through the auxiliary winding Wa of the transformer TR, thereby controlling the first switch Q1 and the second switch Q2 to be alternately turned on and off to adjust the output voltage Vout. Specifically, Figure 6 As shown, the transformer TR also has an auxiliary winding Wa, and the secondary winding W2 has a turns ratio relationship with the auxiliary winding Wa, so the auxiliary winding Wa can provide an auxiliary voltage Vaux having a turns ratio relationship with the output voltage Vout. In other words, the controller 20 receives an auxiliary voltage feedback signal corresponding to the magnitude of the auxiliary voltage Vaux, and controls the first switch Q1 and the second switch Q2 to be alternately turned on and off according to the auxiliary voltage feedback signal to adjust the magnitude of the output voltage Vout. Among them, the technical concept of the auxiliary voltage feedback signal is similar to and connected to the output voltage feedback signal Svout, so it will not be repeated.

[0065] In one embodiment of the present invention, the power converter 100 further includes a capacitor adjustment circuit 30. The capacitor adjustment circuit 30 has an adjustment capacitor (described in detail later) and is coupled to the resonant capacitor CR1. The controller 20 controls the connection relationship between the adjustment capacitor and the resonant capacitor CR1 (described in detail later) according to the output voltage feedback signal Svout to determine the equivalent resonant capacitance value of the resonant circuit 10. When the output voltage Vout increases, the equivalent resonant capacitance value is controlled to decrease; conversely, when the output voltage Vout decreases, the equivalent resonant capacitance value is controlled to increase.

[0066] like Figure 1 As shown, the controller 20 provides a first signal S1, a second signal S2 and a capacitance adjustment signal Scc to respectively control the first switch Q1, the second switch Q2 and the capacitance adjustment circuit 30. That is, the first signal S1 controls the on or off of the first switch Q1; the second signal S2 controls the on or off of the second switch Q2; and the capacitance adjustment signal Scc controls the switching of the capacitance adjustment circuit 30 (to be described in detail later).

[0067] See also Figure 2 , which is a circuit diagram of a first embodiment of a capacitor adjustment circuit of a power converter of the present invention. The capacitor adjustment circuit 30 includes a second capacitor CR2 and a third switch Q3. The second capacitor CR2 is used as the adjustment capacitor. The third switch Q3 is connected in series with the second capacitor CR2 to form a series path, wherein the series path is connected in parallel with the resonant capacitor CR1.

[0068] When the capacitance adjustment signal Scc controls the third switch Q3 to be turned off, and the resonant circuit 10 performs a resonant operation (but this is not limiting, and the resonant circuit 10 performs a resonant operation as an example), the first equivalent resonant capacitance value is the capacitance value of the resonant capacitor CR1, and the resonant current only flows through the resonant capacitor CR1.

[0069] When the capacitance adjustment signal Scc controls the third switch Q3 to be turned on and the resonant circuit 10 performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the second capacitor CR2 in parallel (indicated by the symbol / / , the same will be omitted below), and the resonant current flows through the resonant capacitor CR1 and the second capacitor CR2 respectively.

[0070] For convenience of explanation, in this embodiment, it is assumed that the capacitance value of the resonant capacitor CR1 is equal to the capacitance value of the second capacitor CR2, so the second equivalent resonant capacitance value (i.e., CR1 / / CR2) is greater than the first equivalent resonant capacitance value (i.e., CR1). When the output voltage Vout is less than the voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the second equivalent resonant capacitance value; conversely, when the output voltage Vout is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the first equivalent resonant capacitance value. For example, but not to limit the present invention, when the output voltage is 36V, the capacitance value of the resonant capacitor CR1 can be designed to be 0.32uF; when the output voltage is 5V, the capacitance value of the resonant capacitor CR1 can be designed to be 1.04uF. In this way, the equivalent capacitance value of the resonant circuit 10 can be adjusted in real time according to the size of the output voltage Vout. When the output voltage Vout increases, the capacitance value of the resonant capacitor is adjusted to decrease. Conversely, when the output voltage Vout decreases, the capacitance value of the resonant capacitor is adjusted to increase, thereby improving efficiency, reducing voltage surges on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0071] See also Figure 3 , which is a circuit diagram of a second embodiment of a capacitor adjustment circuit of a power converter of the present invention. The capacitor adjustment circuit 30 includes a third capacitor CR3 and a fourth switch SW4. The third capacitor CR3 is used as the adjustment capacitor. The fourth switch SW4 has a common terminal 0, a first switching terminal 1, and a second switching terminal 2. The common terminal 0 is connected to the resonant capacitor CR1, the first switching terminal 1 is connected to one end of the third capacitor CR3 (close to the magnetizing inductor Lm), and the second switching terminal 2 is connected to the other end of the third capacitor CR3 (away from the magnetizing inductor Lm).

[0072] When the capacitance adjustment signal Scc controls the common terminal 0 of the fourth switch SW4 to be connected to the first switching terminal 1, and the resonant circuit 10 performs a resonant operation (but this is not limiting, and the resonant operation of the resonant circuit 10 is only taken as an example for explanation), the first equivalent resonant capacitance value is the capacitance value of the resonant capacitor CR1, and the resonant current only flows through the resonant capacitor CR1.

[0073] When the capacitance adjustment signal Scc controls the common terminal 0 of the fourth switch SW4 to be connected to the second switching terminal 2, and the resonant circuit 10 performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the third capacitor CR3 connected in series (indicated by the symbol +, the same will be omitted below), and the resonant current flows through the third capacitor CR3 and the resonant capacitor CR1.

[0074] For the convenience of explanation, in this embodiment, it is assumed that the capacitance value of the resonant capacitor CR1 is equal to the capacitance value of the third capacitor CR3, so the first equivalent resonant capacitance value (i.e., CR1) is greater than the second equivalent resonant capacitance value (i.e., CR1+CR3). When the output voltage Vout is less than the voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the first equivalent resonant capacitance value; conversely, when the output voltage Vout is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the second equivalent resonant capacitance value. In this way, the equivalent capacitance value of the resonant circuit 10 can be adjusted in real time in response to the size of the output voltage Vout. When the output voltage Vout increases, the capacitance value of the resonant capacitor is adjusted to decrease. Conversely, when the output voltage Vout decreases, the capacitance value of the resonant capacitor is adjusted to increase, thereby improving efficiency, reducing voltage surges on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0075] See also Figure 4 As shown, it is a circuit diagram of the third embodiment of the capacitor adjustment circuit of the power converter of the present invention. The capacitor adjustment circuit 30 includes a second capacitor CR2, a third capacitor CR3, a third switch Q3 and a fourth switch SW4. The second capacitor CR2 and the third capacitor CR3 are used as the adjustment capacitor. The third switch Q3 is connected in series with the second capacitor CR2 to form a series path, wherein the series path is connected in parallel with the resonant capacitor CR1. The fourth switch SW4 has a common terminal 0, a first switching terminal 1 and a second switching terminal 2. The common terminal 0 is connected to the resonant capacitor CR1 and the second capacitor CR2, the first switching terminal 1 is connected to one end of the third capacitor CR3 (close to the excitation inductor Lm), and the second switching terminal 2 is connected to the other end of the third capacitor CR3 (far away from the excitation inductor Lm).

[0076] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned off and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the first switching terminal 1, and the resonant circuit 10 performs a resonant operation (but this is not a limitation, and the resonant operation of the resonant circuit 10 is only used as an example for explanation), the first equivalent resonant capacitance value is the capacitance value of the resonant capacitor CR1, and the resonant current only flows through the resonant capacitor CR1.

[0077] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned off and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the second switching terminal 2, when the resonant circuit 10 performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the third capacitor CR3 connected in series, and the resonant current flows through the third capacitor CR3 and the resonant capacitor CR1.

[0078] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned on and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the first switching terminal 1, when the resonant circuit 10 performs a resonant operation, the third equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the second capacitor CR2 in parallel, and the resonant current flows through the resonant capacitor CR1 and the second capacitor CR2 respectively.

[0079] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned on and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the second switching terminal 2, when the resonant circuit 10 performs a resonant operation, the fourth equivalent resonant capacitance value is the equivalent capacitance value of the resonant capacitor CR1 connected in parallel with the second capacitor CR2 and then connected in series with the third capacitor CR3, and the resonant current flows through the third capacitor CR3 and respectively flows through the resonant capacitor CR1 and the second capacitor CR2.

[0080] For convenience of explanation, in this embodiment, it is assumed that the capacitance value of the resonant capacitor CR1, the capacitance value of the second capacitor CR2, and the capacitance value of the third capacitor CR3 are equal, so the third equivalent resonant capacitance value (i.e., CR1 / / CR2) is greater than the first equivalent resonant capacitance value (i.e., CR1), the first equivalent resonant capacitance value is greater than the fourth equivalent resonant capacitance value (i.e., (CR1 / / CR2)+CR3), and the fourth equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value (i.e., CR1+CR3).

[0081] When the output voltage Vout is less than the first voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the third equivalent resonant capacitance value. When the output voltage Vout is greater than the first voltage threshold but less than the second voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the first equivalent resonant capacitance value. When the output voltage Vout is greater than the second voltage threshold but less than the third voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the fourth equivalent resonant capacitance value. When the output voltage Vout is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the second equivalent resonant capacitance value. In this way, the equivalent capacitance value of the resonant circuit 10 can be adjusted in real time in response to the size of the output voltage Vout. When the output voltage Vout increases, the capacitance value of the resonant capacitor is adjusted to decrease. Conversely, when the output voltage Vout decreases, the capacitance value of the resonant capacitor is adjusted to increase, thereby improving efficiency, reducing voltage surges on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0082] See also Figure 5As shown, it is a circuit diagram of the fourth embodiment of the capacitor adjustment circuit of the power converter of the present invention. The capacitor adjustment circuit 30 includes a second capacitor CR2, a third capacitor CR3, a fourth switch SW4 and a third switch Q3. The second capacitor CR2 and the third capacitor CR3 are used as the adjustment capacitor. The fourth switch SW4 has a common terminal 0, a first switching terminal 1 and a second switching terminal 2. The common terminal 0 is connected to the resonant capacitor CR1, the first switching terminal 1 is connected to one end of the third capacitor CR3 (close to the excitation inductor Lm), and the second switching terminal 2 is connected to the other end of the third capacitor CR3 (away from the excitation inductor Lm).

[0083] The third switch Q3 is connected in series with the second capacitor CR2 to form a series path, wherein one end of the series path (away from the magnetizing inductor Lm) is connected to the resonant capacitor CR1, and the other end of the series path (close to the magnetizing inductor Lm) is connected to the first switch terminal 1 and the third capacitor CR3.

[0084] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned off and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the first switching terminal 1, and the resonant circuit 10 performs a resonant operation (but this is not a limitation, and the resonant operation of the resonant circuit 10 is only used as an example for explanation), the first equivalent resonant capacitance value is the capacitance value of the resonant capacitor CR1, and the resonant current only flows through the resonant capacitor CR1.

[0085] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned off and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the second switching terminal 2, when the resonant circuit 10 performs a resonant operation, the second equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the third capacitor CR3 connected in series, and the resonant current flows through the third capacitor CR3 and the resonant capacitor CR1.

[0086] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned on and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the first switching terminal 1, when the resonant circuit 10 performs a resonant operation, the third equivalent resonant capacitance value is the equivalent capacitance value of the capacitance value of the resonant capacitor CR1 and the second capacitor CR2 in parallel, and the resonant current flows through the resonant capacitor CR1 and the second capacitor CR2 respectively.

[0087] When the first capacitance adjustment signal Scc1 controls the third switch Q3 to be turned on and the second capacitance adjustment signal Scc2 controls the common terminal 0 of the fourth switch SW4 to be connected to the second switching terminal 2, when the resonant circuit 10 performs a resonant operation, the fourth equivalent resonant capacitance value is the equivalent capacitance value of the resonant capacitor CR1 connected in series with the third capacitor CR3 and then connected in parallel with the second capacitor CR2, and the resonant current flows through the third capacitor CR3, the resonant capacitor CR1 and the second capacitor CR2.

[0088] For convenience of explanation, in this embodiment, it is assumed that the capacitance value of the resonant capacitor CR1, the capacitance value of the second capacitor CR2, and the capacitance value of the third capacitor CR3 are equal, so the third equivalent resonant capacitance value (i.e., CR1 / / CR2) is greater than the fourth equivalent resonant capacitance value (i.e., (CR1+CR3) / / CR2), the fourth equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value (i.e., CR1), and the first equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value (i.e., CR1+CR3).

[0089] When the output voltage Vout is less than the first voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the third equivalent resonant capacitance value. When the output voltage Vout is greater than the first voltage threshold but less than the second voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the fourth equivalent resonant capacitance value. When the output voltage Vout is greater than the second voltage threshold but less than the third voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the first equivalent resonant capacitance value. When the output voltage Vout is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit 10 is the second equivalent resonant capacitance value. In this way, the equivalent capacitance value of the resonant circuit 10 can be adjusted in real time in response to the size of the output voltage Vout. When the output voltage Vout increases, the capacitance value of the resonant capacitor is adjusted to decrease. Conversely, when the output voltage Vout decreases, the capacitance value of the resonant capacitor is adjusted to increase, thereby improving efficiency, reducing voltage surges on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0090] In summary, the present invention has the following features and advantages:

[0091] 1. In view of the fact that the capacitance value of a single resonant capacitor cannot be compatible with the capacitance value 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 of the resonant capacitor required under the output voltage can be designed in response to different output voltages.

[0092] 2. According to the size of the output voltage, the equivalent capacitance value of the resonant circuit is adjusted in real time to obtain a normal resonant waveform, thereby improving efficiency, reducing the voltage surge on the resonant capacitor, and reducing the current flowing through the transistor to avoid damage to the transistor.

[0093] The above description is only a detailed description and drawings of the preferred specific embodiments of the present invention. The features of the present invention are not limited thereto and are not intended to limit the present invention. The entire scope of the present invention shall be subject to the following patent application scope. All embodiments that conform to the spirit of the patent application scope of the present invention and similar variations thereof shall be included in the scope of the present invention. Any changes or modifications that can be easily conceived by a person familiar with the art within the field of the present invention shall be covered by the following patent scope of this case.

Claims

1. A power converter, characterized in that: include: A transformer having a primary winding and a secondary winding coupled to the primary winding; a resonant circuit coupled to the primary winding, the resonant circuit comprising a resonant capacitor and a resonant inductor, wherein the resonant inductor is composed of a magnetizing inductance and a leakage inductance of the primary winding; A first switch and a second switch, the first switch and the second switch are coupled to the resonant circuit; as well as A controller receives an output voltage feedback signal corresponding to an output voltage of the power converter, and controls the first switch and the second switch to be alternately turned on and off according to the output voltage feedback signal to adjust the output voltage.

2. The power converter according to claim 1, wherein: Also includes: A capacitance adjustment circuit has an adjustment capacitor coupled to the resonant capacitor; The controller controls the connection relationship between the adjustment capacitor and the resonant capacitor according to the output voltage feedback signal to determine an equivalent resonant capacitance value of the resonant circuit.

3. The power converter according to claim 2, wherein: When the output voltage increases, the equivalent resonant capacitance value is controlled to decrease; when the output voltage decreases, the equivalent resonant capacitance value is controlled to increase.

4. The power converter according to claim 2, wherein: The controller provides a first signal, a second signal and a capacitance adjustment signal to control the first switch, the second switch and the capacitance adjustment circuit respectively.

5. The power converter according to claim 2, wherein: The capacitance adjustment circuit comprises: a second capacitor, used as the adjustment capacitor; and A third switch is connected in series with the second capacitor to form a series path; wherein the series path is connected in parallel with the resonant capacitor.

6. The power converter according to claim 5, wherein: When the third switch is turned off and the resonant circuit performs a resonant operation, a first equivalent resonant capacitance value is the capacitance value of the resonant capacitor, and a resonant current flows through the resonant capacitor; When the third switch is turned on and the resonant circuit performs a resonant operation, a second equivalent resonant capacitance value is an equivalent capacitance value of the resonant capacitor and the second capacitor in parallel, and the resonant current flows through the resonant capacitor and the second capacitor respectively.

7. The power converter according to claim 6, wherein: When the capacitance value of the resonant capacitor is equal to the capacitance value of the second capacitor, the second equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value; When the output voltage is less than a voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value; when the output voltage is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value.

8. The power converter according to claim 2, wherein: The capacitance adjustment circuit comprises: a third capacitor, used as the adjustment capacitor; and A fourth switch has a common terminal, a first switching terminal and a second switching terminal; wherein the common terminal is connected to the resonant capacitor, the first switching terminal is connected to an end of the third capacitor close to the magnetizing inductor, and the second switching terminal is connected to the other end of the third capacitor.

9. The power converter according to claim 8, wherein: When the common terminal of the fourth switch is connected to the first switching terminal and the resonant circuit performs a resonant operation, a first equivalent resonant capacitance value is the capacitance value of the resonant capacitor, and a resonant current flows through the resonant capacitor; When the common end of the fourth switch is connected to the second switching end and the resonant circuit performs a resonant operation, a second equivalent resonant capacitance value is an equivalent capacitance value of the capacitance value of the resonant capacitor and the third capacitor in series, and the resonant current flows through the third capacitor and the resonant capacitor.

10. The power converter according to claim 9, wherein: When the capacitance value of the resonant capacitor is equal to the capacitance value of the third capacitor, the first equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value; When the output voltage is less than a voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value; when the output voltage is greater than the voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

11. The power converter according to claim 2, wherein: The capacitance adjustment circuit comprises: A second capacitor and a third capacitor are used as the adjustment capacitor; a third switch connected in series with the second capacitor to form a series path; wherein the series path is connected in parallel with the resonant capacitor; and A fourth switch has a common terminal, a first switching terminal and a second switching terminal; wherein the common terminal is connected to the resonant capacitor and the second capacitor, the first switching terminal is connected to an end of the third capacitor close to the magnetizing inductor, and the second switching terminal is connected to the other end of the third capacitor.

12. The power converter according to claim 11, wherein: When the third switch is turned off and the common terminal of the fourth switch is connected to the first switching terminal, the resonant circuit performs a resonant operation, a first equivalent resonant capacitance value is the capacitance value of the resonant capacitor, and a resonant current flows through the resonant capacitor; When the third switch is turned off and the common terminal of the fourth switch is connected to the second switch terminal, the resonant circuit performs a resonant operation, a second equivalent resonant capacitance value is an equivalent capacitance value of the capacitance value of the resonant capacitor and the third capacitor in series, and the resonant current flows through the third capacitor and the resonant capacitor; When the third switch is turned on and the common terminal of the fourth switch is connected to the first switching terminal, the resonant circuit performs a resonant operation, a third equivalent resonant capacitance value is an equivalent capacitance value of the capacitance value of the resonant capacitor and the second capacitor in parallel, and the resonant current flows through the resonant capacitor and the second capacitor respectively; When the third switch is turned on and the common end of the fourth switch is connected to the second switching end, the resonant circuit performs a resonant operation, a fourth equivalent resonant capacitance value is an equivalent capacitance value of the resonant capacitor connected in parallel with the second capacitor and then connected in series with the third capacitor, and the resonant current flows through the third capacitor and respectively flows through the resonant capacitor and the second capacitor.

13. The power converter according to claim 12, wherein: When the capacitance value of the resonant capacitor, the capacitance value of the second capacitor, and the capacitance value of the third capacitor are equal, the third equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value, the first equivalent resonant capacitance value is greater than the fourth equivalent resonant capacitance value, and the fourth equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value; When the output voltage is less than a first voltage threshold, the equivalent capacitance value of the resonant circuit is the third equivalent resonant capacitance value; when the output voltage is greater than the first voltage threshold but less than a second voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value; when the output voltage is greater than the second voltage threshold but less than a third voltage threshold, the equivalent capacitance value of the resonant circuit is the fourth equivalent resonant capacitance value; when the output voltage is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

14. The power converter according to claim 2, wherein: The capacitance adjustment circuit comprises: A second capacitor and a third capacitor are used as the adjustment capacitor; a fourth switch having a common terminal, a first switching terminal and a second switching terminal; wherein the common terminal is connected to the resonant capacitor, the first switching terminal is connected to an end of the third capacitor close to the magnetizing inductor, and the second switching terminal is connected to the other end of the third capacitor; and A third switch is connected in series with the second capacitor to form a series path; wherein one end of the series path is connected to the resonant capacitor, and the other end of the series path is connected to the first switch end and the third capacitor.

15. The power converter according to claim 14, wherein: When the third switch is turned off and the common terminal of the fourth switch is connected to the first switching terminal, the resonant circuit performs a resonant operation, a first equivalent resonant capacitance value is the capacitance value of the resonant capacitor, and a resonant current flows through the resonant capacitor; When the third switch is turned off and the common terminal of the fourth switch is connected to the second switch terminal, the resonant circuit performs a resonant operation, a second equivalent resonant capacitance value is an equivalent capacitance value of the capacitance value of the resonant capacitor and the third capacitor in series, and the resonant current flows through the third capacitor and the resonant capacitor; When the third switch is turned on and the common terminal of the fourth switch is connected to the first switching terminal, the resonant circuit performs a resonant operation, a third equivalent resonant capacitance value is an equivalent capacitance value of the capacitance value of the resonant capacitor and the second capacitor in parallel, and the resonant current flows through the resonant capacitor and the second capacitor respectively; When the third switch is turned on and the common end of the fourth switch is connected to the second switching end, the resonant circuit performs a resonant operation, a fourth equivalent resonant capacitance value is an equivalent capacitance value of the resonant capacitor connected in series with the third capacitor and then in parallel with the second capacitor, and the resonant current flows through the third capacitor, the resonant capacitor and the second capacitor respectively.

16. The power converter according to claim 15, wherein: When the capacitance value of the resonant capacitor, the capacitance value of the second capacitor, and the capacitance value of the third capacitor are equal, the third equivalent resonant capacitance value is greater than the fourth equivalent resonant capacitance value, the fourth equivalent resonant capacitance value is greater than the first equivalent resonant capacitance value, and the first equivalent resonant capacitance value is greater than the second equivalent resonant capacitance value; When the output voltage is less than a first voltage threshold, the equivalent capacitance value of the resonant circuit is the third equivalent resonant capacitance value; when the output voltage is greater than the first voltage threshold but less than a second voltage threshold, the equivalent capacitance value of the resonant circuit is the fourth equivalent resonant capacitance value; when the output voltage is greater than the second voltage threshold but less than a third voltage threshold, the equivalent capacitance value of the resonant circuit is the first equivalent resonant capacitance value; when the output voltage is greater than the third voltage threshold, the equivalent capacitance value of the resonant circuit is the second equivalent resonant capacitance value.

17. The power converter according to claim 1, wherein: The transformer also has an auxiliary winding, and the secondary winding has a turns ratio relationship with the auxiliary winding; the auxiliary winding provides an auxiliary voltage having the turns ratio relationship with the output voltage; The controller receives an auxiliary voltage feedback signal corresponding to the auxiliary voltage, and controls the first switch and the second switch to be turned on and off alternately according to the auxiliary voltage feedback signal to adjust the output voltage.

18. The power converter according to claim 1, wherein: Also includes: An output voltage detection circuit receives the output voltage and detects the magnitude of the output voltage to generate an output voltage feedback signal corresponding to the magnitude of the output voltage.

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