Power converter and control method thereof

Abstract

The invention discloses a power converter and a control method thereof. The power converter comprises a transformer, a resonance circuit, a first switch, a second switch, a resonance adjusting circuit 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 comprises a resonant capacitor and a resonant inductor provided by at least the primary side winding. The first switch and the second switch are commonly connected to a node, and the node is coupled to the resonant circuit. The resonance adjusting circuit is coupled to the resonance circuit. The controller controls the enabling time of the resonance adjusting circuit according to the magnitude of the output voltage of the power converter, so that the transmission efficiency of the energy transmitted from the primary side winding to the secondary side winding is maintained in a full output voltage range.

Description

Technical Field

[0001] The present invention relates to a power converter and a control method thereof, and more particularly to a power converter and a control method thereof that instantaneously adjust the resonance characteristics in the full output voltage range. Background Art

[0002] Under the application of the USB PD3.1 fast charging standard, the charging power is increased from the original 100W to 240W, and a maximum voltage output of 48V is supported. Therefore, the power supply needs to provide a voltage change of 5 to 48V. For the asymmetric half-bridge (AHB) architecture, its advantages of variable voltage begin to emerge. The asymmetric half-bridge flyback converter combines the advantages of zero-voltage switching on the primary side of the LLC resonant circuit architecture and wide voltage output of the flyback architecture, and is suitable for power conversion applications with high switching frequencies.

[0003] However, the inability to achieve high-efficiency operation in the full output voltage range is a problem and a technical bottleneck worthy of attention. Therefore, to solve the foregoing problems, a method of adding a parallel capacitor has been adopted. However, such a method is only suitable for higher efficiency at a single output voltage and still cannot achieve better conversion efficiency operation in the full output voltage range.

[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 by the inventors of this case. Summary of the Invention

[0005] In view of the deficiencies of the prior art, an object of the present invention is to provide a power converter, including a transformer, a resonant circuit, a first switch and a second switch, a resonance adjustment circuit, 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, and the resonant circuit includes a resonant capacitor and at least a resonant inductor provided by the primary side winding. The first switch and the second switch are commonly connected to a node, and the node is coupled to the resonant circuit. The resonance adjustment circuit is coupled to the resonant circuit. The controller controls the energization time of the resonance adjustment circuit according to the magnitude of the output voltage of the power converter, so as to maintain the transmission efficiency of the energy transmitted from the primary side winding to the secondary side winding in the full output voltage range.

[0006] In an embodiment, the resonance adjustment circuit includes an adjustment capacitor and an adjustment switch. The adjustment capacitor has a first end and a second end, and the first end of the adjustment capacitor is coupled to the resonant capacitor; wherein the adjustment capacitor and the resonant capacitor form an equivalent capacitor. The adjustment switch has a first power supply terminal, a second power supply terminal, and a control terminal; wherein the first power supply terminal is coupled to the second end of the adjustment capacitor, and the second power supply terminal is coupled to the second switch.

[0007] In one embodiment, the power converter further includes a current detection unit and a voltage detection unit. The current detection unit is coupled to the resonant capacitor and the regulating capacitor to detect the magnitude of the current flowing through the equivalent capacitor, so as to generate a current signal. The voltage detection unit is coupled to the first power terminal of the regulating switch to detect the switching voltage on the regulating switch.

[0008] In one embodiment, the controller controls the conduction and turn-off of the regulating switch according to the first control signal for controlling the first switch, the second control signal for controlling the second switch, the current signal corresponding to the current flowing through the equivalent capacitor, and the switching voltage on the regulating switch.

[0009] In one embodiment, when the regulating switch is turned off, the capacitance value of the equivalent capacitor is the capacitance value of the resonant capacitor; when the regulating switch is turned on, the capacitance value of the equivalent capacitor is the equivalent capacitance value after the resonant capacitor and the regulating capacitor are connected in parallel.

[0010] In one embodiment, the controller obtains a charging control signal according to the current signal and the first control signal, obtains a discharging control signal according to the switching voltage and the second control signal, and generates a switching control signal according to the charging control signal and the discharging control signal to control the conduction and turn-off of the regulating switch.

[0011] In one embodiment, the charging control signal is obtained by taking the intersection of the voltage compensation signal generated after compensating the current error signal between the current signal and the current reference value and the first control signal; the discharging control signal is obtained by taking the intersection of the voltage comparison signal generated after comparing the switching voltage with the voltage reference value and the second control signal.

[0012] In one embodiment, the controller includes a calculation unit, a compensation unit, a first AND operation unit, a comparison unit, a second AND operation unit, and an OR operation unit. The calculation unit receives the current signal and the current reference value, and calculates the current error signal according to the current signal and the current reference value. The compensation unit receives the current error signal and compensates the current error signal to generate a voltage compensation signal. The first AND operation unit receives the voltage compensation signal and the first control signal, and performs a logical AND operation on the voltage compensation signal and the first control signal to generate a charging control signal. The comparison unit receives the switching voltage and the voltage reference value, and compares the switching voltage and the voltage reference value to generate a voltage comparison signal. The second AND operation unit receives the voltage comparison signal and the second control signal, and performs a logical AND operation on the voltage comparison signal and the second control signal to generate a discharging control signal. The OR operation unit receives the charging control signal and the discharging control signal, and performs a logical OR operation on the charging control signal and the discharging control signal to generate a switching control signal.

[0013] Another object of the present invention is to provide a control method for a power converter, the power converter including a first switch and a second switch, a resonant capacitor, and a resonant adjustment circuit, wherein the resonant adjustment circuit includes an adjustment capacitor and an adjustment switch. The control method includes: detecting the magnitude of the current flowing through an equivalent capacitor formed by the resonant capacitor and the adjustment capacitor to generate a current signal; detecting the switch voltage on the adjustment switch; obtaining a first control signal for controlling the first switch and a second control signal for controlling the second switch; and when the magnitude of the output voltage of the power converter changes, controlling the energization time of the resonant adjustment circuit according to the current signal, the switch voltage, and the first control signal and the second control signal, so as to maintain the transmission efficiency of the energy transmitted from the primary side winding to the secondary side winding within the full output voltage range.

[0014] In one embodiment, in the step of controlling the energization time of the resonant adjustment circuit, the conduction and cutoff of the adjustment switch are controlled according to the current signal, the switch voltage, and the first control signal and the second control signal to control the energization time of the resonant adjustment circuit.

[0015] In one embodiment, when the adjustment switch is cutoff, the capacitance value of the equivalent capacitor is the capacitance value of the resonant capacitor; when the adjustment switch is conducting, the capacitance value of the equivalent capacitor is the equivalent capacitance value after the resonant capacitor and the adjustment capacitor are connected in parallel.

[0016] In one embodiment, a charging control signal is obtained according to the current signal and the first control signal, a discharging control signal is obtained according to the switch voltage and the second control signal, and a switch control signal is generated according to the charging control signal and the discharging control signal to control the conduction and cutoff of the adjustment switch.

[0017] In one embodiment, the intersection of the voltage compensation signal generated after compensating the current error signal between the current signal and the current reference value and the first control signal obtains the charging control signal; the intersection of the voltage comparison signal generated after comparing the switch voltage with the voltage reference value and the second control signal obtains the discharging control signal.

[0018] In one embodiment, the control method further includes: providing a computing unit to receive a current signal and a current reference value, and calculating a current error signal based on the current signal and the current reference value; providing a compensation unit to receive the current error signal and compensating the current error signal to generate a voltage compensation signal; providing a first AND operation unit to receive the voltage compensation signal and a first control signal, and performing a logical AND operation on the voltage compensation signal and the first control signal to generate a charging control signal; providing a comparison unit to receive a switch voltage and a voltage reference value, and comparing the switch voltage with the voltage reference value to generate a voltage comparison signal; providing a second AND operation unit to receive the voltage comparison signal and a second control signal, and performing a logical AND operation on the voltage comparison signal and the second control signal to generate a discharging control signal; and providing an OR operation unit to receive the charging control signal and the discharging control signal, and performing a logical OR operation on the charging control signal and the discharging control signal to generate a switch control signal.

[0019] Therefore, the power converter and its control method proposed by the present invention have the following features and advantages:

[0020] The present invention can dynamically adjust the time length of the resonant operation and the starting timing of the resonant compensation at any voltage within the full output voltage range, not only achieving the real-time performance of on-line resonant compensation, but also accurately achieving the integrity of the resonant compensation.

[0021] By controlling and adjusting the capacitor to be incorporated into the resonant capacitor, the present invention can extend the discharge time of the equivalent capacitor at a resonant current with a lower current peak, not only reducing the component losses on the secondary side to improve the efficiency, but also enabling the selection of smaller current-carrying components to reduce the circuit cost.

[0022] The present invention can ensure zero-voltage switching (ZVS) for turning on the regulating switch in a zero-voltage state to reduce switching losses.

[0023] After completing the capacitor compensation operation, the present invention can provide the timing for zero-voltage switching control for the high-side switch (i.e., the first switch) and the low-side switch (i.e., the second switch).

[0024] To further understand the technologies, 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, features, and characteristics of the present invention can be deeply and specifically understood therefrom. However, the drawings are only for reference and explanation, and are not used to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a circuit block diagram of an asymmetric half-bridge flyback converter;

[0026] Figure 2Voltage waveforms, current waveforms, and control signal waveforms related to the operation of an asymmetric half-bridge flyback converter;

[0027] Figure 3 Waveform diagrams of the current in the main inductor and the resonant current during the operation of an asymmetric half-bridge flyback converter;

[0028] Figure 4 Circuit block diagram of the power converter of the present invention;

[0029] Figure 5 Circuit block diagram of the controller of the power converter of the present invention;

[0030] Figure 6 Voltage waveforms, current waveforms, and control signal waveforms related to the operation of the power converter of the present invention;

[0031] Figure 7 Flowchart of the operation method of the power converter of the present invention;

[0032] Among them, reference numerals:

[0033] 100: Power converter; TR: Transformer;

[0034] 10: Resonant circuit; 20: Resonant adjustment circuit;

[0035] 30: Controller; 31: Calculation unit;

[0036] 32: Compensation unit; 33: First AND operation unit;

[0037] 34: Comparison unit; 35: Second AND operation unit;

[0038] 36: OR operation unit; 41: Current detection unit;

[0039] 42: Voltage detection unit; CR1: Resonant capacitor;

[0040] CR2: Adjustment capacitor; CR: Equivalent capacitor;

[0041] S1: First switch; S2: Second switch;

[0042] QCR: Adjustment switch; Si: Current signal;

[0043] Scr: Switch control signal;

[0044] W1: Primary side winding; W2: Secondary side winding;

[0045] Ns: Node; Vo: Output voltage;

[0046] VQCR: Switching voltage; SQ1: First control signal;

[0047] SQ2: Second control signal; Schg: Charge control signal;

[0048] Sdischg: Discharge control signal; Iref: Current reference value;

[0049] Serr: Current error signal; Scmps: Voltage compensation signal;

[0050] Vref: Voltage reference value; Scmpr: Voltage comparison signal;

[0051] S10 - S40: Steps. Detailed implementation mode

[0052] The technical content and detailed description of the present invention are described below in conjunction with the accompanying drawings.

[0053] Please refer to Figure 1 and Figure 2 , which are respectively the circuit block diagram of the asymmetric half - bridge flyback converter and the relevant voltage waveforms, current waveforms, and control signal waveforms during the operation of the asymmetric half - bridge flyback converter. When the high - side switch HS is turned on, the input voltage Vin charges the main inductor (i.e., the magnetizing inductor) of the transformer TR and the resonant capacitor Cr. Therefore, the current Imag flowing through the main inductor gradually increases, and the current magnetization is like the current waveform of a flyback converter. When the low - side switch LS is turned on, energy is transferred from the resonant capacitor Cr on the primary side of the transformer TR to the secondary side of the transformer TR, and the waveform of its resonant current Icr is like the half - sine - wave current waveform of a resonant converter.

[0054] Due to the characteristic of the wide output voltage, it will affect the conduction time of the low - side switch LS. Because in this operation, the magnetizing inductor will be clamped at nVo (i.e., n times the output voltage) for leakage magnetic flux. Since n is a fixed parameter (where n is the turns ratio of the secondary winding to the primary winding of the transformer TR), the formula at this time is as follows:

[0055] L*(di / dt) = V;

[0056] It can be rewritten as dt = L*di / nVo.

[0057] According to the above formula, it can be known that when the output voltage Vo changes, the dt time (i.e., the leakage magnetic flux time) will change. For exampleFigure 3 As shown, it is a schematic diagram of the waveforms of the current in the main inductor and the resonant current during the operation of an asymmetric half-bridge flyback converter. For example, Imag1 is the waveform of the current in the main inductor when the output voltage Vo is 20V, that is, the waveform when the output voltage Vo is relatively small, and Imag4 is the waveform of the current in the main inductor when the output voltage Vo is 48V, that is, the waveform when the output voltage Vo is relatively large. Therefore, when the output voltage Vo is lower, the time of magnetic leakage will increase significantly.

[0058] Regarding the resonant current Icr, when the resonant capacitor Cr has a fixed capacitance value, once the time of magnetic leakage is longer, since the energy stored in the resonant capacitor Cr is released prematurely, it will cause the primary-side current to flow through the charging resonant capacitor and then be transferred to the secondary side. In this way, the energy transfer efficiency will be greatly reduced, resulting in a decrease in efficiency. As Figure 3 Shown in Imag1 and Icr, when the resonant capacitor Cr releases all its electricity, the current in the main inductor (primary-side current) still needs to pass through the period T1 to completely transfer the energy to the secondary side. Thus, losses will occur during the operation in the period T1 after the resonant state ends, leading to a decrease in efficiency. The same situation also exists in the current relationship between Imag2 and Icr, and losses will also occur during the operation in the period T2 after the resonant state ends. However, for the current relationship between Imag4 and Icr, it will cause the low-side switch LS to turn off prematurely, resulting in switching loss, which will also lead to a decrease in efficiency. Therefore, achieving the current relationship between Imag3 and Icr for the current in the main inductor and the resonant current is the best and highly efficient operation.

[0059] Please refer to Figure 4 Shown, it is a circuit block diagram of the power converter of the present invention. As Figure 4 Shown, the power converter 100 includes a transformer TR, a resonant circuit 10, a first switch Q1 and a second switch Q2, a resonant adjustment circuit 20, and a controller 30.

[0060] The transformer TR includes a primary-side winding W1 and a secondary-side winding W2 coupled to the primary-side winding W1, which isolates the primary-side circuit and the secondary-side circuit, and the voltage coupled to the secondary-side winding W2 is proportional to the turns ratio between the number of turns Ns of the secondary-side winding W2 and the number of turns Np of the primary-side winding W1, that is, Ns / Np.

[0061] The resonant circuit 10 is coupled to the primary-side winding W1. The resonant circuit 10 includes a resonant capacitor CR1 and a resonant inductor, where the resonant inductor provides at least the inductance for the primary-side winding W1. In other words, the resonant inductor can include the equivalent inductance formed by the primary-side leakage inductance and the magnetizing inductance.

[0062] In this embodiment, the first switch Q1 and the second switch Q2 can also be respectively referred to as a high-side switch and a low-side switch. The first switch Q1 and the second switch Q2 are commonly connected to a node Ns, and the node Ns is coupled to the resonant circuit 10. The on and off control of the first switch Q1 and the second switch Q2 is in a complementary relationship, that is, when the first switch Q1 is on, the second switch Q2 is in an off state, and vice versa, when the first switch Q1 is off, the second switch Q2 is in an on state. When the first switch Q1 is on, it is used for a charging operation (i.e., the energy storage operation of the resonant capacitor CR1), and when the second switch Q2 is on, it is used for a discharging operation (i.e., the energy release operation of the resonant capacitor CR1).

[0063] The resonance adjustment circuit 20 is coupled to the resonant circuit 10. As Figure 4 shown, the resonance adjustment circuit 20 includes an adjustment capacitor CR2 and an adjustment switch QCR. The adjustment capacitor CR2 has a first end and a second end. The first end of the adjustment capacitor CR2 is coupled to the resonant capacitor CR1. According to the connection relationship between the adjustment capacitor CR2 and the resonant capacitor CR1, the adjustment capacitor CR2 and the resonant capacitor CR1 can form an equivalent capacitor CR. Generally, the capacitance value of the adjustment capacitor CR2 is greater than or equal to the capacitance value of the resonant capacitor CR1. In one embodiment, the capacitance value of the adjustment capacitor CR2 is three times the capacitance value of the resonant capacitor CR1. Specifically, when the adjustment switch QCR is off, the adjustment capacitor CR2 is not coupled to the resonant capacitor CR1, so the capacitance value of the equivalent capacitor CR is the capacitance value of the resonant capacitor CR1. When the adjustment switch QCR is on, the adjustment capacitor CR2 is coupled to the resonant capacitor CR1, so the capacitance value of the equivalent capacitor CR is the equivalent capacitance value after the resonant capacitor CR1 and the adjustment capacitor CR2 are connected in parallel. Therefore, the capacitance value of the equivalent capacitor CR can be determined by designing the capacitance value of the resonant capacitor CR1 and / or the capacitance value of the adjustment capacitor CR2, and by controlling the on and off of the adjustment switch QCR.

[0064] The adjustment switch QCR has a first power terminal, a second power terminal, and a control terminal. The first power terminal of the adjustment switch QCR is coupled to the second end of the adjustment capacitor CR2, and the second power terminal of the adjustment switch QCR is coupled to the second switch Q2.

[0065] The controller 30 is used to control the energization time of the resonant regulation circuit 20, so as to maintain the transmission efficiency of the energy transmitted from the primary side winding W1 to the secondary side winding W2 within the full output voltage range, enabling the power converter 100 to operate with high efficiency. For example, without limiting the present invention, if the output voltage range of the output voltage Vo of the power converter 100 is from 5 volts to 48 volts, the controller 30 can control the energization time of the resonant regulation circuit 20, so that the magnitude of the output voltage Vo of the power converter 100 can be adjusted efficiently at the output voltage Vo between 5 volts and 48 volts.

[0066] As Figure 4 shown, the power converter 100 further includes a current detection unit 41 and a voltage detection unit 42. The current detection unit 41 is coupled to the resonant capacitor CR1 and the regulation capacitor CR2, and is used to detect the magnitude of the current flowing through the equivalent capacitor CR formed by the regulation capacitor CR2 and the resonant capacitor CR1, so as to generate a current signal Si. The current signal Si is in a proportional relationship with the magnitude of the current flowing through the equivalent capacitor CR, that is, when the current flowing through the equivalent capacitor CR is larger, the value of the current signal Si is larger, and vice versa, when the current flowing through the equivalent capacitor CR is smaller, the value of the current signal Si is smaller. Therefore, the magnitude of the current flowing through the equivalent capacitor CR can be determined according to the value of the current signal Si.

[0067] The voltage detection unit 42 is coupled to the first power supply terminal of the regulation switch QCR, and is used to detect the switching voltage VQCR on the regulation switch QCR. Taking the regulation switch QCR as an n-type metal oxide semiconductor field effect transistor as an example, the first power supply terminal is the drain, the second power supply terminal is the source, and the control terminal is the gate. Therefore, the switching voltage VQCR detected by the voltage detection unit 42 is the drain voltage.

[0068] Specifically, the first switch Q1 can be controlled to be turned on and off via the first control signal SQ1, and the second switch Q2 can be controlled to be turned on and off via the second control signal SQ2. The first control signal SQ1 and the second control signal SQ2 can be provided by a control unit or a control circuit not shown in Figure 4 shown. The controller 30 receives the first control signal SQ1 and the second control signal SQ2, as well as the current signal Si provided by the current detection unit 41 and the switching voltage VQCR provided by the voltage detection unit 42. Therefore, the controller 30 controls the turning on and off of the regulation switch QCR according to the first control signal SQ1 for controlling the first switch Q1, the second control signal SQ2 for controlling the second switch Q2, the current signal Si corresponding to the current flowing through the equivalent capacitor CR, and the switching voltage VQCR on the regulation switch QCR, and further controls the energization time of the resonant regulation circuit 20, so that the magnitude of the output voltage Vo of the power converter 100 can be adjusted efficiently within the full output voltage range.

[0069] Please refer to Figure 5 as shown, which is the circuit block diagram of the controller of the power converter of the present invention, and also refer to Figure 4 . Figure 4 The design of the controller 30 shown can be seen in Figure 5 . As Figure 5 shown, the controller 30 includes a calculation unit 31, a compensation unit 32, a first AND operation unit 33, a comparison unit 34, a second AND operation unit 35, and an OR operation unit 36.

[0070] The controller 30 obtains a charging control signal Schg according to the current signal Si and the first control signal SQ1, obtains a discharging control signal Sdischg according to the switching voltage VQCR and the second control signal SQ2, and generates a switching control signal Scr according to the charging control signal Schg and the discharging control signal Sdischg to control the conduction and cutoff of the regulating switch QCR.

[0071] Specifically, the charging control signal Schg is obtained by taking the intersection (AND) of the voltage compensation signal Scmps generated after compensating the current error signal Serr between the current signal Si and the current reference value Iref and the first control signal SQ1. The discharging control signal Sdischg is obtained by taking the intersection (AND) of the voltage comparison signal Scmpr generated after comparing the switching voltage VQCR and the voltage reference value Vref and the second control signal SQ2.

[0072] More specifically, the calculation unit 31 receives the current signal Si and the current reference value Iref, and calculates the current error signal Serr according to the current signal Si and the current reference value Iref. In this embodiment, the current reference value Iref can be set to 0 amperes. The compensation unit 32 receives the current error signal Serr and compensates the current error signal Serr to generate a voltage compensation signal Scmps. The first AND operation unit 33 receives the voltage compensation signal Scmps and the first control signal SQ1, and performs a logical AND operation on the voltage compensation signal Scmps and the first control signal SQ1 to generate a charging control signal Schg. Therefore, the operations of the calculation unit 31, the compensation unit 32, and the first AND operation unit 33 are to determine the time length of the resonant operation so as to match the time of the leakage magnetic flux of the main inductor to maintain the power converter 100 in high-efficiency operation.

[0073] The comparison unit 34 receives the switch voltage VQCR and the voltage reference value Vref, and compares the switch voltage VQCR with the voltage reference value Vref to generate a voltage comparison signal Scmpr. The second AND operation unit 35 receives the voltage comparison signal Scmpr and the second control signal SQ2, and performs a logical AND operation on the voltage comparison signal Scmpr and the second control signal SQ2 to generate a discharge control signal Sdischg. Therefore, the operations of the comparison unit 34 and the second AND operation unit 35 are to determine the starting timing of the resonance compensation. In this embodiment, the resonance compensation is started when the first switch Q1 is turned on, which means that the resonance compensation is started when charging the equivalent capacitor CR.

[0074] Finally, the OR operation unit 36 receives the charge control signal Schg and the discharge control signal Sdischg, and performs an OR operation on the charge control signal Schg and the discharge control signal Sdischg to generate a switch control signal Scr to control the conduction and turn-off of the regulating switch QCR.

[0075] Please refer to Figure 6 as shown, which are the relevant voltage waveforms, current waveforms, and control signal waveforms during the operation of the power converter of the present invention. Please refer to Figure 4 、 Figure 5 . From the time t0 to before the time t4, the first switch Q1 and the second switch Q2 are complementary controlled to conduct and turn off. Therefore, after the time t0, when the first switch Q1 is turned on, the main inductor (i.e., the exciting inductor) of the transformer TR and the resonance capacitor CR1 are charged and energy is stored. At the time t2, the second switch Q2 is turned on, and the resonance circuit 10 starts to perform resonance operation. As Figure 6 shown, the output voltage Vo during the operation from the time t0 to the time t4 can enable the power converter 100 to operate at high efficiency.

[0076] From the time t4 to before the time t9, since the output voltage Vo decreases (at the time t4). However, during this period, assuming that the resonance compensation of the regulating capacitor CR2 is not started, therefore, it can be clearly seen between the time t7 and the time t8 of Figure 6 that since the resonance capacitor CR1 discharges prematurely and the leakage magnetic time of the main inductor still continues, the energy transfer efficiency will be greatly reduced, thereby resulting in a decrease in efficiency.

[0077] From the time t9 to before the time t17, although the output voltage Vo decreases (at the time t9). However, different from the period from the time t4 to before the time t9 when the resonance compensation of the regulating capacitor CR2 is not started, the resonance compensation of the regulating capacitor CR2 is introduced during the period from the time t9 to before the time t17. Therefore, as Figure 4 、Figure 5 The disclosed circuit operates and is controlled such that when the output voltage Vo decreases, since the regulating capacitor CR2 is incorporated into the resonant capacitor CR1, the equivalent capacitor CR increases. Therefore, the discharge time of the equivalent capacitor CR can be extended, enabling it to match the time of the leakage magnetic flux of the main inductor, so as to maintain the power converter 100 in high-efficiency operation.

[0078] Specifically, as Figure 6 shown, at time t10, the first control signal SQ1 turns on the first switch Q1. At this time, the switching control signal Scr generated by the controller 30 also turns on the regulating switch QCR of the resonant regulating circuit 20. Therefore, the voltage across the regulating capacitor CR2, VCR2, continuously increases as the regulating capacitor CR2 is charged. Until time t14, since the resonant capacitor CR1 releases energy, the voltage across the resonant capacitor CR1, VCR1, becomes less than the voltage across the regulating capacitor CR2, VCR2. At this time, the switching voltage VQCR across the regulating switch QCR becomes negative. Therefore, the body diode DQCR of the regulating switch QCR conducts forward. Corresponding Figure 5 to the comparison of the switching voltage VQCR and the voltage reference value Vref as described, assuming the voltage reference value Vref is 0V (considering the body diode DQCR as ideal) or -0.7V (considering the voltage difference across the body diode DQCR when it conducts), the voltage comparison signal Scmpr generated after comparison is at a high level. And since the second control signal SQ2 is at a high level to turn on the second switch Q2, therefore, the discharge control signal Sdischg after the logical AND operation by the second AND operation unit 35 is at a high level. Thus, after the OR operation unit 36 performs a logical OR operation on the charge control signal Schg and the discharge control signal Sdischg, a high-level switching control signal Scr is generated to turn on the regulating switch QCR, controlling the incorporation of the regulating capacitor CR2 into the resonant capacitor CR1 to increase the equivalent capacitor CR. Therefore, the discharge time of the equivalent capacitor CR can be extended. Incidentally, turning on the regulating switch QCR at this time can ensure zero-voltage switching (ZVS) when turning on the regulating switch QCR. Until time t16, it enables matching with the time of the leakage magnetic flux of the main inductor to maintain the power converter 100 in high-efficiency operation. Incidentally, between time t16 and time t17, it can be used as the timing for zero-voltage switching control of the first switch Q1 and the second switch Q2.

[0079] In summary, by controlling and adjusting the incorporation of capacitor CR2 into the resonant capacitor CR1, the discharge time of the equivalent capacitor CR can be extended at a lower peak current of the resonant current Icr. Therefore, not only can the component losses on the secondary side (such as secondary side coil losses, secondary side rectification losses, and secondary side circuit board losses, as expressed by the following formula (1)) be reduced to improve efficiency, but also smaller current-carrying components can be selected to reduce the circuit cost. The selected component specifications can be improved as expressed by the following formula (2).

[0080]

[0081]

[0082] Please refer to Figure 7 as shown, which is a flowchart of the operation method of the power converter of the present invention. For the circuit architecture of the power converter, please refer to the foregoing Figures 4 to 6 , as well as the corresponding description in the specification, which will not be elaborated here. The control method includes: First, the current detection unit 41 can detect the magnitude of the current flowing through the equivalent capacitor CR formed by the resonant capacitor CR1 and the adjustment capacitor CR2 to generate a current signal Si (step S10). When the adjustment switch QCR is turned off, the capacitance value of the equivalent capacitor CR is the capacitance value of the resonant capacitor CR1. When the adjustment switch QCR is turned on, the capacitance value of the equivalent capacitor CR is the equivalent capacitance value after the resonant capacitor CR1 and the adjustment capacitor CR2 are connected in parallel.

[0083] Then, the voltage detection unit 42 can detect the switching voltage VQCR on the adjustment switch QCR (step S20). Then, the first control signal SQ1 for controlling the first switch Q1 and the second control signal SQ2 for controlling the second switch Q2 are obtained (step S30).

[0084] Finally, when the magnitude of the output voltage Vo of the power converter 100 changes, according to the current signal Si, the switching voltage VQCR, and the first control signal SQ1 and the second control signal SQ2, the energization time of the resonant adjustment circuit 20 is controlled (that is, the conduction and turn-off of the adjustment switch QCR are controlled to control the energization time of the resonant adjustment circuit 20), so that the energy transfer efficiency from the primary side winding W1 to the secondary side winding W2 is maintained within the full output voltage range (step S40). Since the operation method of the power converter corresponds to the circuit control operation of the power converter, please refer to the foregoing detailed description, so it will not be elaborated here.

[0085] In summary, the present invention has the following features and advantages:

[0086] 1. The present invention can dynamically adjust the time length of the resonant operation and the starting timing of the resonant compensation at any voltage within the full output voltage range, which can not only achieve the immediacy of on-line resonant compensation, but also accurately achieve the integrity of the resonant compensation.

[0087] 2. By controlling and adjusting the capacitor to be incorporated into the resonant capacitor, the discharge time of the equivalent capacitor can be extended at a resonant current with a lower current peak. This can not only reduce the component losses on the secondary side to improve the efficiency, but also select components with a smaller current withstand capacity to reduce the circuit cost.

[0088] 3. It can ensure zero-voltage switching (ZVS) for turning on the regulating switch in the zero-voltage state to reduce the switching losses.

[0089] 4. After the capacitor compensation action is completed, the timing for providing zero-voltage switching control to the high-side switch (i.e., the first switch) and the low-side switch (i.e., the second switch) can be provided.

[0090] As described above, it is only a detailed description and drawings of the preferred specific embodiments of the present invention. However, the features of the present invention are not limited thereto and are not used to limit the present invention. The entire scope of the present invention shall be subject to the scope of the patent application. All embodiments that conform to the spirit of the scope of the patent application of the present invention and its similar variations shall be included in the scope of the present invention. Any changes or modifications that can be easily conceived by any person skilled in the art within the field of the present invention can be covered by the patent scope of the present invention.

Claims

1. A power converter, characterized in that: include: A transformer comprising 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 provided by at least the primary winding; A first switch and a second switch, the first switch and the second switch are connected to a node, and the node is coupled to the resonant circuit; a resonance adjustment circuit coupled to the resonance circuit; as well as A controller controls the enabling time of the resonant regulating circuit according to the magnitude of an output voltage of the power converter, so as to maintain the transmission efficiency of the energy transmitted from the primary winding to the secondary winding under the full output voltage range.

2. The power converter according to claim 1, characterized in that: The resonant regulation circuit comprises: an adjusting capacitor having a first end and a second end, wherein the first end of the adjusting capacitor is coupled to the resonant capacitor; wherein the adjusting capacitor and the resonant capacitor form an equivalent capacitor; and A regulating switch has a first power supply end, a second power supply end and a control end; wherein the first power supply end is coupled to the second end of the regulating capacitor, and the second power supply end is coupled to the second switch.

3. The power converter according to claim 2, characterized in that: Also includes: A current detection unit is coupled to the resonant capacitor and the adjustment capacitor to detect the magnitude of the current flowing through the equivalent capacitor to generate a current signal; as well as A voltage detection unit is coupled to the first power terminal of the regulating switch and is used for detecting a switch voltage on the regulating switch.

4. The power converter according to claim 3, characterized in that: The controller controls the on and off of the regulating switch according to a first control signal for controlling the first switch, a second control signal for controlling the second switch, a current signal corresponding to the current flowing through the equivalent capacitor, and the switch voltage on the regulating switch.

5. The power converter according to claim 4, characterized in that: When the regulating switch is turned off, the capacitance value of the equivalent capacitor is the capacitance value of the resonant capacitor; when the regulating switch is turned on, the capacitance value of the equivalent capacitor is the equivalent capacitance value of the resonant capacitor and the regulating capacitor in parallel.

6. The power converter according to claim 4, characterized in that: The controller obtains a charging control signal according to the current signal and the first control signal, obtains a discharging control signal according to the switch voltage and the second control signal, and generates a switch control signal according to the charging control signal and the discharging control signal to control the on and off of the regulating switch.

7. The power converter according to claim 6, characterized in that: The charge control signal is obtained by the intersection of a voltage compensation signal generated by compensating a current error signal between the current signal and a current reference value and the first control signal; the discharge control signal is obtained by the intersection of a voltage comparison signal generated by comparing the switch voltage with a voltage reference value and the second control signal.

8. The power converter according to claim 7, characterized in that: The controller includes: a calculation unit, receiving the current signal and the current reference value, and calculating the current error signal according to the current signal and the current reference value; a compensation unit, receiving the current error signal and compensating the current error signal to generate the voltage compensation signal; a first AND operation unit, receiving the voltage compensation signal and the first control signal, and performing a logic AND operation on the voltage compensation signal and the first control signal to generate the charging control signal; a comparison unit, receiving the switch voltage and the voltage reference value, and comparing the switch voltage with the voltage reference value to generate the voltage comparison signal; a second AND operation unit, receiving the voltage comparison signal and the second control signal, and performing a logic AND operation on the voltage comparison signal and the second control signal to generate the discharge control signal; and An OR operation unit receives the charge control signal and the discharge control signal, and performs a logic OR operation on the charge control signal and the discharge control signal to generate the switch control signal.

9. A control method for a power converter, characterized in that: The power converter includes a first switch and a second switch, a resonant capacitor and a resonant adjustment circuit, wherein the resonant adjustment circuit includes an adjustment capacitor and an adjustment switch, and the control method includes: Detecting the magnitude of a current flowing through an equivalent capacitor formed by the resonant capacitor and the adjusting capacitor to generate a current signal; detecting a switch voltage on the regulating switch; Obtaining a first control signal for controlling the first switch and a second control signal for controlling the second switch; and When the magnitude of an output voltage of the power converter changes, the enabling time of the resonant adjustment circuit is controlled according to the current signal, the switch voltage, the first control signal and the second control signal, so that the energy transmission efficiency of a primary side winding to a secondary side winding is maintained within the full output voltage range.

10. The control method of the power converter according to claim 9, characterized in that: In the step of controlling the enabling time of the resonance regulating circuit, the on and off of the regulating switch is controlled according to the current signal, the switch voltage, the first control signal and the second control signal to control the enabling time of the resonance regulating circuit.

11. The control method of the power converter according to claim 10, characterized in that: When the regulating switch is turned off, the capacitance value of the equivalent capacitor is the capacitance value of the resonant capacitor; when the regulating switch is turned on, the capacitance value of the equivalent capacitor is the equivalent capacitance value of the resonant capacitor and the regulating capacitor in parallel.

12. The control method of the power converter according to claim 10, characterized in that: A charging control signal is obtained according to the current signal and the first control signal, a discharging control signal is obtained according to the switch voltage and the second control signal, and a switch control signal is generated according to the charging control signal and the discharging control signal to control the on and off of the regulating switch.

13. The control method of the power converter according to claim 12, characterized in that: The charge control signal is obtained by the intersection of a voltage compensation signal generated by compensating a current error signal between the current signal and a current reference value and the first control signal; the discharge control signal is obtained by the intersection of a voltage comparison signal generated by comparing the switch voltage with a voltage reference value and the second control signal.

14. The control method of the power converter according to claim 13, characterized in that: Also includes: Providing a calculation unit, receiving the current signal and the current reference value, and calculating the current error signal according to the current signal and the current reference value; Providing a compensation unit, receiving the current error signal, and compensating the current error signal to generate the voltage compensation signal; A first AND operation unit is provided to receive the voltage compensation signal and the first control signal, and perform a logic AND operation on the voltage compensation signal and the first control signal to generate the charging control signal; A comparison unit is provided to receive the switch voltage and the voltage reference value, and compare the switch voltage with the voltage reference value to generate the voltage comparison signal; Providing a second AND operation unit, receiving the voltage comparison signal and the second control signal, and performing a logic AND operation on the voltage comparison signal and the second control signal to generate the discharge control signal; and An OR operation unit is provided to receive the charging control signal and the discharging control signal, and perform a logic OR operation on the charging control signal and the discharging control signal to generate the switch control signal.

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