A direct current converter
By introducing a resonant network into the Buck circuit, zero-voltage conduction of the switching transistor is achieved, solving the problem of high switching losses in traditional Buck circuits, improving energy conversion efficiency and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-15
- Publication Date
- 2026-03-17
AI Technical Summary
In traditional Buck circuits, the switching transistors operate with hard switching, resulting in significant switching losses and low energy conversion efficiency, which is especially pronounced at high frequencies.
A resonant network is introduced into the Buck circuit so that the absolute value of the total resonant current is greater than the absolute value of the critical current before the switch is turned on, thus achieving zero-voltage turn-on of the switch. By combining the resonant circuit and the rectifier circuit, switching losses are reduced.
Soft switching of the switching transistors in the Buck circuit was achieved, reducing switching losses and improving energy conversion efficiency. Furthermore, the number of components used was reduced by reusing the switching devices, thus saving costs.
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Figure CN115224933B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronics technology, and in particular to a DC-DC converter. Background Technology
[0002] Currently, the Buck circuit is one of the most widely used basic circuits in the field of switching power supplies.
[0003] However, in traditional Buck circuits, since each switch operates as a hard switch, meaning that the voltage and current are not zero during the switching process, significant switching losses are generated during energy conversion. This is especially true at higher frequencies, where the switching losses increase significantly, leading to a reduction in the Buck's energy conversion efficiency.
[0004] Therefore, improving the energy conversion efficiency of Buck circuits is a technical problem that urgently needs to be solved. Summary of the Invention
[0005] In view of this, the present invention provides a DC-DC converter to improve the energy conversion efficiency of Buck circuits.
[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:
[0007] This application provides a DC-DC converter, characterized in that it includes: a Buck circuit and at least one resonant network; wherein:
[0008] The input terminal of the Buck circuit serves as the input terminal of the DC-DC converter, and the output terminal of the Buck circuit serves as one output terminal of the DC-DC converter.
[0009] In the Buck circuit, the input and output terminals of at least one switching transistor are connected in parallel with the input terminal of the resonant network; the output terminal of the resonant network serves as the other output terminal of the DC-DC converter.
[0010] The sum of the resonant currents of all the resonant networks is the total resonant current. The absolute value of the total resonant current is greater than or equal to the absolute value of the critical current before the upper switch is turned on. The upper switch is a switch connected to the positive terminal of the input of the Buck circuit.
[0011] The critical current is the resonant total current that minimizes the absolute value of the junction capacitance of the upper switch before it is turned on.
[0012] Optionally, the resonant network includes: a resonant circuit and a rectifier circuit; wherein:
[0013] The input terminal of the resonant circuit serves as the input terminal of the resonant network; the AC side of the rectifier circuit draws power from the output terminal of the resonant circuit; and the DC terminal of the rectifier circuit serves as the output terminal of the resonant network.
[0014] Optionally, the resonant circuit includes: a resonant capacitor, a resonant inductor, a magnetizing inductor, and a transformer; wherein:
[0015] The resonant capacitor, the resonant inductor, and the magnetizing inductor are connected in series, and the two ends of the series branch formed serve as the input terminals of the resonant circuit.
[0016] The primary winding of the transformer draws power from the magnetizing inductor, and the secondary winding of the transformer serves as the output terminal of the resonant circuit.
[0017] Optionally, in the resonant circuit, by setting the inductance value of each of the excitation inductors and / or the turns ratio of each of the transformers, the absolute value of the total resonant current is made greater than or equal to the absolute value of the critical current before the upper switch is turned on.
[0018] Optionally, the resonant circuit includes: a resonant capacitor, a resonant inductor, and a transformer; wherein:
[0019] The resonant capacitor, the resonant inductor, and the primary winding of the transformer are connected in series, and the two ends of the series branch formed serve as the input terminals of the resonant circuit.
[0020] The secondary winding of the transformer serves as the output terminal of the resonant circuit.
[0021] Optionally, in the resonant circuit, by setting the turns ratio of each transformer, the absolute value of the total resonant current is made greater than or equal to the absolute value of the critical current before the upper switch is turned on.
[0022] Optionally, the resonant circuit includes a transformer, and the secondary winding of the transformer includes a first secondary winding and a second secondary winding; the rectifier circuit includes a filter capacitor and two rectifier diodes; wherein:
[0023] The cathode of the first rectifier diode is connected to the same-name terminal of the first secondary winding, and the cathode of the second rectifier diode is connected to the opposite-name terminal of the second secondary winding.
[0024] The anodes of the first rectifier diode and the second rectifier diode are connected, and the connection point serves as the negative terminal of the DC side of the rectifier circuit.
[0025] The opposite-named end of the first secondary winding is connected to the same-named end of the second secondary winding, and the connection point serves as the positive DC side of the rectifier circuit.
[0026] The two ends of the filter capacitor are connected to the positive DC terminal and the negative DC terminal of the rectifier circuit, respectively.
[0027] Optionally, the output terminal of the resonant network can serve as another output terminal of the DC-DC converter.
[0028] Optionally, it may also include: a controller; wherein:
[0029] The control terminals of the upper and lower switches are both connected to the controller; the lower switch is a switch connected to the negative input terminal of the Buck circuit.
[0030] The controller is used to control the upper switch and the lower switch to conduct alternately.
[0031] Optionally, the controller employs a frequency modulation control strategy or a pulse width modulation strategy to regulate the output of the Buck circuit.
[0032] As can be seen from the above technical solution, this application provides a DC-DC converter. In this DC-DC converter, since the absolute value of the resonant total current is greater than or equal to the absolute value of the critical current before the upper switch is turned on, and the critical current is the resonant total current with the smallest absolute value that allows the junction capacitance to discharge before the upper switch is turned on, the junction capacitance of the upper switch is discharged before the upper switch is turned on. Therefore, when the upper switch is turned on, the voltage across the junction capacitance is zero, that is, the voltage between the input and output terminals of the upper switch is zero, thereby achieving zero-voltage turn-on of the upper switch. In addition, since the resonant total current is in the opposite direction to the inductor current in the Buck circuit before the upper switch is turned on, and in the same direction as the inductor current in the Buck circuit before the lower switch is turned on, the junction capacitance of the lower switch can also be discharged before the lower switch is turned on, that is, achieving zero-voltage turn-on of the lower switch. Therefore, the DC-DC converter provided by this application can realize soft switching of each switch in the Buck circuit, thereby reducing the switching losses of the Buck circuit and improving the energy conversion efficiency of the Buck circuit. Attached Figure Description
[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0034] Figures 1-6 These are schematic diagrams illustrating six implementations of the DC-DC converter provided in the embodiments of this application.
[0035] Figure 7a and Figure 7b These are schematic diagrams showing the state of current IAB at different dead time intervals;
[0036] Figure 8 for Figure 5 The circuit shown is ideally configured with only the Buck circuit outputting externally and the duty cycle of the control signal for the upper switch Q1 being equal to 0.5. The diagram illustrates the changes in resonant inductor current iLr, inductor current iLb, current iab, and voltage vab at different stages.
[0037] Figure 9 for Figure 5 The circuit shown is illustrated in the simulation test when only the Buck circuit outputs externally and the duty cycle of the control signal of the upper switch Q1 is greater than 0.5. The simulation results show the changes of the excitation inductor current iLm, resonant inductor current iLr, inductor current iLb, current iab, and voltage vab at different stages.
[0038] Figure 10 for Figure 5 The circuit shown is illustrated in the simulation test when only the Buck circuit outputs externally and the duty cycle of the control signal of the upper switch Q1 is equal to 0.5. The simulation results show the changes of the excitation inductor current iLm, resonant inductor current iLr, inductor current iLb, current iab, and voltage vab at different stages.
[0039] Figure 11 for Figure 5 The circuit shown is illustrated in the simulation test when only the Buck circuit outputs externally and the duty cycle of the control signal of the upper switch Q1 is less than 0.5. The simulation results show the changes of the excitation inductor current iLm, resonant inductor current iLr, inductor current iLb, current iab, and voltage vab at different stages. Detailed Implementation
[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0041] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0042] To improve the energy conversion efficiency of Buck circuits, this application provides a DC-DC converter, the specific structure of which can be found in [reference needed]. Figures 1 to 3 Specifically, it includes a Buck circuit and at least one resonant network 20; the number of resonant networks 20 can be determined depending on the specific situation, and is not specifically limited here.
[0043] The connection relationships between the various components are as follows:
[0044] The input terminal of the Buck circuit serves as the input terminal of the DC-DC converter, and the output terminal of the Buck circuit serves as one output terminal of the DC-DC converter.
[0045] In practical applications, the specific structure of a Buck circuit is as follows: Figures 1 to 3 As shown, the half-bridge structure 10 includes an upper switch Q1, a lower switch Q2, a first diode D1, and a second diode D2.
[0046] The input terminal of the upper switch Q1 is connected to the positive input terminal of the Buck circuit, the output terminal of the upper switch Q1 is connected to the input terminal of the lower switch Q2, the anode of the first diode D1 is connected to the output terminal of the upper switch Q1, and the cathode of the first diode D1 is connected to the input terminal of the upper switch Q1.
[0047] The input terminal of the lower switch Q2 is connected to the output terminal of the upper switch Q1. The output terminal of the lower switch Q2 is connected to the negative input terminal of the Buck circuit. The anode of the second diode D2 is connected to the output terminal of the lower switch Q2, and the cathode of the second diode D2 is connected to the input terminal of the lower switch Q2.
[0048] It should be noted that, Figures 1 to 3 Cj1 in the figure is the junction capacitance of the upper switching transistor Q1. Figures 1 to 3 Cj2 in the figure represents the junction capacitance of the lower switching transistor Q2.
[0049] In this DC-DC converter, the input terminal of each resonant network 20 can be connected in parallel between the input and output terminals of any switch in the Buck circuit.
[0050] For example, such as Figure 1 As shown, a resonant network 20 is connected in parallel between the input and output terminals of the lower-side switch Q2; or, as... Figure 2 As shown, a resonant network 20 is connected in parallel only between the input and output terminals of the upper switch Q1; or, as... Figure 3 As shown, a resonant network 20 is connected in parallel between the input and output terminals of the upper switch Q1 and the lower switch Q2. In addition, there may be one or more resonant networks 20 connected in parallel between the input and output terminals of the upper switch Q1 or the lower switch Q2.
[0051] In this DC-DC converter, the sum of the resonant currents of all resonant networks 20 is the total resonant current. When the DC-DC converter is running, the absolute value of the total resonant current is greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on.
[0052] The critical current is the minimum total resonant current required to discharge the junction capacitance of the upper switch Q1 before it is turned on.
[0053] Since the absolute value of the resonant total current is greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on, and the critical current is the minimum resonant total current required to discharge the junction capacitance Cj1 before the upper switch Q1 is turned on, the junction capacitance Cj1 discharges before the upper switch Q1 is turned on. Therefore, when the upper switch Q1 is turned on, the voltage across the junction capacitance Cj1 is zero, that is, the voltage between the input and output terminals of the upper switch Q1 is zero, thus achieving zero-voltage turn-on of the upper switch Q1. In addition, since the resonant total current is in the opposite direction to the inductor current in the Buck circuit before the upper switch Q1 is turned on, and in the same direction as the inductor current in the Buck circuit before the lower switch Q2 is turned on, the junction capacitance Cj2 can also discharge before the lower switch Q2 is turned on, thus achieving zero-voltage turn-on of the lower switch Q2. Therefore, the DC-DC converter provided in this application can achieve soft switching of each switch in the Buck circuit, thereby reducing the switching losses of the Buck circuit and improving the energy conversion efficiency of the Buck circuit. In addition, this DC-DC converter reduces the number of components used by multiplexing switching devices, thereby saving costs.
[0054] Optionally, the output terminal of each resonant network 20 can be used as another output terminal of the DC-DC converter, i.e., connected to the load; or it can not be used as an output terminal of the DC-DC converter, i.e., not connected to the load; no specific limitation is made here, and it can be determined according to the specific situation, all of which are within the protection scope of this application.
[0055] It should be noted that when the output terminal of the resonant network 20 is not used as the output terminal of the DC-DC converter, the output voltage of the resonant network 20 can be increased and / or a resistor with a larger resistance value can be connected in parallel between the two ends of the output terminal of the resonant network 20 as a dummy load, so that the resonant network 20 can work under a light load environment. As a result, the output power of the resonant network 20 is reduced, and the current stress required to withstand by the corresponding devices of the resonant network 20 is reduced. Therefore, the overall cost and size of the resonant network 20 are also reduced.
[0056] Another embodiment of this application provides one implementation of the resonant network 20, the specific structure of which can be found in [reference needed]. Figure 4 ( Figure 4 Only Figure 1 Based on the above, it is shown that it specifically includes: resonant circuit 21 and rectifier circuit 22.
[0057] The input terminal of the resonant circuit 21 serves as the input terminal of the resonant network 20; the AC side of the rectifier circuit draws power from the output terminal of the resonant circuit 21; the DC side of the rectifier circuit 22 serves as the output terminal of the resonant rectifier circuit 22.
[0058] This embodiment provides one implementation of the resonant circuit 21, the specific structure of which is as follows: Figure 5 ( Figure 5 Only Figure 1 As shown in the diagram, the components include: resonant capacitor Cr, resonant inductor Lr, magnetizing inductor Lm, and transformer 211. The connections between these components are as follows:
[0059] The resonant capacitor Cr, the resonant inductor Lr, and the magnetizing inductor Lm are connected in series, and the two ends of the series branch formed serve as the input terminals of the resonant circuit 21. The primary winding of the transformer 211 draws power from the magnetizing inductor Lm, and the secondary winding of the transformer 211 serves as the output terminal of the resonant circuit 21.
[0060] In this embodiment of the resonant circuit 21, by setting the inductance value of each magnetizing inductor Lm and / or the turns ratio of each transformer 211, the absolute value of the total resonant current is made greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on.
[0061] It should be noted that this embodiment of the resonant circuit 21, combined with the rectifier circuit and the half-bridge structure 10 in the Buck circuit, constitutes an LLC resonant converter circuit; however, it should be noted that, in general, the half-bridge structure 10 of the LLC resonant converter circuit includes two switching transistors. Therefore, in this DC-DC converter, it is preferable that the half-bridge structure 10 includes a Buck circuit with two switching transistors.
[0062] This embodiment provides another implementation of the resonant circuit 21, the specific structure of which is as follows: Figure 6 ( Figure 6 Only Figure 1 As shown in the diagram, the components include: resonant capacitor Cr, resonant inductor Lr, and transformer 211; the connections between these components are as follows:
[0063] The resonant capacitor Cr, the resonant inductor Lr, and the primary winding of transformer 211 are connected in series, and the two ends of the series branch formed serve as the input terminals of the resonant circuit 21; the secondary winding of transformer 211 serves as the output terminal of the resonant circuit 21.
[0064] In this embodiment of the resonant circuit 21, by setting the turns ratio of each transformer 211, the absolute value of the total resonant current is greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on.
[0065] It should be noted that this embodiment of the resonant circuit 21, combined with the rectifier circuit and the half-bridge structure 10 in the Buck circuit, constitutes a series resonant converter circuit; however, it should be noted that, in general, the half-bridge structure 10 of the LLC resonant converter circuit includes two switching transistors. Therefore, in this DC-DC converter, it is preferable that the half-bridge structure 10 includes a Buck circuit with two switching transistors.
[0066] The above are only two implementation methods of the resonant circuit. In practical applications, there are other methods, including but not limited to these. No specific implementation is specified here. The specific implementation method can be determined according to the specific circumstances, and all are within the protection scope of this application.
[0067] The following is based on Figure 5 Taking the circuit shown as an example, this application explains in detail how the DC-DC converter provides implements soft switching of each switching transistor in Buck; the details are as follows:
[0068] 1) When only the output terminal of the resonant network 20 outputs externally, as can be seen from the above, Figure 5 The resonant network 20 shown and the half-bridge structure 10 in the Buck circuit constitute an LLC resonant converter circuit, which is the same as the traditional LLC resonant converter circuit, with the same output characteristics and a common control strategy. Therefore, the switching transistors in the half-bridge structure 10 can achieve soft switching.
[0069] 2) When the output of the Buck circuit is outputting externally while the output of the resonant network 20 is not outputting externally, how to achieve soft switching of each switching transistor in the Buck circuit? The details are as follows:
[0070] The following section will introduce the soft-switching process of the upper switching transistor Q1 and the lower switching transistor Q2:
[0071] Figure 7a The diagram shows the stage when the lower switch Q2 is turned off and the upper switch Q1 is not turned on, which is the first dead time. At this time, the current iab is negative, that is, in the negative direction. Figure 7b The diagram shows the stage where the upper switch Q1 is turned off and the lower switch Q2 is not turned on, which is the second dead time. At this time, the current iab is positive, that is, in the positive direction.
[0072] Since the voltage across the first junction capacitor Cj1 is Vin and the voltage across the second junction capacitor Cj2 is zero when the lower switch Q2 is on and the upper switch Q1 is off, when entering... Figure 7a During the stage shown, the current iab discharges the first junction capacitor Cj1 and charges the second junction capacitor Cj2. Before the upper switch Q1 is turned on, the voltage of the first junction capacitor Cj1 is reduced to zero and the voltage of the second junction capacitor Cj2 is charged to Vin.
[0073] Since the capacitance of the first junction capacitor Cj1 drops to zero, the first diode D1 conducts, and current flows through the first diode D1. As a result, the voltage between the input and output terminals of the upper switch Q1 is zero. Therefore, when the upper switch Q1 receives the conduction signal, the upper switch Q1 can conduct with zero voltage, that is, realize soft switching.
[0074] Similarly, as in the process described above, when entering Figure 7b During the stage shown, the current iab charges the first junction capacitor Cj1 and discharges the second junction capacitor Cj2. Before the lower switch Q2 is turned on, the voltage of the first junction capacitor Cj1 is charged to Vin and the voltage of the second junction capacitor Cj2 is reduced to zero.
[0075] Since the capacitance of the second junction capacitor Cj2 drops to zero, the second diode D2 conducts, and current flows through the second diode D2. As a result, the voltage between the input and output terminals of the lower switch Q2 is zero. Therefore, when the lower switch Q2 receives the conduction signal, the lower switch Q2 can conduct with zero voltage, that is, soft switching is achieved.
[0076] From the above soft-switching implementation process, it can be seen that the conditions for soft-switching are: 1) the current iab is in Figure 7a The stage shown is in the negative direction. Figure 7b The stage shown is in the positive direction; 2) The current iab can enable the junction capacitance of the corresponding switching transistor to complete charging and discharging, that is, there exists a current threshold I that guarantees the realization of soft switching. zvs I zvs The expression for the current threshold is as follows:
[0077]
[0078] Among them, I zvs is the current threshold, Coss is the junction capacitance of the corresponding switch, and Td is the corresponding dead time.
[0079] Parasitic capacitance was not considered in the threshold calculation process; therefore, to ensure the implementation of soft switching, it is necessary to... Figure 7a and Figure 7b During the phase shown, the absolute value of the current iab must be greater than or equal to the current threshold I. zvs .
[0080] In the DC-DC converter provided in this application, such as Figure 5 As shown, the current iab is equal to the sum of the inductor current iLb and the resonant inductor current iLr, i.e., iab = iLb + iLr; when in Figure 7b During the stage shown, both the resonant inductor current iLr and the inductor current iLb are positive. Figure 7a During the stage shown, the resonant inductor current iLr is negative and the inductor current iLb is positive. Therefore, to achieve soft switching of Q1, i.e., in the following stage... Figure 7a During this stage, the current iab is in the negative direction, and its absolute value is greater than or equal to the threshold current I. zvs .
[0081] When the duty cycle of the control signal for the switching transistor Q1 is 0.5, ideally, the changes in the magnetizing inductor current iLm, resonant inductor current iLr, inductor current iLb, current iab, and voltage vab at different stages are as follows: Figure 8 As shown; in Figure 7a During the stage shown, the resonant inductor current iLr is equal to the magnetizing inductor current iLm, i.e., iab = iLb + iLr = iLb + iLm. Therefore, by adjusting the amplitude of the magnetizing inductor current iLm, the absolute value of the current iab can be guaranteed to be greater than or equal to the threshold current I. zvs .
[0082] When the duty cycle of the control signal for the upper switching transistor Q1 is greater than 0.5, or when the duty cycle of the control signal for the upper switching transistor Q1 is less than 0.5, in Figure 7a During the stage shown, the resonant inductor current iLr is greater than or equal to the magnetizing inductor current iLm. Therefore, by adjusting the amplitude of the magnetizing inductor current iLm, the absolute value of the current iab can be guaranteed to be greater than or equal to the threshold current I. zvs .
[0083] Therefore, regardless of the duty cycle of the control signal for the upper switching transistor Q1, the amplitude of the magnetizing inductor current iLm can be adjusted to achieve the desired result. Figure 7a During the phase, the absolute value of the current iab is guaranteed to be greater than or equal to the threshold current I. zvs .
[0084] When the duty cycle of the control signal for the upper switching transistor Q1 is greater than 0.5, equal to 0.5, and less than 0.5, respectively, the following applies: Figure 5The resonant network 20 shown was used for simulation experiments, and the obtained excitation inductor current iLm, resonant inductor current iLr, inductor current iLb, and current iab are as follows: Figure 9 , Figure 10 , Figure 11 As shown.
[0085] The expression for the magnetizing inductor current iLm is as follows:
[0086]
[0087] Therefore, by setting the inductance value of the magnetizing inductor Lm in the resonant network 20 and the turns ratio of the transformer, the absolute value of iab can be made greater than or equal to the current threshold I. zvs .
[0088] 3) When the output of the Buck circuit is output to the outside and the output of the resonant network 20 is also output to the outside, how to achieve soft switching of each switching transistor in the Buck is the same as in point 2, and will not be repeated here.
[0089] In this case, not only is soft switching of each switching transistor achieved, reducing switching losses, but the DC-DC converter can also output from two ports or even multiple ports.
[0090] It should be noted that when multiple resonant networks 20 are connected in parallel between the input and output terminals of the corresponding switching transistor, or when resonant networks 20 are connected in parallel between the input and output terminals of both switching transistors, the current iab is equal to the sum of the currents of multiple resonant inductors and the inductor current iLb. Therefore, it can be deduced from the above that by setting the inductance value of each magnetizing inductor and / or the turns ratio of each transformer, the absolute value of the total resonant current can be made greater than or equal to the absolute value of the critical current before the upper switching transistor Q1 is turned on.
[0091] When the structure of the DC converter is Figure 6 The structure shown follows a similar principle to the one described above, except that... Figure 6 In the structure shown, since there is no magnetizing inductor, it is not possible to make the absolute value of the total resonant current greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on by setting each magnetizing inductor. Instead, the absolute value of the total resonant current can be made greater than or equal to the absolute value of the critical current before the upper switch Q1 is turned on by setting the turns ratio of the transformer.
[0092] Another embodiment of this application provides an implementation of the rectifier circuit 22, applicable to cases where the resonant circuit 21 includes a transformer 211, and the secondary winding of the transformer 211 includes a first secondary winding and a second secondary winding; its specific structure is as follows: Figure 5 or Figure 6 As shown, it specifically includes: a filter capacitor Cv and two rectifier diodes.
[0093] The specific connection relationships between the various components are as follows:
[0094] The cathode of the first rectifier diode Dz1 is connected to the same-name terminal of the first secondary winding, and the cathode of the second rectifier diode Dz2 is connected to the opposite-name terminal of the second secondary winding; the anodes of the first rectifier diode Dz1 and the second rectifier diode Dz2 are connected, and the connection point serves as the negative terminal of the DC side of the rectifier circuit 22; the opposite-name terminal of the first secondary winding and the same-name terminal of the second secondary winding are connected, and the connection point serves as the positive terminal of the DC side of the rectifier circuit 22; the two ends of the filter capacitor are connected to the positive terminal of the DC side of the rectifier circuit 22 and the negative terminal of the DC side of the rectifier circuit 22, respectively.
[0095] It should be noted that the above is only one specific implementation of the rectifier circuit 22. In practical applications, there are other implementations, including but not limited to this one. No specific implementation is specified here. The implementation can be determined according to the specific circumstances, and all of them are within the protection scope of this application.
[0096] Another embodiment of this application provides another implementation of the controller, which, in addition to the above-described implementation, further includes: a controller.
[0097] The control terminals of both the upper and lower switching transistors are connected to the controller; the controller is used to control the upper and lower switching transistors to conduct alternately.
[0098] Optionally, the controller can use a frequency modulation control strategy or a pulse width modulation strategy to regulate the output of the Buck circuit.
[0099] The features described above in the disclosed embodiments can be substituted or combined with each other, enabling those skilled in the art to implement or use this application. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.
Claims
1. A direct current converter, characterized by Comprise: a Buck circuit and at least one resonance network; wherein: the input end of the Buck circuit is the input end of the direct current converter, and the output end of the Buck circuit is one output end of the direct current converter; the input end and the output end of at least one switch tube in the Buck circuit are connected in parallel with the input end of the resonance network; and the output end of the resonance network is the other output end of the direct current converter; the sum of the resonance currents of all the resonance networks is a resonance total current, and the absolute value of the resonance total current is greater than or equal to the absolute value of a critical current before the upper switch tube is turned on; the upper switch tube is the switch tube connected to the positive electrode of the input end of the Buck circuit; the critical current is the resonance total current with the minimum absolute value and which makes the junction capacitance of the upper switch tube discharge before the upper switch tube is turned on.
2. The dc-dc converter of claim 1, wherein, The resonance network comprises: a resonance circuit and a rectifier circuit; wherein: the input end of the resonance circuit is the input end of the resonance network; the alternating current side of the rectifier circuit is connected to the output end of the resonance circuit; and the direct current side of the rectifier circuit is the output end of the resonance network.
3. The dc-dc converter of claim 2, wherein, The resonance circuit comprises: a resonance capacitor, a resonance inductor, an excitation inductor and a transformer; wherein: the resonance capacitor, the resonance inductor and the excitation inductor are connected in series to form a series branch, and the two ends of the series branch are the input end of the resonance circuit; the primary winding of the transformer is connected to the excitation inductor, and the secondary winding of the transformer is the output end of the resonance circuit.
4. The dc-dc converter of claim 3, wherein, In the resonance circuit, the absolute value of the resonance total current is greater than or equal to the absolute value of the critical current before the upper switch tube is turned on by setting the inductance value of each excitation inductor and / or the turns ratio of each transformer.
5. The dc-dc converter of claim 2, wherein, The resonance circuit comprises: a resonance capacitor, a resonance inductor and a transformer; wherein: the resonance capacitor, the resonance inductor and the primary winding of the transformer are connected in series to form a series branch, and the two ends of the series branch are the input end of the resonance circuit; the secondary winding of the transformer is the output end of the resonance circuit.
6. The dc-dc converter of claim 5, wherein, In the resonance circuit, the absolute value of the resonance total current is greater than or equal to the absolute value of the critical current before the upper switch tube is turned on by setting the turns ratio of each transformer.
7. The dc to dc converter of claim 2, wherein, The resonance circuit comprises a transformer, and the secondary winding of the transformer comprises: a first secondary winding and a second secondary winding; the rectifier circuit comprises: a filter capacitor and two rectifier diodes; wherein: the cathode of the first rectifier diode is connected to the same-named end of the first secondary winding, and the cathode of the second rectifier diode is connected to the different-named end of the second secondary winding; the anodes of the first rectifier diode and the second rectifier diode are connected, and the connection point is the negative electrode of the direct current side of the rectifier circuit; the different-named end of the first secondary winding and the same-named end of the second secondary winding are connected, and the connection point is the positive electrode of the direct current side of the rectifier circuit; the two ends of the filter capacitor are respectively connected to the positive electrode of the direct current side of the rectifier circuit and the negative electrode of the direct current side of the rectifier circuit.
8. The dc-dc converter according to any one of claims 1 to 7, characterized in that Further comprise: a controller; wherein: The control end of the upper switch tube and the control end of the lower switch tube are connected with the controller; the lower switch tube is a switch tube connected with the negative electrode of the input end of the Buck circuit; The controller is used for controlling the upper switch tube and the lower switch tube to be alternately conducted.
9. The dc to dc converter of claim 8, wherein, The controller adopts a frequency modulation control strategy or a pulse width modulation strategy to realize the output regulation of the Buck circuit.
Citation Information
Patent Citations
Single-stage LED driver circuit integrating bridgeless Boost and LLC circuits
CN107041036A