LLC circuit and switching power supply

Abstract

The invention discloses an LLC circuit and a switching power supply. The LLC circuit comprises an inverter circuit, a resonance circuit and a preset number of rectification circuits, the resonance circuit is respectively connected with the inverter circuit and the rectifying circuit and is used for converting the high-frequency alternating-current square wave into alternating-current voltage; the resonance circuit comprises a first inductor, a second inductor, N first primary windings, N second primary windings, a preset number of first secondary windings and a preset number of second secondary windings; the first inductor, the first primary winding, the second primary winding and the second inductor are connected in series at two ends of the inverter circuit; the first secondary winding and the second secondary winding are connected with the rectifying circuits in a one-to-one correspondence manner; the first inductor and the second inductor are symmetrically arranged, and the first primary winding and the second primary winding are symmetrically arranged. According to the LLC circuit, the noise can be reduced without adding a common-mode filter circuit, so that the circuit cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to an LLC circuit and a switching power supply. Background Art

[0002] The resonant conversion (Inductor-Inductor-Capacitor, LLC) circuit is used for DC / DC voltage conversion of switching power supplies. Due to its zero current switching (Zero Current Switching, ZCS) and zero voltage switching (Zero Voltage Switching, ZVS) characteristics, it can significantly reduce the loss of the switching tube, improve the efficiency of the circuit, and reduce the temperature rise. It is widely used in medium and high power switching power supplies.

[0003] LLC circuits include half-bridge LLC and full-bridge LLC. The existing LLC circuits have relatively large noises, and it is necessary to add large-sized filter components at the input port of the LLC circuit to reduce the propagation of noise, which is costly. Summary of the invention

[0004] The present invention provides an LLC circuit and a switching power supply, which can reduce noise while reducing the size of a filter component, thereby reducing the circuit cost.

[0005] In the first aspect, the present invention provides an LLC circuit, comprising: an inverter circuit, a resonant circuit and a preset number of rectifier circuits; wherein the preset number is M, M is an integer greater than or equal to 1 and less than or equal to 2N, and N is an integer greater than or equal to 1; the inverter circuit is used to convert a DC input voltage into a high-frequency AC square wave; the resonant circuit is connected to the inverter circuit and the rectifier circuit respectively, and is used to convert the high-frequency AC square wave into an AC voltage; the rectifier circuit is used to convert the AC voltage into a DC output voltage; the resonant circuit comprises a first inductor, a second inductor, N first primary windings, N second primary windings, a preset number of first secondary windings and a preset number of second secondary windings; the first inductor, the first primary winding, the second primary winding and the second inductor are connected in series at both ends of the inverter circuit, and the first secondary winding and the second secondary winding are connected to the rectifier circuit one-to-one; the first inductor and the second inductor are symmetrically arranged with the first capacitor, and the first primary winding and the second primary winding are symmetrically arranged.

[0006] Optionally, the inductance values ​​of the first inductor and the second inductor are the same, the number of turns of the first primary winding and the second primary winding are the same, and the number of turns of the first secondary winding and the second secondary winding are the same.

[0007] Optionally, the resonant circuit also includes a resonant unit, which includes a plurality of first capacitors and / or third inductors connected in series; the first inductor, the first primary winding, the resonant unit, the second primary winding and the second inductor are sequentially connected in series at both ends of the inverter circuit; the first inductor and the second inductor are symmetrically arranged about the resonant unit, and the first primary winding and the second primary winding are symmetrically arranged one by one about the resonant unit.

[0008] Optionally, the resonant circuit also includes Y second capacitors and Y third capacitors, where Y is an integer greater than or equal to 1; the first inductor, the first primary winding, the second capacitor, the second primary winding, the third capacitor and the second inductor are connected in series at both ends of the inverter circuit, and the second capacitor and the third capacitor are symmetrically arranged one by one.

[0009] Optionally, the LLC circuit further includes a DC power supply, which is connected to the inverter circuit and is used to provide a DC input voltage for the inverter circuit.

[0010] Optionally, the inverter circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the control end of the first switch tube is connected to the first control signal, the first end of the first switch tube is connected to the positive end of the DC power supply, and the second end of the first switch tube is respectively connected to the first end of the second switch tube and the first end of the resonant circuit; the control end of the second switch tube is connected to the second control signal, and the second end of the second switch tube is connected to the negative end of the DC power supply; the control end of the third switch tube is connected to the second control signal, the first end of the third switch tube is connected to the first end of the first switch tube, and the second end of the third switch tube is respectively connected to the first end of the fourth switch tube and the second end of the resonant circuit; the control end of the fourth switch tube is connected to the first control signal, and the second end of the fourth switch tube is connected to the second end of the second switch tube; wherein the first control signal and the second control signal are a pair of complementary PWM signals.

[0011] Optionally, the duty cycle range of the first control signal and the second control signal is 49% to 50%.

[0012] Optionally, the rectifier circuit includes a first diode, a second diode and a second capacitor; the first end of the first diode is connected to the first end of the first secondary winding, the second end of the first diode is connected to the first end of the second capacitor and serves as the first output end of the LLC circuit, the second end of the second capacitor is connected to the common end of the first secondary winding and the second secondary winding, and serves as the second output end of the LLC circuit; the first end of the second diode is connected to the first end of the second secondary winding, and the second end of the second diode is connected to the second end of the first diode.

[0013] In a second aspect, the present invention provides a switching power supply, characterized in that it includes the LLC circuit provided by any embodiment of the present invention.

[0014] Optionally, the switching power supply further includes a control circuit, and the control circuit is used to generate a first control signal and a second control signal.

[0015] The LLC circuit provided by the embodiment of the present invention is that the first inductor, the first primary winding, the first capacitor, the second primary winding and the second inductor are sequentially connected in series at both ends of the inverter circuit, the first secondary winding and the second secondary winding are connected to the rectifier circuit in a one-to-one correspondence, the first secondary winding and the second secondary winding are sequentially connected in series at both ends of the rectifier circuit, and the common end between the first secondary winding and the second secondary winding is connected to the rectifier circuit. By symmetrically arranging the first inductor and the second inductor, and symmetrically arranging the first primary winding and the second primary winding, the noise of the resonant circuit can be offset, thereby reducing the noise of the LLC circuit, and thereby reducing the size of the noise filter device required for the input port of the LLC circuit, thereby reducing the cost.

[0016] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 is a structural schematic diagram of an LLC circuit provided by an embodiment of the present invention;

[0019] Figure 2 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0020] Figure 3 This is a waveform diagram of a stable DC voltage after the noise of V1a and V1b is superimposed, provided by an embodiment of the present invention;

[0021] Figure 4 This is a waveform diagram of a stable DC voltage after the noise of V2a and V2b is superimposed, provided by an embodiment of the present invention;

[0022] Figure 5 This is a waveform diagram of a stable DC voltage after the noise of V3a and V3b is superimposed, provided by an embodiment of the present invention;

[0023] Figure 6 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0024] Figure 7 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0025] Figure 8 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0026] Fig. 9 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0027] Fig.10 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0028] Fig.11 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0029] Fig.12 is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention;

[0030] Fig.13 is a waveform diagram of a first control signal and a second control signal provided by an embodiment of the present invention;

[0031] Fig.14 It is a structural schematic diagram of a switching power supply provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0034] Figure 1 It is a structural schematic diagram of an LLC circuit provided by an embodiment of the present invention. Figure 2 FIG. 1 is a schematic diagram of another LLC circuit provided by an embodiment of the present invention. Figure 1 and Figure 2 As shown, the LLC circuit includes: an inverter circuit 11, a resonant circuit 12, and a preset number of rectifier circuits 13. The preset number is M, M is an integer greater than or equal to 1 and less than or equal to 2N, and N is an integer greater than or equal to 1.

[0035] The inverter circuit 11 is used to convert a DC input voltage into a high-frequency AC square wave.

[0036] The resonant circuit 12 is connected to the inverter circuit 11 and the rectifier circuit 13 respectively, and is used to convert the high-frequency AC square wave into an AC voltage. The rectifier circuit 13 is used to convert the AC voltage into a DC output voltage.

[0037] The resonant circuit 12 includes a first inductor L1, a second inductor L2, N first primary windings L1a, N second primary windings L2a, a preset number of first secondary windings L1b, and a preset number of second secondary windings L2b. Figure 1 The LLC circuit is schematically shown to include a rectifier circuit 13, a first primary winding L1a, a second primary winding L2a, a first secondary winding L1b, and a second secondary winding L2b. Figure 2 The case where the LLC circuit includes two rectifier circuits 13 , two first secondary windings L1 b and two second secondary windings L2 b is schematically shown.

[0038] The first inductor L1 , the first primary winding L1 a , the second primary winding L2 a and the second inductor L2 are connected in series at two ends of the inverter circuit 11 , and the first secondary winding L1 b and the second secondary winding L2 b are connected to the rectifier circuit 13 in a one-to-one correspondence.

[0039] The first inductor L1 and the second inductor L2 are symmetrically arranged, and the first primary winding L1a and the second primary winding L2a are symmetrically arranged.

[0040] Specifically, the inverter circuit 11 can be a half-bridge inverter circuit or a full-bridge inverter circuit. The inverter circuit may include a power switch device. By controlling the on and off of the power switch device, the DC input voltage is inverted into a high-frequency AC square wave output. The power switch device can be a metal-oxide semiconductor field-effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET), or an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT), or a gallium nitride (GaN) transistor. Optionally, the rectifier circuit 13 can be a full-wave rectifier circuit or a half-wave rectifier circuit, and the output end of the rectifier circuit 13 serves as the LLC circuit output end. When N is greater than or equal to 2, the output ends of the rectifier circuits 13 are connected in parallel.

[0041] The first inductor L1 and the second inductor L2 are symmetrically arranged, and the first primary winding L1a and the second primary winding L2a are symmetrically arranged. This can make the noise moving points of the LLC circuit become 6, and these noise moving points are numbered as: V1a, V1b, V2a, V2b, V3a, V3b; among which, V1a and V1b are symmetrical noises, V2a and V2b noises are symmetrical, and V3a and V3b noises are symmetrical.

[0042] Figure 3 This is a waveform diagram of a stable DC voltage formed by superimposing the noise of V1a and V1b provided by an embodiment of the present invention. Figure 4 This is a waveform diagram of a stable DC voltage formed by superimposing the noise of V2a and V2b provided by an embodiment of the present invention. Figure 5 This is a waveform diagram of a stable DC voltage after the noise of V3a and V3b is superimposed, provided by an embodiment of the present invention. Figures 3 to 5 , V represents voltage, and t represents time. After the symmetrical noises are superimposed on each other, the obtained V1a+V1b, V2a+V2b, and V3a+V3b are all stable DC voltages, that is, these high-frequency AC noises cancel each other out.

[0043] The LLC circuit provided by the embodiment of the present invention is configured by sequentially connecting the first inductor, the first primary winding, the first capacitor, the second primary winding and the second inductor in series at both ends of the inverter circuit, and the first secondary winding and the second secondary winding are connected to the rectifier circuit one by one. Figure 1In the embodiment, the first secondary winding and the second secondary winding are connected in series to both ends of the rectifier circuit, and the common end between the first secondary winding and the second secondary winding is connected to the rectifier circuit. By symmetrically arranging the first inductor and the second inductor, and symmetrically arranging the first primary winding and the second primary winding, the noise of the resonant circuit can be offset, thereby reducing the noise of the LLC circuit, and further reducing the size of the noise filter device required for the LLC circuit input port, thereby reducing the cost.

[0044] Based on the above embodiments, continue to refer to Figure 1 and Figure 2 Optionally, the first inductor L1 and the second inductor L2 have the same inductance value, the first primary winding L1a and the second primary winding L2a have the same number of turns, and the first secondary winding L2a and the second secondary winding L2b have the same number of turns. The "same" here is not limited to the absolute equality of the values ​​of the two. For example, the difference between the values ​​of the two can be within 5±%. The first inductor L1 and the second inductor L2 with the same inductance value can achieve balanced current distribution in the circuit. When the alternating current passes through, the two inductors have the same obstruction effect on the current, avoiding the uneven current caused by the difference in inductance, so that the circuit works more stably. For the transformer windings, the first primary winding L1a and the second primary winding L2a and the first secondary winding L1b and the second secondary winding L2b with the same number of turns can ensure that the voltage and current conversion ratios of the primary and secondary sides are consistent when the transformer is working. This helps to maintain the stability of the output voltage and reduce fluctuations. In addition, the symmetrical circuit structure helps to reduce electromagnetic interference. The magnetic field generated by the inductor and winding with the same parameters is more symmetrical when working, and the part that cancels each other increases, thereby reducing the electromagnetic radiation to the outside world. At the same time, it also reduces the impact of the external electromagnetic field on the circuit and improves the circuit's anti-interference ability.

[0045] Figure 6 It is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention. Figure 7 It is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention. Figure 8 FIG. 1 is a schematic diagram of another LLC circuit provided by an embodiment of the present invention. Figures 6 to 8 As shown, optionally, the resonant circuit 12 further includes a resonant unit 120, and the resonant unit 120 includes a plurality of first capacitors C1 and / or third inductors L3 connected in series. The first inductor L1, the first primary winding L1a, the resonant unit 120, the second primary winding L2a, and the second inductor L2 are sequentially connected in series at both ends of the inverter circuit 11.

[0046] in, Figure 6 The case where the resonance unit 120 includes a first capacitor C1 is schematically shown. Figure 7The case where the resonance unit 120 includes two first capacitors C1 and one third inductor L3 is schematically shown, wherein the first first capacitor C1A and the second first capacitor C1B are symmetrically arranged with respect to the third inductor L3. Figure 8 The case where the resonance unit 120 includes two first capacitors C1 is schematically shown.

[0047] Fig. 9 It is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention. Fig.10 FIG. 1 is a schematic diagram of another LLC circuit provided by an embodiment of the present invention. Fig. 9 and Fig.10 As shown, optionally, the resonant circuit further includes Y second capacitors C2 and Y third capacitors C3, where Y is an integer greater than or equal to 1. The first inductor L1, the first primary winding L1a, the second capacitor C2, the second primary winding L2a, the third capacitor C3 and the second inductor L2 are connected in series at both ends of the inverter circuit 11, and the second capacitors C2 and the third capacitors C3 are symmetrically arranged one by one.

[0048] Fig.11 It is a structural schematic diagram of another LLC circuit provided by an embodiment of the present invention. Fig.12 FIG. 1 is a schematic diagram of another LLC circuit provided by an embodiment of the present invention. Fig.11 and Fig.12 As shown, the LLC circuit further includes a DC power supply Uin, which is connected to the inverter circuit 11 and is used to provide a DC input voltage to the inverter circuit 11.

[0049] In some embodiments, the required DC input voltage range can be determined according to the design requirements of the inverter circuit 11. Different inverter circuits 11 may have specific requirements for the input voltage. For example, some inverter circuits 11 may require a specific rated voltage to work properly, or achieve optimal performance within a certain voltage range. The operating requirements of the entire LLC circuit can also be considered, including the voltage requirements of the load, the voltage compatibility of the resonant circuit 12 and the rectifier circuit 13, etc. Ensure that the output voltage of the DC power supply can meet the voltage requirements of the entire system to ensure the normal operation of the circuit.

[0050] Based on the above embodiments, continue to refer to Fig.11 Optionally, the inverter circuit 11 includes a first switch tube Q1, a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4.

[0051] The control end of the first switch tube Q1 is connected to the first control signal sig1, the first end of the first switch tube Q1 is connected to the positive end of the DC power supply Uin, and the second end of the first switch tube Q1 is respectively connected to the first end of the second switch tube Q2 and the first end of the resonant circuit 12.

[0052] The control end of the second switch tube Q2 is connected to the second control signal sig2, and the second end of the second switch tube Q2 is connected to the negative end of the DC power supply Uin.

[0053] The control end of the third switch tube Q3 is connected to the second control signal sig2, the first end of the third switch tube Q3 is connected to the first end of the first switch tube Q1, and the second end of the third switch tube Q3 is respectively connected to the first end of the fourth switch tube Q4 and the second end of the resonant circuit 12.

[0054] A control end of the fourth switch tube Q4 is connected to the first control signal sig1 , and a second end of the fourth switch tube Q4 is connected to a second end of the second switch tube Q2 .

[0055] The first control signal sig1 and the second control signal sig2 are a pair of complementary PWM signals. That is, when the first control signal sig1 is at a high level, the second control signal sig2 is at a low level; conversely, when the first control signal sig1 is at a low level, the second control signal sig2 is at a high level. Such a control method enables the four switch tubes to be alternately turned on and off, thereby converting the DC voltage of the DC power supply Uin into a high-frequency AC square wave and outputting it to the resonant circuit 12.

[0056] When the first switch tube Q1 and the fourth switch tube Q4 are turned on, and the second switch tube Q2 and the third switch tube Q3 are turned off, the voltage of the DC power supply Uin is positively applied to the resonant circuit, and the current starts from the positive electrode of the DC power supply Uin, passes through the first switch tube Q1, the resonant circuit 12 and the fourth switch tube Q4 in sequence, and then returns to the negative electrode of the DC power supply Uin. When the second switch tube Q2 and the third switch tube Q3 are turned on, and the first switch tube Q1 and the fourth switch tube Q4 are turned off, the voltage of the DC power supply Uin is reversely applied to the resonant circuit 12, and the current starts from the positive electrode of the DC power supply Uin, passes through the third switch tube Q3, the resonant circuit 12 and the second switch tube Q2 in sequence, and then returns to the negative electrode of the DC power supply Uin.

[0057] Optionally, the duty cycle range of the first control signal sig1 and the second control signal sig2 is 49% to 50%. Exemplarily, the duty cycle range of the first control signal sig1 and the second control signal sig2 is 50%. For a full-bridge inverter circuit composed of four switch tubes (a first switch tube Q1, a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4), a duty cycle of 50% means that in a switching cycle, each switch tube is turned on and off for half of the time. In this way, the square wave voltage output by the inverter circuit 11 can have a more symmetrical waveform. The symmetrical square wave voltage helps to improve the working stability of the resonant circuit 12. In the LLC circuit, the first inductor L1, the second inductor L2, the first capacitor and the primary winding of the transformer work together to resonate the input square wave voltage.

[0058] Optionally, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 are all NMOS tubes. The first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 are all connected to body diodes in reverse parallel. The body diode is used for freewheeling. When the switch tube is turned off, a freewheeling path is required because the current in the inductor cannot change suddenly. At this time, the body diode can provide a freewheeling channel for the inductor current to prevent the inductor from generating an excessively high induced electromotive force, thereby protecting the switch tube and other circuit components.

[0059] Based on the above embodiments, continue to refer to Fig.11 and Fig.12 Optionally, the rectifier circuit 13 includes a first diode D1, a second diode D2 and a second capacitor C2.

[0060] The first end of the first diode D1 is connected to the first end of the first secondary winding L1b, the second end of the first diode D1 is connected to the first end of the second capacitor C2 and serves as the first output end OUT1 of the LLC circuit, and the second end of the second capacitor C2 is connected to the common end of the first secondary winding L1b and the second secondary winding L2b and serves as the second output end OUT2 of the LLC circuit.

[0061] A first end of the second diode D2 is connected to a first end of the second secondary winding L2 b , and a second end of the second diode D2 is connected to a second end of the first diode D1 .

[0062] Specifically, when the secondary winding of the transformer induces an AC voltage, during the positive half cycle, the current charges the second capacitor C2 through the first secondary winding L1b and the first diode D1, and provides current to the load. During the negative half cycle of the AC voltage, the current charges the second capacitor C2 through the second secondary winding L2b and the second diode D2, and provides current to the load. The second capacitor C2 plays a filtering role, making the rectified DC output smoother and more stable, and reducing the ripple of the output voltage.

[0063] Fig.13 is a waveform diagram of a first control signal and a second control signal provided by an embodiment of the present invention, combined with Fig.11 and Fig.13 , the working principle of the LLC circuit is:

[0064] First, in the first time period t0, the first control signal sig1 and the second control signal sig2 are both at low levels, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 are all turned off, and the first inductor L1, the second inductor L2, the first primary winding L1a, the second primary winding L2a and the first capacitor C1 resonate. The resonance causes the voltage of the first node A to rise from 0V to a high voltage, and the voltage of the second node B to drop from a high voltage to 0V. In the remaining time, the body diodes of the first switch tube Q1 and the fourth switch tube Q4 are turned on, preparing for the soft switching of the device in the next time.

[0065] In the second time period t1, the second control signal sig2 is at a low level, the first control signal sig1 is at a high level, the first switch tube Q1 and the fourth switch tube Q4 are turned on, the second switch tube Q2 and the third switch tube Q3 are turned off, the first primary winding L1a and the second primary winding L2a are clamped by the secondary side, and at this time, the first primary winding L1a, the second primary winding L2a and the first capacitor C1 resonate, and the input voltage transfers power to the secondary side while also charging and storing energy in the first primary winding L1a, the second primary winding L2a and the first capacitor C1.

[0066] In the third time period t2, the first control signal sig1 and the second control signal sig2 are both at low levels, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 are all turned off, the first inductor L1, the second inductor L2, the first primary winding L1a, the second primary winding L2a and the first capacitor C1 resonate again, and the resonance causes the voltage of the first node A to drop from a high voltage to 0V, and the second node B to rise from 0V to a high voltage, and the body diodes of the second switch tube Q2 and the third switch tube Q3 are turned on during the remaining time of the third time period T2.

[0067] In the fourth time period t3, the high and low levels of the first control signal sig1 and the second control signal sig2 are opposite to those in the second time period t1, the switching state of each switch tube is opposite to that in the second time period t1, and the current flow direction is also opposite to that in the second time period t1, which will not be repeated here.

[0068] Based on the same inventive concept, the present invention also provides a switching power supply. Fig.14 Schematic diagram of a switching power supply provided by an embodiment of the present invention. Fig.14 As shown, the LLC circuit 1 provided by any embodiment of the present invention has the same functional modules and beneficial effects as the LLC circuit, which will not be described in detail here. Fig.14 The switching power supply includes Fig.11 The case of the LLC circuit shown.

[0069] Optionally, continue to refer to Fig.14The switching power supply further includes a control circuit 2, and the control circuit 2 is used to generate a first control signal sig1 and a second control signal sig2.

[0070] Optionally, the control circuit 2 may include a single chip microcomputer, and may also include a digital signal processor (Digital Signal Processor, DSP) or a field programmable gate array (Field Programmable Gate Array, FPGA).

[0071] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An LLC circuit, characterized in that: include: An inverter circuit, a resonant circuit, and a preset number of rectifier circuits; wherein the preset number is M, M is an integer greater than or equal to 1 and less than or equal to 2N, and N is an integer greater than or equal to 1; The inverter circuit is used to convert the DC input voltage into a high-frequency AC square wave; The resonant circuit is connected to the inverter circuit and the rectifier circuit respectively, and is used to convert the high-frequency AC square wave into an AC voltage; the rectifier circuit is used to convert the AC voltage into a DC output voltage; The resonant circuit comprises a first inductor, a second inductor, N first primary windings and N second primary windings, the preset number of first secondary windings and the preset number of second secondary windings; The first inductor, the first primary winding, the second primary winding and the second inductor are connected in series at two ends of the inverter circuit, and the first secondary winding and the second secondary winding are connected to the rectifier circuit in a one-to-one correspondence; The first inductor and the second inductor are symmetrically arranged, and the first primary winding and the second primary winding are symmetrically arranged one by one.

2. The LLC circuit according to claim 1, characterized in that: The first inductor and the second inductor have the same inductance value, the first primary winding and the second primary winding have the same number of turns, and the first secondary winding and the second secondary winding have the same number of turns.

3. The LLC circuit according to claim 1, characterized in that: The resonant circuit further comprises a resonant unit, wherein the resonant unit comprises a plurality of first capacitors and / or third inductors connected in series; The first inductor, the first primary winding, the resonant unit, the second primary winding and the second inductor are sequentially connected in series at two ends of the inverter circuit; The first inductor and the second inductor are symmetrically arranged with respect to the resonance unit, and the first primary winding and the second primary winding are symmetrically arranged one by one with respect to the resonance unit.

4. The LLC circuit according to claim 1, characterized in that: The resonant circuit further includes Y second capacitors and Y third capacitors, where Y is an integer greater than or equal to 1; The first inductor, the first primary winding, the second capacitor, the second primary winding, the third capacitor and the second inductor are connected in series at both ends of the inverter circuit, and the second capacitor and the third capacitor are symmetrically arranged one by one.

5. The LLC circuit according to claim 1, characterized in that: It also includes a DC power supply, which is connected to the inverter circuit and is used to provide the DC input voltage to the inverter circuit.

6. The LLC circuit according to claim 5, characterized in that: The inverter circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; The control end of the first switch tube receives a first control signal, the first end of the first switch tube is connected to the positive end of the DC power supply, and the second end of the first switch tube is respectively connected to the first end of the second switch tube and the first end of the resonant circuit; The control end of the second switch tube receives a second control signal, and the second end of the second switch tube is connected to the negative end of the DC power supply; The control end of the third switch tube is connected to the second control signal, the first end of the third switch tube is connected to the first end of the first switch tube, and the second end of the third switch tube is respectively connected to the first end of the fourth switch tube and the second end of the resonant circuit; The control end of the fourth switch tube is connected to the first control signal, and the second end of the fourth switch tube is connected to the second end of the second switch tube; The first control signal and the second control signal are a pair of complementary PWM signals.

7. The LLC circuit according to claim 6, characterized in that: The duty cycle range of the first control signal and the second control signal is 49% to 50%.

8. The LLC circuit according to claim 1, characterized in that: The rectifier circuit includes a first diode, a second diode and a second capacitor; A first end of the first diode is connected to a first end of the first secondary winding, a second end of the first diode is connected to a first end of the second capacitor and serves as a first output end of the LLC circuit, and a second end of the second capacitor is connected to a common end of the first secondary winding and the second secondary winding and serves as a second output end of the LLC circuit; A first end of the second diode is connected to a first end of the second secondary winding, and a second end of the second diode is connected to a second end of the first diode.

9. A switching power supply, characterized in that: Comprising the LLC circuit as claimed in any one of claims 1 to 8.

10. The switching power supply according to claim 9, characterized in that: The switching power supply further comprises a control circuit, wherein the control circuit is configured to generate a first control signal and a second control signal.

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