LLC symmetric half-bridge power converter
By using the distributed resonant capacitor configuration and the leakage inductance of the plane transformer as the resonant inductor in the LLC resonant power converter, the problems of high input current ripple and root mean square value and large magnetic device occupancy area in the prior art are solved, and a high power density design is achieved.
Patent Information
- Application Number
- CN202421703261.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-04-29
- Estimated Expiration
- 2034-08-30
AI Technical Summary
The existing LLC resonant power converters have high input current ripple and root mean square values, and the root mean square current flowing through the resonant capacitor is large, which requires a capacitor model with high withstand voltage. The resonant inductor and transformer are separately set, occupying a large PCB area, affecting the power density.
The distributed resonant capacitor configuration is adopted, and the leakage inductance of the plane transformer is used as the resonant inductor. The voltage equalization resistor ensures that the voltages of the upper and lower resonant capacitors on the bridge arm are basically the same, reducing the root mean square current processing volume of the capacitor.
The power density is improved, the capacitance value and voltage requirements of the capacitor are reduced, the problem of large area occupied by magnetic devices is avoided, and the high power density design capability of the power module is improved.
Smart Images
Figure CN222814382U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a power converter, in particular to an LLC symmetrical half-bridge power converter. Background Art
[0002] With the development of power electronics technology, LLC resonant power converters are widely used in various power systems due to their high efficiency and good dynamic performance. Traditional LLC converters usually adopt full-bridge or asymmetric half-bridge structures. Asymmetric half-bridge topology generally adopts a single resonant capacitor configuration, such as Figure 1 As shown. Its input current ripple and root mean square (RMS) value are high, and the root mean square current flowing through the resonant capacitor is large, and a capacitor with high withstand voltage needs to be selected. The resonant inductor and transformer are set separately, and the PCB occupies a large area, which is not conducive to improving power density.
[0003] Therefore, how to develop a power converter that can improve the above-mentioned prior art is an urgent need. Utility Model Content
[0004] The technical problem to be solved by the utility model is to provide an LLC symmetrical half-bridge power converter with high power density and a voltage reduction function.
[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: an LLC symmetrical half-bridge power converter, comprising an input filter inductor Lin, an input filter capacitor Cin, a first bridge arm, a second bridge arm, a resonant inductor Lr, a planar transformer, a rectifier first bridge arm, a rectifier second bridge arm, and an output capacitor Co;
[0006] The input filter capacitor Cin is connected between the positive input terminal and the negative input terminal;
[0007] One end of the input filter inductor Lin is connected to the input positive end, and the other end of the input filter inductor is connected to one end of the input filter capacitor Cin; the first input bridge arm and the second input bridge arm are connected in parallel to the two ends of the input filter capacitor Cin.
[0008] The output capacitor Co is connected between the positive output terminal and the negative output terminal;
[0009] The first rectifier bridge arm and the second rectifier bridge arm are both electrically connected between the output positive terminal and the output negative terminal and are connected in parallel with the output capacitor Co;
[0010] The planar transformer comprises a primary winding and a secondary winding, wherein two ends of the primary winding are electrically connected to the midpoint of the first input bridge arm and the midpoint of the second input bridge arm, respectively; a resonant inductor Lr is connected in series between the first input bridge arm and one end of the transformer winding; and two ends of the secondary winding are electrically connected to the midpoint of the first rectifier bridge arm and the midpoint of the second rectifier bridge arm, respectively;
[0011] The first input bridge arm includes an upper power switch tube Q1 and a lower power switch tube Q2, wherein the upper power switch tube Q1 and the lower power switch tube Q2 are connected in series and electrically connected between two ends of the input filter capacitor Cin;
[0012] The input second bridge arm includes a first capacitor Cr1, a second capacitor Cr2, a first equalizing resistor R1, and a second equalizing resistor R2. The first capacitor Cr1 and the second capacitor Cr2 are connected in series and electrically connected between the input positive terminal and the input negative terminal, and are connected in parallel with the input first bridge arm. The first capacitor Cr1 is equal to the second capacitor Cr2. The first equalizing resistor R1 is connected in parallel with the first capacitor Cr1, the second equalizing resistor R2 is connected in parallel with the second capacitor Cr2, and the first equalizing resistor R1 and the second equalizing resistor R2 are equal, so that the voltages across the first capacitor Cr1 and the second capacitor Cr2 are substantially the same at any time.
[0013] The first rectifier bridge arm includes a first power switch tube S1 and a second power switch tube S2, which are connected in series and electrically connected between the output positive terminal and the output negative terminal;
[0014] The second rectifier bridge arm includes a third power switch tube S3 and a fourth power switch tube S4, wherein the third power switch tube S3 and the fourth power switch tube S4 are connected in series and electrically connected between the output positive terminal and the output negative terminal, and are connected in parallel with the first rectifier bridge arm;
[0015] The planar transformer comprises a winding module and two magnetic core modules respectively buckled on both sides of the winding module; the winding module comprises a circuit board, the circuit board comprises a plurality of inner layer boards pressed together, a through magnetic core center column through hole is provided in the middle of the circuit board, a through first side column through hole and a through second side column through hole are symmetrically provided on both sides of the middle through hole, and the areas of the middle through hole are not equal to those of the first side column through hole and the second side column through hole.
[0016] The magnetic core module is provided with a magnetic core middle column matched with the magnetic core middle column through hole, a first magnetic core side column matched with the first side column through hole, and a second magnetic core side column matched with the second side column through hole. The top surface of the magnetic core middle column, the top surface of the first magnetic core side column, and the top surface of the second magnetic core side column of the magnetic core modules on both sides are all in contact with each other.
[0017] The secondary winding is arranged on the inner layer board of the circuit board around the through hole of the center column of the magnetic core, and the primary winding is arranged on the inner layer board of the circuit board around the through hole of the center column of the magnetic core and is located on a different inner layer board from the secondary winding. The secondary winding and the primary winding both include at least one turn of coil; the resonant inductor Lr is the leakage inductance of this planar transformer.
[0018] As a preferred solution, the first power switch tube S1 on the first rectifier bridge arm, the fourth power switch tube S4 on the second rectifier bridge arm and the upper power switch tube Q1 on the first input bridge arm are turned on simultaneously in a switching cycle, and are turned off in advance before the upper power switch tube Q1 is turned off; the second power switch tube S2 on the first rectifier bridge arm, the third power switch tube S3 on the second rectifier bridge arm and the lower power switch tube Q2 on the first input bridge arm are turned on simultaneously in a switching cycle, and are turned off in advance before the lower power switch tube Q2 is turned off; the turn-on moments of the upper power switch tube Q1 and the lower power switch tube Q2 on the first input bridge arm are staggered by 180°.
[0019] As a preferred solution, a safety spacing of 0.01 mm to 1 mm is provided between different inner layers of the substrate where the secondary winding and the primary winding are located.
[0020] As a preferred solution, the first side column through hole is arranged at an edge position of the circuit board and is connected to the outside.
[0021] The beneficial effects of the utility model are as follows: the power converter of the utility model adopts a distributed resonant capacitor configuration, the resonant capacitor only handles half of the root mean square current, and the required capacitance is only half of that of a single resonant capacitor, and the capacitor voltage is only half of that of a single resonant capacitor. By setting a voltage-equalizing resistor, it is ensured that the voltages of the upper and lower resonant capacitors of the bridge arm are basically the same, avoiding the imbalance of the positive and negative half-cycles of the resonant cavity current due to the uneven voltage of the capacitor. By using the transformer leakage inductance as the resonant inductor, there is no need to set a separate resonant inductor, which solves the problem of large board area occupied by magnetic devices in the traditional setting method, and is conducive to the design of high power density of the power module. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 An existing asymmetric half-bridge resonant converter circuit;
[0023] Figure 2 is a schematic diagram of the circuit topology of the power converter;
[0024] Figure 3 is a three-dimensional structural diagram of the power converter;
[0025] Figure 4 is a three-dimensional structural diagram of the power converter from another angle;
[0026] Figure 5 is a schematic diagram of the structure of a circuit board of the power converter;
[0027] Figure 6 is a schematic diagram of a multi-layer structure of a circuit board of the power converter;
[0028] Figure 7 is a schematic structural diagram of a magnetic core module of the power converter;
[0029] Figure 8 It is a schematic diagram of the structure of the assembled circuit board and magnetic core module of the power converter;
[0030] Fig. 9 This is the equivalent circuit diagram of the working mode 1 of the power converter;
[0031] Fig.10 This is the equivalent circuit diagram of the working mode 2 of the power converter;
[0032] Fig.11 This is the equivalent circuit diagram of the working mode 3 of the power converter;
[0033] Fig.12 is the waveform diagram of the power converter;
[0034] Fig.13 This is the primary and secondary side MOS driving waveform of this power converter;
[0035] In the figure: 10, winding module; 11, circuit board; 12, first side column through hole; 13, middle column through hole; 14, second side column through hole;
[0036] 20. Magnetic core module; 21. First magnetic core side column; 22. Magnetic core middle column; 23. Second magnetic core side column; DETAILED DESCRIPTION
[0037] The specific implementation scheme of the utility model is described in detail below in conjunction with the accompanying drawings.
[0038] like Figure 1-8 As shown, an LLC symmetrical half-bridge power converter includes an input filter inductor Lin, an input filter capacitor Cin, a first bridge arm, a second bridge arm, a resonant inductor Lr, a planar transformer T, a rectifier first bridge arm, a rectifier second bridge arm, and an output capacitor Co;
[0039] The input filter capacitor Cin is connected between the positive input terminal and the negative input terminal;
[0040] One end of the input filter inductor Lin is connected to the input positive end, and the other end of the input filter inductor is connected to one end of the input filter capacitor Cin; the first input bridge arm and the second input bridge arm are connected in parallel to the two ends of the input filter capacitor Cin.
[0041] The output capacitor Co is connected between the positive output terminal and the negative output terminal;
[0042] The first rectifier bridge arm and the second rectifier bridge arm are both electrically connected between the output positive terminal and the output negative terminal and are connected in parallel with the output capacitor Co;
[0043] The planar transformer T comprises a primary winding and a secondary winding, wherein two ends of the primary winding are electrically connected to the midpoint of the first input bridge arm and the midpoint of the second input bridge arm, respectively, a resonant inductor Lr is connected in series between the first input bridge arm and one end of the transformer winding, and two ends of the secondary winding are electrically connected to the midpoint of the first rectifier bridge arm and the midpoint of the second rectifier bridge arm, respectively;
[0044] The first input bridge arm includes an upper power switch tube Q1 and a lower power switch tube Q2, wherein the upper power switch tube Q1 and the lower power switch tube Q2 are connected in series and electrically connected between two ends of the input filter capacitor Cin;
[0045] The input second bridge arm includes a first capacitor Cr1, a second capacitor Cr2, a first equalizing resistor R1, and a second equalizing resistor R2. The first capacitor Cr1 and the second capacitor Cr2 are connected in series and electrically connected between the input positive terminal and the input negative terminal, and are connected in parallel with the input first bridge arm. The first capacitor Cr1 is equal to the second capacitor Cr2. The first equalizing resistor R1 is connected in parallel with the first capacitor Cr1, the second equalizing resistor R2 is connected in parallel with the second capacitor Cr2, and the first equalizing resistor R1 and the second equalizing resistor R2 are equal, so that the voltages across the first capacitor Cr1 and the second capacitor Cr2 are substantially the same at any time.
[0046] The first rectifier bridge arm includes a first power switch tube S1 and a second power switch tube S2, which are connected in series and electrically connected between the output positive terminal and the output negative terminal;
[0047] The second rectifier bridge arm includes a third power switch tube S3 and a fourth power switch tube S4, wherein the third power switch tube S3 and the fourth power switch tube S4 are connected in series and electrically connected between the output positive terminal and the output negative terminal, and are connected in parallel with the first rectifier bridge arm;
[0048] The planar transformer includes a winding module 10 and two magnetic core modules 20 respectively buckled on both sides of the winding module; the winding module 10 includes a circuit board 11, which is formed by pressing a plurality of inner layer boards together, a through magnetic core center column through hole 13 is provided in the middle of the circuit board 11, and a through first side column through hole 12 and a second side column through hole 14 are symmetrically provided on both sides of the middle through hole, and the first side column through hole 12 is provided at an edge position of the circuit board 11 and is connected to the outside. The area of the middle through hole is not equal to that of the first side column through hole 12 and the second side column through hole 14.
[0049] The magnetic core module 20 is provided with a magnetic core middle column 22 matched with the magnetic core middle column through hole 13, a first magnetic core side column 21 matched with the first side column through hole 12, and a second magnetic core side column 23 matched with the second side column through hole 14. The top surfaces of the magnetic core middle column 22, the first magnetic core side column 21, and the second magnetic core side column 23 of the magnetic core modules 20 on both sides are all in contact with each other.
[0050] The secondary winding is arranged on the inner layer board of the circuit board 11 around the through hole 13 in the center column of the magnetic core, and the primary winding is arranged on the inner layer board of the circuit board 11 around the through hole 13 in the center column of the magnetic core and is located on a different inner layer board from the secondary winding. Both the secondary winding and the primary winding include at least one turn of coil. A safety spacing of 0.01mm-1mm is arranged between different inner layers of the substrate where the secondary winding and the primary winding are located. The resonant inductor Lr is the leakage inductance of the planar transformer.
[0051] The first power switch tube S1 on the first rectifier bridge arm, the fourth power switch tube S4 on the second rectifier bridge arm and the upper power switch tube Q1 on the first input bridge arm are turned on simultaneously in a switching cycle, and are turned off in advance before the upper power switch tube Q1 is turned off;
[0052] The second power switch tube S2 on the first rectifier bridge arm, the third power switch tube S3 on the second rectifier bridge arm and the lower power switch tube Q2 on the first input bridge arm are turned on at the same time in a switching cycle, and are turned off in advance before the lower power switch tube Q2 is turned off; the upper power switch tube Q1 on the first input bridge arm is 180° out of phase with the lower power switch tube Q2 when they are turned on.
[0053] like Figures 9 to 13 As shown, the first half cycle of the converter is mainly divided into three working modes, as follows:
[0054] Mode 1 [t0-t1]: At t0, the output junction capacitor of the upper power switch tube Q1 is discharged, the anti-parallel diode of the upper power switch tube Q1 begins to conduct, and the drive signal V is applied. gs1 , the power switch Q1 on the switch tube is turned on at zero voltage, and the resonant inductor L r Resonance occurs with the first capacitor Cr1, and the first capacitor Cr1 discharges, and the path is as follows Figure 3 As shown by the green arrow, the resonant inductor L r and the second capacitor C r2 , input capacitor C in Resonance occurs, the second capacitor Cr2 is charged, and the input filter capacitor Cin is discharged. The path is as follows Figure 3 As shown by the red arrows. At this time, the first power switch tube S1 and the fourth power switch tube S4 on the secondary side are turned on at zero current, and the excitation inductance L m The voltage across the terminals is clamped to n*V o , the magnetizing inductor current i m The primary side of the planar transformer T is positive at the top and negative at the bottom, transferring energy to the secondary side of the transformer. When the current of the first power switch tube S1 and the fourth power switch tube S4 drops to 0 at time t1, this mode ends;
[0055] Mode 2 [t1-t2]: resonant current i r is exactly equal to the excitation current i m ,ir =i m >0, the upper power switch tube Q1 is still forward conducting, and the resonant inductor L r , the equivalent excitation inductance L of the planar transformer T m Resonance occurs with the first capacitor Cr1, and the discharge current of the first capacitor Cr1 gradually decreases to 0. The discharge path is as follows: Figure 4 As shown by the green arrow, the resonant inductor L r , excitation inductance Lm and second capacitor Cr2, input capacitor C in Resonance occurs, the second capacitor Cr2 continues to charge, the input filter capacitor Cin discharge current decreases to 0 and starts to charge, the path is as follows Figure 4 As shown by the red arrow, the excitation inductance is no longer clamped by the output voltage. However, since the excitation inductance is much larger than the resonant inductance, the excitation current can be considered unchanged. The current of the secondary rectifier is already zero, and the planar transformer does not transfer energy to the secondary side. The output capacitor C o Transfer energy to the output load. When the driving signal V gs1 When closed, this modal ends.
[0056] Mode 3 [t2-t3]: The converter enters the dead zone, the upper power switch Q1 is turned off, the junction capacitance of the upper power switch Q1 starts to charge, the lower power switch Q2 is turned on, and the junction capacitance of the lower power switch Q2 starts to discharge. The charging and discharging current is the excitation current i m The first capacitor Cr1 starts to charge, and the input capacitor Cin continues to charge. When the junction capacitance of the lower power switch tube Q2 is discharged at time t3, the anti-parallel diode of the lower power switch tube Q2 is turned on, and this mode ends.
[0057] The main modes of the second half of the cycle are similar to those of the first half of the cycle mentioned above and will not be repeated here.
[0058] The switch tube can be a power semiconductor device such as Si MOSFET, GaN HEMT, SiC MOSFET, etc. The first power switch tube S1, the second power switch tube S2, the third power switch tube S3, and the fourth power switch tube S4 work in a synchronous rectification mode, which can be replaced by a diode.
[0059] The above-mentioned embodiments are only illustrative of the principles and effects of the invention, as well as some embodiments of its application, and are not intended to limit the invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the invention, and all of these belong to the protection scope of the invention.
Claims
1. An LLC symmetrical half-bridge power converter, comprising an input filter inductor Lin, an input filter capacitor Cin, a first bridge arm, a second bridge arm, a resonant inductor Lr, a planar transformer, a rectifier first bridge arm, a rectifier second bridge arm, and an output capacitor Co; The input filter capacitor Cin is connected between the positive input terminal and the negative input terminal; One end of the input filter inductor Lin is connected to the input positive end, and the other end of the input filter inductor is connected to one end of the input filter capacitor Cin; the input first bridge arm and the input second bridge arm are connected in parallel to the two ends of the input filter capacitor Cin, and the output capacitor Co is connected between the output positive end and the output negative end; The first rectifier bridge arm and the second rectifier bridge arm are both electrically connected between the output positive terminal and the output negative terminal and are connected in parallel with the output capacitor Co; The planar transformer comprises a primary winding and a secondary winding, the two ends of the primary winding are respectively electrically connected to the midpoint of the first input bridge arm and the midpoint of the second input bridge arm, the resonant inductor Lr is connected in series between the first input bridge arm and one end of the transformer winding, and the two ends of the secondary winding are respectively electrically connected to the midpoint of the first rectifier bridge arm and the midpoint of the second rectifier bridge arm; The first input bridge arm includes an upper power switch tube Q1 and a lower power switch tube Q2, wherein the upper power switch tube Q1 and the lower power switch tube Q2 are connected in series and electrically connected between two ends of the input filter capacitor Cin; The input second bridge arm includes a first capacitor Cr1, a second capacitor Cr2, a first equalizing resistor R1, and a second equalizing resistor R2. The first capacitor Cr1 and the second capacitor Cr2 are connected in series and electrically connected between the input positive terminal and the input negative terminal, and are connected in parallel with the input first bridge arm. The first capacitor Cr1 is equal to the second capacitor Cr2. The first equalizing resistor R1 is connected in parallel with the first capacitor Cr1, the second equalizing resistor R2 is connected in parallel with the second capacitor Cr2, and the first equalizing resistor R1 and the second equalizing resistor R2 are equal, so that the voltages across the first capacitor Cr1 and the second capacitor Cr2 are substantially the same at any time. The first rectifier bridge arm includes a first power switch tube S1 and a second power switch tube S2, which are connected in series and electrically connected between the output positive terminal and the output negative terminal; The second rectifier bridge arm includes a third power switch tube S3 and a fourth power switch tube S4, wherein the third power switch tube S3 and the fourth power switch tube S4 are connected in series and electrically connected between the output positive terminal and the output negative terminal, and are connected in parallel with the first rectifier bridge arm; The planar transformer comprises a winding module and two magnetic core modules respectively buckled on both sides of the winding module; the winding module comprises a circuit board, the circuit board comprises a plurality of inner layer boards pressed together, a through magnetic core center column through hole is provided in the middle of the circuit board, a through first side column through hole and a through second side column through hole are symmetrically provided on both sides of the middle through hole, and the areas of the middle through hole are not equal to those of the first side column through hole and the second side column through hole. The magnetic core module is provided with a magnetic core middle column matched with the magnetic core middle column through hole, a first magnetic core side column matched with the first side column through hole, and a second magnetic core side column matched with the second side column through hole. The top surface of the magnetic core middle column, the top surface of the first magnetic core side column, and the top surface of the second magnetic core side column of the magnetic core modules on both sides are all in contact with each other. The secondary winding is arranged on the inner layer board of the circuit board around the through hole of the center column of the magnetic core, and the primary winding is arranged on the inner layer board of the circuit board around the through hole of the center column of the magnetic core and is located on a different inner layer board from the secondary winding. The secondary winding and the primary winding both include at least one turn of coil; the resonant inductor Lr is the leakage inductance of this planar transformer.
2. An LLC symmetrical half-bridge power converter as claimed in claim 1, characterized in that: The first power switch tube S1 on the first rectifier bridge arm, the fourth power switch tube S4 on the second rectifier bridge arm and the upper power switch tube Q1 on the first input bridge arm are turned on simultaneously in a switching cycle, and are turned off in advance before the upper power switch tube Q1 is turned off; the second power switch tube S2 on the first rectifier bridge arm, the third power switch tube S3 on the second rectifier bridge arm and the lower power switch tube Q2 on the first input bridge arm are turned on simultaneously in a switching cycle, and are turned off in advance before the lower power switch tube Q2 is turned off; the turn-on moments of the upper power switch tube Q1 and the lower power switch tube Q2 on the first input bridge arm are staggered by 180°.
3. The LLC symmetrical half-bridge power converter according to claim 1, characterized in that: A safety spacing of 0.01mm-1mm is arranged between different inner layers of the substrate where the secondary winding and the primary winding are located.
4. The LLC symmetrical half-bridge power converter according to claim 1, characterized in that: The first side column through hole is arranged at an edge position of the circuit board and communicates with the outside.