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LLC resonant converter has the advantages of high frequency and high efficiency, and has been developed rapidly and widely used in recent years. However, due to the presence of multiple magnetic components in the circuit, the improvement of power density is limited. To solve this problem, integrated magnetic transformer is usually designed to repla...
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... then to obtain the equivalent circuit diagram, as shown in figure 9, using the principle of transformer impedance transformation. By using the gyrator-capacitor analogy method to obtain the IM gyrator-capacitor equivalent model as shown in figure 10, where C1, C2 and C3 are the equivalent permeance of the two side columns and the middle column of the magnetic core respectively; Cg1, Cg2 and Cg3 are the air gap permeance of the column on both sides of the magnetic core and the center column respectively. The equivalent model can be used to link the magnetic circuit with the electric circuit structure, which provides convenience for simulation analysis. ...
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... equivalent model can be used to link the magnetic circuit with the electric circuit structure, which provides convenience for simulation analysis. Figure 11 shows an air gap and cross-sectional area diagram of IM, where lg is the air gap length of the magnetic core (the three magnetic columns of the EE core have the same air gap to facilitate design) . A1, A2, and A3 are the cross-sectional areas of the two sides and the center columns of the magnetic core respectively. ...
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... power P=400W, transformer ratio n=8:1, switching frequency fs=350kHz, the devices used in the simulation are all ideal devices. And the simulation waveforms are as follows: Figure 12 is the steady-state simulation waveform under full load of DM, figure 13 is the steady-state simulation waveform under full load of IM transformer, and figure 14 is the steady-state simulation waveform under full load of IM. As can be seen from the above figures, in the steady state, the simulation waveforms of the voltage VAB between primary side full bridge, the secondary voltage VCD of the transformer, and the resonant inductance current iLr under the two magnetic integration methods are basically the same as DM . ...
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... power P=400W, transformer ratio n=8:1, switching frequency fs=350kHz, the devices used in the simulation are all ideal devices. And the simulation waveforms are as follows: Figure 12 is the steady-state simulation waveform under full load of DM, figure 13 is the steady-state simulation waveform under full load of IM transformer, and figure 14 is the steady-state simulation waveform under full load of IM. As can be seen from the above figures, in the steady state, the simulation waveforms of the voltage VAB between primary side full bridge, the secondary voltage VCD of the transformer, and the resonant inductance current iLr under the two magnetic integration methods are basically the same as DM . ...
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... power P=400W, transformer ratio n=8:1, switching frequency fs=350kHz, the devices used in the simulation are all ideal devices. And the simulation waveforms are as follows: Figure 12 is the steady-state simulation waveform under full load of DM, figure 13 is the steady-state simulation waveform under full load of IM transformer, and figure 14 is the steady-state simulation waveform under full load of IM. As can be seen from the above figures, in the steady state, the simulation waveforms of the voltage VAB between primary side full bridge, the secondary voltage VCD of the transformer, and the resonant inductance current iLr under the two magnetic integration methods are basically the same as DM . ...
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... IM and IM transformer has the same working effect as the DM, and they all conform to the basic characteristics of LLC resonant converter. Figure 15 shows the closed-loop load switching simulation waveforms of IM. The output voltage V0, the output current I0, the voltage VAB between primary side full bridge, the secondary voltage VCD of transformer , and the resonant inductance current iLr were measured respectively. ...
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... output voltage V0, the output current I0, the voltage VAB between primary side full bridge, the secondary voltage VCD of transformer , and the resonant inductance current iLr were measured respectively. Figure 16 shows the amplification waveforms of the simulation results of figure 15 in the range of 19.99ms to 20.035ms, and the load switched from full to half at 20ms. Figure 17 shows the amplification waveforms of the simulation results of figure 15 in the range of 34.95ms to 35.25ms, and the load switched at 35ms. Figure 18 shows the further enlarged waveforms of the simulation results of figure 17 from 34.99ms to 35.05ms. It can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. ...
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... output voltage V0, the output current I0, the voltage VAB between primary side full bridge, the secondary voltage VCD of transformer , and the resonant inductance current iLr were measured respectively. Figure 16 shows the amplification waveforms of the simulation results of figure 15 in the range of 19.99ms to 20.035ms, and the load switched from full to half at 20ms. Figure 17 shows the amplification waveforms of the simulation results of figure 15 in the range of 34.95ms to 35.25ms, and the load switched at 35ms. Figure 18 shows the further enlarged waveforms of the simulation results of figure 17 from 34.99ms to 35.05ms. It can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. ...
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... 16 shows the amplification waveforms of the simulation results of figure 15 in the range of 19.99ms to 20.035ms, and the load switched from full to half at 20ms. Figure 17 shows the amplification waveforms of the simulation results of figure 15 in the range of 34.95ms to 35.25ms, and the load switched at 35ms. Figure 18 shows the further enlarged waveforms of the simulation results of figure 17 from 34.99ms to 35.05ms. It can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. ...
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... output voltage V0, the output current I0, the voltage VAB between primary side full bridge, the secondary voltage VCD of transformer , and the resonant inductance current iLr were measured respectively. Figure 16 shows the amplification waveforms of the simulation results of figure 15 in the range of 19.99ms to 20.035ms, and the load switched from full to half at 20ms. Figure 17 shows the amplification waveforms of the simulation results of figure 15 in the range of 34.95ms to 35.25ms, and the load switched at 35ms. Figure 18 shows the further enlarged waveforms of the simulation results of figure 17 from 34.99ms to 35.05ms. It can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. ...
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... 16 shows the amplification waveforms of the simulation results of figure 15 in the range of 19.99ms to 20.035ms, and the load switched from full to half at 20ms. Figure 17 shows the amplification waveforms of the simulation results of figure 15 in the range of 34.95ms to 35.25ms, and the load switched at 35ms. Figure 18 shows the further enlarged waveforms of the simulation results of figure 17 from 34.99ms to 35.05ms. It can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. ...
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... can be seen from figure 15 that during the entire simulation time period, when the load is switched, the output voltage overshoot of IM is small, the output voltage waveform is almost unaffected, the dynamic response speed of the system is fast, and the resonant current changes with the switching of the load. In figure 16, when switched from full-load to halfload at 20ms, the output voltage overshoot is small, and it quickly returns to the rated output voltage. In figure 17 and figure 18, when the load is switched at 35ms, the output voltage overshoot is slightly larger, but it can also quickly returns to the rated value. ...
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... figure 16, when switched from full-load to halfload at 20ms, the output voltage overshoot is small, and it quickly returns to the rated output voltage. In figure 17 and figure 18, when the load is switched at 35ms, the output voltage overshoot is slightly larger, but it can also quickly returns to the rated value. In a word, whether under the static or dynamic condition, the system of IM has the smaller output current ripple and output voltage ripple, and has fast dynamic response speed. ...
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... figure 16, when switched from full-load to halfload at 20ms, the output voltage overshoot is small, and it quickly returns to the rated output voltage. In figure 17 and figure 18, when the load is switched at 35ms, the output voltage overshoot is slightly larger, but it can also quickly returns to the rated value. In a word, whether under the static or dynamic condition, the system of IM has the smaller output current ripple and output voltage ripple, and has fast dynamic response speed. ...
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... 20 is a finite element simulation of the discrete transformer, and the maximum magnetic flux destiny is about 0.29T. Figure 21 is a finite element simulation of an IM transformer with a maximum magnetic flux density about 0.27T. The maximum magnetic flux density of the above magnetic components are all less than the saturation magnetic flux density of 0.35T , and all of them meet the normal operation requirements. ...
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Citations
... The windings were sectioned and interleaved by inserting a magnetic shunt in the core, which reduced the length of the crossed sections of the windings while making the magnetic flux generated by external winding sections with cancelation performance. In addition, (Gao and Zhao, 2021), designed a magnetic integrated structure with an independent inductance LLC resonant converter. The resonant inductance and transformer were integrated into a single core using the decoupled integration method, thereby reducing the leakage inductance and lowering the losses. ...
... 02 resonant inductances and two transformers). The conventional magnetic integrated structure uses EE-type cores, where the windings of two transformers are wound on the outer columns, and the magnetic flux is unevenly distributed in the core (Gao and Zhao, 2021). The overall increase in the core volume to prevent local saturation will reduce the power density, resulting in material waste. ...
... 2) Increased leakage flux will cause a decrease in transformer efficiency; 3) Massive leakage flux can also cause serious electromagnetic interference, and secondary-side leakage inductance will cause the rectifier diode pass-state loss to increase (Gao and Zhao, 2021). ...
The LLC resonant converter used in high-power situations suffers from the problems of high conduction loss and current stress, which can be solved using input-parallel output-parallel (IPOP)-connected converter modules. However, this leads to a multiple increase in the number of magnetic components, which reduces power density. Magnetic integration technology is an effective way to reduce the volume of converters. Currently, the magnetic integrated transformer based on EE-type cores is widely used to realize miniaturization, and it uses leakage inductance instead of resonant inductance to improve power density. However, leakage inductance is difficult to control, and the external radiated magnetic field will produce serious eddy current loss and electromagnetic interference. This article proposes a novel double B-type magnetic integrated transformer, which can integrate the magnetic components of two LLC resonant converters simultaneously and where the resonant inductances are wound independently. The structure contains four low reluctance branches, which are used as the cores of the transformer and the resonant inductance. The decoupling integration method, which integrates the four components into a single core, has been used to increase core utilization and improve power density. On this basis, the transformer’s high- and low-voltage windings are cross-arranged to reduce the magnetic field intensity in space, further decreasing the loss and electromagnetic interference. Compared with the EE-type magnetic integrated transformer, the volume of the proposed structure is reduced by 5.9%. A 400W experimental prototype is built, and the results verify the validity of the design.
... The transformer is a significant component in LLC resonant converters as it provides input/output isolation, proper conversion ratio, and serves as both the series resonant and parallel inductors of the LLC resonant network. Researchers have focused on improving the operation of the transformer to reduce power losses [32][33][34][35][36][37][38][39][40][41][42][43]. For instance, a four-output transformer-controlled LLC resonant converter was proposed for Li-Ion battery charger applications in [44]. ...
The LLC resonant converter is a widely utilized power electronics converter, due to its numerous industrial and domestic applications. This converter offers some advantages such as soft-switching operation of all switches, high efficiency, high power density, low voltage stress, minimal electromagnetic interference (EMI) noise, input/output isolation, wide input/output voltage range, and reliable and good performance under the wide load variation ranges, as well as good light-load operation. However, this converter has certain limitations, which can be addressed to enhance its operation and efficiency. This paper provides an in-depth review and comparison of various LLC-based resonant converter configurations, focusing on their operational principles, mathematical analysis, control methods, and some practical applications including electric vehicle chargers, TV power supplies, LED drivers, photovoltaic cells, HVDC production, fuel cells, and wireless power transfer applications. By examining the strengths and weaknesses of the different LLC resonant converter designs, this study aims to contribute to the ongoing research efforts in improving the performance and efficiency of this important power electronics converter.
... A lot of researchers have devised various computer-aided methods based on frequency-domain analysis or time-domain analysis to optimize the resonant tank design for different applications [1]- [4]. Some research studies focused on magnetics design modification and improvement for resonant converters and using integrated planar magnetics to improve power density [5]- [7]. Some researchers worked on the extension of input and/or output voltage operation for different applications by using hybrid switching strategies, using modified resonant tanks, and topology reconfiguration [8]- [10]. ...
Synchronous rectification that is being widely used in high power and current DC-DC LLC converters to reduce conduction losses can be challenging in single-stage AC-DC LLC converters with high output voltage levels (i.e., >200V) where synchronous rectifier (SR) driving ICs cannot be used. In this paper, a simple AC line cycle synchronous rectification strategy with direct control by a cost-effective microcontroller unit (MCU) is proposed for single-stage AC-DC LLC converters with high switching frequencies using wide bandgap devices (i.e., GaN or SiC). The SR gate pulse is generated based on the time-domain calculated conduction time which is then switched ON and OFF over the AC line cycle to avoid reverse power flow in light load conditions. The proposed strategy reduces the complexity of implementation over any adaptive online calculation or model-based methods that require powerful and expensive microcontrollers. First, the operation of the single-stage LLC converter is briefly described for power factor correction (PFC) operation and then the time-domain analysis for AC operation is provided. Next, the calculation and methodology behind the proposed AC line cycle SR driving strategy are discussed in detail. A scaled-down wide bandgap-based AC-DC LLC converter prototype with a 250 V to 400 V output voltage range is used with digital control implementation to validate the performance of the proposed synchronous rectification strategy. It is found that maximum efficiency of 98.1% can be achieved for the 250 V output voltage condition which was improved by around 0.5% over the conventional fixed conduction time method. Moreover, it is shown that the proposed SR driving method obtains the same efficiency levels as more complex adaptive SR driving approaches.
... L f and C f are input filter elements and R L is the load. The magnetic integration (MI) method in [21] is employed to integrate the input filter inductor with the main inductors using a single magnetic core. It is noteworthy that due to utilizing the MI method of [21], L f is completely decoupled from other inductors. ...
... The magnetic integration (MI) method in [21] is employed to integrate the input filter inductor with the main inductors using a single magnetic core. It is noteworthy that due to utilizing the MI method of [21], L f is completely decoupled from other inductors. ...
... According to (37) and (38), and considering L k = 1µH, to achieve soft switching operation for the main and the auxiliary switches, n should be selected between 0.3 to 0.5 which in this design n = 0.4 is chosen. Magnetic integration (MI) method in [21] is applied to the proposed converter to integrate the input filter and the coupled inductors on a single magnetic core. Fig. 4 shows the magnetic structure of the proposed converter. ...
This paper proposes new fully soft switched bridgeless buck-boost power factor correction converters using single magnetic core with capability of realizing positive or negative output voltages. Full ZVS operation is provided for the main switches independent of the load and grid voltage variations. Also, the proposed converters have common ground and single ended output which increase power density and alleviates common mode noise. The proposed converters operate under discontinuous conduction mode (DCM) to shape the input current inherently. A 120W, 100kHz laboratory prototype with negative output voltage is implemented to verify the theoretical analysis and the effectiveness of the proposed topologies. The results demonstrate efficiency of 96.2% and total harmonic distortion (THD) of 4% at full load condition.
... The only drawback is fixed frequency and voltage gain of the output side [32]. Integrated magnetic winding design decreases the magnetizing current with the cancellation of leakage flux [33]. However, the reluctance estimation of WPT system could be sophisticated. ...
... The amplitude of magnetic field density dominates in the ferrite core when compared with the operation frequency. (32,33) illustrate the calculation method and the advantage of the increasing modulation frequency characteristics which keep within the linear range. ̂m , ̂ and ̂ are the circuit maximum magnetizing current, transmitter coil current and magnetic field density in ferrite respectively. ...
An inductor-aid step-up LLC wireless power transfer (WPT) system is proposed in this paper. It could step up the WPT output voltage beyond the conventional LLC series-series (SS) compensation method. Employing a parallel inductor with the transmitter coil to lessen the circuit impedance thus the inverter exhibits a new gain curve. The constant frequency operation and simple control of two series active switches in the parallel inductor branch shows a practical improvement of conventional constant frequency LLC WPT system, in terms of voltage demand, new standards and applications. Even the frequency modulation LLC WPT system could be benefited from this enhanced topology rather than to deteriorate the inverter current stress and unnecessary over-rating of magnetic components. The receiver side compensation tank has no additional voltage drop and overcurrent. A 300W prototype has been constructed to validate the concept and performed at 90% efficiency.
... [19] created a larger resonant inductance by using a magnetic shunt integrated into planar windings, which can increase the power density of the high-frequency LLC resonant converter. [20] shown a magnetic integrated LLC resonant converter with independent inductance winding, and its resonant inductance and magnetizing inductance are decoupling integrated. [21] explored the magnetic-thermal coupling analysis of the integrated magnetic RRF converter, and the results showed that the integrated RRF converter has almost the same power efficiency as the conventional discrete configuration. ...
Hybrid distribution transformer (HDT) has powerful controllability for system currents and voltages. To reduce the number of discrete magnetics and make highly efficient use of ferromagnetic materials, a novel structure of HDT with magnetic integration (IMHDT) is proposed in this article. The key features of this IMHDT are inserting the leakage magnetic iron cores and sharing the common magnetic branches, by these, all the discrete magnetics of HDT are integrated. The 3-D finite element analysis(FEA) model, the equivalent electric-magnetic circuit model and the control strategies for this IMHDT are further established. Simulation and experiment results verify that the proposed IMHDT can not only save ferromagnetic materials but also inherit all the controllability of HDT.
... The ferrite legs were hereby beneficially placed in a square pattern to reduce the flux density inside the core in the top and bottom plate. In [19][20][21], a three-leg transformer was used, where the turn-ratios were chosen to achieve the desired inductance values. Similarly in [22,23] a the ferrite leg number was reduced to two by employing "8-shaped" windings. ...
... Recently, several pieces of research have been carried out on the design ofresonant parameters, control methods and strategies, DC gain analysis, soft switching realization conditions for electrical vehicles, battery systems, communication systems OLED technology [10][11][12][13]. ...
The LLC resonant converter has high-efficiency and low switching losses by achieving Zero Voltage Switching (ZVS). Therefore, it has been widely used in the industry. In conventional vehicles, the low voltage systems are fed by the 12V battery. However, several appliances such as the heater, air-conditioning compressor operate at a few kilowatt regions. Thus, the amount of the current drawn by these appliances is relatively higher with the conventional 12V system. To compensate this high current, a 48V level is obtained from the high-voltage batteries via a dc-to-dc converter. In this study, 3kW Half-Bridge LLC resonant converter is designed for high voltage battery to low voltage battery used in electric vehicles by using PSIM. 48V output voltage is regulated with 0.17% by the proposed converter in several cases, which are varied input voltage and loads by changing switching frequency owing to control algorithm. In terms of unit step response, rising and settling times are 5.55 ms and 1.06 ms, respectively.
... However, since the high magnetic coupling of a planar transformer makes leakage inductance too small to be used as a resonant inductor in the LRC, an extra inductor must be employed and it considerably decreases the power density. To overcome this problem, several types of integrated magnetics transformers have been proposed to integrate an external inductor into a transformer [12][13][14][15][16][17]. In [12], the resonant inductor is integrated with the transformer in a single magnetic core using the decoupling integration method. ...
... To overcome this problem, several types of integrated magnetics transformers have been proposed to integrate an external inductor into a transformer [12][13][14][15][16][17]. In [12], the resonant inductor is integrated with the transformer in a single magnetic core using the decoupling integration method. However, this method requires additional windings for the resonant inductor except for the main transformer, which may significantly increase the size and volume of the integrated magnetics. ...
Recent studies on compact and lightweight electronic devices have demonstrated that the LLC resonant converter (LRC) can facilitate achieving high efficiency and high power density. Moreover, employing a planar transformer can further improve the overall system power density. Although the planar transformer can assist in reducing the size of the converter, its high magnetic coupling makes the leakage inductance too small for a resonant inductor in the LRC. Therefore, an extra inductor must be employed separately, leading a considerable decrease in the power density. From this reason, significant research on integrated magnetics has been conducted to combine a transformer and external inductor into a single core. However, they require additional wires or magnetic sheets, and their structures are complex and costly. To overcome these limitations, the integrated magnetics planar transformer (IMPT) for a high power density LRC is proposed in this paper. In the proposed approach, since the primary wire is split into each side leg of the EE-type magnetic core and each operates as a transformer and a resonant inductor alternatively, an external inductor or additional wires are unnecessary. In addition, since the magnetic flux density of the IMPT is approximately equivalent to that of conventional transformer, the core size and the number of turns are almost the same. Therefore, the proposed IMPT features higher efficiency and power density without additional size and costs. To confirm the validity of the proposed IMPT, the operational principles, theoretical analysis, design considerations, and experimental results from a 350 W prototype are presented.
... For better magnetic integration, their leakage inductance is often used in the resonant inductance of the resonant cavity. 17,18 To get a high power density, the operating frequency is set to be high, and the output current is usually large; these factors all cause high losses. Therefore, the optimization of the PT, especially for high frequency operation, is necessary for the improvement of the converter efficiency. ...
An accurate power loss model, for the design of high-efficiency switching power supplies, is difficult to establish due to the complicated magnetic components where the power loss is hard to calculate. This paper proposed a multi-level power loss model of LLC circuits with a planar transformer of high frequency, high power, and low voltage output. The key loss items can be optimized by using this loss model, the accuracy of which and the feasibility of the optimization method are validated by extensive prototype experiments. The experimental results show that the average accuracy of the loss calculation is about 93.6%, and the high efficiency at high-power conversion (95.9% @ 3 kW, 224–16 V) has been realized using an optimized prototype converter.
