CLL Resonant Converter Research Articles

Multiphase BHB-CLL Resonant Converter Based on Secondary-Side VDR With Automatic Current Sharing Characteristic

A multiphase bidirectional half-bridge (BHB) CLL resonant converter with automatic current sharing characteristics is proposed in this paper for high-power bidirectional energy storage applications. The CLL converter is obtained by placing the resonant inductor in the voltage doubling rectifier (VDR). Compared with LLC resonant converter, the circulating current related to the magnetizing current of the transformer is removed from the resonant inductor. Without extra components and control schemes, the excellent current sharing performance can be achieved only by connecting two wires in the two-phase resonant tanks even when the resonant parameters have 10% tolerance. The current sharing performance of the proposed converter is analyzed by FHA method, and a 1200W experimental prototype is built to verify the superiority of the proposed converter. Under the full load condition, the measured peak efficiency in forward and backward operation mode is 97.99% and 97.8%, the output current sharing error is 0.51% and 4.0%, respectively.

A combined capacitor current balancing method with weighting factor control for multi‐string LED drivers

AbstractA multi‐string LED lamp driver is presented involving a boost converter and a multi‐output CLL resonant converter as the first and second stages, respectively. The CLL resonant converter works in a fixed resonant frequency, and output currents are controlled by the boost converter regulated by the Weighting Factor control method. Also, the boost converter improves and controls its input voltage. Since CLL resonant converters operate at fixed resonant frequency, primary‐side MOSFETs can achieve zero voltage switching, while secondary‐side rectifier diodes achieve zero current switching. A prototype of the proposed system was constructed to verify the theoretical results by practical implementation. Also, the general features of the proposed structure were compared with some other similar works. Results confirmed the accuracy and favourable performance of the proposed system. In fact, the proposed LED driver achieved good current balancing in a wide range of input voltage and unbalanced loads making the structure potentially suitable for application in solar home systems (SHS).

A digital signal processor based capacitor inductor inductor resonant converter for stand alone wind energy system using AC analysis

In this paper the CLL (capacitor inductor inductor) resonant converter (RC) with digital signal processor (DSP) based fuzzy controller for stand alone wind energy system has been estimated and the performance of the converter is analysed. The proposed converter has been analyses with the closed loop condition. The fuzzy controller regulates the output voltage with change of supply voltage and load disturbance are carried out. The controller performance of CLL RC is compared through simulation and experimental studies using TMS320F2407 processor.
 Keywords: Power electronics, DC-DC power converters, fuzzy control, wind energy system

Full-bridge resonant converter with hybrid control for wide input voltage range applications

This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility.

A Passive-Impedance-Matching Technology to Achieve Automatic Current Sharing for a Multiphase Resonant Converter

A passive-impedance-matching (PIM) technology is proposed to achieve automatic current sharing for multiphase resonant converters through matching the input impedance of each phase. The series inductors (or series capacitors) of each phase are connected in parallel to achieve a couple of virtual resistors including positive and negative resistors and variably series inductors (or capacitors). A virtual positive (or negative) resistor increases (or decreases) the input impedance of the respective phase, and the variably series inductors can also compensate the component tolerance such that the impedance of each phase is matched. The current-sharing performance of the common-inductor two-phase LLC resonant converter (as one example) is evaluated under the first-harmonic-approximation assumption. The virtual positive and negative resistors and variably virtual inductors are calculated. The proposed method can share the primary resonant current and the load current for all phases without any additional circuit and control strategy. The PIM technology is extended to other resonant converter topologies, including common-inductor or common-capacitor series-resonant converter, LCC, CLL resonant converter, etc. A 600-W 12-V common-inductor two-phase LLC resonant converter prototype is built to verify the feasibility and demonstrate advantages of PIM technology.

Asymmetrical Duty-Cycle and Phase-Shift Control of a Novel Multiport CLL Resonant Converter

In this paper, a novel multiport CLL resonant converter with a phase shift and asymmetrical duty-cycle control is analyzed. The power flow can be maintained with the phase shift between ports, whereas the asymmetric duty cycle manages the output voltage at the load terminals. Series connected transformers at the secondary side enable to split the power in each port and reduce the voltage stresses on the switches compared with the parallel connected transformers. Even under the unbalanced input conditions, the power flow between ports can be managed by the central control without any need for communication devices. In order to investigate the power distribution in each port, two different isolated dc sources and a variable load are used. The converter operation is tested at 40, 80, or 120 V inputs, with the output of 200 V at a full power of 1 kW with a maximum efficiency of 97.4%. The experimental results show that the multiport CLL resonant converter with the proposed controller is an appropriate topology for sustainable energy platforms, which are supplied by different types of energy sources, such as photovoltaic, fuel cell, wind, and so on, at various power capacities.

Analysis of a CLL Resonant Converter With Semi-Bridgeless Active Rectifier and Hybrid Control

A novel CLL resonant converter with a semi-bridgeless active rectifier (S-BAR) is analyzed, and its hybrid control strategy is proposed in this paper. This topology is developed by replacing rectifier lower diodes with synchronous switches and regulation by a phase-shifted pulsewidth-modulation signal. Theoretical and simulation results show that the performance of the proposed S-BAR is appropriate for resonant converters and secondary-side controlled infrastructure requiring a wide voltage range control at the secondary side. The hybrid control algorithm is obtained with the phase-shift and frequency tuning considering the voltage at the load terminal. High efficiency can be maintained by this proposed control, reducing conduction losses and providing zero-voltage switching soft-switching condition with a wide output voltage range. To confirm the performance of the proposed converter, experimental results are provided for which the output voltage/current range from 0 to 80 V/0 to 8.75 A with an input of 120 V and an average efficiency value of 93%.

Multichannel LED Driver With <italic>CLL</italic> Resonant Converter

This paper presents a two-stage multichannel light-emitting diode (LED) driver, which contains a buck converter as the first stage and a multichannel constant current CLL resonant converter as the second stage. The forward current of one LED string is sensed for feedback control to regulate the bus voltage, which is the input voltage of the CLL resonant converter. Meanwhile, the currents of other strings are cross regulated. In contrast, the CLL converter is always working at the series resonant frequency to maintain high efficiency. Therefore, this two-stage LED driver could achieve high efficiency over a wide load range. Furthermore, lower dimming is easy to obtain with the regulation of the first stage. Good current balance is achieved with large magnetizing inductance, even if the loads are severely unbalanced. In addition, since the transformer's turns ratio is 1:3, the charging and discharging process of the junction capacitors of secondary-side rectifiers significantly influences the similar process of the output capacitors of primary-side switches during dead time. Meanwhile, the displacement current flowing through the transformer's interwinding capacitor impacts on the current balance among multiple LED strings. With these considerations, a two-stage LED driver prototype is built to verify its good current balance and high efficiency.

Equivalence Relations of Resonant Tanks: A New Perspective for Selection and Design of Resonant Converters

There are various resonant tanks for constructing resonant converters. In this paper, the equivalence relations of resonant tanks are investigated, which bring a new perspective for analysis of resonant converters. On one hand, the equivalence relations can help select suitable resonant converter topologies for specific applications, which is illustrated by the examples of the LLC resonant converter and CLL resonant converter, and LCC resonant converter and hybrid series–parallel resonant converter (HSPRC). On the other hand, the equivalence relations can help to simplify the design of some high-order resonant converters, which is illustrated by the example of the LLC resonant converter and LLC-L resonant converter.

Analysis and Design of CLL Resonant Converter for Solar Panel-battery Systems

This paper presents a CLL resonant converter with DSP based Fuzzy Logic Controller (FLC) for solar panel to battery charging system. The mathematical model of the converters has been developed and simulated using MATLAB. The state space model of the converter is developed; it is used to analysis the steady state stability of the system. The aim of the proposed converter is to regulate and control of the output voltage from the solar panel voltage. The performance of the proposed converter is validated through experiments with a 75-Watt solar panel. The effectiveness of the controller is verified for supply change and load disturbance. The converter is implemented on a TMS320F2407 Digital Signal Processor with 75-Watt PV system. Comparison between experimental and simulations show a very good agreement and the reliability of fuzzy controller.

High-Frequency High-Efficiency $CLL$ Resonant Converters With Synchronous Rectifiers

This paper proposes a CLL resonant dc-dc converter as an option for offline applications. This topology can achieve zero-voltage switching from zero load to a full load and zero-current switching for output rectifiers and makes the implementation of a secondary rectifier easy. This paper also presents a novel methodology for designing CLL resonant converters based on efficiency and holdup time requirements. An optimal transformer structure is proposed, which uses a current-type synchronous rectifier (SR) drive scheme. An 800-kHz 250-W CLL resonant converter prototype is built to verify the proposed circuit, design method, transformer structure, and SR drive scheme.

Design optimisation of a 1 MHz half-bridge CLL resonant converter

A detailed design optimisation for the CLL resonant converter is presented and zero-voltage switching (ZVS) of MOSFETs is guaranteed in overall operation ranges. A series of analysis and calculations are presented to choose an ideal value of the loaded quality factor meeting the requirement of ZVS behaviour (inductive load and full discharge of the output capacitance of a MOSFET), ensuring the desired maximum voltage gain and optimal design with high efficiency at normal operation point. Corresponding illustrations are provided to clearly show the analysis result. The developed design optimisation method has been implemented into a 1 MHz CLL resonant converter prototype. It is designed to operate with an output voltage of 24 V and full load output power of 250 W. The maximum efficiency reaches 93% and power density reaches 32 W/inch 3 . Therefore the proposed converter is suitable for high efficiency and high power density applications such as LCD and PDP TV power module.

Half-bridge CLL resonant rectifier with quantum mode control

A quantum mode controller for the operation of the half-bridge CLL resonant converter as a high power-factor rectifier is introduced. The controller uses zero-crossing detection on the resonant current that flows through the switches to ensure operation at both resonant frequency and zero-current switching conditions. In contrast to conventional regulators, this architecture adapts itself automatically to the deviations of the power stage parameter values and is robust against wide load variations. The theoretical contributions of the paper include a control-oriented dynamic model that describes the low-frequency large-signal transient behaviour of the resonant rectifier and a systematic control design procedure based on the sliding mode control theory. Experimental tests and results validate the expected features of the quantum mode controller, such as low-harmonic content, stability and robustness.