Resonant-tank control of parallel resonant converter

A control method called resonant-tank control (RTC) is proposed for a parallel resonant converter operating above resonance. Using a simple linear combination of tank variables, it has potential for high-frequency DC-DC converter applications. RTC controls the tank in a near-time-optimal manner and is shown to have better dynamics than conventional frequency control. Experimental results that confirm the superior transient performance of the RTC method are provided. The principle of operation of the RTC can be extended to operation below resonance as well as to series resonant converter control     

High-frequency high-order parallel resonant converter

A novel approach to the analysis of design of a high-order high-frequency LCC-type capacitive coupled parallel resonant converter (PRC-LCC) operated in the continuous-conduction mode is presented. The presence of an additional capacitor in series with the inductance of the conventional PRC results in a converter with more desirable control characteristics. It is shown that, at switching frequencies lower than the resonant frequency, the gain of the LCC-type converter is lower than the grain of the conventional PRC. This facilitates the converter design with a lower turn-ratio transformer and therefore allows for a higher operating frequency. The complete state-plane diagram of the LCC-type converter, from which a set of steady-state characteristic curves is plotted, is given. Various design curves for component value selections and device ratings are given. A design example with computer simulation results is presented     

Soft switching resonant converter with duty-cycle control in DC micro-grid system

Resonant converter has been widely used for the benefits of low switching losses and high circuit efficiency. However, the wide frequency variation is the main drawback of resonant converter. This paper studies a new modular resonant converter with duty-cycle control to overcome this problem and realise the advantages of low switching losses, no reverse recovery current loss, balance input split voltages and constant frequency operation for medium voltage direct currentgrid or system network. Series full-bridge (FB) converters are used in the studied circuit in order to reduce the voltage stresses and power rating on power semiconductors. Flying capacitor is used between two FB converters to balance input split voltages. Two circuit modules are paralleled on the secondary side to lessen the current rating of rectifier diodes and the size of magnetic components. The resonant tank is operated at inductive load circuit to help power switches to be turned on at zero voltage with wide load range. The pulse-width modulation scheme is used to regulate output voltage. Experimental verifications are provided to show the performance of the proposed circuit.     

A new phase-controlled parallel resonant converter

A phase-controlled resonant converter was obtained by connecting in parallel the AC loads of two identical parallel resonant inverters. A phase shift between the drive signals of the two inverters controls the amplitude of the output voltage of the new inverter. A voltage-driven rectifier is used as an AC load of the inverter, which results in a phase-controlled parallel resonant DC-DC converter. A frequency-domain analysis is performed for the steady-state operation of the inverter, and two types of voltage-driven rectifiers and design equations are derived. The converter can be operated at a constant switching frequency, which reduces EMI problems. It is found that for switching frequencies higher than the resonant frequency by a factor of 1.07, the load of each switching leg is inductive. The converter is capable of regulating the output voltage in the range of load resistance from full-load to no-load. Experimental results are presented for a prototype of the phase-controlled parallel resonant converter with a center-taped rectifier tested at an output power of 50 W and a switching frequency of 116 kHz     

A parallel resonant converter with postregulators

A parallel resonant power converter (PRC) with postregulator(s) power synchronized to the primary switching frequency is investigated for discontinuous-conduction mode operation. It is analyzed with a magnetic amplifier, which blocks the rising edge of the secondary voltage, and with a synchronized buck regulator, which blocks part of the trailing edge of the secondary voltage waveform under the steady-state conditions. As a result, it has been shown that magnetic amplifiers are not suitable for resonant mode power converters, since the step change of the load from low to high during the same switching period as the primary makes the operating conditions worse. However, postregulators that block the trailing edge of the secondary voltage waveform do not adversely affect the operating conditions of PRC and work satisfactorily. As an alternative, a PRC with a magnetic postregulator is presented. An offline 150 W 250 kHz PRC is designed with a magnetic postregulator for a personal computer application, and experimental waveforms are included     

Half-cycle control of the parallel resonant converter operated as ahigh power factor rectifier

A half-cycle control technique for the parallel resonant power converter operated as a high power factor rectifier is introduced in this paper. Switching of the bridge power transistors is determined such that the bridge input current averaged over a half switching cycle exactly follows the reference proportional to the input voltage. Zero current switching and below-resonance operation are guaranteed, while control of the input current is the fastest possible, regardless of the operating point. In contrast to conventional regulators, the performance is preserved under both small and large signal variations, and also for large variations of the power-stage parameter values. Fast response, stability and robustness are experimentally verified on a 1.4 kW prototype     

Single-stage current-fed DC-DC converter with time-sharing controlof output voltage and input current

A single-stage current-fed DC/DC power converter structure and control strategy for simultaneous control of output voltage and current flowing in the input inductor are described. This configuration is suitable for high power-density applications because it results in reduced converter size and power loss. A very fast control-to-output response is obtained, together with stable operation even for large load and reference variations. Static and dynamic converter performances are investigated and design criteria given. Experimental results obtained on a prototype are also reported     

Steady-state analysis and design of the parallel resonant converter

Five basic operating modes of the parallel resonant converter are analyzed. Three of the modes occur when the output filter inductor is removed and the remaining two occur when the filter inductor is large. Closed-form solutions are found for the two most important modes. Analysis results are given graphically so that the designer can use them without lengthy calculation or computer iteration. Switching frequency, peak tank capacitor voltage, and peak tank inductor current are plotted in the output plane. These plots, with a load line superimposed, show how operating point, frequency, and peak stress vary as load conditions change. Use of the output plane plots to minimize component costs is explained. Comparison of the best designs found for the large and zero filter inductance cases shows that removing the filter inductor can reduce both parts count and tank circuit size while peak transistor current remains unchanged     

Steady-state analysis of the parallel resonant converter withLLCC-type commutation network

A novel converter topology known as LLCC-type parallel resonant converter (PRC-LLCC), in which the tank circuit consists of two inductors and two capacitors, is introduced. Using the state-plane approach, the steady-state analysis of the PRC-LLCC operating in the continuous conduction model is carried out. It is shown that by using the state variable transformation technique the steady-state response of the converter can be represented by two state-plane diagrams. Using these diagrams and the circuit equations, a set of control characteristic curves which are useful for converter design is derived. Based on these curves, a design procedure along with a specific design example is given. The correctness of the analysis results is verified via computer simulations     

Nonresonant and resonant coupled zero voltage switching converters

Two zero-voltage switching power converters with nonresonant and resonant coupling are presented. These are high-order multiple resonant converters in which the circuit modes associated with the converter operation may have different resonant frequencies. The steady-state responses of these converters are derived in terms of state-plane diagrams by using proper state variable transformations. It is shown that the converters have all the desirable features for high-frequency applications and overcome the drawback of load-range limitation of zero-voltage switching associated with the conventional class-E converter     

Analysis of a hybrid series parallel resonant bridge converter

The steady-state operation of a hybrid series parallel resonant bridge is analyzed. Two expressions are derived for the power output as a function of capacitor ratio, switching frequency, and conversion ratio. One power output expression is for conversion ratios less than or equal to one, and the other expression is for conversion ratios greater or equal to one and less than or equal to two. The optimum conversion ratio for maximum power transfer is also derived     

Analysis and design of a half-bridge parallel resonant converter

A half-bridge parallel resonant converter (PRC) is analyzed in detail for both continuous-conduction-mode and discontinuous-conduction-mode operations to provide more straightforward and easy-to-use design tools. Closed-form solutions are derived for the PRC operating under steady-state conditions. Theoretical results obtained are presented in the form of normalized design graphs. They could be directly utilized in designing a half-bridge PRC, having up to 2:1 input voltage variation. They do not necessitate converting the obtained ratings, depending on the input voltage and load variations, to check the worst case values. A design example of a 500 kHz 150 W offline switching power supply is given for both modes of operation, and it is implemented for experimental verification.<>     

Operation of the LCC-type parallel resonant converter as a lowharmonic rectifier

A single-phase high-frequency transformer isolated single-stage AC-to-DC controlled rectifier with low line current harmonic distortion using a variable-frequency controlled LCC-type (or series-parallel) resonant power converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line current harmonic distortion and high power factor operation. The converter performance characteristics have been verified with SPICE3 simulations (without active control) and experimental prototype SPRC (rated at 150 W, with and without active control) for variation in load as well as line voltage. When operated with active current shaping, this converter operates in zero-voltage-switching mode for the complete range, maintaining power factor close to unity with low line current distortion and low peak current compared to the parallel resonant converter     

New zero voltage switching DC converter with flying capacitors

A new soft switching converter is presented for medium power applications. Two full-bridge converters are connected in series at high voltage side in order to limit the voltage stress of power switches at V_in/2. Therefore, power metal–oxide–semiconductor field-effect transistors (MOSFETs) with 600 V voltage rating can be adopted for 1200 V input voltage applications. In order to balance two input split capacitor voltages in every switching cycle, two flying capacitors are connected on the AC side of two full-bridge converters. Phase-shift pulse-width modulation (PS-PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active MOSFETs can be turned on under zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. Two full-bridge converters are used in the proposed circuit to share load current and reduce the current stress of passive and active components. The circuit analysis and design example of the prototype circuit are provided in detail and the performance of the proposed converter is verified by the experiments.     

Integral cycle mode control of the series resonant converter

A control method for the series resonant converter (SRC) in which the device switching instants are always synchronized to the zero-crossing points of the resonant current is proposed. Output voltage is controlled by proper selection of the switch modes by varying the duty ratio of the powering mode and free resonant mode. Each switch mode is analyzed and the DC transfer function is obtained. It is also shown that the simulation results coincide well with the practical case. The SRC using the proposed control scheme shows many advantages, such as low current-switching stress, low switching loss, low electromagnetic interference, high input power factor, and wide control range. Some of these characteristics are verified experimentally     

Interleaved soft switching resonant converter with a small input ripple current

ABSTRACT

An interleaved frequency control soft switching converter is studied for solar power or fuel cell power applications. The proposed circuit topology contains two parallel current-fed circuit cells with interleaved pulse-width modulation operation. Thus, the ripple currents at input and output terminals are decreased. In each circuit cell, the proposed current-fed dc-dc converter includes boost circuit and resonant circuit to achieve current ripple-free on low voltage side and less switching losses on active devices. The boost circuit and the resonant circuit have same active devices to decrease power switches. Due to the resonant behaviour, the reverse recovery current loss on secondary diodes is removed. The voltage doubler circuit topology is accomplished on secondary-side to reduce diode counts and conduction loss. The performance and effectiveness of the developed interleaved PWM current-fed converter are verified and confirmed by experiments.     

An energy feedback control of series resonant converter

An energy feedback control utilizing the resonant tank circuit energy as an inner feedback loop is proposed to improve the stability and dynamic characteristics of the series resonant converter (SRC). The energy-feedback-controlled SRC is modeled and analyzed in discrete time domain. In this analysis, the eigenvalues of the controlled system are dependent on the energy feedback gain ratio, and the design guidelines which can be used to select this ratio are derived. Experimental results show a good agreement with theoretical analysis     

三阶高频并联谐振变换器的相平面分析和设计

本文用相平面分析法分析和设计了一种电容耦合的并联谐振变换器。引入附加电容与传统的并联谐振变换器中的电感相串联,能获得更好的调节功能。本文利用平面轨迹图,给出了选择电路元件参数的设计依据。     

Robust controller design for a parallel resonant converter usingμ-synthesis

DC-to-DC resonant power converters have been the subject of much attention recently. These power converters have the potential to provide high-performance conversion without some of the problems associated with classical pulse-width modulation (PWM)-based converters, thus allowing for smaller, lighter power supplies. However, in order to achieve this, a suitable control circuit, capable of maintaining the desired output voltage under different operating conditions, is required. In the past, small-signal models obtained around the nominal operating points were used to design controllers that attempted to keep the output voltage constant in the presence of input perturbations. However, these controllers did not take into account either load or components variations, and thus could lead to instability in the face of component or load changes. Moreover, the prediction of the frequency range for stability was done a posteriori, either experimentally or by a trial-and-error approach. In this paper, the authors use μ-synthesis to design a robust controller for a conventional parallel resonant power converter. In addition to guaranteeing stability for a wide range of load conditions, the proposed controller rejects disturbances at the power converter input while keeping the control input and the settling time within values compatible with a practical implementation. These results are validated by means of detailed nonlinear circuit simulations obtained using PSpice     

基于MAX120的峰值电压检测及其与CPLD的接口

介绍了一种性能良好的A／D转换器MAX120，详细阐述了基于MAX120的数字式峰值电压检测器，并示出了其逻辑功能的Verjlog—HDL描述和与CPLD的接口电路，最后给出了在窄脉冲测试源作用下的实测结果。